A Comparison of Three Ageing Techniques for Feral Pigs From Subalpine and Semi-Arid Habitats.

Abstract

Three ageing techniques were tested on samples of wild-caught feral pigs from subalpine (n =35) and semi-arid (n =64) areas in eastern Australia, and on a sample of known-age captive feral pigs reared from stock from semi-arid areas (n =15). Techniques employed were based on morphometric relationships, patterns of tooth eruption and wear, and counts of cementum lines in permanent incisors. Cyclic seasonal conditions led to apparently annular cementum line deposition for pigs from the subalpine area. In contrast, stochastic variation in seasonal conditions led to irregular cementum line deposition in pigs from the semi-arid area and captive-reared pigs of semi-arid stock. On the assumption that cementum lines are annular in pigs from the subalpine site, patterns of tooth eruption and wear and morphometrics returned reasonably accurate age estimates, the former being more precise. Patterns of tooth eruption and wear returned reasonably accurate age estimates for known-age captivereared pigs, whereas morphometrics gave increasing underestimates of age for progressively older pigs. On the assumption that patterns of tooth eruption and wear return similarly accurate age estimates for wild pigs from the semi-arid area, morphometrics again underestimated true age. A correction to the morphometric technique to improve its accuracy for semi-arid areas is given.