Tomoko Naganuma, Shinsuke Koike, Rumiko Nakashita, Chinatsu Kozakai, Koji Yamazaki, Shino Furusaka, Koichi Kaji (2020) Age- and sex-associated differences in the diet of the Asian black bear: importance of hard mast and sika deer. Mammal Study 45 (2): 155-166.

　This study performed carbon and nitrogen stable isotope analyses of hair samples of Asian black bears, Ursus thibetanus, collected in the Ashio-Nikko Mountains, Japan, over more than 10 years and evaluated the age- and sex-associated differences in their diets among individuals and the influence of sika deer and hard mast abundance on the detected differences. Direct observations have shown that sociality affects the difference in diets among individual social animals. However, there are few studies of solitary, forest-dwelling animals because they are difficult to observe directly. The points of this study that the award committee rated highly were the application of stable isotope analysis to sufficient samples (> 50 individuals) collected in a long-term field survey (> 10 years), the discovery of differences in individual dietary changes in autumn in response to hard mast abundance of Fagaceae species, and the demonstration of the high reliance of mature males on sika deer in summer. The latter two were novel insights into the foraging ecology of the Asian black bear. The award committee thought that the research style of this study, using up-to-date technology, would facilitate the development of ecological research on wild animals. The presence of dietary variation among individuals also implies that we should pay attention to individual differences in the conservation and management of the Asian black bear.