EStimating the age of wild roch-allabies by dental radiography: a basis for quantifying the age structure of a discrete colony of Petrogale assimilis

Abstract

The teeth of rock-wallabies from a wild population of Petrogale assimilis at 'Black Rock' in north Queensland were radiographed in the field at intervals over two years in order to estimate their age. The gross morphology of the dentition conesponds with that of browsing macropodids. The pattern of tooth eruption conforms to the general macropodid model. Although P. assimilis reach sexual maturity at 18-24 months, full molar eruption apparently does not occur until individuals are at least seven years old. The plane of the occlusal surface is only slightly curved. Most of the cheek teeth are in occlusion at once. In all, 70% of wallabies examined at 'Black Rock' had a full complement of cheek teeth. P4 is well developed and rarely lost. These attributes collectively suggest that the small amount of mesial movement of the molars constitutes advanced mesial drift rather than true molar progression. Molar eruption is a reliable index of age until full eruption occurs. Molar movement is likely to be of only limited use in estimating the age of animals with a full complement of cheek teeth. The age structure of the colony at 'Black Rock' suggests a low rate of recruitment into the adult population of P. assirnilis for most of the 1980s.