The Leadbeater's possum is a small marsupial first collected in 1867, and named after Victorian taxidermist John Leadbeater. This species was believed extinct as a result of land clearing and fires for much of the 19th century. It has persisted, however, and is listed as endangered by the international conservation organisation IUCN.
The Leadbeater's possum has thick grey-brown fur with a dark stripe along the midline of the back, and a paler underside. It has dark patches above and below the large eyes as well as at the base of the large ears. The head-and-body length is 15-17 cm with a long bushy tail of 14.5-18 cm. The adults weigh between 100 g and 170 g.
This possum species has a patchy distribution restricted to the mountain ash forests of Victoria's Central Highlands. There is also a small isolated population in swamp forest in Yellingbo State Nature Reserve in eastern Victoria.
The Leadbeater's possum is mostly confined to mountain ash forests that contain three species of eucalypt, including old hollow trees ('Eucalyptus regnans' and 'E delegatensis'), used for nesting and shelter, and a dense understorey of wattles ('Acacia' spp). The eucalypts and wattles are relied upon for food. These habitat requirements are found most commonly in regenerating or mixed-aged forests.
This nocturnal aboreal marsupial feeds on spiders and insects such as crickets and beetles found under loose eucalypt bark. It also gains much of its sustenance from wattle gum or sap, obtained by cutting into the bark with its teeth. These possums lack the gliding membrane of their sugar glider relatives, and instead run or jump through the dense undergrowth to move between the trees.
Unlike most mammals, this possum has a matriarchal society in which the females actively defend their territory. Breeding pairs are monogamous and may produce two litters of one or two offspring each year. After birth, the underdeveloped young crawl into the mother's pouch where they feed on milk. The female young are weaned at 10 months and the males at 15 months, with full maturity reached at 2 years of age. Young females are driven out of the territory and have a much higher mortality.
The Leadbeater's possum constructs communal nests, which may contain up to eight individuals including the breeding pair, their offspring and unrelated adult males. A single nest made of shredded bark in the hollow of a mountain ash tree is usually built about 6-30 m above the ground near the centre of the 1-3 ha territory.
This particular museum specimen was among the first members of the newly discovered species 'Gymnobelideus leadbeateri' and is therefore the 'holotype'. A holotype, or type specimen, is the individual used to name and classify a new species. The holotype is usually kept in a special museum collection. Although holotypes may not be the most typical or well-preserved specimens, they will never be replaced.