Deer fear bear? A test of nonconsumptive effects on sika deer by an omnivorous Asiatic black bear

Abstract Nonconsumptive effects (NCEs) on prey animals by predators have received considerable interest in wildlife ecology and conservation. However, NCEs by large carnivore species with omnivorous diet still remain unclear. The Asiatic black bear (Ursus thibetanus) is widely found in eastern parts of the Eurasian Continent, including Honshu and Shikoku Islands of Japan. At present, this bear species is the only large carnivore in the region as a typical omnivore that occasionally predates sika deer (Cervus nippon). If sika deer recognize predation threats from black bears, then the NCEs by bears will provoke antipredator behavioral responses by the deer. In testing this hypothesis, we evaluated the spatial and temporal overlaps between bears and deer as well as compared the vigilance level and spatiotemporal avoidance observed in sika deer between bear-active and -inactive years, using camera trapping in an agroforest landscape in Fukushima, eastern Japan. Consequently, we found little changes in deer behaviors between bear-active and -inactive years, indicating that sika deer neither exhibited spatial partitioning and spatiotemporal avoidances from black bears nor increased their vigilance even in bear-active year. We concluded that our study showed no significant NCE of omnivorous Asiatic black bears on sika deer.