But the disaster brought the monkeys together in unexpected new ways — showing that extensive social connections serve an important scientific purpose, according to a study published Thursday in the journal Current Biology.
Lead author Camille Testard, a Ph.D. student and a researcher at Platt Labs, says the results may show the connection between group behavior and evolution.
“Our results help us to answer a big outstanding question: What benefits do social relationships provide and [what] might be responsible for their evolution?” Testard tells Inverse.
How they did it — Researchers observed two groups of adult rhesus macaques on Cayo Santiago Island one year after Hurricane Maria, which devastated Puerto Rico in 2017. The island is home to the Caribbean Primate Research Center, and the macaques were introduced there for research purposes.
Although their adopted home was devastated by Hurricane Maria — green vegetation on Cayo Santiago Island declined by 63 percent — relatively few monkeys died.
Using linear models, the researchers compared the monkeys’ social behavior pre- and post-hurricane, looking specifically at two factors: the macaques’ proximity to other primates and their grooming habits. Grooming is a form of social behavior in monkeys, which establishes social hierarchies and builds social bonds.
This provides a unique research opportunity for researchers to explore how social norms change in an environment disrupted by climate change, but one where massive loss of life did not occur.
The researchers also asked five big questions:
- Did the macaques display new or increased social behaviors after the hurricane?
- Did all monkeys display the same social behaviors post-hurricane, or were these behaviors influenced by other factors, like the death of a grooming partner or the outgoing behavior — gregariousness — of individual monkeys?
- Did monkeys build new relationships, strengthen existing ones, or both?
- Which monkeys did individual macaques interact with following the hurricane (i.e., relatives, close friends, higher-ranked individuals in the group, or someone else)?
- Did mere proximity to other monkeys lead to new relationships?
What’s new — Researchers hypothesized that monkeys would become more sociable due to a principle known as the social buffering hypothesis. According to the study, the hypothesis states that “social relationships might be crucial for surviving extreme environmental challenges.”
“A tremendous source of instability for humans and other animals alike are natural disasters such as earthquakes, tsunamis, and hurricanes — which are predicted to increase in frequency and force,” Testard says.
“Social relationships, and particularly broad social tolerance, may be crucial for surviving these extreme environmental challenges.”
The researchers confirmed their hypothesis, finding that adult monkeys “actively sought social contact” and didn’t just rely on proximity to make friends after the disaster.
They summarized their results in four key findings:
- The monkeys became more socially connected following Hurricane Maria
- They forged new social bonds instead of strengthening existing ties
- The macaques often followed the “path of least resistance” by reciprocating other monkey’s grooming attempts to form social bonds
- Those that were most isolated before the storm developed the most connections afterward
Digging into the details — But not all of the results were expected, according to Testard.
“We expected the monkeys would use their closest allies to cope with the ecological devastation of the hurricane and so would invest in their existing relationships like their kin or best friends,” she says.
Since these close allies serve as “critical sources of social support in competitive times,” the researchers’ assumptions made sense, according to Testard.
But that’s not what happened. Instead, the macaques developed a tolerance for a greater number of social connections, focusing on a greater quantity — not quality — of friendships.
The researchers speculate that the loss of shade from trees and other vegetation following Hurricane Maria may have triggered these counterintuitive new relationships.
Animals use shade to stay cool in the hot Caribbean climate. But the significant loss of vegetation suddenly made shade a precious commodity following Hurricane Maria.
Befriending a greater number of other monkeys could theoretically give macaques easier access to shade.
The researchers write:
“In the degraded landscape produced by Hurricane Maria, it might be particularly important to seek out social support from a large pool of partners to access a rare yet diffuse resource like shade.”
Why it matters — The researchers compare the situation with the monkeys on Cayo Santiago Island to other natural disasters that have devastated human habitats, like Hurricane Harvey, which wreaked havoc on Texas in 2017.
The climate crisis has increased the likelihood of extreme weather events and natural disasters. Humans can learn a thing or two from studying how our closest primate relatives cope with the adverse effects of climate change, according to Testard.
The main takeaway for humans: go beyond your close-knit circle of friends and form a broader social network to survive tough times.
“Our best friends can give us many things. But sometimes, what we need is a social network where everyone is just friendly enough,” Testard says.
What’s next — The ongoing climate crisis will bring new challenges to humans and animals alike, particularly through natural disasters. Studies like those conducted by Testard and her team will prove vital to understanding how animals — and humans — cope with a changing world.
For her part, Testard would like to focus on the monkeys and “investigate the long-term impacts of making new friends, or failing to do so, in this extreme context.”
For example: are there certain biological traits that predispose monkeys to invest in new relationships? Could developing more social connections give monkeys greater longevity or a better chance of making babies?
In such an extreme context, making friends could be the difference between life and death.
“Going forward, studies of how animals adjust, socially or otherwise, to these massive transformations of their habitats will be important for addressing why some species, or individuals, are resilient and others more vulnerable,” write the researchers.
Abstract: Climate change is increasing the frequency and intensity of weather-related disasters such as hurricanes, wildfires, floods, and droughts. Understanding resilience and vulnerability to these intense stressors and their aftermath could reveal adaptations to extreme environmental change. In 2017, Puerto Rico suffered its worst natural disaster, Hurricane Maria, which left 3,000 dead and provoked a mental health crisis. Cayo Santiago Island, home to a population of rhesus macaques (Macacamulatta), was devastated by the same storm. We compared social networks of two groups of macaques before and after the hurricane and found an increase in affiliative social connections, driven largely by monkeys most socially isolated before Hurricane Maria. Further analysis revealed monkeys invested in building new relationships rather than strengthening existing ones. Social adaptations to environmental instability might predispose rhesus macaques to success in rapidly changing anthropogenic environments.o