Stomach contents of brown bears Ursus arctos in Hokkaido, Japan

Abstract

We determined the seasonal food habits of brown bears Ursus arctos in three regions of Hokkaido, Japan, over eight years (1991–1998) by analysing the stomach contents of 556 bears killed for nuisance control or sport hunting. Seasonally dominant food items changed from herbaceous plants (61–80% in volume) in spring, to herbaceous plants (53–97% in volume) and ants (0–18% in volume) in early summer, crops (32–46% in volume) and herbaceous plants (26–31% in volume) in late summer, and berries (25–39% in volume), acorns and nuts (8-16% in volume) in autumn. These diet shifts were consistent among the three investigated regions. Crop depredation by brown bears in late summer occurred extensively in Hokkaido and was probably driven by a shortage of alternative food sources during this season. The proportion of sika deer Cervus nippon yesoensis in the diet increased during the 1990s in eastern Hokkaido (25.2% in frequency), where bears consumed deer throughout the year. Bears probably acquired deer meat from carcasses left in the fields after the deer were shot for nuisance control and sport hunting. In the Oshima Peninsula of southern Hokkaido, bears consumed large amounts of anthropogenic waste (16% in frequency).