One hundred and forty days in the life of a flyingfox tooth-fairy: Estimating the age of pups using tooth eruption and replacement

Abstract

Age can be an important predictor of an individual's survival or reproductive fate and therefore methods for determining ages of wild animals are of general interest. Bats are assigned to age classes based on morphological measurements (e.g. forearm measurement and tooth wear); or to a chronological year based on annual cementum rings in teeth. However, for infants, only morphometric techniques are available, and individual variation can lead to less reliable predictions of age from these measurements. Here we describe the sequences and timing of tooth emergence and replacement in the Grey-headed Flying-fox (Pteropus poliocephalus) and evaluate the usefulness of the method for ageing pups. Tooth eruption and replacement were assessed visually and at least four stages of growth were described for each permanent tooth for 20 known-age, mother-reared pups that were monitored weekly from October to February. Forearm measurements and mass were also recorded. To test the reliability of the method we aged 30 additional pups. The ages derived from tooth eruption were compared to ages derived from the traditional method using forearm and weight measurements. Our results indicate that the tooth eruption technique is more reliable in estimating age in flying-foxes up to 140 days old. Further research should compare rates and patterns of tooth eruption in hand-raised to mother-raised pups and use a larger sample size to look for any sex differences. Accurate ages for pups will contribute to determining the agespecific mortality rates for this vulnerable species.