Living at high altitude, the mountain pygmy possum hibernates during the winter months from May to September. To survive hibernation these possums put on large amounts of fat and then roll into a ball to conserve heat. During the winter, individuals will occasionally rise from torpor to feed on stored seeds and berries (2). The mountain pygmy possum is the only marsupial to store food in a cache. Possums are nocturnal and during the 'active season', which runs from October to April, will feed primarily on the high energy Bogong moth (Agrotis infusa) which arrives in the Australian Alps in large numbers in the summer months to breed (2). As numbers of these moths decrease, the pygmy possum switches its diet to seeds and berries, prising open the hard cases with agile fingers (2). Females occupy overlapping home ranges, whereas males disperse from their natal range and are more nomadic (2). Breeding coincides with the retreat of the snow line and the reappearance of Bogong moths in the region. Females give birth to 4 young, which are born in an immature stage of development (3). The young make their way to the pouch and attach to one of four teats (2), leaving the pouch after a few weeks to stay in a nest constructed from grasses (3). Young pygmy possums are independent after 9 weeks but females only have one litter a year due to the need to store up fat for winter hibernation (3). Mountain pygmy possums can live for as long as 12 years (2).