ATOLL RESEARCH BULLETIN NO. 495 ATOLL BIODIVERSITY SURVEYS AND CONSERVATION E POTENTIAL OF INNER SEYCHELLES ISLANDS Edited by MICHAEL J. HILL BULLETIN NATIONAL MUSEUM OF NATURAL HISTORY SMITHSONIAN INSTITUTION WASHINGTON, D.C. U.S.A. JULY 2002 Issued by ATOLL RESEARCH BULLETIN NO. 495 BIODIVERSITY SURVEYS AND CONSERVATION POTENTIAL OF INNER SEYCHELLES ISLANDS EDITED BY MICHAEL J. HILL Deu 17 awe WOKARIED OO ISSUED BY NATIONAL MUSEUM OF NATURAL HISTORY SMITHSONIAN INSTITUTION WASHINGTON, D.C. U.S.A. JULY 2002 ll ACKNOWLEDGMENT The Atoll Research Bulletin is issued by the Smithsonian Institution to provide an outlet for information on the biota of tropical islands and reefs and on the environment that supports the biota. The Bulletin is supported by the National Museum of Natural History and is produced by the Smithsonian Press. This issue was financed by Nature Seychelles(formerly BirdLife Seychelles)and distributed with funds from Atoll Research Bulletin readers and authors. The Bulletin was founded in 1951 and the first 117 numbers were issued by the Pacific Science Board, National Academy of Sciences, with financial support from the Office of Naval Research. Its pages were devoted largely to reports resulting from the Pacific Science Board's Coral Atoll Program. All statements made in papers published in the Atoll Research Bulletin are the sole responsibility of the authors and do not necessarily represent the views of the Smithsonian nor of the editors of the Bulletin. Articles submitted for publication in the Atoll Research Bulletin should be original papers in a format similar to that found in recent issues of the Bulletin. First drafts of manuscripts should be typewritten double spaced and can be sent to any of the editors. After the manuscript has been reviewed and accepted, the author will be provided with a page format with which to prepare a single-spaced camera-ready copy of the manuscript. COORDINATING EDITOR Ian G. Macintyre Smithsonian Institution PO Box 37012 ASSISTANTS National Museum of Natural History MRC-125 William T. Boykins, Jr. Washington, DC 20013-7012 Kay Clark-Bourne Kasandra D. Brockington EDITORIAL BOARD Stephen D. Cairns (MRC-163) Smithsonian Institution Brian F. Kensley (MRC-163) PO Box 37012 Mark M. Littler (MRC-166) National Museum of Natural History Wayne N. Mathis (MRC-169) (Insert appropriate MRC code) Jeffrey T. Williams (MRC-159) Washington, DC 20013-7012 Joshua I. Tracey, Jr. (MRC-137) Warren L. Wagner (MRC-166) Roger B. Clapp Smithsonian Institution PO Box 37012 National Biological Survey MRC-111 Washington, DC 20013-7012 David R. Stoddart Department of Geography 501 Earth Sciences Building University of California Berkeley, CA 94720 Bernard M. Salvat Ecole Pratique des Hautes Etudes Lab de Biologie Marine et Malacologie Université de Perpignan 66025 Perpignan Cedex, France PUBLICATIONS MANAGER A. Alan Burchell Smithsonian Institution Press ATOLL RESEARCH BULLETIN NO. 495 PAGES BRIE A © eee a TSR Ose Meu ate nenanucem siete te aechiciaemanantiag’ Michael J. Hill Vv INTRODUCTION AND METHODG.......................0044 Michael J. Hill, Terence M. Vel 1 Kathryn J. Holm and Nirmal J. Shah 153 020 D para cee cone npeetnes socom don Haden eeencuenae tera auneoueeacmapnasctan: Michael J. Hill, Terence M. Vel, 11 Kathryn J. Holm, Steven J. Parr and Nirmal J. Shah CONCEPTION eee oreo a ones : Michael J. Hill, Terence M. Vel, 31 Kathryn J. Holm, Steven J. Parr and Nirmal J. Shah CO TLGIASS I fetaet pte ome a ea A em rr i PE a HS Michael J. Hill, Terence M. Vel, 49 Kathryn J. Holm, Steven J. Parr and Nirmal J. Shah (CON 2D BOSS Opes sas oreiecesa Ses tconcaaseecncnedhoc aeREnr arate sac saaneciarceeneeenec Michael J. Hill, Terence M. Vel, 73 Steven J. Parr and Nirmal J. Shah IDI] BINT ISS enauseuebasssasannes a teennance poh aeReSoccsaneclice cOnenELr TU SREAa SR Hao ERER Ban Michael J. Hill, Terence M. Vel, Kathryn J. Holm, Steven J. Parr and Nirmal J.Shah 97 IGA TInt eer re rate eR Pec clea Michael J. Hill, David R. Currie, Terence M. Vel and Rodney Fanchette 119 GRANDE SOB UR iscitssccecce sere soho ace amece suteeeeteseouettncenaes Michael J. Hill, Terence M. Vel, Steven J. Parr and Nirmal J.Shah = 141 IVPANIRUTPANININ Bieter ores ciiz ese acne aeiaa mse won ae Tan eau an seettgtuuseeenes Michael J. Hill, Pat Matyot, Terence M. Vel, Steven J. Parr and Nirmal J.Shah = 157 TKO) RR1 BY 8 Gea aati sane aair aaa Utama Hatta are as BI AS ern Michael J. Hill, Terence M. Vel, Kathryn J. Holm, Steven J. Parr and Nirmal J.Shah =177 SIVENBARUES SEG este setae tan A. scoot nena aan ure Cena Michael J. Hill, Terence M. Vel, Kathryn J. Holm, Steven J. Parr and Nirmal J.Shah 201 SPIDERS (ARANEAE) COLLECTED 1999-2000 «0.0.0.0... cece Michael I. Saaristo, Michael J. Hill 221 ASSESSING CONSERVATION VALUE OF ISLANDS IINGREIESINNERGSE Y.G HIE TGIGES eee ee oticoosettaeient ten icnsd teste ene onset area nonns Michael J. Hill 231 153 Bl RY) 82 GNI C) OAS se psacocepeooondecdacibeeodoeacane tocachdoscaaseeactacdace cacuseearet aecatocec acess scuagdoccoscea cL 255 1) LVANTET BtS) saenceneocbaddonocosdanphecbeGunoeclocacnoae oS ToTE DEC ECHR RITE DDR At coouoReecace eee eee ec Sete 269 ISSUED BY NATIONAL MUSEUM OF NATURAL HISTORY SMITHSONIAN INSTITUTION WASHINGTON, D.C. U.S.A. JULY 2002 lil 1V Aerial views of islands in the inner Seychelles: Upper: Granitic islands; Cousin and Cousine. Lower: Bird, a coralline island on the edge of the Seychelles Bank. Photos © Seychelles Tourism Marketing Authority. PREFACE The Republic of Seychelles is made up of 115 islands spread over an Exclusive Economic Zone (EEZ) of 1,374,000 kim? (99.97% of which is sea) in the western Indian Ocean. The islands fall into three main groups, each with a different geological character: the central or inner islands (actually the northernmost group), most of which are predominantly granitic; the low-lying sand cays of the Amirantes and Farquhar to the South; and the raised limestone islands of the Aldabra group (Aldabra and Cosmoledo atolls, Astove and Assumption) and St Pierre. Aldabra is closer to Madagascar (450 km away) than it is to the granitic islands (Mahé is around 1,150 km away). The inner islands and Aldabra atoll support a fauna and flora rich in endemic forms (because of the distance between the groups, few endemics are shared). Both sites have been recognised as ‘Endemic Bird Areas’ by BirdLife International. Aldabra atoll (which makes up approximately a third of the land area of the Seychelles) is a World Heritage Site, with a tiny human population employed by the Seychelles Island Foundation in the conservation of the site. Because of the remote and relatively inhospitable nature of the atoll, it has never been permanently settled and exploitation has been less intensive than in the other island groups of the nation. In contrast, the inner Seychelles islands were settled in 1770 and now support around 80,000 people (on a total land area of 232 km’). In the past 230 years the inner islands have seen extensive habitat change with the conversion of coastal forests to coconut plantation and loss of mangroves and hill forests for timber, fuel, and the production of cinnamon. Although vertebrate extinctions appear to have been minimal when compared to other remote archipelagos, eight bird species of the granitic islands are today listed as globally threatened. Plantation agriculture in the Seychelles has through much of its history been only marginally profitable, primarily due to poor transport links with markets and the small scale of production. In the late twentieth century, falling world copra prices led to the abandonment of many plantations and the largest sectors of the economy today are fish processing for export and the tourist trade. In Seychelles, the low-volume, high-value tourist market is based on the apparently unspoilt environment of the islands and there is undoubtedly potential for ecotourism, already developed on islands such as Cousin and Bird. Ecotourism may in turn provide opportunities for increasing thé amount of land devoted to conservation in Seychelles through active management of tourist islands, although it should not be seen as a panacea; on small islands, even low-volume tourism can have significant environmental impacts, and very few tourists actually make the long journey to Seychelles to observe the endemic wildlife. Economic changes in Seychelles have coincided with a period of increased concern for the environment and flagship species in particular; today, further human- induced extinctions of Seychelles endemic vertebrates seem unlikely. The Seychelles Magpie Robin Recovery Programme initiated by Nature Seychelles in 1990 is a good example of long-term commitment that has led to a major increase in population and range of this endangered bird. However, the intense pressure of development and stochastic events, such as the introduction of novel alien species, are real threats to habitats and endemic species in Seychelles. V1 The work described in this volume was carried out as part of the project ‘Management of Avian Ecosystems in Seychelles’, funded by the Global Environment Fund through the World Bank and implemented by Nature Seychelles. The aim of the island assessment programme was to survey a range of medium-sized islands in the inner Seychelles in order to assess their current biodiversity value and potential to support endangered endemic vertebrates, particularly birds. The standardised survey methods were carried out on 10 islands (of 40 in the island group), making this the most extensive such survey in the Seychelles since the early twentieth century when expeditions in 1905 (the Percy Sladen expedition) and 1908 (led by J. Stanley Gardiner) contributed greatly to the understanding of the flora and fauna of Seychelles (although the objectives of these expeditions were largely taxonomic). The collection of papers in this volume presents the results of the island assessments. The first chapter gives a summary of the methods used and provides further background to the project. In the following chapters, each island is treated in turn, with data on the biodiversity of each island, in addition to its historical and geographical context, and conservation recommendations to enhance its biodiversity value. In a final summary chapter, the potential importance of each to conservation of Seychelles endemic vertebrates is discussed. Michael J Hill Nature Seychelles (formerly BirdLife Seychelles) May 2002 Vil ACKNOWLEDGEMENTS The island assessment work described in this volume was carried out as part of the World Bank-Global Environment Facility (GEF)-funded project, Management of Avian Ecosystems in Seychelles, coordinated by Nature Seychelles. We would like to thank the owners and managers of all islands visited for their permission for the work, and in many cases active assistance in the fieldwork. In particular: Bird Island Lodge, Serge Robert (Bird Island); Marine Parks Authority Seychelles, Kevin Hoareau (Curieuse Island); Denis Island Development Company and Mason’s Travel (Denis Island); North Island Ltd., Richard Slater-Jones and Mark Coetzee (North Island). The Marine Parks Authority of Seychelles provided transport to Conception, Curieuse, and Thérése. Fieldwork was carried out by a team of four to six people, and on each island the core team of three was joined by several workers, most from the Seychelles Ministry of Environment and Transport, the Ministry of Culture or Nature Seychelles. These included: Pierre-André Adam, Eugene Annacoura, Majella Athanase, Terence Athanase, Allain Camille, Perley Constance, Laura Davis, Marcel Dufréne, Joseph Francois, Barbara Hoareau, Camille Hoareau, Marline Isodore, Terry Jules, Victorin Laboudallon, Allan Marguerite, Charles Morel, Roland Nolin, George Ravinia, Dr Gerard Rocamora, Andy Roucou, Roland Tambarra, Jose Tirant, Terence Valentine, and Roy Youpa. The work described in this volume would have been impossible without the assistance of these field workers. We would also like to thank those at Nature Seychelles who provided invaluable logistic support, including Dave Currie, Kerstin Henri and James Millett. The National Archives and Museums (Ministry of Culture and Information, Seychelles), provided historical records, the National Meteorological Services (Ministry of Environment and Transport, Seychelles) gave access to unpublished weather data, and the Geographical Information Systems (GIS) section of the Ministry of Land Use and Habitat provided recent aerial photographs of the islands. Maps for these reports were prepared by Rishabh Jivan. Specimens collected in the course of fieldwork were identified by John Noyes of the Natural History Museum, London (wasps), Michael Saaristo of the Zoological Museum, University of Turku (spiders), Pat Matyot (beetles, Orthoptera, phasmids) and Gillian Watson of Commonwealth Agriculture Bureau (CABI: soft bugs). A number of people contributed to the development of island assessment methods and assisted with the preparation of these reports, including Clive Hambler (Oxford University), Don Merton (Department of Conservation, New Zealand), James Millett and Steve Parr (Nature Seychelles). The authors would also like to thank David Stoddart, Ian Macintyre, Roger Clapp, Wayne Mathis and George Zug for comments on the manuscript. . ‘Seychelles Islands North (.) Silhouette Conceptione Thérése Figure 1. The central Seychelles. Cousin Aride, Curieuse (oa S95 ° PRASLIN —La Dighe Frégate , INTRODUCTION AND METHODS BY MICHAEL J. HILL’, TERENCE M. VEL', KATHRYN J. HOLM’, and NIRMAL J. SHAH! ABSTRACT The central Seychelles islands support 12 species of endemic land birds, eight of which are regarded as globally threatened. As part of a project to evaluate the islands’ potential to support translocated populations of endemic birds, biological surveys were carried out on 10 of the islands ranging from 28 to 286 ha in size. This paper describes the background of the project and the aims and methods of the island assessment survey, the results of which are presented by island in later chapters. INTRODUCTION The central Seychelles (Fig. 1) comprises a group of around 40 granitic islands (and two outlying coralline islands) situated approximately 1,600 km from East Africa and 1,700 km from India (Stoddart, 1984). The flora and fauna are derived from the Oriental and African regions but show a high degree of endemicity: Scott (1933) estimated that 51% of the insect fauna were endemic. There are about 76 extant endemic plant species (Carlstrém, 1996a), which comprise around 9% of the total flora (Procter, 1984). The islands also support a number of endemic land birds (12 extant taxa: see Table 1), and have been classified as an Endemic Bird Area (EBA), one of 218 such regions of global importance for their endemic bird species (Stattersfield et al., 1998). In common with most oceanic archipelagos, the granitic Seychelles has no native terrestrial mammals, the only non-marine mammals being two endemic species of bat (Racey and Nicoll, 1984). Since human settlement of the islands in 1770, habitat destruction and the introduction of alien animals and plants have lead to the complete extinction of at least three endemic bird taxa and the loss of many island populations (Diamond, 1984). On smaller islands, habitat destruction accelerated in the nineteenth and early twentieth centuries with the expansion of coconut plantations. Many islands became devoted to the production of coconut together with a few other cash crop species. A few smaller or remote granitic islands remained predator-free despite conversion to plantation agriculture, and these islands offered refugia for endangered endemic avian species lost on other islands. As a result, species such as the Seychelles warbler Acrocephalus ' Nature Seychelles, PO Box 1310, Victoria, Mahé, Seychelles. Email: birdlite@seychelles.net 2 9 4 . ana ~ ; ~ “1991 Casa Marcia Crescent Victoria, British Colombia, Canada. 2 sechellensis, Seychelles fody Foudia sechellarum, and Seychelles magpie-robin Copsychus sechellarum are today found on a few small islands. These three species, together with five other endemic birds, are regarded as globally threatened (Stattersfield et al., 1998). Several of these species have, at some stage, been reduced to single island populations (the Seychelles warbler on Cousin, magpie-robin on Frégate, black paradise flycatcher on La Digue, and scops owl on Mahé). Such small, isolated populations are vulnerable to extinction through stochastic events (Simberloff, 1998), especially when island refugia are small. In such cases, translocation to establish new populations is an important conservation tool. Table 1. Endemic land bird taxa of the granitic Seychelles. Scientific name English name Pop. Estimate No. of Status” individuals)! __ islands Coracopsis nigra barklyi black parrot 200-300 2 - Copsychus sechellarum Seychelles magpie-robin 85 4 Critical Terpsiphone corvina Seychelles black paradise 150-200 2 Critical flycatcher Otus insularis Seychelles scops owl 180-360 ] Critical Zosterops modestus Seychelles white-eye 280-380 3¢ Critical Falco araea Seychelles kestrel c. 900 7 Vulnerable Collocalia elaphra Seychelles swiftlet 2,500 — 3,000 3 Vulnerable Acrocephalus sechellensis | Seychelles warbler 2,100 3 Vulnerable Foudia sechellarum Seychelles fod 3,260 3 Vulnerable Alectroenas pulcherrima Seychelles blue pigeon > 3,000 pairs 14+ Least Concern Hypsipetes crassirostris Seychelles bulbul > 7,000 pairs 5) Least Concern Nectarinia dussumieri Seychelles sunbird > 8,000 pairs 15+ Least Concern ' Population estimates for seven endangered endemics from species action plans (Shah and Nevill, 2002), Seychelles white-eye and black parrot from Skerrett ef a/. (2001); other species from Rocamora (pers. comm.). Estimates for “Least Concern” species are pairs, all other species individuals. * Only islands in the central Seychelles considered: Seychelles fody is also present (as naturalised population) on one outer coralline island. > Global conservation status from BirdLife International (2000). * Seychelles white-eye recently (2001) introduced to Frégate Island, previously restricted to Mahé and Conception (Rocamora ef al. in press). Recent economic changes and developments in the field of wildlife management have allowed an improvement in the status of several species of Seychelles endemic birds. In the late twentieth century, many plantations became uneconomic and were no longer maintained. Two small islands (Cousin and Aride) were purchased and dedicated entirely to conservation. Cats had previously been present on Aride but were eliminated in the 1920s or 30s (Warman and Todd, 1984); Cousin had no alien mammals apart from the black-necked hare Lepus nigricollis introduced in the early twentieth century (Racey and Nicoll, 1984). Inter-island transfers of some of the most endangered bird species have led to encouraging results. Following the eradication of cats on Cousine and habitat restoration on Cousine and Aride, the Seychelles warbler has successfully been established on both islands (from Cousin: Komdeur ef a/., 1995) and the Seychelles magpie-robin has been successfully translocated to Cousin and Cousine (from Frégate: Parr et al., 2000). In recent years both rats and cats have been eradicated on several islands, including Bird Island (black rats eradicated 1996: Feare, 1999a), Frégate (Norway rats eradicated 2000) and Denis and Curieuse (cats eradicated 2000/2001). The eradication of alien predators and regeneration of broadleaf woodland and scrub in former coconut plantations should facilitate the translocation of endangered endemic bird species to new islands and the establishment of further populations. It was with this opportunity in mind that the project Management of Avian Ecosystems in Seychelles was designed, and implemented from 1999. As part of this project an island assessment process was carried out, which involved biological surveys of a selected range of islands in the central Seychelles from 29 ha (Cousin) to 286 ha (Curieuse). The primary aim of the survey was to assess the potential of a number of islands for habitat restoration and the translocation of endangered endemic land birds, in particular five globally threatened species known to survive on relatively small islands: the Seychelles magpie-robin, Seychelles white-eye, Seychelles black paradise flycatcher, Seychelles warbler and Seychelles fody. For most islands surveyed, assessment visits were carried out in both major seasons, the drier southeast (SE: usually between June and August or September) and the wet northwest monsoon period (NW: approximately November to April). This allowed seasonal differences in (for example) invertebrate activity and freshwater wetlands to be taken into account. This volume is based on the assessment of biological factors on each of the islands visited, describing each island in turn and including a summary chapter on the comparative values of each island for conservation. ISLAND SELECTION Not all of the 40 granitic islands could be visited in this survey: effort was directed at a smaller number of islands. The initial selection was made on the basis of island size, human population, and land ownership. All the central Seychelles islands are relatively small and within the group, both the smallest and largest were identified as having particular disadvantages. The smallest islands (under 20 ha) were rejected because (in most cases) they would only support small populations of endemic land birds, leaving populations vulnerable to stochastic extinctions. Of 43 named islands, 22 are under 20 ha (and 20 of these under 10 ha). Large islands (over 500 ha), while they support a high diversity of habitats and have great conservation potential, also have a number of disadvantages: most have large human populations with associated introduced animal species, and multiple ownership which complicates management. The only large island under single ownership (of four islands > 500 ha) is Silhouette (1,995 ha). Using size criteria, a list of 18 islands was produced. Of these, several inaccessible islands were not visited, and others (for example, islands in the Ste Anne Marine Park off Mahe with restricted access or multiple ownership) were also excluded from the survey. A total of 10 islands were included in the final study and a further island (Frégate) was also the subject of a short assessment visit. For each of the 10 islands studied, a short report is included in this volume. METHODS The islands listed in Table 2 were each visited at least once during the survey period. While temperature and humidity vary little through the year, rainfall is seasonal in the central Seychelles islands: dry months between about May and October are dominated by the SE trade winds. The rainy season (NW monsoon) lasts from November to April (Walsh, 1984). Variations in rainfall (especially, the water stress of the driest months) are likely to have a profound effect on invertebrates (McCulloch and Norris, 1997) and plants in particular. Thus, two sampling periods were carried out, the first predominantly in the dry SE season and the second in the NW monsoon. Most islands were visited twice, once in each season. Table 2. Islands studied and dates of survey. (Island names generally follow map DOS 604: Seychelles, produced by the UK Directorate of Overseas Surveys in 1983, with the exception of fle aux Vaches, now generally known as Bird Island, and Ile du Nord, North Island). Island Geology Survey time Survey dates (ha) (days) SE season NW season Curieuse 285 Granitic 23 2/8 - 14/8/99 5/1 - 18/1/00 Félicité 268 Granitic 6 8/11 - 14/11/99 - North 210 Granitic 17 19/8 - 29/8/99 24/1 - 3/2/00 Denis 143 Sand cay 7 3/10 - 13/10/99 4/4 - 13/4/00 Bird 101 Sand cay 6 - 21/3 - 27/3/00 Marianne 95 Granitic 16 18/10 - 28/10/99 6/3 - 14/3/00 Grande Soeur 84 Granitic 9 17/7 - 27/7/99 - Thérése 74 Granitic 15 6/9 - 15/9/99 7/2 - 15/2/00 Conception 60 Granitic 15 22/9 - 28/9/99 21/2 - 28/2/00 Cousin Granitic 14/6 - 25/6/99 1/12 - 8/12/99 For each island, vegetation and physical maps were produced using data from a variety of sources. Physical data came from existing physical maps (prepared by the UK Directorate of Overseas Surveys and the Seychelles Government; Series Y851[DOS 204]). Vegetation maps were prepared using field observations and data from recent (1998) colour aerial photographs of the islands (provided by the Ministry of Land Use and Habitat, Seychelles Government, for all islands except Thérése). Vegetation maps were based on a simple classification of habitats according to topography (whether on coastal lowland or “‘plateaw’, or granite hill >10 m above sea level) and the dominant plant forms and species. Major habitats included beach crest scrub (native), coconut plantations, plateau woodland (native or exotic), hill woodland (native or exotic), hill scrub (native or exotic) and vegetation of open, rocky places (locally known as “‘glacis’’). Inhabited islands often had significant areas of open grassland and gardens. Of these habitats, those of greatest importance to Seychelles endemic birds are woodland and scrub; many of the endemic species are particularly associated with woodland while anthropogenic habitats are more heavily utilised by introduced bird species. In order to measure island quality for endemic birds, further sampling of vegetation and invertebrate numbers was carried out concentrated in woodland and scrub areas. Using the vegetation map for each island, random point locations were found within woodland/scrub habitats (15-20 points on each island visit). At each point, vegetation and invertebrate survey techniques were applied within a 10 m x 10 m plot. Vegetation Survey A number of measures were recorded to provide details of the structural and biological diversity of vegetation within each 10 m x 10 m plot. Only flowering plants and ferns were recorded; algae, lichens and mosses were excluded. Vegetation was recorded in three strata: canopy (woody plants and palms over 5m tall), shrub (woody plants and palms less than 5 m tall), and herb layers (herbaceous plants and seedlings under 0.5 m tall). In the canopy layer all individual plants were identified and height and DBH (Diameter at Breast Height: 1.3 m above ground) recorded. In the shrub and herb layers, all species present were recorded, and the percentage cover of each within the layer estimated. In addition, for the herb layer the percentage of the 10 m x 10 m plot with no vegetation was estimated. A measure of the quantity of dead wood (tree stumps, standing and fallen dead wood) was made for each plot. Invertebrate Survey Within each plot the following measures of invertebrate abundance were carried out: pitfall trapping, leaf insect counts, beating and sweeping. In a subset of plots, Malaise trapping was used. Pitfall traps were made of plastic cups with a diameter of 7 cm at the mouth. Traps were set about 2 m apart on a diagonal line across the plot and each trap was given a ‘lid’ of wire mesh (approx. mesh gauge 1.5 cm) to exclude land hermit crabs. Ethylene glycol was used as a preservative. Traps were in place for three nights, after which the invertebrate catch was preserved in 70% ethanol. Invertebrates were later counted and sorted to species or morphospecies. Leaf-insect counts were developed as a measure of food supply for the insectivorous Seychelles warbler which mainly feeds by gleaning from the underside of leaves (Komdeur, 1994). Counts were made at, or around, each plot for each of the four most abundant tree species at the plot. For each tree species, five trees were selected. On each of the five trees invertebrates were counted on the underside of 10 leaves. Invertebrates were classified to order, suborder or family. In addition, two leaves were removed from each tree sampled in order to estimate the mean leaf size for each tree species. Leaf sizes were used to calculate the density of invertebrates per square metre of leaf. Since insect activity varies with time of day, temperature etc., counts were completed between 8 a. m. and 11 a. m. No invertebrate specimens were collected. Beating and sweep-sampling were used to collect invertebrate specimens on abundant tree species and in herbaceous vegetation within the plot. Methods were standardised to ensure that sampling effort was standardised between plots and islands (see Hill, 2001). Flight-intercept (Malaise) traps were used to collect flying invertebrates. Ethanol (70%) was used as a preservative in trap heads and the traps left in place for three nights. All invertebrate specimens collected were stored in 70% ethanol and sorted to family or (for pitfall catches) morphospecies. Specimens were retained by Nature Seychelles with the exception of spiders (Araneae) and wasps (Hymenoptera). Spiders were sent for identification by Dr Michael Saaristo of the Zoological Museum, University of Turku, Finland, and remain in the collection of the museum; wasps for identification by Dr. John Noyes of the Natural History Museum, London. Other Survey Methods In addition to the vegetation and invertebrate survey methods carried out within plots, a number of further measures were made at the island level. Freshwater habitats occurred on many of the islands surveyed. These habitats have importance as they support a number of Seychelles endemic species including invertebrates and amphibians (Stevenson ef al., 1987), and have been implicated in the survival of the endemic black paradise flycatcher on La Digue (Watson, 1981). Wherever freshwater marsh, ponds or streams occurred they were surveyed physically and biologically. In most cases, the area of marsh was calculated, vegetation was sampled on a transect across the water body and aquatic invertebrates sampled using a hand net and, in some cases, a submerged aquatic light trap run overnight. A complete list of plant species observed was compiled for each island. Species lists were compiled by one observer (MJH), mainly from sight records. Identifications were made using Beaver (1995), Friedmann (1994), Procter (1974), Robertson (1989), and Wise (1998). Species that could not be identified in the field (particularly grasses and sedges) were collected, and many of these were identified by comparison with specimens in the Seychelles National Herbarium (Natural History Museum, Victoria). Pressed specimens from the project are now held by Nature Seychelles. Plant species lists are included in each island account, where the taxonomy follows Robertson (1989) for monocotyledons, and Friedmann (1994) for dicotyledons. The tree Ochrosia oppositifolia (Lam.) Schum. should more properly be referred to as Neisosperma oppositifolia (Lam.) Fosberg & Sachet (D. Stoddart, pers. comm..), but the name Ochrosia (used in Fraidmann, 1994) is used here for purposes of uniformity. Observation and opportunistic collection were used to identify members of certain invertebrate groups, including day-flying Lepidoptera (identified from Larsen, 1996), Odonata (identified using Blackman and Pinhey, 1967), and Phasmatoptera (identified using a key provided by P. Matyot). Vertebrates were identified by observation; no vertebrates were collected, with the exception of rats. For identification of bird species, Penny (1974) and Sinclair and Langrand (1998) were used, although taxonomic order in species lists follows that in Skerrett et a/. (2001). Introduced predators are of prime importance in determining the current restricted distribution of several endangered endemic birds in Seychelles. While the Seychelles has a relatively small number of introduced bird and mammal species, several introduced species are known or presumed to negatively affect native land birds. These include two Rattus species (R. rattus and R. norvegicus), domestic (feral) cat Felis catus, barn owl Tyto alba and common mynah Acridotheres tristis On each island, lists of all bird and mammal species observed were compiled and, in addition, tape playback methods were 7 used to confirm the presence of barn owls and trapping was used to identify rat species present. Lists of all birds and mammals observed were compiled. Tape playback used recordings of barn owls from India and Britain played between 7 p.m. and 9 p.m. in at least three locations on each island. Recordings were played for a total of 20 minutes in each location. Rodent trapping followed “index trapping” methods developed in New Zealand by the Ecology Division of the Department of Scientific and Industrial Research (Cunningham and Moors, 1983; Nelson and Clark, 1973). The methodology used differed in some respects from index trapping; live rat traps were used rather than snap traps (to reduce the inadvertent killing of land crabs, birds, etc.) and numbers of trap-nights were rather lower than the recommended minimum of 150 for each habitat type. The traps were in place for five nights with coconut flesh as bait. The trapline consisted of pairs of traps (with 1m between the pair) at 30 m intervals. Two traplines were laid on each island to sample major habitats represented. On each morning of trapping the number of rats trapped was recorded, together with other animals caught and the number of traps that had closed without trapping anything. These data were used to calculate an index of rats trapped per 100 trap-nights, corrected for traps closed (D. Merton, in Jitt.). Tape playback was also used to give presence/absence data for three endemic bird species: Seychelles scops owl, Seychelles black paradise flycatcher and Seychelles white- eye. All three of these species may respond to taped calls of their own species by moving closer to the source of the calls and (sometimes) calling, although responses differ between the species and with time of year. Scops owls usually call in response to the tape and fly to perches close to the player, where they can be observed by torchlight (D. Currie, pers. comm.). Paradise flycatchers do not usually sing back to taped song but both males and females move close to taped sources. They tend to gather quickly but disperse again rapidly, at least when constant-loop tapes are used (D. Currie, pers. comm.). White- eyes sometimes respond to taped sources but may ignore them altogether (G. Rocamora pers. comm.). Tape playback was carried out at sample points on walked transects (for example, existing paths). For all species, 60-second constant-loop cassettes were used. Location of playback sites and duration of playback differed, depending on target species: e For scops owl, transects were located within hill forest habitat, or on the plateau adjacent to areas of hill forest. Tapes were played for 20 minutes at three points on each transect, at least 200 m apart. Playback was between 7 p. m. and 9 p. m. e For the paradise flycatcher and white-eye, transects were located in all major habitats represented on an island. Tapes were played at five points on each transect, at least 100 m apart, for five minutes at each point. Playback occurred between 5.30 a.m. and 6.30 a.m. (Rocamora, 1997). For each species, as many sampling events (mornings/evenings of playback) as possible were carried out. The date, time, habitat, and any responses were recorded. RESULTS Results are presented here by island, each of the following 10 reports giving the data gathered on each island and a final summary report discussing the implications of these island studies for the conservation of Seychelles native flora and fauna, and endemic birds in particular. Species lists for each island are given in the text of each island report (most taxa) or as an Appendix (in the case of plants). References are given at the end of the volume. 9 : 7 < ih - it co. i “The sie ol Asim rial 4 : i Bot ed an ‘' - _" } - 7 7 i dri Tee Te at yi! ; Matt} ; . a i ‘ i i} is 4! 1} Oe ¥. oy) hy j . 1A 4 H Thies cH OF hy q i \iod os vas ’ Lee ri 7 La, _' ~ © ti ‘cl eigen and uopoes int? (CC Wilt Boon ¥ ad Roi (i Te MoOrTiy O1 thee: jalan vic ee ihe § Eiyhe aay ’ a" - > , VE ah ' ft it Wie sa) “jn ij he al a, ia i bap. via * mi ‘se i e The Exarni Period Vite bo et cs: a {Pee : | i, Oke Vit ure! ivy ieee g ae ititt VAlPili Ue sco i a | ui { mt § delivxct ts ic te Coe allie Dreomx Lelnidl amnion iru iy rite SE ah hc elidel 1 sichalag en i i ae ~ AMuad ti ihe-graniiia gro as Pies, aiyericcitnaboty Gy) Rani te in 80 ee ee et saree clitveryghce. bog itld binted ri Lares i83), La natal cals teh patie Om Fit EE tert Ossi ey ia x. ) : iti pas ciatmag during the Nw (Honan perid (heres, tic mimics al Tate Macias pri Betruary’\, Pr w Binth udu, febrialidliia are yt: ; . Stadilur, inca ee (Fear, Tees}, ta.bosh ( 44 ; a , when > im a desire » Approximate area of Sooty Tern colony Legend &X] Vegetation plots = Building su: Beach —— | 200 metres Figure 1. Bird Island: Physical map, with position of tern colony and location of vegetation plots. BIRD BY MICHAEL J. HILL!, TERENCE M. VEL!, KATHRYN J. HOLM’, STEVEN J. PARR? and NIRMAL J. SHAH! GEOLOGY, TOPOGRAPHY AND CLIMATE Bird is the northernmost island of the Seychelles, lying around 90 km north of Mahé, the largest of the granitic Seychelles, at the northern edge of the Seychelles bank. Different published sources vary in the estimated area of Bird Island with figures of c. 70 ha given by Feare (1979), 82 ha in Stoddart and Fosberg (1981), 101 ha in Skerrett et al. (2001), and 120.7 ha from recent aerial photographs (Ministry of Land Use and Habitat, Seychelles, unpublished data). In part, this variation may be explained by seasonal or longer-term variations in the vegetated area of the island; Bird Island is relatively dynamic, experiencing considerable coastal changes over time (Feare, 1979). The maximum elevation is less than 4 m above sea level. Unlike the majority of islands on the Seychelles Bank, Bird has no exposed granite and it is entirely formed of reef-derived sands. The accumulation of guano on sand deposits has led to the formation of phosphatic sandstone over 26% of the island’s surface (Baker, 1963). Phosphatic sandstone is concentrated in a central band; the island’s coastal zone 1s entirely sandy. Most of the original guano has now been removed for export. The soils of Bird Island are of two main series; over the central phosphatic sandstone area, Jemo series soils (missing their upper layer of guano) occur. In the rest of the island, soils of the Shioya series occur (Piggott, 1969). The beaches of Bird Island undergo considerable seasonal change. An annual cycle of erosion and deposition occurs with erosion of western beaches and deposition of a sand spit at the north of the island during the south east trade season. During the north west monsoon the sand spit is eroded and deposited on beaches on the west and north east coasts. The extent of erosion varies between years (Feare, 1979). Compared to the granitic islands to the south, Bird Island is relatively remote. The nearest island is the coralline Denis Island approximately 50 km to the west. The nearest large island in the granitic group is Praslin, approximately 80 km to the south and east. The Seychelles islands experience a seasonal humid tropical climate (Walsh, 1984). The annual rainfall pattern on Bird follows that of the granitic islands, with most rainfall occurring during the NW monsoon period (between the months of September/October and February). For Bird Island, rainfall data are only available for 1961, 1962 (Stoddart, 1971) and part of 1972 (Feare, 1979). In both 1961 and 1962, total ' BirdLife Seychelles, PO Box 1310, Mahé, Seychelles. Email: birdlife @sevchelles.net 21991 Casa Marcia Crescent Victoria, British Colombia, Canada. : Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, UK. 12 annual rainfall on Bird Island was lower than on Denis Island and lower than that on the high islands of the granitic Seychelles. HISTORY In 1771, the island was explored and charted by the cruiser Eagle (Stoddart and Fosberg, 1981). The earliest detailed scientific records were made on the visit of H. M.S. Alert in 1882 (Coppinger, 1885). At that time, the island had a coastal band of shrubby vegetation (probably Scaevola sericea, Suriana maritima and Tournefourtia argentea) surrounding a central area dominated by herbaceous species. There were no land birds but abundant seabirds, including sooty terns Sterna fuscata. The human population consisted of only two people. This situation changed soon after the visit of the Alert, with the extraction of guano deposits in 1895-1906 followed by the planting of coconuts. At first, the plantation was restricted to a narrow central strip of the island (Fryer, 1910) but, by the 1970s, coconut woodland dominated the island’s vegetation (Feare, 1979: Stoddart and Fosberg, 1981). The sooty tern colony, which in 1908 occupied most of the island’s area, was restricted to the north west part of the island and considerably reduced in size. In 1967, some of the coconuts around the colony of sooty terns were felled to allow the colony to expand (Feare, 1979). In 1971-73, two airstrips were cleared and a small tourist lodge constructed (Feare, 1979). Tourism became the main source of income for the island although coconuts were still collected for export and sooty tern eggs collected for local consumption. Today the coconut plantation on Bird is no longer managed for production and the island is managed as a resort with 26 villas. The small permanent population of the island is employed in the hotel and tourists travel to Bird by small plane from Mahé. Sooty tern eggs are no longer routinely collected for export to the main islands of the Seychelles (although eggs were collected in 1999; Feare, 1999b). The flora, fauna and ecology of Bird Island were the subject of two recent detailed studies (Feare, 1979; Stoddart and Fosberg, 1981). The sooty tern colony has been the subject of ongoing monitoring since 1993 (Feare and Gill, 1993-7; Feare, 1998, 1999): FLORA AND VEGETATION Flora A total of 105 plant species were recorded on Bird Island (Appendix 1), including one fern, one gymnosperm (introduced) and 103 angiosperms. Of these, 35 ornamental or edible species (all introduced) were restricted to garden areas and did not occur in natural habitats. In all, 71 (68.9%) of angiosperm species observed are regarded as introduced (or probably introduced) in Seychelles (Friedmann, 1994; Robertson, 1989) and 22 (21.4%) native. The remaining 10 (9.7%) were of unknown status. No species endemic to Seychelles were recorded. 13 Forty species recorded by earlier visitors were not observed; 21 of these (52.5%) introduced (Appendix 1). At least one of these species (Pemphis acidula) probably never occurred (Stoddart and Fosberg, 1981), and other records may have arisen out of confusion between Bird and Denis Islands; both Acrostichum aureum and Typha javanica are species of standing water (fresh or brackish) and both still occur on Denis Island. Some species are almost certainly extinct, including former crop plants (such as Nicotiana tabacum) and introduced trees that were planted in small numbers (e.g. Ficus benghalensis). Some crop plants in particular are probably occasionally cultivated, although not present at the time of the survey. Several native plants (especially grasses and small herbs such as Sida parvifolia) are probably still present but overlooked on the current short survey. If synonyms (four species), species that were never present (three species) and extinct plants (12 species) are excluded, the maximum number of plant Species that may survive on Bird Island is 124. Compared to the flora of the granitic islands, that of Bird is notable for its low species richness, lack of endemic species and the dominance of introduced plants (of the total Seychelles flora, around 54% is introduced and 9% endemic; Procter, 1984). Of the introduced plants established on Bird Island, only two can be regarded as invasive weedy species (Carlstrém, 1996a; Fleischmann, 1997): Carica papaya and Passiflora Suberosa Both are widely distributed across the island. In addition to these alien species, the coconut Cocos nucifera, although probably native to the Seychelles, is present in extremely high numbers to the exclusion of other plants. Vegetation The extent of major vegetation types on Bird Island is shown in Table 1, and Figure 2, estimated using the figure of 120.7 ha as the total island size. In total, 20 vegetation plots were completed covering 2.000 m’ or 0.17% of the island’s surface. The plots were located randomly within habitats excluding grassland and garden; the survey covered 0.25% of the targeted area. A summary of results is shown in Table 2. The vegetation of Bird Island had a relatively low density of trees, and the tree layer was species-poor. A total of only five tree species were recorded, four of which were probably native to Seychelles (although at least one of these, Ochrosia oppositifolia, may have been introduced to Bird Island). The most abundant species in the tree layer was Cocos nucifera; 26 of 84 trees (31.0%) were C. nucifera. Other abundant species were Carica papaya (22 trees, 26.2%) and Pisonia grandis (19 trees, 22.6%). Casuarina equisetifolia was relatively abundant in coastal vegetation but none were recorded within vegetation plots. The shrub layer was generally dense. The lowest percentage cover in this layer (5%) was recorded in plot K8, which had a complete canopy of Pisonia. Other plots had a more mixed tree layer or more broken canopy and had a higher density of shrubs. The most widespread species of the shrub layer were Carica papaya (in 17 of 20 plots, with mean cover of 13.2% in plots where it occurred), Cocos nucifera (in 15 plots, with mean cover of 22.9% in plots where it occurred), and Phyllanthus pervilleanus (in 13 plots, with a mean cover of 7.1%). In the herb layer, the most widespread species was again Carica papaya (in 14 of 20 plots with mean cover 4.1%). Three other species occurred in 10 or more plots: 14 Passiflora suberosa (in 11 plots, mean cover 2.3%), Cocos nucifera (in 10 plots, mean cover 2.1%), and Nephrolepis sp. (in 10 plots, mean cover 43.6%). Compared to most other islands studied, Nephrolepis showed a rather restricted distribution but was abundant where it did occur. Only one individual of Pisonia was recorded in the herb layer. Legend: vegetation types Beach crest shrubs, mainly Scaevola Beach crest trees, Cordia and Thespesia ee Coconut plantation Coconut/pisonia woodland Ea Casuarina Other trees [-_]Grassland, garden — = | 200 metres Figure 2. Bird Island vegetation. 15 Table 1. Extent of major vegetation types, Bird Island. Approx. area (ha) Vegetation type Coconut plantation with scrub 13 11 “Native” woodland (Cocos + Pisonia) 18 (15) Beach crest vegetation (Scaevola, beach crest trees) 50 4] Grassland/garden (includes Sooty Tern colony and 3) 33 airstrip)) TOTAL Table 2. Vegetation plot summary, Bird Island. Habitat Plots Mean Mean Meanshrub Meanherb Openleaf Bare Dead wood altitude _—_ trees layer cover layer cover litter rock _— (pieces per (masl) ha’! (%) (%) cover (%) _(%) plot) Woodland 20 <5 420 54.2 44.1 39.8 14.1 2 /scrub Compared to that of the other coralline island studied (Denis Island), the vegetation of Bird Island is species-poor and has low diversity. A large proportion of the island is made up of open habitats; the sooty tern colony has a mat of herbaceous vegetation consisting of Portulaca oleracea, Boerhavia repens, Tribulus cistoides and Phyla nodiflora together with grasses (Feare, 1979). The airstrip and areas around the lodge are dominated by grasses including Eleusine indica, Eragrostis spp. Cynodon dactylon and Dactyloctenium ?aegyptium, and herbs including Phyla nodiflora and Boerhavia repens. Coastal (beach crest) scrub was recorded by early visitors (Fryer, 1910). The current inland woodland and scrub have developed since the early twentieth century when coconuts and papaya were first planted (Fryer, 1910). Since 1976, the native Pisonia has become an important part of this vegetation type; only one tree was recorded in 1976 (Stoddart and Fosberg, 1981), but at the time of the survey there were several hundred individuals. The increase in Pisonia coverage has reduced dominance by coconut. However, this trend has recently reversed; many Pisonia trees were showing loss of foliage or dieback, apparently because of the effects of soft bugs (Hemiptera: Sternorrhyncha) cultured on the trees by crazy ants Anoplolepis gracilipes (see below). Pisonia and papaya were both largely restricted to the central (phosphatic sandstone) area of the island. INVERTEBRATES Pitfall trapping Pitfall trap assemblages on Bird Island were the largest from any of the island surveyed in the project (see Table 3). They also showed the highest degree of dominance by a single species, in this case the introduced crazy ant. The mean number of crazy ants 16 per plot was 4,890; three plots had less than 50 ants in five pitfall traps (plots G9, C4 and T12) and these are classified as “ant-free” plots in Figure 3. Assemblages on Bird Island were much larger than those on the granitic islands and on the coralline Denis Island, even if ants are excluded (Table 3). Ants appear to have an influence on the taxonomic composition of the pitfall assemblages. While assemblages on Denis and Bird ant-free plots were dominated by crustaceans, ant- infested plots on Bird were mainly composed of one species of orthopteran, Myrmecophilus sp., which is closely associated with ants. Earwigs (Dermaptera) were completely absent in ant-infested plots on Bird Island but cockroaches (Blattodea) were relatively abundant. Species richness was lower in Bird ant-infested plots (mean 8.0 species plot’) than in ant-free plots (9.3 species plot’'). Table 3. Pitfall assemblages from Bird Island, and other islands in the same season. NI = number of individuals over 2 mm body length. Mean NI plot’! Mean NI - ants Bird 4947..3 Sei Denis (NW season) 137..9 327i Granitic islands (NW season) 61.1 16.0 | ™ Coleoptera _@Dermaptera | M Orthoptera | NBlattodea | OCrustacea | ®Araneae | O Mollusca | M@ others Bird Bird Crazy ant-free plots Crazy ant-infested plots n=3 n=17 Figure 3. Composition of pitfall assemblages on Bird and Denis Islands, excluding ants. “Others” includes Annelida, Myriapoda, Thysanura, Lepidoptera, Diptera and insect larvae. Leaf-invertebrate Counts Leaf-invertebrate counts were carried out for six tree and shrub species, four in both crazy ant-infested and ant-free areas (see Table 4). Invertebrate densities were highest in ant-infested areas and especially on Pisonia grandis. Most of the invertebrates on trees in ant-infested areas were soft bugs (especially the coccid scale Pulvinaria urbicola), and crazy ants. Crazy ants encourage scale insects and feed on the honeydew they secrete. They also feed on other invertebrates, needing protein-rich food for their 17 larvae (Haines et al., 1994); this could explain the low densities of other invertebrates encountered on Phyllanthus and Scaevola. On Pisonia, huge colonies of scale insects were tended by crazy ants and the density of other invertebrates was higher than in ant- free areas. Many of these other invertebrates were of species predatory on soft bugs (including ladybirds Coleoptera: Coccinellidae, lacewings Neuroptera) that apparently avoided heavy predation by ants. Table 4. Density of invertebrates on foliage, Bird Island. n= no. of leaves counted; NI = number of individual invertebrates. Ant-free areas mean NI mean NI m~ leaf! NI mm? Exc. ants Ant-infested areas Mean NI mean NI NI m~ leaf’ m” Exc. ants + bugs N Introduced species Carica papaya 550 16.51 209.31 AMe3}s) Native species Ochrosia 100 0.01 0.60 0 oppositifolia Phyllanthus S21 300 3.62 6866.72 12.71 pervilleanus Pisonia grandis Scaevola sericea Terminalia catappa 400 514.89 34439.19 308.01 150 aI 86.71 0 50 1.54 34.04 0 250 ASD, NAS) OS 16.56 2023 Malaise Trapping Malaise traps were situated in four locations, all of which were infested with crazy ants. Catches were very large, mean 2,477.25 individuals; however, most individuals were wingless crazy ants which walked into the trap from surrounding vegetation and the ground. Anoplolepis dominated Malaise assemblages from three of the locations, forming 69.8 — 89.5% of the total assemblage. At one location (plot M7), crazy ants were only 6.5% of the complete assemblage. This location also had the highest absolute numbers of other invertebrates, and the largest number of taxonomic groups present (14). The composition of Malaise assemblages is shown in Figure 4. The majority of taxa collected have yet to be identified to species level. 18 Number of Individuals 200° Wasps O)Lepidoptera | O Hemiptera Diptera M Psocoptera 4 Collembola @ other inverts Figure 4. Taxonomic composition of Malaise trap assemblages (excluding ants). Observation A list of invertebrate species observed or collected in the current survey, and by previous observers, is given in Table 5. Table 5. Invertebrates, Bird Island. Order Family Species Notes Mollusca Achatinidae Achatina ?fulica (Bowditch, 1822) African land snail Streptaxidae ?Ennea sp. Occasional in pitfall traps Arachnida: Acarinae Argasidae Ornithodoros capensis Neumann, Recorded on sooty terns 1973 1901* (Feare 1976) Ixodidae Amblyomma loculosum Neumann, Recorded on sooty terns 1907* (Hoogstraal et al. 1976) Aranae Tetragnathidae Nephila inaurita (Walckenaer, 1841) | Abundant, March 2001 Scorpiones Buthidae ?Isometrus maculatus (De Geer, Recorded by Feare (1979) 1778)* under the bark of Casuarina Crustacea: Amphipoda Talitridae Sp. Indet. In pitfall traps, ant-free locations only Decapoda Ocypodidae Ocypode ceratopthalmus (Pallas, Ghost crab, beaches. Rare kV) Ocypode cordimana Desmarest, 1825 Ghost crab, beach crest. Rare Insecta: Coleoptera Carabidae Tetragonoderus bilunatus Klug, 1832 Rare in pitfall traps Coccinellidae Sp. Indet. On foliage Paussidae Sp. Indet. Abundant in pitfall traps Scarabaeidae Oryctes monoceros (Olivier, 1789) Larvae in pitfall traps Protaetia maculata (Fabricius, 1775) © Abundant Hemiptera Coccidae Pulvinaria urbicola Cockerell, 1893 = Abundant on Pisonia Hymenoptera Anthophoridae Xylocopa caffra (Linnaeus, 1767) Occasional Formicidae Anoplolepis gracilipes (Smith, 1857) | Abundant Cardiocondyla emeryi Forel, 1881 Rare in pitfall traps 19 Order Family Species Notes Tapinoma melanocephala (Fabricius, Rare in pitfall traps 1793) ?Technomyrmex albipes (F. Smith, Rare in pitfall traps 1861) Tetramorium bicarinatum (Nylander, Rare in pitfall traps 1846) Vespidae Polistes olivaceus (de Geer, 1773) Occasional Lepidoptera Lycaenidae ?Zizeeria knysna (Trimen, 1862) Common Lepidoptera Nymphalidae Hypolimnas misippus (Linnaeus, Common, March 2001 1764) Odonata Sp. Indet. * Dragonflies recorded by Feare (1979) Orthoptera Myrmecophilidae = Myrmecophilus sp. Abundant, pitfall assemblages Phthiraptera Saemundssonia sternae (L., 1758)* Recorded by Feare (1979) on Roseate tern * species recorded by previous observers, not seen in current survey. Discussion: Invertebrates The crazy ant dominates invertebrate assemblages on Bird Island. This species has ill-defined multi-queen colonies that multiply chiefly by budding. They feed on honeydew from Hemiptera but also require protein-rich foods and have been observed taking ants and other insects, isopods, myriapods, molluscs and arachnids (Haines et al., 1994) and land crabs (Feare, 1999a). It is significant that pitfall assemblages in ant- infested areas of Bird Island had no myriapods, Dermaptera, or molluscs and were relatively species-poor. A small number of invertebrate species seems to be able to survive in ant-infested areas and reach far higher densities than in ant-free areas. Some of the invertebrates recorded in crazy ant-infested areas feed on the bugs (including ladybirds Coleoptera: Coccinellidae) and others on the ants themselves (e.g. ant beetles Coleoptera: Paussidae). On Bird Island the tree Pisonia grandis was favoured by crazy ants. The major Sternorrhynchine bug encouraged by the ants was the introduced coccid Pulvinaria urbicola. This species 1s widespread in the Caribbean, Asia and Pacific regions, but has not been recorded in Seychelles before (Gillian Watson, pers. comm.). It usually feeds on members of the Solanaceae and was probably introduced to Bird Island with agricultural produce. Exudates from the bug encourage sooty moulds to grow on leaves and heavy infestations of the insects can lead to plant death, as observed in Pisonia on Bird Island. Some invertebrate species common on other islands in the central Seychelles appeared rare on Bird Island, possibly due to the effects of crazy ants. For example, the social wasp Polistes olivaceus was rarely seen and no nest was found. Although solitary carpenter bees Xylocopa sp. appeared abundant, nests were concentrated in an area of Scaevola in the south east of the island yet to be colonised by ants. Land crabs were also comparatively rare (crazy ants have been observed killing crabs: Feare, 1999a). Feare (1979) recorded the presence of dragonflies (species not given), but as there is usually no standing water on the island they could only breed there in wet years. None were recorded in the current survey. 20 VERTEBRATES Reptiles Five reptile species were observed on Bird: three lizards and two land tortoises. At least two of these species (the land tortoises Geochelone gigantea and G. pardalis) were introduced on Bird Island. The Seychelles skink Mabuya sechellensis may also be introduced. It was not recorded by Fryer in 1908 (Fryer, 1910) and the first record of the species on Bird Island was that of Vesey-Fitzgerald (1947). The geckos (Hemidactylus frenatus and Phelsuma sp.) may have arrived by natural means. All of the lizard species appeared to be restricted to parts of the island free of crazy ants. A further introduced reptile species, the blind snake Rhamphotyphlops braminus (previously recorded by Feare, 1979 and 1998) was not observed, but it is likely that this secretive species survives on the island, at least in areas free of crazy ants. Giant tortoises were present in 1787 (presumably belonging to one of the endemic species of the granitic islands) but this population became extinct before 1875 (Bour, 1984). In addition to the land reptiles, two marine turtles breed on the beaches of Bird Island; Hawksbill Eretmochelys imbricata and green sea turtle Chelonia mydas (Frazier, 1984). Crazy ants have been observed to kill turtle hatchlings (Feare, 1999b). Birds Because of Bird Island’s marginal position in the Seychelles archipelago and the presence of experienced observers, a large number of vagrant birds have been recorded for the island. There are recent records of breeding and non-breeding seabirds (Feare, 1979), resident land birds (Feare, 1979; Feare & Gill, 1995b) and migrant and vagrant shorebirds (Feare & High, 1977). In the current fieldwork, 14 land birds and waders were recorded (Table 6) of which nine were migrants and five were resident species. Three of the resident species were obvious introductions (barred ground dove, common mynah, Madagascar fody), two of which have been present on the island since early in the twentieth century. Fryer (1910) recorded four land birds on Bird Island: Geopelia striata, Foudia madagascariensis, Gallinula chloropus and (possibly) Bubulcus ibis. The presence of moorhens is interesting given that no standing freshwater was recorded. Feare (1979) suggests that the moorhens recorded may have been vagrants from the granitic islands (Denis Island is another possible, closer, source). By the early 1970s, mynahs had colonised (Feare, 1979) and the Madagascar turtle dove Streptopelia picturata appears to be a more recent colonist (Feare & Gill, 1995b). No endemic land birds were recorded on the island although the turtle doves appear close to the endemic race rostrata (Feare & Gill, 1995b). A single Seychelles fody Foudia sechellarum has been recorded once (Diamond and Feare, 1980). Ten seabird species were observed (Table 7), and there was evidence for breeding of five species. One breeding species previously listed by Feare (1979) was not observed during the present survey (wedge-tailed shearwater Puffinus pacificus). Since 1979, the lesser noddy Anous tenuirostris has been added to the list of breeding seabirds on Bird Island, and large numbers of this species breed in broad-leaved trees including Pisonia 1) grandis. Other seabirds have occasionally bred on the island in recent years, including Sterna saundersii, Sterna bergii, and Sterna anaethetus (Rocamora and Skerrett, 2001). Table 6. Terrestrial birds and waders observed on Bird Island. M = migrant species. Species Bubulcus ibis Charadrius mongolus M Charadrius leschenaultii M Charadrius hiaticula M Pluvialis fulva M Pluvialis squatarola M Numenius phaeopus M Arenaria interpres M Calidris alba M Calidris ferruginea M Streptopelia picturata ssp. Geopelia striata Acridotheres tristis Foudia madagascariensis cattle egret lesser sandplover greater sandplover Common ringed plover Pacific golden plover grey plover Whimbrel ruddy turnstone Sanderling curlew sandpiper turtle dove barred ground dove Common mynah Madagascar fod Table 7. Seabirds observed on Bird Island. Species marked * are known to nest on the island. Species Phaeton lepturus * Fregata minor Fregata ariel Sterna bergii Sterna anaethetus Sterna fuscata * Sterna albifrons/saundersi Anous stolidus * Anous tenuirostris * Gygis alba * white-tailed tropicbird great frigatebird lesser frigatebird greater crested tern bridled tern sooty tern little/Saunder’s tern brown noddy lesser noddy Notes One seen at farm, 27/3/00 Seen in company of greater sandplover on airstrip Several birds seen regularly on airstrip and beaches One individual, grassland around the hotel Several birds seen regularly on grassland Several birds seen regularly on grassland and beaches Seen regularly. Group of 44 birds roosting on beach at North Point, 25/3/00 Seen regularly, on grassland and beaches, in groups of up to 30 Several individuals seen with turnstones on southern beach, 26/3/00 Seen regularly, on grassland and beaches, in groups of up to 20 Seen occasionally in coconut woodland Seen regularly, especially around habitation Seen regularly Seen regularly, especially around habitation Notes Juveniles observed March Large mixed flock of frigatebirds (including many in juvenile plumage) seen over island 26/3/00, some apparently roosting in Casuarinas by airstrip Group of 10-15 with other seabirds and waders roosting on beach at North Point, 25/3/00 Group of 20-30 in Casuarinas by airstrip, 26/3/00 Birds beginning to return to their regular nesting area March Group of up to 80 birds with other seabirds and waders, North Point 25/3/00 Abundant, many with young. Nesting in coconuts and on the ground around the hotel Many in Pisonia trees in woodland, some beginning to build nests Juveniles observed March ph Mammals Three mammals were recorded on Bird Island, of which only one (house mouse Mus domesticus) was feral. Mice occur in semi-natural habitats on Bird Island and one dead individual was recorded. The other species were domestic pigs Sus domesticus, kept in covered pens, and a single domestic dog Canis familiaris. A number of mammal species have occurred at Bird Island in the past but are now extinct. The only native mammals were the “Vaches Marines” after which the island was first named. Stoddart (1972) concludes that these were not dugongs but a seal species, extinct here before the 1880s. Introduced species, now extinct, include goats Capra hircus, rabbits Oryctolagus cuniculus and ship rats Rattus rattus. A semi-wild herd of goats was recorded by Pigott (1969). The rabbit was introduced sometime after 1979; there is no mention of the animal in the accounts by Feare (1979) or Stoddart and Fosberg (1981). Similarly, rats were also a recent introduction, probably arriving on the island in 1967 in a consignment of thatching leaves (Feare, 1979). Rats and rabbits were eradicated in 1995 (Feare, 1999a). Two cats Felis catus were removed at the time of rat eradication (S. Robert, pers. comm.). DISCUSSION The current vegetation and fauna of Bird Island are similar to those of the plateau of Cousin Island in the granitic Seychelles. Like Cousin, Bird Island is free of introduced mammalian predators. Although Cousin is smaller than Bird Island, it supports populations of several endangered endemic land birds of Seychelles. There are no historical records of Seychelles endemic land birds on Bird Island, probably because of the island’s distance from the granitic islands of Seychelles, but also perhaps because of the sparse original vegetation. Human activities (mainly the planting of coconuts) have helped create conditions more favourable to endemic land birds, allowing the development of woodland with the native Pisonia grandis once the plantation fell into disuse and the species (regarded as a weed in managed plantations) regenerated from seed spread by seabirds. Unfortunately, human activities also led to the introduction of the ant Anoplolepis gracilipes and the scale insect Pulvinaria urbicola in the late twentieth century; together these invertebrates appear to have had a severe effect upon the vegetation, with higher-order effects on species dependent upon that vegetation. Anoplolepis also has marked direct effects on crabs, turtle hatchlings and skinks, and nesting seabirds (Feare, 1999a). Despite the presence of crazy ants, densities of other invertebrates were high. However, the composition of invertebrate assemblages had undoubtedly been affected by the ants, with certain taxa being excluded or confined to ant-free areas. The size of invertebrate assemblages on Bird Island and the similarity of vegetation to that of Cousin Island suggest that endemic birds (particularly those that occur on Cousin) could be introduced. However, while food availability would appear to be adequate, the establishment of birds would appear to be seriously impaired by introduced crazy ants. The ants occur throughout the woodland habitats on the island in which the birds would breed. Unless ant-proof nesting boxes could be provided, it is certain that ants would My disrupt nesting attempts. Nesting of sooty terns has already been disrupted by ants, causing them to abandon 1.5 ha of their traditional nesting colony in 1998 (Feare, 1999a). It is possible that the present high density of crazy ants is a natural population explosion associated with the early stages of colonisation of new territory (a “boom and bust” path) as has been noted for some other species (see Williamson, 1996). If so, numbers should decline naturally until a more stable density of ants is reached (in some cases, the introduced species becomes extinct, although this appears unlikely in the case of A. gracilipes). A boom-and-bust pattern has been observed in the case of A. gracilipes on Rodrigues and Agalega, with the decline setting in 10-15 years after colonisation (Lewis et al., 1976). On Mahé, a reduction in the crazy ant population has also occurred, although reasons for the decline may include control measures introduced from the 1970s to 1990s (Haines ef al., 1994). There is no guarantee that a similar pattern will be followed on Bird Island, where biological and physical conditions differ from those on Mahé; some native species (for example, Pisonia) may be lost before any reduction occurs. CONSERVATION RECOMMENDATIONS The first priority for conservation on Bird Island must be the eradication, or at least enhanced control, of crazy ants. Present control measures (which prevent ants from overrunning the hotel and tern colony) include clearing shrubby vegetation and the use of Cypermethrin as a direct toxicant (Feare, 1999b). This helps to maintain refugia for native reptiles and some insect species which are absent, or very rare, over the rest of the island but kills invertebrates other than ants and could present a hazard to other wildlife (including land birds). To achieve control over the island as a whole, much of the woodland vegetation of the island would probably have to be removed to allow chemical controls to be applied. The eradication of ants would be an important conservation gain, as Bird Island is among a small number of islands in the central Seychelles free of introduced mammalian predators. If crazy ant control can be achieved, several endemic land birds could be introduced to Bird Island, including Seychelles magpie-robin Copsychus sechellarum, Seychelles warbler Acrocephalus sechellarum, and Seychelles fody Foudia sechellarum. Habitat management would allow larger populations of all three species to form. Habitat management measures that should be considered include the replacement of coconut in woodland areas with native trees, particularly Pisonia and Morinda, to produce woodland similar to that of Cousin Island. Suppression of scrub and herbs within woodland areas would increase the area of foraging habitat for Seychelles magpie-robin, which prefers to feed in woodland with open ground layers (Komdeur, 1996). The control of mynahs, a potential nest predator, would aid the establishment of introduced land birds. 24 Appendix 1. Plant species recorded from Bird Island (excluding seagrasses) Plants recorded in the current survey (mainly sight records) are numbered. For plants only recorded by previous authors, not in current survey, date of most recent record is given (see below). Taxonomy of dicotyledons as given by Friedmann (1994), of monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>1000 individuals observed); C = Common (100-1000 individuals observed); F = Frequent (10-100 individuals observed); Occasional (3-10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: G = Grassland; W = Woodland; Sc = Scrub; BC = Beach Crest; Cu = Garden/farm. Historical records (in Notes): ' Christensen, 1912; * Stoddart and Fosberg, 1981; > Feare, 1979; i Summerhayes, 1931; z Fryer, 1910; ° Procter, 1970 cited in Stoddart and Fosberg, 1981. Species Status Abund. — Habitats Notes PTERIDOPHYTA Adiantaceae Acrostichum aureum L. N - - Recorded 1912': in error for Denis Island? Davalliaceae l Nephrolepis biserrata (Sw.) Schott N A W Nephrolepis multiflora (Roxb.) Jarrett N - - Recorded 19767 Polypodiaceae Phymatosorus scolopendria (Burm. f.) N - - Recorded 1912! GYMNOSPERMAE Cycadaceae 2 Cycas thuarsii Gaud. I F Cu Only in gardens ANGIOSPERMAE: Dicotyledons Acanthaceae 3 Asystasia sp. B (sensu Friedmann) 21 }8 Sc, W Asystasia multiflora Kl. 2 - - Last recorded 1976”. Same as A. sp. B? Asystasia gangetica (L.) T. Anders. v - - Last recorded 1977. Same as A. sp. B? 4 Pseuderanthemum carruthersii (Seem.) I Je Cu Only in gardens Guillaumin Amaranthaceae 5 Achyranthes aspera (L.) DC. I A W 6 Alternanthera ?tenella Colla. I Je Cu Only in gardens Amaranthus caudatus L. I - - Recorded 19317. Now extinct? 7 Amaranthus dubius Mart. ex Thell. I A G, W Amaranthus lividus L. I = z Recorded 19773 (as A. oleraceus L.). = A. dubius? 8 Gomphrena globosa L. I 18 Cu Only in gardens Annonaceae 9 Annona reticulata L. I R Cu Only in gardens (at farm) Apocynaceae 10 Catharanthus roseus (L.) G. Don. I O W, Cu 25 Species Status Abund. Habitats Notes 11. = Nerium oleander L. I R Cu Only in gardens 12. Ochrosia oppositifolia (L.) K. Schum. N R W, Cu 13. Plumeria rubra L. I R Cu Only in gardens Araliaceae 14 Polyscias sp. I R Cu Only in gardens Balsaminaceae 15. Impatiens balsamina L. I R Cu Only in gardens Bignoniaceae 16 Tabebuia pallida (Lindl.) Miers. I O Cu, G Boraginaceae 17. ~—-Cordia sebestena L. I C W, Cu 18 Cordia subcordata Lam. N Cc BC, W 19 Tournefortia argentea L. f. N € BC Caesalpiniaceae Caesalpinia bonduc (L.) Roxb. N - - Recorded 1910”: extinct? 20 = Caesalpinia pulcherrima (L.) Sw. I O Cu 21 Senna occidentalis (L.) Link I C G Capparidaceae 22 Cleome gynandra L. I Cc G, Cu Cleome viscosa L. I - - Recorded 1977°: overlooked in this survey? Caricaceae 23. -Carica papaya L. I A W, Sc Casuarinaceae 24 = Casuarina equisetifolia J. R. & G. Foster I A BC, W, G Combretaceae 25. _Terminalia catappa L. 2N A W, Sc Compositae 26 ~~ Coreopsis lanceolata L. I C Cu Only in gardens 27 ~~ Dendranthema sp. cultivar I R Cu Only in gardens 28 = _Lactuca sativa L. cultivar I € Cu Only in gardens 29 ~—«- Tagetes patula L. cultivar I O Cu Only in gardens 30 Vernonia cinerea (L.) Less. I A G 31 ~~ Zinnia sp. cultivar I O Cu Only in gardens Convulvulaceae Ipomoea batatas (L.) Lam. I - - Recorded 19317. 32 Ipomoea macrantha Roem. et Schult. N A BE AW. 33. ~~: Ipomoea pes-caprae (L.) R. Br. N C BC Crassulaceae 34. ~— Kalanchoe pinnata (Lam.) Pers. I A W Cruciferae 35.“ Brassica chinensis L. I € Cu Only in gardens Cucurbitaceae Cucurbita sp I : - Recorded 1976’. Intermittent cultivation? Cucurbita cf. maxima Duchesne I . - Recorded 1976”, Intermittent cultivation? Cucurbita moschata Duchesne - - Recorded 1977°, Intermittent cultivation? 36 ~—- Trichosanthes cucumerina L. I F W Euphorbiaceae 37. ~— Acalypha indica L. A G 38 Acalypha wilkesiana Muell. Arg. ] F Cu, W 26 Species Status Abund. Habitats Notes 39. = Codiaeum variegatum L. Euphorbia cyathophora Murr. 40 = Euphorbia hirta L. Euphorbia prostrata Ait 41 Euphorbia thymifolia L. 42 = Euphorbia tirucalli L. 43 Jatropha pandurifolia L. Pedilanthus tithymaloides (L.) Poit. 44 ~~ Phyllanthus amarus Schumach. & Thonn. 45 Phyllanthus maderaspatensis L. 46 = Phyllanthus pervilleanus (Ballon) Miill. Arg. 47 Ricinus communis L. Goodeniaceae 48 Scaevola sericea Vahl Guttiferae 49 = Calophyllum inophyllum L. Hernandiaceae Hernandia nymphaeifolia (Presl) Kubitzki Labiatae Plectranthus sp. 50 Solenostemon sp. cultivar Lauraceae Sil Cassythea filiformis L. Lecythidaceae Sy Barringtonia asiatica (L.) Kurtz Lythraceae Pemphis acidula Forst. Malvaceae 53. ~~ Abutilon indicum (L.) Sweet 54. = Gossypium hirsutum 5) Malvastrum coromandelianum (L.) Garcke 56 Sida acuta Burm. f. Sida pusilla Cav. 57 Thespesia populnea (L.) Soland. ex Correa Moraceae 58 Artocarpus altilis (Parkins.) Fosb. Ficus benghalensis L. 59 Ficus ?benjamina L. Ficus lutea Vahl Moringaceae 60 Moringa oleifera Lam. Myrtaceae 61 Syzygium samarangense (B1.) Merr. & I F Cu I 2 s I A G 1 cy z I A G I R Cu I O Cu 1 2 : I A G I A G, Sc N A W, Sc I e W, Sc N BE Sc N O Cu, G N s E O Cu N A BESSc N O Cu 9 a S 2 | C W, Sc I C W, Sc I A W I O W N P :. N F BC, W I R W I 5 rs I R Cu N e : I F GueSc I R Cu Only in gardens Recorded 19314, in error for Denis Island? Recorded 1977°. = E. thymifolia? Only in gardens Only in gardens Recorded 1976’. Overlooked this survey? Trees recently planted Recorded 1910° (as H. sonora L.): extinct. Recorded 1976° Only in gardens Recorded (in error?) 19314 Recorded 1976’ (as S. parvifolia DC): overlooked in this survey? Recorded 19767: Extinct? Only in gardens Recorded 1976? (as F. nautarum Baker): Extinct? Perry 27 Species Status Abund. _ Habitats Notes Nyctaginaceae 62 Boerhavia repens L. 2N A G Boerhavia diffusa L. (sensu lato) ? 3 - Recorded 1910°. = B. repens? 63 Bougainvillea sp. cultivars I O Cu Only in gardens Mirabilis jalapa L. I : < Recorded 1976’, 1977”. Overlooked in this survey? 64 ~~‘ Pisonia grandis R. Br. N A W Papilionaceae 65 ?Canavalia sp. u € Be 66 Sesbania ?sericea (Willd.) Link I F W, Sc Passifloraceae 67 ~~ Passiflora edulis Sims I O W 68 Passiflora suberosa L. I A W, Sc Portulacaceae 69 Portulaca grandiflora Hook I O Cu Only in gardens 70 Portulaca oleracea L. N A G, BC Rubiaceae 71 Guettarda speciosa L. N j2 BC Morinda citrifolia L. II Recorded 1910”: extinct? Sapindaceae Cardiosperma halicacabum L. 2N - - Recorded 1910”: extinct? Scrophulariaceae Striga asiatica (L.) G. Ktze. ?1 - - Recorded 1910: extinct? Solanaceae Je Cu Only in gardens 72 ~~ Capsicum frutescens L. - Recorded 1910: extinct I Nicotiana tabacum L. I 78 Solanum americanum Mill. I I I O G 74 ~~ Solanum lycopersicum L. O Cu Only in gardens 75 Solanum melongena L. Ie Cu Only in gardens Surianaceae 76 = Suriana maritima L. N A BC Turneraceae 77 Turnera angustifolia Miller I J8 W, Sc Verbenaceae 78 Phyla nodiflora (L.) Greene I A G 79 ~~ Stachytarpheta jamaicensis (L.) Vahl. € GySc 80 = Stachytarpheta urticifolia Sims I O GySc¢ Zy gophyllaceae 81 Tribulus cistoides L. 1 F G ANGIOSPERMAE: Monotyledons Agavaceae Agave rigida Northrop var. sisalana Perr. I - - Recorded 1976°, 1977° Ex Engelm. 82 Agave/Yucca sp. I O Cu Only in gardens Amaryllidaceae 83 ?Hymenocallis littoralis (Jacq.) Salisb. wl R G 84 Zephyranthes sp. I Is Cu Only in gardens Araceae 85. Alocasia macrorrhiza (L.) G. Don. I A W Colocasia esculenta (L.) Schott I - - Recorded 1976*: extinct? Commelinaceae 86 Tradescantia spathacea Swartz. I R Cu Only in gardens 28 Species Status Abund. Habitats Notes Cyperaceae 87. Cyperus conglomeratus Rottb. N jz BC 88 Cyperus ?rotundus L. 4 A G 89 Mariscus dubius (Rottb.) Fischer N € W, Sc 90 = Mariscus ligularis (L.) Urb. 2N (e G Gramineae 91 Cymbopogon sp. I le Cu Planted at farm 92. — Cynodon dactylon (L.) Pers. q A Gi Be 93 Dactyloctenium ctenoides (Steud.) Bosser ? A G, BC 94 ~— Digitaria sp. (D. ?horizontalis) ? Cc W 95 Eleusine indica (L.) Gaertn. ? A G, Sc 96 Enteropogon ?sechellensis (Baker) Dur. & N A G Schinz Enteropogon monostachyum K. Schum. ex ? - - Recorded 19767 Engl. 97 Eragrostis tenella (L.) P. Beuv. ? A G Eragrostis tenella var. insularis Hubb. ? - - Recorded 1941 98 Eragrostis ?subaequiglumis Renvoize u A G 99 ~~ Lepturus ?radicans (Steud.) Camus ? A W Lepturus repens (Forst.) R. Br. ? - - Recorded 1931* 100.) Panicum repens L. u IF Sc ? - - Recorded 1931? Pennisetum polystachyon (L.) Schult. 101 Pennisetum sp. (purple) 21 € Cu Only in gardens R 102 Saccharum officinarum L. I Cu Only in gardens Sporobolus virginicus (L.) Kunth. N - - Recorded 1970° Stenotaphrum micranthum (Des.) C. E. ? = - Recorded 1976? Hubb. Liliaceae Crinum sp. 21 - - Recorded 1976’. = Hymenocallis littoralis ? Marantaceae Maranta arundinacea L. I - - Recorded 1970° Musaceae Musa sapientum L. I - - Recorded 19767 Orchidaceae 103. Dendrobium sp. I O Cu Only in gardens Palmae 104. Cocos nucifera L. N A G, W, Sc; BE Pandanaceae 105. Pandanus sanderi Hort. I C Cu Only in gardens Typhaceae Typha javanica Schnizl ex Rohrb. N - - Recorded 1931*: in error for Denis Island? 7) $@pukancyrnw apn 7 i _ | as = ve ee MICHADL1 HIRD’ TERENCE Vie KATIE fH ; -_ ant MERMAL 1, SILA ms = ae - fe : - s.2> ? | eR AMY. YOPOMAPTIIY | Xie 1. 7 x E 4 a r y 7 : - we -.. A h tapes hits) 48 9 weil eens newt PAD wilh Oa. cians A anly Ss Ai) Ti 1p. Viti thes x T Eypag) " wale ; MEL uP = ee cS ei ik easy Nien. 2 eee 0 ipa BRR. Hopmg previ, « Toe rly ] tal les tye iu a the aa ae rij “i eer r é —4 et wey 7 - vr < ~ — . ic USS (Oi tls; Pert oh } ih ates, ' Lage 1 Ne ana te ot ” is | | i fy : ir : ‘ Re are me ws he 7 a the ie on : ; = . ral) er a Wg ae ety gt cameo flare i es : oi . uu nae ned apenas peer ; 34 ; Vay nhsare a 2 Riiw C1. 2 rp ergy) | ' A ce nie Gitte LLCry ey CNL EW rie! ’ baer viet Fiz ) ochre: VRE ay: Pe tas Perry dW ay ry f ; a t. SL TE- Ah Meee Lanse , 7 on 1 rs ay ss ua — — 6% BA aie valor Ke Vy en wr Ae GY LD), ga | ae Birii1s A Pili Gian y Maa Vali Wali: PRS ANCE vs si fie Coyle thal D n he fi evarhe ‘ad “finde Agra pelt iciilin Lite anireh) iy bili ee wa - 7 fi = ay —— 7 At = 5 oo a 7 Dear ei |! i ~ ss ‘= xs - 7 A a et) _ Pie ary Te a - acyl Legend «Contours [x] Vegetation plots 200 metres Figure 1. Conception: physical map, with locations of vegetation plots. CONCEPTION BY MICHAEL J. HILL’, TERENCE M. VEL', KATHRYN J. HOLM’, STEVEN J. PARR?’ and NIRMAL J. SHAH! GEOLOGY, TOPOGRAPHY AND CLIMATE Conception is a small granitic island with an area of approximately 60 ha, situated only 1,600 m from the east coast of Mahe, the largest of the granitic Seychelles islands. At its highest point it reaches 130 m above sea level (Fig. 1). The island is dominated by rocky, sloping ground. A single raised ridge, flat-topped at its northwestern end dominates the island. In the south east, a small lower hill (reaching only 20 m above sea level) is separated from the rest of the island by a low boulder-filled fault. There is no coastal flat land and no sandy beach. Most of the land is sloping ground between 10 and 100 m above sea level (Table |). Geologically, the island is similar to the nearby west coast of Mahé, dominated by porphyritic granite (Braithwaite, 1984). The soils of Conception are mainly red earths, strongly eroded on steeper slopes. On the open glacis areas, soils are restricted to pockets between rocks Standing water on the island is very limited. For much of the year a trickle of fresh water runs down rocks into the sea at the landing place (CK 1940 8432). At the height of the rainy season, ephemeral streams carry rainwater to the sea, although these were not observed during the assessment surveys of the island.A few small pools are less short-lived; in February, a shallow (1-2 cm deep) pool with an open surface of less than 2 m° was present in woodland on the eastern side of the island, and several deeper pools were observed in hollows on open rock at the top of the island (at CK 1870 8462); although exposed, some of these contained larvae of aquatic insects. No weather data exist for Conception but the climate of the island probably follows a similar pattern to that of nearby Mahé. Port Glaud, on the west coast of Mahé opposite Conception, has lower annual rainfall than Beau Vallon to the north or Victoria to the east (Walsh, 1984). Although it is in the generally wetter northern part of Mahé, it is sheltered from the prevailing winds (in particular the north west wind of the rainy season) by hills. ' Nature Seychelles, PO Box 1310, Mahé, Seychelles. Email: birdlife@seychelles.net 2 9 . 6 and ~ Q ~ 1991 Casa Marcia Crescent Victoria, British Colombia, Canada. * Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, UK 32 Table 1. Area of Conception by altitude (calculated from maps published by Directorate of Overseas Survey (UK)/Seychelles Government). Altitude range (m. asl.) Area (ha) Percentage total area HISTORY Few early records exist for the island. Following the establishment of the first French settlement in Seychelles in 1770, the proximity of Conception to the main island of Mahé probably encouraged exploitation of the island even though landing was difficult all year round. While Conception had at the time little interest for agriculture, it possessed other resources, including giant tortoises, which were among the principal resources of the islands. Exploitation was such that by 1787, Malavois wrote of Conception “there were formerly on this island large quantities of tortoises, which were there without having been brought there. Now there is only a small number left and these are generally small” (in Fauvel, 1909). Despite the lack of freshwater, the island was settled, and there are now ruins of several small buildings. Coconut plantations were probably started in the nineteenth or early twentieth century, when a range of other species including cinnamon Cinnamomum verum and fatak grass Panicum maximum was introduced. Plantations throughout the Seychelles were abandoned in the late twentieth century. Today the island (although still privately owned) has no permanent human population, and plantations are unexploited. The only visitors are staff of the Seychelles Ministry of Environment and Transport and occasional fishermen. FLORA AND VEGETATION Flora A total of 92 plant species was recorded on Conception, including eight ferns and 84 angiosperms (Appendix 1). Of the angiosperms, 37 (44.0%) species are regarded as introduced (Friedmann, 1994) and 35 (41.7%) native. Of the native taxa (species and subspecies), nine are endemic to the Seychelles (10.7% of the total flora). The proportion of the flora made up of introduced species was lower than that for the Seychelles as a whole, and the proportion of Seychelles endemics higher; of the total Seychelles flora, around 54% are introduced and 9% endemic (Procter, 1984). Compared to the flora of other small islands, Conception is relatively rich in endemic species. This high endemicity is due to the proximity of the island to Mahé, where almost all the endemic plant species of Seychelles are represented. The rocky slopes of the island and 33 soils of little agricultural value may also have contributed to the survival of a number of endemic plants here. Few previous botanical surveys have been carried out on the island and Robertson (1989) lists just two species for Conception: Premna serratifolia (as P. obtusifolia R. Br.), and coconut Cocos nucifera. Both were recorded in the current survey. ‘Of the introduced plants established on Conception, 13 were invasive weedy species. Several of the woody weeds known to be particularly invasive on the smaller islands of Seychelles were present, including cocoplum Chrysobalanus icaco and cinnamon Cinnamomum verum (both abundant). Other potentially invasive introduced trees included Alstonia macrophylla, Syzygium jambos (well established on rocky areas on top of the island), Psidium cattleianum, and cashew Anacardium occidentale. Coconuts were common, especially on the south east and south west slopes of the island. Vegetation The extents of major vegetation types on Conception are shown in Table 2 and Figure 2. Most of Conception is dominated by mixed forest (exotic and native species), with some open glacis and scrub, and areas of coconut monoculture. Table 2. Extent of major vegetation types, Conception Island. Altitude Vegetation type Appox. area (ha) 32 >10masl Woodland (predominantly introduced) Coconut with regeneration Scrub (native) Bare rock <10masl Woodland (predominantly introduced) Coconut with regeneration Bare rock a — wi wee Seon) Thirty vegetation plots were studied in hill woodland/scrub with a combined area of 3,000 m° (approximately 0.8% of the total area of this vegetation type). A summary of results is shown in Table 3. On average, plots had a relatively high density of trees with a fairly complete canopy (mean canopy cover = 64%). The tree layer had low species richness (only nine species were recorded) and was dominated by an introduced species, Cinnamomum verum (see Table 4). The shrub layer was more species-rich than the tree layer with 13 species represented, eight of them native. The most widespread species, and the species showing the greatest dominance of the plots where it occurred, was the endemic palm Phoenicophorium borsigianum (see Table 5). Cinnamomum verum was widespread in the shrub layer, occurring in 73% of plots. Cocos nucifera occurred in fewer than half of the plots, but in these plots it occupied 14% of the shrub layer. The herb layer included tree seedlings and herbaceous species. Twenty-five species were present, 15 of which were native. The most widespread species were Nephrolepis sp. and Cinnamomum verum (see Table 6). Species forming the largest proportion of the ground cover were the ferns Phymatosorus scolopendria and Nephrolepis sp. 34 Legend: vegetation types ag Bare rock ‘_ | Glacis/native scrub Scaevola scrub Coconut scrub ae aS [4 Tabebuia woodland 5 _——= ‘ Mixed exotic woodland 200 metres \ ‘oo 0) Casuarina Figure 2. Conception vegetation Table 3. Conception vegetation plot summary. Plots Mean Mean Meanshrub Meanherb Openleaf Bare Dead wood altitude —_ trees layer cover layer cover litter rock (pieces per (masl) ha’ (%) (%) cover (%) (%) plot) 30 56 667 SHES 37.9 D9) 33.8 1.8 be) Table 4. Conception Island: plants in tree layer (>5 m). No. individuals % individuals Introduced species Adenanthera pavonina 19 35) Anacardium occidentale 13 6.5 Cinnamomum verum 116 58.0 Native species Calophyllum inophyllum 15 es Canthium bibracteatum 12 6.0 Cocos nucifera 15 Wes Intsia bijuga 1 0.5 Premna serratifolia 7 35) Tabernaemontana coffeoides 2 1.0 Total Table 5. Conception Island: species of shrub layer. Percentage shrub cover is the mean cover by the species for those Plots in which the species occurs. No plots —_ % shrub cover Introduced species Adenanthera pavonina 3 DD Anacardium occidentale 7 6.3 Cinnamomum verum DD O19 Strychnos spinosa 1 1.0 Native species Calophyllum inophyllum 10 3.4 Canthium bibracteatum 14 7.0 Cocos nucifera 12 14.0 Dracaena reflexa 7 2.4 Ficus lutea 4 1.0 Ficus reflexa 1 8.0 Phoenicophorium borsigianum 24 20.6 Premna serratifolia 9 332 Tabernaemontana coffeoides 2, 3.0 Total no. of plots 30 36 Table 6. Conception Island: species of herb layer. Only species occurring in three or more plots shown. Percentage herb cover is the mean cover by the species, for those plots in which the species occurs. No plots % herb cover Introduced species Adenanthera pavonina 14 1 Asystasia sp. B 1] 2 Cinnamomum verum 28 5 Panicum maximum 3 ey, Vanilla planifolia 7 2 Native species Calophyllum inophyllum i

2 mm included (number in parentheses = number of invertebrates excluding ants). Mean no. individuals per 5 traps SE season NW season 34.4 (9.1) 50/3:(13-5) 61.8 (9.4) 61.1 (16.0) Conception Hill woodland Mean for all granitic islands Leaf-insect Counts Leaf-insect counts were carried out for seven tree and shrub species, five of these in both seasons (Table 8). The highest density of invertebrates (in terms both of individuals per leaf, and per square metre of leaf) was on the native tree Premna serratifolia. However, the introduced Cinnamomum verum had high leaf counts in both seasons, and density of invertebrates observed on Cinnamomum leaves exceeded that of most native species in both seasons. Three of the five species which were counted in both seasons showed highest density of invertebrates in September rather than February. This runs counter to the trend on most islands, where leaf counts are significantly greater during the wetter north west monsoon, and may reflect weather conditions specific to Conception for the 1999/2000 season. Table 8. Density of invertebrates on foliage, Conception. n=no. of leaves counted; NI = number of individual invertebrates. Species SE season (September) NW season (February) n mean NI mean NI n mean NI mean NI leaf! m” leaf! m? Introduced species Anacardium occidentale Cinnamomum verum 310 1100 0.606 Oa 0.854 350 0.223 39.34 1300 0.978 155.34 Native species Calophyllum inophyllum Canthium bibracteatum Ficus lutea Premna serratifolia Tabernaemontana coffeoides 450 1.009 108.06 550 0.098 49.94 50 0.720 43.00 250 2.548 349.42 Malaise Trapping Malaise trapping was carried out in plateau and hill woodland habitats, during both seasons. Main results are summarised in Table 9. The number of individuals trapped was similar in both seasons (slightly larger in September). 39 The most abundant taxonomic groups were Diptera, Lepidoptera and Hymenoptera. Other invertebrate groups represented included arachnids (spiders), Coleoptera, Collembola, Hemiptera, Orthoptera and Psocoptera. The majority of taxa collected have yet to be identified to species level. Table 9. Malaise trap assemblages, Conception. NI = number of individuals. No. traps Mean NI trap” Diptera 558 59.0 Lepidoptera 221 23.4 Hymenoptera 78 8.2 Coleoptera 793} 2.4 Others Observation A list of species observed or collected is given in Table 10. In both September and February, dragonfly species were observed flying over open glacis on the top of the island. Pools here must be present for much of the year although probably not permanent. In February, mosquito larvae were abundant in these small pools so it is possible that dragonflies breed on the island. The introduced crazy ant Anoplolepis gracilipes was not trapped in pitfall traps, but small numbers of ants were observed in the vicinity of the old settlement. This species is widespread on Mahe, where it is regarded as a nuisance (Haines ef a/., 1994), and on Bird Island it has had negative effects on the island’s ecosystems and conservation status (Feare, 1999a; Hill, in prep.). On Conception, it appears very restricted in distribution, suggesting that the species was recently introduced. 40 Table 10. Invertebrates observed and collected, Conception Island. Order Family Species Notes Mollusca Acavidae Stylodonta unidentata (Chemnitz, 1795) Endemic snail Achatinidae Achatina fulica (Bowditch, 1822) African land snail Helicinidae Helicina theobaldiana Nevill, 1871 Endemic snail Subulinidae Subulina octona Bruguiére, 1792 Arachnida: Araneae Tetragnathidae Nephila inaurita (Walckenaer, 1841) Crustacea: Decapoda Coenobitidae Coenobita brevimanus Dana, 1852 Land hermit crab Grapsidae Geograpsus crinipes (Dana, 1851) Land crab Myriapoda: Chilopoda Scolopendridae § Scolopendra subspinipes (Leach, 1918) Diplopoda Trigoniulidae Spiromanes ?braueri (Attems, 1900) Insecta: Coleoptera Scarabaeidae Oryctes monoceros (Olivier, 1789) Perissosoma aenescens Waterhouse, 1875 Hymenoptera Anthophoridae = Xylocopa caffra (Linnaeus, 1767) Apidae Apis mellifera adansoni Latreille, 1804 Formicidae Anoplolepis gracilipes (Smith, 1857) Cardiocondyla emeryi Forel, 1881 In pitfall traps ?Camponotus thomasetti Forel, 1912 In pitfall traps Odontomachus troglodytes Santschi, 1914 In pitfall traps Pachycondyla melanaria (Emery, 1894) In pitfall traps Plagiolepis ?alluaudi Emery, 1894 In pitfall traps Plagiolepis ?exigua Forel, 1894 In pitfall traps ?Solenopsis seychellarum Forel, 1912 In pitfall traps Tapinoma melanocephala (Fabricius, 1793) In pitfall traps Technomyrmex albipes (Smith, 1861) In pitfall traps Vespidae Polistes olivaceus (de Geer, 1773) Lepidoptera Hesperiidae Borbo sp. Odonata Libellulidae Diplacodes trivialis (Rambur, 1842) ?Orthetrum stemmale wrightii (Selys, 1877) ?Pantala flavescens (Fabricius, 1798) Tramea limbata Selys, 1878 Phasmatodea Phasmatidae Carausius sechellensis (Bolivar, 1895) On Agave Discussion: Invertebrates Pitfall assemblages were slightly smaller than the mean size of assemblages on the granitic islands (Table 7). In general, plateau sites on granitic islands showed higher invertebrate catches in pitfall traps than hill sites. Conception had no plateau and little land under 10 m asl. Leaf counts suggest that the cinnamon forest has high insect productivity: insect counts on cinnamon leaves are high, although the species is not native. This is the dominant tree species of the island. Although most of the invertebrates counted are ants, and bugs attended by ants (especially mealy bugs), the supply of invertebrates for 4] insectivores with a wide tolerance of small food items is good. Seychelles white-eye, for example are known to take mealy bugs (Feare, 1975). Invertebrates on vegetation and in flight-intercept (Malaise) traps were more abundant in September than in February, contrary to expectations. The fact that both methods showed this decline suggests that it was a real effect, perhaps caused by local environmental conditions (especially, weather conditions) in 1999/2000. Although few endemic species were collected in the current survey, Conception probably supports a large endemic invertebrate fauna, in addition to the introduced or cosmopolitan species found on most islands of the Seychelles. The island is close to Mahé, which has a large endemic fauna, and supports a range of endemic plants including native palms (which provide important microhabitats for endemic invertebrate species in leaf axils). VERTEBRATES Reptiles Reptiles observed during the course of fieldwork were recorded, and a list of species identified is given in Table 11. The list includes four lizards, all endemic to the granitic Seychelles. One of the endemic giant tortoises of the granitic islands was recorded in the late eighteenth century (Bour, 1984). Table 11. Reptiles observed on Conception. Family Species Notes Gekkonidae Ailuronyx seychellensis (Dumeril & Bibron, 1836) | Observed 26/9/99 and 22/2/00 Phelsuma spp. Two morphotypes observed Scincidae Mabuya sechellensis (Dumeril & Bibron, 1836) Janetaescincus braueri or Pamelaescincus Burrowing skink gardineri Birds In total, nine land birds and waders were recorded during the course of fieldwork (Table 12). Three of these were Seychelles endemics, two of which (Seychelles kestrel Falco araea and Seychelles white-eye Zosterops modestus) are globally threatened. The Seychelles white-eye is only known on two islands, Mahé and Conception; the Conception population was discovered in 1997 (Rocamora, 1997). The population on Conception is at least 250 birds, the Mahé population only about 50 (Rocamora and Francois, 1999). Four seabird species were observed (Table 13) and at least one of these (the fairy tern) probably nests on the island. 42 Table 12. Land birds and waders observed on Conception. M = migrant species; E = Seychelles endemic species. Species Notes Falco araea E Seychelles kestrel Two individuals observed around hill glacis, 26/9/99. One individual over hill glacis, 23/2/00 Arenaria interpres M ruddy turnstone One individual observed flying close to island (over sea), 27/2/00 Streptopelia picturata Madagascar turtle dove Observed every day in hill woodland and picturata (occasionally) more open habitats Geopelia striata barred ground dove A few individuals observed in hill grassland, February 2000 Alectroenas pulcherrima E Seychelles blue pigeon Observed every day Tyto alba ?barn owl Plucked feathers of Fairy Tern observed in coconut woodland, February Zosterops modestus E Seychelles white-eye At least 200 resident birds (G. Rocamora, pers. comm.). Young birds observed in February Acridotheres tristis common mynah Observed every day, especially in coastal habitats Foudia madagascariensis Madagascar fody Regularly seen in small numbers in hill grassland, open scrub and coconut forest near Camp Table 13. Seabirds observed on Conception. Species Notes Phaeton lepturus white-tailed tropicbird § Observed flying in amongst trees in hill woodland on the eastern side of the island (close to point E10) on 26/9/99. Occasionally observed flying close to island in February Fregata ariel lesser frigatebird Two individuals displaying in flight over glacis, 22/2/00 Anous tenuirostris lesser noddy Roosting in large numbers (hundreds of individuals) in large Casuarina trees, February Gygis alba fairy tern Regularly observed in small numbers Mammals Only two species of mammals were recorded in the course of fieldwork: one bat and one rat. The endemic Seychelles fruit bat Preropus seychellensis Milne Edwards 1887 was regularly observed and heard both in September and February, particularly in Casuarina trees around the old settlement area. Rodent trapping was carried out in September 1999, and February 2000 (Table 14). Two traplines were established, both in hill woodland with coconut and cinnamon. Only one species of rodent, Rattus norvegicus L., was trapped. 43 Table 14. Results of rat trapping, Conception. Rats per 100 trap- Rats per 100 trap- Trap-nights No. of rats nights nights (uncorrected) (corrected)* Dates 22 — 29/9/99 140 82 58.57 88.65 23 — 28/2/00 ay 49 43.75 59.76 Total (SE) 35.34 Total (NW) *Corrected to account for the effect of closed traps: Cunningham and Moors, 1996. Trapping rates were high for both trapping periods, although higher in September during the dry season when food and water stress were greater and rats more likely to be trapped. The generally high trapping rates could be due to the more terrestrial nature of Norway rats compared to ship rats (found on most other islands surveyed) which feed in trees and palms to a greater extent. Biometric data show that the Norway rats on Conception are relatively small compared to continental populations (and possibly populations on Mahé), although larger and heavier than the ship rat R. rattus (which is more widespread in Seychelles). Almost all individuals showed a tail length less than the head plus body measurement, a trait which distinguishes them from ship rats. The only natural enemy of rats on Conception is probably the barn owl. These owls were introduced to Seychelles in order to control rats (Penny, 1974) but seem to have little impact on rodent populations. The impact of rats on other vertebrates and invertebrates is difficult to gauge, although probably severe. In both seasons, many young plants of the endemic thief palm (Phoenicophorium borsigianum) showed rat damage; the animals had gnawed palm petioles, causing collapse of the leaf-stem or complete loss of a leaf. This damage was seen even on palms with trunks over two metres in height. CONSERVATION RECOMMENDATIONS Conception is a relatively small island which has conservation interest principally because of the presence there of a population of the Seychelles white-eye Zosterops modestus, an endangered endemic bird. Natural populations of this species only occur on two islands, Mahé (where it is very rare) and Conception (Rocamora and Francois, 1999, 2000). Predation by mynahs, bulbuls (on Mahé) and rats may affect the breeding success of the species and rat eradication on Conception would probably be advantageous to the white-eyes, as well as other endemic elements of the flora and fauna. While eradication of rats would also reduce populations of ground-feeding birds such as doves, white-eyes would be at little risk. Translocations of white-eyes to other islands have been proposed, and in 2001 birds were moved to Frégate (Rocamora ef al., in press). Because Conception remains the stronghold of the species, translocations of other endangered species to Conception should not be attempted. 44 The flora of Conception is of interest because of the prominence of endemic species. Probably as a result of the island’s proximity to the largest island of the archipelago, Mahé, which has 65 of the granitic Seychelles endemic plant species, and the limits to human exploitation imposed by the difficulty of landing, lack of fresh water and its rocky slopes, nine endemic species occur on the island. Some of these species occur in large numbers, including the endemic palm Phoenicophorium borsigianum which is restricted to larger islands and their satellites. Many endemic invertebrates are found in association with endemic or native plants; Scott (1933) found a close association between endemic invertebrates and endemic vegetation, particularly native palms and Pandanus species. Conception is therefore likely to harbour a number of endemic invertebrates in addition to its plant species. As with the nearby island of Thérése, the island resembles lowland habitats of Mahé and thus presents the opportunity to conserve habitats and species present on the larger island, in more controlled (potentially predator-free) conditions. However, since the cinnamon forest of Conception appears vital for the survival of the white-eye, habitat management such as removal of exotics could not be carried out on a large scale. Some exotics (eg. Anacardium) and Cocos might be controlled in limited areas to encourage the growth of native shrubs such as Premna. 45 Appendix 1. Plant species recorded from Conception (excluding seagrasses) Taxonomy of dicotyledons as given by Friedmann (1994), of monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>1000 individuals observed); C = Common (100-1000 individuals observed); F = Frequent (10-100 individuals observed); Occasional (3-10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: HG = Hill grassland; HW = Hill Woodland/scrub; Co = Hill Coconut woodland; Gl = Glacis; BC = ‘Beach Crest’. Species Status Abund. Habitats PTERIDOPHYTA Adiantaceae 1 Acrostichum aureum L. N 2 BC, Co Davalliaceae 2 Davallia denticulata (Burm.) Mett. N A HW, Gl 3 Nephrolepis biserrata (Sw.) Schott N A HW, Gl 4 Pellaea ?doniana Hooker N O HW Lycopodiaceae 5 Lycopodium cernuum L. 2N O HW Polypodiaceae 6 Phymatosorus scolopendria (Burm. f.) N A HW Psilotaceae 7 Psilotum sp. N (CE HW Vittariaceae 8 Vittaria sp. N O Gl ANGIOSPERMAE: Dicotyledons Acanthaceae 9 Asystasia sp B. (sensu Friedmann) 71 A HW, Gl Amaranthaceae 10 ~=Lagrezia madagascariensis (Poir.) Moq. N O BC Anacardiaceae 11 = =Anacardium occidentale L. I A HW Annonaceae 12. Annona cherimola Mill. I B HG, HW Apocynaceae 13. Alstonia macrophylla Wall ex G. Don. I O HW 14 Catharanthus roseus (L.) G. Don. I O HW, Gl 15 = Plumeria rubra L. I R HW 16 Tabernaemontana coffeoides Boj. ex A. DC. N A HW Araliaceae 17. ~— Gastonia sp. 13) R Gl Asclepiadaceae 18 Sarcostemma viminale (L.) Alton N F Gl, HW Bignoniaceae 19 = Tabebuia pallida (Lindl.) Miers. I C HW Cactaceae 20 ~~ Rhipsalis baccifera (J. Mill.) Stearn N O Gl Caesalpiniaceae 21 ~~ Intsia bijuga (Coleb.) O. Kuntze N O HW 22 Senna occidentalis (L.) Link I F HG, Gl 46 Species Status Abund. Habitats Casuarinaceae 23. Casuarina equisetifolia J. R. & G. Foster I le HW Chrysobalanaceae 24 ~=— Chrysobalanus icaco L. I Fe HW Combretaceae 25 Terminalia catappa L. 2N R HW Compositae 26 ~— Emilia sonchifolia (L.) Wight I O Gl Dai Vernonia cinerea (L.) Less. O HW Convulvulaceae 28 = Ipomoea obscura (L.) Ker Gawl. I F HW 29 = Ipomoea pes-caprae (L.) R. Br. N A BC, Gl 30 = Ipomoea venosa (Desr.) Roem. & Schult. N C HW, Co Euphorbiaceae 31 = Euphorbia pyrifolia Lam. N F Gl 32. ~~ Phyllanthus amarus Schumach. et Thonn. I O HG Goodeniaceae 33. = Scaevola sericea Vahl. N A BC Guttiferae 34 = Calophyllum inophyllum L. N E HW Labiatae 35. Plectranthus amboinicus (Lour.) Spreng. 21 € Gl Lauraceae 36 =Cinnamomum verum Pres]. I A HW Lecythidaceae 37. ~—- Barringtonia asiatica (L.) Kurtz N ie BC Loganiaceae 38 ~—= Strychnos spinosa Lam. I Is HW Malvaceae 39 Abutilon indicum (L.) Sweet 21 O HG Meliaceae 40 Xylocarpus moluccensis (Lam.) Roem. N R BC, HW Mimosaceae 41 = Adenanthera pavonina L. I C HW Moraceae 42 Ficus lutea Vahl. N C HW, Gl 43 Ficus reflexa Thunb. ssp. seychellensis (Baker) Berg E(ss) lg HW Myrtaceae 44 — Psidium cattleianum Sabine I R HW 45 — Syzygium jambos (L.) Alston I C HW, Gl 46 =Syzygium wrightii (Baker) A. J. Scott E R HW Nyctaginaceae 47 Pisonia grandis R. Br. N R PG Papilionaceae 48 Desmodium incanum DC. I C HW 49 Desmodium triflorum (L.) DC I zi HW 50 = Teramnus labialis (L.) Spreng. I R HW Passifloraceae 51 Passiflora foetida L. I F HW 52. Passiflora suberosa L. I € HG, HW Rubiaceae 53 Canthium bibractatum (Baker) Hiem. N A HW, Gl 54 Pentodon pentandrus (Schumach.et Thonn.) Vatke I O BC, GI 47 Species Status Abund. Habitats Rutaceae 55. Citrus reticulata Blanco I O HW Sapindaceae 56 = Allophyllus sechellensis Summerh. E O HG Sapotaceae S7/ Mimusops sechellarum (Oliv.) Hemsl. E R Gl Tiliaceae 58 = Triumphetta rhomboidea Jacq. I 3 Gl Turneraceae 59 = Turnera angustifolia Miller I Ki HW Verbenaceae 60 Clerodendron speciosissimum Morren I R HW 61 Premna serratifolia L. N A HW, Gl 62. Stachytarpheta jamaicensis (L.) Vahl. I F HW 63 Stachytarpheta urticifolia (Salisb.) Sims. I € HW ANGIOSPERMAE: Monotyledons Agavaceae 64 ~=-Furcraea foetida (L.) Haw. I F HW Bromeliaceae 65. Ananas comosus (L.) Merr. I (C Gl, HW Cyperaceae 66 Cyperus compressus L. 2 O Gl 67 ~Fimbristylis cymosa R. Br. ? A BC, Gl 68 Fimbristylis sp. (glacis sedge) e C Gl 69 — Kyllinga polyphylla Willd. ex Kunth N € HW 70. ~=Mariscus dubius (Rottb.) Fischer N A HW, GI 71 ~~ Mariscus ligularis (L.) Hutchinson 2N Ie HG, HW 72. Pycreus polystachyos (Rottb.) P. Beauv. ? a HW Gramineae WB Axonopus compressus (1.) P. Beauv. 2 F HW 74 ~~ Brachiara umbellata (Trin.) W. D. Clayton N A HW 75 ?Brachiara sp. y C HW 76 ~—= -Ischaenum heterotrichum Hack. ? A HW, Gl WY Oplismenus compositus (L.) P. Beuv. N A HW 78 = Panicum brevifolium L. N A HW 719 Panicum maximum L. 2 C HW, Gl 80 = Paspalum scrobiculatum L. ? R HW 81 = Pennisetum polystachyon (L.) Schult. ? (C Gl 82 ?Sacciolepis curvata (L.) Chase ? A HW 83 Setaria barbata (Lam.) Kunth. ? O HG 84 Stenotaphrum dimidiatum (L.) Brogn. N A HG, HW Liliaceae 85. Dracaena reflexa Lam. var. angustifolia Baker N c HW, Gl Orchidaceae 86 = Vanilla phalaenopsis Reichb. f. O Gl 87 ~~ Vanilla planifolia Andrews I F HW Palmae 88 Cocos nucifera L. N A HW, Co 89 Nephrosperma vanhoutteanum (Wendl. ex van-Houtt) Balf. BE O HW 90 = Phoenicophorium borsigianum (K. Koch) Stuntz E A HW 91 Raphia farinifera (Gaertn.) Hylander I R HW Pandanaceae 92 Pandanus balfourti Mart. E F Gl, HW ye Tortoise Legend ‘ NS * Contours Ny & Vegetation plots 100 metres m Marsh ® Buildings Beach Figure 1. Cousin Island: physical, with locations of vegetation plots. COUSIN BY MICHAEL J. HILL', TERENCE M. VEL', KATHRYN J. HOLM’, STEVEN J. PARR? and NIRMAL J. SHAH! GEOLOGY, TOPOGRAPHY AND CLIMATE Cousin is one of the smaller islands of the granitic Seychelles with an area of only about 29 ha. It lies about 2 km from Praslin, the second largest of the central Seychelles islands, and 2.1 km north east of the slightly smaller island of Cousine. The island is dominated by its plateau (Table 1), a flat coastal plain made up of phosphatic sandstones. This rock was formed by the action of seabird guano on loose deposits, largely of marine origin, in the presence of Pisonia litter (Fosberg, 1984). The southern part of the island consists of a granite hill which reaches 58 m. The granite of the hill is similar in quality to that of Praslin Island (Braithwaite, 1984). Along Anse Frégate in the south, there is a conspicuous line of fossil beach-rock (Fosberg, 1970). A granite outcrop, Roche Cannon, of similar granite to the hill, is connected to the north west corner of the island by a natural causeway. The plateau rocks support a thin layer of soil. Fosberg (1984) describes the plateau deposits as a beheaded Jemo soil, except around the marshes where deeper alluvial deposits have accumulated. These deeper soils were used for crop cultivation, and small numbers of fruit trees survive at the base of the hill. Cousin’s beaches surround the island and their sand is highly mobile, shifting between beaches on the east and west sides of the island with the two main seasons of the Seychelles (Frazier and Polunin, 1973). Standing fresh water on the island 1s limited in extent and seasonal. On the plateau at the northern base of the hill there are several freshwater pools. To the south of the hill is a regularly inundated area of land colonised by mangroves. There are several small seasonal streams. The Seychelles islands experience a seasonal humid tropical climate (Walsh, 1984). Historical weather data for Cousin Island are limited and current data are unavailable. A summary of data on rainfall for the period 1970-75 is shown in Table 2. ' Nature Seychelles, PO Box 1310, Mahé, Seychelles. Email: birdlife@seychelles.net 71991 Casa Marcia Crescent, Victoria, British Colombia, Canada. * Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, UK. 50 Table 1. Area of Cousin Island by altitude (calculated from maps published by Directorate of Overseas Survey (UK)/Seychelles Government). Altitude range (m. asl.) Area (ha) Percentage total area 50 - 100 0.6 Zl 10 - 50 5) 19.2 0 - 10 DONS 78.7 Table 2. Cousin Island. Mean monthly rainfall (mm), 1970-1975 (from Shah et al. 1999). Jan Feb 2) Mar Apr May Jun ul Aug Sep: 5 Oct siNovale Dec mmaotal 232 141 143 110 56 30 4] 100 112 205 139 310 1619 HISTORY The island was briefly mentioned by Malavois (1787) who described it as wooded with difficult access (in Fauvel, 1909). In 1821, when the island was surveyed by the Mauritian Government surveyor, it was divided into three sections owned by freed slaves (Diamond, 1975). In the nineteenth and early twentieth centuries, the island had a succession of private owners. At this time mixed agriculture was probably practised and the natural resources of the predator-free island (turtles, seabirds and their eggs) exploited. Coconut plantations were begun on Cousin around 1910. Within 10 years, the natural vegetation of the plateau had been completely replaced by coconuts (den Boer and Geelhoed, 1990). The island was managed for copra production until 1967 when it was purchased by the International Council for Bird Preservation (now BirdLife International) and subsequently managed as a nature reserve, largely to protect the Seychelles warbler Acrocephalus sechellensis, which was then known only from Cousin (Komdeur, 1988). Management from this time allowed the regeneration of semi-natural vegetation dominated by Pisonia grandis (Phillips, 1984). The island was designated a Nature Reserve by the Seychelles Government in 1968, and was designated a Special Reserve in 1969. The Special Reserve designation includes the sublittoral zone to 400 m beyond the high-water mark (Shah ef al. 1999). FLORA AND VEGETATION Flora Ninety-five plant species were recorded on Cousin Island, including three ferns and 92 angiosperms. Of the angiosperms, 47 (51.1%) species are regarded as introduced (Friedmann, 1994) and 32 (34.8%) native. Only one of these native species (Pandanus balfourii) is endemic to the Seychelles although the list also contains an endemic subspecies (Ficus reflexa ssp. seychellensis). 51 The flora of Cousin Island has a similar proportion of introduced species and a smaller number of endemics than the flora of Seychelles as a whole (of the total Seychelles flora, around 54% are introduced and 9% endemic: Procter, 1984). The small number of endemic taxa probably reflects the island’s size; in general, smaller islands in the archipelago have fewer endemic species (Procter, 1984). Of the introduced plants established on Cousin Island, a small number can be regarded as invasive weed species (Carlstrém, 1996a; Fleischmann, 1997). Of these, three are woody plants: casuarina Casuarina equisetifolia (frequent in beach crest vegetation; possibly native), papaya Carica papaya (abundant in plateau woodland) and agati Adenanthera pavonina (occasional in plateau woodland). Other potentially invasive species are the herbs pineapple Ananas comosus and fatak grass Panicum maximum. Both species currently have a limited distribution on the island. The Rangoon creeper Quisqualis indica occurs at one point near the marsh. It has the potential to dominate large areas through vegetative propagation. Several previous workers have produced plant species lists for Cousin Island, most notably Fosberg (1970, 1984). Fosberg recorded 132 species, many of which are still present on the island. Further surveys were carried out by Bathe and Bathe (1982) and Schumacher and Wiithrich (2000). In total, 54 species were identified in previous surveys but not in the current survey (Appendix 1). At least three of these previously recorded taxa are synonyms of other species on the list, and three may never have been present on the island. Many more (especially species of cultivation) are probably now extinct, or are occasionally cultivated. Some species were undoubtedly overlooked; a long-term survey of 1999 recorded 10 species not recorded by this survey (Schumacher and Wiithrich, 2000). If these, and species listed by previous authors which may survive (17 species: mainly herbs and grasses which may have been overlooked) are included, the total current plant species list for Cousin is 122. Vegetation The extents of major vegetation types on Cousin Island are shown in Table 3, and on Map 2. While most of the island was formerly coconut plantation, the plateau and part of the hill is now dominated by native woodland. The hill also has native scrub and large areas of bare rock. In total, 40 vegetation plots were completed, 20 in June and 20 in December, covering 4,000 m° or 1.4% of the island’s surface. Twenty vegetation plots were in plateau woodland covering 2,000 m’ or 1.1% of this habitat type, and 20 were in hill woodland/scrub (excluding areas of bare rock), covering 2,000 m° or 4.7% of this habitat type. A summary of results is shown in Table 4. Hill woodland plots had a relatively low density of trees with sparse shrub and herb layers. The most abundant tree was the native Pisonia grandis (Table 5). Introduced trees made up only a small proportion of the total tree layer (only one or two species, around three percent of stems). The shrub layer of hill plots was species-poor, with only eight species represented, seven of which were native. The most widespread species was Euphorbia pyrifolia (Table 6). Coconut Cocos nucifera was only present in one plot, although in that plot it constituted 38% cover in the herb layer. The herb layer of hill 52 plots had fewer species than plateau plots: only 18 species were recorded, four of them introduced. The only species occurring in more than 10 plots was the fern Nephrolepis ?biserrata, in 17 plots (with a mean coverage of 29.6% in these plots). Plateau woodland plots had a high density of trees, relatively dense shrub layer, and sparse herb layer. The tree layer was more species-rich than that of hill woodland and included several species not present on the hill. Pisonia grandis was again dominant, but introduced species were more prominent due to the abundance of introduced papaya, absent on the hill. The shrub layer of plateau plots was more species-rich than that of hill plots with 15 species represented (three of them introduced). The most widespread species, and that forming the largest part of shrub cover in the plots where it occurred, was Pisonia grandis. Cocos nucifera, Morinda citrifolia and Ochrosia oppositifolia were also widespread in the plateau shrub layer. The herb layer of plateau plots was also species-rich with 20 species, seven or eight of which were introduced. Five species occurred in 10 or more plots: the most widespread and abundant were the liana Canavalia cathartica (in 15 plots, mean cover 14.8%) and the fern Nephrolepis ?biserrata (in 15 plots, mean cover 13.7%). Morinda citrifolia occurred in 12 plots (mean cover 1%), Carica papaya in 11 (mean cover 1%), and Pisonia grandis 10 (mean cover 4.7%). Table 3. Extent of major vegetation types, Cousin Island. Vegetation type Area (ha) Hill Woodland (Pisonia grandis dominant) 1.5 (> 10 m asl) Woodland (figs, other native spp.) 0.4 Scrub (native) 2.4 Bare rock 1.1 Plateau Woodland (Pisonia grandis dominant) hie, (< 10 masl) Woodland (other native spp.) 0.7 Scrub (native) 0.1 Coconuts 0.1 Freshwater marsh 0.2 Mangrove 0.8 Beach crest vegetation (including Casuarina) 1.9 Bare rock 1.5 Grassland/garden 0.1 Table 4. Vegetation plot summary. Habitat Plots Mean Mean Meanshrub Meanherb Openleaf Bare Dead wood altitude trees layer cover layer cover litter rock _— (pieces per Gnlasl) a ehalt (%) (%) cover(%) _(%) lot) Plateau 20 <5 990 41.9 29.9 44.4 21.4 3.8 woodland Hill 20 PD 390 ISO) 29.6 Zhe 47.1 1S woodland = 100 metres Legend: vegetation types Ficus woodland Bare rock Grassland Glacis/native scrub Casuarina — | Beach crest vegetation al Marsh < 4 Mangrove fil) Coconut Figure 2. Cousin Island vegetation. 53 54 Table 5. Cousin Island: tree species recorded Plateau No. stems %stems | No. stems % stems Introduced species Adenanthera pavonina 6 32 Carica papaya 32 16.2 Eucalyptus sp. Native species Euphorbia pyrifolia 2 1.0 Ficus lutea 5 2S Ficus reflexa 2 1.0 Hibiscus tiliaceus 2 1.0 Ochrosia oppositifolia 13 6.5 Pandanus balfourii Phyllanthus pervilleanus ] 0.5 Pisonia grandis 88 44.4 Status unknown Morinda citrifolia 47 23K Total 198 Table 6. Cousin Island: most widespread shrub species. Shrubs occurring in five or more plots shown. Percentage shrub cover is the mean cover for those plots in which the species occurs. No. plots % shrub cover Plateau No. plots = % shrub cover Introduced species Carica papaya 8 333 Native species Cocos nucifera MS) 13.4 Euphorbia pyrifolia 3 6.3 Ficus lutea 7 ell Ficus reflexa 5 2 Ochrosia oppositifolia 13 o3 Phyllanthus pervilleanus 5 4.6 Pisonia grandis IY 14.9 Status unknown Morinda citrifolia 15 7.0 Total 55 Flora And Vegetation: Discussion A vegetation survey of the island was competed by Diamond (1975) before the island had become dominated by Pisonia grandis woodland. At the time, the island (especially the plateau) was still dominated by plantation palms. The hill, largely unsuited for cultivation, was less extensively planted. Following the island’s designation as a Nature Reserve, attempts to replant native vegetation were deemed largely unsuccessful (Diamond, 1975) and a process of natural succession occurred with coconuts removed to prevent the island being overtaken by coconut scrub. Fosberg (1970) predicted that the vegetation would undergo succession until dominated by Pisonia. This change has happened within a period of 30 years, assisted by the repression of coconut regrowth and the removal of mature fruiting palms. If mature palms had been left in place, and coconuts left to germinate, the plateau would probably now be a dense palmetum. Although Pisonia is a relatively fast-growing, short-lived tree with fragile wood, it can form climax vegetation through its ability to layer, and regenerate quickly from fallen stems (Schumacher and Wiithrich, 2000). It is possible that further change may result in areas of Ochrosia-dominated woodland (Fosberg, 1970); other abundant woody species on the plateau are small trees or large shrubs. The flora of Cousin has lost many of the introduced species that were recorded by Fosberg (1984). Of introduced woody species, the most widespread in natural habitats were Carica papaya and Adenanthera pavonina (although a number of other species occur, especially in previously cultivated areas around the marshes). There was evidence for widespread regeneration of both species. Although the most abundant woody exotic on the island, Carica is probably not of major conservation concern: its fruits are eaten by a number of endemic vertebrates including Foudia sechellarum (Collar and Stuart, 1985) and Mabuya spp. (Brooke and Houston, 1983). Individual plants are relatively short-lived and small (the mean height of Carica in the tree layer was 7.4 m compared to 10.7 m for Pisonia), so they are unlikely to shade out other tree species. Mature coconut palms were not found in any of the vegetation plots; large Cocos now have a restricted distribution on the island (mainly around the marsh; see Fig. 2). However, young Cocos plants were relatively widespread and abundant in the shrub layer on the plateau (more restricted on the hill). Management of coconut regrowth remains important. INVERTEBRATES Pitfall Trapping Pitfall trap assemblages were relatively large, compared to those from other islands surveyed (Table 7). Assemblages (excluding ants) were larger in the north west monsoon period than in the dry season dominated by south east trade winds. The high value for hill plots in the SE season is due to extremely high ant numbers trapped in one plot. Ants dominated all pitfall assemblages forming between 57% of the total invertebrate individuals (NW, hill) and 98% of invertebrate individuals (SE, hill). Other 56 than ants, dominant invertebrate groups included Crustacea (including both Isopoda and Amphipoda), Blattodea, Dermaptera and Araneae (Fig. 3). In Hill plots, larger numbers of Crustacea were trapped. Only isopods were collected on the hill; amphipods were abundant but only trapped in plateau plots. Cockroaches (Blattodea) were also abundant in hill plots in both seasons. Plateau woodland sites were dominated by ants which made up 78.6% of the total individuals in pitfall assemblages. The most abundant species was the native Odontomachus troglodytes (41.5% of individuals), followed by ?Cardiocondyla emeryi (35.6% of individuals). The most abundant non-ant species (and the third most abundant species) was an amphipod crustacean which formed 5.0% of individuals. An earwig species (Dermaptera) made up 4.0% of individuals. A total of 73 morphospecies were collected in 20 plots. In hill woodland/scrub, assemblages were similar but less species-rich. A total of 48 taxa were collected in 16 plots. Ants were again dominant, forming 90.0% of the total individuals. Cardiocondyla emeryi was the most abundant species (88.2% of individuals). An isopod crustacean was the second most abundant species (4.9% of individuals). Other species form much smaller proportions of the total assemblage: a cockroach species made up 2.3% of individuals, Odontomachus troglodytes 0.7%. The crazy ant Anoplolepis gracilipes was collected twice. One individual was collected in a hill plot and one in a plateau plot. Table 7. Pitfall assemblages from Cousin Island. Only invertebrates of body length >2 mm included. (Number in parentheses = number of invertebrates excluding ants). Habitat Mean no. individuals per 5 traps SE season NW season Cousin Plateau woodland 58.0 (16.9) 1222912 126) Hill woodland 410.2 (6.7) 62.7 (27.0) Mean for all granitic 61.8 (9.4) 61.1 (16.0) islands Ei Blattodea Dermaptera MG | Diptera KZ | larvae BRR | CiLepidoptera O Crustacea Mean NI per plot Ospider Mothers Hill Plateau Hill Plateau SE NW Figure 3. Composition of pitfall assemblages on Cousin Island, excluding ants. a] Leaf-insect Counts Leaf-insect counts were carried out for six tree and shrub species, five of these in both seasons (Table 8). For four of the species counted in both seasons, invertebrate densities were higher in June. For one species, invertebrate counts were higher in December, during the north west monsoon. As found on some other islands, the highest density of invertebrates was on the shrub Morinda citrifolia. Pisonia grandis also had high invertebrate densities (especially in June). Together, these two species dominate woodland vegetation on the plateau of Cousin. Table 8. Density of invertebrates on foliage, Cousin Island n= no. of leaves counted; NI = number of individual invertebrates. SE season (June) n mean NI mean NI leaf’! m? NW season (December) N mean NI mean NI leaf! m? Species Native species Euphorbia pyrifolia 600 0.070 30.73 Ficus lutea 350 1.040 76.35 Ficus reflexa 400 0.193 57.88 Ochrosia oppositifolia 500 0.114 8.51 Pisonia grandis 1600 0.531 46.02 Status unknown Morinda citrifolia Malaise Trapping Malaise trapping was carried out in hill and plateau woodland habitats, during both seasons. Five Malaise traps (three in plateau plots, two in hill plots) were run in June, and four (two in each habitat) in December 1999 (Table 9). Assemblages were larger in the north west monsoon season (December), than in the south east season. However, there was no consistent difference in catch size between habitats. The major insect order in most seasons was the Diptera. In June, in hill plots, Hemiptera (especially Auchenorrhyncha) dominated assemblages. The majority of taxa collected have yet to be identified to species level. 58 Table 9. Malaise trap assemblages, Cousin. NI = Number of Individuals. SE (June) NW (December) Hill Plateau Hill Plateau No. traps 2 2 2 Mean NI trap’! 699.5 1038.0 2890.5 1875.0 Total NI Diptera 232 4312 ST, Total NI Hemiptera S27) 39 38 Total NI Hymenoptera 216 317) 348 Total NI Lepidoptera esi) 1013 288 Total NI Orthoptera 128 45 19 Total NI Other orders 59 5) 45 Observation A list of species observed or collected in the current survey, and by previous workers, is given in Table 10. Terrestrial invertebrates were collected on both assessment visits; aquatic invertebrates were only collected when there was water in the marsh, in December. At this time, the marsh had standing water with a combined area of about 1,000 m’ and to a depth of up to 50cm. An aquatic light trap operated overnight collected two crustacean species in very large numbers. Discussion: Invertebrates Pitfall assemblages from Cousin Island were relatively large and assemblages on the plateau (excluding ants) were larger than those on the hill: plateau areas are more suitable for Seychelles magpie-robin than hill areas. The presence of the crazy ant Anoplolepis gracilipes in pitfall assemblages, albeit in small numbers, is of concern. This pest species was introduced in Seychelles in the early 1960s (Haines et al., 1994) and has since been spread to many islands including Marianne and Félicité. On Bird Island, especially high concentrations of ants have caused tree death (Hill, in prep.) and the eradication of native reptiles from large parts of the island (Feare, 1999a). Crazy ants were not recorded on Cousin in 1982 (Bathe, 1982b) but their presence has been reported on several occasions, and ants in the vicinity of buildings have been eradicated. It is possible that the species had been present on the island for some time but has not been able to reach the pest proportions found on other islands due to competitive exclusion by other ant species favoured in the semi-natural habitats of Cousin Island. Leaf invertebrate counts were highest for the two tree species that currently dominate Cousin’s woodland (especially plateau woodland). For most tree species (contrary to results for several islands) invertebrate densities were higher in the dry season (June) than in the north west monsoon season (December). 59 Few aquatic invertebrates were collected on Cousin, probably as a result of the seasonality of standing water on the island. No dragonflies were recorded, although six species have been recorded on the island, four breeding (Bathe, 1982c). Species lists have also been produced for Cousin bees (5 species: Bathe, 1982a) and ants (14 species: Bathe 1982b). Table 10. Invertebrates, Cousin Island. Previous records (in notes); 1 = Bathe and Bathe, 1982a; 2 = Miihlenberg 1977; 3 = Bathe and Bathe, 1982b; 4 = Bathe and Bathe, 1982c; 5 = Blackman 1965, in Blackman and Pinhey, 1967. Order Family Species Notes Mollusca Achatinidae Achatina sp. Many empty shells Subulinidae Subulina octona Bruguiere, 1792 ?Opeas sp. Arachnida: Amblypygi Tarantulidae ?Charinus seychellarum Krapelin, 1898 Araneae Tetragnathidae Nephila inaurita (Walckenaer, 1841) Scorpiones Buthidae Isometrus maculatus (de Geer, 1778) Crustacea: Decapoda Coenobitidae Coenobita brevimanus Dana, 1852 Grapsidae Grapsus tenuicrustatus (Herbst, 1783) Ocypodidae Ocypode ceratophthalmus (Pallas, 1772) Ocypode cordimana Desmarest, 1825 Myriapoda: Chilopoda Scolopendridae Scolopendra subspinipes (Leach, 1918) Diplopoda Spirostreptidae Seychelleptus seychellarum (Desjardins, 1834) Spirobolellidae ?Benoitiulus flavicollis Mauries, 1980 Trichopolydesmidae Cylindrodesmus hirsutus (Pocock, 1888) Trigoniulidae Spiromanes ?braueri (Attems, 1900) Spiromanes seychellarum Saussure & Zehntner, 1902 Insecta: Coleoptera Scarabaeidae Oryctes monoceros (Olivier, 1789) Hymenoptera Anthophoridae Ceratina nodosiventris Cockerell 1912 * Recorded 1982! Xylocopa caffra (Linnaeus, 1767) Apidae Apis mellifera adansoni Latreille, 1804 Recorded 1982' and 1999/2000 Formicidae Anoplolepis gracilipes (Smith, 1857) Brachymyrmex cordemoyi Forel 1895 * Camponotus grandidieri Forel, 1886 * Camponotus hova Forel, 1891 Cardiocondyla emeryi Forel, 1881 Leptogenys maxillosa (Smith, 1858) * Monomorium floricola (Jerdon, 1851) * Odontomachus troglodytes Santschi, 1914 ?Pachycondyla melanaria (Emery, 1894) Paratrechina bourbonica (Forel, 1886) * Paratrechina longicornis (Latreille, 1802)* Recorded 1975° Recorded 1982° Recorded 1982° Recorded 1975- Recorded 19757, 1999- 2000 Recorded 1975- Recorded 1975> 60 Table 10 (cont.) Order Family Species Notes Lepidoptera Neuroptera Odonata + extinct? Halictidae Megachilidae Vespidae Hesperiidae Lycaenidae Myrmeleontidae Coenagrionidae Aeshnidae Libellulidae Pheidole megacephala (Fabricius 1793) * Strumigenys rogeri Emery, 1890* Tapinoma melanocephalum (Fabricius, 1/93) Technomyrmex albipes (Smith, 1861) Tetramorium ?bicarinatum (Nylander, 1846) Tetramorium languinosa Mayr, 1870 * Tetramorium simillimum (F. Smith, 1851)* Pachyhalictus mahensis (Cameron) * Megachile seychellensis Cameron, 1907 * Polistes olivaceus (de Geer, 1773) Borbo sp. Leptotes pirithous Linnaeus, 1767 Myrmeleon obscurus Rambur, 1852 Ceriagrion glabrum (Burmeister, 1839)* Hemianax ephippiger (Burmeister, 1839)* Diplocodes trivialis (Rambur, 1842)* Orthetrum stemmale wrightii (Selys, 1869)* Tramea limbata (Selys, 1869)* Zyxomma petiolatum (Rambur, 1842)* e species recorded by previous workers but not observed in current survey Reptiles and Amphibians VERTEBRATES Recorded 1982 Recorded 1982? Recorded 19757 Recorded 1975’, 1982°, 1999-2000 Recorded 1982? Recorded 1982? Recorded 1982! Recorded 1982! Recorded 1980-814 Recorded 1980-814 Recorded 1980-814 Recorded 1965°, 1980- sie Recorded 1980-814 Recorded 1965° Six terrestrial reptiles were observed (Table 11), all native to Seychelles although one (Aldabra tortoise) was introduced in the granitic islands and was first recorded on Cousin in the 1960s (Bour, 1984). Four species of reptile previously recorded on Cousin were not observed in the current survey, the geckos Urocotyledon inexpectata and Gehyra mutilata, the Brahminy blind snake Ramphotyphlops braminus and the freshwater terrapin Pelusios subniger. Three of these (excluding G. mutilata) are rather cryptic, rarely observed species and were probably overlooked. U. inexpectata was recorded once, in 1979 (Shah et al., 1999); its current status is unknown.. The introduced gecko Gehyra mutilata has been observed in houses (Shah ef al., 1999). It is common on larger islands such as Praslin and, if extinct, is likely to reinvade. The blind snake is a widespread introduced species found on many of the islands where agriculture formerly occurred, and probably survives on Cousin. The terrapin was introduced to the island from La Digue in c. 1940 (Bour, 1984). It is rarely observed by island staff but may survive. Two of the native skinks of Cousin Island, Seychelles skink Mabuya sechellensis and Wright’s skink Mabuya wrightii, reach extremely high population densities on 61 Cousin with a biomass of between 96 kg and 184 kg per hectare (Hunter, 1978: Brooke and Houston, 1983). Such high biomass is supported by the seabird colonies of the island. M. wrightii is restricted to islands with seabird colonies although the apparent association may be simply the result of its inability to survive on islands with introduced rats (Cheke, 1984). M. sechellensis, although endemic, is widespread in the granitic islands and the near coralline islands. The large gecko Ailuronyx seychellensis also survives on islands with rat populations, although it is most obvious on rat-free islands, where (as on Cousin) it is diurnal and often found in houses (Cheke, 1984). In addition to the land reptiles, two marine turtle species breed on Cousin Island: green sea turtle Chelonia mydas (L.) and hawksbill Eretmochelys imbricata (L.). Breeding hawksbills were observed in December. October to January is the peak breeding season for hawksbill sea turtles on Cousin (Frazier, 1984). One species of amphibian, an unidentified species of caecilian (possibly Hypogeophis rostratus) has been recorded on Cousin Island (Nussbaum, 1984b), but was not observed during the current survey. Table 11. Reptiles observed on Cousin. Status: E =endemic, I = introduced, N = native (in central Seychelles). Family Species Status Gekkonidae Ailuronyx seychellensis (Dumeril & Bibron, bronze-eyed gecko E 1836) Phelsuina astriata Tornier, 1901 day gecko E Scincidae Mabuya sechellensis (Dumeril & Bibron, 1836) Seychelles skink E Mabuya wrightii (Boulenger) Wright’s skink E Pamelaescincus gardineri Boulenger, 1909 burrowing skink E Testudinidae Geochelone gigantea (Schweigger, 1812) Aldabra giant tortoise I Birds In total, 15 land birds and waders were recorded (Table 12). Five of these were endemic species, three of which are regarded as endangered or vulnerable species in Seychelles (Watson, 1984). For much of the twentieth century, Cousin was the only island on which the Seychelles warbler Acrocephalus sechellensis occurred (Komdeur, 1988). In 1988-90 birds were translocated to Aride and Cousine and further populations established (Komdeur, 1994). The Seychelles magpie-robin Copsychus sechellarum was translocated to Cousin in 1994 and the Cousin population is now the second largest of three island populations (Parr et al., 1999). The Seychelles fody Foudia sechellarum is currently restricted to three islands in the granitic archipelago, with an introduced population surviving on D’ Arros. Cousin probably holds the major population of this species (Collar and Stuart, 1985). Penny (1974) noted that the endemic Seychelles form of the “Madagascar” turtle dove, Streptopelia picturata rostrata, appeared to survive on the island but a survey in 1990 suggested that very few individuals display the characteristics of true S. p. rostrata. Most individuals belonged to an intermediate form showing characteristics of both S. p. 62 rostrata and the introduced Madagascar form S. p. picturata (den Boer and Geelhoed, 1990), suggesting that S. p. rostrata has become effectively extinct through cross- breeding. Two additional resident land bird species are known on Cousin. The black- crowned night heron Nycticorax nycticorax was found to be breeding on the island in 2000 (Anon, 2000), following natural colonisation of the island. There are also occasional records of the introduced barn owl Tyto alba and it seems likely that there is at least one resident bird. On Cousin, where rats are unavailable, barn owls prey on birds, especially fairy terns Gygis alba (Penny, 1975). Other bird species are also taken, suggesting that the presence of the barn owl represents a threat to endemic land birds on the island. In addition to the land birds, Cousin Island supports breeding colonies of seven seabird species. Ten seabird species were observed (Table 13), seven of which breed on the island. Diamond (1975) lists 52 bird species that had been recorded from Cousin Island, including migrants and vagrants not recorded in this survey. Since his list was written, two new resident breeding birds have been added to the fauna of Cousin: Seychelles magpie-robin and black-crowned night heron, and the Seychelles blue pigeon Alectroenas pulcherrima, which only occurred occasionally at the time of Diamond’s list, iS now resident. Table 12. Land birds and waders observed on Cousin. M = migrant species; E = Seychelles endemic species. Species Bubulcus ibis Butorides striatus Gallinula chloropus cattle egret green-backed heron common moorhen Dromus ardeola M Arenaria interpres M crab plover ruddy turnstone Calidris alba M Streptopelia picturata ssp. sanderling turtle dove Geopelia striata barred ground dove Alectroenas pulcherrima E Seychelles blue pigeon Seychelles magpie robin Seychelles warbler Seychelles sunbird common mynah Copsychus sechellarum E Acrocephalus sechellensis E Nectarinia dussumieri E Acridotheres tristis Madagascar fody Seychelles fody Foudia madagascariensis Foudia sechellarum E Notes One observed in mangrove, 14/6/99 One observed near Roche Canon, 7/12/99 Common at main marsh, and in a variety of plateau and hill habitats One individual, December. Regularly observed on beaches and plateau woodland, in small groups, both June and December One group of 5-6 birds observed on beach, June Regularly seen around houses and in woodland, June and December Occasional at houses, and on hill glacis, June and December Nesting close to houses. Flock of 7-10 seen feeding on figs 20/6/99 (observed by Alan Burger) Regularly seen in woodland Very common in woodland Very common in woodland One observed in Casuarina close to research house, 14/6/99 Rarely seen Very common in woodland and around houses, June and December 63 Table 13. Seabirds observed on Cousin Island. Species Notes Puffinus pacificus wedge-tailed shearwater — Breeding birds present (June) Puffinus lherminieri Audubon’s shearwater Breeding birds present (June & December) Phaeton lepturus white-tailed tropicbird Breeding birds present (June & December) Sterna anaethetus bridled tern Breeding birds present (June) Anous stolidus brown noddy Breeding birds present (June) Anous tenuirostris lesser noddy Breeding birds present (June) Gygis alba fairy tern Breeding birds present (June & December) Fregata minor great frigatebird Seen overflying island several times, in both June and December Sterna dougalli roseate tern Seen from beach 23/6/99 (observed by Alan Burger) Sterna fuscata sooty tern Seen from beach 23/6/99 (observed by Alan Burger) Mammals Two mammal species were observed in the course of the survey, the endemic fruit bat Preropus seychellensis and the introduced black-naped hare Lepus nigricollis. During both assessments, Seychelles fruit bats were observed feeding on fruit on Cousin. Most or all appear to roost on Praslin; bats were observed flying over the sea from Praslin to Cousin on the evening of 21st June. Black-naped hares are the only terrestrial mammal on the island. They were seen every day of the survey, usually singly, throughout the island in woodland, scrub and grassy areas. The population of hares was estimated to be between 50 and 100 animals in 1974 (Diamond, 1975). In 1981, the population was estimated as 120-170 individuals (Kirk and Racey, 1992). The effect of the animals on the vegetation of Cousin has not been fully documented. In the 1980s, faecal pellets were dominated by plants that are now rather rare on the plateau (grasses and sedges). Hares may also distribute Boerhavia and Achyranthes, although the former species is also now rare on Cousin in comparison to many other islands. It is also possible that hares reduce the regeneration of Casuarina (Kirk and Racey, 1992). Rats (Rattus spp.), although widespread on other islands of the granitic Seychelles (and introduced soon after human colonisation to many of the islands: Fauvel, 1909), have never been present on Cousin. The absence of rats and cats accounts for the survival here of the Seychelles warbler and large colonies of breeding seabirds. CONSERVATION RECOMMENDATIONS Conservation recommendations have been given in various management plans for the Nature Reserve, including the most recent (Shah er al., 1999). Recommendations generally centre on the preservation of the island’s existing wildlife values, rather than on habitat restoration, as a natural process of rehabilitation has occurred since the island was acquired as a nature reserve. In 30 years, Pisonia forest has replaced coconut plantations and the forest existing today, at least on the plateau, probably resembles the original vegetation of the island (Fosberg, 1970). 64 The major recommendations of management plans concern the need to prevent invasion of alien species currently absent from the island, especially mammals. Vegetation management measures in the most recent management plan are limited to the removal of fallen coconuts and the management of beach-crest vegetation by encouraging native species and removing casuarinas. Additional measures that could be proposed in the light of this report include: 1) Monitoring of crazy ant populations and (if feasible) eradication of this species. Crazy ants are present, but apparently in very small numbers. It is important to monitor populations. The species tends to undergo “boom and bust” demography after introduction to a new area (Haines ef al., 1994) and it can have important conservation implications (Haines et al., 1994; Feare, 1999). 2) Removal of mature coconut palms around marsh. Although probably a native species in the granitic Seychelles (Sauer, 1967), the present abundance of coconuts is a function of planting in the nineteenth and twentieth centuries. On Cousin, coconuts can be regarded as a weed because the regrowth of young palms from fallen nuts produces dense vegetation unsuitable for foraging by Seychelles magpie-robin, which prefers open areas of leaf litter (McCulloch, 1994). Coconut palms are currently controlled by removal of seedling growth and fallen nuts. Both are still abundant near the main area of mature palms surviving on the plateau at the marsh. Here mature palms shade the marsh and prevent the growth of aquatic macrophytes. Removal of most (or all) of these palms would allow more light to reach the seasonal marsh and reduce the need for management of coconut seedling growth. 3) Control/eradication of other invasive introduced species. Few introduced plant species appear invasive in Cousin’s semi-natural habitats. Adenanthera pavonina was rather widespread in vegetation plots and produces many seedlings; it should be removed. The introduced ornamental vine Rangoon creeper Quisqualis indica only occurs in one place near the marsh but is potentially invasive through vegetative propagation and could also be removed. Bamboo Bambusa vulgaris also has the potential for vegetative spread. The species rarely flowers so is unlikely to spread by seed at least one clump could be left in place. Because a number of endangered endemic birds already exist on the small island of Cousin, further translocations of endemic birds to the island are not recommended unless a greater understanding of habitat requirements and compatioility of species can be gained. 65 Appendix 1. Plant species recorded from Cousin Island (excluding seagrasses) Plants recorded in the current survey (mainly sight records) are numbered. For plants only recorded by previous authors, not in current survey, date of most recent record is given (see below). Taxonomy of dicotyledons as given by Friedmann (1994). Of Monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>1000 individuals observed); C = Common (100 - 1000 individuals observed); F = Frequent (10 - 100 individuals observed); Occasional (3 - 10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: Cu = Cultivation/settlement area; PG = Plateau grassland; PW = Plateau woodland; HW = Hill Woodland; Gl = Glacis; BC = Beach Crest; Ma = Marsh; Mg = Mangrove. Historical records (in Notes): 1= Fosberg 1970; 2 = Bathe & Bathe 1982; 3 = Robertson 1989, 4 = Schumacher & Wiithrich 2000. Species Status _Abund. _ Habitats Notes PTERIDOPHYTA Adiantaceae 1 Acrostichum aureum L. N R Mg Davalliaceae 2 Nephrolepis ?biserrata (Sw.) Schott N A PW Nephrolepis multiflora (Roxb.) Jarrett N - - Recorded 1970, 1982". = N. biserrata? Polypodiaceae 3 Phymatosorus scolopendria (Burm. f.) N 2 HW, PW ANGIOSPERMAE: Dicotyledons Acanthaceae 4 Asystasia sp B. (sensu Friedmann) 21 A PGAGL Asystasia gangetica (L.) T. Anders. 21 - - Recorded 1970, 1982, 1999'?* =A. sp. B? Justicia gendarussa ut - - Recorded 1970', not 1982’. Extinct on Cousin Aizoaceae 5 Glinus oppositifolius (L.) A. DC. 2N In PW, Cu Amaranthaceae 6 Achyranthes aspera L. It A PW 7 Amaranthus dubius Mart. ex Thell. I ¢€ PW, Cu 8 Lagrezia cf. madagascariensis (Poir.) Moq. N ? BC Anacardiaceae Mangifera indica L. I . S Recorded 1970, 1982'** Extinct on Cousin Spondias cytherea Sonn. It - - Recorded 1970', not 1982 *. Extinct on Cousin Annonaceae Annona muricata L. I - . Recorded 1970, 1982, 1999 ae ne 9 Annona reticulata L. I R Cu 10 Annona squamosa L. I O Cu ; ee 66 Species Apocynaceae it Catharanthus roseus (L.) G. Don. 12. = Ochrosia oppositifolia (L.) K. Schum. 13. Plumeria rubra L. Avicenniaceae 14 = Avicennia marina (Forssk.) Vierh. Boraginaceae it) Cordia subcordata Lam. 16 = Heliotropium indicum L. Tournefortia argentea L. f. Caesalpiniaceae 17. ~~ Caesalpinia bonduc (L.) Roxb. 18 Senna occidentalis (L.) Link Capparidaceae 19 Cleome viscosa L. Caricaceae 20 = Carica papaya L. Casuarinaceae 7a) Casuarina equisetifolia J. R. & G. Foster Combretaceae 22 Quisqualis indica L. 23 Terminalia catappa L. Compositae Synedrella nodiflora (L.) Gaertn. 24 Vernonia cinerea (L.) Less. Convulvulaceae 25. Ipomoea macrantha Jacq. 26 = Ipomoea pes-caprae (L.) R. Br. 27 Ipomoea venosa (Destr.) Crassulaceae 28 Kalanchoe pinnata (Lam.) Pers. Cucurbitaceae Cucumis sp. Cucurbita moschata (Lam.) Poir. Momordica charantia L. Trichosanthes cucumerina L. Euphorbiaceae 29 ~~ Acalypha indica L. Euphorbia hirta L. Euphorbia prostrata L. 30 = Euphorbia pyrifolia Lam. 31 = Euphorbia thymifolia L. Euphorbia tirucalli Manihot esculenta Crantz Pedilanthus tithymaloides (L.) Poit. Status HZ Li Md Za Ze ZL, Thy OL HO Abund. v2) Habitats HW, Cu PW Cu Mg Notes Recorded 1970!, 19827. Extinct on Cousin Recorded 1970!, 1982? Recorded 1970', not 1982. Extinct on Cousin Recorded 1970', not 19827. Extinct on Cousin Recorded 1970', not 19827. Extinct on Cousin Recorded 1970’, not 19827. Extinct on Cousin Recorded 1970, 1982!” Recorded 1970! Recorded 1982’, extinct on Cousin Recorded 1970, 1982!**, extinct on Cousin Recorded 19994 67 Species Status Abund. Habitats Notes Phyllanthus acidus (L.) Skeels I - - Recorded 1970, 1982°°°. Extinct on Cousin 32. ~~ Phyllanthus amarus Schumach. et Thonn. I O PW 33. ~~ Phyllanthus pervilleanus (Baillon) Mull. N (C PW Arg. Phyllanthus tenellus Roxb. I : = Recorded 1999* 34. ~——- Ricinus communis L. I FE PW Goodeniaceae 35. = Scaevola sericea Vahl. N € BC Guttiferae 36 = Calophyllum inophyllum L. N R PW, HW Labiatae 37. ~~ Plectranthus amboinicus (Lour.) Spreng. 21 O PW, PG Lauraceae Persea americana Mill. I - - Recorded 1970', 1982°. Extinct on Cousin? Lecythidaceae 38 — Barringtonia asiatica (L.) Kurtz N O BC Malvaceae 39 ~=— Abutilon indicum (L.) Sweet 7a R PW, Cu 40 Gossypium hirsutum L. I Je PW Hibiscus surattensis L. I - - Recorded 1982’. Probably extinct on Cousin 41 Hibiscus tiliaceus L. N F BC Malachra capitata (L.) L. 2 - Recorded 1970’. Not in Seychelles? Sida acuta Burm. f. I - - Recorded 1970! 42 Sida cordifolia L. 2N F Gl, HW Sida stipulata Cav. mt : : Recorded 1989? 43. = Thespesia populnea (L.) Soland. ex Correa O BC Mimosaceae 44 — Adenanthera pavonina L. I O HW Moraceae Artocarpus altilis(Parkins.) Fosb. I - - Recorded 1970', not 1982”. Extinct on Cousin Ficus benghalensis L. I - - Recorded 1999". = F. rubra? 45 Ficus lutea Vahl. N € HW, PW 46 Ficus reflexa Thunb. seychellensis (Baker) E (ss) R HW Berg 47 — Ficus rubra Vahl. N R PW Moringaceae 48 Moringa oleifera Lam. I R Cu Myrtaceae 49 = Eucalyptus camaldulensis Dehnh. It O HW : Syzygium samarangense (Bl.) Merr & Perr. I . - Recorded 1970', 1982>. Extinct on Cousin Nyctaginaceae 50. ~~ Boerhavia repens L. 2N C PG 51 = Mirabilis jalapa L. I O Cu 52 Pisonia grandis R. Br. N A PW 68 Verbenaceae Species Status Abund. — Habitats Notes Onagraceae 58 Ludwigia octovalvis (Jacquin) Raven 21 O Ma Oxalidaceae 54 = Averrhoa bilimbi L. I R Cu Papilionaceae 55 Canavalia cathartica Thouars N A PW 56 — Gliricidia sepium (Jacq.) Walp. I R PW Sesbania bispinosa (Jacq.) W. F. Wight I - - Recorded 1970!, 19827. = §. cannabina? Vigna unguiculata (L.) Walp. I - - Recorded 1970', not 1982”. Extinct on Cousin Se Sesbania cannabina (Retz.) Poir. I O Ma Passifloraceae 58 — Passiflora foetida L. I F HW Passiflora suberosa L. I - - Recorded 1970', 1982” Piperaceae 59 Peperomia pellucida (L.) H. B. K. I A PW Polygonaceae Polygonum senegalense Meisn. 2N - - Recorded 1970', 19827. Portulacaceae 60 ~~ Portulaca oleracea L. N O Gl Rhizophoraceae 61 Rhizophora mucronata Lam. N R Mg Rubiaceae 62 Coffeasp. I O Cu 63 Guettarda speciosa L. N O BC Hedyotis corymbosa (L.) Lam. 21 - - Recorded 1970! 64 Morinda citrifolia L. 21 (S PW, HW Rutaceae Clausena anisata (Willd) Hook f. I Recorded 1970', 1982°. = Murraya koenigii? 65 — Citrus sp. I O Cu 66 Murraya koenigii (L.) Spreng.. I O PW Solanaceae 67 = Capsicum frutescens L. I O Cu 68 Datura metel L I F PG Nicotiana tabacum L. I - - Recorded 1982’, Probably extinct on Cousin 69 Solanum americanum Mill. ] O Ma 70 = Solanum lycopersicum L. I R Cu Solanum melongena L I - - Recorded 1970’, not 1982, 1999’*. Cultivated occasionally Surianaceae 71 Suriana maritima L. N O BC Turneraceae 72 ~~ Turnera angustifolia Miller I O PW Umbelliferae Centella asiatica (L.) Urb. 21 Recorded 1970!, not 19827. 73 Stachytarpheta jamaicensis (L.) Vahl. I Cc PW, PG Species Status Abund. Habitats Notes ANGIOSPERMAE: Monotyledons Agavaceae Furcraea foetida (L.) Haw. Amaryllidaceae 74 Crinum asiaticum L. 75 Hymenocallis littoralis (Jacq) Salisb. 76 = Scadoxus multiflorus (Martyn.) Raf. Araceae Ty Alocasia macrorrhiza (L.) G. Don. Colocasia esculenta (L.) Schott Bromeliaceae 78 Ananas comosus (1.) Merr. Cannaceae 79 Canna hybrids Commelinaceae 80 Commelina diffusa Burm f. Cyperaceae 81 Bulbostylis barbata (Rottb.) C.B.Cl. Cyperus alopecuroides Rottb. 82 Fimbristylis complanata (Retz.) Link 83. = Fimbristylis cymosa R. Br. 84 ~Fimbristylis sp. (glacis sedge) Kyllinga monocephala Rottb. 85. Kyllinga polyphylla Willd. Ex Kunth Mariscus dubius (Rottb) Fischer 86 Mariscus ligularis (L.) Urb. 87 Pycreus polystachyos (Rottb.) P. Beauv. Dioscoriaceae Dioscorea alata L. Gramineae 88 Bambusa vulgaris Schrad. Ex Wendl var. aureo-variegata Brachiaria subquadripara (Trin.) Hitche. Cenchrus echinatus L. Dactyloctenium ctenoides (Steud.) Bosser or D. aegypticum (L.) Willd. Digitaria horizontalis Willd. Digitaria radicosa (Presl.) Miq. Digitaria setigera Roth. Eleusine indica (L.) Gaertn. Enteropogon sechellensis (Baker) Dur & Schinz — 21 1 ~~ WFAA Y.Y~ ZI) t23) © (o) Mar 69 5 Recorded 1970', 1982”. Probably extinct on Cousin Recorded 1970’, 1982°. Probably extinct on Cousin Recorded 1970!, not 1982? Recorded 1970!, 19827 Recorded 1970', 1999* Recorded 1976!, not 1982°. Extinct on Cousin Recorded 1970’, not 1982° Recorded 1970', 1982°. Probably extinct on Cousin Recorded 1970’, 1999* Recorded 1970', 1999° Recorded 1970', not 1982° Recorded 1970', not 19827 Recorded 1970', 1982° Recorded 1970, 1982, 1999 * >" 70 Species Status Abund. — Habitats Notes Eragrostis tenella (L.) Beauv. q ; 3 Recorded 1970', 1999* Eragrostis subaequiglumis Renvoize z - - Recorded 1970’, not 1982? 89 Panicum brevifolium L. N A PW, PG 90 ~=Panicum maximum L. q R Mar 91 Sporobolus virginicus (L.) Kunth. N A BC 92. = Stenotaphrum dimidiatum (L.) Brogn. N A PG Stenotaphrum micranthum (Desy.) Hubb. ? = = Recorded 1970, 1982, 1999 1 >* Lemnaceae Lemna sp. z - - Recorded 1970'; occasional outbreaks in marsh Musaceae 93. Musa ?sapientum L. | Ig Cu Palmae 94 Cocos nucifera L. N F PW, HW Pandanaceae 95 ~~ Pandanus balfourii Mart. ig, € Gl, HW 71 . CURIKASE it —_7 a z wv = iukns sat sre Wipes. tin UE BTR é a ae wee | sO Ais vi 1 CHT 4 Pit ui Mee oan Lis i ee a i i as ae st ee a A iy ; \ 7 Cie Wa oes af 1) gate ie = pa Saat ike oowr', Ty oS, he fh ; ‘ med ey nee cnt gE La PICT Wri ma is oat hea lle // ital te Soeote este ti me 2. = OF Dae Fs. 5 jal. et mio! romans Af Lire a wt oe onaa he ie) ‘ a eng - : aie che ai Cera Re ag ee ae hin a ls wy Sony tp # ici he Fd Pine pop a pies et 4 | Mert TA: ai? Fu: saint K gai ae ve i BAeOES 7 Seth a eis Wan? es sh) Yheneal: I Nihen ete ay avr uc f z Oe. Poe er > | Pat be, stra), Huis La = eile Laon te ji jean ie ¥ 7 al 4, aecee 8 i } Sa #, toh (Leper o is - p PO | | h. {hl ‘ peaiue * ‘ ‘pe 7 7 a : _ 2 : =? : ' A v Gyeeayly 1 itt ‘le = 14 3 Sera? - Te. tl oo FY if : it | j vi “a Wii =f : ) . as : ; u * nfs ; hed it elt _ © i - OF Wal are a ea ee Feat, ped) TO 5 Bay ig mall A alg Uist hSHY al Phen | Pisehrerinig punptulcns iy geal Tagan Sm, mee rsvent valor: ai ; Sn ee ee eee Seat ea a Oe Pee ee ee ee Se Be ier event’ eydied Pa iF if fw yillh-@0 ii) S166; | be dans fim / ie Ni ee, © 00 Ld oa [ ity “ le a Liyglet sepa pe rig tec ered “at ba) bi igtay aby Ee MLD Thi is agi ‘+. | Pe mol stile ven), eae fr in wrineen Lanci)s Pods Lh. uae " = u a | DPR CAMS 0) Conite-aest unio}, aie! agine «if ips Shy é eas tobi 5 AA) ATP A> iui h Bev ice taldhG usp a latte bien amos miral) 4rwes is bic vi ’ eee yonice, ful Verreund Wy easly Petliawiar wekony, wwe Be ative ciicveias wink tide aromatic whakesity) and WIE Oo) ule ¢ aol vt piadousy, There bits Liwéyr Toodads aah 4 7 an i ih Seveleiles Mad aad, PAY (cee. OSESCCMAE ial tai Leal i. LD t vv yell Why i np Gwithuy daik, eric toy Chiru, « meoilil Er, preili ifs taal thes 3 in eeeeie Patri, ti ths al dary dk, - mh 79 400, Laan ital Muiiel Ainhwiiadl ie >a S Wipes ¢) lap Lore iy rr Alig hoe Aine rT imple: Fit sialiad ihe agi ited ial = Anse Badamier Legend s Contours ® Vegetation plots m Marsh 8 Building “ Beach — Main paths Coastal plateau areas 500 metres Figure 1. Curieuse Island: physical, with locations of vegetation plots. CURIEUSE BY MICHAEL J. HILL', TERENCE M. VEL', STEVEN J. PARR’ and NIRMAL J. SHAH ' GEOLOGY, TOPOGRAPHY AND CLIMATE OF CURIEUSE Curieuse has an area of 286 ha and is the fifth largest of the granitic Seychelles Islands. It is situated little over 1 km from Praslin, the second largest of the islands. At its highest point (Curieuse Peak), it reaches 172 m above sea level. The island consists of two ranges of high ground enclosing a shallow bay (Baie La Raie). Most of the land is sloping ground between 10 and 100 m above sea level (Table 1). The periphery of the island has low-lying coastal areas. There are four main areas of low-lying ground: 1. North (Anse Badamier) 2. Centre-east plateau (around National Park HQ) 3. Central (Baie La Raie mangrove, partially inundated) 4. South (Leper colonies) Geologically, the island is similar to the nearby island of Praslin. The central hills are made up of reddish-grey granite (Braithwaite, 1984). Surrounding lowland areas consist of weathering products of granite, together with more recent calcareous deposits. The soils of Curieuse are mainly lateritic red earths. On the central range of hills, these have been severely eroded (Piggott, 1968), reduced to bare sub-soil and quartz gravel (Baker, 1963). In some flatter areas (for example, the northern plain) these soils have been less eroded. Some areas of the hill have river valley soils. The soils of the coastal lowlands include red earths (northern plain), marsh and mangrove deposits (central mangrove area, parts of centre-east plateau), and soils of the Shioya series (parts of centre-east plateau, south) (D.O.S., 1966). The island has a large number of marsh areas in the coastal lowlands, most with a marine influence, but there are at least two freshwater wetlands, one at the Doctor’s House (at the eastern end of the leprosarium plateau) and one at the western end of the leprosarium plateau. There are five permanent freshwater streams (IUCN, 1993). The Seychelles islands experience a seasonal humid tropical climate (Walsh, 1984). While no weather data exist for Curieuse, it could be predicted that the climate of the island follows a similar pattern to that of nearby Praslin. Praslin is one of the driest of the large granitic islands with mean annual rainfall of 1,842.8 mm for the periods 1946- 58 and 1977-99 (records from Praslin Grand Anse and Airstrip; unpublished data, National Meteorological Services, Seychelles). ' Nature Seychelles, PO Box 1310, Mahé, Seychelles. Email: birdlife@seychelles.net * Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, UK. 74 Table 1. Area of Curieuse by altitude (calculated from maps published by Directorate of Overseas Survey (UK)/Seychelles Government) Altitude range (m. asl.) Area (ha) Percentage total area >150 2 0.7 100 — 150 3) 11.1 50 — 100 67 23.4 10-50 11] 38.8 0-10 74 25.9 HISTORY Curieuse was first named Ile Rouge (after its exposed red earth soils) but its name was changed to that of one of the vessels of the Marion Dufresne expedition of 1768 (prior to settlement of the Seychelles). The same expedition noted little timber on the island, and very few land tortoises (this population later became extinct). Both coconut and Coco-de-Mer Lodoicea maldivica were recorded (Lionnet, 1984). Malavois (1787) recorded that the hill was covered with Coco-de-Mer (in Fauvel, 1909). In October 1817, the island was leased, but it reverted to the control of the colonial government in 1827. A leper colony was established in 1829 for lepers from Mauritius and Seychelles, and 78 people were housed there by 1830 (McAteer, 2001). Lepers were later joined by old and infirm paupers, but by the late 1860s the colony was dwindling. When Edward Newton visited in 1866, there were only three lepers and “a few old decrepit paupers” remaining (Newton, 1867). The settlement was not closed until 1900, when the few remaining lepers and paupers were moved to new facilities on Round Island, Praslin, and Curieuse was commercially leased again. Coconut plantations were established, production reaching 300,000 nuts per year in 1930 (Anon, n.d.). Vanilla was introduced as a commercial crop in the early twentieth century; production ceased in the 1930s (IUCN, 1993). In 1909-10, a 500 m wall was constructed across Baie La Raie, enclosing the bay which was used for rearing sea turtles for meat. However, the project failed in 1914 when most of the turtles died of disease (Anon, n.d.). In 1937, the government regained control of the island and reopened the leper colony to replace overcrowded facilities on Round Island, Praslin, and Round Island, Mahé (McAteer, 2001). The colony was abandoned in 1965 and the island and 1,370 ha of the surrounding seas were declared a Marine National Park in 1979 (IUCN, 1993). The island is still managed by the Seychelles Marine Parks Authority. The population is small (around 10 people). A large number of tourists make day visits from Praslin. In July 2000, a project of rat and cat eradication was undertaken on Curieuse, to eliminate alien mammals and enhance the conservation value of the island. Aerial application of pelleted bait was used for rats, and poisoning/trapping for cats. ie FLORA AND VEGETATION Flora A total of 242 plant species was recorded on Curieuse, including 11 ferns, one gymnosperm (introduced) and 230 angiosperms (Appendix 1). Of the angiosperms, 131 (57.0%) species are regarded as introduced (Friedmann, 1994) and 81 (35.2%) native. Of the native plants, 23 taxa are endemic to the Seychelles (10.0% of the total flora). At least 43 species of introduced angiosperm (18.7% of the flora) recorded on Curieuse were restricted to gardens around houses and were not found away from cultivation. Most would probably become extinct were cultivation to cease. The proportions of the total flora made up of introduced species and Seychelles endemics were similar to those for the Seychelles as a whole (of the total Seychelles flora, around 54% is introduced and 9% endemic; Procter, 1984). Compared to the flora of smaller islands, Curieuse is relatively rich in endemic plants. Several endemic species are abundant on Curieuse, notably the Coco-de-Mer palm Lodoicea maldivica; Curieuse and Praslin have the only natural populations of the species although planted specimens exist on many other islands (Procter, 1974). In addition, some of the endemic species recorded by previous observers but not in the current survey may still survive on the island (see Appendix 1). Two are known to be extinct there: wild vanilla Vanilla phalaenopsis has not been recorded on the island since the nineteenth century, and the parasitic shrub Bakerella clavata ssp. sechellensis is apparently completely extinct (Carlstr6m, 1996a). Ten species recorded by previous observers may still survive on the island, bringing the total number of plants on the island to 252, with 25 Seychelles endemics. Of the introduced plants established on Curieuse, 15 are invasive weedy species. Several of the woody weeds which are most invasive on the smaller islands of Seychelles are present, including cocoplum Chrysobalanus icaco and cinnamon Cinnamomum verum, both of which are abundant. Coconuts Cocos nucifera were not widely planted on the island and, although abundant in the north of the island, they are less common elsewhere; Curieuse has far fewer coconuts than most other small islands in Seychelles. 76 pli lGe Zia nn Ta WO NO re ue | ! i! \ Wy Wel 500 metres Figure 2. Curieuse Island: vegetation Vegetation Legend:vegetation types Bare rock/glacis vegetation | Cocoplum scrub at Mixed scrub, mainly native Scaevola scrub Sparse hill scrub/red earth Coconut Takamaka woodland Mixed woodland Grassland/garden Marsh The extents of major vegetation types on Curieuse are shown in Table 2 and Figure 2. Curieuse has a wide range of vegetation types and several were not studied in detail. Upland areas of Curieuse are dominated by scrublands that have a variety of endemic species together with one abundant introduced species, cocoplum Chrysobalanus icaco. There are some areas of open rock, and the plateaux have wetland vegetation including mangrove and freshwater marsh. The vegetation survey concentrated on areas of greatest value for endemic bird conservation: the woodland and scrub of plateaux and low hills. WI Table 2. Extent of major vegetation types, Curieuse Island Hill Woodland (predominantly native) (©10 masl.) | Woodland (mixed) Scrub (native spp.) 85.8 Scrub (mixed) WE Scrub (Introduced: predominantly De)| Chrysobalanus) Bare rock 4.9 Plateau Woodland (predominantly native) Py) (<10 masl.) | Woodland (mixed) 6.8 Coconut with regeneration 3.4 Scrub (native spp.) 0.7 Scrub (mixed) 8.8 Scrub (Introduced: predominantly 1.4 Chrysobalanus) Mangrove 4.8 Freshwater marsh 0.7 Beach crest vegetation 4.7 Grassland/garden Bare rock Twenty-five plots were carried out in plateau woodland with a combined area of 2,500 m? (approximately 0.7% of the total area of this vegetation type), and 15 in low hill woodland covering 1,500 m’ or 0.3% of the total area of the habitat. A summary of results is shown in Table 3. Table 3. Curieuse vegetation plot summary Habitat Plots Mean Mean Meanshrub Meanherb Openleaf Bare Dead wood altitude _ trees layer cover layer cover litter rock — (pieces per m asl ha’! %) %) cover (%) %) lot) Plateau 25 <5 744 53.0 42.6 50.0 92 1.3 Hill 15 pA 653 46.0 34.0 41.0 26.6 Hel Plateau plots had a relatively high density of trees and a relatively complete canopy (mean canopy cover = 72%). At ground level, vegetation cover was less than 50% and there was a high proportion of open leaf litter. The tree layer was dominated by a native species, takamaka Calophyllum inophyllum (127 trees, 68% of total trees), although the introduced cinnamon Cinnamomum verum was also abundant (31 trees, 17% of total trees). The shrub layer was dominated by the invasive introduced shrub Chrysobalanus icaco, which was present in 18 of 25 plots and covered 25% of the shrub layer in plots where it occurred. Other widespread species of the shrub layer included cinnamon (in 17 plots, forming on average 14.2% cover), Phoenicophorium borsigianum (in 11 plots, mean 9.1% cover) and takamaka (10 plots, mean 2.6% cover). Plots in low hill woodland had a lower density of stems and a less complete canopy (mean canopy cover=62%). Vegetation of the herb layer was less dense than that in plateau plots, but a larger proportion of the ground was outcrops of bare rock. The tree layer contained less natives than that in plateau woodland; 30.6% of stems were 78 introduced species. However, the most abundant single species was takamaka (28 trees, 28.6% of total trees). Cinnamon was again the second most abundant tree species (17 trees, 17.3% of total trees). Tree species diversity was higher in hill plots than in plateau plots, and the hill woodland contained a number of endemic shrub species including Paragenipa wrightii, Erythroxlum sechellarum and Syzygium wrightii. The shrub layer of low hill woodland was again dominated by Chrysobalanus icaco, found in 14 of 15 plots, with a mean cover of 23.6%. Phoenicophorium borsigianum was as widespread as Chrysobalanus, but contributed less to the shrub cover within plots where it occurred (mean cover was 13.9%). Canthium bibracteatum occurred in 13 of 15 plots, with mean cover of 7.8%. Cinnamon was found in 11 of 15 plots forming 11.5% cover in those plots in which it occurred. The woodland of plateaux and low hills showed great similarity. In both cases, most of the trees present belonged to native species. The presence of native and endemic shrubs in hill woodland indicated that high woodland vegetation appeared to be advancing up-slope into areas previously occupied by native scrub. In early 2000, several Calophyllum trees on the eastern plateau were suffering from symptoms of takamaka wilt disease caused by the fungus Leptographium (Verticillium) calophylli (Ivory et al., 1996: Wainhouse et al, 1998). This disease has caused extensive death of Calophyllum trees on several other islands including North Island and Mahé and could threaten all high forest on Curieuse, which 1s dominated by this species. INVERTEBRATES Pitfall Trapping Pitfall trap assemblages were smaller than average for granitic islands (Table 4); in part, this reflects the lower abundance of ants on Curieuse compared to some other islands, notably those infested with crazy ant Anoplolepis gracilipes such as Marianne and Félicité In fact, plateau sites were rather rich in invertebrates other than ants. In both habitats, invertebrate assemblages were larger during the north west monsoon season, and on the plateau. Lowest invertebrate counts came from hill woodland in the dry south east season. The composition of assemblages also differed between the plateau and hill woodland, although both were dominated by ants (Hymenoptera: Formicidae). Ants formed a larger proportion of the total assemblage in hill woodland than in plateau woodland sites (Fig. 3). Plateau woodland contained greater numbers of earwigs (Dermaptera), beetles (Coleoptera) and woodlice (Crustacea: Isopoda). Woodlice were absent in hill plots. In both hill and plateau woodland, the most abundant invertebrate was the ant Odontomachus troglodytes, which formed 39.1% of all individuals in the plateau woodland and 41.3% of all individuals in hill woodland. In hill woodland, the four most commonly trapped species were all ants. The most abundant invertebrate other than ants was an earwig (4.9% of individual invertebrates belonged to this species). In plateau plots, the two most abundant species were ants, and the third was an earwig (making up 72 8.3% of individuals). Cockroaches (a favoured food item of magpie-robins) were found on both hill and plateau; only two individuals (0.5% of total individuals) were trapped on the hill, while 14 (1.4% of total individuals) were trapped in plateau plots. Table 4. Pitfall assemblages from Curieuse. Only invertebrates of body length >2 mm included. (Number in parentheses = number of invertebrates excluding ants). Habitat Mean no. individuals per 5 traps SE season NW season Curieuse Plateau woodland 38.4 (10.7) 42.1 (22.5) Low hill woodland 17.0 (1.0) 32116) Mean for all granitic islands 61.8 (9.4) 61.1 (16.0) mean NI per plot 45 | 40 1 an Waris =z aan 5 35 + —— - . — H Blattodea others | Crustacea QO Coleoptera | fA Dermaptera | Plateau Figure 3. Total pitfall assemblages from Curieuse. Leaf-insect Counts Leaf-insect counts were carried out for 11 tree and shrub species, eight of these in both seasons (Table 5). In both seasons, the highest densities of invertebrates (both in terms of individuals per leaf and individuals per square metre of leaf) were on native plant species. Terminalia catappa and Paragenipa wrightii had particularly high invertebrate densities. However, the introduced Cinnamomum verum also had high invertebrate counts. Most invertebrates on cinnamon were soft bugs (Hemiptera: Sternorrhyncha) or ants (together these groups comprised 94% of invertebrates on cinnamon in August, 88% in January). In general, mangrove species (Avicennia marina and Rhizophora mucronata) had a low density of invertebrates but that for 4. marina in August was particularly high. For five species, leaf counts were higher in January than in August. Three species had higher leaf counts in January. 80 Table 5. Density of invertebrates on foliage, Curieuse. n=no. of leaves counted; NI = number of individual invertebrates. SE season (August N mean NI mean NI leaf! m” NW season (Janua n mean NI mean NI leaf! i Species Introduced species Anacardium occidentale 100 0.11 20.73 Chrysobalanus icaco 800 0.04 11.58 Cinnamomum verum 960 0.22 34.03 Mean value: introduced 0.14 23.66 Native species Avicennia marina 1099 0.02 9.68 Calophyllum inophyllum 750 0.27 33.94 Canthium bibracteatum 1010 0.08 27.82 Hibiscus tiliaceus 0 Memecylon elaeagni 300 0.06 43.65 Paragenipa wrightii 350 1.08 168.11 Rhizophora mucronata 1000 0.12 15221 Terminalia catappa Mean value: native Malaise Trapping Malaise trapping was carried out in plateau and hill woodland habitats, during both seasons (Table 6). Invertebrate assemblages were greater in January (wet season) than in August (dry season). Assemblages were larger in hill woodland than plateau woodland, probably due to the greater air movement in hill plots where trees are more well-spaced, and herb and shrub layers less dense. The most abundant invertebrates in traps were the Diptera, Lepidoptera and Hymenoptera (wasps and ants); the relative importance of these groups varied between habitats and seasons. The majority of taxa collected have yet to be identified to species level. Table 6. Malaise trap assemblages, Curieuse. NI = number of individuals. SE (August) Hill Plateau NW (January) Hill Plateau No. traps 3 3) Mean NI trap’! 325 262 Mean NI Diptera 159.0 126.7 Mean NI Hymenoptera DO)3) 34.0 Mean NI Lepidoptera 55.0 69.3 Observation Many of the invertebrates observed were introduced or cosmopolitan species (Table 7). However, given the number of endemic plants present on the island, Curieuse probably also supports a number of endemic invertebrates. A more complete survey would be necessary to identify endemic taxa; microhabitats that could harbour endemic insects, not collected in the current survey, include the leaf bases of endemic palms and Pandanus species. Seventy-five species of insect in Seychelles are associated with the leaf bases of native palms and Pandanus, and half the beetle fauna of Praslin are associated with Lodoicea (Stoddart, 1984). Curieuse probably shares many or most of these species. While many of the marshes of the plateaux showed a marine influence, that by the Doctor’s House was entirely fresh and appeared permanently wet. Several species of Odonata were observed around this pool and collections in January included several species of water beetle, water bugs (Gerridae and Veliidae), ostracods and tadpoles of the Mascarene frog Ptychadaena mascareniensis. This marsh area and surrounding takamaka woodland was surveyed by Stevenson ef al. (1997) who recommended it as a potential site for black paradise flycatchers on Curieuse. Table 7. Invertebrates observed and collected, Curieuse. Order Family Species Notes Arachnida: Araneae Tetragnathidae Nephila inaurita (Walckenaer, 1841) Crustacea: Decapoda Coenobitidae Coenobita brevimanus Dana, 1852 Land hermit crab Coenobita sp. 2 Mangrove hermit crab Gecarcinidae Cardisoma carnifex (Herbst, 1784) In mangrove Grapsidae Grapsus tenuicrustatus (Herbst, 1783) On coastal rocks Neosarmatium ?meinerti (De Man, 1887) In mangrove Ocypodidae Ocypode ceratophthalmus (Pallas, 1772) | Beach ghost crab Ocypode cordimana Desmarest, 1825 Beach crest ghost crab Palaemonidae Macrobrachium sp. Crayfish; in stream above leprosarium plateau Mollusca Achatinidae Achatina fulica (Bowditch, 1822) In pitfall traps Achatina ?panthera Ferrusac, 1822 In pitfall traps Cyclophoridae Cyathopoma blanfordi Adams, 1868 In pitfall traps Littorinidae Littoraria ?scabra (L., 1758) Mangrove periwinkle Subulinidae Subulina octona Bruguiére, 1792 In pitfall traps Myriapoda: Chilopoda Scolopendridae Scolopendra subspinipes (Leach, 1918) Diplopoda Paradoxosomatidae Oxidus (Orthomorpha) gracilis (K. In pitfall traps Spirostreptidae Trigoniulidae Koch, 1847) Seychelleptus seychellarum (Desjardins, 1834) Spiromanes ?braueri (Attems, 1900) Spiromanes seychellarum Saussure & Zehntner, 1902 Giant millipede In pitfall traps In pitfall traps 82 Table 7 (cont.) Order Family Species Notes Insecta: Coleoptera Curculionidae Cratopus sp. Dytiscidae Sp. Indet Scarabaeidae Oryctes monoceros (Olivier, 1789) Perissosoma aenescens Waterhouse, 1875 Hemiptera Gerridae Pondskater sp. In freshwater marsh ?Veliidae Water bug In freshwater marsh Hymenoptera Anthophoridae Xylocopa caffra (Linnaeus, 1767) Apidae Apis mellifera adansoni Latreille, 1804 Formicidae Camponotus grandidieri Forel, 1886 In pitfall traps Camponotus hova Forel, 1891 In pitfall traps Camponotus ?thomasetti Forel, 1912 In pitfall traps Cardiocondyla emeryi Forel, 1881 In pitfall traps Odontomachus troglodytes Santschi, In pitfall traps 1914 Paratrechina sp. In pitfall traps Plagiolepis ?alluaudi Emery, 1894 In pitfall traps Plagiolepis ?exigua Forel, 1894 In pitfall traps Technomyrmex albipes (Smith, 1861) In pitfall traps Vespidae Polistes olivaceus (De Geer, 1773) Lepidoptera Hesperiidae Borbo ?gemella Mabille, 1884 Lycaenidae Leptotes pirithous Linnaeus, 1767 Zizeeria knysna (Trimen, 1862) Odonata Agrionidae Ceriagrion glabrum (Burmeister, 1839) Around marshes Coenagrionidae Agriocnemis pygmaea (Rambur, 1842) Around marshes Libellulidae Diplacodes trivialis (Rambur, 1842) Around marshes Orthetrum stemmale wrightii (Selys, Around marshes 1877) ?Pantala flavescens (Fabricius, 1798) Around marshes Rhyothemis semihyalina (Desjardins, Around marshes 1832) Tramea limbata Selys, 1878 Around marshes Zygomma petiolatum Rambur, 1842 Around marshes Phasmatodea Phasmatidae Carausius sechellensis (Bolivar, 1895) VERTEBRATES Reptiles, Amphibians and Fish Reptiles, amphibians and fish observed during the course of fieldwork are listed in Table 8. The list includes five lizards, one tortoise and one frog. None of the three snakes known from Seychelles (Nussbaum, 1984a) were recorded, although these are rarely seen and may occur there. The endemic caecilian Hypogeophis rostratus has been recorded on Curieuse (Nussbaum, 1984b), but was not observed in the current survey. Given the relatively large size of Curieuse, and its proximity to the large island of Praslin, 83 it is possible that other endemic amphibians and reptiles survive on the island and an extensive survey is recommended. Giant tortoises were present in the late eighteenth century, but the population (presumably one of the endemic granitic Seychelles species) became extinct before 1875 (Bour, 1984). 42 Aldabra giant tortoises were brought to the island from Mahé in 1890- 1902; these also became extinct. 252 tortoises were brought from Aldabra in 1978-82. Although the species breeds on the island, subsequent studies have revealed that the population is declining, probably due to poaching (Stoddart et a/., 1982; Samour ef al., 1987; Hambler, 1994; IUCN, 1993). Table 8. Amphibians, reptiles and freshwater fish on Curieuse. Status: E =endemic, I = introduced, N = native (in central Seychelles). Family Species Status Amphibians Raniidae Ptychadaena mascareniensis (Dumeril & Bibron, 1836) Mascarene frog II Reptiles Gekkonidae Gehyra mutilata (Wiegmann, 1835) Pacific house gecko I Phelsuma sundbergi Rendahl, 1939 day gecko EB Phelsuma sp. (?P. astriata Tornier, 1901) day gecko E Urocotyledon inexpectata (Steiner, 1893) sucker-tailed gecko EB Scincidae Mabuya sechellensis (Dumeril & Bibron, 1836) Seychelles skink E Pamelaescincus gardineri (Boulenger, 1909) burrowing skink Is Testudinidae Geochelone gigantea (Schweigger, 1812) Aldabra giant tortoise I Fishes Anguillidae Anguilla sp. eel N Rivulidae Pachypanchax playfairii Giinther, 1866 Seychelles Killifish E Birds Land birds and seabirds were identified by sight and, in addition, tape playback was used to give data on presence or absence of four species (black paradise flycatcher, Seychelles white-eye, Seychelles scops owl and barn owl). There was a positive response for only one of these species, the barn owl. In total, 14 land birds and waders were recorded (Table 10). Three of these were Seychelles endemics, but two of these endemic species are currently widespread and common within the granitic islands. One, the black parrot, is endangered. Perhaps because of the early introduction of predators to the island, and destruction of natural vegetation, few endemic species have ever been recorded on Curieuse; only Seychelles kestrel and Seychelles sunbird were reported by Newton (1867). Despite the presence of apparently suitable takamaka Calophyllum inophyllum woodland on the plateaux, the Seychelles black paradise flycatcher Terpsiphone corvina has never been recorded (Collar and Stuart, 1985). Only two species of seabird were recorded (Table 9); one of these (fairy tern) breeds on the island. 84 Table 9. Seabirds observed on Curieuse Island. Species Notes Sterna anaethetus bridled tern One individual seen regularly on beaches and flying offshore, January Gygis alba fairy tern Breeding birds present in trees near headquarters buildings (chick seen, 6/8/99) Table 10. Land birds and waders observed on Curieuse M =migrant species E = Seychelles endemic species; E(ss) = Seychelles endemic subspecies Species Notes Butorides striatus green-backed heron Seen regularly around the marshes and mangrove, August and January common moorhen A small number occur at the plateau marshes: not common. Heard occasionally in August, only once in January chicken A few individuals free-ranging around houses on plateau Several birds seen in mangrove on two occasions (August). Many birds seen in mangrove areas and beaches (January) Gallinula chloropus Gallus gallus Arenaria interpres M ruddy turnstone Pluvialis squatarola M grey plover A few birds on beaches, January. Numenius phaeopus M whimbrel One or two individuals seen regularly in mangrove, beaches: August and January Streptopelia picturata ssp. turtle dove Regularly seen in lowland habitats Geopelia striata Alectroenas pulcherrima E Coracopsis nigra barklyi E(ss) Tyto alba Nectarinia dussumieri E Acridotheres tristis barred ground dove Seychelles blue pigeon Seychelles black parrot barn owl Seychelles sunbird common mynah Mainly around inhabited areas and gardens. Seen regularly Seen regularly in woodland habitats (e.g., feeding on Ficus reflexa figs, January) Reported by park staff: population of around six birds, some of which appear to fly from Praslin but others possibly resident A bird heard in lowland forest, January Very common in all habitats Common, especially in lowland habitats and beaches Foudia madagascariensis Madagascar fody Fairly common around inhabited areas Mammals Four mammal species were recorded during the course of fieldwork: Seychelles fruit bat Pteropus seychellensis, feral domestic cat Felis catus, a small number of domestic dogs Canis familiaris, and ship rat Rattus rattus In addition, a fifth species, the house mouse Mus domesticus, was reported by residents. Rodent trapping was carried out in August 1999 and January 2000 (Table 11). Two traplines were established, one in plateau woodland close to the Doctor’s House and ruins of the leper colony and one in hill scrub dominated by cocoplum Chrysobalanus icaco. Only one species of rodent, the ship rat Rattus rattus, was trapped. Capture rates were relatively low, although higher in August (a period of food and water stress) than in January. Curieuse has abundant fruit trees and shrubs (including mangoes and cocoplum) with fruit in season on both visits. The availability of alternative food sources could influence the readiness of rats to enter traps. Table 11. Results of rat trapping, Curieuse Dates Trap-nights No. of rats Rats per 100 Rats per 100 trap-nights trap-nights _(uncorrected) (corrected)* 8 - 13/8/99 140 333) 2 Brom 30.14 13 — 18/1/00 112 18 16.07 YOST) Total (SE) 35.34 Total (NW) PND *Corrected to account for the effect of closed traps; Cunningham and Moors, 1996. DISCUSSION Curieuse is a relatively large island with a great diversity of habitats. Today its central hills have very eroded red earth soils and support sparse scrub which is rich in endemic species (including Coco-de-Mer) and cocoplum scrub. Repeated forest fires have exacerbated erosion on these slopes and caused degradation of the vegetation (Carlstr6m, 1996). The coastal plains support high forest dominated by native takamaka but with many introduced invasive species. Takamaka typically forms dense stands with little undergrowth of shrubs or herbs but these have been invaded by cinnamon and cocoplum, especially where the canopy is interrupted. Some of these invasive aitens support high densities of invertebrates on their foliage but the most important trees for invertebrate communities (and, therefore, insectivorous birds) are native species. The native takamaka forest is threatened by takamaka wilt disease. The island supports a rich endemic flora including important populations of several species of endemic plant (Carlstré6m, 1996) and is likely to be of importance for conservation of endemic invertebrates. Although few species of endemic bird have been recorded here, the proximity of the island to Praslin suggests that several would once have been present before eradication by introduced predators (and, possibly, habitat change). CONSERVATION RECOMMENDATIONS In July-August 2000, a rat- and cat-eradication programme was undertaken on the island by staff of the New Zealand Department of Conservation in a project co-ordinated by the Seychelles Ministry of Environment and Transport. Initially, eradication appeared to have been achieved for rats and mice, although a single cat was caught in early 2001, 86 and it is possible that further individuals remain. However, in August 2001, ship rats were again trapped on the island and at this time a well-established population appeared to be present (M. Hill pers. obs.). It is unclear whether animals survived the eradication attempt or have subsequently re-invaded. Like the original population, rats captured in 2001 all had grey underparts and were relatively small, although significantly larger than the rats present in 2000. Given the high costs of mammal eradications, it is unclear whether further attempts will be made to remove rats. If alien mammals can be eradicated, the island has potential to support populations of several Seychelles endemic birds, in particular the Seychelles magpie-robin and black paradise flycatcher. Both of these species, but particularly the paradise flycatcher, are associated with coastal plateau areas. While the magpie-robin inhabits upland areas on islands such as Cousin and Frégate, hill territories are generally larger than coastal ones, indicating that they are less productive. In order to enhance the suitability of the island for these endemic land birds, actions that must be taken include the control of cocoplum on plateau areas. This spreading shrub has been widely planted on Curieuse to control erosion on the hills. However, it has also spread to plateau areas where it can form dense monospecific stands. These areas are poor in invertebrate food for most bird species, and the density of stems would prevent foraging by the magpie-robin. The takamaka wilt disease threatens the success of paradise flycatcher introduction; this bird inhabits takamaka-badamier woodland on La Digue’s plateau (Collar and Stuart, 1985). Takamaka is common on Curieuse but badamier (Terminalia catappa) relatively rare. Extensive planting of badamier and other native trees should be carried out to mitigate the effects of takamaka wilt disease on coastal forests. 87 Appendix 1. Plant species recorded from Curieuse (excluding seagrasses) Taxonomy of dicotyledons as given by Friedmann (1994). Of monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>1000 individuals observed); C = Common (100 - 1000 individuals observed); F = Frequent (10 - 100 individuals observed); Occasional (3 - 10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: Cu = Cultivated area (including weeds and crops, and garden ornamentals); PG = Plateau grassland; PW = Plateau woodland; HW = Hill Woodland; HSc = Hill Scrub; Gl = Glacis; BC = Beach Crest; Ma = Marsh; Mg = Mangrove. Species Status — Abund. Habitats Notes PTERIDOPHYTA Adiantaceae 1 Acrostichum aureum L. N C Ma, Mg Davalliaceae 2 Nephrolepis biserrata (Sw.) Schott N A HW 3 Nephrolepis cordifolia Schott ? O Cu 4 Nephrolepis multiflora (Roxb.) Jarrett N C PW Gleicheniaceae 5 Dicranopteris linearis Burm. N A HSc Hymenophyllaceae 6 Trichomanes sp. N O HW Lycopodiaceae 7 Lycopodium cernuum L. N F HSc Parkeriaceae 8 Ceratopteris cornuta (Pal.) Lepr. N O Ma Polypodiaceae 9 Phymatosorus scolopendria (Burm. f.) N A PW, HW Psilotaceae 10 Psilotum nudum Sw. N C PW, HW Thelypteridaceae Ii Thelypteris sp. 2N F PW GYMNOSPERMAE 1 Cycas thuarsii Gaud. | R PG ANGIOSPERMAE: Dicotyledons Acanthaceae 13 Asystasia sp. B (sensu Friedmann) Ul A HW, Gl, PG 14 Justicia gendarussa Burm. f. 2] F PW Amaranthaceae 15 Amaranthus viridis L. I F Cu 16 Alternanthera brasiliana (L.) O. Kuntze. I O Cu Only in gardens 17 Alternanthera sessilis (L.) DC. I O Ma Anacardiaceae 18 Anacardium occidentale L. I 6. HW, HSce 19 Mangifera indica L. I & PW, [HW] 20 Schinus terebinthifolius Raddi I R Cu Only in gardens I 21 Spondias cytherea Sonn. F PW : 88 Species Annonaceae 22. Annona muricata L. 23 Annona reticulata L. 24 Annona squamosa L. Apocynaceae 25 Allamanda cathartica L. 26 Alstonia macrophylla Wall ex G. Don. 27 Catharanthus roseus (L.) G. Don. 28 Cerbera manghas L. 29 Nerium oleander L. 30 Ochrosia oppositifolia (L.) K. Schum. 31 Plumeria rubra L. Araliaceae 32 Gastonia sechellarum (Baker) Harms. 33 Polyscias sp. Asclepiadaceae 34 Sarcostemma viminale (L.) Alton 35 Secamone schimperiana (Hemsl.) Klack. Avicenniaceae 36 Avicennia marina (Forssk.) Vierh. Balsaminaceae 37 Impatiens balsamina L. 38 Impatiens wallerana Hook. F. Begoniaceae 3) Begonia semperflorens 40 Begonia sp. Bignoniaceae 4] Tabebuia pallida (Lindl.) Miers. Boraginaceae 42 Cordia subcordata Lam. 43 Tournefourtia argentea L. f Caesalpiniaceae 44 Caesalpinia pulcherrima (L.) Sw. 45 Delonix regia (Hook.) Raf. 46 Intsia bijuga (Coleb.) O. Kuntze 47 Senna occidentalis (L.) Link 48 Tamarindus indica L. Campanulaceae 49 Hippobroma longiflora (L.) G. Don Caricaceae 50 Carica papaya L. Caryophyllaceae St Drymaria cordata (L.) Roem. & Schult. Casuarinaceae 52 Casuarina equisetifolia J. R. & G. Foster Chrysobalanaceae 53 Chrysobalanus icaco L. Combretaceae 54 Lumnitzera racemosa Willd. 5 Quisqualis indica L. Status N I Abund. nw Co © AWA Oman ©) 25] (©) ~Ay OO > 32> | OQ @G © wWoOwBawo O's @ wz ©) 23) Habitats PW, HW PW BC, HW HSc, HW, PW Notes Only in gardens Only in gardens Only in gardens Only in gardens Only in gardens Only in gardens Only in gardens Only in gardens Only in gardens Species Status Abund. Habitats Notes Compositae 51) Dahlia x hortensis Guillaumin I R Cu Only in gardens 58 Dendranthema sp. I O Cu Only in gardens 59 Emilia sonchifolia (L.) Wight I Ei CuyRG 60 Tagetes patula L. I Ja Cu Only in gardens 61 Tridax procumbens L. I O PG, Cu 62 Vernonia cinerea (L.) Less. I A RGaCu 63 Zinnia sp. Cv. I R Cu Only in gardens Convulvulaceae Ipomoea aquatica Forssk. I - Listed in Robertson (1989), not seen 64 Ipomoea batatas (L.) Lam. I O Cu Only in gardens 65 Ipomoea macrantha Roem. & Schult. N FE BC, PW 66 Ipomoea obscura (L.) Ker Gaw!l. I F PG 67 Ipomoea pes-caprae (L.) R. Br. N A BC Crassulaceae 68 Kalanchoe pinnata (Lam.) Pers. 8 BC/PG 69 Kalanchoe sp. R Cu Only in gardens Cucurbitaceae 70 Cucurbita sp. I O Cu Only in gardens al Trichosanthes cucumerina L. I O Cu Only in gardens Dilleniaceae 72 Dillenia ferruginea (Bailon) Gilg. E A HSc, HW Erythroxylaceae 73 Erythroxylum sechellarum O. E. Schultz 13 A HSc, HW Euphorbiaceae 74 Acalypha indica L. I Jel Cu WS Acalypha wilkesiana Mull. Arg. O Cu, PW 76 Codiaeum variegatum L. I O Cu, PW i) Euphorbia hirta L. I A PG 78 Euphorbia ?hypericifolia L. It R Cu 79 Euphorbia prostrata Ait. I C Cu 80 Euphorbia pyrifolia Lam. N F Gl 81 Jatropha pandurifolia L. I O Cu Only in gardens 82 Manihot esculenta Crantz I F Cu, PW Phyllanthus acidus (L.) Skeels ] - - Listed in Robertson (1989); not seen 83 Phyllanthus amarus Schumach. & A PG Thonn. 84 Phyllanthus pervilleanus (Baillon) Mull. N O HSc Arg. Ricinus communis L. I - - Listed in Robertson (1989); not seen Flacourtiaceae 85 Flacourtia jangomas (Lour.) Rauschel I R PW Hydnocarpus pentandra (Buch.-Ham.) I - - Listed in Robertson Oken. (1989); not seen 86 Ludia mauritiana Gmel. Var. E (var.) R HW sechellensis F. Friedmann Gesneriaceae 87 Episcia cupreata (Hook.) Hanst. I R Cu Only in gardens Goodeniaceae 88 Scaevola sericea Vahl. N iC BC 89 90 Species Status — Abund. Habitats Notes Guttiferae 89 Calophyllum inophyllum L. N A PWC, HW Hernandiaceae 90 Hernandia nymphaeifolia (Presl) N R PW Kubitzki Labiatae 91 Ocimum ?canum Sims. I R Cu Only in gardens 92 Plectranthus amboinicus (Lour.) Spreng. 2] R PG Lauraceae 93 Cassythea filiformis L. N O BC 94 Cinnamomum verum Presl. I A PW, HW 95 Persea americana Mill. | O PW Lecythidaceae 96 Barringtonia asiatica (L.) Kurtz N R BC Loranthaceae Bakerella clavata (Desrouss.) S. Balle E(ss) - - Listed in Robertson ssp. sechellensis (Baker) S. Balle (1989); now possibly extinct Malvaceae Oi Hibiscus rosa-sinensis L. I O Cu Only in gardens 98 Hibiscus schizopetalus (Mast.) Hook. I R Cu Only in gardens 99 Hibiscus tiliaceus L. N F BC, PW 100 Sida acuta Burm. f. I F PG, Cu 101. = Sida cordifolia L. 2N O Gl 102 Thespesia populnea (L.) Soland. ex N F PW, BC Correa Melastomataceae 103. Memecylon elaeagni Blume IE a HW Meliaceae 104 = Swietenia sp. I F PW 105 Xylocarpus granatum Koenig N O Mg 106 Xylocarpus moluccensis (Lam.) Roem. N F Mg, BC Mimosaceae Acacia confusa Mert. I - - Listed in Robertson (1989); not seen 107. Adenanthera pavonina L. I A PW, HW 108 Leucaena leucocephala (Lam.) de Wit I A PW, HW 109. Mimosa pudica L. I Cc PG 110 = Paraserianthes falcataria (L.) Niels. I ¢ PW, HW 111 = Pithecollobium unguis-cati (L.) Benth. I C PW Moraceae 112 = Artocarpus altilis (Parkins.) Fosb. I O PW 113. Artocarpus heterophyllus Lam. I O PW 114. Ficus lutea Vahl. N F HW, Gl 115. Ficus reflexa Thunb. seychellensis E (ss) R PW (Baker) 116 = Ficus rubra Vahl N O PW Moringaceae 117. = Moringa oleifera Lam. I O PW Myrtaceae 118 Eucalyptus sp. I R HW 119 Psidium guajava L. I R PW 120 Syzygium malaccense (L.) Merr. & Perry I O PW Species Status Abund. Habitats Notes 121 Syzygium samarangense (Bl.) Merr. & I O PW Perry 122. = Syzygium wrightii (Baker) A. J. Scott 13, F HW, HSc Nyctaginaceae 123 Bougainvillea cultivars I R PW, Cu Onagraceae 124 Ludwigia octovalvis (Jacquin) Raven 21 F Ma Oxalidaceae 125. Averrhoa bilimbi L. I O Cu, PW Papilionaceae 126 Abrus precatorius L. 2N A HW, HSc 127. ~=Canavalia cathartica Thouars. N F BC 128 = Crotalaria pallida Ait. 1 O PG 129 Dendrolobium umbellatum (L.) Benth. N F BC 130 Desmodium incanum DC. I C PW, PG, HSc 131 Desmodium triflorum (L.) DC. I F PG 132. ~=Erythrina ?variegata L. 2N R PG 133. Gliricidia sepium (Jacq.) Walp. I Es PG 134 Pterocarpus indicus Willd. I R HW 135. Tephrosia noctiflora Bojer ex Baker I O Gl 136 =Teramnus labialis (L.) Spreng. I € PG 137. Vigna marina (Burm.) Merr. N F BC Passifloraceae 138 Passiflora foetida L. I F PG 139 — Passiflora suberosa L. I F PG, PW Plantaginaceae 140 Plantago major L. I O Cu Only in gardens Portulacaceae 141 Portulaca grandiflora Hook. I O Cu Only in gardens 142 Portulaca oleracea L. N la PG 143. Portulaca ?pilosa L. I O Gl Punicaceae 144 = Punica granatum L. I R Cu Only in gardens Rhamnaceae 145. Colubrina asiatica (L.) Brogn. N F PG Rhizophoraceae 146 Bruguiera gymnorrhiza (L.) Lam. N F Mg 147 — Ceriops tagal (Perrotet) C. B. Robins. N F Mg 148 = Rhizophora mucronata Lam. N A Mg Rosaceae 149 = Rosa sp. I R Cu Only in gardens Rubiaceae 150. = Canthium bibractatum (Baker) Hiem. N A PW, HW, [BC] 151 Guettarda speciosa L. N O BC 152 = Ixora coccinea L. I O Cu Only in gardens 153. Mitracarpus hirtus (L.) DC. O PG 154. = Morinda citrifolia L. a F PW 155 Tarenna sechellensis (Baker) Summerh. E O HW 156 Paragenipa wrightii (Baker) F. E A HW, HSe Friedmann 91 2 Species Status Abund. Habitats Notes Psychotria pervillei Baker E - - Listed in Carlstr6ém (1996a, b); not seen 157. Tarenna sechellensis (Baker) Summerh. E O HW Rutaceae 158 Citrus reticulata Blanco I R PW 159 — Citrus sinensis (L.) Osbeck I 1g PW Sapindaceae 160 Dodonea viscosa Jacq. N F HSc Sapotaceae 161 Mimusops sechellarum (Oliv.) Hemsl. E O PW 162 Northea hornei (M. M. Hartog) Pierre IE F HSc Scrophulariaceae Striga asiatica (L.) Kuntze I - - Listed in Robertson (1989); not seen Solanaceae 163. Capsicum frutescens L. I O Cu Only in gardens 164 = Solanum lycopersicum L. I O Cu Only in gardens 165 = Solanum melongena L. O Cu Only in gardens Sterculiaceae 166 = -Heritiera littoralis Ait. N € BE Surianaceae Suriana maritima L. N = - Listed in Robertson (1989); not seen Turneraceae 167 = Turnera angustifolia Miller I C HSc, HW Verbenaceae 168 Premna serratifolia L. N O BC 169 = Stachytarpheta jamaicensis (L.) Vahl. I A PG, PW 170 = Stachytarpheta urticifolia (Salisb.) Sims. I A RGSPRW 171 = Vitex trifolia L. I R PG ANGIOSPERMAE: Monotyledons Agavaceae 172. Agave sisalana (Perr. ex Engelm.) Drum. I Cc PW, HSc & Prain 173 + Furcraea foetida (L.) Haw. I F PW Amaryllidaceae Crimum amabile Ker.-Gawl. 21 - - Listed in Robertson (1989); not seen 174. ~ Hymenocallis littoralis Salisb. 21 € PW Araceae 175 Alocasia macrorrhiza (L.) G. Don. I C PW 176 = Anthurium sp. I R Cu Only in gardens 177. ~~ Caladium bicolor (Dryand.) Vent I R Cu Only in gardens 178 Colocasia esculenta (L.) Schott. I O PW 179 Dieffenbachia sequine (Jacq.) Schott I R Cu Only in gardens 180 Syngonium ?podophyllum Schott. I R Cu Only in gardens Bromeliaceae 181 Ananas comosus (L.) Merr. I F PW Cannaceae 182. Canna hybrids I O Cu Only in gardens Commelinaceae 183. Commelina sp. 21 Ie Ma 184 Tradescantia spathacea Swartz I O Cu Only in gardens 23) Species Status Abund. Habitats Notes Cyperaceae 185. Bulbostylis barbata (Rottb.) C. B. Cl. N © HSc 186 = Cyperus halpan L. ? IE Ma, HSc 187. Cyperus?rotundus L. ? C Ma 188 Eleocharis dulcis (Burm. f.) Trin. N O Ma, HSc 189 = Fimbristylis cymosa R. Br. ¥ Cc BES RW. Gl 190 Fimbristylis sp. 2 (glacis sedge) 2 Fe HSc 191 = Kyllinga polyphylla Willd. ex Kunth N ¢ PG 192 Kyllinga sp. 2 ? O PW 193. Lophoschoenus hornei (C. B. Cl.) Stapf. igh A HSc 194 = Mariscus dubius (Rottb.) Fischer N A PG 195 = Mariscus pennatus (Lam.) Domin. N F Ma 196 Scleria sumatrensis Retz. N (© Ma 197 Scleria sp. 2 v Cc PW 198 Thoracostachyum floribundum (Nees) C. Ig Fi HW, PW BAG: Dioscoreaceae 199 Dioscorea alata L. I O PW Flagellariaceae 200 =~ Flagellaria indica L. N 2 PW Gramineae 201 Bambusa vulgaris Schrad. Ex Wendl. I R PG 202. Brachiara umbellata (Trin.) W. D. N A HW, HSc, Clayton PW 203 = Chloris barbata (L.) Sw. 2 F PG 204. Cymbopogon sp. I R Cu, PW 205 Dactyloctenium ctenoides (Steud.) v F PG Bosser 206 Digitaria ?horizontalis Willd. U € PG 207 ~—‘ Eleusine indica (L.) Gaertn. v FS PG 208 Enteropogon sechellensis (Baker) Dur. & N C Gl Schinz 209 = Eragrostis tenella (L.) P. Beuv. 2 Ig BC, Mg 210 Heteropogon contortus (L.) P. Beuv. v Cc Gl 211 Hyparrhenia rufa (Nees) Stapf. v F HSc, Gl 212 Ischaenum heterotrichum Hack. r Ist BC 213. Oplismenus compositus (L.) P. Beuv. N ¢€ PW 214 = Panicum brevifolium L. N Cc PG, PW 215) = Panicum maximum L. ? O PG 216 Paspalum conjugatum Berg N Ie PG 217 ~~ Pennisetum polystachyon (L.) Schult. u F Gl 218 Saccharum officinarum L. I O Cu Only in gardens 219 Sporobolus diander (Retz.) P. Beuv. B F Gl, BC 220 Sporobolus virginicus (L.) Kunth. N A BE] PG 221 Stenotaphrum dimidiatum (L.) Brogn. N A PG Hypoxidaceae 222. ~ Curculigo sechellensis Bo). E (C HSce 223. =H ypoxidia rhizophylla (Baker) Dur. & E (Ce HW, HSe Schinz Lilaceae 224 ~~ Cordyline fruticosa L. (A. Chev.) I R Cu Only in gardens 225 Dianella sp. (varieg.) I R Cu Only in gardens ~ . eat 94 Species Status | Abund. Habitats Notes 226 Dracaena reflexa Lam. var. angustifolia N A HW, PW Baker 227 ~~ Sansevieria trifasciata Hort. ex Prain I R Cu Only in gardens Marantaceae 228 Maranta arundinacea L. I O PW Musaceae 229 Musa sp. I F Cu, PW Orchidaceae 230 = Cynorkis ?fastigiata Thouars N R HSc 231 ~~ Disperis tripetaloides (Thouars) Lindl. N ie HW Vanilla phalaenopsis Reichb. f. IE - - One 19" century record (M. North; in Carlstrém, 1996; now locally extinct 232 ~~ -‘Vanilla planifolia Andrews I C HW, PW Palmae 233 = Cocos nucifera L. N € BEIEG 234 ~~ Deckenia nobilis Wendl E F HSc 235 = Lodoicea maldivica (Gmel.) Pers E A HSc, HW, [HW] Nephrosperma vanhoutteanum (Wendl. E - - Listed in Robertson ex van-Houtt.) Balf. (1989), Carlstr6m (1996a, b); not seen 236 ~=Phoenicophorium borsigianum (K. E A HW, PW Koch) Stuntz Pandanaceae 237 ~~ Pandanus balfourii Mart. 18 O BC, PW 238 Pandanus hornei Balf. f. E F BC, PW 239 Pandanus multispicatus Balf. f. E A HSc 240 Pandanus utilis Bory I R PW Typhaceae 241 = Typha javanica Schnitzl. ex Zoll. N € Ma Zingiberaceae 242 _ Alpinia purpurata (Vieill.) Schumann I O Cu Only in gardens _ pe eee 7 mt a Ta Ae Att et ot 1 ony eo ee oe ig i < _: = 1 ale lato ng Wigs 7 ey hemi ae TE Ds an Ne i ai} — ai bv eG Wiis Cited tier hl 9 rar: . 3 fy a y : ; Pate i L bo i) a ey Piro Fi Da } ‘ i. (le BAP oh if) pias) i {i . pat aN = Fi eo i ee nei bay oe Ore bam |b ves ti ray tr 5 | . rt Le! a . AD Sriatisistehel ' tke vy vis 6 if ‘ Pit ven ue ail ut: what : oe i | _ Anita) f rid worse tips ue? - ha Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, UK. 98 The annual rainfall pattern of Denis also differs from that of the granitic Seychelles and coralline islands to the south. On Denis, rainfall is more evenly distributed through the year than on Mahé; there are fewer dry months than on islands to the south (Walsh, 1984). Table 1. Denis Island: monthly rainfall (mm), 1976-1984. (Data: National Meteorological Services, Seychelles, unpublished data). Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 1976 [7/3253 324 n/a n/a n/a 48.0 19.1 35.6 DDI ily 11.9 241.8 1977 366.0 341.5 n/a [68:57 “752 45:0, 56:5" 464.5 8:9" * 2722009 S826 1978 n/a 1952555 937/20 n/a 74.0 26.0 18.5 n/a 39°05,» L060 Mania n/a 1983 DSO 7/850. n/a n/a n/a AQ 1 M659" 28712 491 Se 920 OSS) 1984 252: 0247-69 ei eO 96.0 0.0 47,5 255) SO NOMO os 1092578 2159/0 ls OO RSS 5l Mean 266.6 1992 47.0 132.3 48.5 AZ 2042, 1236 134.2 5 sl4820 992 eee OSk0 HISTORY The island was discovered in 1773 by Denis de Trobriand and named for himself. He found an island with abundant sea turtles, land tortoises, sea lions (or dugong) and birds (Bradley, 1940). His records suggest that the original vegetation of the island was high forest with species including Pisonia grandis or a similar tree (Stoddart and Fosberg, 1981). The existence of extensive guano deposits (Baker, 1963) implies the presence of large colonies of nesting seabirds, possibly tree-nesters. In the 19th and 20th centuries the island underwent complete transformation, first through the cultivation of coconuts, planted from around 1890 (Stoddart and Fosberg, 1981), then guano extraction (from 1929-41; Baker 1963), and finally by the extensive replanting of coconuts. In 1975, the island was sold to a new owner. An airstrip was built and a small tourist lodge opened. Today, the coconut plantation on Denis is no longer managed for production and the island is managed as a resort with 25 villas. The permanent population of the island (50-70 people) is employed in the hotel and tourists travel to Denis by small plane from Mahe. The flora, fauna and ecology of Denis (and Bird Island) were the subject of a detailed paper in the 1980s (Stoddart and Fosberg, 1981). The two islands were visited by earlier naturalists including Coppinger (1885) and Fryer (1910); unfortunately, some of the early reports seem to be characterised by confusion between the two islands. FLORA AND VEGETATION Flora A total of 179 plant species were recorded on Denis Island, including four ferns, one gymnosperm (introduced) and 174 angiosperms (Appendix 1). Of the angiosperms, 119 (68.4%) species are regarded as introduced (Friedmann, 1994) and 37 (21.3%) 99 native. No species endemic to Seychelles was recorded. At least 55 ornamental or edible species were restricted to garden areas. While few previous records of the flora of Denis Island exist, a number of workers have collected specimens, or made observations on the island. Many of the species recorded in 1999/2000 were not listed by previous workers; these include a number of ornamental species undoubtedly introduced to enhance the hotel grounds in recent years. Some species were probably overlooked in earlier surveys, including the fig Ficus lutea, tamarind Tamarindus indica, and agati Adenanthera pavonina (all represented today by large trees). Twelve species recorded by earlier visitors were not observed (see Appendix). At least two of these species were probably synonyms of species recorded in the 1999/2000 survey; others are now extinct and some may never have occurred on Denis Island. In some early records (notably Fryer, in Christensen, 1912; Summerhayes, 1931) there appears to be some confusion between Bird and Denis Islands, thus some species which have probably never occurred on Bird (mangrove fern Acrostichum aureum and bulrush Typha javanica) are recorded for that island. Tribulus cistoides, listed for Denis by Summerhayes (1931), may have been a record from Bird Island where the species still occurs (or this may refer to an extinct population). Excluding locally extinct species, probable synonyms, and species that probably never occurred there, the total plant list for Denis Island stands at 185 species. Compared to the flora of the granitic islands, that of Denis is notable for its lack of endemic species and the dominance of introduced plants (of the total Seychelles flora, around 54% are introduced and 9% endemic: Procter, 1984). Of the introduced plants established on Denis Island, only seven are generally regarded as invasive weedy species (Carlstr6m, 1996a; Fleischmann, 1997). One of these, lantana Lantana camara, is present in relatively small numbers but has the potential to become a serious weed of open areas. At least two others, fatak grass Panicum maximum and Passiflora suberosa, are herbaceous species which can be displaced by native woody vegetation. The most widespread and well-established woody introduced species is casuarina Casuarina equisetifolia, which appears more invasive here than it is on the granitic islands. Papaya Carica papaya is also widespread in coconut woodland on Denis. In addition to these alien species the coconut Cocos nucifera, although probably native to the Seychelles, is present in extremely high numbers to the exclusion of other plants. One species of interest is the rampant liana ?7ylophora coriacea (provisional identification), a rare native species known from Aldabra and Silhouette (Friedmann, 1984) but found to be abundant on Denis, often climbing Casuarina trees to a height of 15 m or more. Vegetation The extents of major vegetation types on Denis Island are shown in Table 2, and Figure 2. The whole island is dominated by former coconut plantations, but the north west of the island has a high proportion of Casuarina equisetifolia, and areas around the airstrip and the east by broad-leaved trees, especially Terminalia catappa. 100 In total, 40 vegetation plots were completed, 20 in October and 20 in April. These covered 4,000 m? or 0.28% of the island’s surface. The 40 plots were located randomly within habitats excluding grassland, garden and marsh: the survey covered 0.37% of the targeted area. A summary of results is shown in Table 3. The vegetation of Denis Island had a relatively low density of trees and the tree layer was species-poor. A total of 12 tree species was recorded, seven of which were probably native. Three species together accounted for 70% of all individuals. The most abundant tree was bwa torti Morinda citrifolia, a species that is possibly introduced (Friedmann, 1994); 51 of 174 trees (29.3%) were M. citrifolia. Other abundant species were Cocos nucifera (45 of 174 trees, 25.9%) and Casuarina equisetifolia (25 trees, 14.4%). The most widespread species of the shrub layer were Cocos nucifera (in 38 of 40 plots, mean cover 33.1%), Morinda citrifolia (in 33 plots, mean cover 16.5%), and Carica papaya (eight plots, mean cover 3.2%). The herb layer was particularly dense and was dominated by Nephrolepis sp., which occurred in 39 of 40 plots (mean cover 36.7%). Three other species occurred in more than 12 plots: Cocos nucifera (in 30 of 40 plots, mean cover 4.6%), Phymatosorus scolopendra (29 plots, mean cover 23.9%) and Morinda citrifolia (27 plots, mean cover 2.5%). Table 2. Extent of major vegetation types, Denis Island. Vegetation Coconut with scrub Scrub (exotic) Broadleaf woodland (exotic) 3.4 Broadleaf woodland (native) Diff Beach crest vegetation Sy) Marsh 0.5 Grassland/garden Table 3. Vegetation plot summary, Denis Island. Habitat Plots Mean Mean Meanshrub Meanherb’ Openleaf Bare Dead wood altitude trees layercover layer cover litter rock _— (pieces per (m asl) ha’! (%) (%) cover (%) _(%) plot) Woodland 40 <5 435 46.9 61.9 36.9 Ie) 1E35 /scrub 101 —_— _—— = 200 metres Figure 2. Denis Island: vegetation. 102 Compared to that of the other coralline island studied (Bird Island), the vegetation of Denis Island is rather diverse. Stoddart and Fosberg (1981) recognised four different vegetation units on Denis: Littoral hedge (beach crest), Casuarina woodland, coconut woodland and marsh. Today, at least three further vegetation types occur: broadleaf woodland, grassland and ornamental gardens. Broadleaf woodland occurs in two relatively large areas, to the north and south of the airstrip. In much of this woodland Terminalia catappa is the dominant tree, with Casuarina, Cocos and Calophyllum. An area to the north of the airstrip is composed of Tabebuia pallida. Grassland areas, dominated by a variety of grass species and low herbs include the airstrip, village and farm. The airstrip is maintained by mowing, other areas by cattle grazing. Gardens are situated around habitation in the north and west of the island. The tourist operation, which was small at the time of Stoddart and Fosberg’s visit, has grown and the area devoted to gardens has increased. A number of ornamental plants unrecorded in the 1970s are now present on the island although most are not found away from cultivated areas. The few ornamentals that have found their way into the flora of wild habitats on Denis were earlier introductions, including /pomoea hederifolia and Euphorbia cyathophora The dominant vegetation type of the island is sparse open woodland of Cocos nucifera and Morinda citrifolia, with occasional trees of other species including Casuarina, Ficus lutea and Terminalia catappa. The shrub and herb layers of this vegetation were usually dense and were dominated by Morinda and Nephrolepis. Of the vegetation units recognised by Stoddart and Fosberg, that which has shown the most change is the marshland. Although wet areas were still present in 1999 and 2000, they appear reduced in extent (see map) and several of the marsh areas were heavily shaded by Terminalia catappa and Cocos nucifera, with few aquatic macrophytes surviving. Acrostichum sp. was still abundant and widespread. Typha javanica was restricted to one small pond, heavily shaded by coconut regrowth. Few marshes had any open water, and in these, water levels varied with the tide. INVERTEBRATES Pitfall Trapping The pitfall trap assemblages were large (Table 4). Overall pitfall assemblages were larger in April than October. Assemblages on Denis Island were larger than those on the granitic islands in both seasons. As on all other islands, assemblages were dominated by ants: ants formed 54.8% of the total number of individuals in October, 76.4% in April. The most abundant species in both seasons was an ant Odontomachus troglodytes (which made up 52.9% of individuals in October and 70.3% in April). However, excluding the ants, assemblages on Denis were still larger than those of the granitic islands. Crustacea (mainly Amphipoda), Dermaptera and Blattodea all formed significant parts of the overall assemblage (Fig. 3). Blattodea are favoured food items of the Seychelles magpie-robin. 103 The crazy ant Anoplolepis gracilipes was present on the island, but only two individuals were collected in pitfall traps, in plots E13 and F11, suggesting that this pest species was uncommon. On nearby Bird Island, an extremely high population density of this ant has caused many conservation problems including the death of native trees (Hill, in prep.) and the eradication of native reptiles from large parts of the island (Feare, 1999a). The status of crazy ants on Denis Island should be monitored, and control methods used if necessary. Table 4. Pitfall assemblages from Denis Island. only invertebrates over 2 mm body length counted (number in parentheses: excluding ants). Mean no. individuals per 5 traps SE season NW season Apr 110.0 (49.7) ISS) (S27) 61.8 (9.4) 61.1 (16.0) Island Habitat Denis Plateau woodland/scrub Granitic islands (mean) 7 | |SBlattodea | me | Coleoptera _ M1 Dermaptera | |G Crustacea il | Mollusca |EiMyriapoda ‘Ospiders [Mothers _ Total NI (excluding ants) Figure 3. Composition of pitfall assemblages on Denis Island. Leaf-insect Counts Leaf-insect counts were carried out for 11 tree and shrub species, four of these in both seasons (Table 5). For all trees counted in both seasons, the populations of invertebrates on leaves were at a higher density in the wet north west monsoon season. The highest counts were for the native tree Pisonia grandis, which is uncommon on Denis Island (only one individual tree was found in the vegetation plots). As found on some other islands, the shrub Morinda citrifolia (status uncertain; possibly introduced) also had very high leaf counts. Morinda is the most abundant tree on Denis Island and dominates the island’s vegetation. One introduced tree, Tabebuia pallida, also showed high leaf counts per square metre of leaf. 104 Table 5. Density of invertebrates on foliage, Denis Island. n= no. of leaves counted; NI = Number of individual invertebrates. SE season (October n mean NI mean NI leaf! ix NW season (April n mean NI Mean NI leaf! m? Species Introduced species Carica papaya Tabebuia pallida 0.555 9.82 0.667 D3 AES? Native species Calophyllum inophyllum 0.300 30.81 Cordia subcordata 0.340 35. Guettarda speciosa Hibiscus tiliaceus 0.370 25.56 Pisonia grandis 63.02 3373.66 Scaevola sericea 0.300 28.49 Terminalia catappa 0.741 52.20 Thespesia populnea ?Status unknown Morinda citrifolia Malaise Trapping Malaise trapping was carried out in both seasons. Four Malaise traps were run in October 1999 and five in April 2000. Assemblages were large and slightly larger in October (mean NI = 946.5) than in April (mean NI = 828). Malaise trap assemblages included members of 13 invertebrate orders. In both seasons, the Diptera were dominant (Diptera accounted for 41.3% of individuals in October, 45.9% in April). Other important orders included Hymenoptera (15.3% of the assemblage in October, 37.9% in April) and Lepidoptera (16.9% of the assemblage in October, 12.5% in April). Assemblages also contained Orthoptera and Blattodea. The majority of taxa collected have yet to be identified to species level. Observation Most invertebrates observed on Denis Island were of introduced or cosmopolitan species (Table 6). One Seychelles endemic cricket Pelerinus rostratus, not otherwise known outside the granitic islands, was probably introduced. At least four species of Odonata were observed, sometimes in large numbers. Observations were most frequent over the airstrip, but observations of dragonflies and damselflies around the island’s wetlands suggest that some species may breed on the island. Few other invertebrates were observed in wetland areas: the water snail Me/anoides was found in large numbers, along with mosquito larvae, in April. Table 6. Invertebrates observed, Denis Island Order Family Species Notes Mollusca: Gastropoda Subulinidae Subulina octona Bruguieére, 1792 Very common, pitfall traps Thiaridae Melanoides tuberculata (Miller, 1774) Abundant, ‘freshwater’ marsh Crustacea: Decapoda Coenobitidae Coenobita brevimanus Dana, 1852 Occasionally in rat traps Coenobita rugosus H. Milne-Edwards, Mainly close to shore 1837 Coenobita perlatus H. Milne-Edwards, Red hermit 1837 Grapsidae Grapsus tenuicrustatus (Herbst, 1783) On rocks, sea’s edge Geograpsus crinipes (Dana, 1851) Regularly seen near beaches Ocypodidae Ocypode ceratophthalmus (Pallas, 1772) | On beaches Ocypode cordimana Desmarest, 1825 Abundant in all habitats, diurnal and nocturnal Myriapoda: Chilopoda Scolopendridae Scolopendra subspinipes (Leach, 1918) Diplopoda Paradoxosomati- Oxidus (Orthomorpha) gracilis (K. In pitfall traps dae Koch, 1847) Trigoniulidae Spiromanes braueri (Attems, 1900) In pitfall traps Spiromanes ?seychellarum Saussure & In pitfall traps Zehntner, 1902 Insecta: Coleoptera Scarabaeidae Oryctes monoceros (Olivier, 1789) Frequent Protaetia maculata (Fabricius, 1775) Hymenoptera Anthophoridae Xylocopa caffra (Linnaeus, 1767) Formicidae Anoplolepis gracilipes (Smith, 1857) In pitfall traps Cardiocondyla emeryi Forel, 1881 In pitfall traps Odontomachus troglodytes Santschi, In pitfall traps 1914 Paratrechina sp. In pitfall traps Plagiolepis sp. In pitfall traps Technomyrmex albipes (Smith, 1861) In pitfall traps Tetramorium sp. In pitfall traps Vespidae Polistes olivaceus (De Geer 1773) Lepidoptera = Lycaenidae Zizeeria knysna (Trimen, 1862) Collected April, not abundant Nymphalidae Hypolimnas misippus L. 1764 Observed April Neuroptera Myrmeleontidae Myrmeleon obscurus Rambur, 1853 To light, 10/99 Odonata Coenagrionidae Ceriagrion glabrum (Burmeister, 1839) | One damselfly observed at marsh, 12/10/99 Libellulidae Diplacodes trivialis (Rambur, 1842) or One individual observed over Orthetrum stemmale wrightii (Selys, airstrip, April 1877) ?Pantala flavescens (Fabricius, 1798) Large, orange-brown dragonfly observed over airstrip, April. Several indivs observed Tramea limbata (Selys, 1869) Two indivs. observed, Orthoptera Phasgonuridae Ruspolia difjerens (Serville, 1838) To light Tettigonidae Pelerinus rostratus (Brunner, 1878) 105 To light 106 VERTEBRATES Reptiles and Amphibians Six reptile species were observed on Denis; four lizards, a snake and a giant tortoise (see Table 7). At least three of these species, Gehyra mutilata, Geochelone gigantea, and Ramphotyphlops braminus, are introduced. A giant tortoise species, presumably one of the taxa endemic to the granitic Seychelles, was present in 1773 (Bour, 1984), but this population is now extinct. Fossil giant tortoise eggs from Denis have been dated to 1308+85 yr BP (Burleigh, 1979). In addition to the land reptiles, two species of marine turtle breed regularly on Denis Island: the green sea turtle Chelonia mydas (L.) (Frazier, 1984) and hawksbill Eretmochelys imbricata (L.). Table 7. Reptiles observed, Denis Island. Status: E =endemic, I = introduced, N = native (in central Seychelles). Family Species Status Gekkonidae Gehyra mutilata (Wiegmann, 1835) Pacific house gecko I Phelsuma sundbergi Rendahl, 1939 day gecko ls, Phelsuma sp. (?P. astriata Tornier, 1901) day gecko E Scincidae Mabuya sechellensis (Dumeril & Bibron, 1836) Seychelles skink Js Testudinidae — Geochelone gigantea (Schweigger, 1812) Aldabra giant tortoise I Typhlopidae Ramphotyphlops braminus (Daudin, 1803) Robb, 1966 _ Brahminy blind snake I Birds In total, 17 land birds and waders were recorded of which six were resident species (Table 8). Three of these resident species were obvious introductions (barred ground dove, common mynah, Madagascar fody). One species (turtle dove) is likely to have been introduced although it was recorded on the island early in the twentieth century (Fryer, 1910). The individuals observed showed grey heads and relatively large size, characteristics of the introduced Madagascan race S. picturata picturata rather than the Seychelles endemic form S. picturata rostrata (which appears effectively extinct throughout its former range; Gaymer ef al., 1969). Only one endemic species was observed (Seychelles blue pigeon). Together with the moorhen, this seems to comprise the entire native bird fauna. Stoddart and Fosberg (1981) suggest that the Denis population of the latter species is introduced but, if so, the introduction must have occurred prior to 1866, when Newton obtained three live specimens (Newton, 1867). In 1908, a sunbird Cinnyris sp. was recorded (Fryer, 1910), Stoddart and Fosberg (1981) suggest that this was the souimanga sunbird Nectarinia sovimanga. However, the nearest extant populations of this species are on Aldabra and Cosmoledo (Sinclair and Langrand, 1998): a much more likely species would appear to be Seychelles sunbird Nectarinia dussumieri, which is widespread on islands of the granitic Seychelles. No sunbirds were observed during the current survey, and it appears that this population is now extinct. In general, sunbirds appear relatively resistant to extinction caused by human intervention; there are no known extinctions of NV. sovimanga populations in the 107 Aldabra group (Diamond, 1984), despite massive environmental degradation on some of the islands. Two of the land bird species observed, common mynah and Seychelles blue pigeon, were not recorded by Fryer (1910), and appear to be more recent invaders or introductions. One of the introduced land bird species recorded (common mynah), is a potential nest predator of endemic birds. Eight seabird species were recorded (Table 9). The most abundant species was the fairy tern Gygis alba; during the October 1999 survey, thousands were observed roosting in tall Casuarina trees, together with smaller numbers of brown noddy Anous stolidus. Other seabirds were much less abundant. In April 2000, there was evidence of breeding of fairy terns, brown noddies, and white-tailed tropic birds (the latter species nesting in Casuarina trees). Domestic hens and quail are kept caged in a large poultry unit on the island; there appeared to be no free-living fowl. Table 8. Land birds and waders observed on Denis Island. M = migrant species; V = vagrant species; E = Seychelles endemic species. Species Notes Anas querquedula V Gallinula chloropus Dromas ardeola M garganey common moorhen crab plover Charadrius leschenaultii M_ greater sandplover Pluvialis squatarola M grey plover Numenius phaeopus M whimbrel Eurasian curlew common greenshank Numenius arquata M Tringa nebularia M Xenus cinereus M terek sandpiper common sandpiper ruddy turnstone Actitis hypoleucos M Arenaria interpres M Calidris ferruginea M curlew sandpiper barn swallow turtle dove Hirundo rustica V Streptopelia picturata ssp. barred ground dove Seychelles blue pigeon common mynah Madagascar fody Geopelia striata Alectroenas pulcherrima E Acridotheres tristis Foudia madagascariensis One bird, east of airstrip, 10-12/10/99 One bird seen in freshwater marsh, 11/10/99. Not seen April 2000 Several birds seen 11/10/99. Group of three birds on beaches, 9/4/00 Several birds seen regularly on airstrip, October and April. Distinguished from C. mongolus by call Seen regularly, on airstrip and beaches, both October and April Seen regularly, especially on airstrip, both October and April. Flock of 17 birds seen, E. end of airstrip, 12/4/00 One bird on airstrip 16/04/01 One bird in shallow sea, eastern end of airstrip, 12/10/99 One bird with Curlew Sandpipers on airstrip, 7/10/99 One individual, E. end of airstrip, 12/10/99 Seen regularly, on airstrip and beaches, in groups of up to 30, both October and April Seen regularly, on airstrip and beaches, in groups of up to 10 (October only) One individual seen flying over airstrip, 11/4/00 Seen regularly. Doves on Denis Island have features close to the introduced Madagascan subspecies S. p. picturata, rather than the endemic S. p. rostrata Seen regularly Seen occasionally, especially around the village. Reported common Seen regularly Seen regularly, many nests observed (some with young chicks present) in October 108 Table 9. Seabirds observed, Denis Island. + = species breeding on island Species Notes Phaeton lepturus + white-tailed A few individuals seen. Reported to nest in casuarinas on tropicbird the island. Observed nesting 16/04/01 Fregata minor great frigatebird One adult male seen flying low over airstrip, 11/10/99. Juvenile and female frigatebirds (F. minor or F. ariel) regularly observed in October. Both species probably occur Sterna bergii greater crested tern Regularly seen on rocks close to island (October only) Anous Stolidus + brown noddy Roosting in casuarinas (October). Breeding April: one well-grown chick observed dead beneath casuarina 6/4/00, large fledgling observed on forest floor 6/4/00 Anous tenuirostris lesser noddy Seen flying in to roost, October and April. Around 35 birds observed roosting in tall coastal casuarina, 9/4/00 Sterna anaethus bridled tern Around 10 birds roosting in tall casuarinas, Muraille Bon Dieu, 6/4/00 Sterna fuscata sooty tern Regularly seen close to island, October and April Gygis alba + fairy tern Large numbers of birds (hundreds) roosting in casuarinas, October. Evidence of breeding in April: chicks and eggs observed. Most nesting appears to occur in tall casuarinas VERTEBRATES: MAMMALS Mammals observed in the course of fieldwork were recorded (Table 10). In addition, rodent trapping was carried out in October 1999 and April 2000 (Table 11). Two traplines were established, both in coconut woodland (former plantation). Two species of rodent were trapped. Ship rat Rattus rattus was the most frequent, while house mouse Mus domesticus were taken in small numbers (a total of six mice taken in 279 trap-nights). Overall trapping rates were relatively high with higher rates in October (at the end of the dry season when food and water stress are greatest). Table 10. Mammal species recorded on Denis. Status 1999/2000 Status August 2001 Felis catus L. A large population present: five individuals seen on one ?Extinct occasion (at pig farm). Rattus rattus L. Widespread Extant Mus domesticus L. Collected in rat traps, and regularly seen in woodland habitats. Extant Also in buildings and anthropogenic habitats. Bos taurus L. c. 30 individuals, usually tethered Extant Sus domesticus Erxleben cc. 100 animals Extant 109 Table 11. Results of rat trapping Dates Trap-nights No. of rats Rats per 100 trap- Rats per 109 trap- nights nights (uncorrected) (corrected )* 7 - 12/10/99 140 50 Be, 64.9 7 — 12/4/00 139 46 3321 34.5 All islands 1893 595 31.4 *Corrected to account for the effect of closed traps: Cunningham and Moors, 1996 In July 2000, a rat and cat eradication programme was undertaken on the island by staff of the New Zealand Department of Conservation, in a project coordinated by the Seychelles Ministry of Environment and Transport. Initially, the project appeared to be successful in eradicating rats on Denis, but trapping in August 2001 revealed small populations of rats in at least two areas of the island, and rats have since spread to most areas of the island. It is possible that rats invaded the island following a successful eradication. Mice probably survived the eradication: although they were not recorded until early 2001, they were found to be abundant and widely distributed around the island by August 2001. A small number of cats (possibly only two individuals) survived the cat and rat eradication of 2000, but were killed in 2001. Cats now appear to be extinct on the island. The herd of cattle on Denis Island (numbering about 30) appeared to have a limited impact on the island’s ecosystems, because the animals were usually kept tethered in Open grassy areas on the east coast of the island or in grassland near the pig farm. Their major impact was on fresh water marsh areas which are limited in extent and fragile. Cattle appeared to cause physical disturbance and eutrophication of the marsh (especially that at CL 5215 7915). CONSERVATION RECOMMENDATIONS Although Denis is a coralline island with a history as a coconut plantation, it now has relatively extensive coastal forest dominated by native tree species, and the remaining coconut plantation areas are undergoing succession to woodland. Native trees support high densities of invertebrates on their foliage which could provide food for introduced small insectivores such as Seychelles warbler Acrocephalus sechellarum, Seychelles white-eye Zosterops modestus and Seychelles fody Foudia sechellarum. The woodland is particularly rich in badamier Terminalia catappa and is rather marshy, resembling woodland on La Digue which supports the major population of black paradise flycatcher Terpsiphone corvina (Watson, 1981). The island could at present support around 10 pairs of this highly endangered species (Currie ef a/. in prep.), and this number would rise with appropriate management of marshland and woodland habitats. Ground-dwelling invertebrate assemblages were also relatively large and similar in composition to those of Cousin Island which supports a population of Seychelles magpie-robin Copsychus sechellarum, suggesting that this species could survive on Denis if translocated. Since 110 magpie-robins forage on the ground, some clearance of dense coconut regrowth would be necessary to increase the area of suitable habitat available to the birds. Management for conservation on Denis Island should include the encouragement of forest succession through the removal of coconut and planting of native broadleaf trees including Terminalia and Pisonia. Pisonia probably made up the original vegetation of the island prior to human settlement. However, most importantly, complete eradication of introduced predators will be necessary before translocation of endemic bird populations can occur. The most important predators remaining on the island are ship rats, although mynahs might also present a hazard to an establishing population of Seychelles magpie- robin as they are known to be nest competitors and nest predators of magpie-robins. Assessment work suggests that Denis could easily support viable populations of some of Seychelles’ most endangered endemic birds, but the translocation of Seychelles endemic birds to Denis would not be a classic “reintroduction” of a species to sites in its former range where it has been extirpated by introduced predators or environmental change. None of the endangered endemic birds of the granitic Seychelles have ever been recorded on Denis Island: the endemic fauna has been restricted to two common species, the Seychelles blue pigeon and Seychelles sunbird (the latter now locally extinct). It is generally advised that translocations of endangered animals should generally be kept within the species’ known range, in locations where it has died out (reintroduction rather than introduction; IUCN, 1998). Translocations within a species’ known historical range have a better chance of success than those outside (Towns ef al., 1990). However, the conservation of species threatened with extinction may justify translocation outside the natural range. While introductions to pristine islands that have never had alien predators can be detrimental to existing habitats and species (Towns et al, 1990), this is less likely to be the case where the island concerned has previously suffered major habitat disruption and the introduction of alien predators (as on Denis). In the Seychelles, at least two circumstances favour the translocation of bird species outside those islands which can be precisely defined as the species’ former range: 1) Historical records of bird distribution are poor with very little information before 1865 (Rocamora and Skerrett, 2001) by which time much human-mediated environmental change had already occurred. Alien predators were introduced with, or even before, the first human settlement in 1770, and were responsible for the loss of island populations of several species (Newton, 1867; Diamond, 1984). 2) Most of the land area of the archipelago is currently unsuitable for many of the rarer species, and likely to remain so; 78% of the granitic Seychelles’ land area is contained in the two islands Mahé and Praslin where it is impossible to eradicate alien predators. While the Seychelles biota as a whole shows a high degree of endemism (Stoddart, 1984), there is little evidence of island endemism, especially on the low coralline islands where the majority of the flora and fauna is made up of widely- distributed species (Stoddart and Fosberg, 1984). The absence of endemic species on islands such as Denis can be advantageous to translocations of endemic vertebrates, JHE) ensuring little conflict of interest with the conservation of pre-existing populations of other endemic taxa (Atkinson, 1990). In this situation, the coralline island of Denis would appear to offer an excellent opportunity to establish additional populations of some endemic birds as part of ongoing species recovery programmes. At least two endemic land birds have been translocated to coralline islands in the past and become established; the Seychelles magpie-robin survived on Alphonse for 60 years before being driven to extinction by habitat change and/or the introduction of cats in the 1950s (Collar and Stuart, 1985). The Seychelles fody was introduced to D’Arros in 1965 (Penny, 1974). The isolation of Denis imposes special conditions on any translocation programme. Because of the remoteness of the island, birds translocated here will remain isolated and cannot disperse to other islands in the group. Populations will necessarily be artificially managed and it is essential that any habitat management be initiated before birds are translocated. 2 Appendix 1. Plant species recorded from Denis (excluding seagrasses) Taxonomy of dicotyledons as given by Friedmann (1994). Of monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>1000 individuals observed); C = Common (100 - 1000 individuals observed); F = Frequent (10 - 100 individuals observed); Occasional (3 - 10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: PG = Grassland; W = Woodland; Sc = Scrub; BC = Beach Crest; Ma = Marsh; Cu = Garden. Previous records (in Notes): 1 = Stoddart and Fosberg, 1981; 2 = Fryer in Summerhayes, 1931; 3 = Fryer, 1910; 4 = collections by Jeffrey (no date), cited by Stoddart and Fosberg, 1981. Species Status Abund. Habitats Notes PTERIDOPHYTA Adiantaceae l Acrostichum aureum L. N A Ma Davalliaceae 2 Nephrolepis biserrata (Sw.) Schott N A WwW ~~ 1 1 Recorded 1977', not current survey. Same as N. biserrata? Nephrolepis cf. hirsutula (Forst.f.) Presl. Polypodiaceae 3 Phymatosorus scolopendria (Burm. f.) N A W Psilotaceae 4 Psilotum ?nudum Sw. N F W GYMNOSPERMAE 5) Cycas thuarsii Gaud. I R Cu Only in gardens ANGIOSPERMAE: Dicotyledons Acanthaceae 6 Asystasia sp. B (sensu Friedmann) 21 A G Asystasia bojeriana Nees y - - Recorded 1977', not current survey. Same as A.sp. B? i Pseuderanthemum carruthersii (Seem.) I F Cu Only in gardens Guillaumin Amaranthaceae 8 Achyranthes aspera (L.) DC. I A W,G 9 Alternanthera brasiliana (L.) O. Kuntze I O Cu Only in gardens 10 Amaranthus dubius Mart. ex Thell. I A G 11. Celosia argentea L. I R Cu Only in gardens Anacardiaceae 12. Spondias cytherea Sonn. I R Cu Only in gardens Annonaceae 13. Annona muricata L. I R Cu Only in gardens 14. Annona squamosa L. I FE W, Cu Apocynaceae WS Catharanthus roseus (L.) G. Don. I A G, W Species Status Abund. _ Habitats Notes 16 Nerium oleander L. I R Cu Only in gardens 17. = Ochrosia oppositifolia (L.) K. Schum. N R G 18 Plumeria rubra L. I O Cu Only in gardens 19 Thevetia peruviana K. Schum. I R Cu Only in gardens Araliaceae 20 Polyscias sp. I R Cu Only in gardens Asclepiadaceae 21 Calotropis gigantea (L.) Aiton f. I Fi GasciGu 22. ~=—‘Tylophora ?coriacea Marais N Cc W Balsaminaceae 23. ~~‘ Impatiens balsamina L. I O Cu Only in gardens 24 = Impatiens wallerana Hook. F. I Id Cu Only in gardens Bignoniaceae 25. Tabebuia pallida (Lind1.) Miers. I A W Boraginaceae 26 Cordia sebestena L. I O Cu Only in gardens il Cordia subcordata Lam. N CE W, BC 28 Tournefortia argentea L. f. N € BC Cactaceae 29 = Opuntia sp. I O Cu Only in gardens Caesalpiniaceae 30 = Caesalpinia pulcherimma (L.) Sw. It F Cu Only in gardens 31 Cassia/Senna sp. I F Cu Only in gardens 32. ~—Delonix regia (Hook.) Raf. I R Cu Only in gardens 33. ~~ Senna occidentalis (L.) Link I C PG 34 Tamarindus indica L. I O Cu, W Campanulaceeae 35. ~~ _Hippobroma longiflora (L.) G. Don I I Ma, G Capparidaceae 36 Cleome gynandra L. I F BEXG Caricaceae 37. ~—- Carica papaya L. I A W, Cu Casuarinaceae 38 Casuarina equisetifolia J. R. & G. Foster I A W Combretaceae 39 Terminalia catappa L. 2N A W Compositae 40 __ Bidens pilosa L. | ¢ G 4] Coreopsis lanceolata L. | S Cu Only in gardens 42 Melanthera biflora (L.) Wild 2N G G 43. Synedrella nodiflora (L.) Gaertn. ] A G 44 Tithonia diversifolia (Hemsl.) A. Gray I R Cu Only in gardens 45 Vernonia cinerea (L.) Less. I A W,G Convulvulaceae 46 Ipomoea hederifolia L. I O G 47 Ipomoea macrantha Roem. Et Schult. N (C W, Ma 48 Ipomoea obscura (L.) Ker Gawl. I F G, W 49 —_ Ipomoea pes-caprae (L.) R. Br. N C. BC, G Crassulaceae 50 Kalanchoe pinnata (Lam.) Pers. I c G 51 Kalanchoe blossfeldiana I R Cu Only in gardens __ =~ — 114 Species Status Abund. Habitats Notes Cucurbitaceae Cucurbita cf. maxima Duch. ex Lam. 52 Cucurbita moschata (Duch. ex Lam.) Duch ex Poir Mukia maderaspatana (L.) M. J. Roem. 53 Trichosanthes cucumerina L. Euphorbiaceae 54 = Acalypha indica L. 55. Acalypha wilkesiana Muell. Arg. 56 Codiaeum variegatum L. 57. Euphorbia cyathophora 58 Euphorbia hirta L. Euphorbia microphylla Heyne ex Roth. 59 Euphorbia prostrata Alt. 60 Jatropha pandurifolia Andtr. 61 Pedilanthus tithymaloides (L.) Pott. 62 Phyllanthus amarus Schumach. & Thonn. 63. = Phyllanthus maderaspatensis L. 64 ~= Phyllanthus pervilleanus (Baillon) Mill. Arg. 65 Ricinus communis L. Gesneriaceae 66 = Episcia cupreata (Hook.) Hanst. Goodeniaceae 67 Scaevola sericea Vahl. Guttiferae 68 Calophyllum inophyllum L. Hernandiaceae 69 Hernandia nymphaeifolia (Presl) Kubitzki Labiatae 70 Ocimum basilicum L. 71 Solenostemon cultivar Lauraceae 72 ~~ Cassythea filiformis L. 73. Persea americana Mill Lecythidaceae 74 ~~ ~Barringtonia asiatica (L.) Kurtz Lythraceae Pemphis acidula Forst. Malvaceae 75 Abutilon indicum (L.) Sweet 76 Gossypium hirsutum Vil Hibiscus rosa-sinensis L. 78 Hibiscus tiliaceus L. I : It O I O I A F | Fe I A I A 2 é I € I O I FE I F I ¢ N € I A I O N A N le N O O Ie N A I R N Ig Y % 21 Cc I S I Ie N x I R Recorded 1977', not current survey; extinct on Denis? Only in gardens Recorded 1910? (as Melothria maderaspatana) Only in gardens Only in gardens Recorded 1910°. = E. stodartii Fosberg? (Robertson, 1989) Only in gardens Only in gardens Only in gardens Only in gardens Recorded 1910”; Never occurred? Only in gardens 719 Malvaviscus arboreus Cav. Cu Only in gardens 115 Species Status Abund. Habitats Notes 80 Sida acuta Burm. f. I O G 81 Sida pusilla Cav. 2N A G 82 Thespesia populnea (L.) Soland. ex Correa N © W, BC Mimosaceae 83. Adenanthera pavonina L. I ( W 84 Leucaena leucocephala (Lam.) de Wit I C W Moraceae 85. Artocarpus altilis (Parkins.) Fosb. I O G, Cu 86 = Ficus benghalensis L. I ip G 87 Ficus elastica Roxb. I O Cu Only in gardens 88 Ficus lutea Vahl. N F W Moringaceae 89 Moringa oleifera Lam. H Je Cu, G Myrtaceae 90 = Psidium guajava L. R Cu Only in gardens 91 Syzygium samarangense (Bl.) Merr. & Perry R Cu Only in gardens Nyctaginaceae 92 Boerhavia repens L. 2N A G 93 Bougainvillea sp. cultivars I F Cu Only in gardens 94 ~— Mirabilis jalapa L. I F G, Cu 95 Pisonia grandis R. Br. N € W Oxalidaceae 96 = Averrhoa bilimbi L. I O GaCGu Papilionaceae 97 ~~ Canavalia cathartica N F BC Canavalia gladiata DC. I - = Recorded 19107: now extinct on Denis? 98 Crotalaria pallida Ait. (or C. trichotoma 21 € G Bojer, H. M) 99 Desmodium incanum DC. I A G, W 100 Gliricidia sepium (Jacq.) Walp. I F Cu Only in gardens Passifloraceae 101 Passiflora edulis Sims I O Cu Only in gardens 102 Passiflora foetida L. I O W 103. Passiflora suberosa L. A W,G Portulacaceae 104 Portulaca grandiflora Hook. In Cu Only in gardens 105 Portulaca oleracea L. N A G BE Rhamnaceae 106 Colubrina asiatica (L.) Brogn. N O W Rubiaceae 107 Guettarda speciosa L. N G BC 108 Morinda citrifolia L. 21 A W 109 Mussaenda sp. I R Cu Only in gardens Spermacoce repens (DC.) Fosb. and Powell ? - . Recorded 1977'; possibly Mitracarpus hirtus? (Robertson, 1989) Rutaceae 110 Citrus sp. I F G, Cu 111 9 Murraya koenigii (L.) Spreng. l F G, Cu Sapindaceae 112 Cardiospermum halicacabum.L. 2N O W 116 Species Status Abund. Habitats Notes Scrophulariaceae 113 Striga asiatica (L.) O. Kuntze 21 Ie G Solanaceae 114 Capsicum frutescens L. I R Cu Only in gardens 115 Physalis angulata L. I R W 116 Solanum americanum Mill. I O G, W 117. Solanum lycopersicum L. I F Cu Only in gardens 118 Solanum melongena L. I ig Cu Only in gardens 119. Solanum torvum Sw. I O G, W Surianaceae 120 Suriana maritima L. N Ie BE Turneraceae 121 Turnera angustifolia Miller I A W Verbenaceae 122. Lantana camara L. I F Sc, G, W 123. Phyla nodiflora (L.) Greene I A G, Ma 124 Stachytarpheta jamaicensis (L.) Vahl. I € G Zygophyllaceae Tribulus cistoides L. I - - Recorded 1910? (as T. terrestris); extinct on Denis? ANGIOSPERMAE: Monotyledons Agavaceae 125. Agave sisalana (Perr. Ex Engelm.) I (SC G 126 Furcraea foetida O G Amaryllidaceae 127. Crinum ?amabile Ker-Gawl. 2] ¢ G, Cu 128 Crinum asiaticum L. I F Cu Only in gardens 129 Zephyranthes rosea Lindl. I 6 G, Cu Araceae 130 = Alocasia macrorrhiza (L.) G. Don. I S W 131 Colocasia esculenta (L.) Schott I O Ma Commelinaceae 132. Commelina sp. 21 O Ma 133. Tradescantia spathacea Swartz I A Cu, W 134 Zebrina pendula Schnitzl. I R G Cyperaceae 135. Cyperus conglomeratus Rottb. N C BC 136 Cyperus rotundus L. ? A G 137 Cyperus sp. ? A G 138 Fimbristylis cymosa R. Br. u A G; BE 139 Kyllinga alba Nees. ey F W 140 Kyllinga polyphylla Willd. ex Kunth N F W 141 Mariscus dubius (Rottb.) Fischer N A G 142. = Mariscus ligularis (L.) Urb. 2N Fe G 143. Pycreus polystachyos (Rottb.) P. Beauv. ” R Ma Dioscoreaceae 144 Dioscorea alata L. I R W Gramineae 145. Brachiara umbellata (Trin.) W. D. Clayton N R Se 146 Cenchrus echinatus L. ? € G 147. Chloris ?barbata (L.) Sw. zy C G 148 Cymbopogon sp. I O Cu Only in gardens 149 _ Cynodon dactylon (L.) Pers. ? A Grube LT) Species Status Abund. Habitats Notes 150 Dactyloctenium ctenoides (Steud.) Bosser ? Cc G 151 Digitaria sp. (D. ?horizontalis Willd.) ? A G 152. Eleusine indica (L.) Gaertn. v A G 153. Enteropogon sechellensis (Baker) Dur. & N € G Schinz Enteropogon monostachyos (Vahl.) S. & E. z - - n.d.*; same as E. sechellensis? Eragrostis ciliaris (L.) R. Br. ? - - n.d.7 154 Eragrostis tenella (L.) P. Beuv. 2 A G 155 Eragrostis tenella var. insularis Hubb. ? C G 156 Lepturus sp. x A G, W 157 = Panicum maximum L. ? Ip G 158 Panicum ?repens L. e R G 159 Pennisetum polystachyon (L.) Schult. ? A G 160 Pennisetum sp. (purple var.) 21 O Cu Only in gardens 161 Rhynchelytrum repens (Willd.) C. E. Hubb. 2 ¢ G 162 Saccharum officinale L. I O Cu Only in gardens 163 Sporobolus virginicus (L.) Kunth. N Cc BC 164 Stenotaphrum dimidiatum (L.) Brogn. N A G Stenotaphrum micranthum (Des.) C. E. N - - n.d. Hubb. Liliaceae 165 Dianella sp. I R Cu Only in gardens 166 Dracaena reflexa Lam. N O Cu Only in gardens: introduced on Denis 167 Pleomele reflexa variegata I O Cu Only in gardens 168 Sansevieria thyrsifolia Thunb. I O Cu Only in gardens 169 Yucca sp. I O Cu Only in gardens Musaceae 170 Musa ?sapientum L. I ig Cu, W,G Orchidaceae 171 Vanilla planifolia Andrews I C W Palmae 172 ?Areca catechu L. I R Cu Only in gardens 173. Cocos nucifera L. N A RGA Sc, BC 174 Ptychosperma macarthurii (Wend1.) I R Cu Only in gardens Nichols. 175 Pritchardia pacifica I Is Cu Only in gardens 176 ?Thrinax sp. I R Cu Only in gardens Pandanaceae 177. = Pandanus sanderi Hort. ] R Cu Only in gardens 178 Pandanus sp. ] R Cu Only in gardens Typhaceae 179 Typha javanica Schnitzl. ex Zoll. N O Ma N 9 A 3 r Legend \s Contours \\ \\ &) Vegetation Plots m Marsh ® Building Beach 200 metres Figure 1. Félicité: physical, showing locations of vegetation plots. FELICITE BY MICHAEL J. HILL', DAVID R. CURRIE’, TERENCE M. VEL' and RODNEY FANCHETTE! GEOLOGY, TOPOGRAPHY AND CLIMATE Félicité, covering 268 ha, is the sixth largest of the granitic Seychelles Islands. At its highest point it reaches 231.5 m above sea level although most of the island is below 100 m (Table 1). Much of the island is high and rocky, made up of reddish-grey granites similar to those of Praslin (Braithwaite, 1984). In the north and east are two small low- lying “plateau” areas of more recent origin. The plateaux are made up of calcareous sediments, in part overlain by marsh and alluvial deposits. Large parts of the upland area are rocky with poor conditions for soil creation and retention. In glacis and rocky areas, soils are restricted to pockets between boulders. However, lateritic red earth soils are present over at least half of the hill area (D.OS., 1966). There are also small areas of alluvial soil associated with temporary stream beds. The plateaux (apart from marshy areas) are made up of Shioya soils. There are no permanent water bodies on the island, although seasonal stream beds exist (all were dry at the time of survey), and there is a small marsh on the plateau at Petite Anse (grid ref. CL 743 222); this too was without standing water at the time of the survey. The nearest large inhabited island is La Digue, 3.2km from Feélicité. Praslin is 8.6km away. Few weather records exist for Félicité, but rainfall data for 1958 and 1959 suggest that the island is drier than low-altitude sites on Praslin or Silhouette; mean annual total rainfall for these years was 1,428 mm on Félicité (Table 2). Annual rainfall at Praslin Grande Anse in 1958 was 1,847.1 mm (compared to 1,491.0 mm on Félicité) and mean annual total rainfall for 1958-9 on Silhouette (La Passe) was 1,609.4 mm (Seychelles Meteorological Office, Unpublished data). Table 1. Area of Félicité by altitude (calculated from map published by UK Directorate of Overseas Survey/Seychelles Government, 1980). Altitude range (m. asl.) Area (ha) Percentage total area ' Nature Seychelles, PO Box 1310, Mahé, Seychelles. Email: birdlife@seychelles.net 120 Table 2. Félicité: monthly rainfall (mm), 1958-1959. (Data: National Meteorological Services, Seychelles, unpublished data). Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year 1958 Lege Oe 8 4e3re OMe AN 93099387 le 53.55 S255 21.8 48:8 1133) 20743 S149ik0) 1959 26915 46:5 (84:1 11285, SW | 22:67 2216), 42:2, 206.3) 11210 ISIS ISG SRI SEO. mean, 223.3 65:4 92:6 77:3 18358 2049" 38.0) 373) 11451 80.4 152.6 158.7 1428.0 HISTORY Early records of Félicité suggest that it was a rather dry barren island. The Marion Dufresne expedition of 1768 (prior to settlement of the Seychelles) visited the island, although records were restricted to the exploitable resources. It was noted that the island was not as well wooded as La Digue, and that timber was poorer (Lionnet, 1984). In 1787, the island was said to be well wooded with bwa-d-nat Mimusops sechellarum and takamaka Calophyllum inophyllum (the latter on the coast only), with endemic giant tortoises on the hill, but lacking any fresh water in the dry season (Malavois, 1787 in Fauvel, 1909). Following the permanent settlement of the Seychelles, Félicité became a private estate. In the nineteenth century, the estate was abandoned and annexed by the colonial government (in Mauritius) before 1866. Timber from the island was used by the colonial government (Newton, 1867). When the island was visited by Edward Newton in 1866, rats and cats had already been introduced (Newton, 1867). Although there was still “very considerable forest” on the south west side of the island, Newton found only two species of land bird, the Seychelles sunbird Nectarinia dussumieri and feral chickens Gallus gallus. In contrast, the nearby island of Marianne (still predator-free) had 12 species of Seychelles endemic birds. At that time, Félicité was leased to small farmers, with the government retaining control of forest reserves over part of the island for the protection of timber and water supplies. In 1895 a 30-year lease was given to Harold Baty, who extended the existing coconut plantations. In 1898, Harold Baty wrote (in a letter to the Administrator of Seychelles) that the island produced 30,000 coconuts per month and that he had introduced “‘valuable plants” to the island including cloves Syzygium aromaticum, rubber Hevea brasiliensis, bamboo (probably Bambusa vulgaris), raffia Raphia farinifera, vacoa Pandanus utilis and pepper Piper nigrum. He added that experiments with coffee (Coffea liberica) had been unsuccessful (letter of 23/10/1898 in Seychelles Archive). In 1908, Félicité was reputed to support 100—150 acres (60.8 ha) of native forest, dominated by Mimusops sechellarum and Intsia bijuga, with over 1,000 trees reaching 18 inches (46 cm) in diameter (Anon. 1908). In 1910, the lessces applied for the right to fell some of the forest trees remaining on the island and were granted the use of 130 acres (52.6 ha) of forest land, the government reserving the right to purchase all timber felled. This area was later planted with coconuts by the lessee. In 1921-24 the government itself felled takamaka trees on approximately 100 acres (40.5 ha). In 1923, representatives of the lessee illegally cut timber (Mimusops and Intsia) within the government reserve, some being removed to Grande Soeur Island 121] (which was managed by the same lessee, the Society des Iles Soeurs) and some sent to Mauritius. The trees were regarded as valuable as they were “getting extremely scarce”. In 1927, the lessee Louis Bessin applied for, and received, permission to fell most of the forest trees remaining in the reserve areas. An area of 29 acres (11.7 ha) at Glacis Rouillé was to be left untouched. In addition, he introduced herds of free-roaming cattle and goats. In 1934, the Director of Agriculture, Mr P. R. Dupont, visited Felicité and found that the forest reserve had been exhausted and, with the exception of a few hundred trees left standing, was only fit for firewood. Undercropping had inhibited natural regeneration and encouraged erosion, and even trees bordering streams had been felled. He suggested replanting with Albizzia (probably Paraserianthes falcataria), sangdragon Pterocarpus indicus, bois de table Heritiera littoralis and agati Adenanthera pavonina, which had little commercial value but would survive on the dry island. It is unclear whether these suggestions were acted upon. By 1959, coconuts were planted throughout the island although some takamaka Calophyllum inophyllum, kapisen Northea hornei, gayac and bwa-d-nat survived (Swabey, 1961). Although goats appear to have become extinct on the island (as elsewhere in the granitic islands), it appears that the free-ranging cattle introduced in the 1930s persisted until the late 1980s, when they were culled (island manager, pers. comm.). In 1984, there were 33 animals (Racey & Nicoll, 1984). Currently the island is managed as a small and exclusive resort with a staff of around ten permanent inhabitants. Settlement is now restricted to the plateau area to the north east of the island and many of the buildings dating from the plantation period are now abandoned. Some coconuts are still harvested from the palms (particularly around the settlement), and plateau vegetation is managed, but the majority of the former plantation has been abandoned. FLORA AND VEGETATION Flora A total of 187 plant species were recorded on Félicité, including 11 ferns, one gymnosperm (cultivated), and 175 angiosperms (Appendix 1). Of the angiosperms, 86 (49.1%) were introduced, 73 (41.7%) native and 23 of these (13.1% of total) endemic. Compared to other islands on the survey, the proportion of the total flora made up of introduced species was small while the proportion of Seychelles endemics was high (for the total Seychelles flora, around 54% is introduced and 9% endemic: Procter, 1984). The high proportion of endemic species reflects Félicité’s topography and history. For much of the nineteenth and twentieth centuries, parts of the island were protected as forest reserves (see above). The size of the island and inaccessibility of some areas allowed a number of endemic species to survive the expansion of agriculture on the island. One endemic species, coco-de-mer Lodoicea maldivica, was introduced to Felicite (its natural range appears restricted to Praslin, Curieuse, and nearby islets). However, the Felicite coco-de-mer population includes mature fruiting palms and young plants suggesting that it is established on the island. 122 Of the introduced plants established on Feélicité, 13 are invasive weedy species. Among the most successful alien plants on Félicité were cocoplum Chrysobalanus icaco and cinnamon Cinnamomum verum, which are the most widespread and invasive woody weed species on the smaller islands of the granitic Seychelles (Hill, 2001). A small proportion of the total flora (around 23 species, 13.1%) consisted of ornamental species (most of recent introduction) confined to the landscaped areas around the hotel buildings. Twelve species recorded in previous botanical collections on Félicité were not recorded in the current survey. Most of these species were probably still present on the island but were not discovered in the short time of the survey. One previous record is doubtful, however: bwa bannan Gastonia crassa was recorded by Procter (1974), who did not record G. sechellarum from Félicité. In his revision of the genus Friedmann (1994) records G. sechellarum sechellarum but not G. crassa from Félicité. When not in flower, these Gastonia species can be difficult to differentiate. The addition of 12 species brings the flora of Félicité to 199 species, 26 of which are endemic. Vegetation The extent of major vegetation types on Félicité is shown in Table 3, and Figure 2. The vegetation is dominated by hill woodland rich in native species, scrub (mainly the introduced cocoplum Chrysobalanus icaco) and glacis (bare rock with a number of endemic species but heavily invaded by Chrysobalanus icaco in many places). Coconut plantations and fruit tree orchards are now largely abandoned and overgrown with the exception of coconut groves around the inhabited area. Invasive coconut regrowth occurs particularly along the coastal strip. The 10 vegetation plots completed were carried out in hill woodland/scrub (giacis was avoided). Only 1,000 m’ of the island fell within the vegetation plots (0.04% of the total island area, 0.08% of Félicité’s upland forest). Fifty-two species were recorded (0.052 species m”), of which the majority were native or endemic (28 species, 53.8% of total species, were native or endemic). In the tree layer, 12 species were recorded, nine of which (75%) were native or endemic. Fifty-three individual trees were recorded, giving a mean density of 530 trees ha’. Almost half of all trees recorded belonged to the two most abundant species, both native; takamaka Calophyllum inophyllum (15 trees, 28.3% of all trees) and bwa dir rouz Canthium bibracteatum (11 trees, 20.8% of all trees). Introduced species made up only a small proportion of the canopy layer (only 17%), the commonest being cashew Anacardium occidentale. All tree species recorded showed signs of natural regeneration, and were represented in the shrub and/or herb layer. In the shrub layer the most widespread species were Canthium bibracteatum (represented in nine of 10 plots), Chrysobalanus icaco (in eight plots), Cocos nucifera (in eight plots) and Allophyllus pervillei (in six plots). Of these species, Cocos was the most dominant locally; in plots where it occurred, Cocos formed on average 17.9% of shrub layer coverage (compared to Canthium, 9.5%; Chrysobalanus, 9.8%; and Allophyllus, 10.3%). Table 3. Extent of major vegetation types, Feélicité. Hill > 10 masl Plateau < 10 masl Vegetation type Woodland (predominantly native) Coconut plantation Scrub (Introduced) Bare rock Woodland (predominantly native) Coconut plantation Coconut with regeneration Freshwater marsh Beach crest vegetation Grassland/garden Bare rock 123 124 Legend:vegetation types HB Bare rock [] Grassland, garden Scaevola Cocoplum scrub Exotic woodland Native woodland Coconut with scrub Exotic scrub Beach crest PZ | 200 metres Figure 2. Félicité vegetation. Ds INVERTEBRATES Pitfall Trapping Pitfall trap assemblages were similar in size (number of individuals) to the overall mean for the season. The mean number of individuals per five traps was 72, compared to the mean for the season (all islands): 68.2 individuals per five traps. However, the major part of each assemblage was made up of ants; mean assemblage size excluding ants was 8.6 individuals (compared to the seasonal mean of all islands: 15.12). Abundance of invertebrates other than ants was relatively low. Assemblages were dominated by the introduced crazy ant Anoplolepis gracilipes. This species, introduced to the Seychelles in the early 1960s, occupied 60% of the area of Félicité in 1994. It is a domestic and agricultural pest with effects on natural ecosystems that are difficult to gauge (Haines et al., 1994). Of 720 individual invertebrates caught, 567 (78.8%) were A. gracilipes (Fig. 3). Of the total assemblage 86.8% was made up of ants, 3.2% earwigs (Dermaptera), 3.1% snails, and 2.9% flies (Diptera), mainly larvae. A. gracilipes has a major effect on the composition of ground invertebrate communities and, at high densities, may cause changes in the vegetation composition of islands (Hill, in prep). Lepidoptera ~ GMollusca larvae ———___ Anoplolepis gracilipes Figure 3. Taxonomic composition of pitfall assemblages from Feélicité. Only invertebrates of body length > 2 mm included. ‘Others’ group includes Blattodea, Diptera (adults), Hemiptera, Myriapoda and Orthoptera. Leaf-insect Counts Leaf-insect counts were carried out for 11 tree and shrub species (Table 4). The highest leaf counts were for the introduced Citrus due to high levels of infestation of mealy bugs and scale insects (both tended by ants) on these species. The endemic Erythroxylum sechellarum also had particularly high values for invertebrate densities. 126 Table 4. Density of invertebrates on foliage, Feélicite. : =D Mean insects m Mean insects leaf”! No. leaves counted Species Introduced species Anacardium occidentale 150 0.207 SEO? Chrysobalanus icaco 100 0.030 8.75 Citrus sp. 200 0.290 198.21 Mangifera indica 150 0.033 5.76 Native species Allophyllus pervillei 150 0.093 293 Calophyllum inophyllum 500 0.232 26.37 Canthium bibracteatum 450 0.033 15.42 Erythroxylum sechellarum 50 0.060 27.84 Memecylon elaeagni 100 0 0 Paragenipa wrightii 50 0.420 63.09 ?Status unknown Morinda citrifolia Malaise Trapping and Other Methods Two malaise traps were in place for three nights each in hill woodland habitats. Malaise trap assemblages were large (179 and 185 individual invertebrates) and included members of nine invertebrate orders. The dominant orders were the Lepidoptera (48.4% of all individuals), Hymenoptera (19.8%) and Diptera (17.3%). The majority of taxa collected have yet to be identified to species level. A number of other invertebrate species were identified and are shown in Table 5. Table 5. Invertebrate species identified, Félicité. 127 Order Family Species Notes Mollusca: Gastropoda Achatinidae Achatina fulica (Bowditch, 1822) Introduced species, abundant Achatina pantera Ferrusac, 1822 Introduced species, abundant Subulinidae Subulina octona Bruguiére, 1792 Crustacea: Decapoda Coenobitidae Coenobita brevimanus Dana, 1852 Gecarnicidae Cardisoma carnifex (Herbst, 1784) Occasional, plateau Ocypodidae Ocypode ceratophthalmus (Pallas, 1772) | On beach and beach crest Ocypode cordimana Desmarest, 1825 Myriapoda Trigoniulidae = ?Spiromanes braueri (Attems, 1900) In pitfall traps Insects: Odonata Anisoptera Diplacodes trivialis (Rambur, 1842) Observed flying over glacis Lepidoptera Nymphalidae = Melanitis leda africana (Linnaeus, 1758) In hill woodland Hypolimnas misippus (Linnaeus, 1764) Lycaenidae Leptotes pirithous Linnaeus, 1767 Zizeeria knysna (Trimen, 1862) In grassland, mainly on plateau Hesperiidae Borbo sp. Coleoptera Buprestidae Belionota prasina Thunberg, 1789 Caught in Malaise trap, hill woodland Rhipiceridae Callirrhipis philiberti Fairemaire, 1891 Endemic. Caught in Malaise trap, hill woodland Hymenoptera Anthophoridae Xylocopa caffra (Linnaeus, 1767) Apidae Apis mellifera adansoni Latreille, 1804 Formicidae Anoplolepis gracilipes (Smith, 1857) Abundant on vegetation and in leaf litter. In pitfall traps Cardiocondyla emeryi Forel, 1881 In pitfall traps Monomorium ?floricola (Jerdon, 1851) In pitfall traps Odontomachus troglodytes Santschi, In pitfall traps 1914 Tapinoma melanocephala (Fabricius, Occasional, in pitfall traps 1793) Technomyrmex albipes (Smith, 1861) Abundant on vegetation and in leaf litter. In pitfall traps Vespidae Polistes olivaceus (de Geer, 1773) Phasmatodea = Phasmatidae Carausius sechellensis (Bolivar, 1895) Collected in sweep samples VERTEBRATES Reptiles A total of eight species (six lizards, one tortoise and one snake) was observed (Table 6), but there are probably further species present that were not recorded. At least two of these (Aldabra giant tortoise and Brahminy blind snake) are introduced species. Giant tortoises, presumably a species of the granitic Seychelles, were present in the late eighteenth century but became extinct before 1875 (Bour, 1984). Neither of the Seychelles’ two endemic snakes (Nussbaum, 1984a) was observed although they are likely to occur here given the island’s size and relatively undisturbed nature. 128 In addition to land reptiles, at least one marine turtle appears to nest on the island. A single hawksbill Eretmochelys imbricata (L.) was observed on the beach at Grand’ Anse. Table 6. Reptiles observed on Félicité. Status: E =endemic, I = introduced, N = native (in central Seychelles). Family Species Status Gekkonidae —Ailuronyx seychellensis (Dumeril & Bibron, 1836) bronze-eyed gecko 8) Phelsuma sundbergi Rendahl, 1939 day gecko Ig; Phelsuma sp. (?P. astriata Tornier, 1901) day gecko Ig, Urocotyledon inexpectata (Steiner, 1893) sucker-tail gecko Ig Scincidae Mabuya sechellensis (Dumeril & Bibron, 1836) Seychelles skink 18) Janetaescincus braueri (Boettger, 1896) or Pamelaescincus — burrowing skink id gardineri Boulenger, 1909 Testudinidae Geochelone gigantea (Schweigger, 1812) Aldabra giant I tortoise Typhlopidae Rhamphotyphlops braminus (Daudin, 1803) Robb, 1966 Brahminy blind I snake Birds Extensive surveys of the island were carried out for two endemic species, Seychelles scops owl Otus insularis and Seychelles black paradise flycatcher Terpsiphone corvina The available map of Félicité (Directorate of Overseas Survey UK/Seychelles Government, 1980) is plotted on a 100 m x 100 m grid. Forty-one of these squares were selected randomly representing 13% of the island's area. Where the random squares consisted exclusively of glacis, or were coastal with less than 50% land, they were excluded and other squares were selected. Both sexes of Seychelles black paradise flycatcher respond well to the playback of male song and individuals frequently approach to within a few metres of the recorder. Male song was played continuously for five minutes in each of the 41 randomly selected squares (11-17 November 1999, 0830h-1600h) and any response noted. In addition, we also noted the presence of any other bird species detected during the five minutes of playback. Scops owls also respond well to playback of conspecific calls, often approaching to within a few metres of the recorder. Scops owl calls were played at c.200 m intervals at seven points for 10 minutes along a transect on 12 November (1820-2030h). No flycatchers were observed in any of the random squares in response to the playback and, furthermore, none were observed in the extensive coverage of island during the sampling. The Seychelles sunbird Nectarina dussumieri was the most common species observed in the random squares occurring in 31 squares (76%), followed by the blue pigeon Alectroenas pulcherrima found in 22 squares (54%) and the common mynah Acridotheres tristis found in 10 squares (24%) (Table 7). In six squares (15%), no birds were detected. There was no response to the scops owl playback. WwW Table 7. Bird species recorded during the sampling of 41 random squares (each 100 m x 100 m) on Félicité 8th-14th November 1999. Percentages given in parentheses. Species Nectarina dussumieri Alectroenas pulcherrima Acridotheres tristis Streptopelia picturata Foudia madagascariensis Geopelia striata Butorides striatus No. squares species recorded Seychelles sunbird 31 (76) Seychelles blue pigeon 22 (54) common mynah 10 (24) Madagascar turtle dove 4 (10) Madagascar fody 2S) barred ground dove @) reen-backed heron ine Few endemic land bird species have ever been recorded on Félicité (Table 8). In 1866, only one endemic species was recorded (Newton, 1867). Diamond (1984) suggests that up to six endemic species may have occurred here although one of the species he lists as present (Seychelles bulbul Hypsipetes crassirostris) was not recorded in the current survey and Shah et al. (1998) suggest that it has never been recorded on Feélicité. Reports of the Seychelles scops owl (Diamond and Feare, 1980) have not been confirmed, and it is possible that the records were of barn owl Tyto alba.The Seychelles kestrel Falco araea was reported by Shah ef al. (1998), but was not observed in the current extensive survey; it seems likely that the species is again extinct on the island. There are various records of the black paradise flycatcher on the island from 1936 to the 1980s (Collar and Stuart, 1985), but recent records probably refer to vagrants from La Digue (Diamond, 1984). Table 8. The current and prior status of endemic land-birds of the inner Granitics on Félicité. Current status based on observations from visit to the island 8-14"" November. Prior status based on Shah ef al. (1998). Species Falco araea Alectroenas pulcherrima Coracopsis nigra barklyi Otus insularis Collocalia elaphra Hypsipetes crassirostris Copsychus sechellarum Acrocephalus sechellensis | Seychelles warbler Terpsiphone corvina Nectarinia dussumieri Zosterops modestus Foudia sechellarum Seychelles fody Current status Prior Status Seychelles kestrel Absent 2 Seychelles blue pigeon Common 2 Seychelles black parrot Absent | Seychelles scops owl Absent 3 Seychelles swiftiet Absent 3 Seychelles bulbul Absent l Seychelles magpie-robin Absent l Absent l Seychelles black paradise flycatcher Absent 3 Seychelles sunbird Very common 2 Seychelles white-eye Absent l Absent | Prior status: 1 = never recorded; 2 = present; 3 = bred or present in the past but not recorded in recent years. 130 Three species of seabird were observed; two of these (white-tailed tropicbird Phaeton lepturus and fairy tern Gygis alba) may breed on Félicité. A third species (a frigate bird Fregata sp.) was observed flying over the island. Mammals Four mammal species were observed in the course of fieldwork, one endemic (the Seychelles fruit bat Pteropus seychellensis) and three introduced (domestic dog Canis familiaris, domestic and feral cats Felis catus and ship rats Rattus rattus). The large herd of feral cattle (Bos taurus) previously recorded on Félicité (Racey & Nicoll, 1984) was exterminated in the late 1980s or early 1990s. Rodent trapping was carried out with two traplines, one on the plateau and one running through hill glacis/cocoplum scrub habitat. A total of 112 trap-nights were carried out and 31 individual rats caught, giving a capture rate of 27.68 rats per 100 trap- nights (unadjusted) or 33.33 per 100 trap-nights (adjusted to account for the effects of closed traps: Cunningham and Moors, 1996). This rate of trapping was slightly lower than average for the season (overall mean for all islands in season 1s 33.64 rats per 100 trap-nights unadjusted). Rattus rattus is a widespread species in Seychelles that can have a significant impact on bird populations as it is a proficient climber (Racey and Nicoll, 1984). DISCUSSION Félicité is a relatively large high island supporting a large area of predominantly native woodland. In recent history, native woodland has been more extensive but clearance for timber and coconut plantation in the twentieth century reduced the area of this habitat. Many endemic and native plant species survived the enlargement of plantations (Swabey, 1961) and the economic decline of coconut plantations, as elsewhere in the granitic islands, has already allowed partial recovery of semi-natural woodland. On the plateaux, coconut plantations are still actively managed for production. While the upland forest retains a “natural” appearance, the composition appears to be very different from that recorded in the early twentieth century. The dominant species recorded in vegetation plots in the current survey (takamaka and Canthium bibracteatum) were native but the two species regularly recorded in the early twentieth century (/ntsia bijuga and Mimusops sechellarum) were not recorded in the tree layer of plots. /ntsia was recorded in the shrub layer of one plot, Mimusops was not observed although probably still present on the island. In addition to the native species recorded, the upland woodland contains a number of introduced plant species, the establishment of which has probably been favoured by previous woodland clearance including cinnamon and cocoplum. Takamaka is a long- lived shade-bearing tree (Friedmann, 1986) that may compete effectively with invasive introduced species. However, takamaka is threatened throughout the granitic islands by the current outbreak of takamaka vascular wilt disease (Ivory et al., 1996). The disease is not yet present on Félicité although it occurs on neighbouring islands, including Praslin and La Digue (Hill et a/., submitted), and it seems that, with time, it will reach most 131 islands in the archipelago that have takamaka. If and when it invades Félicité, tree death and the subsequent opening of the forest canopy are likely to encourage the spread of a number of trees and shrubs, largely invasive alien species. The invasive alien crazy ant Anoplolepis gracilipes is widespread on the island. Unfortunately it was not possible to compare the current extent or severity of the crazy ant infestation with that recorded by previous workers (see Haines et al., 1994), but it seems unlikely that the infestation has progressed beyond the 60% of the island recorded in the 1990s. Anoplolepis undoubtedly affects the invertebrate communities of islands where it is present although, on (relatively) complex islands such as Félicité, ant-free areas are likely to occur and it would seem unlikely that the presence of ants would drive any invertebrate species to extinction. The early introduction of alien mammals probably accounts for the small number of endemic vertebrates recorded on the island. CONSERVATION RECOMMENDATIONS Félicité has great potential for conservation. Compared to the other small- and medium-sized islands considered in the island assessment process, it is relatively large with large areas of semi-natural woodland. Its existing biodiversity value for groups other than birds is high: it supports a large number of endemic plants, and some of the invertebrate species identified are also endemic. The limited traffic to and from the island would reduce the potential for reintroduction of alien species (once eradicated) and the island’s small human population has a relatively limited effect on the island environment. Few endemic birds have been recorded on Feélicité but this is probably the result of the early introduction of rats and cats. It seems highly likely that a number of endemic Species occurred in the past and rehabilitation would allow the introduction of several bird species. The predominance of native tree species, which support a large number of invertebrates, suggest that several endemic bird species which feed primarily on insects among foliage could survive on the island in the absence of predators. Examples include Seychelles warbler, white-eye, and black paradise flycatcher. Because of the large size of the island, more than one of these species could be considered for introduction. However, the continued spread of takamaka wilt disease between islands threatens the island’s takamaka and, if the disease were introduced, would necessitate extensive habitat rehabilitation work (including replanting of other native trees) before reintroductions could occur. Seychelles magpie-robins feed primarily on invertebrates on the ground. Initial pitfall trap data suggest that invertebrate densities, excluding ants, at the time of sampling were relatively low so the island would not be ideal for introduction of the species. While these pitfall data were from a limited number of sites (10) and trapping was carried out at the end of a particularly dry season, it is certainly the case that hill habitats tend to have lower densities of ground invertebrates than do plateaux. The plateau area of Felicite is small and heavily modified and a large area of the island is made up of glacis, which is of little value to magpie-robins. Although the island is large, population densities of magpie- robins on Félicité would be lower than those on islands with large plateaux. Therefore, 132 the island should not be considered a priority for introduction of magpie-robins and further study of potential food supply would certainly be necessary if the reintroduction of magpie-robins was considered desirable. In order for the conservation potential of the island to be realised, the following major actions would be needed: e Eradication of alien mammals (rats and cats); e Removal of invasive alien plants, and coconuts (cocoplum and cinnamon are among the most troublesome alien weeds present but there are also large numbers of fruit trees including citrus and mango); e Further research, especially on food supply for Seychelles magpie-robin; e Monitoring of crazy ant population density and extent of infestation; and e Monitoring of takamaka wilt disease. 133 Appendix 1. Plant species recorded from Félicité (excluding seagrasses) Taxonomy of dicotyledons as given by Friedmann (1994). Of monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>1000 individuals observed); C = Common (100 — 1000 individuals observed); F = Frequent (10 — 100 individuals observed); Occasional (3 — 10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: Cu = Cultivated area (includes garden weeds and ornamentals); PG = Plateau grassland (includes coconut plantation); PW = Plateau woodland; HW = Hill Woodland; HSc = Hill Scrub; HG = Hill Grassland (includes coconut plantation); Gl = Glacis; BC = Beach Crest; Ma = Marsh. Previous records from 'Procter, 1974; ? Averyanov & Kudriavtzeva, 1987; ‘ Robertson, 1989; *Carlstrom 1996a. Species Status | Abund. Habitats Notes PTERIDOPHYTA Adiantaceae 1 Acrostichum aureum L. N C Ma 2 Pellaea ?doniana Hooker N C HW, Gl Davalliaceae 3 Davallia denticulata (Burm.) Mett. N C HW 4 Nephrolepis biserrata (Sw.) Schott N A HW Gleicheniaceae 5 Dicranopteris linearis Burm. N FS Gl Lomariopsidaceae 6 ?Bolbitis bipinnatifida (Mett. Ex Kuhn) Ching 2N R PSe Lycopodiaceae 7 Lycopodium cernuum L. 2N R Gl Parkeriaceae 8 Ceratopteris cornuta (Pal.) Lepr. N E Ma Polypodiaceae 9 Phymatosorus scolopendria (Burm. f.) N A HW, PW Psilotaceae 10 = Psilotum nudum Sw. N O HW Selaginellaceae 11 = Selaginella sp. N O HW GYMNOSPERMAE 12. Cyceas thuarsii Gaud. Ik R Cu Only in gardens ANGIOSPERMAE: Dicotyledons Acanthaceae 13. ~~ Asystasia sp. B (sensu Friedmann) 2 A PG, HW, Gl 14 = Justicia gendarussa Burm. f. 21 R PG Anacardiaceae 1S. = Anacardium occidentale L. I A Gl, HSc, HW 16 Mangifera indica L. ] A HW 17 ~~ Spondias cytherea Sonn. I R PG Annonaceae 18 Annona muricata L. l O HW 134 Species Status | Abund. Habitats Notes Apocynaceae 19 Catharanthus roseus (L.) G. Don. I C Gl 20 = Ochrosia oppositifolia (L.) K. Schum. N F HW 21 = Plumeria obtusa L. I R Cu Only in gardens 22. = Plumeria rubra L. I O Cu Only in gardens 23 Tabernaemontana coffeoides Boj. ex. A. DC. N © HW, HSc 24 ~—- Thevetia peruviana K. Schum. I O Cu Only in gardens Araliaceae Gastonia crassa (Hemsl.) F. Friedmann E - - Previous record’; in error for G. sechellarum? 25 Gastonia sechellarum (Baker) Harms. I € HW, HSc 26 ~~ Polyscias sp. I O Cu Only in gardens Asclepiadaceae 27. ~~ Sarcostemma viminale (L.) Alton N O Gl Bignoniaceae 28 Tabebuia pallida (Lindl.) Miers. I C PW Bombacaceae 29 Ceiba pentandra (L.) Gaertn. I R Cu Only in gardens Boraginaceae 30 = Cordia subcordata Lam. N F BC Si Tournefourtia argentea L. f N R BC Brexiaceae 32 ~=Brexia madagascariensis (Lam.) Ker Gawl. E (ss) O HW subsp. microcarpa (Tul.) F. Friedmann Cactaceae 33. = Opuntia vulgaris Mill. I R PG; Gi 34 ~— Rhipsalis baccifera (J. Mill.) Stearn N R Gl Caesalpiniaceae 35 Caesalpinia bonduc (L.) Roxb. N R HW 36 = Caesalpinia pulcherimma (L.) Sw. I R Cu Only in gardens 37. ~— Intsia bijuga (Colebr.) O. Kuntze N Ja HSc, HW 38 Senna occidentalis (L.) Link R PG 39 Tamarindus indica L. I F PG, HW Capparaceae Cleome viscosa L. I - - Previous record” Caricaceae 40 = Carica papaya L. I O Cu, PG, HW Casuarinaceae 4] Casuarina equisetifolia J. R. & G. Foster I Ei Gl Chrysobalanaceae 42 Chrysobalanus icaco L. I A HW, HSc, Gl Combretaceae 43 Terminalia catappa L. 2N A BC, HW Compositae 44 Coreopsis lanceolata L. I R Cu Only in gardens 45 Elephantopus mollis H. B. K. I le HW 46 Emilia sonchifolia (L.) Wight I K PG 47 Melanthera biflora (L.) Wild 2N O PG 48 Vernonia cinerea (L.) Less. I A PG Convulvulaceae 49 _ Ipomoea batatas (L.) Lam. I O Cu Only in gardens Species Status Abund. 50. = Ipomoea obscura (L.) Ker Gawl. 51 Ipomoea macrantha Roem. & Schultes 52. Ipomoea mauritiana Jacq. 53. Ipomoea pes-caprae (L.) R. Br. Crassulaceae 54. —- Kalanchoe pinnata (Lam.) Pers. Ebenaceae 55 Diospyros seychellarum (Hiern.) Kosterm. Erythroxylaceae 56 Erythroxylum sechellarum O. E. Schulz Euphorbiaceae 57 Acalypha hispida Burm. f. 58 Acalypha wilkesiana Muell. Arg. 59 Euphorbia hirta L. 60 Euphorbia pyrifolia Lam. 61 Euphorbia thymifolia L. Excoecaria benthamiana Hemsl. 62 Jatropha curcas L. 63 Jatropha pandurifolia L. 64. Manihot esculenta Crantz 65 = Pedilanthus tithymaloides (L.) Poit. 66 Phyllanthus acidus (L.) Skeels 67 = Phyllanthus sp. Flacourtiaceae Aphloia theiformis (Vahl.) Benn ssp. madagascariensis (Clos.) H. Perr. var. seychellensis (Clos.) Friedmann 68 Ludia mauritiana Gmel. var. sechellensis F. Friedmann Goodeniaceae 69 Scaevola sericea Vahl. Guttiferae 70. ~~ Calophyllum inophyllum L. Hernandiaceae 71 ~~ -Hernandia nymphaeifolia (Pres) Kubitzki Labiatae 72 ~~ ~-Plectranthus amboinicus (Lour.) Spreng. Lauraceae 1 Cinnamomum verum Presl. Lecythidaceae 74 ~~ ~Barringtonia asiatica (L.) Kurtz Loganiaceae iS Strychnos spinosa Lam. Malvaceae 76 ~~ Hibiscus rosa-sinensis L. Hi Hibiscus tiliaceus L. 78 Sida acuta Burm. f. 79 ~~ Sida cordifolia L. 80 Thespesia populnea (L.) Soland. ex Correa Melastomataceae 81 Memecylon elaeagni Blume I E N (SC 21 (SG N A I Cc 8 C Ig C I R I Fe I A N C I O E = I R I R J O I O I R I ( E £ (var.) 3 A (var.) N € N A N Ie wl C I O N O ] (C ] O N EB ] F 2N R N F E A Habitats PG, HW HW HW, HG BC HW HW, HSc HW, HSc HW BC HW, BC BC Gl HW BC HSc, PG, HW Cu BC PG Gl BC HSc, HW 135 Notes Only in gardens Only in gardens Previous record* Only in gardens Only in gardens Previous record* } Only in gardens 136 Species Status Abund. Habitats Notes Meliaceae 82 Xylocarpus moluccensis (Lam.) Roem. N F BE Mimosaceae 83. Adenanthera pavonina L. I C HW 84 Mimosa pudica L. A PG, HSc Moraceae 85 Artocarpus altilis (Parkins.) Fosb. I F PG 86 Artocarpus heterophyllus Lam. I R PG Ficus bojeri Baker N - - Previous record! 87 Ficus lutea Vahl. N C HW, Gl, PG 88 Ficus reflexa Thunb. ssp. seychellensis (Baker) __ E (ss) C HW, Gl, PG Berg 89 ~~ Ficus rubra Vahl. N 13 Gl, HW Moringaceae 90 = Moringa oleifera Lam. I iF PG, HW Myrtaceae 91 ~~ Psidium guajava L. I O PRGyHSe 92 Syzygium samarangense (BI.) Merr. et Perry I R Cu 93 = Syzygium wrightii (Baker) A. J. Scott K Gl, HW Nyctaginaceae 94 ~Bougainvillea sp. cultivars I O Cu Only in gardens Onagraceae Ludwigia erecta (L.) Hara i - - Previous record? 95 Ludwigia octovalvis (Jacquin) Raven al F Ma Oxalidaceae 96 = Averrhoa bilimbi L. I O HW Papilionaceae 97 Abrus precatorius L. 2N A HW, HSc 98 Canavallia cathartica Thouars. N F BC, PG 99 Dendrolobium umbellatum (L.) Benth. N O BC 100 Desmodium incanum DC. I A PG, HSc 101 Desmodium triflorum (L.) DC. I G PG 102. Gliricidia sepium (Jacq.) Walp. I 2 PG, HW 103 Indigofera tinctoria L. I C PG 104 Mucuna gigantea (Willd.) DC. N O HW 105 = Teramnus labialis (L.) Spreng. I € PG, HSce 106 Vigna marina (Burm.) Mert. N O BC, PG Passifloraceae 107 Passiflora foetida L. Is HW 108 Passiflora suberosa L. A PG, HSc, HW Portulacaceae 109 Portulaca oleracea L. 2N R PG Rhamnaceae 110 Colubrina asiatica (L.) Brogn. F BC, HW N Rubiaceae 111 Canthium bibractatum (Baker) Hiem. N A 112 Mitracarpus hirtus (L.) DC. I Ja 113. Morinda citrifolia L. 21 C HW, Gl 114 Paragenipa wrightii (Baker) F. Friedmann 3 € Pentodon pentandrus (Schumach. & Thonn.) I - Previous record? 115. Tarenna sechellensis (Baker) Summetrh. E Rutaceae (C 116 Citrus spp. I A HW, Cu Species Sapindaceae 117. Allophyllus pervillei Blume 118 Dodonea viscosa Jacq. Sapotaceae Mimusops sechellarum (Oliv.) Hemsl. 119 Northea hornei (M. M. Hartog) Pierre Scrophulariaceae 120 Striga asiatica (L.) O. Kuntze Sterculiaceae 121 Heritiera littoralis Ait. Tiliaceae 122 Triumfetta rhomboidea Jacq. Turneraceae 123. Turnera angustifolia Miller Umbelliferae 124 Centella asiatica (L.) Urb. Verbenaceae 125. Premna serratifolia L. 126 Stachytarpheta jamaicensis (L.) Vahl. 127 Stachytarpheta urticifolia (Salisb.) Sims. 128 Vitex trifolia L. ANGIOSPERMAE: Monotyledons Agavaceae 129 Agave sisalana (Perr. ex Engelm.) Drum. & Prain 130 Furcraea foetida (L.) Haw. Amaryllidaceae 131 Crinum ?asiaticum L. 132 Hymenocallis littoralis (Jacq.) Salisb. Araceae 133. Colocasia esculenta (L.) Schott 134 Dieffenbachia sequine (Jacq.) Schott 135 Epipremnum pinnatum (L.) Engel. cv. aureum 136 Protarum sechellarum Engl. Bromeliaceae 137 Ananas comosus (L.) Merr. Commelinaceae 138 Commelina sp. 139 Tradescantia spathacea Swartz. Cyperaceae 140 Cyperus halpan L. Cyperus iria L. 141 Cyperus ?difformis L. 142 Eleocharis sp. 143. Fimbristylis ?complanata (Retz.) Link 144 Fimbristylis cymosa R. Br. 145 Fimbristylis ?dichotoma (L.) Vahl 146 Fimbristylis sp. (glacis sedge) 147 Kyllinga polyphylla Willd. ex Kunth Kyllinga tenuifolia Steud. 148 Lophoschoenus hornei (C. B. Cl.) Stapf. 149 Mariscus dubius (Rottb.) Fischer Status N N mH tH 71 Yl FA Son) eA AS) SES 2S) ZH oS) 2-5) XS) Abund. I @ 2 2 © © © QO Qo © 137 Habitats Notes HW HSc Gl, HSc Cu, HW Gl Gl Cu Ma, Gl HW Ma Gl PG Gl Gl HSc Gl BC, PG, HSc Previous record’ Only in gardens Only in gardens Only in gardens Only in gardens Previous record- Previous record” 138 150 Mariscus pennatus (Lam.) Domin. 151 Pycreus polystachyos (Rottb.) P. Beauv. 152. Thoracostachyum floribundum (Nees) C.B.Cl. Flagellariaceae 153. Flagellaria indica L. Gramineae 154 Brachiara umbellata (Trin.) W. D. Clayton 155. Cymbopogon sp. 156 Dactyloctenium ?ctenoides (Steud.) Bosser 157 Digitaria didactyla Willd. 158 Digitaria sp. 159 Enteropogon sechellensis (Baker) Dur. & Schinz 160 Eragrostis tenella (L.) P. Beuv. 161 Eragrostis ?tenella var. insularis Hubb. 162 Heteropogon contortus (L.) P. Beuv. 163. Ischaenum heterotrichum Hack. 164 Oplismenus compositus (L.) P. Beuv. 165 Panicum brevifolium L. 166 Panicum maximum L. 167 Paspalum sp. 168 Pennisetum polystachyon (L.) Schult. 169 Saccharum officinarum L. 170 Sporobolus ?virginicus (L.) Kunth. 171 Stenotaphrum dimidiatum (L.) Brogn. Hypoxidaceae 172. Hypoxidia rhizophylla (Baker) Dur. & Schinz Liliaceae 173. Dracaena reflexa Lam. var. angustifolia Baker Lemnaceae Lemna perpusilla Torrey Musaceae 174 Musa sp. (M.?sapientum) Orchidaceae 175 Cynorkis ?seychellarum Aver. 176 O6coniella aphrodite Schltr. 177. Vanilla phalaenopsis Reichb. f. 178 Vanilla planifolia Andrews Palmae 179 Cocos nucifera L. 180 Deckenia nobilis Wendl. 181 Lodoicea maldivica (Gmel.) Pers 182 Phoenicophorium borsigianum (K. Koch) Stuntz 183 Phoenix dactylifera L. Pandanaceae 184 Pandanus balfourii Mart. 185 Pandanus multispicatus Balf. f. 186 Pandanus sechellarum 187 Pandanus utilis ZAmrrvvA7 Avrwvve Ze De (xD) | ies) Z sO mW TAO: o) 2 Co PP COQ Qe p> ere! CroOoOa ©: Rea Ol@ > Ou a a OS aC) ©) - Previous record Ma Ma HW HW PG, HW, HSc Cu Only in gardens BC Cu Only in gardens - Previous record? Cu One old palm, in garden \ - stlennencd eter? BS Vit. TERENCE Me VPI SHAN! i ; a 1 i . 2 (GBOLOGY, 7D : an) | ; a raft Sistul py relaiul Wers striate iy Ae tie vicdhate ar edf tro ! 7 ‘ if (ire noms is ip? ia, ie Ww heurt s4 Hal Nile ve ‘es mA * Aor “ Gis 4 rw evan: Wie 5 ait DALEY ax “a iy; malt Salita at RWS Bon ive rh : hy resi vitig, Grey t ( ; TS Gre ielARG ike ue sal Hy sacl 7: bie arive) or Mi oF batt ay ito + fel int (Tirta: dan int a ad fedoba © rome! ol Fr oof 73) Siforin 2 dyes af cit ie quicrrpr yz piers Minihalie vuole have (usin an ul artic colle (Bikey By (ihe BS 1nd) oO! AWwesiheriny: Airducth rt ack Miaka is bts? reid A dae rilicut, lic eb eh irs swig rychy Wib * ema _ f : rit AL wh! creat a i mila Ae Ty lie ehdvidien 10 masl.) | Woodland (predominantly introduced) Scrub (mixed) 28.0 Scrub (introduced) 3\ Beach crest vegetation (Scaevola scrub) wD Grassland/garden 0.3 Bare rock 8.6 Plateau Woodland (predominantly native) 1.8 (<10 masl.) | Coconut with regeneration Coconut plantation Scrub (mixed) Beach crest vegetation Freshwater marsh Grassland/garden Bare rock 144 Legend: vegetation types ie Bare rock [“] Grassland Scaevola scrub Beach crest trees [I] Coconut plantation Coconut scrub Tabebuia/coconut woodland Cinnamon woodland Hill woodland, mainly Calophyllum Aa Terminalia Scrub, includes cocoplum Cocoplum scrub cil . I ia jae ii —k—k—== 200 metres Figure 2. Grande Soeur: vegetation. 145 The herb layer (<0.5 m) included 21 species, of which the most frequent were the native ferns Phymatosorus scolopendria (in seven plots) and Nephrolepis biserrata (in six plots). Vegetation cover in this layer was rather sparse (mean cover 30.1%) with similar proportions of open leaf litter (38.5%) and bare rock (31.8%). INVERTEBRATES Pitfall trapping Pitfall trap assemblages were very small. The mean number of individuals per five traps was 20.5, compared to mean for season (all islands) of 68.18 individuals per five traps. Assemblages were dominated by ants (78% of all invertebrate individuals were ants), the most abundant species being Odontomachus troglodytes (78 individuals; 38.0% of total). Technomyrmex albipes, the dominant ant species in collections from Grande Soeur made by Mithlenberg ef a/. (1977), was also collected (25 individuals, 12.2% of total). Other taxonomic groups represented included Orthoptera (7.8% of total individuals), Dermaptera (6.3%), Isoptera and Blattodea (each 2.0%), molluscs and Coleoptera (each 1.0%) and four other groups represented by only one individual each. The crazy ant Anoplolepis gracilipes, which has been introduced to other agricultural islands, was not collected. Leaf-insect Counts Leaf-insect counts were carried out for seven tree and shrub species. Results are shown in Table 3. The highest leaf counts were on the native tree Terminalia catappa. However, invertebrates were also abundant on the introduced cinnamon. Most invertebrates on cinnamon were ants (22%) and soft bugs Sternorrhyncha (75%). Table 3. Density of invertebrates on foliage, Grande Soeur. Species No. leaves Mean inverts Mean insects counted leaf! m Introduced Chrysobalanus icaco 150 0.107 29.82 Cinnamomum verum 200 0.495 72.74 Tabebuia pallida 100 0.030 4.19 Native Calophyllum inophyllum 450 0.609 51.79 Canthium bibracteatum 340 0.079 27.89 Terminalia catappa 160 1.588 $1.65 ?Status unknown Morinda citrifolia 160 0.525 37.34 146 Malaise Trapping Three malaise traps were in place for three nights each in hill woodland habitats. Malaise trap assemblages were very large (mean number of invertebrates was 762), and included members of 10 invertebrate orders. The dominant orders were the Lepidoptera (53.4% of all individuals), Diptera (18.2%) and Hemiptera (14.5%). The majority of taxa collected have yet to be identified to species level. A number of invertebrate species were observed (Table 4). Table 4. Invertebrate species identified. Order Family Species Notes Mollusca: Gastropoda Achatinidae Achatina ?fulica (Bowditch, 1822) Many empty shells, hill Crustacea: Decapoda Myriapoda: Chilopoda Diplopoda Insecta: Blattodea Lepidoptera Odonata Hymenoptera Helicinidae Subulinidae Thiaridae Coenobitidae Grapsidae Ocypodidae Scolopendridae Spirostreptidae Trigoniulidae Blattidae Lycaenidae Hesperiidae Libellulidae Anthophoridae Apidae Formicidae Helicina theobaldiana Nevill, 1871 Subulina striatella (Rang, 1831) Melanoides tuberculata (Miller, 1774) Coenobita brevimanus Dana, 1852 Grapsus crinipes (Dana, 1851) Ocypode ceratophthalmus (Pallas, 1772) Ocypode cordimana Desmarest, 1825 Scolopendra subspinipes Leach, 1918 Seychelleptus seychellarum (Desjardins, 1834) Spiromanes braueri (Attems, 1900) Periplanata sp. Leptotes pirithous Linnaeus, 1767 Zizeeria knysna (Trimen, 1862) Borbo sp. Diplocodes trivialis (Rambur, 1842) Orthetrum stemmale wrightii (Selys, 1877) Tholymis tillarga (Fabricius, 1798) Xylocopa caffra (Linnaeus, 1767) Apis mellifera adansoni Latreille 1804 ?Pachycondyla melanaria (Emery, 1894) Camponotus grandieri Forel, 1886 Cardiocondyla emeryi Forel, 1881 Odontomachus troglodytes Santschi, 1914 Technomyrmex albipes (Smith, 1861) woodland Endemic. In pitfall traps Introduced. in pitfall traps One specimen Commonly caught in rat traps Abundant on Grande Anse One individual observed Several individuals seen (by day) in hill woodland In pitfall traps Abundant on plateau Several specimens caught Several specimens caught One individual observed Observed at plateau marsh Observed flying over hill Over marsh at dusk In pitfall traps In pitfall traps In pitfall traps In pitfall traps In pitfall traps Vespidae Polistes olivaceus (de Geer 1773) 147 VERTEBRATES Amphibians, Reptiles and Fish A total of six species (one amphibian, three lizards, one tortoise and one freshwater fish) was observed (Table 5); several other species have been recorded in the past (Cheke, 1984) and are probably still present. The status of terrapins Pelusios sp., introduced from La Digue in the mid-late 1990s, is unknown. Two species recorded by earlier workers were not observed in the current survey: the gecko Urocotyledon inexpectata, and the burrowing skink Pamelaescincus gardineri (Cheke, 1984). Both of these lizards are easily overlooked and probably survive on the island. Giant tortoises, presumably one of the species of the granitic islands, were present on “Les Soeurs’) in the late eighteenth century (Bour, 1984); the date of their extinction is unknown. A herd of giant tortoises, probably the Aldabra species, was noted by General Gordon in 1881 (Stoddart and Peake, 1979). In 1999, a small group of Aldabra giant tortoises was kept in a pen on the plateau. The exposed eastern beach of Grande Soeur is reportedly used for nesting by Hawksbill sea turtles Eretmochelys imbricata (Frazier, 1984). Table 5. Amphibians, reptiles and fish observed. Status: E =endemic, I = introduced, N = native (in central Seychelles). Family Species Status Amphibians Raniidae Ptychadaena mascareniensis (Dumeril & Bibron, | Mascarene frog 21 1836) Reptiles Gekkonidae Gehyra mutilata (Wiegmann, 1835) Pacific house gecko I Phelsuma sp. (?P. astriata Tornier, 1901) day gecko E Scincidae Mabuya sechellensis (Dumeril & Bibron, 1836) Seychelles skink E Testudinidae | Geochelone gigantea (Schweigger, 1812) Aldabra giant tortoise Fishes Rivulidae Pachypanchax playfairii Giinther, 1866 Seychelles killifish E Birds In total, 15 land birds and waders were recorded (Table 6). Only two endemic species were observed. In addition to sight records, tape playback was used to determine presence/absence of three endemic species: Seychelles white-eye Zosterops modestus, Seychelles scops owl Otus insularis and Seychelles black paradise flycatcher Terpsiphone corvina. There were no positive responses. At the time of the survey, domestic fowl were a notable feature of Grande Soeur; the plateau area supported a large number of domestic birds (over 150 individuals) of six species, the most abundant being ducks and chickens. The birds were fed regularly but eggs were not collected and (apparently) birds are rarely, if ever, killed for human 148 consumption. There appeared to be few checks on population growth. The birds roamed freely on the plateau and had a major impact on plateau ecosystems (especially the marsh), although they rarely appeared to enter semi-natural habitats on the hills. Few endemic land bird species have ever been recorded on Grande Soeur; the island appears to have been little-visited by naturalists before extensive habitat change. Endemic birds that may have occurred on Grande Soeur in the past include the chestnut- flanked white-eye Zosterops mayottensis semifiava (only known from Marianne and now extinct), Seychelles magpie-robin Copsychus sechellarum and Seychelles black paradise flycatcher Terpsiphone corvina. All these species have formerly been recorded on satellite islands of La Digue (Newton, 1867; Collar and Stuart, 1985). The presence of phosphatic rocks on parts of the island (Baker, 1963) suggests that seabird colonies must have been a prominent feature of the island’s past biota, but today only one or two species appear to breed, at low densities. Table 6. Wild terrestrial birds and waders observed on Grande Soeur. M = migrant species; V = vagrant species; E = Seychelles endemic species. Species Butorides striatus Ixobrychus sinensis Gallinula chloropus Pluvialis squatarola M Gallinago ?gallinago V Numenius phaeopus M Tringa nebularia M Calidris alba M Arenaria interpres M Streptopelia picturata ssp. Geopelia striata Alectroenas pulcherrima E Nectarinia dussumieri E Acridotheres tristis Foudia madagascariensis green-backed heron yellow bittern common moorhen grey plover snipe whimbrel common greenshank sanderling ruddy turnstone turtle dove barred ground dove Seychelles blue pigeon Seychelles sunbird common mynah Madagascar fody Notes Seen regularly around the plateau marsh, in both July and December. Seen once at plateau marsh, 19/7/99 A small number occur at the plateau marsh Seen on reconnaissance trip May 1999 (LD). Two individuals seen on Grand’ Anse and marsh, 14/12/99. One individual seen feeding in plateau marsh, SAD: Seen once, at Grand Anse 22/7/99 One individual seen feeding in plateau marsh, 15/12/99. Flock of 5-6 seen on Grand’ Anse, 14/12/99 Flock of 10 seen on plateau, 15/12/99. Very common on the plateau: flock of around 30 individuals seen around buildings 18/7/99 Occasional on plateau Seen regularly in hill woodland, and on the plateau Very common in nill woodland and on the plateau Very common on the plateau, feeding around houses and on the beach A few birds were seen, on plateau-edge/glacis habitats 149 Table 7. Seabirds recorded on Grande Soeur. Species Notes Puffinus pacificus wedge-tailed shearwater Calls heard at night Puffinus lherminieri | Audubon’s shearwater Calls heard at night Phaeton lepturus white-tailed tropicbird A few individuals seen, flying close to the island by day. On occasion, flew around trees on plateau. Gygis alba fairy tern Breeding birds present in trees in hill woodland July 1999. Mammals Mammals observed in the course of fieldwork were recorded (Table 8). In addition, rodent trapping was carried out with two traplines, both in plateau scrub habitat. A total of 140 trap-nights were carried out and 91 individual rats caught, giving a capture rate of 65 rats per 100 trap-nights (unadjusted) or 99.45 per 100 trap-nights (adjusted to account for the effects of closed traps; Cunningham and Moors, 1996). This rate of trapping was the highest for any island throughout the survey (overall mean for all islands in season was 33.64 rats per 100 trap-nights unadjusted). The exceptionally high capture rate was probably an indication of a high population density but was also likely to be a function of seasonal effects. During the south east season, and particularly in July, rats were under greater food and water stress than at other times and were therefore more likely to be caught. Rodent eradication programmes in 2000 were deliberately carried out at that time of year to exploit the increased uptake of bait then (Don Merton, pers. comm). The only rodent species recorded on the island was the ship rat Rattus rattus, a widespread species in Seychelles that can have significant impacts on bird populations as it is a proficient climber (Racey and Nicoll, 1984). Table 8. Mammals observed, Grand Soeur. Status Three domestic dogs were kept at the settlement Feral cats were reported by people living on the island, and cat scat was observed on rocks at the edge of the plateau, although the animals were not seen At least one rabbit kept (caged) at the settlement In July 1999, a roost of at least 40 individuals was found close to the North-East coast of the island at L’Enclos (Grid reference CL 7465 2645) Widespread Canis familiaris L. Felis catus L. Oryctolagus cuniculus L. Pteropus seychellensis Milne Edwards Rattus rattus L. CONSERVATION RECOMMENDATIONS At the time of the survey, Grande Soeur had little conservation interest. Some endemic species of plant and invertebrate were recorded. However, a high density of rats and the presence of cats appeared to have destroyed any endangered endemic land birds 150 that may have once survived on the island, and probably had a negative impact on reptile species. The presence of a large population of domestic fowl probably caused enhanced rat populations and influenced the biodiversity of the marsh ecosystem. Invasive alien plant species, most introduced during the plantation period, undoubtedly displaced native and endemic species, although the number of endemic plants present was probably always rather small due to the island’s size. Because of the lack of biological records of the island in the past, any attempt to reconstruct island ecosystems is based largely on conjecture. From written records, it seems that the island was probably never well-wooded, and that large areas of open rock and shrubby forest may have supported breeding colonies of seabird species. Endemic birds in addition to the two species recorded in the current survey were probably present. With correct management, the island could be rehabilitated to an extent. The most urgent action for endemic vertebrates is the eradication of mammalian predators. Removal of predators would allow the introduction of endemic land birds and allow breeding colonies of seabirds to develop. The reduction of populations of domestic birds would enhance the conservation value of the freshwater marsh, reducing disturbance and eutrophication. The removal or control of invasive weed species would be desirable, although eradication of some species is probably impossible due to the broken terrain. However, some introduced species (especially cinnamon) have relatively high densities of invertebrates on their foliage, and removal of these species would not be necessary for the introduction of small insectivorous birds such as Seychelles white-eye Zosterops modestus and Seychelles warbler Acrocephalus sechellensis. The Seychelles black paradise flycatcher may have occurred on the island in the past (records exist for nearby Praslin, La Digue, Félicité and Marianne; Collar and Stuart, 1995), but the limited area of woodland vegetation on the island would probably support only a small population. The small pitfall trap assemblages suggest that the potential food supply for Seychelles magpie-robins is poor, at least on the hill. While the plateau area (and possibly, areas of the hill with particularly fertile soils) could be managed to form suitable habitat, the total population of birds that the island could support is small. Grande Soeur is not a priority island for Seychelles magpie-robin management. 15] Appendix 1. Plant species recorded from Grande Soeur Taxonomy of dicotyledons as given by Friedmann (1994). Of monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>1000 individuals observed); C = Common (100 - 1000 individuals observed); F = Frequent (10 - 100 individuals observed); Occasional (3 - 10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: Cu = Cultivated; PG = Plateau grassland; HW = Hill Woodland; Sc = Hill Scrub; Gl = Glacis; BC = Beach Crest; Ma = Marsh. Species Status | Abund. Habitats Notes PTERIDOPHYTA Adiantaceae l Acrostichum aureum L. N F Ma Davalliaceae 2 Nephrolepis biserrata (Sw.) Schott N A HW Polypodiaceae 3 Phymatosorus scolopendria (Burm. f.) N A HW Psilotaceae 4 Psilotum ?nudum Sw. N G HW ANGIOSPERMAE: Dicotyledons Acanthaceae 5 Asystasia sp. B (sensu Friedmann) ?I A Sc, Gl, HW Amaranthaceae 6 Alternanthera sessilis (L.) DC. I (E Ma Anacardiaceae 7 Anacardium occidentale L. I O HW 8 Mangifera indica L. I in PG, HW 9 Spondias cytherea Sonn. I R HW Apocynaceae 10. Catharanthus roseus (L.) G. Don. I F PG 11. = Plumeria rubra L. I R PG Only in garden Araliaceae 12. Gastonia ?sechellarum (Baker) Harms. E R HW Bignoniaceae 13. Tabebuia pallida (Lindl.) Miers. I © HW, [PG] Boraginaceae 14 = Tournefortia argentea L. f. N O BC Cactaceae 15 = ?Hylocereus undatus (Haw.) Britt. et Rose R Cu Only in garden 16 Opuntia sp. I O PG Caesalpiniaceae 17. ~—sIntsia bijuga (Colebr.) O. Kuntze N O HW 18 Senna occidentalis (L.) Link I F HW, PG Caricaceae 19 = Carica papaya L. i R PG Casuarinaceae 20 Casuarina equisetifolia J. R. & G. Foster I F HW Chrysobalanaceae 21 Chrysobalanus icaco L. ] A Se, HW, Gl lis2 Species Status — Abund. Habitats Notes Combretaceae 22. = Terminalia catappa L. 2N € PG, HW Compositae 23. ~~ Emilia sonchifolia (L.) Wight I O RGSSc 24 ~—-Tridax procumbens L. I R RG: 25 Vernonia cinerea (L.) Less. I A PG, Sc Convulvulaceae 26 Ipomoea aquatica Forssk. I F Ma 27 ~~ Ipomoea batatas (L.) Lam. I O Cu 28 Ipomoea macrantha Roem. & Schultes N O HW 29 ~~ Ipomoea obscura (L.) Ker Gawl. I R PG 30 = Ipomoea pes-caprae (L.) R. Br. N € BEVGI Crassulaceae 31 Kalanchoe pinnata (Lam.) Pers. I R PG Euphorbiaceae 32. = Euphorbia hirta L. I C PG, Sc 33. = Euphorbia thymifolia L. I O Cu 34. ~— Pedilanthus tithymaloides (L.) Poit. I O Cu Only in garden 35. -Phyllanthus acidus (L.) Skeels I R PG 36 Phyllanthus amarus Schumach. & Thonn. I F PG, HW Goodeniaceae 37. Scaevola sericea Vahl. N C BE Guttiferae 38 Calophyllum inophyllum L. N A HW, PG Hernandiaceae 39 _Hernandia nymphaeifolia (Presl) Kubitzki N O BC Labiatae 40 ~~ Plectranthus amboinicus (Lour.) Spreng. 21 R PG Lauraceae 4] Cassythea filiformis L. N R BC 42 ~~ Cinnamomum verum Presl. I A HW 43. Persea americana Mill. I R PG Only in garden Malvaceae 44 — Hibiscus tiliaceus L. N F BC 45 Thespesia populnea (L.) Soland. Ex Correa N R BC Meliaceae 46 Xylocarpus moluccensis (Lam.) Roem. N R BC Mimosaceae 47 — Adenanthera pavonina L. I € HW 48 Leucaena leucocephala (Lam.) de Wit F HW Moraceae 49 — Artocarpus altilis (Parkins.) Fosb. I O PG 50 Ficus lutea Vahl. N (e HW, Gl 51 Ficus reflexa Thunb. Ssp. Seychellensis E (ss) 2 HW, Gl (Baker) Berg 52. Ficus rubra Vahl. N R HW Moringaceae 53. Moringa oleifera Lam. I R PGES Myrtaceae 54 Eucalyptus sp. I F PW 55 Psidium guajava L. I O Cu 56 Syzygium wrightii (Baker) A. J. Scott E R HW Species Status Onagraceae 57. Ludwigia octovalvis (Jacquin) Raven 21 58 Ludwigia erecta (L.) Hara ] Oxalidaceae 59 Averrhoa bilimbi L. I Papilionaceae 60 Abrus precatorius L. 2N 61 Canavalia cathartica Thouars. N 62 Centrosema pubescens Benth. I 63 Crotalaria pallida Ait. 21 64 Desmodium incanum DC. I 65 Desmodium triflorum (L.) DC. I 66 Indigofera tinctoria L. I 67 Tephrosia noctiflora Bojer ex Baker I 68 Teramnus labialis (L.) Spreng. I Passifloraceae 69 = Passiflora edulis Sims 70 ~~~ Passiflora suberosa L. Portulacaceae 71 ~~ ~Portulaca oleracea L. N Rubiaceae 72, ~~ Canthium bibractatum (Baker) Hiem. N 73 Coffea canephora Froehner I 74 ~~ Guettarda speciosa L. N 75 Morinda citrifolia L. 21 76 + Paragenipa wrightii (Baker) F. Friedmann E Rutaceae 77 ~~ Citrus sinensis (L.) Osbeck I Scrophulariaceae 78 ~~ Striga asiatica (L.) O. Kuntze I Tiliaceae 79 Triumphetta rhomboidea Jacq. I Turneraceae 80 Turnera angustifolia Miller I Umbelliferae 81 Centella asiatica (L.) Urb. val Verbenaceae 82 Phyla nodiflora (L.) Greene I 83. = Premna serratifolia L. N 84 Stachytarpheta jamaicensis (L.) Vahl. I 85 Stachytarpheta urticifolia (Salisb.) Sims. I 86 = Vitex trifolia L. I ANGIOSPERMAE: Monotyledons Agavaceae 87 Agave sisalana (Perr. Ex. Engelm.) Drumm, & Prain 88 Furcraea foetida (L.) Haw. Amaryllidaceae 89 Hymenocallis littoralis L. Bromeliaceae 90 Ananas comosus (L.) Merr. Cyperaceae 9] Cyperus halpan L. Abund. F O a Qe wOa SOs = OGM rs i © © & D> aay Dd (e) > e) 153 Habitats Notes Ma Ma HW HW, Sc BC HW, PG PG HW HW PG, HW HW PG Cu PG, HW Ma, PG HW [PG] HW PG HW PG, HW PG, HW 154 Species Status Abund. Habitats Notes 92 ?Cyperus sp. 2 R HW 93 Fimbristylis cymosa R. Br. ? EF Gl, HW 94 Fimbristyis dichotoma (L.) Vahl. U C PG 95 Kyllinga polyphylla Willd. ex Kunth N Cc PG, Ma 96 = Mariscus dubius (Rottb.) Fischer N C RG 97 = Mariscus pennatus (Lam.) Domin. N ig Ma 98 Pycreus polystachyos (Rottb.) P. Beauv. ? F Ma 99 = Thoracostachyum floribundum (Nees) E O HW C Beh Gramineae 100 Brachiara umbellata (Trin.) W. D. Clayton N A HW 101. Dactyloctenium ctenoides (Steud.) Bosser ? Fs BC, PG 102 Digitaria sp. ? A PG, HSc 103. Echinochloa colonum (L.) Link z O PG 104 Enteropogon sechellensis (Baker) Dur. & N C PG, HSc Schinz 105 Eragrostis tenella var. insularis Hubb. ? O PG 106 Panicum brevifolium L. N A HW 107 Panicum maximum L. v F HW, Gl 108 Paspalum conjugatum Berg N F PG 109 Pennisetum polystachyon (L.) Schult. e O Gl 110 Saccharum officinarum L. I O PG 111 Sporobolus ?virginicus (L.) Kunth. N A BCZEG 112 Stenotaphrum dimidiatum (L.) Brogn. N A PG Liliaceae 113. Cordyline fruticosa (L.) A. Chev. I R PG 114 Dracaena reflexa Lam. var. angustifolia N A HW, Gl Baker Musaceae 115 Musa sp. I R Cu Orchidaceae 116 Disperis tripetaloides (Thouars)Lindl. N R HW 117. Vanilla planifolia Andrews I C HW Palmae 118 Cocos nucifera L. N A PG, HW Pandanaceae 119 Pandanus balfourii Mart. B C Gl, HW 120 Pandanus utilis Bory I Cc Cu “REAIAN SE a fe - 155 yh : \ . j ‘AGL ) PA 7 Me WE STEVE SD). PARR wat rs = ; a a4, ofle sokgpeoely — AT! a, ‘ie PMiariinme | We ee) peu nf jot nn f bach laroee eT 1 E eur y hiphoest ; neler! Shack tel « i Para et toachicn 14 cid Wwe Hi om ai) au tog Je Sony 1 dries #1 ; One TAD an ban (oer Table 1) ee ee iS gar PAE wiles) ia Raaie. lie pe PARR erate. whit: ehligiely Trond the oi moe igi Vs Preallp rae (agi a Trnway hs Are i @ atari es i) Seale yu: ui ie ; ire} MN tiloteqife awe) Jin Ne lores 4 ah a Rairsity mein sch stig yoau lt ot rnp - ieabtitiauioe! Me avilne wonky (Pr: By te or-ainh | Ye thes ne ae asi dine cpprate ay; Pt aii uit ares THe Pee Yi diets ie ail LS ASME LiL Cems yr de Hi The tint agente 7 Pe xloerd te. parti Heir ort O? tet ant le sat seme sacheding oly Porim i ind bearer! fe Mee : ve ti Cece Th 7, me: KOE OF Ee oh ot eee AIG ES Ore. OTF fs ana 3 | i‘ Davee! AL ihe 3 tee MUTHbE ly @ripse y tity i slider Setticnn Cw fee 4 — fat cy. Piatt Of thee | _ Bie {iT Aes Ma vig | Th, er Wel Bes 5 hn Bb sde Pineal an NAVE Aes) va" ph ; aul Ce ce ip « BON SENS Mha- : i enh, watid- iy ,, clcabe ) | Se atal) aay Boos 1)vOR) Svcd COND Udy rrr gengarte gt imu! 3), E ee | | lena elie Mtoe Jc Seni Pcie OF fresh eater 4 = preieal Nia ‘ Povvertarse 1/-(hia Oveze airits OTe ] i, " J T° ; ing - : 2 MOM sn ox . Sit ntvirest or y Tue savcholice Aalaris 2 Pie ty Wiig? aia. 4 eR ETA PANO o iilay Cattliss oe Ps te sellin’ % ines : ci 7 hale Ce he a hy pu) nfo sey eye Al it taeté BES Hiliie Cra Mwah: ie S Ag, vy. ipa uae ' 7 wa ie 2 oe 1 Ke CAT et Whe ae) Se ale bes critic ‘ead re - WL Pipe (Veta aloeuls Cas Ea E4/1 B® E4/2 E4/38 & WF4/3 pes eu OB x D11 Fala Legend a Contours & Vegetation plots m a Building & Beach Figure 1. Marianne: physical, with locations of vegetation plots. E54 © /waF5/4 Ee ES3@ wES/2 EG/1 ba & BG ME6G/2 G6 & i v= DAO E108 FAO) {Gio — 200 metres MARIANNE Ive MICHAEL J. HILL!, PAT MATYOT?”, TERENCE M. VEL’, STEVEN J. PARR? and NIRMAL J. SHAH! GEOLOGY, TOPOGRAPHY AND CLIMATE Marianne has an area of 94.7 ha, and is the twelfth largest of the granitic Seychelles Islands. At its highest point (Estel Hill, grid ref. CL8034 2068) it reaches 130 m above sea level. A second lower peak (about 85 m) occurs to the South (grid ref. CL8023 1977). Most of the island is gently sloping land below 50 m (see Table 1). The island is made up of porphyritic granite, which differs slightly from that of the other islands in the Praslin-La Digue group. Traversing the island in a northwesterly direction is a dyke of closely jointed metadolerite rock. On the northern slopes of the island, brown earthy rocks occur, the result of guano deposition on granite soils (Baker, 1963). On the western side of the island is a small “plateau” with a fringing reef. The plateau is made up of recent calcareous sediments and marsh deposits. The island’s gentle slopes have allowed the accumulation of red earth soils throughout, excluding only some areas of coastal glacis, where little or no soil occurs. The plateau has soils of the Shioya series (DOS, 1966). Fresh water on the island is limited, especially during the dry season. At the site of the main former settlement (La Cour), there are two shallow wells. Much of the plateau area supports marsh vegetation (mainly sedges and Ludwigia), but in October 1999 there was no standing water. In March, after heavy rain, most of the plateau area was under fresh water to a depth of several centimetres. The marsh must occasionally be inundated; Shah and Parr (1998) reported the presence of mullet Mugil cephalus. On coastal glacis in the South of the island near Pointe Grande Glacis (grid ref. CL8035 1925), standing pools of fresh water were present in October. Marianne 1s the most remote of the La Digue group of islands. The nearest island is Félicité, 3.8km away. The nearest large inhabited island is La Digue, 7.2km from Marianne. The Seychelles islands experience a seasonal humid tropical climate (Walsh, 1984). While no weather data exist for Marianne, it could be predicted that the climate of the island follows a similar pattern to that of Félicité, with lower total rainfall than coastal sites on the larger islands. ' Nature Seychelles, PO Box 1310, Mahé, Seychelles. Email: birdlite@seychelles.net > SBC, PO Box 321, Victoria, Mahé, Seychelles. * Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, UK. 158 Table 1. Area of Marianne by altitude (calculated from maps published by Directorate of Overseas Survey (UK)/Seychelles Government). Altitude range (m. asl.) Approx. area Percentage total area (ha) 100 - 150 3 32. 50 - 100 24 25/5 10 - 50 49 52.1 0-10 18 19S HISTORY The Marion Dufresne expedition of 1768 (prior to settlement of the Seychelles) made only a short note on Marianne Island, recording that only a little woodland was present (Lionnet, 1984). They also recorded the presence of giant tortoises (Bour, 1984). In the earliest days of the colony, the lack of fresh water (perhaps combined with difficult access) probably restricted development on the island, although it passed into private hands in the early nineteenth century. By the 1830s, maize was being produced on Marianne Island in quantity (McAteer, 2000), but natural habitats remained; in 1866, the visiting naturalist Edward Newton recorded that the north side of Marianne appeared ‘tolerably wooded, but...not with any very large trees’ (Newton, 1867), although it seems that during his short stay he remained on the western side of the island around the settlement at La Cour. At the time of his visit, the human population of Marianne was one family of five people. During a short stay on the island he recorded seven endemic species of birds, two of which (Seychelles fody Foudia sechellarum and the chestnut- flanked white-eye Zosterops mayottensis semiflava) were new to science. He noted that the island had no cats or rats, while the nearby Félicité Island, although well-wooded (it was government-owned and supplied timber for other Seychelles islands at the time of his visit) had few birds and had populations of introduced predators. Noting that the owner of Marianne (M. Choppy) intended to start a coconut plantation on the island, he suggested that this act could be as destructive to the native avifauna (which was obviously outstanding for the period) as the introduction of predators. Native vegetation and endemic species prevailed on Marianne for longer than on neighbouring islands. In 1890, most of the endemic birds recorded by Newton were still present (Ridgway, 1895). However, in the early twentieth century plantations replaced native forest; in the 1920s, extensive stands of the Seychelles endemic tree bwa-d-nat Mimusops sechellarum were cleared for firewood (Procter, 1974). By 1940, the human population of the island was 60 (Bradley, 1940). Marianne’s extensive plantations supplied copra, fruit and other crops such as sweet potatoes until 1983, when coconut palms on the island were hit by disease (thought to be caused by a combination of insect pests, drought and high winds). A five-month quarantine was imposed on the island, banning the removal of agricultural produce. At the time, Marianne was said to be one of the major copra-producing plantations in Seychelles, and the quarantine caused a significant reduction in Seychelles’ copra exports for the year (Seychelles Nation, 7/10/83). 159 Marianne Island is still privately owned, but its plantations have fallen into disuse. At the time of the survey visit, the island was uninhabited although a caretaker occasionally stayed overnight and had planted crops (including pumpkins, cassava and aubergine) on part of the plateau. The island was occasionally visited by day-trippers from La Digue and local fishermen. FLORA AND VEGETATION Flora A total of 152 plant species were recorded on Marianne, including six ferns and 146 angiosperms. Of the angiosperms, 81 (53.3%) species are regarded as introduced in Seychelles (Friedmann, 1994) and 48 (32.9%) native. Of the native species, eight were endemic to the Seychelles (5.5% of the angiosperm flora). At least seven species of introduced plant (4.6% of the total flora) recorded on Marianne were restricted to cultivated areas of the plateau, where they had been planted in 1999. They were observed nowhere else on the island and would probably become extinct were cultivation to cease. The proportion of the angiosperm flora made up of Seychelles endemics was lower than the average for the Seychelles as a whole (of the total Seychelles flora, around 54% are introduced and 9% endemic: Procter, 1984). The low proportion of endemics reflects the island’s relatively small size and also the destruction of the natural vegetation of the island in the twentieth century. The surviving endemic species were restricted to the rockiest parts of the island when the plantation was functioning, although some have begun to spread out from these refugia. Both Gastonia sechellarum and Tarenna sechellensis were found as young plants amongst Canthium scrub in the former plantation. Mimusops sechellarum, which was among the dominant trees of the original native forest (Procter, 1974) was uncommon but several extremely large trees (two of which each reached around 20 m) were observed in predominantly native vegetation in the north of the island. Regeneration of this species appeared poor, perhaps as a result of seed predation by rats (Carlstr6m, 1996a). No endemic palms were found. Of the introduced plants established on Marianne, 15 are invasive weedy species. Compared to other granitic islands, Marianne had relatively few woody weed species. The cocoplum Chrysobalanus icaco was notably absent and cinnamon Cinnamomum verum, although present was very rare. Only a handful of mature cinnamon trees were observed, with some regeneration. This was an extremely unusual situation; on other islands, cinnamon appears extremely invasive and has come to dominate large areas. Previous work on the flora of Marianne has been limited. Robertson (1989) includes some records from the island, but lists no species not recorded in the current survey. Vegetation The extents of major vegetation types on Marianne are shown in Table 2 and Figure 2. The vegetation has undergone great change since the plantation was abandoned and much of the island is characterised by tall, dense scrub regenerating beneath coconut or fruit trees. Areas on the east coast of the island still have the appearance of a managed 160 coconut plantation, with scrub invasion restricted by exposure to salt spray. Throughout the former plantation many of the old coconut palms are dead, probably through a combination of exposure, drought and insect attack. At higher altitudes, almost all old palms are dead. Near the summit of Estel Hill and to the north, there is an area of native woodland with very few palms or introduced plants. Table 2. Extent of major vegetation types, Marianne Island. Vegetation type Approx. area (ha Hill Woodland (predominantly native) 7 (>10 m asl) Woodland (mixed) dl Coconut plantation ] Coconut with regeneration 22 Scrub (native) 7 Scrub (mixed) 29 Grassland/garden 2 Bare rock Sl Plateau Woodland (predominantly native) <] (<10 masl) Woodland (exotic) 3 Coconut plantation 4 Coconut with regeneration 1 Scrub (native) 2 mm body length included (numbers in parentheses: excluding ants). Habitat | Mean no. individuals per 5 traps SE season NW season Marianne Native woodland 21.6 (9.0) 20.6 (3.4) Former plantation 49.6 (12.7) S/O) (251) All granitic islands 61.8 (9.4) 61.1 (16.0) ‘Mollusca ZAraneae OBlattodea Collembola OM Diptera & Dermaptera Elothers Former plantation Native woodland 0 50 100 150 200 250 300 350 400 Total number of individuals | Figure 3. Total pitfall assemblages from Marianne, excluding ants. Leaf-insect Counts Leaf-insect counts were carried out for 16 tree and shrub species, seven of these in both seasons. Results are shown in Table 5. Extremely high counts occur for Morinda citrifolia (status uncertain; possibly introduced) and Chinese guava Psidium cattleianum (introduced) in October, due to high numbers of soft bugs. In general, the highest leaf counts were for native species and a few fruit tree species (e.g. Citrus, Psidium) which are favoured by ants culturing soft bugs (mealy bugs and scale insects). 164 Table 5. Density of invertebrates on foliage, Marianne. n=no. of leaves counted; NI = number of individual invertebrates. SE season (October) NW season (March) Species Mean NI mean NI n mean NI mean NI leaf 5 leaf! m? Introduced species Annona muricata Citrus sp. Mangifera indica Psidium cattleianum Tabebuia pallida Native species 0.170 125i 0.060 9.56 0.210 45.89 Calophyllum inophyllum 0.140 17.03 Canthium bibracteatum 0.042 15221 Euphorbia pyrifolia 0.140 BS Oy Gastonia sechellarum Paragenipa wrightii 0.480 71.02 Premna serratifolia 0.218 28.94 Scaevola sericea 1.980 262.08 Tarenna sechellensis Tabernaemontana coffeoides Terminalia catappa ?Status unknown Morinda citrifolia 0.010 ESO 1.240 119.98 0.756 123.01 Malaise Trapping Malaise trapping was carried out in native woodland and former plantation habitats. Four Malaise traps (two in each habitat) were run in October 1999 and three (one in mixed former plantation, two in native woodland) in March 2000. Assemblages were slightly larger in March (mean number of individuals (NI) = 430) than in October (mean NI = 398), but there was no consistent pattern between habitats. Malaise trap assemblages included members of 13 invertebrate orders. The dominant orders were the Lepidoptera (43.7% of all individuals) and Diptera (28.7% of individuals). The majority of taxa collected have yet to be identified to species level: Hymenoptera (excluding ants) are currently being identified by Dr John Noyes of the Natural History Museum, London. Observation A list of species observed or collected is given in Table 6. Invertebrates of the highly disturbed areas of the plateau tended to be introduced or cosmopolitan species. Inland a greater number of endemic species were found. In general, the mixed woodland and scrub of abandoned plantation areas appeared richer than the native hill woodland on Estel Hill and the north of the island. Notable species included the endemic cricket Seychellesia longicercata normally found associated with endemic palms (Matyot, 1998). 165 At Pointe Grande Glacis, freshwater pools were present in October, when the marsh area was dry. Live mosquito larvae and dragonfly larvae were present. One adult dragonfly was observed flying over the pools, but could not be caught. Two dead insects were collected here: Myriochile melancholica perplexa (Coleoptera, Cicindelidae) and Perissosoma grande (Coleoptera, Scarabaeidae). This is apparently the first record of M. m. perplexa in Seychelles since the 1908-9 Percy Sladen Trust expedition (Scott, 1912). The species is widespread, occurring as a variety of different forms in Africa. The endemic chafer P. grande was formerly only known from Praslin, where it is often found in endemic palm forest. Due to the exposed position of this site, these insects could have originated outside Marianne. In early March, the plateau marsh varied greatly in size from a small area of damp mud to a wide pool of freshwater with a depth of several centimetres covering much of the plateau (following heavy rain). Several dragonfly species were observed at this time. Specimens of one water beetle (unidentified) were collected and a species of water boatman (Hemiptera: Notonectidae) observed. Table 6. Insects observed, Marianne Island. Order Family Species Arachnida Araneae Tetragnathidae Nephila inaurita (Walckenaer, 1841) Crustacea Decapoda Coenobitidae Coenobita brevimanus Dana, 1852 Gecarcinidae Cardisoma carnifex (Herbst, 1784) Grapsidae Grapsus tenuicrustatus (Herbst) Ocypodidae Ocypode ceratophthalma (Pallas, 1772) Mollusca Cyclophoridae Cyathopoma blanfordi Adams, 1868 Streptaxidae Streptosele sp. Subulinidae Subulina octona Bruguiére, 1792 Myriapoda Chilopoda Scolopendridae Scolopendra subspinipes (Leach, 1918) Diplopoda Spirostreptidae Seychelleptus seychellarum (Desjardins, 1834) Sphaerotheridae Cyliosomella furciparum (Brélemann, 1896) Trichopolydesmidae = Cylindrodesmus hirsutus (Pocock, 1888) Trigoniulidae Spiromanes ?braueri (Attems, 1900) Insecta Blattodea Blattidae Periplaneta americana (Linnaeus, 1758) Periplaneta australasiae (Fabricius, 1775) Coleoptera Cerambycidae Olenecamptus bilobus (Fabricius) Cicindelidae Myriochile melancholica perplexa (Dejean, 1825) Curculionidae Cratopus griseovestitus Linell, 1897 Cratopus aurostriatus Fairmaire, 1892 Rhipiceridae Callirhipis philiberti Fairmaire, 1891 Scarabaeidae Oryctes monoceros (Olivier, 1789) Perissosoma grande (Scott, 1912) Protaetia maculta (Fabricius, 1775) Hemiptera Cicadoidea Antankaria (Chremistica) pu/verulenta (Distant, 1905) Hymenoptera Anthophoridae Xylocopa cafjra (Linnaeus, 1767) Apidae Apis mellifera adansoni Latreille, 1804 Formicidae Anoplolepis gracilipes (Smith, 1857) Cardiocondyla emeryi Forel, 1881 Monomorium ?fossulatum Emery, 1894 Monomorium floricola (Jerdon, 1851) __ 166 Table 6 (cont.) Order Family Species Hymenoptera (cont.) Formicidae (cont.) Odontomachus troglodytes Santschi, 1914 Plagiolepis ?alluaudi Emery, 1894 Tapinoma melanocephalum (Fabricius, 1793) Technomyrmex albipes (Smith, 1861) Megachilidae Chalcidoma disjuncta (Fabricius, 1781) Sphecidae Trypoxylon sp. (T. errans or T. scutifrons) Vespidae Delta alluaudi (Perez, 1895) Polistes olivaceus (de Geer, 1773) Rhynchium brunneum (Fabricius, 1773) Lepidoptera Lycaenidae Leptotes pirithous Linnaeus, 1767 Zizeeria knysna (Trimen, 1862) Zizula hylax (Fabricius, 1775) Noctuidae Achaea mercatoria (Fabricius, 1775) Anticarsia irrorata Fabricius, 1781 Trigonodes hyppasia (Cramer, 1780) Nymphalidae Hypolimnas misippus (Linnaeus, 1764) Hypolimnas ?bolina Drury, 1773 Melanitis leda africana (Linnaeus, 1758) Pyralidae Spoladea recurvalis (Fabricius, 1787) Diaphana indica (Saunders, 1851) Endotricha mesenterialis mahensis Whalley Sphingidae Acherontia atropos (Linnaeus, 1758) Cephnodes hylas virescens (Wallengren, 1865) Neuroptera Myrmeleonidae Myrmeleon obscurus Rambur, 1842 Odonata Libellulidae Orthetrum stemmale wrightii (Selys, 1877) ?Pantala flavescens (Fabricius, 1798) Tramea limbata Selys, 1878 Orthoptera Gryllidae Gryllodes supplicans (Walker, 1859) Mogoplistidae Ornebius elegantulus (Boliver, 1912) Phalangopsidae Seychellesia longicercata (Boliver, 1912) Tettigonidae Ruspolia differens (Serville, 1838) Conocephalus iris (Serville, 1838) VERTEBRATES Reptiles Four species were recorded, all lizards: two day geckos (Phelsuma sundbergi and a smaller species, possibly P. astriata), a third gecko (a pink-bodied juvenile, observed on ruined buildings on the plateau: probably a young Pacific house gecko Gehyra mutilata), and one skink, Mabuya sechellensis. A fifth species, bronze-eyed gecko Ailuronyx seychellensis, has been recently recorded (Shah and Parr, 1998) although not observed during the current study. Both 4. seychellensis and the large skink Mabuya wrightii were collected on Marianne by Lantz in 1877 (Cheke, 1984) and M. wrightii now appears to be extinct, probably due to the introduction of rats since 1877. No snakes were recorded, although the introduced fossorial snake Ramphotyphlops braminus 1s likely to be present as it was commonly spread to agricultural islands (Nussbaum, 1984a). Giant tortoises, presumably an endemic taxon of the granitic islands, were recorded in 1787 but had become extinct before 1875 (Bour, 1984). 167 Birds Birds were surveyed by observation and using tape playback. In October 1999, playback of taped calls was used in locations around the island to give an indication of the number of individuals of the endemic Black Paradise Flycatcher. Tape playback of Scops Owl Otus insularis was carried out on one night (27/10/99). The endemic Black Paradise flycatcher was observed on several occasions in three locations: 1) In mango trees at/near plot D10, once spontaneously (22/10/99) and once to tape (26/10/99); 2) Atthe northern end of the island, to tape (26/10/99); 3) Peak of Estel Hill, to tape (27/10/99, 28/10/99). All responding individuals were females. It is possible that these were multiple records of the same bird, but seems more likely that there were at least two individuals. Among the granitic islands, Marianne is unique in the quality of records of its bird fauna. Because plantation development occurred later here than on other islands in the group, naturalists of the 19" century were able to record the extant fauna, at a time when endemic species were extinct, or were being lost, on most other islands. The most complete records are those of Newton (1867). Abbott collected specimens on Marianne (and other islands) in 1890 (Ridgway, 1895). The past and present endemic avifauna of Marianne Island are summarised in Table 7. Table 7. Past and present endemic land birds, Marianne Island. Species Late 19" — early 20" century 1999-2000 Falco araea Seychelles kestrel Present 1866: Streptopelia picturata Seychelles turtle dove** Present 1866! Subspecies rostrata effectively extinct Alectroenas pulcherrima Seychelles blue pigeon Present 1866! Present Coracopsis nigra barklyi Seychelles black parrot** Reported numerous prior to 1866, but locally extinct by then’ Hypsipetes crassirostris Seychelles bulbul Present 1866' Copsychus sechellarum Seychelles magpie-robin Present 1866! and 1890° Acrocephalus Seychelles warbler (?) Recorded 1936° sechellarum Terpsiphone corvina Seychelles black paradise Present 1890°, 1936° Present, rare flycatcher Nectarinia dussumieri Seychelles sunbird Numerous 1866' Present Zosterops mayottensis Chestnut-flanked white- Present 1866' (first described Seychelles semiflava ery from Marianne specimen) and subspecies 1890° extinct Foudia sechellarum Seychelles fody Present 1866! (first described from Marianne specimen) and 18907 ** Endemic subspecies ' Newton, 1867 * Ridgway, 1895 *Vesey-Fitzgerald, 1936 168 In total, 12 land birds and waders were observed on the island during the current survey (Table 8), including three endemic species. Seabirds observed included fairy terns Gygis alba (common in breadfruit trees around the settlement, where they probably breed), common noddy Anous stolidus, white-tailed tropicbird Phaeton lepturus and frigate birds Fregata spp. (all observed occasionally offshore). In March 2002 a wedge- tailed shearwater Puffinus pacificus was heard calling in flight over the plateau at 8pm. Table 8. Land birds and waders recorded on Marianne. M = migrant species; E = Seychelles endemic species. Species Notes Butorides striatus green-backed heron Gallus gallus domestic chicken Dromas ardeola M crab plover Numenius phaeopus M whimbrel common sandpiper ruddy turnstone Actitis hypoleucos M Arenaria interpres M Streptopelia picturata picturata Geopelia striata Madagascar turtle dove barred ground dove Alectroenas pulcherrima E Seychelles blue pigeon Seychelles paradise flycatcher Terpsiphone corvina E Nectarinia dussumieri E Seychelles sunbird Acridotheres tristis Foudia madagascariensis common mynah Madagascar fody Mammals Up to three individuals regularly observed in rocky shallows near La Cour; one (abandoned) nest in Euphorbia. Several feral individuals, both sexes and young. One individual on beach, 18/10/99 One individual on beach, 21/10/99. Two individuals regularly on beach, March. One individual on beach, 25/10/99 Seen on two occasions, on glacis at the southern tip of the island. Seen regularly on beach, March Observed fairly regularly around La Cour in Tabebuia forest. A few individuals observed, in disturbed or open habitats. In October, only one individual observed 26/10/99, feeding on Canthium berries. In March seen more frequently, especially in fig trees. October: at least three individual female birds found in an extensive survey of the island using tape playback of calls. March: several females observed. Very common everywhere. Several nests found, March. Common. Apparently rare: one male in breeding plumage observed 21/10/99. Females occasionally seen in Tabebuia forest near La Cour. Table 9 shows mammals observed in the course of the survey. In addition, rodent trapping was carried out in October 1999 and March 2000 (Table 10). Two trap-lines were established, both in hill woodland/scrub (former plantation). Only one species of rodent, the ship rat Rattus rattus, was trapped. Trapping rates were relatively low, although slightly higher in October than in March. Marianne has abundant fruit trees (especially mangoes and oranges) with fruit in season on both visits, and the availability of alternative food sources could influence the readiness of rats to enter traps. 169 Table 9. Mammal species observed, Marianne. Species Notes Bos taurus L. Cattle One individual Felis catus L. Domestic cat Rarely observed Pteropus seychellensis Milne- Seychelles fruit bat | Abundant, observed travelling between Edwards Marianne and other nearby islands (including La Digue, Félicité) Rattus rattus L. Ship rat Abundant Table 10. Results of rat trapping. Dates Trap-nights No. of rats Rats per 100 trap- _—Rats per 100 trap- nights nights (uncorrected) (corrected)* 23 — 28/10/99 140 31 22.14 25.20 10 — 14/3/00 2 20 17.86 19.80 Total (SE) 35.34 Total (NW) PD) 53\0) *Corrected to account for the effect of closed traps: Cunningham and Moors, 1996 CONSERVATION RECOMMENDATIONS Given Marianne’s documented history, it is of great conservation interest. Perhaps less than 100 years ago the island supported a greater range of endemic birds than any other of the central Seychelles islands. The loss of habitat, combined with the introduction of predators, caused the local extinction of most species. In addition, the presence of phosphatic rocks suggests that substantial colonies of seabirds existed. Marianne is obviously capable of supporting viable populations of endemic land birds, but two major factors have to be addressed before re-introductions could be considered: introduced predators and habitat suitability. Specific actions that need to be taken include the control or eradication of introduced predators (particularly rats and cats) and the removal of introduced plant species and coconut scrub regenerating under the former coconut plantation. The introduced crazy ant Anoplolepis gracilipes is a potential threat on the island. Areas of the forest were dominated by this ant species which can have extreme effects on plant and invertebrate communities (Hill ef a/., in prep.) with probable higher-order effects for vertebrates. At present, there are no instances of established populations of crazy ants being eradicated in the Seychelles. The presence of Seychelles black paradise flycatchers on the island is of particular interest, given that the bird was thought to be restricted to La Digue prior to 1999. Records of the species by Shah and Parr (1998) and the current survey suggest that the number of individuals on the island is small; no adult males were recorded on visits in 1999 and 2000, although it is possible that juvenile males (with plumage similar to the female) were present. Even if males occur there, the small population on Marianne is undoubtedly vulnerable to extinction, especially given the presence of predators (rats and cats) on the island. However, these predators should not necessarily preclude the survival 170 of the paradise flycatcher on Marianne; on La Digue, a large, established population of the bird survives alongside a range of predators (including Seychelles bulbul, absent from Marianne). In order to encourage the paradise flycatcher to establish a viable population on Marianne, thus extending the species’ range and reducing the possibility of extinction, the population of birds on Marianne could be enhanced by managed translocations, preferably in combination with attempts to reduce populations of introduced predator species. 171 Appendix 1. Plant species recorded from Marianne Taxonomy of dicotyledons as given by Friedmann (1994). Of monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>1000 individuals observed); C = Common (100 - 1000 individuals observed); F = Frequent (10 - 100 individuals observed); Occasional (3 - 10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: Cu = Cultivated area; Ma = Marsh; PG = Plateau Grassland; HW = Hill Woodland/scrub; HG = Hill Grassland; Gl = Glacis; BC = Beach Crest. Species Status Abund. Habitats Notes PTERIDOPHYTA Adiantaceae 1 Acrostichum aureum L. N O BC 2 Pityrogramma calomelanos (L.) Link. 21 R HW Davalliaceae 3) Davallia denticulata (Burm.) Mett. N O HW 4 Nephrolepis biserrata (Sw.) Schott N A HW, HG Polypodiaceae 5) Phymatosorus scolopendria (Burm. f.) N A HW Psilotaceae 6 Psilotum ?nudum Sw. N F HW ANGIOSPERMAE: Dicotyledons Acanthaceae 7 Asystasia sp. B (sensu Friedmann) 71 A HW, Gl Amaranthaceae 8 Achyranthes aspera (L.) DC. I O HW 9 Alternanthera sessilis (L.) DC. I O Ma Anacardiaceae 10. Anacardium occidentale L. I O HW 11. = Mangifera indica L. I A HW, PG 12. Spondias cytherea Sonn. I O HW Annonaceae 13.) Annona muricata L. I A HW, PG 14. Annona reticulata L. F HW 1S = Annona squamosa L. O HW Apocynaceae 16 Catharanthus roseus (L.) G. Don. I C HW, Gl 17. = Ochrosia oppositifolia (Lam.) Schum. N R HW 18 Tabernaemontana coffeoides Boj. ex A. DC. N (C HW Araliaceae 19 Gastonia sechellarum (Baker) Harms. var. E (o HW sechellarum Asclepiadaceae 20 Sarcostemma viminale (L.) Alton N O HW, Gl Avicenniaceae 21 ~— Avicennia marina (Forssk.) Vierh. N R BC Bignoniaceae 22 Tabebuia pallida (Lindl.) Miers. I A HW 172 Species Status — Abund. Habitats Notes Boraginaceae 23 Cordia subcordata Lam. N O PG, BC Caesalpiniaceae 24 ~~ Caesalpinia bonduc (L.) Roxb. N F HW 25. Senna occidentalis (L.) Link I O PG, HW 26 Tamarindus indica L. I O HW Capparidaceae 27. — Cleome viscosa L. I O Gl Caricaceae 28 ~~ Carica papaya L. I O Cu, HW Casuarinaceae 29. Casuarina equisetifolia J. R. & G. Foster I O BC Combretaceae 30 Terminalia catappa L. 2N C BC, PG, HW Compositae 31 = Emilia sonchifolia (L.) Wight I Cc PG, Gl 32. = Synedrella nodiflora (L.) Gaertn. I A PG 33. -—- Tagetes patula L. I R Cu Only in garden 34 Vernonia cinerea (L.) Less. I A PG Convulvulaceae 35. Ipomea batatas (L.) Lam. I F Cu 36 = Ipomoea macrantha Roem & Schult. N 13 HW 37. Ipomoea pes-caprae (L.) R. Br. N A BE, RG Cucurbitaceae 38 = Cucurbita moschata (Lam.) Poir. FE Cu Only in garden 39 Lagenaria siceraria (Molina) Stand. K Cu Only in garden Euphorbiaceae 40 = Acalypha indica L. I A PG 41 = Euphorbia hirta L. I A PG, Cu 42 Euphorbia pyrifolia Lam. N F HW, Gl 43. Euphorbia thymifolia L. I C PG, Cu 44 Jatropha curcas L. I O HW 45 Manihot esculenta Crantz I O Cu, HW 46 ~~ Pedilanthus tithymaloides (L.) Poit. I R HW 47 — Phyllanthus amarus Schumach. & Thonn. I A PG 48 ~~ Phyllanthus pervilleanus (Ballon) Mill. Arg. N F HW Flacourtiaceae 49 Flacourtia jangomas (Lour.) Réuschel I F HW Goodeniaceae 50 = Scaevola sericea Vahl. N A BC, HW Guttiferae 51 Calophyllum inophyllum L. N A HW, BC Labiatae 52. Ocimum basilicum L. O Gl 53. = Ocimum ?tenuiflorum L. O Gl 54 — Plectranthus amboinicus (Lour.) Spreng. I Fi Gl, HG 55 Plectranthus prostratus Girke I R Sc 56 Solenostemon scutellarioides (L.) Codd I R Cu Only in garden Lauraceae 7 Cinnamomum verum Presl. I R HW 58 Persea americana Mill. I O HW Lecythidaceae 59___Barringtonia asiatica (L.) Kurtz N O BC 173 Species Status Abund. Habitats Notes Malvaceae 60 Abutilon indicum (L.) Sweet 21 R HW 61 Hibiscus tiliaceus L. N O HW 62 Sida acuta Burm. F. I A PG, HW 63. Sida cordifolia L. 2N C Gl 64 Thespesia populnea (L.) Soland. Ex. Correa N F BEyERG 65 Urena lobata L. ?] A PG, HW Meliaceae 66 Xylocarpus moluccensis (Lam.) Roem. N I9 BC Mimosaceae 67 Adenanthera pavonina L. I O HW 68 Leucaena leucocephala (Lam.) de Wit I F HW 69 = Pithecollobium unguis-cati (L.) Benth. I O HSc Moraceae 70. =‘ Artocarpus altilis (Parkins.) Fosb. I O PG 71 ~~ ~Ficus lutea Vahl. N C HW 72 ‘Ficus reflexa Thunb. ssp. seychellensis (Baker) __ E (ss) J3 HW, PG Berg 73 Ficus rubra Vahl. N C HW, PG Moringaceae 74. ~~ Moringa oleifera Lam. I O HW Myrtaceae 75 ~-Psidium guajava L. I C PG, HW 76 ~=- Syzygium wrightii (Baker) A. J. Scott O HW Onagraceae 77 ~~ Ludwigia octovalvis (Jacquin) Raven 21 € Ma Papilionaceae 78 Abrus precatorius L. 2N A HW 79 Desmodium incanum DC. I A HW 80 Desmodium triflorum (L.) DC. I (C HW 81 Teramnus labialis (L.) Spreng. I (SE HW 82 Vigna marina (Burm.) Merr. N F PG, Ma Passifloraceae 83. ~~ Passiflora foetida L. I is HW 84 = Passiflora suberosa L. ] C HW Portulacaceae 85 Portulaca oleracea L. 2N F PG, Gl Rubiaceae 86 = Canthium bibractatum (Baker) Hiem. N A HW, Gl 87 Guettarda speciosa L. N O BC 88 Morinda citrifolia L. 21 A HW 89 = Paragenipa wrightii (Baker) F. Friedmann E F HW 90. = Pentadon pentandrus (Schumach. & Thonn.) I R Gl Vatke 91 Tarenna sechellensis (Baker) Summerh. E C HW Rutaceae 92. ~~ Citrus aurantifolia (Christm.) Swingle I O HW 93 Citrus medica L. I O HW 94 ~— Citrus reticulata Blanco I F HW 95 Citrus sinensis (L.) Osbeck I A HW 96 Murraya koenigii (L.) Spreng. I R HW 97 Murraya paniculata (L.) Jack I F HW 174 Species Status — Abund. Habitats Notes Sapindaceae 98 — Allophyllus pervillei Blume N R HG, HW 99 ~~ Cardiospermum halicacabum L. 2N E HW, Gl Sapotaceae 100 Mimusops sechellarum (Oliv.) Hemsl. IE F HW Scrophulariaceae 101 = Striga asiatica (L.) O. Kuntze ?] O HG Solanaceae 102. Capsicum frutescens L. I R Cu Only in garden 103. Datura metel L. I (Sc PG 104 Physalis angulata L. I O PG 105 Solanum melongena L. I Ke Cu Only in garden Tiliaceae 106 Triumphetta rhomboidea Jacq. I Cc GIAEG; Turneraceae 107 Turnera angustifolia Miller I A HW Verbenaceae 108 Phyla nodiflora (L.) Greene I O PG 109. Premna serratifolia L. N A HW 110 Stachytarpheta jamaicensis (L.) Vahl. I O HGaeG 111 Stachytarpheta urticifolia (Salisb.) Sims. I A HW 112 Vitex trifolia L. I C PG, Ma ANGIOSPERMAE: Monotyledons Agavaceae 113. Furcraea foetida (L.) Haw. I O HW Amaryllidaceae 114 Hymenocallis littoralis (Jacq.) Salisb. 21 Ig PG 115. Zephyranthes rosea Lindl. I R PG Araceae 116 Alocasia macrorrhiza (L.) G. Don. I O HW Bromeliaceae 117. Ananas comosus (L.) Merr. I O HW, Gl Commelinaceae 118 Commelina sp. ¥ O HW Cyperaceae 119 Cyperus compressus L. z O PG, Gl 120 Fimbristylis cymosa R. Br. u € Gl 121 Fimbristylis dichotoma (L.) Vahl. D A PG 122 Fimbristylis sp. (glacis sedge) ? € Gl 123 Kyllinga alba Nees v fi HW 124 Kyllinga polyphylla Willd. ex Kunth N C HW, Gl 125. Mariscus dubius (Rottb.) Fischer N (S HW, PG, Gl 126 Mariscus pennatus (Lam.) Domin. N C Ma 127 Pycreus polystachyos (Rottb.) P. Beauv. ¥ C Ma, Gl 128 Thoracostachyum floribundum (Nees) C. B. Cl. 8 O HW Gramineae 129 Bambusa vulgaris Scrad. ex Wendl. I R HW 130 Brachiara umbellata (Trin.) W. D. Clayton N A HW, Gl 131 Cenchrus echinatus L. v O RG 132. Chloris barbata (L.) Sw. 2 O Gl 133. Dactyloctenium ?ctenoides (Steud.) Bosser ? A PG 134 Digitaria ?didactyla Willd. N A HG 135 Digitaria ?horizontalis Willd ? F PG 175 Species Status _Abund. Habitats Notes 136 Enteropogon sechellensis (Baker) Dur. & N A PG, Gl Schinz 137. Eragrostis ?tenella (L.) P. Beuv. insularis Z O Gl Hubb. 138 Oplismenus compositus (L.) P. Beuv. N O HW 139 Paspalum ?scrobiculatum L. ? O HW 140 Pennisetum polystachyon (L.) Schult. x O Gl 141 Sporobolus virginicus (L.) Kunth. N CS BC 142 Stenotaphrum dimidiatum (L.) Brogn. N C HW 143. Stenotaphrum micranthum (Desv.) C. E. Hubb. U A HG 144 sp. indet. (?Brachiaria sp.) B € HW Liliaceae 145 Dracaena reflexa Lam. var. angustifolia Baker N A HW Musaceae 146 Musa sapientum L. I F Cu, HW Orchidaceae 147 Disperis tripetaloides (Thouars)Lindl. N F HW 148 Vanilla planifolia Andrews I A HW Palmae 149 Cocos nucifera L. N A HW, HG, EGHBE Pandanaceae 150 = Pandanus balfourii Mart. Ig, O BC, HW 151 Pandanus utilis Bory I € HW Taccaceae 152 Tacca leontopetaloides (L.) O.Kuntze ? F HW Leqend NS \ X m a T Contours Vegetation plots Marsh Buildings Beach Cemetery Grand Paloss Bernica Figure 1. North Island physical, with locations of vegetation plots. | 200 metres NORTH ISLAND BY! MICHAEL J. HILL', TERENCE M. VEL!, KATY HOLM”, K., STEVEN J. PARR? and NIRMAL J. SHAH! GEOLOGY, TOPOGRAPHY AND CLIMATE North Island has an area of 201 ha, and is the ninth largest of the granitic Seychelles Islands. At its highest point (Grand Paloss) it reaches over 180 m above sea level. The island’s north-south axis is made up of raised rocky hills with an outlier (Congoment) to the east. Along the eastern and western sides of the island are two large low-lying “plateau” areas. Geologically, the island differs from most of the granitic islands of Seychelles apart from its nearest neighbour Silhouette. Both islands are made up of syenite resulting from volcanic activity. These rocks are of much more recent origin than the bulk of Seychelles granite; Mahé and Praslin granites have been dated at about 650 million years old (Braithwaite, 1984) and Silhouette syenite at 63 million years old (Stephens, 1996). The plateaux are made up of recent calcareous sediments covered (on the landward side) with 20-30 cm depth of weathering products from the syenite hills (Baker, 1963) and, in places, marsh deposits. The island’s soils are varied. On the lower slopes of the hills Bernica and Basin Jean, and parts of the eastern plateau, Seychelles red earths occur, with some river valley soils in seasonal stream beds. On the western plateau, soils are of the Jemo series. The eastern plateau has soils of the Shioya series (DOS, 1966). Around the base of the hill, on the eastern plateau, is a complex of marshes varying in extent according to season. North Island is relatively remote. The nearest island is Silhouette, c. 7 km away. The Seychelles islands experience a seasonal humid tropical climate (Walsh, 1984). Historical weather data for North Island are limited, although more complete data have been collected in recent years. Monthly rainfall for the period 1975-80 is shown in Table 2. Total rainfall on North Island for this period was considerably lower than that on the nearby higher island of Silhouette which reaches an altitude of 621 m as! (annual mean rainfall for Silhouette = 2,082.5 mm: North Island = 1,516.9 mm). ' Nature Seychelles, PO Box 1310, Mahé, Seychelles. Email: birdlife@seychelles.net 21991 Casa Marcia Crescent Victoria, British Colombia, Canada. Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, UK. 178 Table 1. Area of North Island by altitude (calculated from maps published by Directorate of Overseas Survey (UK)/Seychelles Government). Altitude range (m. asl.) Area (ha) Percentage total area 150 - 200 5 be) 100 - 150 17 8.5 50 - 100 3) 25.4 10 - 50 61 30.3 0 - 10 67 33 Table 2. North Island: monthly rainfall (mm), 1975-1980. (Data: National Meteorological Services, Seychelles, unpublished data). n/a = not available. Jan Feb Mar Apr Ma Jun Jul Au Se Oct Nov Dec 1975 454.9 151.6 65.7 30.4 84.8 15.4 6.3 48.7 n/a 3.8 286.0 224.0 1976 260.1 366.0 50.0 180 208 355 21.0 29.7 20.3 26.9 n/a 279.4 1977 Bie NA Sie ea GSO) 29.2 76.5 48.3 ISO esis. Si 25.2 1978 349.0 220.5 848 2469 66.3 40.9 24.4 0.8 39.1 95.8 397.3 n/a 1979 QAO ASSIS) 29058 ZOOS aes 10.4 83.1 21.3 ORO elt 920 n/a 169.7 1980 Wiles 830)7/ n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a Mean 291.2 2285 1086 147.6 50.8 26.3 42.3 29.8 18:6. LOL-8> S27 1ESF SSX HISTORY Written references on the island’s history are few although it was one of the first islands to be visited by man. On the fourth voyage of the East India company in 1609, the granitic Seychelles were first discovered by western mariners (Lionnet, 1986). Ina written account of the voyage by John Jourdain, there are records of landings on two islands, one of which (later identified as North Island by W. Wharton) had no fresh water but did have giant land tortoises, which were collected for food (Foster, 1905). “Pirate markings” inscribed on rocks on Congoment may pre-date official settlement of the Seychelles islands, which occurred in 1770. Within 17 years of permanent human settlement of the archipelago, North Island was overrun by rats, although the tortoises mentioned by Jourdain were still present. Malavois (1787: in Fauvel, 1909) records that North Island **...18 now little wooded, having been burned down several years ago. In the small plain...one would find sufficient land to have a small habitation, but it would require the destruction of rats that now populate the island. The most beautiful tortoises of the archipelago are to be found there, and [green] turtles also come ashore. But Caret [hawksbill turtle] is almost MEVEMSEeIy The tortoises, presumably species of the granitic islands, became extinct before 1875 (Bour, 1984). In the early twentieth century, North Island guano was exploited on a 179 small scale for export. The guano was low grade; it was reported to contain 2-3% iron oxide and was also unusually rich in magnesium and aluminium as a result of contamination with syenitic soil (Baker, 1963). Evidence of guano processing remains in physical features and soils; an artificial mound at Petite Anse (between Congoment and Bernica) is labelled “guano siftings” on the map of 1976 (Seychelles Government and UK Directorate of Overseas Surveys, 1976). The eastern plateau of North Island has Jemo series soils (DOS, 1966), which form on the plateaux of seabird islands and are also found on Cousin, Cousine, Aride and Frégate. In the late nineteenth or early twentieth century, extensive plantations of coconut and fruit trees were made over the plateau areas. North Island exported a variety of agricultural produce to Mahé. In recent years, the plantations of North Island have declined and been abandoned; in 1997, there was one family managing a small farm with domestic animals on the island (Shah and Parr, 1997). North Island was bought by Wilderness Safaris Ltd. in 1997, with the purpose of developing a tourism and conservation project. Since this time there has been intermittent human presence on the island and some domestic animals survive in a feral state. FLORA AND VEGETATION Flora In total, 188 plant species were recorded on North Island, including 12 ferns, one cycad and 175 angiosperms (Appendix 1). Of the angiosperms, 108 species (61.7%) are regarded as introduced (Friedmann, 1994) and 42 (24.0%) native. Only one of these native species (Pandanus balfourii) was endemic to the Seychelles, although the list also included an endemic subspecies (Ficus reflexa seychellensis). The flora of North Island shows a greater proportion of introduced species and a smaller number of endemics than the flora of Seychelles as a whole (of the total Seychelles flora, around 54% are introduced and 9% endemic; Procter, 1984). Within the granitic Seychelles, larger islands tend to have more endemic species, but the number on North Island was similar to that on a much smaller island, Cousin (29 ha). The small number of endemic taxa probably reflects the island’s history of cultivation and the accessibility of most of the island (compared with, for example, the broken rocky topography of Félicité). Fire may also have contributed to the loss of endemic species; in 1972, a bush fire destroyed vegetation throughout the northern hill including Grand Paloss and Basin Jean. The area destroyed by fire included the highest parts of the island and those of lesser economic value where endemic species might have survived. It has been suggested that an endemic labiate (called Coleus subfrutectosus Summerhayes by Robertson, 1989) survives on North Island. However, this plant is probably a vigorous variety of the introduced Plectranthus amboinicus (Friedmann, 1994). Of the introduced plants established on North Island, at least 16 can be regarded as invasive weedy species (Carlstrém, 1996a: Fleischmann, 1997). The most abundant are lantana Lantana camara, cocoplum Chrysobalanus icaco, guava Psidium guajava, strawberry (Chinese) guava Psidium cattleianum, and Alstonia macrophylla. One potentially invasive species Clidemia hirta appears to be a recent introduction from 180 Silhouette, probably arriving as bird-sown seed. In addition to these alien species, the coconut Cocos nucifera, although probably native to the Seychelles, is present in extremely high numbers to the exclusion of other plants. Several previous workers have produced plant species lists for North Island; species recorded in the past but not in the current survey are shown in Appendix 1. While some of these species (notably cultivated herbs) may now be extinct, others such as fruit trees probably survive in small numbers, and grasses may have been overlooked in the current survey. Eighteen species recorded by previous authors may survive on North Island (13 of these introduced species), bringing the total species list to 206. Vegetation The extents of major vegetation types on North Island are shown in Table 3 and Figure 2. The plateaux are dominated by former coconut plantations, with a dense shrub layer of Lantana camara and Psidium gujava. The plateau also has areas of native woodland (mainly takamaka Calophyllum inophyllum and Terminalia catappa), mixed woodland (rich in fruit trees) and marshland vegetation. The hills are generally dominated by mixed coconut woodland and scrub with large areas of open rock. In total, 40 vegetation plots were completed, 20 in August and 20 in January- February. In total, these covered 4,009 m’ or 0.2% of the island’s surface. Twenty vegetation plots were in plateau broad-leaf woodland (excluding areas identified on the map as coconut), covering 2,000 m? or 0.8% of this habitat type. Twenty vegetation plots were in hill woodland/scrub (excluding areas identified on the map as bare rock), covering 2,000 m’ or 0.2% of this habitat type. A summary of results is shown in Table 4. Table 3. Extent of major vegetation types, North Island. Vegetation type Approx. area (ha Hill Woodland (predominantly native) 4 (10 masl) Woodland (predominantly introduced) 86 Coconut with regeneration 2 Scrub (mixed) 12 Scrub (introduced) 9 Bare rock 22 Plateau Woodland (predominantly native) 12 (<10 masl) Woodland (predominantly introduced) 12 Coconut with regeneration 28 Scrub (introduced) 2 Beach crest vegetation <1 Freshwater marsh Grassland/garden 3 Bare rock 9 Table 4. Vegetation plot summary. Bare Dead wood Mean Mean Meanshrub Meanherb Open leaf altitude trees layercover layer cover litter rock (pieces per m asl ha’! lot 20 <5 785 32 8855 60.8 1.8 0.3 Habitat Plots Plateau woodland Hill woodland 20 54.6 445 Eo8) 52.4 18.3 BQH) 0.4 18] Legend: vegetation types Aa] Agati, Adenanthera pavonina [RA Albizzia, Parasenanthes falcatana Alstonia macrophylla AY Beach crest trees Casuanna Coconut with scrub Coconut with dense regrowth Intl Coconut-dominated exotic woodland 3 3 Cocoplum scrub do - 5 \/] Exotic scrub (lantana, guava) Native scrub, glacis vegetation x Mixed exotic woodland ° °, © Native woodland, mainly Ca/ophyllum Ot: Marsh Grassland | ee Bare rock 200 metres Figure 2. North Island vegetation. 182 Plateau woodland plots had a relatively high density of trees and sparse shrub and herb layers. The tree layer was dominated by native trees: 92.4% of individual trees were native. The most abundant species was takamaka Calophyllum inophyllum (124 trees, 78.5%). The second most abundant species was Cocos nucifera (18 trees, 11.4%) indicating that plateau woodland 1s expanding into areas of former coconut plantation. The most widespread species of the shrub layer were Cocos (in 17 of 20 plots with mean cover of 6% in plots where it occurred), Calophyllum (in 15 of 20 plots with mean cover of 19% in plots where it occurred), and Psidium guajava (in nine plots, mean cover 19%). The herb layer of plateau woodland was relatively species-rich containing a total of 45 species in 2,000 m*. The most widespread species was Cocos, which occurred in 16 of 20 plots. However, Cocos was not the major component of the herb layer in terms of percentage cover; the mean percentage cover per plot was 4%. Calophyllum occurred in 12 plots with a mean cover of 4%. The native fern Nephrolepis biserrata occurred in the herb layer of 12 plots with an average of 24% plot cover where it occurred. The 20 plots carried out in hill woodland and scrub were much more open than those on the plateau with a lower number of trees and shrubs but with a dense herb layer. The tree layer was more mixed than the takamaka-dominated plateau woodlands; a total of 12 tree species were recorded (as opposed to eight on the plateau) but had many more introduced trees; 48.3% of individual trees belonged to introduced species. The most abundant plant in the tree layer was Cocos (35 trees, 39.3% of all trees). Casuarina was also abundant (16 trees, 18.0% of all trees). Cocos was also the most widespread species in the shrub layer occurring in 17 of 20 plots with a mean coverage (in plots where it occurred) of 19%. The herb layer was dominated by Nephrolepis biserrata, which occurred in all plots with a mean coverage of 39%. Cocos occurred in 12 plots with mean cover of 10%. Although plateau woodland contains some introduced fruit tree species, it is dominated by native trees and shows signs of natural expansion into areas of coconut plantation. Unfortunately, a large number of takamaka trees have been affected by the takamaka wilt disease, probably caused by the fungus Leptographium (Verticillium) calophylli (Ivory et al., 1996; Wainhouse, 1998). This disease was not recorded in 1997 (Shah and Parr, 1997). In May 1999, a few infected trees were noticed in the vicinity of the marsh. In August, a larger number of trees with symptoms of the disease were observed on the western plateau, around the marsh and in takamaka woodland to the west of the cemetery. In January 2000, the area of infection on the eastern plateau had noticeably spread and was visible from Congoment peak. A total of 126 trees showing 50% or greater loss of foliage were counted on the eastern plateau with at least two affected trees located on the western plateau. Some trees showed signs of regrowth but many appeared dead. In some patches of dead takamaka, the growth of saplings was affected by cattle grazing but in some places a range of saplings were present including Alstonia, Chrysobalanus, Calophyllum, Terminalia and fruit trees. The worst-affected forest areas were inland, with few beach-crest trees suffering symptoms. Takamaka wilt disease probably spread to North Island from Silhouette. Most of the hill has Cocos-woodland dominated by palms and introduced species occurring at low densities. On the northern hills, some of the older palms show signs of 183 blackening that probably occurred in the 1972 fire, showing that some trees survived this event. INVERTEBRATES Pitfall Trapping The pitfall trap assemblages were large compared to those of other islands (Table 5). Generally, pitfall assemblages were larger in plateau woodland than hill woodland or scrub and higher in the northwest monsoon season. The composition of assemblages also differed between the plateau and hill woodland (Fig. 3). Table 5. Pitfall assemblages from North Island: only invertebrates >2 mm included. (numbers in parentheses = excluding ants. Habitat Mean no. individuals per five traps SE season NW season OBroN (62) 113.3 (20.9) 44.6 (4.7) 68.5 (14.6) 61.8 (9.4) 61.1 (16.0) Plateau woodland Hill woodland/scrub North All granitic islands 100% - 90% - | &Mollusca % 80% - _ BAraneae Blattodea 710% - 60% 50% - | | {Coleoptera | & Dermaptera | W@ lsoptera 40% - | Dlarvae 30% MM Lepidoptera 20% others 10% - 0% - North Plat North Plat = North Hill = North Hill SE NW SE NW Figure 3. Composition of pitfall assemblages on North Island (including allinvertebrates over 2 mm body length, except ants). “Others” group includes Diptera, Hemiptera, Myriapoda, and wasps (Hymenoptera, exc. ants). 770 Plateau woodland sites were dominated by ants which made up 72° of pittall assemblages. The most abundant species was the native Technomyrmex albipes (35% of individuals) followed by Odontomachus troglodytes, which formed 31% of all individuals. Assemblages excluding ants were dominated by Dermaptera (earwigs) which made up 43% of plateau assemblages in the northwest monsoon season and 65% in the 184 southeast season. Blattodea (cockroaches) were also abundant on the plateau, forming up to 17% of the assemblage (in the northwest season). Hill sites were also dominated by earwigs, which formed 58-60% of the assemblage. Araneae (spiders) made up a larger part of the hill assemblage but cockroaches were less important. The crazy ant Anoplolepis gracilipes was not collected in pitfall assemblages suggesting that this introduced pest species is not present on the island. Since its arrival in Seychelles in the early 1960s (Haines ef a/., 1994), this ant has been introduced to many islands including Marianne and Félicité. On Bird Island especially high concentrations of ants have caused tree death (Hill, in prep.) and the eradication of native reptiles from large parts of the island (Feare, 1999). If North Island is free of crazy ants as these data suggest, it is important that efforts are made to prevent invasion. Leaf-insect Counts Leaf-insect counts were carried out for 13 tree and shrub species, seven of these in both seasons (Table 6). Six of the trees surveyed in both seasons had higher leaf counts in the August survey; only one had higher counts in the north west monsoon (Jan-Feb). As found on some other islands, the highest counts were for the shrub Morinda citrifolia (status uncertain-possibly introduced; Friedmann, 1994). Morinda is uncommon on North Island. Some introduced fruit tree species show exceptionally high counts, particularly in the dry season (August). High counts for Annona muricata are due to large numbers of soft bugs (Hemiptera; Sternorrhyncha) attended by ants. Table 6. Density of invertebrates on foliage, North Island. n= no. of leaves counted; NI = number of individual invertebrates. SE season (August) n mean NI mean NI leaf! m? NW season (Jan-Feb) n mean NI mean NI leaf! Species Introduced species Alstonia macrophylla 100 4.95 385.33 150 5.85 444.95 Anacardium occidentale 300 De 167.51 350 0.66 84.44 Annona muricata 300 4.00 1024.79 800 1.90 452.52 Chrysobalanus icaco 50 0.20 42.11 0 Ixora finlaysoni 50 0.10 18.94 0 Mangifera indica 62.62 100 0.32 55.88 Psidium cattleianum 350 0.09 20.97 Psidium guajava 267.56 450 0.44 118.79 Tabebuia pallida 300 1.29 226.30 Native species Calophyllum inophyllum 650 1.45 188.95 1350 1.40 167.13 Ficus lutea 310 8.76 616.31 150 4.73 338.74 Terminalia catappa 58.43 0 Status unknown Morinda citrifolia SS HlJS 0 Malaise Trapping Malaise trapping was carried out in hill and plateau woodland habitats in both seasons. Four Malaise traps (two in each habitat) were run in August 1999 and four in January/February 2000. Assemblages were larger in August (mean number of individuals (NI) = 830) than in Jan/Feb (mean NI = 346), but there was no consistent pattern between habitats. In August catches were higher on the plateau, and in January on the hill. Malaise trap assemblages included members of 12 invertebrate orders. In both seasons, the Diptera dominated assemblages (Diptera accounted for 80.3% of individuals in August, 66.7% in Jan/Feb). Other important orders included Lepidoptera (9.2% of assemblage in August, 8.0% in Jan/Feb) and Hymenoptera (5.9% of the assemblage in August, 16.5% in Jan/Feb). Observation A list of species observed or collected is given in Tables 7 and 8. Most invertebrates observed on North Island were of introduced or cosmopolitan species. In contrast to a previous recent list (Shah & Parr, 1997), no endemic species of butterfly (Lepidoptera, Rhopalocera) were recorded, suggesting that none are resident on the island. One lycaenid species, Zizula hylax, was present in extremely large numbers on plateau grassland/scrub habitats. This species, together with another of the lycaenids collected, Leptotes pirithous are recorded as using Lantana camara as a larval food plant (Davis & Barnes, 1991) although in Africa both take a wide range of plant species, especially members of the families Leguminosae (Fabaceae) (L. pirithous) and Acanthaceae (Z. hylax) (Larsen, 1996). On North Island, larvae of one lycaenid species (?Zizula hylax) were observed being attended by ants under fallen coconuts in short- cropped turf (including Desmodium and Stenotaphrum) at the settlement. Dragonflies (Odonata) were common throughout the island, especially close to the wetland areas, on every visit. A total of eight species were observed (Table 7) most of which were captured and detailed colour notes made. There was evidence for breeding of at least four species. Wain ef al. (1999) made a list of nine species for North Island (including Rhyothemis semihyalina and Anax guttatus, not recorded in the present survey). Larvae of two dragonfly species were collected in an underwater light trap in February. Other invertebrates observed in the marsh included water bugs (Hemiptera: ?Veliidae) and water boatmen (Hemiptera; Notonectidae). Table 7. Invertebrates: Odonata. Evidence for breeding Dates Coenagrionidae Ceriagrion glabrum (Burmeister, 1839) Egg laying, August August Ischnura senegalensis (Rambur, 1842) - January Aeshnidae Hemianax ephippiger (Burmeister, 1839) - August Libellulidae Diplocodes trivialis (Rambur, 1842) Egg laying, January August, January ?Pantala flavescens (Fabricius, 1798) - January ?Orthetrum stemmale wrightii (Selys, - August, January 1869) Tholymis tillarga (Fabricius, 1798) Tramea limbata (Selys, 1869) Egg laying, January August, January Egg laying, January August, January oO I oO S 186 Table 8. Invertebrates observed, excluding Odonata. Order Family Species Notes Mollusca: Gastropoda Subulinidae Lamellaxis ?javanicum (Reeve) In pitfall traps Crustacea: Decapoda Arachnida: Scorpiones Araneae Myriapoda: Diplopoda Chilopoda Insecta: Coleoptera Diptera Hemiptera Hymenoptera Lepidoptera Coenobitidae Ocypodidae Buthidae Tetragnathidae Trigoniulidae Geophilidae Scolopendridae Scarabaeidae Chironomidae Cicadoidea Notonectidae ?Veliidae Anthophoridae Apidae Formicidae Vespidae Lycaenidae Hesperiidae Reptiles and Amphibians ?Opeas sp. Subulina octona Bruguiére, 1792 Coenobita brevimanus Dana, 1852 Ocypode ceratophthalmus (Pallas, 1772) Ocypode cordimana Desmarest, 1825 Tsometrus maculatus (de Geer, 1778) Nephila inaurita (Walckenaer, 1841) Spiromanes braueri (Attems, 1900) ?Mecistophalus sp. Scolopendra subspinipes Leach, 1918 Oryctes monoceros (Olivier, 1789) 9 ?Antankaria (Chremistica) pulverulenta (Distant, 1905) Water boatman Water bug Xylocopa caffra (Linnaeus, 1767) Apis mellifera adansoni Latreille 1804 Camponotus hova Forel, 1891 Cardiocondyla emeryi Forel, 1881 Monomorium ?fossulatum Emery, 1894 Odontomachus troglodytes Santschi, 1914 Plagiolepis ?alluaudi Emery, 1894 Tapinoma melanocephalum (Fabricius, 1793) Technomyrmex albipes (F. Smith, 1861) Technomyrmex ?foreli Emery, 1893 Tetramorium bicarinatum (Nylander, 1846) Polistes olivaceus (de Geer 1773) Zizula hylax Fabricius, 1775 Zizeeria knysna Trimen, 1862 Leptotes pirithous Linnaeus, 1767 Borbo sp. VERTEBRATES In pitfall traps In pitfall traps On beaches In pitfall traps In pitfall traps Observed eating skink Larvae in marsh Heard on E. plateau, Jan. Observed in marsh, August Specimens collected, May In pitfall traps In pitfall traps In pitfall traps In pitfall traps In pitfall traps In pitfall traps In pitfall traps In pitfall traps In pitfall traps Abundant, grassland Abundant, grassland Abundant, grassland Abundant, grassland Five terrestrial reptiles and one amphibian were observed (Table 9). At least three of these species are introduced on North Island. Since breeding seabirds occurred there in the recent past, it is likely that Wright’s skink Mabuya wrightii also occurred on the island at least until alien mammals were established. 187 In addition to the land reptiles, two sea turtle species breed on the beaches of North Island: green sea turtle Chelonia mydas (L.) and hawksbill Eretmochelys imbricata. (L.). Tracks of the latter species were observed on the western beach in August. One of the native land tortoise species of the granitic Seychelles was recorded on North Island in 1609 and again in 1787, but the species had become extinct by 1875 (Bour, 1984). The Aldabra giant tortoise was introduced to the island in the twentieth century and a few large free-ranging individuals were present at the time of the survey. There was also evidence of successful breeding; two young tortoises (both with plastron length under 10 cm) were found. Table 9. Reptiles and amphibians, North Island. Status: E =endemic, I = introduced, N = native (in central Seychelles). Family Species Status Amphibians Raniidae Ptychadaena mascareniensis (Dumeril & Bibron, Mascarene frog 71 1836) Reptiles Gekkonidae _Gehyra mutilata (Wiegmann, 1835) Pacific house gecko I Phelsuma sp. {?P. longinsulae (Rendahl, 1939)] day gecko E Scincidae Mabuya sechellensis (Dumeril & Bibron, 1836) Seychelles skink E Testudinidae | Geochelone gigantea (Schweigger, 1812) Aldabra giant tortoise I Typhlopidae __Ramphotyphlops braminus (Daudin, 1803) Robb, 1966 _ Brahminy blind snake I Birds In total, 17 land birds and waders were recorded (Table 10). Three endemic species were observed; two of these (Seychelles sunbird and kestrel) undoubtedly breed on the island but one (Seychelles swiftlet) was only recorded for a few days, and these birds were probably temporary visitors from Mahé (the species is absent from Silhouette; Rocamora and Skerrett, 2001). Two of the introduced bird species recorded, barn ow! and common mynah, are potential nest predators of endemic birds. Barn owls were regularly observed on the island (by day and night), and 11 pellets were retrieved from one roost site. None of the pellets contained bird remains; all included rat bones and hair and three pellets had small pieces of cockroach (Periplaneta sp.) exoskeleton. In addition to sight records, tape playback was used to give data on presence or absence of four species. In both August 1999 and January 2000, calls of black paradise flycatcher Terpsiphone corvina, Seychelles white-eye Zosterops modestus, Seychelles scops owl Otus insularis and barn owl Tyto alba were played. There was a positive response for only one of these species, the barn owl (two birds flew to a palm close to the tape when calls were played on the night of 31/1/00). 188 Table 10. Land birds and waders recorded, North Island. M = migrant species; E = species endemic species. Species Notes Butorides striatus Green-backed heron Common at marsh. One nest on Congoment May Nycticorax nycticorax Black-crowned night One individual observed on eastern plateau, 10/5/99 heron Falco araea E Seychelles kestrel At least one pair, around Congoment (above settlement) Gallus gallus Domestic (feral) At least seven birds present (R. Slater-Jones, pers. comm.) chicken Gallinula chloropus Common moorhen Abundant at marsh (at least 30 individuals) Dromas ardeola M crab plover One individual, 30/1/00 and 1/2/00 Pluvialis squatarola M grey plover One on E. beach 23/8/99. Two or more individuals, on beaches, January Numenius phaeopus M Whimbrel One regularly at marsh and E. beach (August). Several, marsh and beaches (January) Calidris alba M Sanderling One individual with other shore birds, Grande Anse, January Arenaria interpres M Ruddy turnstone One, in marsh, 7/5/99. Several on beaches, January Geopelia striata Barred ground dove Common on plateau Streptopelia picturata Madagascar turtle Very common on plateau, especially in plateau and low picturata dove hill woodland Tyto alba barn owl One individual seen on Bernica, pellets found in two locations (May). One individual in two locations by day (Bernica and Basin Jean), pellets collected (August). Heard regularly from settlement (January), two individuals responding to taped call 31/1/00, marsh. Collocalia elaphra E Seychelles swiftlet Two individuals flying over settlement for several days in August. Nectarinia dussumieri E Seychelles sunbird Rarely observed. One group of five seen on Bernica (May) Acridotheres tristis Common mynah Common on plateau, especially in plateau coconut plantation Foudia madagascariensis Madagascar fody Occurring throughout the island, particularly glacis. Three nests observed. Occasionally in large groups (12-15). Table 11. Seabirds observed on North Island. Species Notes Phaeton lepturus white-tailed tropicbird Several observed flying over the island, especially on the North and West sides of Grand Paloss. Fregata sp. (?great) frigatebird Large group of frigatebirds (40 or more) observed in flight over Grand Paloss, January (KH). Anous tenuirostris lesser noddy One dead individual on western plateau (?shot), May 99. Feeding flock of noddies (?common or lesser) observed off eastern beach August 99. Gygis alba fairy tern One observed at sea off eastern coast, May 99: several observed in a feeding flock of noddies, off eastern beach August 99. 189 Although the presence of guano deposits on North Island suggests that colonies of seabirds occurred in the past, few seabird species were observed in the current survey (Table 11), and there was no evidence of breeding in any species. Mammals Mammals observed in the course of fieldwork were recorded (Table 12). In addition, rodent trapping was carried out in May and August 1999 and January 2000 (Table 13). On all occasions, only one species of rodent, the ship rat Rattus rattus, was trapped. Two traplines were established, one in coconut plantation on the eastern plateau (on DOS map of North Island, series DOS 104, edition 1-DOS 1976, grid ref. CL 0580 1428 — CL 0550 1425), and one in hill woodland (grid ref. CL 0513 1420 — CL 0495 1414). Trapping rates were highest in May, with very low rates in January/February. This observation fits the trend for rats to be more easily trapped in the dry season when water and food stress is more acute (Merton, 1999). Rats have a considerable conservation impact as do several other species present on the island including cats (as predators of vertebrates) and cattle. The herd of feral cattle on North Island (numbering about 30 individuals) has a great impact upon plateau ecosystems, destroying beach-crest vegetation (especially Scaevola) and freshwater vegetation (through grazing on 7ypha when marsh water levels are low), and causing physical disturbance and eutrophication of the marsh. Overgrazing and selective grazing may have favoured the establishment of an understorey of Lantana over much plateau grassland and the animals are responsible for distributing guava Psidium guajava around the plateau. Cattle also appear to have inhibited succession in some areas including the marsh and woodland habitats where heavy grazing and disturbance by cattle must have restricted the regeneration of Cocos. These effects are not entirely detrimental; disturbance of the marsh has probably prevented successional change and browsing affects mainly introduced species. However, if habitat restoration were to be initiated, cattle would have to be removed. In this case, an increase in the number of land tortoises would help to maintain open water in the marsh. Table 12. Mammals observed, North Island. Status 20-30 individuals several individuals observed around settlement, one individual caught in rat trap 1/2/00 not trapped on island, but a single individual found in grocery box prior to disembarkation to island May 2000 common throughout the island Bos taurus L. Felis catus L. Mus domesticus Rutty, 1772 Pteropus seychellensis Milne Edwards 1887 Sus domesticus Erxleben, 1777 Rattus rattus L. at least one individual survived in 2000: not seen, but signs observed abundant 190 Table 13. Results of rat trapping. Dates Trap-nights No. of rats Rats per 100 trap- Rats per 100 trap- nights (uncorrected) _ nights (corrected)* 14/5 — 19/5/99 47 38 74.5 - 23/8 — 28/8/99 140 39 ZS) 33.8 27/1 — 1/2/00 140 5 3.6 3.8 *Corrected to account for the effect of closed traps; Cunningham and Moors, 1996. DISCUSSION North Island has been radically changed by human activities. Repeated fire, the early introduction of rats (prior to permanent human settlement) and plantation agriculture together destroyed almost all natural vegetation and nesting seabird colonies. The endemic flora and fauna (which originally included giant tortoises) were largely eliminated by these factors with only a small number of native and endemic species surviving (some of these species, such as takamaka Calophyllum inophyllum and Ochrosia oppositifolia probably owe their present abundance or occurrence to deliberate planting). The remaining endemic flora of the island is equivalent to that of a far smaller island. Although little remains of the original vegetation of the island, the Jemo series soils of the eastern plateau suggest that this area was formerly covered with Pisonia grandis forest and supported breeding colonies of seabird (Fosberg, 1954). Lower hill slopes would probably have included species such as takamaka Calophyllum inophyllum, Mimusops sechellarum, Ficus lutea and Ficus reflexa. Native scrub on upper slopes would have included a number of shrub species no longer found on the island. At the time of the survey, the island was dominated by coconut and introduced trees and shrubs. The only areas of semi-natural vegetation were hill glacis vegetation and the plateau takamaka forests. Glacis vegetation had been heavily invaded by introduced species, and was poor in native taxa. The plateau takamaka forest was threatened by wilt disease and invasion by introduced tree species. Plateau takamaka forests probably offer the most suitable habitat on the island for Seychelles magpie-robin. Some introduced tree species support large numbers of invertebrates on their foliage (especially mealy bugs and scale insects) so they could be valuable for small insectivorous endemic birds such as the Seychelles white-eye. However, introduced plants tend to be invasive, displacing native plants and generally supporting introduced and pantropical invertebrates, rather than endemic invertebrate species. CONSERVATION RECOMMENDATIONS Despite its current condition, North Island has great potential for the conservation of endemic birds (and other taxa). Its large coastal plateau area and marsh system, if appropriately restored, would provide suitable conditions for a number of endangered endemic species including Seychelles’ rarest land bird the magpie-robin and, with 19] appropriate habitat restoration, the Seychelles black paradise flycatcher, currently restricted to La Digue and Marianne. Although, at the time of the survey described, the island was abandoned and uninhabited, it had been purchased for the development of a tourist resort and concurrent habitat restoration with the aim of introducing some endemic bird species. Development has now begun on the island. Major conservation actions that must be undertaken before such translocations can occur are outlined below: 1) Control of introduced animals Ship rats, cats and barn owls must be removed before bird introductions can take place. Cattle should be removed, or controlled, before attempting vegetation rehabilitation. 2) Rehabilitation of coconut plantation Former plantation areas on coastal plateaux should be cleared of invasive shrubs and coconut palms and succession to native-dominated forest encouraged. 3) Clearing invasive plant species Hill woodland is of lesser conservation importance. However, as it is dominated by exotic species and coconut palms, it acts as a reservoir of seed for invasion of lowland forest. Exotic species growing on the hills should be removed and replaced with native species such as Ficus spp. The most invasive species (e.g. Alstonia macrophylla) should be targeted. Clidemia hirta (at the time of the survey, restricted to a few plants on the plateau) should be destroyed before it becomes established. Some alien fruit trees have high invertebrate counts on foliage: less invasive species could be left to provide a food source for endemic insectivorous birds. 4) Control of takamaka wilt Takamaka wilt disease was already well established on North Island in 2000, and control would be difficult or impossible. However, affected trees should be removed to allow areas of forest which have been badly affected (e.g., on the east plateau) to be planted with other native species (probably Terminalia catappa). 5) Replanting To encourage rapid succession to native forest (especially where takamaka wilt has taken hold) replanting should be considered. Some species should be reintroduced including Pisonia grandis, Morinda citrifolia and Mimusops sechellarum. Beach crest vegetation (especially Scaevola sericea) should be replanted. Beach crests have been particularly badly grazed by cattle. Replanting will provide shelter for inland plantings and inhibit coastal erosion. 6) Animal reintroductions The large ground invertebrate assemblages suggest that food supply would be adequate for Seychelles magpie-robin Copsychus sechellarum. Old plateau takamaka forest would have provided an ideal foraging habitat, due to its open structure. owever, this habitat is threatened by takamaka wilt disease. Replanting of the takamaka area 192 should use Terminalia catappa or other native species which support dense populations of invertebrates. Leaf-invertebrate counts were also particularly high on North Island, including on introduced trees. Birds that feed by gleaning invertebrates from leaves, including Seychelles warbler Acrocephalus sechellensis, Seychelles white-eye Zosterops modestus and black paradise flycatcher Terpsiphone corvina could be introduced. Leaf- invertebrates were dominated by soft bugs (mainly mealy bugs) and ants but the Seychelles white-eye has been observed feeding on mealy bugs (Feare, 1975) and the warbler on ants (Bathe, 1982). These bird species would be particularly appropriate for reintroduction. The Seychelles blue pigeon Alectroenas pulcherrima was not observed on the island; North Island was the only one of the granitic islands visited where this species appeared to be absent. Although not endangered, this endemic species could be introduced if native fruit trees and shrubs were planted (for example, Canthium bibracteatum). Reptiles that should be considered for reintroduction include the Seychelles terrapins Pelusios castanoides or P. subniger, provided that sustained searches for the species demonstrate that it is absent. The North Island herd of Geochelone gigantea could be supplemented to fill the ecological role of cattle. 193 Appendix 1. Plant species recorded from North Island Taxonomy of dicotyledons as given by Friedmann (1994). Of monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>1000 individuals observed); C = Common (100 — 1000 individuals observed); F = Frequent (10 — 100 individuals observed); Occasional (3 — 10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: Se = Settlement area (on buildings); PG = Plateau grassland; PW = Plateau woodland; HW = Hill Woodland; Gl = Glacis; BC = Beach Crest; Ma = Marsh. Prior records (in notes): 1 = in Robertson, 1989; 2 = Shah and Parr, 1997. Species Status — Abund. Habitats Notes PTERIDOPHYTA Adiantaceae 1 Acrostichum aureum L. N O BC, Gl y) Pellaea ?doniana Hooker N O HW, Gl 3 Pteris tripartita Sw. 2 O PW 4 Pteris vittata L. I R Se Aspleniaceae 5 Asplenium sp. (cf. A. pellucidum Lam.) N O HW 6 Pityrogramma calomelanos (L.) Link. N e HW Davalliaceae if Davallia denticulata (Burm.) Mett. N R HW 8 Nephrolepis biserrata (Sw.) Schott N A HW, PW, Gl, [PG] Parkeriaceae 9 Ceratopteris cornuta (Pal.) Lepr. N je Ma Polypodiaceae 10 Phymatosorus scolopendria (Burm. f.) N A HW, PW Psilotaceae 11 = Psilotum nudum Sw. N F HW, PW Thelypteridaceae 12. ?Thelypteris sp. 2N R PW GYMNOSPERMAE 13. Cycas thuarsii Gaud. I R PG ANGIOSPERMAE: Dicotyledons Acanthaceae 14 = Asystasia sp. B (sensu Friedmann) at A Gl Asystasia gangetica (L.) T. Anders. ? - - Prior record ; =A 15 Justicia gendarussa Burm. f. 2] R PW Aizoaceae 16 ~— Glinus oppositifolius (L.) A. DC. 2N A Ma Amaranthaceae 17. Achyranthes aspera (L.) DC. O HW Amaranthus dubius Thell. | - 18 Alternanthera sessilis L. DC. | (o Ma 19 Amaranthus viridis L. | 194 Species Status | Abund. Habitats Notes Anacardiaceae 20 = Anacardium occidentale L. I A HW 21. = Mangifera indica L. I E PW, [HW] 22 Spondias cytherea Sonn. O PW Annonaceae Annona cherimola Mill. I - - Prior record’ 23 Annona muricata L. I A PW 24 ~=— Annona reticulata L. I E PW 25. Annona squamosa L. I O PW Apocynaceae 26 ~— Alstonia macrophylla Wall ex G. Don. I A HW 27 ~~ Catharanthus roseus (L.) G. Don. I ( PG; Gl [HW] 28 Nerium oleander L. I O PG 29. = Ochrosia oppositifolia (L.) K. Schum. N 1g PW, Gl 30 = Plumeria rubra L. I € HW il Tabernaemontana coffeoides Boj. ex A. DC. N € Gl Asclepiadaceae 32 Sarcostemma viminale (L.) Alton N F Gl Bignoniaceae 33 Tabebuia pallida (Lindl.) Miers. I A PW, HW Boraginaceae 34. = Cordia subcordata Lam. N O BC 35 Heliotropium indicum L. I A PG, PW, Ma Cactaceae 36 = ?Hylocereus undatus (Haw.) Britt. & Rose I O HW 37. Rhipsalis baccifera (J. Mill.) Stearn. N R Gl Caesalpiniaceae 38 Caesalpinia bonduc (L.) Roxb. N O PW, HW 39 ~=Delonix regia (Hook.) Raf. I O PG 40 ~~ Peltophorum pterocarpum (DC.) Hayne I O PW 4] Senna occidentalis (L.) Link I Cc PG, Ma 42 Tamarindus indica L. I F PG, PW, HW Capparidaceae 43 Cleome viscosa L. I O PG, Gl Caricaceae 44 Carica papaya L. I R PG Caryophyllaceae 45. Drymaria cordata (L.) Roem. & Schult. I O PW Casuarinaceae 46 Casuarina equisetifolia J. R. & G. Foster I A BC, HW Chrysobalanaceae 47 ~~ Chrysobalanus icaco L. I A HW, Gl Combretaceae 48 = Terminalia catappa L. 2N (G PW, HW [BC] Compositae 49 Ageratum conyzoides L. I O PG, Ma 50. Emilia sonchifolia (L.) Wight I Ei Gl, PG 5] Melanthera biflora (L.) Wild 2N R PG 52. Synedrella nodiflora (L.) Gaertn. I € PG, [Ma] 53 Tridax procumbens L. I (SC PG 195 Species Status Abund. Habitats Notes 54 Vernonia cinerea (L.) Less. I A PG Convulvulaceae 55 Ipomoea aquatica Forssk. I O Ma 56 Ipomoea mauritiana Jacq. 21 3 PG, PW, HW 57 Ipomoea pes-caprae (L.) R. Br. N Cc BC, Gl Crassulaceae 58 = Kalanchoe pinnata (Lam.) Pers. I F PG, HW Cucurbitaceae 59 = Momordica charantia L. I R PG 60 =Trichosanthes cucumerina L. I R RG: Ebenaceae 61 Diospyros philippensis (Desr.) Giirke I R HW Euphorbiaceae 62 Acalypha indica L. I F PG 63 Euphorbia hirta L. I A PG 64 Euphorbia ?hypericifolia L. 21 R PG 65 Euphorbia thymifolia L. I A PG 66 Euphorbia tirucalli L I O PG 67 ~~ Jatropha curcas L. I F PG, PW Manihot esculenta Crantz I - - Prior record’; now extinct? 68 Phyllanthus amarus Schumach. & Thonn. I F PG, PW, HW 69 ~=Phyllanthus pervilleanus (Ballon) Mill. Arg. N SC HW, Gl 70. ~=-Phyllanthus urinaria L. I F PG Goodeniaceae 71 ~~ Scaevola sericea Vahl. N F BC Guttiferae 72 ~~ Calophyllum inophyllum L. N A PW, HW [BC] Hernandiaceae 73. Hernandia nymphaeifolia (Presl) Kubitzki N O PG Labiatae Leonotis nepetifolia (L.) R. Br. I - - Prior record’; now extinct? 74 ~~ Leucas lavendulifolia J. E. Sm. I E PG, Gl 75 = Ocimum basilicum L. I R Ma Ocimum gratissimum L. I - - 76 ~~ Plectranthus amboinicus (Lour.) Spreng. 71 O HW, PG Lauraceae Cinnamomum verum Presl. I . - Prior record’; if still present, very rare 77 ~Persea americana Mill. I R PW Lecythidaceae 78 Barringtonia asiatica (L.) Kurtz N O BC Malvaceae 79 ~~ Abutilon indicum (L.) Sweet I R PG 80 Aibiscus tiliaceus L. N O HW, Gl 81 Sida acuta Burm. f. l A PG, PW 82 Sida pusilla Cav. 2N F PG, BC 83. Sida rhombifolia L. I G PG Sida stipulata Cav. l - - ; Prior record’ 196 Species Status — Abund. 84 Urena lobata L. 21 O Melastomataceae 85 Clidemia hirta (L.) D. Don. I O Meliaceae Sandoricum koetjape (Burm. f.) Merrill I - 86 Xylocarpus moluccensis (Lam.) Roem. N O Mimosaceae 87. Adenanthera pavonina L. I C 88 Albizia lebbeck (L.) Benth. F 89 Paraserianthes falcataria (L.) Niels. C Moraceae 90. Artocarpus altilis (Parkins.) Fosb. I Fs Artocarpus heterophyllus Lam. I - 9] Ficus lutea Vahl. N (€ 92 Ficus reflexa Thunb. ssp. seychellensis (Baker) _ E (ss) O Berg 93. Ficus rubra Vahl. N O Myrtaceae 94 = Eugenia uniflora L. I (O; 95 Psidium cattleianum Sabine I ¢ 96 ~~ Psidium guajava L. I A 97 Syzygium malaccense (L.) Merr. & Perry I F Nyctaginaceae 98 Boerhavia repens L. 2N € Onagraceae 99 Ludwigia erecta (L.) Hara I F 100 Ludwigia octovalvis (Jacquin) Raven 21 A Oxalidaceae 101 Averrhoa bilimbi L. I C Papilionaceae 102. Abrus precatorius L. 2N € 103. Canavalia cathartica Thouars N F 104 Crotalaria retusa L. I O 105 Desmodium incanum DC. I A 106 Desmodium triflorum (L.) DC. I A Indigofera suffruticosa Mill. I - 107 Teramnus labialis (L.) Spreng. I (C Passifloraceae 108 Passiflora foetida L. I FB 109 Passiflora suberosa L. I C Polygonaceae 110 Antigonon leptopus Hook. et Arn. I R 111 Polygonum senegalense Meisn. 2N O Portulacaceae 112. Portulaca oleracea L. 2N F Rhamnaceae 113. Colubrina asiatica (L.) Brogn. N O Rubiaceae 114 Coffea canephora Froehner I O 115. Guettarda speciosa L. N F 116 Hedyotis goreensis DC. 21 O 117 Ixora finlaysoniana G. Don. I C 118 Morinda citrifolia L. al C Habitats PW PW, Gl PW, HW PG [HW] HW, PG HW Ma Ma PG, PW PW BC Ma PW Gl, HW Notes Prior record! Prior records!” Prior record! 197] Species Status Abund. Habitats Notes Pentodon pentandrus (Schumach. & Thonn.) I - - Prior record. 119 Vangueria madagascariensis J. F. Gmel I € PW, HW Rutaceae 120 Citrus aurantifolia (Christ.) Swing. I O PG, PW 121 Citrus aurantium L. I O PG 122 Citrus limon (L.) Burm. I O PG 123. Citrus medica L. I O PG, PW Citrus paradisi Macfad. I - - Prior record’ 124 Citrus reticulata Blanco I R PG Citrus sinensis (L.) Osbeck I - Prior record’ 125. Murraya koenigii (L.) Spreng. I R PG Sapindaceae Cardiospermum halicacabum L. 2N - - Prior record’ Scrophulariaceae 126 Striga asiatica (L.) O. Kuntze Bi O PG Solanaceae 127 Datura metel L I FE PG 128 Physalis angulata L. I R PW 129 Solanum americanum Mill. I R PG 130 Solanum lycopersicum L. I R PG Sterculiaceae 131 Heritiera littoralis Ait. N O PG Tiliaceae 132 Triumphetta rhomboidea Jacq. I F Gl Turneraceae 133. Turnera angustifolia Miller I ¢€ PG, PW, HW Umbelliferae 134 Centella asiatica (L.) Urb. 21 A PG Verbenaceae 135 Lantana camara L. I A PG, Gl 136 Phyla nodiflora (L.) Greene | A Ma. PG 137 Stachytarpheta jamaicensis (L.) Vahl. it Is PG 138 Stachytarpheta urticifolia (Salisb.) Sims. I A PW, HW ANGIOSPERMAE: Monotyledons Agavaceae 139 Furcraea foetida (L.) Haw I F PW, Gl Amaryllidaceae 140 ?Crinum sp. 21 R PG 141 Zephyranthes rosea Lindl. O PG Araceae 142 Alocasia macrorrhiza (L.) G. Don. ] F PW 143. Epipremnum pinnatum (L.) Engl. Cv. Aureum I O PW Bromeliaceae 144 Ananas comosus (L.) Merr. I O Gl Commelinaceae 145 Commelina benghalensis L. 7] G Ma Commelina diffusa Burm. f. a - - Prior record Cyperaceae 146 Cyperus alopecuroides Rottb. ? O Ma 147. Cyperus articulatus L. N O Ma 148 Cyperus compressus L. ? O Gl 149 Cyperus rotundus L. ts A PG see at a 198 Species 150 Fimbristylis complanata (Retz.) Link 151 Fimbristylis cymosa R. Br. 152. Fimbristylis sp. (glacis sedge) 153 Kyllinga alba Nees 154 Kyllinga monocephala Rottb. 155 Kyllinga polyphylla Willd. Ex Kunth 156 = Mariscus dubius (Rottb.) Fischer 157. Pycreus polystachyos (Rottb.) P. Beauv. Gramineae Axonopus compressus (L.) P. Beuv. 158 Bambusa vulgaris Scrad. Ex Wendl. B. vulgaris var. aureo-variegata 159 ?Brachiaria sp. 160 Chloris barbata (L.) Sw. 161 Chrysopogon aciculatus (Retz.) Trin. 162 Dactyloctenium ctenoides (Steud.) Bosser 163 Digitaria ?didactyla Willd. Digitaria radicosa (Presl.) Miq. 164 Digitaria sp. 165 Echinochloa colonum (L.) Link 166 Eleusine indica (L.) Gaertn. 167 Eragrostis tenella (L.) P. Beuv. Eragrostis tenella var. insularis Hubb. 168 Lepturus radicans (Steud.) Camus 169 Oplismenus compositus (L.) P. Beuv. 170 Panicum brevifolium L. 171 Paspalidium geminatum (Forsk.) Stapf. 172. Paspalum conjugatum Berg 173. Paspalum scrobiculatum L. 174 Pennisetum polystachyon (L.) Schult. 175 Rhynchelytrum repens (Willd.) C. E. Hubb. Saccharum officinarum L Setaria barbata (Lam.) Kunth. 176 Sporobolus virginicus (L.) Kunth. 177. Stenotaphrum dimidiatum (L.) Brogn. Urochloa paspaloides Pres. Lemnaceae 178 Lemna sp. Liliaceae Dracaena reflexa Lam. 179 Gloriosa superba L. Marantaceae Maranta arundinacea L. Musaceae Musa sp. Najadaceae 180 Najas ?australis Bory ex Rendle Orchidaceae 181 Vanilla planifolia Andrews Palmae 182 Cocos nucifera L. Status G) HVVYVYAA A Aryvvvv—vrvAvyvvyvywewHas STAN AOS) Abund. € > Ti@ Gra nA: QOraydnanop,r O@G© Oa Sa Qi Sey ar > Habitats Gl RG Gl PW Notes Prior record! Prior record! Prior record'; now extinct? Prior record! Prior record! Prior record! Prior record! Prior records”; now extinct? 199 Species Status Abund. Habitats Notes 183 Latania lontaroides Gaertn. I F PG 184 Phoenix sp. (?P. dactylifera L.) | R PG Pandanaceae 185 Pandanus balfourii Mart. Ig |e) Gl, HW 186 Pandanus utilis I R PG Typhaceae 187 Typha javanica Schnitz. ex Zoll. N A Ma Zingiberaceae 188 ?Zingiber zerumbet I O PW legend 14 Se Contours & Vegetation plots m Marsh & Building Beach Figure 1. Thérése Island: physical, showing site of vegetation plots. Mangrove 200 metres THERESE BY MICHAEL J. HILL', TERENCE M. VEL', KATY HOLM”, K., STEVEN J. PARR? and NIRMAL J. SHAH! GEOLOGY, TOPOGRAPHY AND CLIMATE Thérese has an area of 73.9 ha. It is situated 700 m from the east coast of Mahé, the largest of the granitic Seychelles islands. At its highest point (Thérese Peak) it reaches 160 m above sea level. The island is dominated by sloping ground. There are two main hills: Therese Peak and a lower hill to the north (60 m). The south west has a raised, level area of open rock (glacis) at 50-70 m above sea level. The north east shore of the island has a sandy beach backed by a narrow coastal plain (plateau). Most of the land is sloping ground between 10 and 100 m above sea level (Table 1). Table 1. Area of Thérese by altitude (calculated from maps published by Directorate of Overseas Survey(UK)/Seychelles Government). Altitude range (m. asl. Area (ha Percentage total area >150 0.1 0.1 100 - 150 0.8 1.1 50 - 100 36.7 49.7 10 - 50 26.1 35)53 0-10 10.2 13.8 Geologically, the island is similar to the nearby west coast of Mahé. The hills are made up of porphyritic granite (Braithwaite, 1984) while the coastal plateau is made up of recent calcareous deposits mixed with weathering products of the granite and overlain (in places) with marsh deposits. The soils of Thérese are mainly red earths, strongly eroded on steeper slopes. On the open glacis areas, soils are restricted to pockets. Standing water on the island is limited. The coastal plateau has a narrow marsh (dimensions approximately 90 metres by 10 metres wide) running parallel to the coast and separated from the sea by a raised sandy berm. Water in this marsh is saline and the water level varies with tides, although the marsh is superficially not open to the sea. A small mangrove pool (see Fig. 1) is open to the sea. Behind this pool, a small fresh-water stream drains the hill and glacis, widening to form rocky freshwater pools at the base of the hill. While stream flow appeared seasonal, water was present in both September and February, and flowing or standing water is probably present here for much of the year. ' Nature Seychelles, PO Box 1310, Mahé, Seychelles. Email: birdlife@seychelles.net 2199] Casa Marcia Crescent Victoria, British Colombia, Canada. Royal Society for the Protection of Birds, The Lodge, Sandy, Bedfordshire, UK. 202 The Seychelles islands experience a seasonal humid tropical climate (Walsh, 1984). While no weather data exist for Théreése, it could be predicted that the climate of the island follows a similar pattern to that of nearby Mahé. Port Glaud, on the west coast of Mahé opposite Thérése, has lower annual rainfall than Beau Vallon to the north or Victoria to the east (Walsh, 1984). Although it is in the generally wetter northern part of Mahé, it is sheltered from the prevailing winds (in particular the north west wind of the rainy season) by hills. HISTORY In 1787, relatively soon after the first permanent human settlement of the Seychelles, Malavois recorded that landing was possible on Thérése throughout the year and that the island had fresh water all year round. Land tortoises, which had been recorded in 1776 (Bour, 1984) were absent at that time (although still present on the nearby, less accessible Conception Island) and green sea turtles did not breed there, although hawksbill turtles were reported to visit the island (in Fauvel, 1909). The relative accessibility of the island from Mahé made exploitation of the island possible, but the small plateau was not suitable for agriculture on any scale. There are no records of the earliest settlement of Thérése but coconut plantations were probably begun in the nineteenth or early twentieth century when a range of other species including cinnamon and vanilla were probably introduced. Today, the island has no permanent human population and is managed as a resort with day-trippers visiting from Mahé. There are restaurant and water sports facilities. Few distinct paths exist and most tourists stay on the beach or the small coastal plateau. FLORA AND VEGETATION Flora In total, 183 plant species were recorded on Thérése, including eight ferns and 175 angiosperms (Appendix 1). Of the angiosperms, 94 (53.7%) species are regarded as introduced (Friedmann, 1994) and 65 (37.1%) native. Of the native taxa, 17 species or subspecies are endemic to the Seychelles (9.7% of the angiosperm flora). The proportions of the total flora made up of introduced and endemic species were similar to those for the Seychelles as a whole (of the total Seychelles flora, around 54% are introduced and 9% endemic; Procter, 1984). Compared to the flora of other small islands, Thérése is relatively rich in endemic species. This high endemicity is due to the proximity of the island to Mahé, where almost all the endemic plant species of Seychelles are represented. The steep slopes of the island and presence of open glacis and scrub on soils of little agricultural value may also have contributed to the survival of a number of endemic plants here. 203 Few previous botanical surveys have been carried out on the island and Robertson (1989) lists just three species for Thérése: Erythroxylum sechellarum (as E. longifolium), Intsia bijuga, and Cocos nucifera. All were recorded in the current survey. Of the introduced plants established on Thérése, 17 are invasive weedy species. Several of the woody weeds which are most invasive on the smaller islands of Seychelles were present, including cocoplum Chrysobalanus icaco and cinnamon Cinnamomum verum (both abundant). A/stonia macrophylla was also well established in open hill woodland along with casuarina Casuarina equisetifolia and cashew Anacardium occidentale. Coconuts Cocos nucifera were common, especially on the plateau and lower hills. Albizzia Paraserianthes falcataria was represented by a few old trees on the plateau but there was strong regeneration present. One tree species which was abundant (mainly on the plateau), Trema orientalis, was regarded as an invasive introduced species by Carlstré6m (1996a) but as a native species by Friedmann (1994). At least 31 species of introduced plants (17.7% of the angiosperm flora) recorded on Thérése were restricted to the gardens around the restaurant and were not found away from cultivation. Most are recent introductions on Thérése and would probably become extinct were cultivation to cease. Vegetation The extent of major vegetation types on Thérése is shown in Table 2 and Figure 2. The vegetation of Thérése 1s varied with some habitats, such as mangrove, glacis, and native scrub, dominated by native plants. Table 2. Extent of major vegetation types, Thérése Island. Vegetation type Approx. area (ha) Hill Woodland (predominantly introduced) 10 (>10 m asl) Native palm forest 2 Coconut with regeneration 6 Scrub (native) 20 Scrub (mixed) 18 Scrub (introduced) ] Bare rock 2) Plateau Woodland (predominantly introduced) 2 (<10 m asl) Coconut plantation I Coconut with regeneration l Scrub (native) << Mangrove <] Brackish marsh <1 Beach crest vegetation l Grassland/garden 5 stems shown. Plateau No stems % stems | No stems % stems Introduced species Anacardium occidentale l 1.0 Casuarina equisetifolia 0 Cinnamomum verum 22 22.7 Tabebuia pallida 24 24.7 Native species 0 Canthium bibracteatum Cocos nucifera Dracaena reflexa Hibiscus tiliaceus Paragenipa wrightii Tabernaemontana coffeoides Terminalia catappa Total 206 Table 5. Thérese Island: most widespread shrub species. Shrubs occurring in >5 plots shown. Percentage shrub cover is the mean cover by the species for those plots in which the species occurs. No. plots % shrub cover % shrub cover No. plots Introduced species Chrysobalanus icaco Cinnamomum verum 10 14.1 Native species Calophyllum inophyllum 6 13 Canthium bibracteatum Cocos nucifera 13 12.9 Dracaena reflexa q Ihe Memecylon elaeagni Paragenipa wrightii Phoenicophorium borsigianum Premna serratifolia 6 4.6 Scaevola sericea 3) 8.8 Total Discussion: Flora and Vegetation The flora of Thérése is similar to that of nearby parts of Mahé Island. Some species present on nearby coastal areas and hills of Mahé but rare on other islands include the endemic Allophyllus sechellensis and the (probably) native Dianella ensifolia. The vegetation of plateau forest on Théreése is not distinct from that of the hill except for a narrow coastal strip of beach crest woodland including species such as Hibiscus tiliaceus and Guettarda speciosa. Takamaka Calophyllum inophyllum 1s still a constituent of this coastal strip and it is also found in hill woodland. However, most of the takamaka trees on the coastal strip show symptoms of takamaka wilt disease caused by the fungus Leptographium (Verticillium) calophylli (Ivory et al., 1996; Wainhouse ef al., 1998). Many of the trees along the beach crest are already dead although some have shown signs of foliage regrowth after extensive dieback (J. Etienne, pers. comm.). Plateau and hill forest are dominated by introduced species (especially cinnamon) but they also have a high diversity of native and endemic species including endemic palms (there is an area of endemic palm forest on the north west of the island). Native and endemic shrub species are abundant suggesting that much of the native vegetation of the island would be scrub that has been invaded by introduced trees such as cinnamon, becoming high forest in the process. 207 INVERTEBRATES Pitfall Trapping The total size of pitfall assemblages (numbers of invertebrates caught) are shown in Table 6. Only invertebrates over 2 mm body length are included (excluding minute invertebrates such as Collembola). Both hill and plateau habitats were dominated by ants (Hymenoptera; Formicidae), which made up 63.5% of all invertebrates captured. The earwigs (Dermaptera) made up 25.5% of the invertebrates caught. The remaining 11% of individuals included spiders (Araneae), insect larvae, Lepidoptera, Blattodea, Coleoptera, Crustacea, Isoptera, Mollusca, Myriapoda, Orthoptera, Psocoptera and Hymenoptera (excluding ants). The most abundant invertebrate species was the ant Odontomachus troglodytes, which formed 47.5% of individuals overall. An unidentified earwig species made up 14.9% of total invertebrates and was the second most abundant taxon. Invertebrate counts excluding ants were higher in the north west monsoon and higher on the plateau than the hill. Lowest invertebrate counts came from hill woodland in the dry south east season. A single individual of the introduced crazy ant Anoplolepis gracilipes was collected in one pitfall trap on the plateau. This species is widespread on Mahé, where it is regarded as a nuisance (Haines et a/., 1994) and on Bird Island it has negative effects on the island’s ecosystems and conservation status (Feare, 1999a; Hill, in prep.). Since only one individual was caught it is probable that the species is not established on Thérése. Table 6. Pitfall assemblages from Thérese. Only invertebrates of body length >2 mm included. (number in parentheses = number of invertebrates excluding ants). Mean no. individuals per five traps SE season NW season Thérése Plateau woodland 49.7 (12.0) 44.9 (19.0) Hill woodland 13.2 (6.2) 24.9 (9.4) Mean for all granitic 61.8 (9.4) 61.1 (16.0) islands Leaf-insect Counts Leaf-insect counts were carried out for 20 tree and shrub species, 11 of these in both seasons (Table 7). The large number of tree species counted reflected the island’s high tree species richness. The highest density of invertebrates (in terms of individuals per square metre of leaf) was on the native coastal shrub Scaevola sericea (plants showed high levels of infestation by aphids at the time of counting in September). Scaevola is abundant at the beach crest and in some areas of low hill scrub. Morinda citrifolia, a species of doubtful status (possibly introduced in Seychelles; Friedmann, 1994) which is 208 uncommon on Thérese, also showed high invertebrate densities. The endemic species Erythroxylum sechellarum had the highest invertebrate density in February. Ten of the 11 species counted in both seasons showed highest density of invertebrates in September rather than February. This runs counter to the trend on most islands where leaf counts are significantly greater in the wetter north west monsoon, and may reflect weather conditions specific to Thérése for the 1999/2000 season. Although the trees showing highest densities of invertebrates in both seasons were native, some introduced species also showed relatively high invertebrate densities, especially Cinnamomum and Tabebuia. Table 7. Density of invertebrates on foliage, Thérése. n=no. of leaves counted; NI = number of individual invertebrates. NW season (Februa Species Mean NI Mean NI n mean NI mean NI Leaf! m? leaf m? Introduced species Alstonia macrophylla 50 0.36 3255 0 Anacardium occidentale 149 0.34 33.04 100 0.13 [3351 Chrysobalanus icaco 100 0.14 42.81 50 0.08 25.16 Cinnamomum verum 900 0.48 76.78 1850 0.20 29.78 Psidium cattleianum 50 0 0 0 Tabebuia pallida 50 0.26 87.84 0 Native species Calophyllum inophyllum 250 0.26 24.39 200 0.18 19.65 Canthium bibracteatum 340 0.08 48.73 300 0.01 6.94 Erythroxylum sechellarum 0 50 1.28 335.08 Ficus lutea 50 0.16 22.54 0 Guettarda speciosa 0 50 0.32 11.54 Hibiscus tiliaceus 50 0.16 IBIS 9 0 Memecylon elaeagni 250 0.05 71.64 500 0.05 63.01 Paragenipa wrightii 200 0.62 90.64 500 0.12 14.20 Premna serratifolia 250 0.27 31563 200 0.06 9.46 Scaevola sericea 100 14.02 649.68 200 0.08 4.58 Tabernaemontana 100 0.18 41.47 0 coffeoides Terminalia catappa 50 0.46 28.29 50 0.92 45.59 Trema orientalis 100 0.41 61.90 200 0.09 19.50 Status unknown Morinda citrifolia 50 5.14 285.87 Malaise Trapping Malaise trapping was carried out in plateau and hill woodland habitats, in both seasons. Main results are summarised in Table 8. As for the leaf counts, invertebrate 209 assemblages were greater in September than in February. Assemblages were larger in plateau locations than in hill plots. The most abundant taxonomic groups were Diptera, Lepidoptera, Hymenoptera and Collembola. Other Invertebrate groups represented included arachnids (spiders and mites), Blattodea, Coleoptera, Dermaptera, Embioptera, Orthoptera, Hemiptera, Psocoptera and Thysanoptera. Table 8. Malaise trap assemblages, Thérese. NI = number of Individuals. SE (September) Hill Plateau No. traps Z 2 Mean NI trap” 1180.0 3534.5 112.0 635.5 Total NI Diptera 891 6156 98 510 Total NI Hymenoptera 87 196 42 22 Total NI Lepidoptera 107 389 53) 489 Total NI Collembola 32 137 4 3] Total NI (others) 63 191 27 149 Observation A number of invertebrates were identified from observation and/or collection (Table 9). Among the endemic species recorded was the snail Stylodonta unidentata (also on Conception). Invertebrate collection took place in and around the aquatic habitats on the island in both September and February. The large brackish marsh on the plateau had few aquatic species. The vegetation was dominated by the mangrove fern Acrostichum aureum and a filamentous alga. Adults of two dragonfly species were observed around this marsh, as well as the crab Cardisoma carnifex. The most abundant invertebrate was the water snail Melanoides tuberculata. Other invertebrates collected (in September) include aquatic mites. Pools in the fresh-water stream (which had no aquatic macrophytes) had abundant invertebrate life in February, including water skaters (Hemiptera; Gerridae), water beetles, chironomid larvae (Diptera; Chironomidae) and a freshwater crab (?Sesarma impressum). Discussion: Invertebrates Invertebrate assemblages in pitfall trap assemblages were relatively large but the plateau of Thérése, the richest area for ground invertebrates, is small. Invertebrates on vegetation and in flight-intercept (Malaise) traps were more abundant in September than in February, contrary to expectations. The fact that both methods showed this decline suggests that it was a real effect, perhaps caused by local environmental conditions (especially weather conditions) in 1999/2000. 210 Although few endemic species were collected in the current survey, Thérése probably supports a large endemic invertebrate fauna in addition to the introduced or cosmopolitan species found on most islands of the Seychelles. The island is close to Mahé, which has a large endemic fauna, and supports a range of endemic plants including native palms (which provide important microhabitats for endemic invertebrate species in leaf axils). Table 9. Invertebrates observed, Therese Island. Order Family Species Notes Mollusca Acavidae Stylodonta unidentata (Chemnitz, 1795) Occasional shells in hill woodland Achatinidae Achatina fulica (Bowditch, 1822) Abundant Thiaridae Melanoides tuberculata (Miller, 1774) In saline marsh Arachnida: Araneae Tetragnathidae = Nephila inaurita (Walckenaer, 1841) Crustacea: Decapoda Coenobitidae Coenobita brevimanus Dana, 1852 Gecarcinidae Cardisoma carnifex (Herbst, 1784) In saline marsh and mangrove Grapsidae Neosarmatium ?meinerti (De Man, 1887) In mangrove Sesarma impressum H. Milne Edwards, In freshwater stream 1837 Ocypodidae Ocypode ceratophthalmus (Pallas, 1772) On beach Myriapoda: Chilopoda Scolopendridae Scolopendra subspinipes (Leach, 1918) Diplopoda Trigoniulidae Spiromanes ?braueri (Attems, 1900) Insecta: Coleoptera Scarabaeidae Perissosoma aenescens Waterhouse, 1875 Lampyridae Luciola laeta Gerstaecker, 1871 Rare, in hill woodland Hymenoptera Anthophoridae Aylocopa caffra (Linnaeus, 1767) Apidae Apis mellifera adansoni Latreille, 1804 Formicidae Anoplolepis gracilipes (Smith, 1857) In pitfall traps Camponotus hova Forel, 1891 In pitfall traps ?Camponotus thomasetti Forel, 1912 In pitfall traps Cardiocondyla emeryi Forel, 1881 In pitfall traps Odontomachus troglodytes Santschi, 1914 In pitfall traps Paratrechina sp. In pitfall traps Plagiolepis ?alluaudi Emery, 1894 In pitfall traps ?Plagiolepis exigua Forel, 1894 In pitfall traps Technomyrmex albipes (Smith, 1861) In pitfall traps Vespidae Polistes olivaceus (de Geer, 1773) Lepidoptera Lycaenidae Leptotes pirithous Linnaeus, 1767 Zizeeria knysna (Trimen, 1862) Hesperiidae Borbo ?gemella Mabille, 1884 Nymphalidae Melanitis leda africana (Linnaeus, 1758) Odonata Agrionidae Ceriagrion glabrum (Burmeister, 1839) Coenagrionidae Agriocnemis pygmaea (Rambur, 1842) Libellulidae Diplacodes trivialis (Rambur, 1842) Tramea limbata Selys, 1878 Subulinidae Subulina octona Bruguiere, 1792 Orthetrum stemmale wrightii (Selys, 1877) Pantala flavescens (Fabricius, 1798) 211 VERTEBRATES Reptiles and Amphibians Reptiles and amphibians observed during the course of fieldwork were recorded and a list of species identified is given in Table 10. The list includes three lizards, one tortoise and one frog. At least two of these species are introduced on Thérése, the Pacific house gecko and the Aldabra giant tortoise, the latter represented by a small group of individuals kept in a pen. One species previously recorded from the island was not seen: the bronze-eyed gecko Ailuronyx seychellensis (Cheke, 1984). This species 1s cryptic and nocturnal and is only common on rat-free islands (Cheke, 1984); it may have been overlooked. None of the three snakes known from Seychelles (Nussbaum, 1984a) were recorded, although these are rarely seen and may occur on the island. Given the proximity of Thérése to Mahé, it is possible that one of the Seychelles’ endemic caecilians survives on the smaller island (the most likely species 1s Hypogeophis rostratus: Nussbaum, 1984b). Table 10. Reptiles and amphibians, Therese Island. Status: E =endemic, I = introduced, N = native (in central Seychelles). Family Species Status Amphibians Rantidae Ptychadaena mascareniensis (Dumeril & Bibron, 1836) — Mascarene frog 21 Reptiles Gekkonidae Gehyra mutilata (Wiegmann, 1835) Pacific house gecko I Phelsuma spp. day gecko E Scincidae Mabuya sechellensis (Dumeril & Bibron, 1836) Seychelles skink E Testudinidae Geochelone gigantea (Schweigger, 1812) Aldabra giant tortoise I Birds In total, 10 land birds and waders were recorded (Table 11). Three of these were Seychelles endemics but two of these endemic species (Seychelles blue pigeon and Seychelles sunbird) are currentiy widespread and common within the granitic islands. One (the Seychelles kestrel Falco araea) is endangered. In addition to sight records, tape playback was used to give data on presence or absence of two species. In September 1999, calls of Seychelles scops owl Otus insularis were played and in February 2000, calls of the scops owl and barn owl Tyo alba were played. There were no positive responses. There was no evidence of seabirds breeding on Theérése island, although it is possible that some pairs of fairy tern Gygis alba nest there. However, in the September study period a number of seabird species were observed off the island, between Therese and Mahé. These birds included feeding flocks of fairy tern and noddies (Anous sp.), and occasional highflying frigatebirds (Fregata sp.). On some evenings, large numbers of shearwaters were observed flying over this stretch of water to the North: most of these HNP birds appeared to be wedge-tailed shearwaters (Puffinus pacificus) but Audubon’s shearwater (Puffinus [herminieri) were also present. Seabirds were also observed (although less frequently) in February: one tern (probably common tern Sterna hirundo) was resident on the island. Fairy terns were occasionally seen and one white-tailed tropicbird (Phaeton lepturus) was seen flying over the island. Table 11. Land birds and waders observed on Thérése. M = migrant; E = Seychelles endemic species. Species Notes Butorides striatus green-backed heron August: at least two individuals in mangrove and neighbouring beach Falco araea E Seychelles kestrel August: at least one pair, around tall Paraserianthes tree. February: one individual, flying over glacis Numenius phaeopus M whimbrel August and February: one seen regularly on beach Arenaria interpres M ruddy turnstone August and February: on beaches and glacis. Group of 8 individuals seen on glacis 10/9/99 Streptopelia picturata Madagascar turtle dove Regularly seen on plateau around settlement. picturata Geopelia striata barred ground dove A few birds regularly seen on plateau. Alectroenas pulcherrima E Seychelles blue pigeon Frequently seen in woodland and scrub habitats. Nectarinia dussumieri E Seychelles sunbird Regularly seen in mangrove and woodland. Acridotheres tristis common mynah Regularly seen on beach, around buildings, around glacis and in woodland/scrub. Foudia madagascariensis Madagascar fody Commonly seen. Mammals Mammals observed in the course of fieldwork were recorded (Table 12). In addition, rodent trapping was carried out in September 1999, and February 2000 (Table 13). Two traplines were established, one in plateau woodland (grid ref. CK 2285 8375 — CK 2250 8390) and one in hill woodland/scrub (dominated by cinnamon Cinnamomun verum at lower altitudes with mixed scrub at higher altitudes) (grid ref. CK 2250 8390 — CK 2232 8400). Only one species of rodent, the ship rat Rattus rattus, was trapped. Trapping rates were low in September, perhaps in part due to interference with traps by resident dogs. Rates were higher in September although in general rates were lower in the north west Monsoon and higher in the south east period when food and water stress were greater and rats more likely to be trapped. The island had the largest number of mammalian predators of any of those studied. Table 12. Mammals, Thérese Island. 4-6 individuals several individuals observed, also tracks and scat on beaches and glacis observed once: possibly juvenile black rat common in February; rarely seen in September fresh bones collected Abundant Canis familiaris L. Felis catus L. ?Mus domesticus Rutty Pteropus seychellensis Milne Edwards Tenrec ecaudatus Schreber Rattus rattus L. Table 13. Results of rat trapping, Thérese Island. Trap-nights No. of rats Rats per 100 trap- Rats per 100 trap- Dates nights nights (uncorrected) (corrected)* 9 — 14/9/99 139 20 14.39 17.47 10 — 15/2/00 140 515) 39.29 63.22 Total (SE) 35.34 Total (NW) 25.56 *corrected to account for the effect of closed traps: Cunningham and Moors, 1996 CONSERVATION RECOMMENDATIONS Théreése is a relatively small island which has conservation interest principally because of its proximity to the islands of Mahé and Conception. Its proximity to Mahé (and its hilly terrain) has allowed the development of a flora (and probably invertebrate fauna) rich in endemic species. Nearby Conception has a population of the Seychelles white-eye Zosterops modestus, an endangered endemic bird. The white-eye has never been recorded on Thérése, probably due to the early introduction of ship rats which are a likely nest predator (on Conception only the Norway rat Rattus norvegicus is present). The introduction of white-eyes to Thérese would require the eradication of rats and cats, which are also present. The presence of introduced predators would appear to be the chief barrier to the survival of white-eyes on the island. White-eyes feed mainly on gleaned invertebrates although they also take small fruit. The species survives on an island dominated by introduced cinnamon (Conception) so it is not dependent upon native vegetation. The high leaf invertebrate counts on Thérése suggest food supply would not be limiting for a translocated population although planting of Morinda citrifolia and other native shrubs would increase the available food supply. White-eyes are currently found on only two islands and translocation to establish new populations is an urgent priority. Calophyllum inophyllum on Thérése 1s threatened by the takamaka wilt disease Leptographium calophylli, which is probably spread by a native bark beetle (Wainhouse et al., 1998). The disease has caused dieback and death of most coastal trees on the island, although some have shown signs of recovery. To prevent enhanced erosion of the coastal plateau, planting of other native coastal trees should be carried out at the beach crest. Most trees in hill forest showed no signs of the disease but on Mahe, trees at high altitudes also suffer from the disease (personal observation). Removal of dead and dying wood may reduce the rate of spread on Thérése but is unlikely to eradicate the disease due to the ease of reinvasion from Mahé where the disease is very well established. 214 Appendix 1. Plant species recorded from Thérése Taxonomy of dicotyledons as given by Friedmann (1994). Of monocotyledons, as in Robertson (1989). Families arranged in alphabetical order. Species observe only in cultivation around the buildings are listed separately, below. Status: E = Endemic; N = Native; I = Introduced. Abundance: A = Abundant (>1000 individuals observed); C = Common (100 - 1000 individuals observed); F = Frequent (10 - 100 individuals observed); Occasional (3 - 10 individuals observed); R = Rare (1 or 2 individuals observed). Habitats: PG = Plateau grassland; PW = Plateau woodland; HW = Hill Woodland; HSc = Hill Scrub; Gl = Glacis; BC = Beach Crest; Ma = Marsh; Mg = Mangrove; Cu = Cultivated area; Cu* = species only recorded in cultivation. Species Status Abund. Habitats PTERIDOPHYTA Adiantaceae ] Acrostichum aureum L. N A Ma Davalliaceae 2 Davallia denticulata (Burm.) Mett. N A HW, PW, Gl 3 Nephrolepis biserrata (Sw.) Schott N A HW, PW, Gl Gleicheniaceae 4 Dicranopteris linearis Burm. ? A HSc Polypodiaceae 5 Phymatosorus scolopendria (Burm. f.) N A HW, PW Psilotaceae 6 Psilotum nudum Sw. N O HW Selaginellaceae i Selaginella sp. N O HW, PW Vittariaceae 8 ?Vittaria sp. N O G] ANGIOSPERMAE: Dicotyledons Acanthaceae Y) Asystasia sp. B (sensu Friedmann) 21 A PG, HW Amaranthaceae 10 Celosia argentea L. I O Cu* Anacardiaceae 11. = Anacardium occidentale L. I A HW 12. Mangifera indica L. I ig PW, HW 13. Spondias cytherea Sonn. I O PG Apocynaceae 14. = Allamanda cathartica L. I R Cus 1S. Alstonia macrophylla Wall ex G. Don. I C HW, Gl 16 Catharanthus roseus (L.) G. Don. I Fi Gl, Cu 17. -Nerium oleander L. I O Gus 18 Plumeria rubra L. I R Cus 19 Tabernaemontana coffeoides Boj. ex. A. DC. N A HW 20 Tabernaemontana divaricata (L.) Roem. & Schult. I R Cuz Araliaceae Dl Polyscias spp. I Cu* ve) Species Status Abund. Habitats Asclepiadaceae 22 Sarcostemma viminale (L.) Alton Avicenniaceae 23. ~~ Avicennia marina (Forssk.) Vierh. Bignoniaceae 24. ~—- Tabebuia pallida (Lindl.) Miers. Boraginaceae 25. Cordia subcordata Lam. 26 = Tournefourtia argentea L. f Caesalpiniaceae 27 ~~ Caesalpinia pulcherimma (L.) Swartz 28 = Intsia bijuga (Colebr.) O. Kuntze 29 ‘Senna alata (L.) Roxb. 30 ~=Tamarindus indica L. Campanulaceae 31 Hippobroma longiflora (L.) G. Don Caricaceae 32. ~= Carica papaya L. Casuarinaceae 33. = Casuarina equisetifolia J. R. & G. Foster Chrysobalanaceae 34. = Chrysobalanus icaco L. Combretaceae 35. Lumnitzera racemosa Willd. 36 = Terminalia catappa L. Compositae 37. ~—- Emilia sonchifolia (L.) Wight 38 Vernonia cinerea (L.) Less. Convulvulaceae 39 = Ipomoea macrantha Roem. & Schultes 40 = Ipomoea obscura (L.) Ker Gawl. 41 —_ Ipomoea pes-caprae (L.) R. Br. 42 Ipomoea venosa (Desr.) Roem. & Schultes Crassulaceae 43. Kalanchoe pinnata (Lam.) Pers. Ebenaceae 44 — Diospyros seychellarum (Hiern.) Kosterm. Erythroxylaceae 45 Erythroxylum sechellarum O. E. Schulz Euphorbiaceae 46 Acalypha wilkesiana Mill. Arg. 47 Codiaeum variegatum L. 48 = Euphorbia hirta L. 49 Euphorbia ?hypericifolia L. 50 Euphorbia pyrifolia Lam. 51 ~~ Jatropha pandurifolia L. 52. Phyllanthus acidus (L.) Skeels 53. Phyllanthus pervilleanus (Baillon) Mull. Arg. 54 ~~ Phyllanthus urinaria L. Flacourtiaceae 55 Flacourtia jangomas (Lour.) Rauschel. Goodeniaceae 56 Scaevola sericea Vahl. N F Gl, HW N F Mg I (C PW N F BC N O BC I O Cuz N F HW, HSc I R Cuz I R PG I F PG I F Cu, PW I A HW, Gl I A HW, HSc, Gl N Ie Mg 2N Cc BC, PW O PG, Cu A PG, Cu N F PW I F PG N A BC, Gl N F Gl I F Gl E E HSce E F HW, HSc, PW I F Gu* ] (C Cu* | (e Cu, PG l R Cu N Cc Gl i O Cu* I R PG N F PG, HW l O Cu, PG ] R PG N (3 BC DNS 216 Species Status Abund. Habitats Guttiferae 57 ~~ Calophyllum inophyllum L. N C BC [PW, HW] Hernandiaceae 58 Hernandia nymphaeifolia (Pres) Kubitzki N O BE Labiatae 59 Plectranthus amboinicus (Lour.) Spreng. vl O Gl Lauraceae 60 Cinnamomum verum Presl. I A PW, HW 61 Persea americana Mill. I R PG Lecythidaceae 62 Barringtonia asiatica (L.) Kurtz N O BC Malvaceae 63 Hibiscus rosa-sinensis L. I O Cus 64 Hibiscus tiliaceus L. N F BC, PW 65 = Sida stipulata Cav. I R PG 66 Thespesia populnea (L.) Soland. ex Correa N Ig BC/Mg Melastomataceae 67 Melastoma malabathricum L. 21 O Gl 68 Memecylon elaeagni Blume IE A HSc, HW Meliaceae 69 Xylocarpus moluccensis (Lam.) Roem. N O Mg Mimosaceae 70. Adenanthera pavonina L. I (Cc HW 71 Albizzia lebbeck (L.) Benth. R HW 72 ~~ ~Paraserianthes falcataria (L.) Niels. F PW Moraceae 13 Ficus lutea Vahl. N (C HW, PW 74 ~~ Ficus reflexa Thunb. ssp. seychellensis (Baker) Berg E (ss) FE HW 75. Ficus rubra Vahl. N O Gl Myrtaceae 76 ~=Eucalyptus sp. (?E. camaldulensis Dehn.) I R HW 77 ~~ ‘Eugenia uniflora L. I O PG 78 Psidium cattleianum Sabine I F Cu, PW, HW 79 ~~ ~Psidium guajava L. I O Cu, PW 80 Syzygium malaccense (L.) Merr. & Perry I R PG 81 Syzygium wrightii (Baker) A. J. Scott IE Je HW, HSc Nyctaginaceae 82 Mirabilis jalapa L. I R Cus Oxalidaceae 83. = Averrhoa bilimbi L. I F Cu, HW Papilionaceae 84 Abrus precatorius L. 2N A PG, PW, HW 85 Alysicarpus vaginalis (L.) DC. I O PG 86 Canavalia cathartica Thouars. N C BC, PG 87 Desmodium incanum DC. I A BC, PG 88 Desmodium triflorum (L.) DC. if © BC, PG 89 Indigofera suffruticosa Mill. I F PG 90 Pterocarpus indica Willd. I O HW, PW 91 Sophora tomentosa L. N Is BC 92 Teramnus labialis (L.) Spreng. I O PW, HW 93 Vigna marina (Burm.) Merr. N O BC Passifloraceae 94 Passiflora edulis Sims F Cu, PW 95 Passiflora foetida L. I (c PW, HW 27), Species Status Abund. Habitats 96 —— Passiflora suberosa L. I A PG, PW, HSc, HW Portulacaceae 97 Portulaca grandiflora L. I € Cut Rhamnaceae 98 Colubrina asiatica (L.) Brogn. N F BC, PW Rubiaceae 99 ~~ Canthium bibractatum (Baker) Hiem. N A HW, HSc, PW 100 Guettarda speciosa L. N O BC 101. Mitracarpus hirtus (L.) DC. I A PG, HW 102. Morinda citrifolia L. 7 (© PG, HW, Gl 103. Paragenipa wrightii (Baker) F. Friedmann E A HW, HSc, Gl 104 Pentodon pentandrus (Schumach. & Thonn.) Vatke I O Cu Rutaceae 105 Citrus spp. R Cu, PG 106 Murraya koenigii (L.) Spreng. R Cut Sapindaceae 107. Allophyllus sechellensis Summeth. E EF PW, HW, HSc 108 Dodonea viscosa Jacq. N O HSc Sapotaceae 109 Mimusops sechellarum (Oliv.) Hemsl. 19, O HW Scrophulariaceae 110 Russellia equisetiformis Cham. & Schlect. I Cc Gus 111 Striga asiatica (L.) O. Kuntze 2] Ie PG Sterculiaceae 112 Heritiera littoralis Ait. N R PW Turneraceae 113. Turnera angustifolia Miller I A PG, HSc, HW Ulmaceae 114 Trema orientalis (L.) BI. N F PW, HW Verbenaceae 115 Clerodendron speciosissimum Morren I O PW 116 Lantana camara L. I O HSc, 117. Premna serratifolia L. N A HW, HSc, PW 118 Stachytarpheta jamaicensis (L.) Vahl. I A HW, PG 119 Stachytarpheta urticifolia (Salisb.) Sims. ] F PG ANGIOSPERMAE: Monotyledons Agavaceae 120 Furcraea foetida (L.) Haw. ] RK G] Amaryllidaceae 121 Hymenocallis littoralis (Jacq.) Salisb. II EK BC 122 Zephyranthes candida Herb. I B Cu* Araceae 123. Alocasia macrorrhiza (L.) G. Don. I O Cu* 124 Anthurium sp. I O Cu* 125 Caladium bicolor (Dryand.) Vent. I O Cu* 126 Dieffenbachia sequine (Jacq.) Schott I R Cu* Bromeliaceae 127. Ananas comosus (L.) Merr. I F Cu, Gl Commelinaceae 128 Tradescantia spathacea Swartz I F Cu* Cyperaceae 129 Cyperus sp. ? F HW 130 Cyperus sp. 2 ? iG ai __Mg : 218 Species Status Abund. 131 Fimbristylis cymosa R. Br. ? A 132 Fimbristylis ?dichotoma (L.) Vahl. zy F 133 Fimbristylis sp. (glacis sedge) ? C 134 = Kyllinga alba Nees ”, C 135 Kyllinga polyphylla Willd. ex Kunth N A 136 Lophoschoenus hornei (C. B. Cl.) Stapf. E € 137. Mariscus dubius (Rottb.) Fischer N A 138 ?Mariscus pennatus (Lam.) Domin. N R 139 Pycreus polystachyos (Rottb.) P. Beauv. g € Gramineae 140 Bambusa vulgaris Schrad. ex Wendl. var. aureo-variegata I R 141 Brachiara umbellata (Trin.) W. D. Clayton N A 142 Cymbopogon sp. I O 143. Dactyloctenium ctenoides (Steud.) Bosser ? B 144 Digitaria ?horizontalis Willd. z € 145 Digitaria ?radicosa (Presl.) Miq. 2N F 146 Eragrostis tenella var. insularis Hubb. ¥ F 147 ?ischaemum heterotrichum Hack. y FF 148 Oplismenus compositus (L.) P. Beuv. N A 149 Panicum brevifolium L. N A 150 =Panicum maximum L. ? € 151 Paspalum conjugatum Berg. N (C 152 Pennisetum polystachyon (L.) Schult. a ¢€ 153. Rhynchelytrum repens (Willd.) C. E. Hubb. ? Ki 154 Sacciolepis curvata (L.) Chase 2 € 155 Sporobolus diander (Retz.) P. Beuv. ? O 156 Sporobolus virginicus (L.) Kunth. N F 157. Stenotaphrum dimidiatum (L.) Brogn. N A Hypoxidaceae 158 Curculigo sechellensis Bo). E O Liliaceae 159 Cordyline fruticosa L. (A. Chev.) I O 160 Dianella ensifolia (L.) DC. N A 161 Dracaena reflexa Lam. var. angustifolia Baker N A 162 Gloriosa superba L. I O 163 Ophiopogon ?intermedius D. Don I R 164 Pleomele sp. I R Marantaceae 165. Maranta arundinacea L. I O Musaceae 166 Heliconia psittacorum L. I O 167 Musa sp. I i Orchidaceae 168 Angraecum eburneum Bory subsp. brongniartianum E (ss) R (Thours.) H. Perrier 169 Cynorkis ?fastigiata Thouars N O 170 Disperis tripetaloides (Thouars) Lindl. N R 171 Spathoglottis plicata Blume I O {72 Vanilla phalaenopsis Reichb. f. B O 173. Vanilla planifolia Andrews — I C Palmae 174 Cocos nucifera L. N A 175 Deckenia nobilis Wendl. I3, C Habitats PG Cu* BC, PG, PW Gl Cu* HW HW, Gl Cu* Cu* Cu* Cu* Cu* Cu, PG PW HSc, HW HW Cu* Gl HW PG, BC, PW, HW HW Species Status Abund. Habitats 176 = Latania ?lontaroides Gaertn. 177 Nephrosperma vanhoutteanum (Wendl. ex van Houtt.) Balf. 178 Phoenicophorium borsigianum (K. Koch) Stuntz 179 Raphia farinifera (Gaertn.) Hylander Pandanaceae 180 Pandanus balfourii Mart. 181 Pandanus multispicatus Balf. f. Taccaceae 182 Tacca leontopetaloides (L.) O. Kuntze Zingiberaceae 183 Alpinia purpurata (Vieill.) Schumann 219 I R PG E € HW, Gl E (C HW I R HSc E € Gl, HW E O Gl I C PG I R (Ci? =F : a | _ eeeE Wetton ip are Vvrhaeh worth dagen insists ‘ {- Aoi a mate apreoi a ae aie al SPIDERS (ARACHNIDA, ARANEAE) COLLECTED BY BIRDLIFE GEF ISLAND ASSESSMENT PROJECT 1999-2000 l\C MICHAEL I. SAARISTO! and MICHAEL J. HILL? ABSTRACT During the BirdLife GEF Island Assessment project 1999-2000 a total of 2,725 spider specimens were collected. Of these, 887 were adult specimens and 1,838 juveniles. The great majority of specimens (98%) could be determined down to species level. In all, the collection included 68 species belonging to 23 families. Five species new to science were collected. METHODS Spiders were collected by a variety of methods, including pitfall trapping, sweeping and beating, and were occasionally taken in Malaise traps (see Hill, this volume, for more details), on the ten islands described in the above reports, and also on Aride (pitfall trapping only) in 2000. Specimens collected were sorted and stored in 70% ethanol for later identification. RESULTS Overall, a total of 2,725 specimens were sorted for identification. Of these, 887 were adult and 1,838 juvenile; 98% of specimens could be determined to species. Sixty- eight species were represented in the collection, belonging to 23 families; at present, a total of 191 spider species (in 39 families) are known on the granitic Seychelles, with further species from the coralline islands (the latter mainly from families Araneidae, Oonopidae, Tetragnathidae and Theridiidae; Roberts 1983, Saaristo 2001b). A summary table showing representation of different spider families in this material is shown below (Table 1). Five previously undescribed taxa were identified, and these will be described at a later date. A checklist of taxa recovered, with their distribution outside the Seychelles, and known distribution within Seychelles, is given below. ' Zoological Museum, Centre for Biodiversity, University of Turku, FIN-20014 Turku, Finland. Email micsaa(@utu.fi * Nature Seychelles, PO Box 1310, Mahé, Seychelles. Email: birdlife@seychelles.net Table 1. Summary of spider specimens collected. Family No. of species This material Seychelles 01 Araneidae 6 17 Ww 02 Clubionidae 03 Corinnidae 04 Cryptothelidae 05 Gnaphosidae 06 Linyphiidae 07 Liocranidae 08 Lycosidae 09 Miturgidae 10 Ochyroceratidae 1] Oonopidae 12 Oxyopidae 13 Pholcidae 14 Salticidae 15 Scytodidae 16 Selenopidae 17 Sparassidae 18 Symphytognatidae Ww — Coy NOS KH NRK NRK KF ONK ANN NK HRN KN WV 19 Tetragnathidae 1 20 Theridiidae 1 2 21 Theridiosomatidae 22 Thomisidae 23 Uloboridae i) OIN NY WHR NNANYNRFDNONNDYK NK FN W TOTAL 6 — lon CHECKLIST Abbreviations of island names (islands in bold were visited in the course of this project, islands with asterisk are coralline): Aldabra* Ald Frégate FR Anonyme AO Grande Soeur’ GS Aride AR La Digue LD Assumption* Asn Long Island LO Astove* Ast Mahé MH Bird BI Marianne MA Cerfs Cr North NO Coetivy* Coe Petite Soeur PS Conception CC Poivre* Pov Cousin CS Praslin PR Cousine CE Providence* Prd Curieuse CR St Pierre SP Denis DE St Joseph* SU Desroches* Dsr Silhouette SI Farquhar* Faq Thérése TE Félicité FE Ile aux Vaches VA DI— Global distribution according to Platnick (2000) OR = Old records from Seychelles BeSe— New records (this collection) (f) = female specimens, (j) = juvenile specimens, (m) = male specimens. DipEe SUBORDER ARANEOMORPHA (true spiders) 01 Family ARANEIDAE Simon, 1895 - orbweb weavers Cyrtophora Simon, 1864 C. citricola (Forskol, 1775) DI: = Old World OR: Ald, AR, CF, CR, LD, PR, SI (Simon 1898; Hirst 1911; Saaristo1978; Grasshoff 1980; Roberts 1983; Gerlach et al.1997; Bowler et al. 1999; Saaristo 1999) BLS: CC, FE, MA, NO Larinia Simon, 1874 L. bifida Tullgren, 1910 DI: Central, Eastern and Southern Africa OR: AR, CE, MH, SI (Grasshoff 1980; Gerlach et al. 1997; Bowler et al.1999; Saaristo 1999) BLS: BI, CC, CS, DE, FE, MA Neoscona Simon, 1864 N. morelii (Vinson, 1863) DI: Cuba to Argentina, Africa to Seychelles OR: SP (Grasshoff 1980) BLS: BI Nesubjusca(Cala Koch.1837)) DI: = Old World OR: CR, MH, PR, SI (Grasshoff 1980; Saaristo 1999) BE: eS Prasonica Simon, 1895 P.seriata (Simon, 1895) DI: — Africa, Madagascar OR: MH, PR, SI (Grasshoff 1980; Saaristo 1999) BLS: CC, CR, DE, FE, MA, NO Thelacantha Hasselt, 1882 T. brevispina (Doleschall, 1875) DI: | Madagascar, India to Philippines, Australia OR: MH (Saaristo 1999) BES? aCe 02 Family CLUBIONIDAE Wagner, 1887 - sac spiders Clubiona Latreille, 1804 Canes: DI: —Endemic(?) OR: CE, SI (Saaristo 1999, as Clubiona sp. ign.) BES: BIy@C@; CS; DE; FE, MANO "Clubiona" “C.""nigrimaculosa Blackwall, 1877 DI: Endemic OR: AO, AR, CS, MH, SI (Simon 1893; Hirst 1911; Saaristo 1995) BESYaes 224 03 Family CORINNIDAE Karsch, 1880 - dark sac spiders Oedignatha Thorell, 1881 O. mogamoga Marples, 1955 DI: — Malaysia, Seychelles, Borneo, Samoa OR: AR, CE, PR, MH, SI (Saaristo 1978; Bowler et al. 1999; Saaristo 1999, all as O. scrobiculata). BES> Ak; BIL Cs; CRI DESMA NO aie Corinna C. L. Koch, 1842 C. gulosa (Thorell, 1878) DI: | Myanmar OR: CE, SI (Saaristo 1999, as Corinnidae Genus ign. 2., sp. ign.) IBIS NR, CS 04 Family CRYPTOTHELIDAE L. Koch, 1872 - litter spiders Cryptothele L. Koch, 1872 C. alluaudi Simon, 1893 DI: Endemic OR: CE, FR, LD, MH, PR, SI (Simon 1893; Simon 1898; Hirst 1911; Benoit 1978d; Saaristo 1999) BESaAce 05 Family GNAPHOSIDAE Banks, 1882 - flat-bellied ground spiders Camillina Berland, 1919 C. cordifera (Tullgren, 1910) DI: — Central and Southern Africa, Seychelles OR: AR, CE, CR, MH, PR, SI (Saaristo 1978; Platnick 1981; Bowler et al.1999; Saaristo 1999) BLS: AR, BI, CR, CS, CR, DE, MA Xerophaeus Purcell, 1907 X. espoir Platnick, 1981 DI: | Endemic OR: CE, MH (Platnick 1981; Saaristo 1999) BESaEes 06 Family LINYPHIIDAE Blackwall, 1859 - dwarf or money spiders Microbathyphantes van Helsdingen, 1988 M. palmarius (Marples, 1955) DI: — Sri Lanka, Seychelles, Myanmar, Polynesia OR: CS, MH, SI (van Helsdingen 1988, as M. asiaticus; Saaristo 1995; Saaristo 1999, as M. spedani) BLS? DE Neonesiotes Millidge, 1991 N. remiformis Millidge, 1991 DI: — Marshall Is., Caroline Is., Cook Is., Fiji, Samoa OR: CE, MH, SI (Saaristo 1999) BLS: DE, MA, NO Nesioneta Millidge, 1991 N. benoiti (van Helsdingen, 1978) DI: —_ Sri Lanka, Seychelles OR: AR,CS, CE, LD, MH, PS, PR, SI (van Helsdingen 1978, as Meioneta b.: Saaristo 1995: Bowler et al.1999; Saaristo 1999) BITS AUR, Jay Nipes, Thoea Saaristo, 1995 T. tricaudata (Locket, 1982) DI: — Seychelles, Malaysia OR: CE, MH, SI (Saaristo 1995; Saaristo 1999) BES: GRAMA 07 Family LIOCRANIDAE Simon, 1897 Othobula Simon, 1897 O. impressa Simon, 1896 DI: = Sri Lanka OR: AR, CE, MH, SI (Bowler et a/.1999, as Corinnidae: Genus ign. 1. sp. 1.; Saaristo 1999, as Corinnidae: Genus ign. J. sp. ign.) BLS: CSG) 08 Family LYCOSIDAE Sundevall, 1833 - wolf spiders Bristowiella Saaristo, 1980 B. seychellensis (Bristowe, 1973) DI: — Seychelles, Comoro Is. OR: AR, CE, LD, PR, MH, SI (Bristowe 1973; Saaristo 1978; Alderweilert 1988; Bowler et al.1999; Saaristo 1999) BES CS) NO Trochosa C. L. Koch, 1848 T. urbana (O. Pickard-Cambridge, 1878) CS, DE DI: Africa to India OR: AR, Ast, CF, CE, FE, MH, PR, SI, SP (Simon 1898; Hirst 1911, as Lycosa urbana; Bowler et al. 1999; Saaristo 1999) BES: CSADE 09 Family MITURGIDAE Lehtinen, 1967 - forest-floor spiders Palicanus Thorell, 1897 P. caudatus Thorell, 1897 DI: | China, Myanmar, Indonesia OR: SI (Saaristo 1999, as Miturgidae: Gen. sp. ign.) BESs DE 10 Family OCHYROCERATIDAE Fage, 1912 - midget ground weavers Roche Saaristo, 1998 R. roche Saaristo, 1998 DI: | Endemic OR: MH (Saaristo 1998) Biss Es Theotima Simon, 1893 T. minutissima (Petrunkevitch, 1929) DI: Pantropical OR: CE, MH, SI (Brignoli 1980, as Speocera bonaspei; Saaristo 1998, 1999) BLS: AR 226 11 Family OONOPIDAE Simon, 1890 - dwarf hunting spiders Brignolia Dumitresco & Georgesco, 1983 B. cubana Dumitresco & Georgesco, 1983 IDE Cuba OR: AR, CE, MH, Pov, SI (Bowler et a/.1999; Saaristo 1999, 2001b) BLS: BI Ischnothyreus Simon, 1892 1 pelifer (Simon, 1891) USA to Panama, West Indies, St. Helena OR: AR, CS; CE; MH, NO, SI (Benoit 1979, as Ischnothyreus sechellorum Bowler et al.1999; Saaristo 1999, 2001b) BES? DE; N© iesp.-@) BES?) BINCR Lionneta Benoit, 1979 L. sp. J) BLS: MA Lionneta n. sp. DI: Endemic OR: None BLS: CC(f), CR(m), GS(m) Lisna Saaristo, 2001 L. trichinalis (Benoit, 1979) DI: Endemic OR: AR, CE, MH, PS, SI (Benoit 1979, as Gamasomorpha trichinalis, Bowler et al.1999 and Saaristo 1999, as “Gamasomorpha” trichinalis; Saaristo 2001b) BES? DE Opopaea Simon,1891 O. deserticola Simon,1891 DI: | USA, West Indies OR: Asn, CS, CE, Faq, Pov (Saaristo 2001b) BLS: BI O. lena Suman, 1965 DI: Hawaii OR: AR, CE, MH, PS, PR, SI (Benoit 1979, as Gamasomorpha ladiguei; Bowler et al.1999; Saaristo 1999, as “Gamasomorpha” ladiguei; Saaristo 2001b) BLS: BI Orchestina Simon, 1882 O. justini Saaristo, 2001 DI: Endemic OR: SI (Saaristo 1999, as Orchestina sp. ign.; Saaristo 2001b) BLS: CC, CS, NO je] 12 Family OXYOPIDAE Thorell, 1878 - lynx spiders Oxyopes Latreillei, 1804 O. dumontii (Vinson, 1863) DI: — Africa, Madagascar to Seychelles OR: AR, MH, PR, SI (Benoit 1978b; Bowler et a/.1999; Saaristo 1999) BES] BIarE SMA 13 Family PHOLCIDAE C. L. Koch, 1851 - daddy-long-legs spiders Cenemus Saaristo, 2001 Carasp: DI: Endemic OR: None BLS: MA Modissimus Simon, 1893 M. culicinus (Simon, 1893) DI: — North, South America, Congo, Hawaii, Marshal Is. OR: AR. CS, CE, CR, GS, MH, PS, PR, SI (Bowler et a/.1999; Saaristo 1999, as Hedypsilus culicinus; Saaristo 2001a) BLS: NO 14 Family SALTICIDAE Blackwall, 1841 - jumping spiders Baviola Simon, 1898 B. spatulata Wanless, 1984 Diese Endemic OR: MH, SI (Wanless 1984; Saaristo 1999) BES a CRanE 15 Family SCYTODIDAE Blackwall, 1864 - spitting spiders Soeuria Saaristo, 1997 S. soeur Saaristo, 1997 DI: Endemic OR: CE, PS, SI (Saaristo 1997, 1999) BLS: BI, CC, DE, MA, NO 16 Family SELENOPIDAE Simon, 1897 - flatters or wall spiders Selenops Dufour, 1817 S. secretus Hirst, 1911 DI: Endemic OR: AR, CE, FR, LO, MH, PR, SI (Simon 1898, as S. radiata; Hirst 1911; Benoit 1978d; Bowler et a/. 1999; Saaristo 1999) BLS: CR, DE, MA, NO 17 Family SPARASSIDAE Simon, 1874 (= Heteropodidae Thorell, 1874) - giant crab spiders Heteropoda Latreillei, 1804 H. venatoria (Linnaeus, 1758) DI: Pantropical OR: BI, CE, Dsr, MH, Pov, PR, SI (Simon 1898, as H. regia; Hirst 1911, as H. regia; Benoit 1978c; Saaristo 1999) BES: Bly CesMiAIN® 228 Rhacocnemis Simon, 1898 R. guttata (Blackwall, 1877) DI: Endemic OR: CF, CR, MH, PR, SI (Blackwall 1877, as Sparassus guttata; Simon 1898; Hirst 1911, as S. guttatus & S. elegans; Benoit 1978c) BLS: CC, CR, FE, MA, NO 18 Family SYMPHYTOGNATHIDAE Hickman, 1931 - dwarf orb-weavers Anapistula Gertsch, 1941 A. seychellensis Saaristo, 1996 DI: Endemic OR: SI (Saaristo 1996) BES: CR 19 Family TETRAGNATHIDAE Menge, 1866 - long-jawed orbweavers and golden orbweb and silver marsh spider Leucauge Darwin in White, 1839 L. argyrescens Benoit, 1978 DI: — Endemic OR: MH, PR, SI (Benoit 1978b; Saaristo 1999) BLS: CR, DE, FE, MA, NO Nephila Leach, 1815 N. inaurata (Walckenaer, 1841) [palm spider] DI: South Africa to Seychelles OR: “AldVAR Coe CE, CR, FRA EDSMIE) Pov, PR, SIl.St) (Blackwall 1877, as N. inaurata and N. plumipes; Simon 1893, as N. madagascariensis; Simon 1898, as N. madagascariensis; Hirst 1911; Saaristo 1978; Benoit 1978b as N. inaurata ssp. Madagascariensis; Roberts 1983; Bowler et al.1999; Saaristo 1999) B. vanmoli Wanless, 1894 DI: Endemic OR: MH, SI (Wanless 1984; Saaristo 1999) BES: CClRE Cosmophasis Simon, 1901 Cosmophasis n. sp. DI: —Endemic(?) OR: None BLS: BI Epocilla Thorell, 1887 Epocilla n. sp. DI: — Endemic(?) OR: None BES2 Ce Goleba Wanless, 1890 G pallens (Blackwall, 1877) DI: Endemic OR: Ald, DE, MH, SI (Blackwall 1877, as Lyssomanes pallens; Hirst 1911, Wanless 1980, 1984, all as Asamonea pallens; Saaristo 1999) BLS: €C, CS, CR, DEY EESMAGNO 229 Hasarius Simon, 1871 H. adamsonii (Audouin, 1826) DI: | Cosmopolitan OR: CE, CR, MH, PR, SI (Saaristo 1978, as H. albocircumdatus; Wanless 1984; Saaristo 1999) BIESse CSV CREDESEE hE Heliophanus C. L. Koch, 1833 H. activus (Blackwall, 1877) DI: — Endemic OR: AR, CR, MH, PR, SI (Blackwall 1877, as Salticus a.; Simon 1893; Saaristo 1978; Wanless 1984; Bowler et a/.1999; Saaristo 1999) BLS: CC, CS, CR, DE, FE, GS, MA, NO Hyllus C. L. Koch, 1846 H. acutus (Blackwall, 1877) DI: Endemic OR: AR, DE, CF, CE, MH, PR, Prd, SI (Blackwall 1877, as Salticus a.; Saaristo 1978, as “Salticus” a.; Wanless 1984; Bowler et al.1999; Saaristo 1999) BLS: BI, CC, DE, FE, MA Myrmarachne MacLeay, 1838 M. constricta (Blackwall, 1877) DI: Endemic OR: AR, DE, LO, MH, PR, SI (Blackwall 1877, as Salticus a.; Wanless 1984; Gerlach et al.1997; Bowler et al.1999; Saaristo 1999) BES ACG CSyCReDEVEE: MA, N® Plexippus C. L. Koch, 1846 P. paykullii (Audouin, 1826) DI: | Cosmopolitan OR: BI, Coe, CE, LD, VA, MH, PR, SI (Simon 1898; Hirst 1911; Wanless 1984; Saaristo 1999) BLS: FE, MA Tetragnatha Latreillei, 1804 T. demissa L. Koch, 1872 DI: — South Africa, Australia to Tonga OR: Ald (Roberts 1983, as 7. grenda) BLS: CC T. mandibulata Walckenaer, 1842 DI: West Africa, Bangladesh to Philippines, Australia OR: Coe, LD, MH, PR, SI (Blackwall 1877, as T. minax; Simon 1893, as T. minax; Hirst 1911; Saaristo 1978; Benoit 1978a: Saaristo 1999) BLS: NO T. marginata (Thorell, 1890) DI: | Myanmar to New Caledonia OR: MH, SI (Saaristo 1978, 1999) BLS: CS Tetragnatha sp. (j) BESY eS DEVRE 230 20 Family THERIDIIDAE Sundevall, 1833 - cobweb spiders Achearanea Strand, 1929 A. labarda Roberts, 1983 DI: — Endemic OR: Ald, AR (Roberts 1983; Bowler et al.1999) BLS: CS, DE, MA Argyrodes Simon, 1864 A. argyrodes (Walckenaer, 1837) DI: Mediterranean to West Africa, Seychelles OR: Ald, MH (Saaristo 1978; Roberts 1983; Saaristo 1999, 2000) BUS RE SRE A. cognatus (Blackwall, 1877) DI: | Endemic OR: MH, PR, SI (Blackwall 1877, as Epeira cognatus; Simon 1898; Hirst 1911; Saaristo 1978; Roberts 1978; Gerlach et al. 1997; Saaristo 1999, 2000) BES: €GSEE.NO A. recurvatus Saaristo, 1978 DI: Endemic OR: MH, SI (Saaristo 1978; Roberts 1978; Gerlach et al. 1997; Saaristo 2000) BLS: DE,MA A. rostratus Blackwall, 1877 DI: Endemic OR: MH, PR, SI (Blackwall 1877, as Epeira rostratus; Simon 1893; Hirst 1911; Saaristo 1978; Roberts 1978; Gerlach et al. 1997; Saaristo 1999, 2000) BLS: CC, CR, DE, FE, MA, NO Coleosoma O. Pickard-Cambridge, 1882 C. adamsoni (Berland, 1935) DI: Pantropical OR: CE, MH, SI (Saaristo 1978; Roberts 1978, as Theridion a.; Saaristo 1999) BLS: DE, MA, NO C. blandum O. Pickard-Cambridge, 1882 DI: | Cosmopolitan OR: AR, MH, SI (Saaristo 1978, as Crysso acrobeles; Roberts 1978; Bowler et al.1999; Saaristo 1999) BLS: CS, DE, FE, MA, NO C. floridana (Banks, 1900) DI: Pantropical, greenhouses in Europe OR: AR, CE, LD, MH, PR, SI (Saaristo 1978; Roberts 1978; Bowler et al.1999; Saaristo 1999) BLS: CC, CS, CR, DE, FE, MA, NO 231 Dipoena Thorell, 1869 D. menustya Roberts, 1983 DI: Endemic OR: Ald (Roberts 1983) BLS: MA D. spundana Roberts, 1978 DI: Endemic OR: AR, LD, SI (Roberts 1978; Bowler et al. 1999; Saaristo 1999) BLS: DE, NO Theridion Walckenaer, 1805 T. clabnum Roberts, 1978 Di" Endemic OR: AR, CE, LD, MH, PR, SI (Roberts 1978; Bowler et a/.1999; Saaristo 1999) BiSs CC{ER. DE. NO 21 Family THERIDIOSOMATIDAE Simon, 1881 - ray spiders Theridiosomatidae sp. BLS: GSG.) Andasta Simon, 1895 A. benoiti (Roberts, 1978) DI sraeendemice OR: MH (Roberts 1978) BLS: CC, DE, FE, MA, NO 22 Family THOMISIDAE Sundevall, 1833 - crab spiders Firmicus Simon, 1895 F. insularis (Blackwall, 1877) DI: Endemic OR: MH, SI (Blackwall 1877, as Thomisus insularis; Simon 1898, as F. marginatus; Hirst 1911; Benoit 1978e) BLS: DE Thomisus Walckenaer, 1805 T. stenningi Pocock, 1900 DI: Africa OR: AR, CR, MH, PR, SI (Simon 1898 and Benoit 1978e, as Thomisus citrinellus; Bowler et al.1999, Saaristo 1999) BLS: DE, FE, NO 23 Family ULOBORIDAE Thorell, 1869 (3; 20-252) - hackled-orbweb weavers Uloborus Latreillei, 1806 U. plumipes Lucas, 1846 DI: Old World OR: AR, CR, MH, PR, SI (Blackwall 1877, as U. luteola; Saaristo 1978, as Uloborus sp. 1.; Benoit 1978b; Gerlach ef al.1997; Bowler et al.1999; Saaristo 1999) BESS BICC CSNGReDES FES GswMA : ton hee - 7 it Lore = an a Raby tinsel wusogie ahh Tyee iced, Wa FAibcagteRinarB I LS , ‘ te oe danetiny eis eine i a | ) | ete ahd aR yBiA, wo = Rateeee 5 > ie Aba B Je Fale ie a sera malistbane 8 ! PL: ‘Ly a - pein — FPG aime ; ern! | Ae yes. loa ray M2 x eon iv ats coe afi. : ea ae “ law tte i.) ail Nes Rabb: wi Sage (|e RE ube tea: He BY hay neat, ae en ee ret, wntlod reundoyn aA ee a Oras say ae ; : e i Oe ; iene hited oh: are “2! @ i ge fe amd, we Wi 13 IA aal a3 a (@0@ ‘oh ac? ‘ (OAD ao re, ‘0 7 __ noe Ky rhs aya D 1o7h, Bo! i ft yey tee " grobiqgs rag NCE Sn geraanit en cienemoeONaLst2 a) I Gi Mok , t if moe . qe gabine HORON ees mi peri agtig?s iTS { ye i): oh te - Ey : rye rw a “Re At iLike ateatynde | ; 7 ewer GENE Ww came q ORR ear Nidal, b./ 3 OR = To - - engin sn Sioa i" ain ind « tae BO a “ ‘ _ a> “we Rd eet biel a0 =i) ral me pees seid sj ia i iekye! A) mabe Ba . iting | tal B ihe le: (dirisbad aera Dean ET fe Siekeaab nt) 2 hug = OBL atop meter’ eat) Nor Aaa, peut oe =: ano ct Ch, Nii: ST Saari 3 o ay Teele: | on “a oi haa, iva pn salted (OUR! smtp eee es / Noy mem inieitinnaa - qeanirgad hes 1 Wie ™ ASSESSING CONSERVATION VALUE OF ISLANDS IN THE CENTRAL SEYCHELLES BY MICHAEL J. HILL! ABSTRACT Data gathered in the island assessment process are used to prioritise the islands visited (and, by extrapolation, other islands in the central Seychelles) for conservation value, particularly in regard to conservation of endemic land birds. Several criteria of particular importance for endemic bird conservation are identified, and these could be used in more rapid assessment of other islands in the area for conservation. INTRODUCTION Several authors have attempted to formalise criteria to evaluate land for conservation purposes in order that the most appropriate sites can be selected for protection (see, for example, Smith and Theberge, 1986; Usher, 1986). There is no simple consensus that can be applied in all situations although a number of biological and physical indicators that are commonly cited include the presence of rare species of animals and plants, or rare habitats, diversity (of species or habitats), size, “representativeness” or “naturalness”, and the relative fragility of an area or habitat (Bibby, 1998). In addition, social, cultural and management practicalities need to be considered, especially where an area has multiple use (such as scientific research or recreation in addition to conservation). While many criteria emphasise existing conservation values, the concept of “potential value” (Ratcliffe, 1977) or, in this case, “rehabilitation value”, is particularly important for the islands of the granitic Seychelles. The original habitats of all islands have been profoundly altered in the past 200 years. Active human intervention is likely to be necessary to realise the conservation value of any of the small or medium-sized islands. However, the term restoration (implying a return to the original state) is probably inappropriate for any such process involving the removal of alien species and introduction (or re-introduction) of native species. Instead, a partial restoration or rehabilitation 1s probably the most that can be achieved (Simberloff, 1990). The original vegetation and habitats of the smaller islands are likely to remain the subject of speculation; written records of island biota prior to human settlement are patchy and equivocal in nature and, while a fossil record may exist, conditions for preservation of biological remains such as pollen are more likely to occur on the larger, wetter islands. ' Nature Seychelles, PO Box 1310, Mahe, Seychelles. E-mail: birdlife@seychelles.net The island assessment procedure quantified various aspects of the current flora and vegetation, and fauna of the islands visited and these data can be used to develop priorities for island (and species) conservation in the Seychelles. In this report, data gathered on the 10 islands described in individual island reports will be considered. A large number of biological factors need to be considered in determining priority islands for conservation. Major factors include: 1) island size; 2) proximity of other islands; 3) island topography; 4) range of habitats (existing and potential); 5) extent of natural or near-natural vegetation (existing and potential); 6) existing biodiversity values; 7) invertebrate prey availability (existing and potential); 8) presence/absence of invasive introduced animals; 9) presence/abundance of invasive introduced plants; 10) pollutants and pathogens (existing and potential). BIOLOGICAL AND PHYSICAL FACTORS Island Size Island size is an important factor contributing to conservation value, through its influence on biological/historic features including: e potential populations of endemic species; e possibility of successful eradication of introduced species (human population also important); e range of available habitats and climate (geology, altitude range also important); e history of exploitation (accessibility, human population also important). Drawing on the theories of island biogeography (MacArthur and Wilson, 1967), it is often recommended that protected areas should be as large as possible to protect larger populations of individual species and to maximise the number of different species protected (Bibby, 1998). Larger populations are less vulnerable to extinction through stochastic events than smaller populations and may contain greater genetic diversity than smaller populations (Lande & Barrowclough, 1987). The central Seychelles is a small, isolated archipelago with a high degree of endemism among its species (Nussbaum, 1984b). The granitic islands, together with Bird and Denis, have a total land area of only 23,140 ha (approximately 90 square miles) (Seychelles Survey/Directorate of Overseas Surveys, unpublished data). This small potential range means that technically all endemic birds of the Seychelles qualify as threatened under IUCN criteria (Collar et al., 1994). Within the granitic Seychelles, island size varies considerably. Although there are over 40 islands (excluding unvegetated rocks), most are very small (Fig. 1). Only four islands exceed 1,000 ha in size and the largest individual island, Mahé, accounts for 66% of the total land area. 235 While the largest islands of the Seychelles would appear to offer greatest potential for conservation, several factors act to reduce their importance for conservation of endemic land birds. Mahé, Praslin and La Digue all have large human populations and associated problems: multiple ownership, pressure of development (especially important on coastal plateaux), the presence of large populations of domestic and feral animals, and regular traffic of cargo between islands (increasing the probability of transfer of alien predators and exotic plants). This increases the difficulty of eradicating introduced mammalian predators and the likelihood of re-invasion. The smallest islands, and even some of the unvegetated rocks, may have considerable conservation value as many have escaped the introduction of introduced predators and few have human populations. Such islands are of greatest value as nesting sites for seabirds and for some species of native reptiles and invertebrates that can tolerate arid conditions but cannot survive in the presence of introduced predators. The island assessment work concentrated on small- to medium-sized islands (between 28 and 286 ha in size) which offer some of the benefits of smaller islands (single ownership, small or no human population, potential for eradication of introduced species) but are large enough to support viable populations of endemic birds. Within the size range considered, larger islands are likely to offer the greatest opportunity for rehabilitation of a range of native ecosystems and endemic species. Number of islands size (ha) Figure 1. Size distribution of islands in the central Seychelles. Proximity of Other Islands The proximity of other islands helps to determine the rates of invasion by species (MacArthur and Wilson, 1967). Neighbouring islands can act as a source of invasion, especially by mobile organisms such as birds (and hence, for example, bird-distributed plant species). The proximity of Thérése and Conception to the island of Mahe (which supports most of the endemic plants of Seychelles) probably contributes to the large number of endemic plant species on these small islands. In theory, a cluster of small proximate islands under conservation management could provide important conservation benefits, especially for vagile organisms such as birds. Occasional natural transfer of individuals between islands could ensure continued gene flow between populations and allow populations to function as a single, large population (such transfers have been observed in Seychelles magpie-robin: Shah and Parr, 1999). This might be particularly important for Seychelles birds; eradication of introduced pests and management for conservation is much easier on smaller, rather than large, multiple-owner islands. Groups of proximate islands could be gradually established a part of a long-term conservation strategy. Proximity does, however, carry a number of disadvantages; in particular, it allows the spread of diseases and the invasion of exotic species. Thérese Island, less than 1 km from Mahé, has an established infection of takamaka wilt disease, while Conception, further from the mainland, does not (although takamaka trees are found there). But proximity alone cannot determine invasion of such harmful species. Factors such as wind direction also play a role in dispersal/invasion: North Island, 7 km from Silhouette, has both takamaka wilt and the invasive weedy shrub Clidemia hirta, both probably invaders from Silhouette (carried by mobile vectors). Some invasive species are carried by human vectors, for example the crazy ant Anoplolepis gracilipes, carried to new islands with plants or other cargo. In this case, the amount of human traffic (and the nature of cargoes moving between islands) will influence invasion to a greater extent than absolute distance. Island Topography Island topography (range of altitudes, presence/absence of “plateau’’) has an important influence on the rehabilitation potential of islands. In general, maximum island altitude 1s closely correlated to island size (Pearson Correlation Coefficient = 0.828; p < 0.001). For larger islands such as Mahé, altitude has an important influence on rainfall; rainfall is greater at higher altitude stations and also at lower stations that are not in the rain shadow of hills (Walsh, 1984). Constant high humidity and high rainfall allow mist forests to thrive on the hills of Mahé and Silhouette. However, on smaller (lower) islands altitudes are probably less important in determining climate. More important factors influencing the length and severity of dry seasons include an island’s position relative to high islands (rain shadow effects, etc.) and its position within the archipelago (islands to the north have a shorter dry season than those further south: Walsh, 1984). Maximum altitude alone is a probably poor indicator of rehabilitation potential for islands. However, topography (and, in particular, size of plateau) has a greater degree of biological importance. The plateaux are composed of recent (Jess than 6,000 years old) calcareous deposits. On some islands (including Cousin, Frégate, Bird) these have combined with guano to form cemented sandstone (Braithwaite, 1984). In addition to the calcareous deposits of plateaux, alluvial deposits occur at the mouth of rivers and streams. These conditions are rare on small islands and tend to be marked by mangrove habitats. The alkaline soils of plateaux are generally more fertile than those of uplands (Braithwaite, 1984). The productivity of terrestrial invertebrates appears higher in plateau habitats than on hills, so birds feeding on ground invertebrates (such as Seychelles magpie-robins) are likely to reach greater densities on plateaux and islands with large plateaux to support larger populations. WN eS) — Plateaux are also easier to manage effectively than hill habitats. While plateau woodland can be dense (especially where there is heavy regeneration of coconut), plateaux are not physically inaccessible as rocky slopes and glacis can be. Figure 2 shows the extent of land in altitude categories for all islands studied. Table 1 has approximate extents of true coastal “plateaux” (areas of predominantly coralline deposits of altitude 5 m asl or less). Cousin O< 10m Conception aE 010-50m Therese oo [50-100m Gd Soeur oe | 1 100-450m @150-200m Marianne ®200m+ Bird : Denis North Felicite Curieuse 0 50 100 150 200 250 300 Area (ha) | Ik Figure 2. Altitude distribution of land area. From maps of Seychelles, Directorate of Overseas Surveys/Seychelles Survey. Table 1. Area of coastal plateau. Figures in parentheses = area excluding mangrove habitats. pls ancl aan eee PLoxtrarcal(ia))i Denis 143 Bird D1 North 49 Curleuse 48 [39] Cousin 19 [18] Féliciteé 4 Grande Soeur 4 Thérese 3 Marianne 9) Conception 0) Coralline islands are similar to the plateaux of granitic islands; Denis Island even has freshwater marsh, a feature of coastal areas on granite islands. Of the granitic islands. those with the largest plateaux are Curieuse and North islands. For both these islands, the 238 plateaux alone are larger than an island such as Conception. Although Feélicité is larger than North, it has a significantly smaller plateau and is a much higher island. This may explain why Felicité has a number of endemic plant species not present on North Island (see “Existing Biodiversity Values”, below). Range of Habitats Habitat diversity is a commonly used criterion for ranking land for conservation purposes (Bibby, 1998). In general, it is felt preferable to conserve areas with the widest range of habitat types. The greater the number of habitats protected, the greater are the opportunities to preserve a wide range of plant and invertebrate species (although not all habitats are equally important to conservation: see below). However, small islands cannot conserve all the habitats represented in the Seychelles; high-altitude biomes are entirely unrepresented on the islands assessed. In general, larger islands have a greater range of habitat types than smaller ones and granitic islands have a larger range of habitat types than coralline islands of similar SIZe. Extent of Natural or Near-Natural Habitats All islands in the granitic Seychelles have been altered (usually to a large extent) by human intervention and the greatest change has occurred at middle to lower altitudes (below about 500 m). Thus, there are no examples of small, pristine islands to act as blueprints for island restoration, and records of early travellers offer little useful information. The original vegetation and habitat structure of islands cannot be exactly reconstructed. However, habitats can be broadly classified according to their degree of “naturalness”; most islands have been cleared for coconut plantation and, where this has fallen into disuse, the regenerating forest and scrub habitats are dominated by either introduced or native species. “Near-natural” habitats can be defined as those dominated by native species, in vegetation types which would persist on islands prior to human interference (usually, woodland or scrub). Generally, islands with a greater number of different near-natural habitats and larger areas of near-natural habitats should be preferred to those which are dominated by anthropogenic habitats. Of these habitats, woodland is probably the most important for endemic birds. Table 2 shows the approximate extent of near-natural habitats on the islands studied. Habitats are separated into native woodland, scrub (including beach crest vegetation), mangrove and other wetland. Wetlands, especially freshwater wetlands, have conservation importance for a number of reasons: e They provide habitat for a number of endemic freshwater invertebrates and vertebrates (Stevenson et al., 1997); e Invertebrates with aquatic larvae often have winged adults which may be taken as food by endemic insectivorous birds (e.g. black paradise flycatcher; Watson, 1991); and e They are nationally threatened (since most wetlands in Seychelles are small, they are easily threatened by pollution, drainage and other human impacts: Stevenson et al., 1997; Shah, 1997). LB Table 2. Approximate extent of near-natural habitats on islands studied. Area (ha) Island Native Native scrub Mangrove Other wetland Total woodland (including beach crest veg.) Bird 18 50 0 0 68 0 4 0 0 4 Cousin 20 4 <1 25 Curieuse 3) 87 S) 1 148 Denis 28 6 0 <1 34 Félicité 13 2 0 <1 135 Grande Soeur 7h 1 0 <1 1p) Marianne 7 v 0 S Il 14 North 16 l 0 1 17 Thérese 2 l 0.10). The lack of correlation between importance ratings for plants and birds stems from the different factors underlying their distributions. For several endangered endemic land birds (including Seychelles magpie-robin, warbler and fody) the primary factor determining current distribution appears to be introduced mammalian predators, principally cats and rats. The distribution of endangered endemics 1s thus partially a relict (due to survival of birds on predator-free islands such as Frégate and Cousin) and in part an artificial construct as further islands (such as Cousine, Aride) were freed of introduced predators and endemics translocated. Predation may also play a role in the decline of endangered endemic plants through the destruction of flowers and fruit before maturity (Carlstr6m, 1996a). However, direct predation appears to be less of a threat to the survival of plant species than it is to birds. Grazing mammals, such as goats, are not presently a threat to endangered plant communities in the granitic Seychelles. The major threats to endemic and endangered plants are habitat destruction and invasive plants (Fleischmann, 1997), although for certain species direct exploitation may also be significant (Shah, 1997). However, although the ranking of islands for bird and plant conservation differ, there are some similarities between the lists in Table 4. The coraliine islands Bird and Denis, which are remote from other islands in the archipelago, have low habitat diversity and were most comprehensively affected by human intervention, emerge as the islands with lowest biodiversity rating for both groups. While restoration of granitic islands of the central Seychelles may include the enhancement of existing endemic floras, this would probably be inappropriate on the coralline islands. The lack of endemic species would not in itself prevent these islands being used for translocations of endemic birds (indeed, it might allow a greater degree of environmental intervention prior to translocation and would eliminate the possibility of negative interactions between translocated and pre-existing endemic taxa) but would probably reduce the overall conservation gain. Invertebrate Prey Availability Invertebrates were collected using several different methods to provide data on prey abundance for insectivorous birds. The techniques giving comparative data of greatest importance for endemic birds are pitfall trapping and leaf-invertebrate counts. Pitfall trapping. Results suggested that invertebrate density was highest on coralline islands, followed by the plateaux of granitic islands. Hills on granitic islands had lower invertebrate density. There appeared to be no significant association between vegetation parameters and the pitfall catch, although trapping was carried out within a narrow range of conditions (in woodland and scrub). While the taxonomic composition of assemblages on coralline islands differed from those on most granitic islands, they were similar to those on Cousin Island (which already supports a population of Seychelles magpie-robin). This suggests that the priority islands for Seychelles magpie-robin introduction are the coralline islands (Denis, Bird) or islands with large plateaux (Curieuse, North) irrespective of the nativeness of their vegetation. 243 However, invertebrate density is only one aspect of magpie-robin feeding ecology. Food availability is also dependent on the suitability of habitat for feeding. On Frégate, magpie-robins feed primarily in open areas free of herbaceous vegetation (Watson et al., 1992). On Denis Island, herbaceous and shrub layer vegetation was generally dense with little ground free of ferns (Nephrolepis and Phymatosorus) and young coconuts Cocos nucifera. Management of Denis Island’s vegetation would be necessary before introduction. On Bird Island, the high density of crazy ants Anoplolepis gracilipes 1s likely to influence magpie-robin behaviour, possibly disrupting feeding and nesting. Leaf invertebrate counts. These counts give information on the food availability for small insectivorous birds including Seychelles warbler, paradise flycatcher and white- eye. The density of invertebrates on leaves varies greatly between wet and dry seasons but, in general, native plants have a higher density of invertebrates associated with them than do introduced species. Densities of invertebrates on Morinda citrifolia are comparable with those on native rather than introduced species. There 1s no significant difference in invertebrate density between trees in hill and plateau locations. Islands with the greatest potential food supply for small insectivorous species are those with the largest number of native trees (Félicité, Curieuse). However, the smallest island studied (Cousin) supports a population of Seychelles warbler suggesting that (with habitat restoration) any of the islands studied would be large enough to support this species. Presence/Absence of Introduced Animals Animal communities of remote oceanic islands tend to be more susceptible to invasion than communities on continental land masses (Elton, 1958) and introduced species of animals and plants have a disproportionately large impact upon island ecosystems (Williamson, 1996). Exotic species can have far-reaching effects; introduced animal species, through patterns of grazing and predation, often favour the establishment and spread of exotic plant species over native flora (Stone ef a/., 1992). In general, only a small proportion of alien species become established as serious pests. However, since there are no native terrestrial mammals in the Seychelles, it is likely that all of these species have an impact upon natural communities (Racey and Nicoll, 1984). In addition to mammals, animal introductions to the granitic Seychelles have included birds (seven species established; Diamond, 1984; Skerrett er a/., 2001), reptiles and amphibians (at least four species established; Cheke, 1984; Nussbaum, 1984a and b), freshwater fish (one or more species established) and an unknown number of invertebrate species. For many of these species, it is impossible to assess their ecological impact. Information is more complete for the more conspicuous vertebrates, particularly mammals and birds. In Seychelles, the mammal species with the greatest ecological impact are cats Felis catus and rats Rattus spp., which are predators of native species and (to a lesser extent) rabbits Orvctolagus cuniculus, which can destroy native vegetation. Cats and rats are widely established on islands in the archipelago and were among the earliest introductions to the islands; cats and ship rats Rattus rattus were probably first introduced around the time of the earliest permanent human settlement of the Seychelles in the late eighteenth century. The Norway rat Rattus norvegicus 1s a more recent introduction with 244 a relatively restricted distribution (Hill, in prep). These alien predators have long been associated with the loss of endemic birds (Newton, 1867: Diamond, 1984). Rats and cats have been implicated in the extinction of at least 27 populations of Seychelles land birds (Diamond and Feare, 1980). Feral rabbits are today restricted to one smali seabird island, although domesticated animals are commonly kept in captivity on larger islands. Other alien mammals are less destructive or less firmly established: these include black-necked hares Lepus nigricollis, mice Mus domesticus, tenrecs Tenrec ecaudatus, dogs Canis familiaris, cattle Bos taurus and pigs Sus domesticus. Of the small number of introduced land bird taxa surviving in the Seychelles, several appear to have minimal impact on native species. Three species (barred ground- dove Geopelia striata, common waxbill Estrilda astrild and Madagascar fody Foudia madagascariensis) are largely restricted to open, anthropogenic habitats. The Madagascar turtle dove Streptopelia picturata picturata appears to have caused the effective extinction of the endemic race of the same taxon (S. p. rostrata) but there is no evidence of ecological differences between the races so any effects on other species are likely to be limited. The most recent land bird species to become established, the ring-necked (rose- ringed) parakeet Psitticula krameri appears restricted in population and ecological influence at present (Skerrett et a/., 2001). Two introduced bird species with important ecological effects in near-natural habitats are the barn owl 7yto alba and common mynah Acridotheres tristis. Barn owls were introduced from East Africa in 1949-52 (Blackman, 1965) in an unsuccessful attempt to control introduced rats. In addition to rats, they take most small birds (in particular, fairy terns Gygis alba: Penny, 1974). Mynahs are omnivorous but are nest predators of Seychelles magpie-robin (McCulloch, 1996) and possibly other endemic bird species. There are many introduced invertebrate species in the Seychelles, some deliberately introduced to provide biological control of agricultural pests (for example, beetles of the family Coccinellidae to control scale insects on crop plants) while other introductions were accidental. At least one introduced invertebrate is known to have important deleterious effects to conservation: the crazy ant Anoplolepis gracilipes (Haines et al, 1994; Hill in prep). Table 5 shows the distribution of six introduced animals of particular conservation concern, between islands studied. Table 5. Introduced animal species present on the islands assessed. Bir = Bird; Con = Conception; Cou = Cousin; Cur = Curieuse; Den = Denis; Fel = Félicité; GSo = Grande Soeur; Mar = Marianne; Nor = North; The = Thérése + = present; (+) = present early 2000, probably eradicated by mid-2001; ? = probably present but not recorded during island assessment survey Bir (Con {Gour “Cure Den ele 4GSor Man aINor: | iihe Felis catus - ats = (G2) (G9) a ar ot + i Rattus norvegicus = + = = : i 2 2 B : Rattus rattus = = = + a + + + + + Acridotheres tristis 7 + a a its 17 “ ts aly af Tyto alba < ? ? + z ? 9 ? in, 9 Anoplolepis gracilipes os 4p + 2 + + . + = + TOTAL 2 4-5 2-3 3 3 4-5 3-4 4-5 4 4-5 The presence/absence of species on islands does not fully reflect their conservation impact except perhaps for mammalian predators. For non-mammals, density of populations (and hence, impact) may vary greatly between islands. Thus, while Anoplolepis gracilipes forms vast colonies and dominates near-natural habitats on Bird Island, it is widely present on other islands without having such severe impacts. The common mynah is found on all islands but 1s rather rare on Cousin. In the case of cats and ship rats, however, there is usually a simple relationship between the presence of the species on an island and the loss of susceptible native bird species. Although introduced mammals have a great impact upon native species, it is feasible to eradicate populations. The removal of alien predators in the Seychelles has been directly responsible for the continued survival of at least one endangered endemic bird species, Seychelles magpie-robin. The last surviving population of this species was threatened by the introduction of cats to Frégate in 1958. In 1960, over 80 cats were killed (Penny, 1968), clearing the island of mammalian predators (at least temporarily). In New Zealand, cats have been eradicated on islands as large as 3,000 ha (Veitch and Bell, 1990). Only two of the granitic Seychelles exceed this size (and both of the large islands have permanent human populations, making it difficult to eradicate cats). In July- August 2000, rat and cat eradication was attempted on three medium-sized islands in the Seychelles archipelago, by Don Merton and colleagues from the New Zealand Department of Conservation. Anticoagulant baits were applied aerially (for rats) and ground-baiting and trapping were used to remove cats from Curieuse and Denis Islands. On Frégate Island, only rat baiting was used (no cats present). Cats appear to have been successfully eradicated on Curieuse and Denis and Norway rats on Frégate but, by mid- 2001, ship rats were again recorded on Curieuse and Denis. It 1s not clear whether eradications were unsuccessful on these islands, or these rats represent subsequent reinvasion. Invasive Weed Species On most small islands of the Seychelles the flora is dominated by introduced species which form 44-69% (or more) of the plant list on the islands studied. Procter (1984) estimated that nationally around 165 exotic plant species had become established in the wild (forming 22% of the flora) and a further 249 (33%) were known only in cultivation. The latter figure has certainly increased as new species are constantly being added to the garden flora of Seychelles (Shah, 1997). Globally, only a small proportion of introduced species become established in wild communities with only 10% of introduced, established species becoming pests in their new environment (Williamson, 1996). Procter’s figures suggest that a higher-than-expected proportion of species imported into Seychelles have become established, perhaps due to Seychelles climate or the relative invadability of species-poor island vegetation, especially when modified by human activities. It is difficult to estimate the number of exotic species that have become serious invasive weeds in the granitic Seychelles in part because weediness is hard to define in the context of some fundamentally altered ecosystems. Thus, while agricultural weeds are easily identified, as are species invading largely natural ecosystems (such as glacis habitats which may be invaded by A/stonia macrophylla: Carlstrém, 1996a), in most mid- 246 altitude forests on the large islands native trees have been replaced by exotic plant species. In natural ecosystems, invasive exotics are a threat to native vegetation through displacement and shading. Because, in general, introduced plant species support an impoverished insect fauna compared to that of native plant species, large-scale replacement of natives by naturalised species is likely to lead to higher-order effects, such as reducing the food supply of endemic birds. Both Carlstr6m (1996a) and Fleischmann (1997) attempted to identify species most threatening to native vegetation in Seychelles (particularly, the larger islands). Twenty-six invasive plant species thought to threaten native habitats are listed by Carlstr6m (1996a) including one fern, two grasses, 10 shrubs and 13 trees. However, this list includes several species of doubtful origin including one tree regarded by Friedmann (1994) as native (Trema orientalis) and one grass regarded by Robertson (1989) as native (Brachiaria umbellata). Fleischmann (1997) regarded 34 introduced species as invasive in his survey of Mahé and Silhouette; most of these species were trees, but seven shrubs, three climbers, a bamboo and two herbaceous species were also included. Fleischmann’s list included one native species, Cocos nucifera, which probably showed restricted distribution prior to human colonisation. The two lists share 15 species in common, and both suggest that the greatest threat to native ecosystems (at least on large islands in Seychelles) comes from cinnamon Cinnamomum verum and Chinese guava Psidium cattleianum. However, both earlier lists are primarily concerned with invasive species in native forest habitats of the larger islands (Mahé and Silhouette in the case of Fleischmann, 1997). On smaller, drier islands, the relative importance of different weed species is likely to differ. In order to assess the weed status of introduced species on smaller islands of the granitic Seychelles, data from plant species lists and vegetation plots were used to provide a measure of distribution and density of populations. While introduced species form a significant part of the flora of smaller islands, most are not widespread; 98 of 295 species recorded in species lists (33%) were found on only one of 11 islands. Only 58 species (20%) occurred on six or more islands. Many of the introduced species are ornamentals which may persist 1f cultivation were abandoned (as in the case of Codiaeum variegatum which survives around the ruins of the leper colony on Curieuse Island), but are unlikely to actively spread into near-natural vegetation. Ornamentals seem less of a threat to natural ecosystems than species introduced for economic purposes; only two of the invasive species listed by Fleischmann (1997) are likely to have originated as ornamentals (Acalypha wilkesiana, Lantana camara). Data from vegetation plots identify those species that have successfully entered near-natural plant communities on a wider scale. Figure 3 shows measures of distribution between 10 islands and within islands (for islands on which species present, percentage of random vegetation plots in which the species was recorded) for all species which are definitely, or probably introduced (definitions of introduced status from Friedmann, 1994). In addition, Cocos nucifera was included as its present distribution 1s largely the result of plantation agriculture of the nineteenth and twentieth centuries. Species are divided by life-form, as this has a bearing on the relative importance of species as weeds: trees, shrubs and large lianas are more likely to reach pest status in woodland and scrub habitats. Species found in 20% or more of vegetation plots on islands on which they occur are identified. Plots with species (%) 90 80 70 60 50 40 Mor cit Aa Asy B 30 Lan cam Qo * Ade pav 0 1 2 3 5 6 il 8 9 10 Number of islands sp. recorded on Figure 3. Distribution of introduced species between and within islands. These data suggest that the most invasive alien species on small islands are Cinnamomum verum (Cin ver) and Chrysobalanus icaco (Chr ica). Cocos nucifera 1s ubiquitous and regenerates strongly to form a dense scrub of little value to endemic species. Asystasia “species B’(sensu Friedmann, 1994) occurs on all islands but its oO Herb + Liana 4 Shrub * Tree 247 impact is probably minor. Lantana camara (Lan cam) was recorded in species lists from several islands but only occurred in vegetation plots on one island (North). It is a fast- growing, weedy shrub of open ground that has come to dominate former coconut plantations on North Island but probably cannot survive heavy shade and is not a significant problem in established woodland habitats. The same is likely to be true of Clidemia hirta, identified as a weed species on Silhouette and Mahé (Gerlach, 1996a), and a recent invader of North Island. Morinda citrifolia (Mor cit) 1s doubtfully native (Friedmann, 1994; Gerlach, 1996b; Sauer, 1967), supports an extensive insect fauna and has fruit favoured by feeding giant tortoises. Psidium cattleianum (P. littorale), identified by Fleischmann (1997) as the second most prominent invasive species on Silhouette and parts of Mahé (after Cinnamomum verum), was only recorded in vegetation plots on two islands where it occurred in six (of 77) plots surveyed. In all, only four trees of over five metres were recorded. The vegetation plot analysis suggests that a small number of (mainly) woody species are the major invasive plants of conservation concern, at least in near-natural woodland and scrub habitats. Vegetation plots were not carried out in other habitats, most notably glacis, a naturally open habitat threatened by a small number of invaders including A/stonia macrophylla (Carlstr6m, 1996a), and freshwater habitats. The latter 248 support a range of exotic species that have become pests in parts of Seychelles, including Pistia stratiotes, Eichornia crassipes and Ipomoea aquatica (Stevenson et al., 1997). Data on introduced weeds are summarised in Table 6, showing species in four categories: a) those woody species which are currently widespread and invasive; b) species which have the potential to become widespread weeds but are currently restricted in distribution (from Carlstr6m, 1996a; Fleishmann, 1997); c) species which are potentially invasive in open, glacis habitats (from Carlstrém, 1996a; Fleishmann, 1997; Friedmann, 1986; and personal observation); and d) species which are potentially invasive in wetlands (from Stevenson et al., 1997). Species which were not recorded on any island (probably restricted to the larger islands) are omitted. In general, coralline islands and small islands have the lowest score for invasive species. The highest scores were for larger granitic islands with a history of cultivation. The lowest score on any of the granitic islands was for Cousin (a nature reserve) but the island of Marianne also had a relatively low score. Marianne had a wide range of weeds but several species (such as Cinnamomum) were only present in small numbers and Chrysobalanus appeared to be absent. 249 Table 6. Introduced invasive plant species on the islands assessed. For island names, see Table 5S. Extent of invasion: 1 = present in small numbers (usually less than 100 individuals per island); 2 = 100-1000 individuals, strong regeneration from seed or vegetative propagation, species dominating small areas of habitat to the exclusion of native species; 3 = very invasive (1000+ individuals, very strong regeneration, large proportions of island dominated by the species, to the exclusion of native species). Bir Conws Cougs Cum 7 chum hells GSOm Mare Nom lhe Woody species invading woodland and scrub habitats Adenanthera pavonina 2 1 I, 2 2 2 1 2 D Anacardium occidentale 2 2 2 1 1 D 2 Carica papaya 3 3 2 3 1 1 1 1 2 Chrysobalanus icaco 2 3 3 3 2 3 Cinnamomum verum 3 3 2 3} 1 3 Cocos nucifera* 3 3 2 3 3 3 3 3) 3 3 Lantana camara Z 3 1 Passiflora suberosa 2 2 2 D 2 2 y} 2 Z Species potentially invasive of woodland or scrub habitats Clidemia hirta ] Psidium guajava 1 1 2 3 ] Psidium cattleianum 1 D, 1 Paraserianthes falcataria 2 2 l Syzygium jambos 2 Vanilla planifolia 2 2 2 2 2. 2 2 2 Species potentially invasive of glacis or open habitats Alstonia macrophylla 2 2 3 2 Ananas comosus D D 2 2 l 1 2 Dicranopteris linearis * 3 2 2 Furcraea foetida z 2 I 2 ] l 2 2 Panicum maximum 2 1 ] 2 2 2 2 Species potentially invasive of wetlands Ipomoea aquatica 2 ] Total 8 Dil 9 32 18 26 24 15 * Native or doubtfully native species: see Gerlach (1996b), Friedmann (1994). oP) bh J J Pollutants and Pathogens Pollution and the presence of pathogens all have an impact on individual native species. In some cases, pollutants have been identified (or inferred) as major contributors to a decline in endangered species. On Mauritius, it has been suggested that declines in the populations of the endemic Kestrel and Cuckoo-shrike were caused by the use of organochlorine pesticides (Safford and Jones, 1997). In Seychelles, a range of persistant organic (and inorganic) compounds were used in the twentieth century for pest control on plantations. There is little evidence regarding the levels of use although it is likely that usage in Seychelles was less intense than in Mauritius. 250 A range of natural pathogens are important to individual species, and thus to habitats. An example is the wilt disease of takamaka Calophyllum inophyllum, probably caused by the fungus Leptographium calophyli (Ivory et al., 1996; Wainhouse et al., 1998). Takamaka is a native tree, which commonly grows at beach crests, helping to protect them from erosion (for example, on Mahé, Praslin, Curieuse, Grande Soeur). It often forms dense stands in coastal plateau forest (on La Digue, Curieuse, North Island), and occurs in hill forest (on Marianne, Grande Soeur, Curieuse). The wilt fungus causes extensive wilting and dieback of takamaka trees, and can lead to complete defoliation and death of trees within months (Ivory ef al., 1996). Wilt disease was first noted on Mahé in 1994, but has now spread to a number of islands (Hill et a/., in prep.), some of which have lost many of their takamaka trees (see Table 7). The endemic bark beetle Cryphalus trypanus probably acts as a vector of the disease (Wainhouse et al.,1998). Table 7. Current status of takamaka and takamaka wilt disease on islands studied. From Hill et a/., in prep. Takamaka Wilt disease Bird Only one or two trees, planted Absent Conception | Occasional component of hill woodland Absent Cousin Few trees Absent Curieuse Many trees, large areas of takamaka forest on plateau First symptoms observed and trees in mixed hill woodland 1999, extensive death in one area of forest Denis Few trees First symptoms observed 2001 Felicite Important component of hill woodland Absent Grande Important part of hill woodland, old trees present on Absent Soeur beach crest Marianne Significant component of hill woodland Absent North Many trees, large areas of takamaka forest on plateau Present, causing death of and trees in mixed hill woodland hundreds of trees Thérese Found in hill woodland, old trees present on beach Present. Most beach crest crest trees dead, trees on hill survive Takamaka is one of the most widespread native trees in the archipelago and is a component of near-natural ecosystems on most of the small islands. Loss of trees to takamaka wilt is of particular importance on islands where it forms a major component of plateau woodland, for example, La Digue and North Island. On both these islands, takamaka and badamier Terminalia catappa dominate plateau woodland but many mature takamaka trees have been affected by the disease. The longer-term effects of takamaka wilt are unknown; there is some evidence that a proportion of trees recover without human intervention (FAO, 1997). In areas of high landscape value on large islands, trees have been treated with fungicides but this is a labour-intensive and expensive method inappropriate for use on a larger scale. Early eradication attempts and the introduction of regulations prohibiting the inter-island transfer of takamaka wood may have had some effect in delaying the establishment of the disease on the second largest island of the 251 granitic Seychelles, Praslin, but personal observation suggests that takamaka wilt is now well established there. A second novel wilt disease affecting sandragon Pterocarpus indicus, has recently been recorded on Mahé (Seychelles Nation, 8'" May 2000). Sandragon is an introduced tree and is less widespread on smaller islands than takamaka so the disease is of less conservation concern than takamaka wilt but on certain islands (such as Frégate), sandragon 1s an important component of woodland vegetation. The source of such novel pathogens in Seychelles is unknown (Ivory et al. 1996) but once introduced even strict quarantine measures seem unable to control the spread of virulent pathogens to a large number of islands. While it seems likely that higher levels of human movement between islands increases the risk of transfer of pathogens (probably accounting for the appearance of takamaka wilt on Denis, a remote coralline island), diseases can reach even relatively remote uninhabited islands such as North Island. The true threat to native species and ecosystems from such factors is difficult to predict and resolve. CONCLUSIONS: ASSIGNING CONSERVATION VALUES A range of biological and physical factors considered above are summarised for each island surveyed in Table 8. The aim of the table 1s to illustrate the overall conservation value of each island, including both potential (rehabilitation) values and existing values. Some of these values (size of island and plateau) are unchanging whereas others (number of alien animals, invasive weeds, extent of semi-natural vegetation) may be increased by active management. Large granitic islands, and coralline islands, emerge as having particularly high conservation values in this simple ranking. The largest islands, such as Curieuse and Félicité, have a wide range of native habitats and relatively large areas of plateau forest which would be suitable for introduction of Seychelles magpie-robin (and possibly black paradise flycatcher). In both cases, existing biodiversity values are high so the removal of introduced vegetation and other conservation management would protect a range of endemic forms. The coralline islands Bird and Denis were both severely impacted by guano mining and coconut planting in the twentieth century (Stoddart and Fosberg, 1981) and today are dominated by former coconut plantations, although Denis has large areas of badamier Terminalia catappa woodland and Bird has some Pisonia grandis. While both islands have introduced crazy ants, on Denis these occurred in a restricted area and could be controlled. On Bird Island, the infestation 1s extensive and is having a serious effect on biodiversity. Both coralline islands appear to be outside the natural range of many of the endangered endemic birds of Seychelles. The only endemic species to have been recorded on the coralline islands are a sunbird Nectarinia sp. (Stoddart and Fosberg, 1981) and Seychelles blue pigeon Alectroenas pulcherrima. While reconstructing former ranges of birds is difficult as early ornithological records for the Seychelles are sketchy before 1865 (Rocamora and Skerrett, 2001), it seems likely that few of the granitic Seychelles endemic birds were ever present on the close coralline islands. However, 252. coralline islands appear to be suitable for some of the endemic land birds and previous translocations of endemic birds to coralline islands within the Seychelles have been successful. The Seychelles magpie-robin survived for over 50 years on the coral island of Alphonse before being exterminated by introduced predators or habitat change in the mid-twentieth century (Collar and Stuart, 1985) and the Seychelles fody was translocated to D’Arros in 1965 (Penny, 1974), where the species survives (BirdLife International, 2000). The eradication or control of alien predators and rehabilitation of woodland habitats dominated by native tree species would increase the likelihood of success of such translocations. Translocations to coralline islands could be used as part of a strategy to extend the range and increase populations of endemic birds requiring less intensive input than captive management. The remoteness of the coralline islands from the central granitics could be advantageous (allowing isolation from diseases) but would also act as a barrier to natural recolonisation of further islands. Table 8. Overall island rankings based on criteria discussed above. l 2 3 4 5 6 Total Total rank Bird 5 2 3 10 1 1 DED ps Conception 9 10 M5 4 iy, 8.5 48.0 10 Cousin 10 5) 5 TES 2) Dy, Se5 5) Curieuse l 4 l l 8.5 3.5 19.0 1 Denis 4 i 4 9 4 3.5 DONS 3 Félicité D 6 D 2 6 8.5 26.5 4 Grande Soeur vi 7] 6 6 5 5 36.0 ii Marianne 6 9 8 5 3 8.5 B95 8 North 3 3 Ti USD 65) a ale) 35.0 6 Wherese 8 8 0.5 3 10 8.5 47.0 9 1 = size of islands. 1=largest, 10 = smallest 2 = area of true coastal plateau: 1 =large, 10 = small 3 = area of existing near-natural habitat: 1= large, 10 = small. 4 = existing number of endemic/threatened plant species: 1 = many, 10 = few 5 = score for existing introduced weed species: 1 = few, 10 = many 6 = existing number of introduced animal species: 1 = few, 10 = many Although Cousin is already managed for conservation and has a high proportion of its land area under semi-natural forest, its small size means that it does not emerge strongly in this particular analysis. North Island, although much larger with a larger plateau, ranks lower overall because most of its near-natural habitat has been lost over the island’s long history of human use. North Island’s existing biodiversity values are low. A small proportion of the flora is native and there are only two endemics. However, given active management for conservation, its potential value for conservation of a variety of endemic birds is high. The small, rocky islands of Thérése and Conception are identified as having the lowest rehabilitation values. These islands are predominantly open rocky hills with a high proportion of glacis. However, despite the island’s small size and dominance by introduced species, Conception supports the major population of one of Seychelles’ endangered endemic bird species, the Seychelles white-eye Zosterops modestus. Were introduced predators to be eliminated and habitat rehabilitation to be implemented, both of these smaller islands could support small insectivorous bird species such as Seychelles warbler and white-eye. While populations would necessarily be smaller than those on larger islands, the founding of new populations would in itself reduce the likelihood of extinction of these species. Both Therese and Conception support a number of endemic plant species absent on much larger islands because they are positioned relatively close to Mahé, the largest island of the archipelago and one of the islands having the greatest endemic biodiversity. While limited resources available to conservation might be better directed at medium-sized islands with large plateau areas that could support a number of endemic species, under appropriate management regimes even the smailest of the islands surveyed could have a role in the conservation of Seychelles endemic land birds. 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CS ts ir a, : 2 a. ie Hasta ; ye non Be in i ~fomleghiit! ey \j PLATES 270 Plate 1. Major habitat types on smaller islands of the granitic Seychelles: a Coastal plateau dominated by coconut plantation, North Island; 6 Coconut plantation (with introduced ornamental palm Latania sp. In foreground); c Abandoned coconut plantation, showing death of many mature palms and regrowth of dense mixed scrub beneath, Marianne Island; d View of native-dominated lowland forest, Curieuse. Endemic Pandanus multispicatus and palm Phoenicophorium borsigianum in foreground; e View of native-dominated lowland forest and ruins of leprosarium, Curieuse. Trees are takamaka Calophyllum inophyllum; f Death of takamaka trees caused by takamaka wilt disease, North Island. Invasive alien tree A/stonia macrophylla in foreground. Photos © BirdLife Seychelles. Plate 2. Major habitat types on smaller islands of the granitic Seychelles: a Open glacis with introduced shrub cocoplum Chrysobalanus icaco, Félicité with views to Grande Soeur (right) and Petite Soeur (left); 6 Rocky shore with coastal “beach crest’ vegetation, predominantly Scaevola sericea, Conception; c Beach crest vegetation on Denis Island: sedges and /pomoea pes-caprae on seaward side, with Suriana and Scaevola behind; @ Freshwater marsh with 7ypha and grazing cattle, North Island; e Tidal marsh with dense growth of Acrostichum sp., Thérése; f Dense growth of young coconuts beneath abandoned plantation, Denis; g Carica papaya growing under abandoned coconut plantation, Bird Island. Photos © Birdlife Seychelles. 272 Plate 3. Endangered endemic birds of the granitic Seychelles with potential for inter- island translocations: a Seychelles magpie-robin Copsychus sechellarum; b Seychelles fody Foudia sechellarum; c Seychelles black paradise flycatcher Terpsiphone corvina, female bird; d Seychelles warbler Acrocephalus sechellensis; e Seychelles white-eye Zosterops modestus. Photos a—d © BirdLife Seychelles, photo e © Dr Dave Currie. = ONIAN INSTITUTION LIBRARIES ATOU RESEARCH EU A 3 9088 01375 3975 NO. 495 PAGES PREBA CEE sccsciccsssccccosescedachensuesccsastoss cousseceswscssesscoesdounscevessue tie tees accor taco Cone ee eR C EET Michael J. Hill Vv INTRODUCTION AND METHOODG..............cccccccsssssssessssscccesssscccsess Michael J. Hill, Terence M. Vel 1 Kathryn J. Holm and Nirmal J. Shah BERD asiceteccedicvesecvssscaescescessivesecssbuasessccaassecsavsoccscecceecsesavsavsuccucesevestaseverese Michael J. Hill, Terence M. Vel, 11 Kathryn J. Holm, Steven J. Parr and Nirmal J. Shah CONCEPTION eiccciccecosose ss rivarros eae e eee EET Michael J. Hill, Terence M. Vel, 31 Kathryn J. Holm, Steven J. Parr and Nirmal J. Shah COUSIN Wiassssseccscsccésavncccceacanccestvccdactssebesusnesbavenrnetscesauscecsecsatceseveusstecterees Michael J. Hill, Terence M. Vel, 49 Kathryn J. Holm, Steven J. Parr and Nirmal J. Shah CURIE US Biveiccsdicckicissscscsecscissvasdsssctcasecouscsosesacccecscecsvescecnsecssesesesescteoviee Michael J. Hill, Terence M. Vel, 73 Steven J. Parr and Nirmal J. Shah DDE NUS i sicscbccsecedececteasessdeastaucasceecccascascesducedcsteccvssenkccsstoteceucescsenevesssoosertere Michael J. Hill, Terence M. Vel, 97 Kathryn J. Holm, Steven J. Parr and Nirmal J. Shah 131) Cl ( 0) Hb Deeeeemnne nee aire inernen Mn eee ec et cen eaion Michael J. Hill, David R. Currie, 119 Terence M. Vel and Rodney Fanchette GRANDE SOEUR vscsssiccecesccccscccsssecsdcscsssesecaceveszecestesssvereisgescoten eeeeeeene Michael J. Hill, Terence M. Vel, 141 Steven J. Parr and Nirmal J. Shah IVIPAIRITAININE i esscccsdeceosevsscasssctececsoocceccedossccssuvsecesessedsencsessseocecncoesccteteeteaterren: Michael J. Hill, Pat Matyot, 157 Terence M. Vel, Steven J. Parr and Nirmal J. Shah INOR DE evccccéscsececkcsvancesssecssscnsets seucccevsscctsseecesavcesusssacestoeeee sevawsssoseneoreeesee Michael J. Hill, Terence M. Vel, 177 Kathryn J. Holm, Steven J. Parr and Nirmal J. Shah THERESE? 33.3 2.Acs..cshisiisn bien chae eeneee e e Michael J. Hill, Terence M. Vel, 201 Kathryn J. Holm, Steven J. Parr and Nirmal J. Shah SPIDERS (ARANEAE) COLLECTED 1999-2000...............cccsssccssssscsssccsseccesscsees Michael I. Saaristo, 221 Michael J. Hill ASSESSING CONSERVATION VALUE OF ISLANDS IN THE INNER SEYCHELLES wisc.cccscscscesescescesccsseveccsssscsctsssesdsonessestotsseseuseccssevsnccsesess Michael J. Hill 231 IRREE ERENCES ticsccssececcecseccecccessusecsccocsosecessesaccdecssnceescessoceccvssscsceesuascueeteroreneasoseocttesensuuseceswsuccescatstceseeaereeeee 255 PULA TES sesscccsscssccvcscccsccoesessesccsdacecossevssseesoeeveosccsecosvaesessceossessesssoveccoustocssssusssecssessancetesvatectsatecsaccetseunsesesucentees: 269 ISSUED BY NATIONAL MUSEUM OF NATURAL HISTORY SMITHSONIAN INSTITUTION WASHINGTON, D.C., U.S.A. JULY 2002