High but not low tolerance populations of Japanese macaques solve a novel cooperative task.

Currently, it has been revealed that high levels of tolerance facilitate the occurrence of cooperative behavior in animals. This predicts that Japanese macaques (Macaca fuscata) would fail to solve cooperative food-retrieval tasks because of their low level of social tolerance. However, Japanese macaques exhibit regional differences in their levels of tolerance. In this study, we showed how inter-group difference in social tolerance could affect cooperation, by presenting a well-established cooperative rope-pulling task with two free-ranging groups of Japanese macaques that exhibit different levels of social tolerance. We used the task that required two macaques to pull both ends of a single rope simultaneously to obtain food rewards. We found that some macaques from the more tolerant group successfully solved the task, and one of them learned to wait for a partner when a partner was absent. In contrast, however, those of the less tolerant group almost never succeeded in the task. These results indicate that Japanese macaques possess the abilities to cooperate with conspecifics, but such abilities may be constrained in their typically despotic society.