Cumulative experience influences contest investment in a social fish

When animals live in long-term groups, the potential for conflict is high. Conflict is costly, so an individual’s decision to engage depends on the information it has about the costs and benefits of fighting. One source of information could be past contest experience, where previous winners/losers typically become more likely to win/lose in the future. However, repeated interactions can familiarize individuals with conflict and provide opportunities to learn to become better fighters, regardless of outcome. We explored how individuals integrate information from previous contests to inform future encounters in a group-living fish, Neolamprologus pulcher. We gave contestants single, reinforcing, and contradictory experiences and measured behavior and post-fight water-borne levels of androgenic steroids (testosterone, 11-ketotestosterone). Contradictory outcomes were associated with reduced investment in fighting. More fighting experience did not lead to greater investment in fighting, as consecutive losses resulted in reduced aggression. Also, there was no effect of fighting treatment on water-borne androgen concentrations. Interestingly, there were sex differences in which behaviors were influenced by experience, and in whether body mass was associated with androgen concentrations, which could indicate that males and females vary in how perceived fighting ability changes with contest experience. Our data reveal the complex ways in which repeated experiences can alter an individual’s propensity to invest in conflict. Repeated interactions associated with predictable changes in behavior can contribute to rank stability in groups and our results indicate that whether and how they do depend on the quality and quantity of interactions plus individual factors such as sex.