Video-documentation of American Black Bear (Ursus americanus) foraging on algae in livestock tanks on a conservation property in western Montana, USA

Algae foraging by black bears

Résumé

Algae is an important food for many wildlife species. For ursids, marine algae is documented in Polar Bear (Ursus maritimus) diets, but freshwater algae has not been reported in American Black Bear (Ursus americanus) diets. We installed remote cameras at livestock tanks, in which freshwater algal blooms grew, to document Black Bear foraging behaviour. We video-documented algae foraging by four unique bears of both sexes and of different age classes. Algae foraging by two cubs and one adult female likely represented exploratory sampling because these three bears minimally foraged and did not subsequently return to the livestock tanks to forage on algae again. One adult male foraged on algae during three separate occasions, indicating his algae foraging was non-exploratory. We discuss possible hypotheses to explain freshwater algae consumption by Black Bear, including nutritional benefit, physiological relief, and parasite expulsion. Our study is the first to report algae foraging by American Black Bear, and our findings suggest that the benefits of Cladophora species for wild animals may be greater than is currently understood.