Overview
- Researchers tracked 3,243 aggressive incidents among 22 groups at 16 European zoos, observing only apes older than seven years.
- There was no overall species-level difference in aggression rates, but patterns diverged: chimp aggression was mainly male-led toward both sexes, whereas in bonobos both sexes aggressed, mostly against males.
- Female-to-male aggression was pronounced in bonobos, reflecting their female-dominant social structure, while male-to-female aggression was more common in chimpanzees.
- Aggression varied widely within species, with bonobo groups exhibiting both the highest and lowest levels recorded, underscoring strong group-level effects.
- The authors say the captive setting limits broad conclusions and call for corroborating studies in wild populations, noting the findings complicate simple accounts of bonobo self-domestication and suggest aggression was present in the shared ancestor of humans, chimps and bonobos.