Japanese macaques on Awajishima island in Hyogo Prefecture work together to pull food toward them. (Provided by Osaka University’s Graduate School of Human Sciences)

Japanese macaques help each other to achieve a common goal, according to an Osaka University study, highlighting the importance of tolerance of others in society.

The research team, which includes Masayuki Nakamichi, a primatology professor at the college's Graduate School of Human Sciences, and graduate student Yu Kaigaishi, said that although Japanese monkeys are known to form a strict pecking order and a relatively intolerant community, tolerance of others is key when it comes to cooperative acts.

"In a highly tolerant society, members do not attack each other even when in close quarters, allowing for social negotiation," Kaigaishi said. "The cooperative behavior (of the monkeys) confirmed in the latest study reflects this. The findings will also prove helpful in analyzing the evolution of human societies where people cooperate in various ways.”

Japanese macaques were not believed to help one another in securing food, as monkeys with a high social status tend to drive away lower-ranking ones to keep the foodstuffs for themselves.

For the study, the team developed a food supply system equipped with ropes from which two macaques can get food when they are pulled simultaneously. If only one rope is pulled, the animals cannot obtain the food.

Using the contraption, the scientists conducted tests to see whether the macaques can behave cooperatively in a 381-monkey population inhabiting Awajishima island in Hyogo Prefecture, known for its high tolerance level, and 148 intolerant macaques in Maniwa, Okayama Prefecture.

The Awajishima macaques succeeded in obtaining food in 60 percent of the 1,500 tests carried out, according to the results.

While monkeys that have close blood relationships, such as mother and daughter, are more likely to attain the target, macaques with greatly different rankings and those that are not close relatives succeeded as well, according to the team.

The study also found that the macaques on Awajishima learned to wait for another to appear when there was no potential rope-pulling partner around.

In contrast, Japanese macaques in Maniwa have a rigorous pecking order and thus scare off others that come close to them, making it rare for two monkeys to show up as a pair. As a result, they succeeded in only 1 percent of the 200 tests.

Based on the results, the team concluded that not only intelligence, but also high social tolerance levels are essential to cooperative actions made in communities.

The findings have been published in the online edition of the international academic journal Primates at (https://doi.org/10.1007/s10329-019-00742-z).