Differentiating captive and wild African lion (Panthera leo) populations in South Africa, using stable carbon and nitrogen isotope analysis

Abstract

The international trade in lion (Panthera leo) products, particularly bone, has increased substantially over the last decade. The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) has established a zero-export quota for wild-origin lion bones. Whilst the trade of lion bone is permittable from captive-bred South African populations, there is no established method to differentiate between captive and wild-sourced lion derivatives in trade. This study acts as a preliminary investigation, by examining the stable carbon (δ13C) and nitrogen (δ15N) isotope composition of hair from wild and captive lion populations as well as wild prey animals in South Africa, to judge the accuracy and applicability of this method for future bone analysis. Isotopic values for δ15N are found to be significantly enriched in some wild populations, however it is not possible to discriminate between captive and wild populations using δ13C analysis alone. Using the classification algorithm k-Nearest Neighbour, the origin of simulated data was identified with 70% accuracy. When using the model to test the origin of seized samples, 63% were classified as of wild origin. Our study indicates the potential for stable isotope analysis to discriminate between captive and wild populations. Additional study of captive husbandry, and analysis of bone samples from populations of a known origin and feeding regime is recommended to improve the utility of this method for maintaining transparency in trade.