Japanese macaques form a matrilineal, multi-male, multi-female group. In such a group, motivation to contact group members should differ among age-sex classes. Wild Japanese macaques emit coo call frequently and thereby maintain spatial cohesiveness of the group. The rate of coo calls can differ among age-sex classes reflecting their motivation of contacting group members. In this study, we examined the difference in the rate of coo call and the rate of the vocal response from the other group members among different age-sex classes, in the wild groups of Japanese macaques on Yakushima Island, Japan. Overall, adult females and juveniles of both sexes emitted coo calls more frequently than adult males. Adult females and males called more frequently when they were separated from group members. In contrast, juveniles called similarly frequently either when they were separated from group members or when they were close to them. Adult females and males were responded vocally more often than juveniles. These results suggest that adult females and juveniles are highly motivated to contact others. However, juveniles call frequently even when the group is cohesive and this may result in the lower response rate from group members. In contrast, adult males are less motivated to contact group members, probably because of their peripheral nature in the group. However, the high response rates to adults' calls suggest that the other group members are motivated to contact adult females and males.
