SCIENTIFIC INSIGHT INTO "GROUP" FROM THE PERSPECTIVE OF SOCIO-ECOLOGY : ENVIRONMENT ADAPTABILITY THROUGH FLEXIBLE SOCIETY(<Special Issue>Variations in Physiological Functions)

Abstract

The benefits of grouping increase with group size, but simultaneously so do the costs. Depending on the circumstances, the degree to which costs and benefits vary, and the resultant optimal group size changes. I studied behavioral ecology of male Japanese macaques (Macaca fuscata yakui) and their method of association with groups and managing the costs and benefits associated with group formation. The decision of males to range with other animals depended on the intensity of inter- and within-group competition, their social position, and the reproductive potential of their group. This behavioral flexibility of males with respect to group cohesion contributed to the approach to the optimal group size.