Population Parameters of Two Congeneric Possums, Trichosurus spp., in Norh Eastern New South Wales

Abstract

In adjacent areas in north-eastern New South Wales, T. vulpecula occurs in the open forest and woodland and T. caninus occurs in the closed and tall open forest; both species are found in the pine plantation. T. vulpecula has a single breeding season in autumn when all females 1 y old and older reproduce. The young become independent around 175 days old and disperse at up to 2 y old. Mortality is low (15%) among dependent young but considerably higher among independent dispersing individuals. T. caninus also has a single autumn breeding season. The young become independent around 240 days old but disperse after 18-26 months, females moving before males. Mortality is high (56%) among dependent young but less so among subadults. An adult sex ratio of parity is the result of a higher survival among subadult males than females offsetting the reverse in adults. Some 2-y-old and all 3-y-old females reproduce but a few older females fail to breed in certain years. There is evidence that the high mortality of dependent young and failure of older females to breed is associated with offspring of previous years remaining in the population. Adult males and females appear to form a pair-bond. Population parameters of T. vulpecula described from other areas show considerable variation; this flexibility in population strategy explains the species' success in occupying a diversity of habitats and rapidly colonizing new areas.