NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. The Mountain Pygmy-possum, Burramys parvus, is a predominantly terrestrial marsupial that has a highly restricted distribution in south-east New South Wales and north-eastern Victoria. The Mountain Pygmy-possum is the only Australian mammal limited in its distribution to alpine and sub-alpine regions and in NSW it occurs in Kosciuszko National Park at altitudes above 1600m.
2. The preferred habitat of the Mountain Pygmy-possum is boulderfield-heath, formed below mountain peaks or in gullies by periglacial weathering processes. During winter, the boulderfield-heath creates a sub-nivean space that has a relatively humid and warm microclimate compared to the above snow environment. In the absence of boulderfields, pygmy-possums will occupy areas where there is Mountain Plum-pine, Podocarpus lawrencei, heath growing over rocks. Suitable habitat patches are often small and isolated, with up to 3km between some boulderfields (Mansergh and Broome 1994). However, there is considerable movement of pygmy-possums between patches, mainly by males and juveniles.
3. In 1986, the extent of Mountain Pygmy-possum habitat in NSW was assessed from aerial photographs and estimated to be approximately 8km2 (Caughley 1986). A better understanding of Mountain Pygmy-possum habitat requirements has been determined over the past 3 years. Preferred habitat is now believed to cover an extent of less than 4km2 in NSW, and may support fewer than 500 adults (Broome et al., in prep.).
4. The Mountain Pygmy-possum is threatened in NSW by the loss, degradation and fragmentation of habitat. Two of the four main sub-populations are located within ski resort areas. Past management practices by the resorts have led to direct loss of habitat and alteration of vegetation. Winter activities such as snow grooming may directly affect Mountain Pygmy-possums by compacting the sub-nivean space and disturbing pygmy-possums during hibernation. Fragmentation of habitat by roads and resort buildings affects recruitment to the population, particularly by inhibiting the dispersal of male and juvenile individuals between habitat patches.
5. Predation by the Red Fox Vulpes vulpes, and Feral Cat Felis catus, threatens the survival of the species. The abundance of these exotic predators is enhanced by the presence of ski resorts, as both species scavenge refuse during winter (Bubela 1995).
6. The Mountain Pygmy-possum does not occur below the winter snowline and its range has decreased over geological time with the retreating snowline. Survival and recruitment of NSW Mountain Pygmy-possums is highly dependent on the duration of snow cover. Survival and recruitment is low during years of very short or very long snow cover (Broome, in prep.). There is evidence of a decline over the last 30 years (1970-1996) in the number of snow events, (days on which snow falls), and a suggested shortening of the snow season, which is correlated with warming regional temperatures (Davis 1998). Given that the extent and duration of snow cover is likely to decrease with the predicted effects of global warming (Whetton et al. 1996, Whetton 1998), the Mountain Pygmy-possum population is likely to continue declining in the foreseeable future.
7. Mountain Pygmy-possums are also threatened in NSW by the likelihood of increased competition with and predation by other alpine and sub-alpine small mammals as snow cover duration and extent declines. The principal food for Mountain Pygmy-possums is Bogong moths and the seeds and fruit of the Mountain Plum-pine. These food items are also likely to decrease in abundance due to global warming. Podocarpus lawrencei and several other alpine plant species are fire-sensitive and alteration to the local fire regime such as increased frequency of burning would affect Mountain Pygmy-possum habitat.
8. In view of the above points, the Scientific Committee is of the opinion that the Mountain Pygmy-possum is likely to become extinct in nature in NSW unless the circumstances and factors threatening its survival or evolutionary development cease to operate.
Proposed Gazettal date: 16/03/01
Exhibition period: 16/03/01 - 20/04/01
Broome, L.S. (in prep.). Survival and recruitment of the Mountain Pygmy-possum Burramys parvus Broom in relation to snow cover in the Snowy Mountains, Australia.
Broome, L.S., Green, K. and Walter, M.A. (in prep.). Re-assessment of Burramys parvus population size and distribution of habitat in Kosciusko National Park.
Bubela, T.M. (1995). Social effects of sterilising free-ranging vixens (Vulpes vulpes L.) in sub-alpine Australia. Ph.D Dissertation, University of Sydney, NSW.
Caughley, J. (1986). Distribution and abundance of the Mountain Pygmy-possum, Burramys parvus Broom, in Kosciusko National Park. Australian Wildlife Research 13, 507-17.
Davis, C. J. (1998). Meteorological aspects of snow. Pp. 3-34 In: Green, K (ed.), Snow: a Natural History; an Uncertain Future. Australian Alps Liaison Committee, Canberra. Surrey Beatty, Sydney.
Mansergh, I. and Broome, L.S. (1994). The Mountain Pygmy-possum of the Australian Alps. University of New South Wales Press, Kensington, NSW.
Whetton, P. (1998). Climate change impacts on the spatial extent of snow cover in the Australian Alps. Pp. 195-206 In Green, K. (ed), Snow: a Natural History; an Uncertain Future. Australian Alps Liaison Committee, Canberra. Surrey Beatty, Sydney.
Whetton, P. H., Haylock, M. R. and Galloway, R. (1996). Climate change and snow cover duration in the Australian Alps. Climatic Change 32: 447-79.