African elephant age determination from teeth: validation from known individuals

Abstract

We assess tooth-based age criteria for African elephants developed by Laws in relation to known-aged individuals in the Amboseli elephant population. Laws's technique remains a robust and useful mechanism for age determination, although we suggest revisions to the oldest age categories. Blind age assignment to jaws of unknown sex using the Laws criteria resulted in misclassification of M4 and M5; measures overlapped too much to differentiate these teeth by sex. Sexes could be reliably distinguished after age 30 or XIX in tooth category by two measures: mandible thickness and width of the ascending ramus, but individuals of the same known age differed in tooth wear and progression rates. Such variation needs to be incorporated in the error assigned to tooth age categories. Ages at death of found jaws (n = 266) were similar to results of survival analysis from all demographic data (n = 2455), excluding calves whose jaws decompose because of weathering and scavengers. Jaw-based models of age at death need correction for the inability to detect this early mortality, which artificially extends mean longevity by up to 6 years.