Age Estimation of African Lions Panthera leo by Ratio of Tooth Areas

Paula A White,Dennis Ikanda,Pascal Mesochina,Roberto Cameriere,Luigi Ferrante,Philippe Chardonnet,Benjamin Lee Allen

doi:10.1371/journal.pone.0153648

Abstract

Improved age estimation of African lions Panthera leo is needed to address a number of pressing conservation issues. Here we present a formula for estimating lion age to within six months of known age based on measuring the extent of pulp closure from X-rays, or Ratio Of tooth AReas (ROAR). Derived from measurements taken from lions aged 3–13 years for which exact ages were known, the formula explains 92% of the total variance. The method of calculating the pulp/tooth area ratio, which has been used extensively in forensic science, is novel in the study of lion aging. As a quantifiable measure, ROAR offers improved lion age estimates for population modeling and investigations of age-related mortality, and may assist national and international wildlife authorities in judging compliance with regulatory measures involving age.

Highlights

The African lion Panthera leo is a species for which there is growing need for improved age assessments
Including only Ratio Of tooth AReas (ROAR) in the regression model, the equation describing the known age of lions as a linear function yielded the following linear regression formula which explained 92.3% of total variance (R2 = 0.923): Age ðin yearsÞ 1⁄4 À69:724 ROAR þ 15:781
Using known-aged animals, we have developed a linear regression formula for estimating age of African lions to within six months using ROAR of the PM2 as visualized from digital X-rays and quantified using area measurement software

Summary

Introduction

The African lion Panthera leo is a species for which there is growing need for improved age assessments. Accurate age estimates are essential to demographic studies [5, 6] because age data contribute to understanding population dynamics [7], serve to inform age-specific life-tables [8, 9], and are needed to refine models used to monitor population trends [1]. Improved age estimation of lions can help in determining the potential impacts that different sources of mortality may impart at the population level. Determining the ages of “problem” lions killed as a result of humanwildlife conflicts [10, 11], and the ages of lions represented in the growing trade in lion bones [12], may improve our understanding of the subsequent impacts of these losses on lion populations. While hunting can play a vital role in conservation [13, 14], unsustainable offtake has been implicated in localized population

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