After a Weather Disaster, a Surprise: Some Ornery Monkeys Got Nicer

Hurricane Maria caused widespread devastation in the Caribbean, not only for people but also for wildlife. Five years after the storm, some of the effects still linger.

Cayo Santiago, a small island off the southeastern coast of Puerto Rico, is a prime example. It transformed almost overnight from a lush jungle oasis to a desert-like spit of sand with mostly skeletal trees.

This posed a big problem for the island’s resident macaques. The monkeys depend on shade to keep cool in tropical daytime heat, but, by wiping out the trees, the storm had rendered that resource in very short supply.

Rhesus macaques are known for being some of the most quarrelsome primates on the planet, with strict social hierarchies maintained through aggression and competition. So it would follow that a simian battle royale would break out over the island’s few remaining patches of shade.

Yet that’s not what happened. Instead, the macaques did something seemingly inexplicable: They started getting along.

“This was really not what we expected,” said Camille Testard, a behavioral ecologist and neuroscientist at Harvard University. “Instead of becoming more competitive, individuals widened their social network and became less aggressive.”