Hurricane Maria caused widespread destruction in the Caribbean, not only to humans but also to wildlife. Five years after the storm, some effects still linger.
Cayo Santiago, a small island off the southeast coast of Puerto Rico, is a good example. It transformed almost overnight from a lush jungle oasis into a desert-like sandy expanse of mostly bare trees.
This poses a big problem for the island’s resident monkeys. The monkeys depend on shade to stay cool in the tropical daytime heat, but with trees wiped out, the storm left that resource in very short supply.
Rhesus monkeys are known to be one of the most quarrelsome primates on the planet, with a strict social hierarchy maintained through aggression and competition. So it follows that an ape battle will break out over the island’s few remaining shaded patches.
However, that’s not what happened. Instead, the monkeys did something seemingly inexplicable: They began to get along with each other.
“This is really not what we expected,” said Camille Testard, a behavioral ecologist and neuroscientist at Harvard University. “Instead of becoming more competitive, individuals expanded their social networks and became less aggressive.”
An article by Dr. Testard and her colleagues, was published Thursday in the journal Science, offers an explanation for this unexpected development. They found that monkeys that learned to share shade after the storm had a better chance of survival than those that remained quarrelsome.
Scientists have documented many cases of species responding to environmental pressures with physiological or morphological adaptations. But this new study is one of the first to show that animals can also respond to persistent changes in their social behavior, Dr. Testard said.
She and her colleagues took advantage of data collected over about 12 years at the Cayo Santiago Field Station, the world’s longest-running primate field site. Researchers introduced rhesus monkeys to the 38-acre island in 1938 and have been studying them ever since.
The approximately 1,000 monkeys living on the island are free-ranging but are fed by field station staff. “Access to food is not the main point of contention,” Dr. Testard said. “Shade is okay to avoid heat stress.”
Daytime temperatures in Cayo Santiago often soar above 100 degrees Fahrenheit, or about 38 degrees Celsius, which can be fatal for monkeys trapped in the sun.
After Hurricane Maria destroyed most of the island’s trees, Dr. Testard and her colleagues expected that apes might invest more in building tight alliances so they could join forces to Provide shade. But she said “the exact opposite” happened. Instead, monkeys invest in looser partnerships with larger numbers of animals, and they generally become more tolerant of each other.
Dr. Testard said she suspects that this is because fighting is an activity that consumes a lot of energy, generates more body heat, and is more dangerous to individuals than “just being concerned about having Is another coin next to you or not?
During the hottest hours of the afternoon, researchers observed groups of monkeys crowded together in thin strips of shade. But even as temperatures became less oppressive, animals still gathered in larger groups than they were accustomed to before the storm, Dr. Testard said.
Not all monkeys jump on the peace train, but those with aggressive attitudes are more likely to pay a heavy price. The overall mortality rate of the monkey population did not change after the storm. But monkeys with more friendly relationships had a 42% lower mortality rate because they were less susceptible to heat stress.
“Who dies and for what reason has changed,” Dr. Testard said.
Noa Pinter-Wollman, a behavioral ecologist at the University of California, Los Angeles, who was not involved in the study, said that the “exciting” findings are “a great example of how sociability can be.” reduce the negative impacts of environmental change”.
Julia Fischer, a behavioral biologist at the German Primate Center in Göttingen, who was also not involved in the study, added that the “extremely well done study” highlighted the importance of flexibility. in behavior that helps animals survive when their habitat is disrupted. “In the context of climate change, this is extremely important,” she said.
Whether other animals can also respond to environmental fluctuations by adjusting their social norms “will depend very much on the species and the context,” Dr. Testard said. However, humans probably fall into that category. For example, people often come together after natural and man-made disasters.
However, Dr. Testard added, there are limits. If resources become too scarce, humans could fall into Mad Max-like violent competition. “There is hope that we will work together to solve things instead of fighting,” she said. “But that’s a big guess.”
