Eavesdropping and the audience effect in fighting fruit flies reveal feedback between social information use and production

Abstract

Social information use and production occur simultaneously during social learning events; however, these two processes are often studied independently. We propose that social information use and production represent a feedback loop: eavesdroppers influence the behaviors of those being observed, which then alters the eavesdroppers social decisions. Here, we used Drosophila melanogaster to investigate the relationship between social information use and production in an aggressive context. We tested whether paired males altered their aggression when they were observed by (i) a male; (ii) a female, or; (iii) no one. Next, we allowed each individual eavesdropper to interact with the paired males that they just observed, and measured their social behaviors. In addition, we tested how naive flies responded when interacting with paired males. We found that paired males reduced their aggression when observed by a male, representing a change in social information production. In response, male eavesdroppers were overall less aggressive towards the more aggressive of the paired males they had observed, but their response to social information was also modulated by their genotype. In contrast, female eavesdroppers did not elicit changes to the behavior of the paired males, nor did we find evidence that they used the social information collected to make mating decisions. Overall, we found support for the feedback loop in males, but not females: information was exchanged bi-directionally during eavesdropping events, resulting in the modification of behavior by all parties. Utilizing the social information feedback framework can contribute to a better understanding of how social behaviors and animal communication are expressed and evolve. Competing InterestsNone Significance StatementAnimals often observe the social interactions that occur between others, but the effects of both watching and being watched on behavior are rarely studied together. Using a novel approach, we studied how an audience influenced and learned from an aggressive contest in fruit flies. A male audience caused contest participants to decrease their aggression, and the male who was watching later showed decreased aggression toward the contest winner. Surprisingly, we did not see any effect of a female audience on male-male aggression, and females later behavior was not altered by observing a contest. Together, these results show how observing a fight led to changes in both the behavior of the contest participants and the male audience, thus suppressing group levels of aggressive behavior. Accounting for this interaction between social information use and production is necessary to understand social behaviors.