Direct observation of bear myrmecophagy: Relationship between bears' feeding habits and ant phenology

Abstract

We studied the ant-feeding behavior of Asiatic black bears (Ursus thibetanus) through direct observation in the Ashio area of Japan. We recorded the bears' " time foraging per ant nest" (TPN), documented the seasonal occurrence of ants in their scats, estimated phenological changes in caste composition of the nests of two abundant ant species (Lasius flavus and . L. hayashi), and calculated the nutritional composition of queens, males, workers, queen pupae, and non-queen pupae of both species. We addressed two main hypotheses: (1) ant-nest phenology, especially the availability of pupae, affects bears' myrmecophagy level; and (2) TPN changes according to the caste composition of ant nests. Bears in the Ashio area consumed more ants than in previous studies elsewhere in Japan, with consumption peaking in early July. The availability of pupae may trigger ant feeding by bears. And, because queen pupae were heavier than members of other castes, calories per individual were higher. TPN varied during the study period (late June-early August). There was a negative relationship between frequency of occurrence of pupae in ant nests and TPN; because pupae cannot move by themselves, bears could consume them effectively and quickly. Thus, bears may change their ant-foraging behavior (especially TPN) based on ant nest composition. © 2012 Deutsche Gesellschaft für Säugetierkunde.