Effects of habitat differences on feeding behaviors of Japanese monkeys: Comparison between Yakushima and Kinkazan

Abstract

Feeding behaviors of Japanese monkeys (Macaca fuscata) were compared between a warm temperate habitat (Yakushima Island: 30°N, 131°E) and a cool temperate habitat (Kinkazan Island: 38°N, 141°E). The composition of diet and the activity budget in the two habitats were very different. Time spent feeding on Kinkazan Island was 1.7 times that on Yakushima Island. Two factors seem to be responsible for these: (1) the energy required for thermoregulation of monkeys on Kinkazan Island is greater than that on Yakushima Island; and (2) the food quality, which affects the intake speed of available energy, is lower on Kinkazan Island. However, monkeys in both habitats increased their moving time and decreased their feeding time when they fed on foods of relatively high quality. Such foraging strategies are predicted by optimal foraging models. Time spent social grooming on Yakushima Island was 1.9 times that on Kinkazan Island, although there were slight seasonal changes in both areas. The difference in time spent social grooming might be explained by the overall difference in feeding time and day length between the two habitats.