Determination of species and geographic origin of rhinoceros horn by isotopic analysis and its possible application to trade control

The failure of the CITES ban to stop the illegal killing of rhinoceros for their horns, and the possibility of using horn from natural mortaility among the growing populations in South Africa to promote the consevation of rhinos, is a subject of current debate. Because of the differing conservation status of the African and Asian rhinoceros spieces, and individual populations, a strict control of trade in the horn would be required. Such a control system is feasible if the species and origin of rhino horn could be independently established from small samples. Recent work on source-area determination of African elephant ivory indicated that isotopic analysis could provide such a method, because of differences in diet, rainfall and geology. We found that black and white rhinoceros horn could be definitively distinguished on the basis of ¹³C values alone. White rhinoceros, being grazers, yielded ¹³C ratios of -10.1‰ to -10.5‰ while black rhinoceros being browsers, yielded ¹³C ratios of -20.3‰ to -24.6‰. Consideration of ¹⁵N and heavy isotope (strontium and lead) values indicated the area of origin of the samples.