A population study of the mountain brushtail possum (Trichosurus caninus) in the central highlands of Victoria

Life-history attributes are described for the mountain brushtail possum (Trichosurus canimus) in mountain ash (Eucalyptus regnans) forest at Cambarville in the central highlands of Victoria, south-eastern Australia. The population was trapped on a regular basis between 1992 and 1995. Population density of T. caninus at Cambarville was high (2.3 animals ha^-1). The adult sex ratio was female-biased (1.4: l) and the age class structure differed between sexes. There were more adult females than males in very old age classes (those animals assigned to Age Classes 7-9 and exceeding an estimated 10 years of age), whereas there were more males in the young adult cohorts (Age Classes 3 and 4). The breeding season was restricted to March-April, when a single young was produced. A second young was not produced if the first was lost. The survival of young from birth to emergence from the pouch showed strong between-year variation (30-80%). Sex ratios at birth were strongly male-biased (average = 2.6: l) but female young were far more likely to survive to advanced back-young stage. Breeding success of females at Cambarville was not influenced by the presence of semi-independent young from a previous year remaining in the natal territory. There was some evidence of senescence in breeding success among females in older age cohorts (Age Classes 7-9) and these animals did not successfully rear young. Many animals were trapped repeatedly at the same place, whereas others ranged over a much wider area (up to 3 ha). There was also considerable overlap between individuals in the spatial location of the areas where they were trapped.