How female bonobos team up to gain power over males

National Geographic

24-04-2025

Why do female bonobos often outrank males, especially when the opposite is true for most social mammals, like their close relative the chimpanzee?
That's the question Martin Surbeck and his colleagues wanted to answer. And after monitoring six communities of bonobos in the Democratic Republic of the Congo for nearly three decades, they have arrived at a conclusion. The study measured 'rank' within the bonobo communities by tallying how many times females won conflicts with males. Females usually came out on top. Photograph by Christian Ziegler
By banding together in coalitions—meaning groups of two or more animals, but usually three to five—female bonobos both reduce the danger posed by males and catapult themselves into positions of influence. Fully 85 percent of cases of female coalitionary aggression were directed at males, which also tend to be larger than females.
'We have found what everybody already knows—that when you work together, you're more successful and you gain power,' says Surbeck, a behavioral ecologist at Harvard University and lead author of a study published today in the journal Communications Biology.
'In bonobo communities, females have a lot to say. And that's very different from chimpanzee communities where all adult males outrank all females in the group, and where sexually attractive females receive a lot of aggression…by the males,' says Surbeck.
The study makes use of 'an impressive data set' to provide 'an exciting new window into how female bonobos build and maintain power,' says Laura Simone Lewis, a biological anthropologist at the University of California, Berkeley, who was not affiliated with the research.
'As bonobos are our closest living relatives along with chimpanzees, these data also provide support for the idea that humans and our ancestors have likely used coalitions to build and maintain power for millions of years,' says Lewis. Two bonobos hold hands while grooming. Photograph By Mélodie Kreyer, LuiKotale Bonobo Project A female bonobo bares her teeth. The more that female bonobos backed each other in the study, the more they won individual fights and rose in rank. Photograph By Frans Lanting, Nat Geo Image Collection Njoki, a female bonobo, sits with her 2-year-old son. Photograph By Christian Ziegler, Nat Geo Image Collection
The six communities of bonobos observed for the study each showed different levels of female cooperation and dominance. 'There is substantial variation in this trait of female power within groups, and we found that coalition formation in females seems to explain a lot of the variation,' says Surbeck.
Surbeck and his colleagues measured 'rank' within the communities by tallying how many times females won conflicts with males, as well as by evaluating the percentage of males in a group that were outranked by females. For instance, while male chimpanzees are always dominant over females, female bonobos outranked 70 percent of the males in their communities. And all of this varied across sites and over time.
In 1998, the females of the Eyengo community never once backed down from or were outranked by a male, and the same was mostly true for the females in the Kokolopori group in 2020; they dominated 98.4 percent of conflicts with males. However, in a mysterious twist in the Ekalakala community, males were made to submit to females just 18.2 percent of the time in 2016. A group of female bonobos groom each other. The six communities of bonobos observed for the study each showed different levels of female cooperation and dominance. Photograph By Christian Ziegler
The difference between groups? When females gave each other backup at higher rates, they won individual conflicts and rose in rank.
Interestingly, males sometimes participated in the female coalitions against other males, but the scientists note that they never led the charge, so to speak. The formation of female coalitions also seemed to occur after different triggers at different sites. In a site known as Wamba, female bonobos teamed up after males acted aggressively toward mature females. However, in three other communities, coalitions formed in response to male aggression against offspring.
The females in these alliances were often unrelated, and they weren't necessarily already friends either.
'The degree of group variation in female coalitions and female power between bonobo communities was one of the most fascinating findings from this study,' says Zanna Clay, a primatologist and comparative psychologist at Durham University in the United Kingdom, who was not involved with the study. 'This challenges the 'one-size-fits-all' view of our closest cousins, and suggests that like us, they show fascinating nuance and important variation in their behavior and traits.' A mother bonobo looks after her baby. Photograph By Christian Ziegler
While no study of animals should be taken as a direct link to the complex factors at play in human society, bonobos and chimpanzees do offer insight into our evolutionary past. 'Women are often victims of male violence around the globe,' says Lewis. 'This study could provide insight into how women could build power to better protect ourselves from male violence by forming and maintaining coalitions, or alliances, with one another, just like our bonobo cousins.'
Surbeck agreed that there may be lessons for humans here.
'It tells us that male dominance and patriarchy is not evolutionarily inevitable,' he says. 'This reinforces the idea that apes and humans are very innovative and flexible in their behavior. If anything, I think we can say that it does give us some hope.' Discover More, Spend Less With new subscriber-exclusive stories published daily and complete archive access, your opportunities to explore are endless!