A new study says “hippie” bonobos are just as aggressive as “warrior” chimpanzees. But the findings also reveal some important details about which gender provokes aggression. Female bonobos tended to attack males, and male chimpanzees were more aggressive towards females. They found significantly lower female-to-female aggression in both species.
The study focused on animals kept in zoos, so it may not apply to bonobos or chimpanzees in the wild, but it adds to a growing body of recent research suggesting bonobos are not as peace-loving as once thought.
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Bonobos (Pan paniscus) and chimpanzees (Pan troglodytes) are our closest living relatives. The two species are separated geographically by the Congo River in Africa and evolved from a common ancestor between 1.5 and 2 million years ago.
Although chimpanzees and bonobos are closely related, they look and behave differently. Bonobos are small and slender, and the differences between males and females are less pronounced than chimpanzees. The bonobo community is led by a coalition of women. This is thought to be a strategy for females to gain power over larger males. Chimpanzees, on the other hand, have males at the top of the hierarchy.
Aggression is an important social behavior for great apes, helping them defend territory, identify mates, assert dominance, and secure resources. This aggression can range from vocal expressions of anger to physical attacks.
In the past, bonobos were considered chimpanzees’ peace-loving “hippie” cousins. This is because bonobos are not combative and were thought to be more likely to use sex to resolve conflicts. However, recent research is beginning to overturn that idea. In a recently reported incident, five wild female bonobos violently attacked a male in the Democratic Republic of the Congo.
In a new study published Wednesday (March 11) in the journal Science Advances, researchers showed that bonobos are just as aggressive as chimpanzees, but that males and females have different targets.
There is almost no difference in overall attack power.
The researchers analyzed how 22 groups of chimpanzees and bonobos based in European zoos interacted. Researchers sat in front of the enclosure and recorded any acts of aggression that occurred throughout the day, from screaming to physical violence. The researchers spent two to three months at each zoo, recording a total of 3,243 acts of aggression from all great apes over the age of seven. Seven years old is the youngest reproductive age for male bonobos that researchers have ever recorded, Stace said.
They found 1,368 instances of directed attacks from bonobos and 1,875 from chimpanzees. About a third of those attacks (1,193) were “touch” attacks. This means that there was physical violence between individuals, rather than simply screaming or other less violent forms of attack. When the data were controlled for gender, relationship, and context, there was little difference in overall aggression between chimpanzees and bonobos.
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“Chimpanzees are not more aggressive,” Stace said. “Bonobos are aggressive as well.” In the case of chimpanzees, males were primarily responsible for conflicts. Male and female bonobos, on the other hand, were equally likely to fight. “Bonobos have no gender differences, which was a bit of a surprise to us,” Stace said.
However, there were differences in which genders were targeted. Male chimpanzees were more aggressive toward both females and other males, and were more likely to use physical violence. Female bonobos were more likely to be aggressive toward male bonobos. According to Stace, bonobos exhibit some aggression between males, but very little aggression between females.
But bonobos are good at making up, she said, adding that the team plans to explain how different groups resolve conflicts in future studies.
There were also clear differences in levels of aggression between groups of bonobos in different zoos, more so than among chimpanzees. “Our findings contribute to a growing body of evidence suggesting that pan behavioral patterns, including aggression, may be more influenced by group identity than by species-wide traits,” the authors write.
Zoos provide an interesting perspective on great ape behavior. Some researchers argue that chimpanzees were more belligerent because food was scarce in the Congo River and they had to compete with gorillas for resources. Conversely, bonobos had more food and fewer predators.
In zoos, these environmental factors no longer matter. “The main advantage is that you can remove two species from their respective ecosystems and really understand, for example, behavioral differences due to genetic changes that have occurred since they were separated from each other,” Stace said.
Sonya Pashchevskaya, a behavioral ecologist at the Max Planck Institute for Animal Behavior in Germany who was not involved in the study, said she welcomed the new insights. “This study is particularly important given the ‘hippie’ concept of bonobos, which famously originates from captivity,” she told Live Science. “It’s great to see myths methodologically challenged in an environment like this, with multiple groups involved.”
“Attacks as a means of surviving conflicts are a normal part of life,” Pashchevskaya said. While chimpanzees are more prone to extreme violence, bonobos may “reserve true violence for the worst dangers.”
New insights into bonobo aggression could provide further clues about conflict between our closest relatives. Pashchevskaya said: “Conflict is inevitable, but there are a variety of offensive expressions for both men and women.”
Ross, T., Edwin, V.L., and Bryon, E. (2025). Replication data: Chimpanzees are less aggressive than bonobos, but have different gender targets. [Dataset]. At DataverseNL. https://doi.org/10.34894/c7vbhl
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