A mammoth task: stable isotope analyses as a tool to prevent illegal trade of elephant ivory

Abstract

Although mammoth ivory was claimed as a substitute to elephant ivory, there are several issues with the current methods to differentiate the two ivory, which provided a loophole to laundering and illegal trade. To contribute to developing efficient tools to distinguish ivory samples, we applied a relatively cheap and fast protocol using stable isotope ratios of carbon (δ¹³C), hydrogen (δ²H), nitrogen (δ¹⁵N), oxygen (δ¹⁸O), and sulfur (δ³⁴S). We compared the isotope ratios of the two ivory types and found statistically significant (p-value<0.01) differences in the Wilcoxon tests for δ²H, δ¹⁸O, δ¹³C and δ³⁴S, but no significant difference for δ¹⁵N. There was no overlap between δ²H and a small overlap for δ¹⁸O, while δ¹³C, δ¹⁵N, and δ³⁴S of most mammoth samples were within the larger isotopic range values of the elephant samples. The PCA also pointed to a higher contribution of δ²H (96.9%) followed by δ¹⁸O (2.7%) to differentiate the ivory types. Our results showed SIA as an efficient tool to distinguish elephant and mammoth ivory, and we recommend using a multi-elements SIA approach focusing on δ²H and δ¹⁸O. While it is essential to address the social issues related to the ivory trade, including reducing human-elephant conflict and increasing financial support to Siberian carver communities, alternatives for natural ivory should also be sought, combined with strict policy changes to combat illegal trade and protect the African and Asian elephant populations.