Estimating the age structure of a population of brushtail possums (Trichosurus vulpecula) by comparing tooth wear and cementum lines

Abstract

We used cementum lines from a sample of possums to calibrate tooth wear patterns in free-ranging common brushtail possums (Trichosurus vulpecula) to estimate of the age structure of a wild population of the species living at the Perth Zoo, Western Australia. We assessed patterns of tooth wear and incremental cementum lines in teeth extracted from 40 possums via necropsy. Rank regression for non-parametric data revealed a weak relationship between the number of cementum lines per tooth (y), which was assumed to correspond to the age of the possums (in years), and tooth wear (males: age = 0.51x + 3.4, r2 = 0.098, n = 27; females: age = 1.17x + 0.35, r2 = 0.345, n = 45). We used these relationships and the tooth wear pattern of 149 live possums caught at Perth Zoo to develop an estimate of the age structure of the population. Most (63.1%) possums were between 4 and 6 years of age. Very few young (1–2 years) or old (6–8 years) possums were caught at Perth Zoo. These results yielded an approximate age distribution for possums within Perth Zoo and should be used with caution because the relationship between the number of cementum lines and tooth wear was weak.