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
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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
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HW
HW
PG, HW, HSc
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Cu Only in gardens
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