Hurricane on Monkey Island made macaques more socially tolerant

Picture this: a tropical paradise teeming with playful monkeys, lush foliage providing ample shade from the Caribbean sun. But then, disaster strikes. A devastating hurricane rips through the island, stripping away the trees and leaving the monkeys exposed to the harsh elements.

What happens next? Do they fight over the remaining scraps of shade, or do they band together and share?

A recent study reveals a surprising twist: the monkeys actually became more tolerant of each other in the wake of the storm. This unexpected turn of events offers valuable insights into how animals adapt to environmental challenges and the power of social connections in times of crisis.

The storm that changed everything

In 2017, Hurricane Maria, a powerful Category 4 storm, made landfall in Puerto Rico, leaving a trail of destruction in its wake. The storm’s impact was not limited to the mainland; the nearby island of Cayo Santiago, a small island off the coast of Puerto Rico, was also severely affected. 

Cayo Santiago, often referred to as “Monkey Island,” is home to a well-established population of rhesus macaques that have been the subject of scientific research for over 80 years. 

The hurricane decimated the island’s ecosystem, stripping away 63% of its vegetation. This loss of foliage significantly reduced the availability of shade, a crucial resource for the monkeys to cope with the intense tropical heat. The monkeys were suddenly confronted with a drastically altered environment and limited options for shelter from the sun.

“In response to the drastic changes caused by the hurricane, macaques persistently increased tolerance and decreased aggression towards each other,” said Dr. Camille Testard from the University of Pennsylvania. This change in behavior wasn’t just a temporary blip; it persisted for years after the storm.

Cooperation on Monkey Island after hurricane

Why did the monkeys suddenly become more cooperative? The answer lies in the concept of “selection pressure.”

In the pre-hurricane environment, where shade was plentiful, there was no evolutionary advantage to being tolerant of others. But after the storm, the ability to share shade became a matter of life or death. Monkeys who were more tolerant were more likely to survive and pass on their genes, leading to a shift in the overall social dynamics of the population.

“Before the hurricane, tolerating others had no impact on risk of death. Afterwards, macaques that displayed more than average social tolerance – and were therefore better able to share shade – were 42% less likely to die than those that were less tolerant,” explained Dr. Testard.

A new social order on Monkey Island

The study revealed that the monkeys’ newfound tolerance extended beyond just sharing shade. They also spent more time grooming each other and engaging in other affiliative behaviors. 

“Macaques that began sharing shade also spend time together in the mornings, before the day’s heat forces them to seek shade. In effect, the hurricane changed the rules of the game in the monkeys’ society,” said Dr. Testard.

This remarkable transformation challenges the traditional view of rhesus macaques as aggressive and competitive. It demonstrates their surprising flexibility and resilience in the face of adversity.

“We were surprised the macaques’ social behavior was so flexible, making them resilient to this environmental change, but some species may not display this same flexibility,” stated Professor Lauren Brent from the University of Exeter.

Lessons for a changing world

The implications of this research extend beyond the monkey island’s adaptation to hurricanes and into the broader context of our changing world. As climate change intensifies, numerous species will encounter environmental pressures like those experienced by the Cayo Santiago macaques.

By studying how animals adapt to such challenges, we can gain valuable insights into the mechanisms of resilience and apply this knowledge to conservation efforts. 

Understanding how social behavior can act as a buffer against environmental stress can inform strategies for protecting vulnerable populations and maintaining biodiversity in the face of climate change.

The remarkable adaptability of the Cayo Santiago macaques, who transformed adversity into an opportunity for increased cooperation and survival, serves as a beacon of hope. 

Their story underscores the potential for resilience and adaptation even in the most challenging circumstances, reminding us that even when faced with seemingly insurmountable obstacles, the possibility for positive change and a brighter future remains.

The study is published in the journal Science.

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