Abstract
Asiatic black bears and Japanese macaques are sympatric in cool temperate forests in Japan. The two species utilize similar food resources both on the ground and in trees; their major foods in spring are young leaves and shoots, and the proportion of plant fibers consumed decreases with the increase of consumption of fruits. Both species prefer fruits; however Japanese macaques adapt to consumption of fibrous foods more than Asiatic black bears, which means survivorship of Japanese macaques is secured by more fallback foods than black bears. This idea is also supported by investigation of the morphology of mastication and digestive organs, abundance of pepsinogens, and characteristics of home range utilization. The two species might compete in a scramble manner for fruits which are preferred by both species and are rare food resources. Macaques might avoid direct interference over food resources because the black bears can be a predator of macaques. The idea of preferred and fallback foods is useful to discuss phylogenetic inertia and adaptation of two species as well as conservation of them.
