Having lots of friends might seem like a win-win, but that’s not always the case if you’re a gorilla.
A new study in Proceedings of the National Academy of Sciences reveals that sociability can be both good and bad for a gorilla’s health, with the outcome depending on an individual’s circumstances.
Gorillas live in family groups that can range in size from a few to a few dozen individuals. Each group includes one or two adult males, multiple adult females, and their offspring.
To see how their social lives affected their health, scientists studied over two decades-worth of data on 164 mountain gorillas living in the Volcanoes National Park in Rwanda.
Sociability came with pros and cons, they found, and these changed depending on the size of groups, and whether the animal was male or female.
For example, males with strong social bonds tended to get ill more often but were less likely to be injured in fights.
Meanwhile, friendly females who lived in small groups didn’t get ill often but had fewer offspring, while those in larger groups had more ill health but had higher birth rates.
- Intimate photos show chimps using insects as medicine to treat each other's wounds in Gabon
- 10 of the strongest animals in the world
“Having a lot of strong social relationships is often really good – but sometimes it isn’t,” says Robin Morrison from the University of Zurich, who led the research. Sometimes traits previously thought of as maladaptive, such as having fewer social ties, can actually be helpful.
The reasons for this are unclear, but it’s more complex than just more social contact leading to more disease risk.
Instead, it’s possible that males expend more energy by having close social ties, as they have to defend females and offspring, and the stress of this may weaken their immune system.
And females living in bigger groups may have poorer immune function but manage more offspring because there are others around to help find resources and assist with childcare.
The study zoomed in on the strength of each gorilla’s key social bonds, and its integration in the group, along with wider context such as group size, stability and conflict with other groups.
“With these forces pushing in different directions, the ‘optimal’ social type will depend on an individual’s sex, age, offspring and wider social group,” says Sam Ellis from the University of Exter, who was also involved in the study.
In humans and other social animals, the social environment is one of the strongest predictors of health and lifespan. This research helps to explain why such a wide range of traits have evolved in social animals.
Main image: A family of mountain gorillas resting together, in Volcanoes National Park, Rwanda. Resting in physical contact is an indicator of close social relationships and tolerance in gorillas. Credit: Dian Fossey Gorilla Fund
More wildlife stories from around the world
- This 'karaoke queen' uses its song to fend off rival mates from vicious nest vandalism
- “Unbelievable thing to see”: drone captures never-seen-before footage of penguin chicks plunging 50 feet into Antarctic Ocean
- It's nicknamed the 'bearcat', smells like popcorn and lives in trees – meet the baffling binturong
- Giant 'phantom' animal filmed swimming over the seafloor in Antarctica
