Female bonobos kill a male, challenging beliefs about species' peaceful nature

No one has seen Hugo since February 18, 2025. That afternoon, around 3:30 p.m., a commotion erupted in the Salonga jungle in the Democratic Republic of Congo. Two minutes later, the first human witness arrived and started recording. Five females — Polly, Tao, Ngola, Djulie, and Bella — were attacking this nearly 20-year-old male, who lay face down on the ground.

The assault lasted 25 excruciating minutes for Hugo, who tried to cover his head while the entire clan watched without intervening, including some of his relatives.

“The females jumped alternatingly on Hugo’s body, stomping on his back and biting his head, legs, neck, fingers and toes. One female bit off a part of Hugo’s ear, two others engaged in genito-genital rubbing with each other on top of him. One of the perpetrators bit into his foot and chewed on the removed tissue, then bit his testes,” the scientists who documented the case describe in detail.

Hugo’s face was disfigured, his lips and eyebrows were bleeding, a large section of skin had been torn from his neck, his knuckles were bitten down to the bone, and he suffered severe injuries to his genitals. He barely managed to escape two hours later.

“He’s still missing, and we’re pretty sure he didn’t survive,” says Sonya Pashchevskaya, a primatologist and direct witness of an attack that highlights the complex realities of a species often idealized as erotic, playful hippies: the bonobos.

Hugo’s story helps illuminate the evolutionary mosaic of great apes: humans, orangutans, gorillas, chimpanzees, and bonobos. The last two species, closest to us, serve as a sort of mirror. Male chimpanzees maintain strict hierarchies and form long-lasting bonds with each other, while using violence against females to secure offspring. Bonobos, by contrast, live in a matriarchy: females dominate the group through alliances, reinforced by behaviors such as mutual genital rubbing, which is largely about pleasure.

The moment when the female bonobos attacked the male, captured on video by scientists.Sonya Pashchevskaya

Ever since Jane Goodall witnessed the brutal wars among chimpanzees, bonobos have often been idealized as the pacifist mirror image, especially following the popular books of Frans de Waal. “Although it’s true that they are much more peaceful,” says Pashchevskaya, “the hippie image of bonobo society largely comes from captive populations.” Wild bonobos are less idyllic, as this researcher from the Max Planck Institute in Germany explains. “The peaceful bonobo society, which is maintained by females assuming dominance over males, can occasionally be interrupted by extreme events like this, which would be the exception that proves the rule.”

Males are larger and stronger, yet it is the females who wield violence as a tool of social control. Perhaps that is why it has gone largely unnoticed. “It reflects a very male-centric view,” admits Martin Surbeck, from Harvard University, who has also worked with the bonobos of Lui Kotale, in Salonga National Park, but did not participate in this study. Surbeck published a study in April that reviews 30 years of observations to understand the power of bonobo females. Eighty-five percent of violent coalitions are led by females seeking to keep males in check, demonstrating that their ferocity is clearly functional: to prevent them from becoming like chimpanzees. In some communities, females win 100% of conflicts, showing that their dominance is structural.

Social power, not physical strength

“The power of these female coalitions is one of the main mechanisms that reverses the power dynamics between the sexes within bonobo groups,” Surbeck added via email. When female bonobos form aggressive alliances to exert social control over males, they demonstrate that power can be derived not from physical strength, but also from social support.

This is where the attack by the five females on Hugo begins to make sense. According to primatologists monitoring this community, a couple of days earlier, Hugo had acted aggressively toward the infant of the youngest attacker, Bella (15 years old). Infanticide is a common male strategy in many species to ensure reproductive success: a male fathers offspring once the female is no longer caring for the children she had with others.

“Bonobo females, however, have managed to reverse this trend, which chimpanzees do, thanks to an unusual cooperation between them,” explains Pashchevskaya, “and they even attack males who misbehave with their young.” “Extreme violence would be better explained as a response to the extreme threat: infanticide,” summarizes the lead author of the case now detailed in Current Biology.

A similar case occurred years ago, but it was less well documented. The primatologist notes that they can only speculate about the motives: “Why doesn’t infanticide occur within the group among bonobos? Because this is what happens if a male tries it.” If females are capable of such a violent act against an adult male, the scientist continues, perhaps that is precisely what keeps male aggression like that of chimpanzees at bay.

Nahoko Tokuyama, another expert on female bonobos, says she was “very surprised” by the episode. “Although they sometimes become violent, I thought female bonobos wouldn’t injure an opponent so seriously,” she says. “I think Hugo provoked the females particularly severely. Aggression against an infant constitutes a serious violation of bonobo society norms and almost always provokes retaliation from the females,” adds Tokuyama, from Tokyo Central University, who is the author of several studies on wild bonobo coalitions. “This case certainly represents the most violent attack ever documented in bonobos,” she concludes.

Injured genitals

Experts are cautious about the symbolism of the more gruesome details, such as Hugo’s genital injuries. Male chimpanzees attacking males from other groups often target the genitals to eliminate reproductive competition.

“They’re an easy area to damage when you’re just using teeth and hands, so it would be wise not to attribute too much symbolic meaning,” says Pashchevskaya. “Perhaps it communicates something like ‘don’t overstep your bounds.’”

The genital rubbing by the females over the attacked male is more typical behavior. Female bonobos use it frequently to weave social bonds, forming the backbone of their matriarchal network. “They also do it when they meet again after a while, as a kind of ‘hello, nice to see you,’” Pashchevskaya points out.

Liza Moscovice, author of several studies on female bonobos and their sexual behavior, elaborates: “It’s common in tense situations, such as during coalition attacks. Genital rubbing helps females coordinate their behavior, confirm mutual support, and possibly reduce stress in tense moments.”

Tokuyama indicates that “they were probably trying both to relieve stress and reaffirm their cooperative bond with each other.”

“In short, in this case,” says Pashchevskaya, “genital rubbing facilitates cooperation: ‘I’m with you on this.’”

Sign up for our weekly newsletter to get more English-language news coverage from EL PAÍS USA Edition