Demography and condition of bushtail possum : A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Applied Science at Lincoln University

Abstract

Necropsy data were collected from brushtail possum (Trichosurus vulpecula) populations in forest habitat at Waihaha, and in farm habitat at Hohotaka, both in the central North Island of New Zealand. A major control operation reduced the Hohotaka population by 89% in 1988, and low population numbers were maintained thereafter by smaller annual operations. Finite rates of increase, calculated from birth and mortality data, were approximately unity for all three populations. Possums at Waihaha were in better morphological and physiological condition, and had lower birth and mortality rates and an older age structure, than those at Hohotaka. The contribution of spring breeding to the population was higher at Waihaha and Hohotaka post-poisoning than at Hohotaka pre-poisoning. After poisoning at Hohotaka, a morphological index of survivors' condition increased, but a fat-related index declined. Birth and mortality rates increased, male and female age structures became younger, and adult sex ratios became increasingly male biased (due in part to male-biased birth ratios). The usefulness of these results for predicting the demographic response of possum populations to sustained control of this pest in other areas is discussed.