Scientists at UC Berkeley discovered that chimpanzees are less likely to steal fruit from their close friends compared to less-bonded peers, and their emotional responses differ depending on the strength of their social ties.
- Chimps steal 9% less from friends versus non-friends
- Victims calm down faster when theft comes from a friend
- Thieves show less hostility when stealing from bonded partners
What happened
UC Berkeley researchers studied the behavior of 26 chimpanzees living at the Ngamba Island Chimpanzee Sanctuary in Uganda. By observing grooming, proximity, and interactions, the team identified closely bonded chimp pairs they classified as friends. The scientists then set up an experiment where one chimp could steal pineapple from another through a rope mechanism linking two rooms.
The results showed that chimps were less likely to steal pineapple pieces from their friends—61% of trials—with non-friends being stolen from in 70% of trials. Additionally, researchers recorded emotional reactions: victims showed less prolonged anger when the thief was a friend, and thieves exhibited reduced hostility when stealing from a closely bonded chimp compared to a non-friend.
Why it feels good
This study enriches our understanding of social emotions and cooperation not only in humans but through our evolutionary relatives. The findings suggest that chimpanzees, like humans, possess social norms and expectations that govern their interactions with close companions. These expectations likely strengthen collaborative relationships essential for survival and well-being.
According to lead author Oded Ritov, the presence of mutual emotional moderation and restraint during conflicts indicates that strong social bonds come with unspoken agreements and considerations. This capacity to regulate behavior within friendships deepens the idea that aspects of human morality and friendship have roots shared with other primates.
What to enjoy or watch next
For those curious about the evolution of social behavior, this study opens doors to exploring how other animals manage friendships and moral-like expectations. Following results from UC Berkeley’s Social Origins Lab might reveal even more about the emotional life of animals and its connection to human social norms.
Meanwhile, animal lovers and science enthusiasts can enjoy documentaries or books on primate behavior that highlight the complexity of chimpanzee relationships, such as their cooperative problem solving and emotional communication. These narratives offer a warm and enlightening view into the rich inner lives of our closest animal relatives.