Association patterns among wild chimpanzees (Pan troglodytes schweinfurthii) reflect sex differences in cooperation

Ian C. Gilby, Richard W. Wrangham

Research output: Contribution to journalArticle

85 Scopus citations

Abstract

Theory predicts that frequent dyadic association should promote cooperation through kin selection or social tolerance. Here we test the hypothesis that sex differences in the strength and stability of association preferences among free-ranging chimpanzees conform to sex differences in cooperative behavior. Using long-term data from the Kanyawara chimpanzee (Pan troglodytes schweinfurthii) community (Kibale National Park, Uganda), we calculated indices of intra-sexual dyadic association over a 10-year period. We found that (1) male-male dyads had significantly stronger association indices than female-female dyads, (2) the pattern of association preferences in both sexes changed little over the entire study period, and (3) when comparing periods with different alpha males, changes in association strength were more frequent among males. These results demonstrate that both the strength and stability of association patterns are important components of social relationships. Male chimpanzees, which are characterized by frequent cooperation, had association preferences that were both strong and stable, suggesting that forming long-term bonds is an important dominance strategy. However, the fact that male association patterns were sensitive to upheaval in the male dominance hierarchy suggests that males also take advantage of a changing social climate when choosing association partners. By contrast, the overall strength of female associations was relatively weak. Female association preferences were equally stable as males'; however, this reflected a dyad's tendency to be found in the same party rather than to associate closely within that party. Therefore, in this community, female association patterns appear to be more a consequence of individual ranging behavior rather than a correlate of cooperation.

Original languageEnglish (US)
Pages (from-to)1831-1842
Number of pages12
JournalBehavioral Ecology and Sociobiology
Volume62
Issue number11
DOIs
StatePublished - Sep 1 2008
Externally publishedYes

Keywords

  • Alliance
  • Association patterns
  • Chimpanzee
  • Cooperation
  • Sex differences
  • Social bonds

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

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