No. 107 OCTOBER 1991 MUSEUM OF VICTORIA »THE Vk T Tasmanian Naturalist ISSN 0819-6826 POSTAL ADDRESS: G.P.O. BOX 68A, HOBART 7001 EDITOR: D.G. HIRD SMALL MAMMAL TRAPPING IN SEDGELAND AT McPARTLAN PASS: A NEW LOCATION FOR Mastacomys fuscus by Michael M Driessen and Michael D Comfort Department of Parks, Wildlife and Heritage We present the results of small mammal trapping at McPartlan Pass over three nights 6 May to 8 May 1991. The area was trapped in order to determine the presence of small mammals, particularly the broad-toothed rat, Mastacomys fuscus , before the area was to be burnt to study the effects of fire on a high fuel load sedgeland. McPartlan Pass (146° 12'E 42° 51'S) is located in southwest Tasmania within the Tasmanian Wilderness World Heritage Area, and is approximately 55 km west of Maydena on the Gordon River Road. Sedgeland was the dominant vegetation where traps were set. For the purposes of this study the sedgeland was subdivided into four community types based on Jarman et al. (1988). A description of these communities is given in table 1. A total of 96 Elliot traps were used on the first night and an additional 10 traps were added in layered blanket moor vegetation on the following 2 nights. In all there was a total of 308 trap nights. Traps were placed in plastic bags and baited with a mixture of peanut butter and rolled oats. Traps were placed in four lines covering the four main vegetation types in the area. The results of trapping in each vegetation type at McPartlan Pass are given in Table2. Inall there werea total of 18captures. The velvet-furred rat r Rattuslutreolus f was the most frequently captured species accounting for 67% of captures. The majority (83%) of captures of this species were in the layered blanket moor. The swamp antechinus, Antechinus minimus , was the next most commonly trapped species (22%). It was mostly caught in the copses. The single capture of A. minimus in the standard peat was only about 10 m away from a wet copse. There Each author is responsible for the opinions and facts expressed in his or her article— EDITOR. 2 The Tasmanian Naturalist October 1991 Standard Peat: This is the dominant community present at McPartlan Pass. The most common species up to 100 cm high are the sedges, Gymnoshoenus sphaerocephalus (buttongrass), Lepidosperma filiforme, Leptocarpus tenax, Restio complanatus and the swamp melaleuca, Melaleuca squarnea. The tea-tree, Leptospermum nitidum, and pink swamp heath, Sprengelia incarmta, are emergent shrubs up to 150 cm high. Vegetation cover ranges from 40% to 70% but tends towards the lower end of the range. Copse: Both dry and wet copses occur as scattered small islands throughout the standard peat moorland at McPartlan Pass. The copses are normally located on areas of raised ground. The communities are usually dominated by the tea-tree, Leptospermum scoparium, up to 200 cm high. Some stands are dominated by banksia, Banksia marginata, which reaches 300 cm in height. G. sphaerocephalus , L. nitidum, S. incarnata and M. squarnea are sub-dominant up to 150 cm high. Vegetation cover in this community is high. Layered Blanket Moor: Within the study area this community is only present along roads and drainage lines (both natural and artificial). G. sphaerocephalus forms a dense cover up to 100 cm high wi th Leptospermum scoparium occasionally forming a dense cover up to 250 cm high. In some areas cutting grass, Gahnia grandis , also forms a dense cover up to 250 cm high. Other common species include L. nitidum, S. incarnata and M. squarnea. Dry Copse with Eucalypts: This vegetation type occurred along the eastern boundary of the standard peat at McPartlan Pass. The community is dominated by a sparse overstorey of Smithton peppermint, Eucalyptus nitida, up to 8 m high with a dense shrubby understorey up to 3 m high dominated by L. scoparium. G. sphaerocephalus tussocks occur towards the edge of this community where it borders the adjacent moorland. L. nitidum, S. incarnata and M. squarnea are also present in the shrub layer. Beneath the tea-tree stands there is little development of vegetation. Table 1 The communities in the study area at McPartlan Pass was one capture each of M.fuscus and the long-tailed mouse, Pseudomys higginsi, in layered blanket moor and dry copse with eucalypts respectively. The results indicated that within sedgeland habitat the differences in vegetation were reflected in the distribution of small mammals. Copses and in particular layered blanket moor appeared to support higher numbers of animals than the standard peat. Presumably this is because of the better cover afforded by these communities. Cover has been identified as an important habitat component of R. lutreolus (Hocking 1975, Murray 1980, Norton 1983, Driessen 1987) and also the The Tasmanian Naturalist October 1991 3 Vegetation Type Trap Nights R1 Am Mf Ph Total Standard Peat 132 1 (0.8) 1 (0.8) 0 (0.0) 0 (0.0) 2(1.5) Layered Blanket Moor 53 10 (18.9) 0 (0.0) 1 (1.9) 0 (0.0) 11 (20.8) Copse 48 1(2.1) 3 (6.3) 0 (0.0) 0 (0.0) 4 (8.3) Dry Copse with Eucalypts 75 0 (0.0) 0 (0.0) 0 (0.0) 1 (1.3) 1 (1.3) Total 308 12 (3.9) 4(1.3) 1 (0.3) 1 (0.3) 18 (5.8) Table 2 Total number of small mammal captures by vegetation type at McPartlan Pass. Values in parentheses are numbers of captures per 100 trap nights. R1 =Rattus lutreolus, Am=Antechinus minimus , Mf =Mastacomys fuscus, Ph =Pseudomys higginsi. mainland subspecies (Braithwaite et al 1978). Similarly Green (1972) noted that A. minimus was usually caught in runways beneath dense vegetation. The most interesting feature of the results is the trapping of a female M. fuscus which is one of the most rarely recorded small mammal species in Tasmania (Rounsevell et al. in press). With the aid of two blunt probes the identity of this species was determined by examination of its teeth. This confirmed the presence of the broad molars which are characteristic of this species (Thomas 1882). The molars were also compared with those of a R. lutreolus trapped nearby. Faeces collected from the M. fuscus were pale green, similar to that described by Green (1968). Green believed that the faeces of M. fuscus , could be distinguished from those of R. lutreolus on the basis of colour. He described the colour of faeces belonging to R. lutreolus as being brown or greyish in colour. At McPartlan Pass there were no captures of R. lutreolus with green faeces, all except one was chocolate brown, the exception being red. Assuming faecal colouration is a reliable indicator of M. fuscus presence, then field observations suggest that the species was spread over a wider area than that indicated by trapping. However, in all cases the faeces were never far from areas with adequate cover such as layered blanket moors and copses. At McPartlan Pass M. fuscus was trapped in layered blanket moor vegetation alongside a 50 cm wide drainage line. Whilst much of the McPartlan Pass area had last been burnt 19 years ago (J. Marsden-Smedley, Project Officer, Department of Parks Wildlife and Heritage), it was obvious by the amount of growth of the 4 The Tasmanian Naturalist October 1991 buttongrass that the layered blanket moor was subject to less firing than the surrounding standard peat. These results concur with the observations of Green (1968), Hocking and Guiler (1983), Taylor et al. (1985) and Taylor and Comfort (1991) that the absence of fire is important in determining M. fuscus habitat. This has important implictions for the management of M. fuscus as fire is a common tool for management of this species' habitat in Tasmania, including the World Heritage Area. Whilst there is a need, in some cases for firing to reduce the risk of loss of life and property, and to manage some threatened species such as the orange bellied parrot ( Neopherm chrysogaster), due consideration should be given to rare, less well known and lower profile species such as M. fuscus. ACKNOWLED GEMENTS Thanks go to Jon Marsden-Smedley and Jennie Whinam for vegetation descriptions, and Karen Wilson for assistance with trapping. REFERENCES Braithwaite, R.W., Cockburn, A. and Lee, A.K. (1978). Resource partitioning by small mammals in lowland heath communities of southeastern Australia. Aust. ]. ofEcol. 3:109-127. Driessen, M.M. (1987). A comparative dietary study of two native, sympatric murids. Hons. Thesis, University of Tasmania. Green, R.H. (1968). The murids and small dasyurids in Tasmania. Parts 3 and 4. Rec. Queen. Vic. Mus. (Launceston) 32:1-19. Green, R.H. (1972). The murids and small dasyurids in Tasmania. Parts 5,6 and 7. Rec. Queen. Vic. Mus. (Launceston) 46:1-34. Green, R.H. (1984). The mammal fauna of Ordinance Point area, north-west Tasmania. Rec. Queen Vic. Mus. (Launceston) 84. Hocking, G.H. and Guiler, E.R. (1983). The mammals of the Lower Gordon River region, south-west Tasmania. Aust. Wild. Res. 10:1-23. Hocking, G.J. (1975). Studies on the behaviour and ecology of Antechinus swainsonii. Hons Thesis, University of Tasmania. Jarman, S.J., Kantvilas, G. and Brown, M.J. (1988). Buttongrass Moorland in Tasmania. Tasmanian Forest Research Council Inc. Research Report No.2. Murray, P.A. (1980). Wet sclerophyll habitat utilisation by Tasmanian small mammals. Hons. Thesis, University of Tasmania. Norton, T.W. (1983). Habitat utilisation by small mammals in north eastern Tasmania. Hons. Thesis, University of Tasmania. The Tasmanian Naturalist October 1991 5 Rounsevell, D.E., Taylor, R.J. and Hocking, G.J. (in press). Distribution records of native terrestrial mammals in Tasmania. Wildl. Res. Taylor, R.J., Bryant, S.L., Pemberton, D. and Norton, T.W. (1985). Mammals of the Upper Henty River Region, Western Tasmania. Pap. Proc. R. Soc. Tas. 119:7- 14. Taylor, R.J. and Comfort M.D. (1991). Small terrestrial mammals and bats of Melaleuca and Claytons, south-west Tasmania. Unpubl. Rep., Wilderness Ecosystems Baseline Studies, Department of Parks, Wildlife and Heritage, Tasmania. Thomas, O. (1882). On two new Muridae from Tasmania. Ann Mag. Nat. Hist. Ser 5, Vol.IX, pp. 413-416. DOLPHIN STRANDING DUE TO KILLER WHALES by /. E. Wapstra Department of Parks, Wildlife and Heritage This note describes an episode of behavioural interaction between dolphins and orcas in southern Tasmania, and subsequent human intervention to avoid an anticipated mass dolphin stranding. Large schools of dolphins are often observed in waters around Tasmania. While often mistakenly called porpoises, bottlenosed and common dolphins are the most prevalent species. Both have a cosmopolitan distribution in temperate and tropical waters. Orcas or killer whales also have a world-wide distribution, extending into polar seas, and are probably more common in Tasmanian waters than human sightings indicate. The three species all belong to an order of mammals known as toothed whales or odontoceti. Filter feeding or baleen whales are in the order mysticeti, and marine mammals belonging to these two orders are collectively known as cetaceans. On May 11th 1991 a large school of dolphins was seen hunting mackerel and other seasonally abundant fish in the sou them portion of Adventure Bay, Bruny Island. Estimates of dolphin numbers ranged from 300 to 1000, not an unusual 6 The Tasmanian Naturalist October 1991 school size in Tasmanian waters. Bottlenosed dolphins (Tursiops truncatus) up to 3.5 metres in length were most numerous, with common dolphins (Delphinus delphis) to two metres also present. Dolphins were observed at about 10 a.m. leaping clear of the water and occasionally closely approaching the shore; normal behaviour for actively feeding dolphins. Between 2 and 3 p.m. 20 dolphins suddenly stranded. At about this time a juvenile and three adult female killer whales or orcas (Orcina orca) were first seen on the seaward side of the dolphins. Some observers reported a flurry of activity and surmised that a dolphin may have been taken. Observers returned the stranded animals to deep water where they rejoined the school. For some hours following the stranding the orcas were observed patrolling the mouth of the bay. Dolphins were reported by observers as darting out to sea trying to escape. Although two small groups apparently escaped in this way, most turned back into the confines of the crowded bay. Wildlife authorities were contacted by concerned members of the public during the afternoon and around 5 p.m. two rangers arrived by boat. After consultation with the author, a cetacean biologist, it was decided to intervene in the most humane way available in order to prevent a mass stranding. At first the boat was interposed between the adversaries but this served only in apparently arousing the curiosity of the orcas. Seal crackers were then used and had an immediate response as the orcas moved out some distance, allowing the dolphins an escape route. Neither the orcas nor the dolphins were seen in the immediate area again over following days, with most dolphins having apparently escaped. Although wildlife managers would not usually intervene in a natural predation incident, it was decided that the likelihood of a mass stranding under difficult conditionsand therelativeinaccessibility torescuersand equipment justified the action taken. The seal crackers, normally used to deter seals from fish farms, were not used at a range of less than 50 metres and were considered to be innocuous in the prevailing conditions. Whales and dolphins do not have the exposed eardrums of most other mammals and in this respect are sturdier than seals. Incidents like this are rare. Tasmanian wildlife biologists know of only one proven stranding in local waters; in 1983 three orcas were seen chasing a school of common dolphins at the mouth of Ralphs Bay and next day 15 dolphins were found stranded (McManus et. at., 1984). A stranding of 109 dolphins in the D'Entrecasteaux Channel in 1975 appeared symptomaticof orca pursuit although no direct evidence of this was found at the time (Guiler, 1978). Orcas are adapted for preying on large vertebrate prey with their size, speed and, particularly, their robust muscular jaws with few large, conical teeth. Their cooperative hunting is sophisticated amongst mammals and is often directed towards schooling prey. Seals, fish including large tuna and trevalla, baleen The Tasmanian Naturalist October 1991 7 whales, and large squid are amongst their known prey items (Baker, 1983). Dolphins are known to exhibit aversive behaviour upon hearing orca vocalisations, usually fleeing silently (Evans, 1987). Causes of cetacean standings are both diverse and often difficult to explain. The incident described here indicates that predation by orcas may be implicated in at least some stranding events. REFERENCES Baker, A.N. (1983) Whales and Dolphins of New Zealand and Australia , Victoria University Press, Wellington. Evans, P.G.H. (1987) The Natural History of Whales and Dolphins , Facts on File, New York. Guiler, E.R. (1978) Whale strandings in Tasmania since 1975 with notes on some seal reports, Pap. Proc. R. Soc. Tasm., 112:189-213. McManus, T.J., Wapstra, J.E., Guiler, E.R., Munday, B.L. & Obendorf, D.L. (1984) Cetacean strandings in Tasmania from February 1978 to May 1983, Pap. Proc. R. Soc. Tasm., 118:117-135. Killer Whale (Orcinas orca) 8 The Tasmanian Naturalist October 1991 Bottlenose Dolphin (Tursiops truncatus ) Common Dolphin (Delphinus delphis) Illustrations from Baker (1983), courtesy of Victoria University Press Wellington, New Zealand. _ J) G J) * (A Tasmanian fieCcC 9{aturaCists CCuB Inc. Bulletin No. 264 Supplement to the Tasmanian Naturalist October 1991 The Tasmanian Field Naturalists Club is devoted to the study of all forms of Natural History, and is comprised of both experts and beginners. We cover a wide variety of topics, and we support conservation. Meetings are held on the first Thursday of every month, except January, in the Life Science Building at the University of Tasmania at 7.45 p.m. Outings are usually held the following weekend, meeting outside the main entrance to the Museum, Macquarie Street. The Club's address is GPO Box 68A, Hobart, 7001 and the club contact is Helen Davidson. Programme Thurs. Nov. 7th 7.45p.m. : Louise Gilfedder will be speaking to us on rare and threatened plant and plant communities from remnant grasslands and grassy woodlands. 9 a.m .: Louise will lead us on this outing to the Midlands visiting several sites with high flora conservation value. We won't be doing much walking but bring warm clothes and lunch. 7.45p.m .: A speaker on the wildlife of Antarctica. Our plan for Graham Robinson to speak on the effects of oriental fishing practices on the world albatross population will depend on whether Graham is able to leave the Chattum Islands on time. Reserve speakers are available. Bring a plate for Christmas supper, but no lamingtons this year please (unless you bring a broom as well)! 8 a.m .: A visit to the property of Mr Paul Berry at Collins vale. Paul wishes to transfer title of his land to community groups. We will conduct mammal trapping and exploration of the block's micro-habitats. Leader Don Hird (34 4293). 7.45p.m .: Dr Bob Ellis will speak on aspects of our changing forests. Weekend excursion with accommodation available at Liawenee. Margaret Mollison (28 2720) will take bookings for the accommodation and co-ordinate transport. On Saturday Bob Ellis will lead us to Waddamana and describe its history particularly with reference to forestry. On Saturday evening there will be an address by Professor Bill Jackson, and on Sunday Bill will lead a botanical ramble on the Central Plateau, noting effects of grazing on the vegetation. _ New Members A special welcome to our new members Bob Patterson and Julie Virtue. 1992 Membership fees Club membership fees are due on 1 January 1992. The current rates are adults $15, concession $12 and families $18. Included in a membership fee is the quarterly Bulletin and Tasmanian Naturalist journal. Subscriptions to the Tasmanian Naturalist are also available separately. Within Australia individuals $12 and institutions $16. Overseas individuals $14 and institutions $18. These rates are guaranteed until 31 December 1991, so pay for your membership in advance this year! Mammal survey group Thanks to the Hobart City Council for loan of a key to access the Pipeline Track for a recent survey. Further surveys are planned during the summer months, phone Don Hird for details (34 4293). Sat. Nov. 9th Thurs. Dec. 5th Sat. Dec. 7th Thurs. Feb. 6th Feb. 7-9th Future Outings? There have been several ideas for exotic outings in recent months. These include Betsy Island (just south of South Arm) and Swan Island (just off the north-east corner of Tasmania). To visit Betsy Island we need to use a boat from Hobart. Does any member own a suitable boat who would be willing to use it for a day or weekend? To visit Swan Island we probably would need to hire a bus to travel to the far north-east, and then a short plane hop is available for about $35. There is comfortable accommodation available on Swan Island. On both islands the Club could undertake mammal and plant surveys. Is anyone willing to co-ordinate the organisation of these outings, or does anyone have any inside information? Phone Patti Virtue (34 9478) with your ideas. Federation of Field Naturalists Clubs of Tasmania Phil and Sue Collier were the Club's delegates for the meeting at Golden Valley on 21 and 22 September. The weekend was cold with a snow shower on Saturday morning and thick snow on the Lakes Highway lasting until Sunday. There was an outing to a property high on the slopes of Quamby Bluff on the Saturday with wonderful snowy views of the Western Tiers. On Sunday morning the business meeting was significant for our Club because we agreed to take on the jobs of President and Secretary of the Federation for two years starting in March 1992. We have not nominated people to fill these positions yet. Any interested members may call Phil Collier (29 6597) if they would like to take on one of these jobs. The jobs are not arduous as there are only two meetings of the Federation each year. The meetings are hosted by different Clubs around the State who usually organise outings to their local area which they know well, and may be poorly known by the visitors. For example the meeting in October 1992 may be on King Island hosted by the King Island Club. Organising the outings is not part of the job of being President who is responsible only for a short business meeting during the weekend. Audio tape of Tasmanian birds songs Congratulations to our life member Kelsey Aves who has produced a tape of calls of 64 Tasmanian Birds. These calls have been collected over many years, and have been electronically processed to be suitable for publication. The tape sells for $12 or $10 through the Club. Helen Davidson Members will be sad to hear that our hard-working secretary until this year has been in hospital for several weeks. During this time Helen's mother died. We extend warm sympathy to Helen and wish her a full and speedy recovery. Helen is looking forward to being out in the bush with us again as soon as possible. Helen is our current Bulletin editor. Thanks go to the members of the committee who stepped in at short notice to produce the last Bulletin. President's report Sue and I have just returned from a visit to WA, and again we were enchanted by the wildflowers. During the visit we met with a couple from the Victorian Field Naturalists Club who are responsible for organising outings.' The Victorian Club uses a bus for its outings with two obvious advantages: the group can enjoy company on the journey and the bus is environmentally more friendly than a convoy of cars. The organisers try to estimate the likely attendance before-hand and set a bus fare on that basis. I think that we should consider this idea for our Club. The disadvantage, of course, is that the Club could make a loss on poorly attended outings. Any comments? Phone Phil Collier (29 6597).