Adjustment of Temporal Call Usage During Vocal Exchange of Coo Calls in Japanese Macaques

Japanese macaques ( Macaca fuscata ) exchange coo calls with group members to maintain contact. I examined the relationship between the distance between group members and (1) the latency of vocal responses to spontaneous calls, and (2) the latency of spontaneous call repetition in the absence of vocal responses. After a subject monkey's spontaneous call, the latency of vocal response by another group member was longer when the subject was farther from the group members than when the subject was near the group members. Furthermore, subject repeated calls with longer intervals in the absence of vocal response, which suggests that they wait longer for the vocal responses of other group members when the expected response latency is longer. These results reveal that Japanese macaques flexibly alter the timing of their calls based on others’ vocal responses.