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

Lion spoor densities (N/100km): (a) at < and > 5 km from water in the WAP (the vertical lines represent the standard error); (b) in national parks and hunting areas of the WAP (the vertical lines represent the standard error).

<p>Lion spoor densities (N/100km): (a) at < and > 5 km from water in the WAP (the vertical lines represent the standard error); (b) in national parks and hunting areas of the WAP (the vertical lines represent the standard error).</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

Embargo on Lion Hunting Trophies from West Africa: An Effective Measure or a Threat to Lion Conservation?

<div><p>The W-Arly-Pendjari (WAP) ecosystem, shared among Benin, Burkina Faso and Niger, represents the last lion stronghold of West Africa. To assess the impact of trophy hunting on lion populations in hunting areas of the WAP, we analyzed trends in harvest rates from 1999 to 2014. We also investigated whether the hunting areas with higher initial hunting intensity experienced steeper declines in lion harvest between 1999 and 2014, and whether lion densities in hunting areas were lower than in national parks. Lion harvest rate remained overall constant in the WAP. At initial hunting intensities below 1.5 lions/1000km², most hunting areas experienced an increase in lion harvest rate, although that increase was of lower magnitude for hunting areas with higher initial hunting intensity. The proportion of hunting areas that experienced a decline in lion harvest rate increased at initial hunting intensities above 1.5 lions/1000km². In 2014, the lion population of the WAP was estimated with a spoor count at 418 (230–648) adults and sub-adult individuals, comparable to the 311 (123–498) individuals estimated in the previous 2012 spoor survey. We found no significant lion spoor density differences between national parks and hunting areas. Hunting areas with higher mean harvest rates did not have lower lion densities. The ratio of large adult males, females and sub-adults was similar between the national parks and the hunting areas. These results suggested that the lion population was not significantly affected by hunting in the WAP. We concluded that a quota of 1 lion/1000km² would be sustainable for the WAP. Based on our results, an import embargo on lion trophies from the WAP would not be justified. It could ruin the incentive of local actors to conserve lions in hunting areas, and lead to a drastic reduction of lion range in West Africa.</p></div

Proportional change in harvest of lions vs. initial average harvest regression models, value of the concordance criterion (CC), Equation, value of R² and P.

<p>The selected model is indicated in bold.</p

Results of the lion count.

<p>Area in km², Number of transects, Transects length in km, Substrate quality, Number of fresh spoors observed, Track density (N/100 km), estimated lion population density (N/100 km²), lion estimate (N), Coefficient of variation (CV) in %, minimum and maximum 95% Confidence Interval (CI) in each stratum of < and > 5 km from water and for the entire W Arly Pendjari Ecosystem. Details per area is given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0155763#pone.0155763.s002" target="_blank">S2 Table</a>.</p

Lion density in 2014 (N/100 km²), vs. the mean of 16 years harvest between 1999 and 2014 (mean number of lions harvested/1000 km²).

<p>Each point represents a hunting area.</p

ANCOVA Analysis.

<p>ANCOVA Analysis.</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