"Peaceful" bonobos are actually more aggressive than chimps 

Chimpanzees and bonobos, often viewed as embodying contrasting aspects of human nature – the aggressive chimpanzee and the peaceful bonobo – exhibit more nuanced behaviors within their communities, according to a recent study led by Boston University. 

The experts found that male bonobos become aggressive more frequently than male chimpanzees, challenging prevailing perceptions. Notably, for both species, increased aggression correlates with more mating opportunities.

Aggressive behavior of chimpanzees and bonobos 

“Chimpanzees and bonobos use aggression in different ways for specific reasons,” said study lead author Maud Mouginot, an anthropologist at Boston University. “The idea is not to invalidate the image of bonobos being peaceful – the idea is that there is a lot more complexity in both species.”

This study is the first of its kind to directly compare the aggressive behaviors of bonobos and chimpanzees using consistent field methods. The research focused on male aggression, typically linked to reproductive behaviors, while recognizing that female aggression in both species also deserves further research.

Monitoring aggression in male bonobos

The scientists examined male aggression within three bonobo communities at the Kokolopori Bonobo Reserve in the Democratic Republic of Congo and two chimpanzee communities at Gombe National Park in Tanzania. They tracked 12 bonobos and 14 chimpanzees, conducting “focal follows” to monitor each individual’s interactions throughout the day.

“You go to their nests and wait for them to wake up and then you just follow them the entire day – from the moment they wake up to the moment they go to sleep at night – and record everything they do,” Mouginot explained.

Surprisingly, the study found that male bonobos were more frequently aggressive than their chimpanzee counterparts, engaging in 2.8 times more aggressive interactions and three times as many physical aggressions. Bonobo aggression was primarily directed at other males, whereas chimpanzees more often targeted females and were more likely to form coalitions during conflicts.

The infrequency of chimpanzee aggression 

The researchers suggest that the infrequency of chimpanzee aggression might be attributed to the potential for severe injuries and the weakening of group defenses against external threats, given that their conflicts often involve multiple males. In contrast, bonobos, who are not known to be territorial and have never been observed to kill each other, tend to have one-on-one disputes, avoiding broader community impacts.

For both species, males displaying higher levels of aggression achieved greater reproductive success. This was particularly unexpected in bonobos, where the social structure is co-dominant, and females typically outrank males – different from the male-dominated hierarchies of chimpanzees.

Broader implications of the study

“Male bonobos that are more aggressive obtain more copulations with females, which is something that we would not expect,” said Mouginot. “It means that females do not necessarily go for nicer males.”

These findings challenge the self-domesticating hypothesis, which posits that aggression has been selectively reduced in bonobos and humans compared to chimpanzees.

While the study did not measure the severity of the aggressive interactions in terms of resulting wounds or injuries, the researchers hope to include such data in future analyses. They also aim to expand their comparisons to include other groups of chimpanzees and bonobos to better understand behavioral variations within and across communities and subspecies.

More about bonobos 

Bonobos, also known scientifically as Pan paniscus, are one of our closest living relatives in the animal kingdom, sharing around 98% of our DNA. They are a species of great ape found only in the Congo Basin in the Democratic Republic of Congo. Bonobos are often noted for their matriarchal society, where females hold significant social status and power within their communities.

Physically, bonobos are slightly smaller and more slender than their relatives, the chimpanzees. They have black faces with pink lips, small ears, and long hair that parts in the middle. Bonobos use sexual behavior as a means to manage social relationships and conflicts, making them unique among primates.

Bonobos are frugivorous but their diet can also include other plant parts as well as small animals and insects. They are highly intelligent and capable of empathy, cooperation, and self-recognition in mirrors.

Unfortunately, bonobos are endangered due to habitat loss, human encroachment, and poaching. Conservation efforts are crucial to their survival, aiming to protect their natural habitat and reduce illegal hunting.

The study is published in the journal Current Biology.

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