On Monkey Island, It's Now Survival of the Nicest

Study suggests macaques off Puerto Rico getting along better after hurricane, out of necessity
By John Johnson,  Newser Staff
Posted Jun 24, 2024 11:11 AM CDT
On Monkey Island, It's Now Survival of the Nicest
A rhesus macaque grooms another on Cayo Santiago, known as Monkey Island, off the eastern coast of Puerto Rico.   (AP Photo/Brennan Linsley, File)

A strange thing happened on Monkey Island after a massive hurricane ripped through: The usually quarrelsome monkeys became nicer to each other, a new study in Science suggests. As it turns out, it was a matter of survival, the BBC explains. Monkey Island is the nickname given to Cayo Santiago, off the coast of Puerto Rico, because of its large population of rhesus macaques. When Hurricane Maria blew through in 2017, it decimated the island's population of trees, whose shade is vital to keeping the monkeys cool in a place where temperatures routinely hit 100 degrees.

Researchers figured it would make the monkeys even less tolerant of each other as they crowded together in the diminished shade. Instead, the opposite happened. "There was a general increase in social tolerance among the animals in the population," the researchers write, adding that the "most tolerant animals had the highest survival." Scientists documented fewer physical altercations than previously, and those monkeys that remained hostile have had a higher mortality rate—possibly because fighting takes up valuable energy.

"This was really not what we expected," Camille Testard, a behavioral ecologist at Harvard, tells the New York Times. "Instead of becoming more competitive, individuals widened their social network and became less aggressive." Another intriguing facet of the research is that the diminished aggressiveness seems to have carried over into times when the sun isn't bearing down. The findings could have implications for a warming planet, adds a researcher not involved with the study. (More monkeys stories.)

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