Age difference in activity pattern of Japanese monkeys: Effects of temperature, snow, and diet

Abstract

Air temperature, snow depth, and diet composition were found to affect the activity budgets of 1 ∼ 2-year-old, 3 ∼ 4-year-old and adult female (>5 years old) Japanese monkeys (Macaca fuscata) in the Shimokita Peninsula. They spent more time resting as the air temperature decreased. They spent less time moving on the ground, so that they moved shorter distances, where the snow was deep. However, they spent more time moving on the ground as they fed more on fruits and seeds. Adult females moved mainly on the ground, while 1 ∼ 2-year-olds moved on the tree branches as well as on the ground. Adult females increased their time moving on the tree branches where the snow was deep but 1 ∼ 2- and 3 ∼ 4-year-olds did not. The 1 ∼ 2- and 3 ∼ 4-year-olds but not adult females increased their feeding time as they fed more on buds and barks containing abundant fiber. We hypothesize that the large body size of adult females may constrain them to move mainly on the ground, and might enable them to choose energy saving tactics more easily.