The hurricane was a “game changer” for this community. And it's not about people

Hurricane Maria hit Puerto Rico in September 2017. The element hit the coast with wind speeds of almost 250 kilometers per hour. The hurricane contributed to the death of approximately 3,000 inhabitants of the island and caused enormous destruction.

He also did not spare the island of Cayo Santiago, located off the eastern coast of Puerto Rico – this place, also known as “monkey island”, is a place where a large population of king macaques is studied (Macaca mulatta). After the disaster, 63 percent of the plant cover was destroyed and has not been rebuilt since then. Scientists from the universities of Pennsylvania in the US and Exeter in the UK looked at how the disaster affected the lives of these intelligent monkeys.

In a study published in the journal Science, scientists analyzed data on the strength and number of social bonds in macaques before and after the hurricane. Social behavior was assessed by recording aggression and how often individuals were seen sitting together. The authors looked particularly closely at how animals coexist in the shade – the damaged trees of Cayo Santiago made the shade a rare and valuable resource there.

The results showed that before the hurricane, tolerating other individuals had no effect on the probability of survival. After the disaster, macaques that could withstand the presence of other monkeys in the shade next to them were 42 percent less likely to die than those that avoided company and chose to sit alone, away from others – and the shadow.

– Macaques are not the best at sharing resources, whether it's food or shade. We know they live in an aggressive, highly competitive society, said Lauren Brent of the University of Exeter, co-author of the analysis. “However, in the heat caused by environmental changes, often reaching 40 degrees Celsius, the macaques had to tolerate each other or face death,” she added.

As the paper's lead author, Camille Testard of the University of Pennsylvania, explained, to gain access to shade, monkeys must tolerate – and be tolerated by – other members of the community. As researchers discovered, this tolerance translates into other interactions between animals.

“Macaques that have started sharing shade also spend time together in the morning before the heat forces them to seek shade,” she said. – The hurricane changed the rules of the game in ape society – she added.

Brent added that for animals that live in groups, social relationships can help them cope with sudden changes in the environment, including climate change. However, not all species may be as resistant to sudden disturbances as macaques.

King macaques come from southern Asia. They appeared on Cayo Santiago in the late 1930s, when primatologist Clarence Carpenter brought about 450 monkeys by ship from India to study their social and reproductive behavior. Currently, the population has grown to approximately 1,500 individuals.