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

• Published in: Mammal review 2022-07, Vol.52 (3), p.322-327
• Main Authors: Falconi, Nereyda, Carlo, Tomás A., Fuller, Todd K., Destefano, Stephen, Organ, John F.
• Format: Article
• Language: English
• Subjects: Ailuropoda melanoleuca; bears; carnivory; Crop damage; Diet; Ecology; Food availability; Livestock; Nitrogen‐15; Omnivores; omnivory; Polar bears; Predation; Signatures; stable isotopes; trophic position; Ursidae; Ursus maritimus
• ISSN: 0305-1838; 1365-2907
• DOI: 10.1111/mam.12285

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 δ15N (‰) values and examined their correlation with diets reported in the literature, including frequency of human–bear conflicts (livestock predation and crop damage incidents). Overall, 15N signatures were consistent with diet estimates. Bear species with higher 15N signatures differed more from each other, including cases of large regional intraspecific variance, than bear species with lower 15N 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. We inferred bear trophic positions from stable isotope values from hair samples of the eight species of bear in six localities. Bear species with higher 15N signatures, such as polar bears Ursus maritimus, differed more from each other than bear species with lower 15N signatures, such as giant pandas Ailuropoda melanoleuca, Asian black bears Ursus thibetanus, Andean bears Tremarctos ornatus, and American black bears Ursus americanus. The brown bear Ursus arctos was the species with highest intraspecific variance of 15N signatures. We examined diets reported in the literature and the frequency of human–bear conflicts, and correlated both variables with 15N signatures. 15N signature was correlated with diet, but not with frequency of reports of human–bear conflicts or bear trophic position. We suggest that livestock predation by bears is an opportunistic behaviour rather than a response to food availability dynamics. Bear artwork by Roger Hall.