Wasps Use Social Eavesdropping to Learn about Individual Rivals.

Many animals minimize the costs of conflict by using social eavesdropping to learn about the fighting ability of potential rivals before they interact. Learning about individual conspecifics via social eavesdropping allows individuals to assess potential opponents without personal risk. However, keeping track of a network of individually differentiated social relationships is thought to be cognitively challenging. Here, we test how Polistes fuscatus nest-founding queens use social eavesdropping to assess individual rivals. Bystanders watched conspecifics fight through a clear partition. Then, bystanders were allowed to interact with fighters. Bystander behavior toward fighters was strongly influenced by the observed fight; bystanders were less aggressive toward fighters that were seen to initiate more and receive less aggression. Control trials allow us to reject alternative explanations for the link between observed aggression and bystander behavior, including priming or winner/loser effects. Therefore, P. fuscatus wasps observe and remember a complex network of social interactions between individual conspecifics rather than only paying attention to individuals they interact with directly. Wasps have an impressive capacity to learn, remember, and make social deductions about individuals. These results indicate that insects can have surprisingly complex social lives involving a network of individually differentiated social relationships.