Stable isotope ecology of black rhinos (Diceros bicornis) in Kenya

Stable isotope and elemental ratios in hair are influenced by the environment, including both climate and geology. Stable carbon isotopes can be used to give estimates of the C-4/CAM fraction of diets of herbivorous mammals; stable nitrogen isotopes are related to the local water deficit; strontium isotopes are determined by the local geology. We studied hair from rhinos in Kenya to determine spatial patterns in delta C-13, delta N-15, and Sr-87/Sr-86 ratios. The samples of rhino hair were collected during Kenya Wildlife Service translocation or veterinary activities. delta C-13 values showed diets dominated by C-3 foods, but in some regions the diet, at least seasonally, contained significant quantities (i.e., > ca. 20%) of C-4/CAM foods. delta N-15 values were related to water deficit, with higher delta N-15 values in regions with high water deficit. Sr-87/Sr-86 isotope ratios were found to be related to the local geological substrate suggesting that Sr-87/Sr-86 isotope ratios are provisionally useful for determining the origins of illegal wildlife materials in Kenya and elsewhere in Africa.