Bear diets and human-bear conflicts: insights from isotopic ecology

Bears, Ursidae, are considered omnivores, except for giant pandas Ailuropoda melanoleuca and polar bears Ursus maritimus. However, omnivory includes a wide range of dietary variation and trophic positions, making bear dietary ecology unclear. We inferred bear trophic positions from delta N-15 (parts per thousand) values and examined their correlation with diets reported in the literature, including frequency of human-bear conflicts (livestock predation and crop damage incidents). Overall, N-15 signatures were consistent with diet estimates. Bear species with higher N-15 signatures differed more from each other, including cases of large regional intraspecific variance, than bear species with lower N-15 signatures. Bear trophic position and frequency of reports of human-bear conflicts were uncorrelated, suggesting that livestock predation by bears is an opportunistic behaviour rather than a response to food availability dynamics.