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Cited by 393Primate Behavior and EcologyAnimal Behavior and ReproductionEvolutionary Psychology and Human Behavior

BOUNDARY PATROLS AND INTERGROUP ENCOUNTERS IN WILD CHIMPANZEES

Watts, David, Mitani, John·2001·Behaviour
DOI 10.1163/15685390152032488
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Abstract

Chimpanzees are among the few mammals that engage in lethal coalitionary aggression between groups. Most attacks on neighbors occur when parties made up mostly of adult males patrol boundaries of their community's range. Patrols have time, energy, and opportunity costs, and entail some risks despite the tendency of males to attack only when they greatly outnumber their targets. These factors may lead to a collective action problem. Potential benefits include protection of community members, particularly infants; range expansion and increases in the amount and quality of food available; and incorporation of more females into the community. Males may not share these equally; for example, those able to obtain large shares of matings may stand to gain most by participating in patrols and to lose most by refraining. Despite the attention that boundary patrolling has attracted, few relevant quantitative data are available. Here, we present detailed data on boundary patrolling and intergroup aggression in a chimpanzee community at Ngogo, Kibale National Park, Uganda, that is unusually large and has more males than any other known community. Males there patrolled much more often, and patrol parties were much larger on average, than at two other sites for which comparative data exist. Our findings support the argument that male participation varies along with variation in potential gains, in willingness to take risks, and in skill at handling these risks. Both the overall frequency with which individual males patrolled and their willingness to join patrols as others set off on them were positively associated with variation in mating success, in participation in hunts of red colobus monkeys, and in hunting success. Males patrolled relatively often with others with whom they associated often in general, with whom they often groomed, and with whom they formed coalitions in withincommunity agonism. This indicates that they were most willing to take risks associated with patrolling when with others they trusted to take the same risks.

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Crossref · 10.1163/15685390152032488

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Authors
Watts, D., & Mitani, J.
Affiliations
  • Yale University (US)
  • University of Michigan (US)
ORCID
Venue
Behaviour
Publisher
Walter de Gruyter GmbH
Published
2001
Volume
138
Issue
3
Pages
299-327
ISSN
  • 0005-7959 (ISSN-L)
  • 1568-539X
DOI
10.1163/15685390152032488
OpenAlex
W2124915716
Cited by
393
References
46
Citations by year
2026: 7 · 2025: 11 · 2024: 21 · 2023: 49 · 2022: 19 · 2021: 22 · 2020: 16 · 2019: 14 · 2018: 10 · 2017: 12 · 2016: 19 · 2015: 17 · 2014: 20 · 2013: 17 · 2012: 17
FWCI
12.63
Type
journal article
Language
en
Open access
closed
Locations
  • Behaviour (publishedVersion)
  • Deep Blue (University of Michigan) (submittedVersion)
Topics
  • Social Sciences › Psychology › Social Psychology › Primate Behavior and Ecology
  • Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Animal Behavior and Reproduction
  • Social Sciences › Psychology › Experimental and Cognitive Psychology › Evolutionary Psychology and Human Behavior
Keywords
chimpanzees, intergroup aggression, collective action problems, male cooperation, risk sharing, mating success, hunting success, red colobus, grooming, social bonds

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