Bonobos may be more aggressive than chimpanzees – 04/16/2024 – Science

The reputation of bonobos or pygmy chimpanzees as pacifists (Pan paniscus), primates that are among the closest relatives of humans, appears to have been greatly exaggerated, indicates a new study. Observations conducted in two African countries showed that aggressive interactions between males of the species can be three times more frequent than those seen among common chimpanzees — apes typically portrayed as much more violent than bonobos.

Although the average severity of aggression still appears to be much lower among bonobos, the new data helps paint a more balanced portrait of the so-called “hippie apes”, says study coordinator Maud Mouginot, from Boston University.

“Chimpanzees and bonobos use aggression in different ways, for specific reasons. The idea is not to invalidate the image that bonobos are peaceful, but to show that there is much more complexity in both species,” says the anthropologist, whose work with colleagues from France and the USA has just been published in the specialized journal Current Biology.

The study was conducted in the Kokolopori Bonobo Reserve in the Democratic Republic of Congo and Gombe National Park in Tanzania. Instead of monitoring communities of both species as a whole, researchers adopted the focal monitoring method, in which primatologists choose an individual from the group to be the focus of their interest and closely tag the animal, following it. during all your activities throughout the day.

“We go to the monkeys’ nests, wait for them to wake up and then follow the individuals throughout the day, until the time they go to sleep, recording everything they do”, summarizes Mouginot.

For this, 12 bonobos (in Congo) and 14 chimpanzees (in Tanzania) were selected, aged over 12 years (that is, they were no longer “children” by the standards of these species). All individuals were males, as among great apes, males tend to have a greater association with aggressive behavior. In total, the monkeys were monitored for more than 2,000 hours of life in the forest.

When monitoring the animals, the researchers recorded both signs of aggression without physical contact (such as attacking a fellow species, the so-called “charging” or “cargo”, or chasing it) and moments in which the animals went to actually saw it. In both cases, aggressive behavior among male bonobos was about three times more frequent.

Interactions between the sexes give more clues about the differences between species. The researchers found that, while aggression committed by male bonobos against females is very rare (only 3% of recorded situations), male chimpanzees attack females frequently (32% of observed cases). The situation is reversed when females are the aggressors: among chimpanzees, they resort to violence in only 1.8% of observations, while in the case of bonobos, females are the aggressors in 15.5% of violent interactions.

All of this makes sense when you consider that the social hierarchies of each species are also inverted: among bonobos, females are dominant, while males dictate the rules in groups of chimpanzees. But there are more interesting details there.

In the case of bonobos, something that is almost never seen are alliances between males to give blows to one or more members of the group or neighboring groups, a practice that is common among chimpanzees. This is probably one of the explanations for the relatively frequent death of chimpanzees “in combat”, something that has not yet been recorded in the case of bonobos, and for the lesser severity of aggression in this species.

Finally, for males of both primates, aggressive behavior is correlated with an important advantage: sexual success. On average, more aggressive males copulate with females more frequently, something that was not expected in the case of bonobos.

It is not yet possible to know whether the data also applies to other communities of these species, as “cultural” differences sometimes influence these variables in the case of primates. It is something to be investigated in the future in other regions of Africa inhabited by the animals.