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National Geographic
24-04-2025
- Science
- National Geographic
How female bonobos team up to gain power over males
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!
New York Times
24-04-2025
- Science
- New York Times
These Apes Are Matriarchal, but It Doesn't Mean They're Peaceful
Male domination is the natural order of things, some people say. But bonobos, primates with whom we share nearly 99 percent of our DNA, beg to differ. Bonobos are great apes that live in female-dominated societies, a relative rarity among mammals, especially in species where males are the larger sex. While females are smaller than their male counterparts, they reign supreme in bonobo societies. Scientists have long wondered how female bonobos maintain their matriarchies. In a study, published Thursday in the journal Communications Biology, researchers who tracked six bonobo communities in the Democratic Republic of Congo over nearly 30 years provided the first evidence-based explanation for how female bonobos gain and sustain dominance over the males within their communities. Females, they found, form coalitions against males to tip the balance of power in their favor. When a male bonobo steps out of line, nearby females will band together to attack or intimidate him. Males who cower in the face of such conflicts lose social rank, while their female adversaries gain it, affording them better access to food, and mates for their sons. Bonobos and chimpanzees are our closest living relatives. They were once thought to be a slightly smaller and darker-skinned subspecies of chimpanzee, but scientists determined nearly a century ago that they are separate species. These endangered apes, found only in the Democratic Republic of Congo, are difficult to study in the wild. To conduct this study, Martin Surbeck, a behavioral ecologist at Harvard University, and other scientists spent thousands of hours trudging through dense jungles. 'You get up around three o'clock in the morning, then walk for an hour or two to find the site where they built their nests the previous night,' Dr. Surbeck said. 'And then you follow the group for the whole day till they make their nests again.' It's known among primatologists that bonobos make a lot of love in addition to war. They carry out rather heavy petting, make sex toys and engage in homosexual intercourse. With their sexual activity and lower levels of violence compared with chimpanzees, the idea that bonobos are the hippies of the ape world is pervasive. However, observations by Dr. Surbeck and his team, and those of other researchers, challenge the harmonious stereotyping of these primates. 'Bonobos are not as peaceful as people might think,' said Maud Mouginot, an anthropologist at Boston University who was not involved in the current study. That includes conflict between the sexes. From 1993 to 2021, the researchers observed 1,786 instances of a male starting beef with a female. Examples included acting aggressively toward a female or her infant, or monopolizing food. In roughly 61 percent of these fights, the female teamed up with other females and emerged victorious. Such conflicts 'can be very severe,' Dr. Surbeck said. 'On a few occasions, we suspect that the male died as a result of the attack.' Males have been known to lose fingers and toes in such conflicts. In one unfortunate incident, a male bonobo in the Stuttgart Zoo in Germany had his penis bit in half during a battle with two females. A surgeon was able to sew it back together. Drawing on all the data they gathered, Dr. Surbeck and his team tested several hypotheses for how females maintain power in bonobo society. After crunching the numbers, the only one the team found evidence to support was one researchers call the 'female coalition hypothesis,' which suggests that females work together to overpower males during conflicts, resulting in higher social ranks for the winning females. The average female bonobo, the researchers found, outranks approximately 70 percent of the males in her community. Dr. Mouginot said what Dr. Surbeck and his colleagues found affirms what scientists like her have suspected for decades about the source of female power in bonobo society. 'For people who've been in the field with bonobos, it's not that surprising — but it's really nice to have actual quantitative data from different bonobos communities,' she said. Scientists are just beginning to scratch the surface when it comes to what lessons may be drawn from bonobos, Dr. Surbeck said, so protecting them is important. 'Bonobos are an endangered species,' he said. 'As our closest living relative, they help us look into our past. If we lose them, we lose a mirror for humanity. ' But for him, the study also supports the idea that male dominance is not a biological inevitability. 'While some people might think that patriarchy and male dominance are somehow an evolutionary trait in our species, that's really not the case,' Dr. Surbeck said.
