title: Out-Group Threat Promotes Within-Group Affiliation in a Cooperative Fish.
abstract: 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.
authors.forename: Rick
authors.initials: R
authors.lastname: Bruintjes
authors.forename: Joshua
authors.initials: J
authors.lastname: Lynton-Jenkins
authors.forename: Joseph W
authors.initials: JW
authors.lastname: Jones
authors.forename: Andrew N
authors.initials: AN
authors.lastname: Radford
mesh_terms: D000374:Aggression; D000818:Animals; D023681:Cichlids / Q000502:physiology*; D012919:Social Behavior; D013731:Territoriality
keywords: cooperation; intergroup conflict; postconflict behavior; signaling; sociality; territorial intrusions