Age Estimation of African Lions <i>Panthera leo</i> by Ratio of Tooth Areas

<div><p>Improved age estimation of African lions <i>Panthera leo</i> 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.</p></div

Plots of Residuals.

<p>Plots of residuals against known ages (left, a) and of known against estimated ages (right, b) using regression model.</p

Relationship between Age and ROAR.

<p>Plot of the dataset used in the regression process to estimate age as function of ROAR, along with regression line.</p

Peri-apical X-ray of African Lion PM².

<p>X-ray showing outline of total tooth and pulp areas for calculating area ratio using Adobe Photoshop after Cameriere et al. (2011) [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0153648#pone.0153648.ref033" target="_blank">33</a>]. Full details of the outlining and area measuring method are provided in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0153648#pone.0153648.s001" target="_blank">S1 Text</a>.</p

ANCOVA Analysis.

<p>ANCOVA Analysis.</p