Out-Group Threat Promotes Within-Group Affiliation in a Cooperative Fish

R Bruintjes, Joshua Lynton-Jenkins, Joseph Jones, Andrew N Radford

Research output: Contribution to journalArticle (Academic Journal)peer-review

45 Citations (Scopus)
534 Downloads (Pure)


In social species, conflict with outsiders is predicted to affect within-group interactions and thus influence group dynamics and the evolution and maintenance of sociality. Although empirical evidence exists for a relationship between out-group conflict and intragroup behavior in humans, experimental tests in other animals are rare. In a model fish system, we show that simulated out-group intrusions cause postconflict increases in intragroup affiliation but no changes in postconflict intragroup aggression. Postconflict affiliation was greater following intrusions by neighboring compared with nonneighboring individuals; neighbors represent greater threats to the dominance rank and breeding success of residents, and they are visible in the aftermath of the intrusion. By providing strong evidence of a link between out-group conflict and postconflict intragroup behavior and demonstrating that intragroup affiliation is affected by the nature of the out-group intrusion, our study shows the importance of considering postconflict behavior for our understanding of cooperation and social structure.
Original languageEnglish
Pages (from-to)274-282
Number of pages9
JournalAmerican Naturalist
Issue number2
Early online date8 Dec 2015
Publication statusPublished - Feb 2016


  • cooperation
  • intergroup conflict
  • postconflict behavior
  • signaling
  • sociality
  • territorial intrusions


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