An unusual marsupial that was first described as a fossil species, then discovered to be still alive and living at the top of mountains in Australia.

Statistics
About 110mm long, with a 140mm tail. Males are slightly larger than females.

Physical description
A small, mouse-like marsupial with a long, prehensile tail. It is covered in soft greyish fur, paler on the belly and with a slightly darker rump and nape of neck. Males become slightly more orange in the breeding season. It has very manipulative front feet for gathering food; and gripping hind feet. Its front teeth are used to scrape at food, and they have specialised premolar teeth for cracking and dehusking seeds.

Distribution
South-eastern Australia

Habitat
Montane heathland and high altitude rocky areas from 1400-2230m.

Diet
Bogong moths in the spring and summer, fruits and seeds in the autumn and winter.

Behaviour
Females are quite sociable, sharing a daytime nest site (probably with related females), and dispersing at night to forage. Males are solitary, and move over large areas, being repelled by unreceptive females whose ranges they cross. This leads to males being less likely than females to survive in a given year as they are more exposed to predators, and do not share body heat during the winter. From May to September, during the winter, the animals become inactive, and remain in the nest, feeding from stored seeds and nuts and living off fat reserves.

Reproduction
Mating takes place between late September and mid October. After a 13-16 day gestation period, a litter of four very small young is usually produced. There are only four teats, so if more than four are produced then the last one to reach the pouch cannot find a nipple and dies. The young remain in the pouch for 30 days, and then they begin to be weaned, staying in the nest or following the mother on foraging trips for the next 30-35 days. They are fully independent after 65 days, and become sexually mature at 1 year old, although they are not able to build up enough fat to survive a winter on their own until their second year, when males are ejected from their mothers' territory. Survival rates through the first winter are low for both sexes.

Conservation status
Endangered with around 2,600 adults remaining. The habitat of this animal coincides exactly with that of ski resorts in Australia, leading to habitat disturbance and conflict with human interests.

Notes
The mountain pygmy possum was first described in 1896 from fossils and was assumed to be extinct. In 1960s some ski lodge residents found a small mammal frequently took residence in their lodge for food and shelter, and in 1966 a specimen was taken to a museum for identification. It was discovered to be a living representative of the fossil species! However, it was assumed that the animal must have come in with wood supplies and could not live at that altitude, and so, despite trapping efforts in the lower forests, no more specimens were found until 1970 when it was realised that these animals really did inhabit the rocky heathland of the mountaintops.