Evaluation of the applicability of different age determination methods for estimating age of the endangered African wild dog (Lycaon Pictus)

摘要

African wild dogs (Lycaon pictus) are endangered and their population continues to declinethroughout their range. Given their conservation status, more research focused on theirpopulation dynamics, population growth and age specific mortality is needed and thisrequires reliable estimates of age and age of mortality. Various age determination methodsfrom teeth and skull measurements have been applied in numerous studies and it is fundamentalto test the validity of these methods and their applicability to different species. In thisstudy we assessed the accuracy of estimating chronological age and age class of Africanwild dogs, from dental age measured by (i) counting cementum annuli (ii) pulp cavity/toothwidth ratio, (iii) tooth wear (measured by tooth crown height) (iv) tooth wear (measured bytooth crown width/crown height ratio) (v) tooth weight and (vi) skull measurements (length,width and height). A sample of 29 African wild dog skulls, from opportunistically located carcasseswas analysed. Linear and ordinal regression analysis was done to investigate theperformance of each of the six age determination methods in predicting wild dog chronologicalage and age class. Counting cementum annuli was the most accurate method for estimatingchronological age of wild dogs with a 79% predictive capacity, while pulp cavity/tooth width ratio was also a reliable method with a 68% predictive capacity. Countingcementum annuli and pulp cavity/tooth width ratio were again the most accurate methodsfor separating wild dogs into three age classes (6±24 months; 25±60 months and > 60months), with a McFadden's Pseudo-R2 of 0.705 and 0.412 respectively. The use of thecementum annuli method is recommended when estimating age of wild dogs since it is themost reliable method. However, its use is limited as it requires tooth extraction and shipping,is time consuming and expensive, and is not applicable to living individuals. Pulp cavity/tooth width ratio is a moderately reliable method for estimating both chronological ageand age class. This method gives a balance between accuracy, cost and practicability,therefore it is recommended when precise age estimations are not paramount.