Uniting against a common enemy: Perceived outgroup threat elicits ingroup cohesion in chimpanzees

Research output: Journal contributionsJournal articlesResearchpeer-review

Authors

  • James Brooks
  • Ena Onishi
  • Isabelle R. Clark
  • Manuel Bohn
  • Shinya Yamamoto

Outgroup threat has been identified as an important driver of ingroup cohesion in humans, but the evolutionary origin of such a relationship is unclear. Chimpanzees (Pan troglodytes) in the wild are notably aggressive towards outgroup members but coordinate complex behaviors with many individuals in group hunting and border patrols. One hypothesis claims that these behaviors evolve alongside one another, where outgroup threat selects for ingroup cohesion and group coordination. To test this hypothesis, 5 groups of chimpanzees (N = 29 individuals) were observed after hearing either pant-hoots of unfamiliar wild chimpanzees or control crow vocalizations both in their typical daily environment and in a context of induced feeding competition. We observed a behavioral pattern that was consistent both with increased stress and vigilance (self-directed behaviors increased, play decreased, rest decreased) and increased ingroup cohesion (interindividual proximity decreased, aggression over food decreased, and play during feeding competition increased). These results support the hypothesis that outgroup threat elicits ingroup tolerance in chimpanzees. This suggests that in chimpanzees, like humans, competition between groups fosters group cohesion.

Original languageEnglish
Article numbere0246869
JournalPLoS ONE
Volume16
Issue number2
Number of pages17
ISSN1932-6203
DOIs
Publication statusPublished - 24.02.2021
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2021 Brooks et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

    Research areas

  • Psychology - chimpanzees, Agression, Vocalization, Animal sociality, Vigilance, Food, Animal behavior, Human evolution