Fighting investment of Neolamprologus pulcher after receiving single, reinforcing, and contradictory contest experiences

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 ..., Neolamprologus pulcher were purchased from Old World Exotic Fish, Inc. in Miami, FL in December 2018, or were F1 offspring of these fish. Contestants were housed in well-established social groups that maintained consistent group membership for at least two years prior to the start of this experiment. No contestant/opponent pair had been housed together or in adjacent tanks for at least two years prior to this experiment to reduce the effects of familiarity. Two weeks prior to the first contest trial, each fish was measured for total length (TL, to the nearest 0.01 mm), standard length (SL, to the nearest 0.01 mm), and mass (to the nearest 0.001 g). Each fish also was sexed by examination of the external genital papilla (Stiver et al. 2005) and received a unique visible implant elastomer tag (a subcutaneous injection of a silicone-based colored liquid) (Jungwirth et al. 2019) at this time. Only sexually mature animals (more than 30 mm in length) (Hellmann, Ligocki, et al. 2015; Antunes a..., All statistical analyses were performed using R 4.1.1. We used the car and emmeans statistical packages and RStudio.,