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

Abstract

Life-history attributes are described for the mountain brushtail possum (Trichosurus caninus) 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 : 1) 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 : 1) 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.