The Mountain pygmy is a rather small marsupial, meanwhile being the largest pygmy-possum. For a long period of time, all information about the Mountain pygmy possum came from fossils, until the animal was discovered in the Australian Alps in 1966. The quality, dense fur of the animal is grey on the back and creamy colored underneath. The long tail and deft front feet allow the possum to easily collect food. The back feet are strong and powerful, helping the animal in gripping. In addition, due to its large front teeth, the Mountain pygmy skillfully cracks seeds. During the breeding season, the fur of male individuals attains more fawn-orange coloration.
The Mountain pygmy is the only Australian mammal, found exclusively in alpine habitat. This marsupial occupies the Alps of Victoria and New South Wales (Australia), where the Mountain pygmy lives among rock screes and boulder fields at elevations of 1,500 - 2,228 meters. In Victoria, Mountain pygmy possum mainly occurs atop the Mount Bogong, Mount Loch and Mount Higginbotham. In New South Wales, this animal primarily inhabits mountain ranges of Kosciusko National Park, namely, Mount Townsend, Mount Kosciusko and Mount Blue Cow. Preferred habitat of this possum is mountain plum-pine heathland with adjacent alpine communities.
The Mountain pygmy possum is a nocturnal animal, spending its daytime hours curled in a ball in order to conserve heat. This marsupial is a rather secretive, but calm and social animal. It does not appear to compete for space or food with other animals. Grooming is a common activity in this species. Mountain pygmy possums have been observed running over the backs of one another without disturbing each other. When distressed, mountain pygmy possums are known to give out low guttural calls. Despite of being excellent climbers, these possums are primarily terrestrial, spending most of their time on the ground, as opposed to most possums. From March-April to September-October, they undergo hibernation as a result of living at high altitudes. Meanwhile, these possums do not hibernate for the entire winter: before hibernating, they usually collect winter food supply, then wake up every few days to eat.
Mountain pygmy possums are omnivores. During spring and summer, these animals feed upon protein rich Bogong moths, allowing them to accumulate fat. Their diet includes various insects, seeds as well as fruit of Mountain Plum Pine, Rambling Bramble, Snow Beard-heath and other plants.
These animals have a polygynous mating system, where each male mates with a number of females. Mountain pygmy possums breed in October-November, during the Austral spring, when males travel to higher elevations to get to nesting sites of females, where mating occurs. Females usually give birth to three-four babies in a litter, after a gestation period of 14-16 days. Newborn young are altricial. They immediately climb into the pouch of their mother, remaining there for 4 - 5 weeks. Coming out of the pouch, they spend additional 5 weeks in the nest, feeding upon maternal milk. Weaning occurs by 10 weeks old, after which juvenile males are usually driven out of the nest. Sexual maturity is reached at 1 year old.
Due to their small and highly scattered range, hardly occupying more than 7 sq. km, these endangered possums live in fragmented populations, facing a number of threats. One of these threats is loss of their natural habitat due to global warming, which causes increased temperatures and decreased snow cover. Development of the ski industry within their range is another big threat, being a result of restrictions of their habitat requirements. The Mountain pygmy possums are hunted by local predators such as the red fox and feral cats. On the other hand, they are affected by many factors, threatening local populations of Bogong moth (their primary food source) such as pesticide use within their breeding grounds. In addition, Mountain pygmy possums have suffered from bushfires, which occurred in 2003, damaging a large area of their range.
According to the IUCN Red List, the total population size of the Mountain pygmy possum is estimated to approximately 1,700 adult females and 550 adult males. Numbers of this species are decreasing today, and the animals are classified as Critically Endangered (CR) on the IUCN Red List.