Japanese macaques are generally known to be very tolerant and form a tightly ranked society.For example, if there is attractive food, high-ranking monkeys will drive away low-ranking monkeys and monopolize it, so actions such as cooperating with other individuals to accomplish tasks that cannot be accomplished by one monkey alone , It has been thought that it does not occur in Japanese monkeys.

　On the other hand, it has become clear in recent years that the tolerance of Japanese macaques varies from region to region.In particular, the population that inhabits Awaji Island is extremely tolerant of Japanese macaques, and it is said that monkeys with different ranks can share food.

　Previous studies have shown that differences in tolerance have a significant impact on the outcome of cooperative behavioral tasks.Therefore, in this study, we conducted a cooperative behavior experiment between the highly tolerant Awajishima Japanese macaque population and the less tolerant Katsuyama Japanese macaque population.
In the task used in the experiment, the string is pulled out when only one of them pulls the string to attract the food that is out of reach.To get food, two monkeys must pull both ends of the string at the same time.

　As a result, in the Katsuyama Japanese macaque group, fighting occurred and low-ranked individuals were driven away, so that cooperation was hardly established, while in the Awajishima Japanese macaque group, monkeys cooperated and were able to solve problems many times.The group also learned to wait without pulling strings until a partner arrives when there is no partner nearby.

　From this, it was found that high tolerance is important for cooperative behavior to occur in society.This result provides new suggestions for the evolutionary path of human cooperative society, and also provides new insights into the diverse ways of Japanese macaque society.

Paper information:[Primates] High but not low tolerance populations of Japanese macaques solve a novel cooperative task