Dietary adaptations of temperate primates: comparisons of Japanese and Barbary macaques.

Habitat, diet and leaf chemistry are compared between Japanese and Barbary macaques to reveal the similarities and differences in dietary adaptations of temperate primates living at the eastern and western extremes of the genus Macaca. Tree species diversity and proportion of fleshy-fruited species are much higher in Japan than in North Africa. Both species spend considerable annual feeding time on leaves. Japanese macaques prefer fruits and seeds over leaves, and Barbary macaques prefer seeds. These characteristics are adaptive in temperate regions where fruit availability varies considerably with season, since animals can survive during the lean period by relying on leaf and other vegetative foods. The two species are different with respect to the higher consumption of herbs by Barbary macaques, and the leaves consumed contain high condensed and hydrolysable tannin for Barbary but not for Japanese macaques. Barbary macaques supplement less diverse tree foods with herbs. Because of the low species diversity and high tannin content of the dominant tree species, Barbary macaques may have developed the capacity to cope with tannin. This supports the idea that digestion of leaves is indispensable to survive in temperate regions where fruit and seed foods are not available for a prolonged period during each year.

Seasonal changes in food resource distribution and feeding sites selected by Japanese macaques on Koshima Islet, Japan.

Feeding sites of Japanese macaques (Macaca fuscata) change according to seasonal fluctuations in food resource distribution. To examine what characteristics of food items affect feeding site selection, I describe herein the seasonal changes in food items, feeding sites, and food resource distributions of this species. Feeding behavior of monkeys and their food resource distributions were investigated on Koshima Islet, southern Japan, for four study periods (i.e., seasons) in 2002. Monkeys showed large variations in their diet between seasons. To weigh the relative influence of the distribution and abundance of food items on feeding site selection in each season, multiple regression analyses were performed by 100 m x 100 m grid. In the analyses, feeding time was a dependent variable and the abundance of staple food items, for which feeding time was over 5% in each season, in each grid square was an independent variable. There was no correlation between the resource distribution of most food items and the distribution of feeding time by monkeys in each season. Monkeys spent more feeding time where multiple staple food items were available. Food items that affected feeding site selection by monkeys had the following three characteristics: (1) clumped distribution, (2) seasonal availability, and (3) fruit. This suggests that monkeys are likely to select feeding sites to consume food items whose availability is limited temporally and spatially, which may enable them to simultaneously use other widely distributed, abundant food items efficiently.