A new analysis of wild gorillas in Rwanda indicates the effects of different social styles are dependent on context
Sarah Kuta – Daily Correspondent
May 7, 2025
Being social has upsides and downsides for mountain gorillas, according to a new paper that scientists say may help explain why some humans have more friends than others.
In the work published Monday in the journal Proceedings of the National Academy of Sciences, researchers describe the complicated interplay between the primates’ social lives and their health.
For the study, the team analyzed more than 20 years of data on 164 wild mountain gorillas (Gorilla beringei beringei) living in Volcanoes National Park in Rwanda.
The gorillas live in groups of roughly 12 individuals, including a single dominant male. But group size varies—some are smaller, some are larger. In addition, the gorillas had different social tendencies. Some were gentle and calm, for example, while others were more aggressive.
In humans and other social mammals, past research has linked strong interpersonal relationships with better health and longevity. But the recent study suggests having lots of friends comes with both pros and cons, at least for gorillas.
“Our study shows this isn’t a straightforward case of more and stronger social ties always being better,” says study co-author Sam Ellis, an animal behavior scholar at the University of Exeter in England, in a statement. “In some situations, social traits that we’ve previously thought of as maladaptive can have important benefits.”
For instance, males with strong and stable social bonds were less likely to get injured in fights, but they were more likely to become ill, the researchers found. Among females, social bonds tended to decrease illness overall, but this varied by group size. In smaller groups, social female gorillas didn’t often get sick, but they had fewer offspring. Friendly females that lived in larger groups had more offspring but also tended to become ill more often.
Being around more gorillas likely increases an individual’s risk of contracting a contagious disease. But the researchers suspect the explanation behind these trends may be more complicated than that: Males that live in larger groups, for example, might be using up more energy by defending their females and offspring, which could be weakening their immune systems.
Whatever the reasons, the findings suggest there’s no one-size-fits-all level of sociability for optimal health in mountain gorillas. Each primate might have its own ideal amount of integration and social bonds, determined by individual age, sex, offspring and context.
Gorillas with different interaction styles “can be successful in different ways,” says lead author Robin Morrison, a behavioral ecologist at the University of Zurich in Switzerland, to the Guardian’s Steven Morris.
“This paper highlights the incredible value of long-term studies to furthering our understanding of the evolution of sociality and how the benefits or costs of sociality can vary considerably across different environments,” says study co-author Tara Stoinski, president and CEO of the Dian Fossey Gorilla Fund, in the statement. Essentially, the consequences of an individual’s interaction style are “highly context dependent,” as the researchers write in the paper.
The same might be true for humans. The authors suggest their findings could help explain why humans and other social mammals have evolved different social strategies and preferences.
“Why are some people very social and others aren’t?” Morrison says to the Guardian. “It’s not as straightforward as saying ‘always be as social as possible.’ Actually, some individuals can do very well by having sort of a smaller number of close friends.”
