Lifetime Social Development in Female Japanese Macaques

Abstract

The present chapter reviews lifetime social development of female Japanese macaques, mainly based on studies conducted on groups that are provisioned and free-ranging or wild. During the first year of life, infants not only nurse on their mothers but also acquire the repertoire of edible food items by intensively observing their foraging mothers. Differences between female and male juveniles in terms of social relationships with mothers and other group members become clear from the second year of life onward, with few differences observed among different groups. Juvenile females maintain relatively frequent interactions with their mothers and are inclined to maintain close proximity relationships with group members who usually form the center of the group; furthermore, they actually tend to interact with younger individuals through social play and infant-handling, while still rarely maintaining affiliative relationships with adult females other than their mothers. Adolescent females tend to be integrated into the social network after first giving birth. Dominance relationships among adult females are strongly influenced by group size: in relatively small groups, dominance relations adhere almost perfectly to Kawamura's rules, whereby females are collectively ranked within their kin-groups, and a clearly linear dominance rank order is apparent. However, with an increasing number of adult females in a group, the number of dyads whose dominance relationships do not follow Kawamura's rules tends to increase and the linear dominance rank order becomes less apparent. Although the Japanese macaque is categorized as a despotic species among Macaca species, each group may include some females who show egalitarian tendencies such as nonkin-biased grooming; such females may play a role in increasing the integrity and cohesion of a group. In Japanese macaque groups, the number of females who experience the postreproductive period is very small. However, some such aged females could contribute to the survival of their young grandchildren. Accumulating data on the daily life of each female and describing the long-term social relationships among females could lead to a fuller understanding of the lifetime social development of female Japanese macaques.