Threatened Species - The Kangaroo Island Dunnart - Rare or Elusive?
Background
The Kangaroo Island Dunnart Sminthopsis aitkeni is a Nationally Endangered species (Environment Protection and Biodiversity Conservation Act 1999) that is endemic to Kangaroo Island. This species, the only species of dunnart occurring on Kangaroo Island weighs 20-25 gm, but is distinguished from similar looking species by the dark sooty colour of the dorsal fur and by its slender pointed muzzle (Strahan 1995). The tail is always longer than the body length, and is never incrassated (Strahan 1995). The Kangaroo Island Dunnart was first recorded in 1969 when a dog captured two animals as they escaped from recently felled yakka. Over the next ten years another four animals were recorded from three other locations (see map for past records). See Information Sheet (350Kb PDF) Another 10 years passed before the next capture in 1990 during the Biological Survey of Kangaroo Island. Only one animal was captured despite over 3,000 pitfall and 8,000 Elliot trap nights (Robinson and Armstrong 1999). Another intensive four-week survey in 1996 failed to capture any dunnarts (Herbert 1996). A breakthrough came in 1997 when a dunnart was captured at a site established by Ranger staff in Flinders Chase, followed by another in 1998. Then in 1999 a record came from the 1990 Biological Survey site, taking the total to just ten! Survey and Research ProjectIn 1996 the Kangaroo Island dunnart was listed as Nationally Endangered (Maxwell et al. 1996). In October 1999 an 18 month survey and research project funded by Environment Australia was initiated.
TrappingA total of 46 sites were surveyed during this project, with over 13,700 pitfall trap-nights and 8,900 Elliott trap-nights carried out. This resulted in 22 dunnarts being captured from six locations, including 4 new locations (see map). All locations occurred within Flinders Chase. Fifteen of the dunnarts captured were juveniles or sub-adults, and no adult females were captured. All captures occurred between January and May. This survey confirmed the rarity of the species. Habitat SelectionCapture sites show high habitat variability owing to structural, floristic and fire history differences. However, with few known 'dunnart' sites it is difficult to identify habitat preferences. Home Range and Micro-habitat Selection
Two male and two female dunnarts were fitted with radio-transmitters on cable-tie collars and tracked for three to nine days. The limited data obtained provided a small insight into the movements and home range size of the dunnarts. Observed range length was 169m and 185m for the females, and 289m and 380m for the males. Home range size estimates ranged from 0.34 ha to 2.32 ha, with overlap between the males and females. Further studies are required to better understand temporal and spatial use of habitat, however, this preliminary data assists with determining sizes of dunnart management areas around the sites where they occur. Radio tracking also allowed day shelters to be located. The dunnarts were found under yakka in dense litter, under banksias, and in a burrow. DietA total of 25 scats were collected from the dunnarts that were captured, and analysis of the contents revealed that spiders and ants were the most common food groups, occurring in 59% and 56% of scats respectively. Beetles and scorpions were also recorded in over one third of the scats, with grasshoppers and centipedes recorded in less than 5% of scats. There was little difference between prey items consumed by males and females. The recorded diet is consistent with dasyurids generally. Breeding seasonThe timing of the breeding season was estimated based on the known growth rates of the Common Dunnart S. murina. The capture of two cohorts of juveniles at one site suggested that, like the Common Dunnart, the Kangaroo Island Dunnart is polyoestrous. The data suggests that mating at this site occurred around late September, and again around late December, with other dates falling within this period. The lack of captured adult females makes it impossible to determine other aspects of the species breeding biology. See The Distribution and Ecology of the Kangaroo Island Dunnart Final Report (2Mb PDF) Rare or Elusive?Low capture rates suggest that this dunnart is rare. It may also have a very patchy distribution, reducing our chances of catching it - so it is also elusive. Future DirectionsFuture management,research, and monitoring directions will focus on protecting the known populations, particularly from wildfire, undertaking further survey work to clarify the distribution of the species, and continuing population monitoring and research at the major dunnart site to determine why the species is so rarely encountered. Recovery PlanConservation management and research recommendations are listed in the Recovery Plan (Gates 2001). References
Gates, J.A. (2001) Recovery plan for the Kangaroo Island Dunnart Sminthopsis aitkeni: 2002-2006. (Unpublished report. Department for Environment and Heritage: Kingscote). Herbert, T. (1996) Distribution, habitat preference and status of the Kangaroo Island Dunnart Sminthopsis aitkeni. Nature Conservation Society of South Australia. Adelaide. Maxwell, S., Burbidge, A.A. and Morris, K. (eds.)(1996) The 1996 action plan for Australian marsupials and monotremes. Environment Australia. Robinson, A.C. and Armstrong, D.M. (eds) (1999) A biological survey of Kangaroo Island, South Australia, 1989 and 1990. Heritage and Biodiversity Section, Department of Environment, Heritage and Aboriginal Affairs, South Australia) Strahan, R. (Ed.)(1995). 'The mammals of Australia' (Reed Books: Chatswood, NSW). Program SupportAuthor / ContactJody Gates, Regional Ecologist, Department for Environment and Heritage |
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