The winner and loser effect: What fighting behaviours are influenced?

We examined the effect of prior winning and losing experiences on the initiating and responding strategies of contestants in contests between individuals of Rivulus marmoratus (Cyprinodontidae). Each contestant was given a penultimate and a recent fighting experience approximately 48 and 24 h prior to the dyadic contests, respectively, through randomly selected procedures. Winning and losing experience appeared to influence different types of fighting behaviours. Losing experiences decreased the probability of an individual initiating a confrontation and thus increased its tendency to retreat immediately when challenged. Winning experiences did not affect the probability of initiation, but significantly increased the likelihood of an individual initiating with attacks that effectively deterred its opponents. A substantial proportion (59/153) of individuals retreated immediately when challenged and reduced the number of fights available for examining experience effects on responding strategies at later stages of a contest. None the less, winning experiences consistently increased the likelihood of an individual retaliating by attacking its opponent at various stages of a contest, and eventually increased its probability of escalating a confrontation into physical fights. However, the effects of losing experiences on these responding strategies were undetectable. Recent experiences significantly affected all fighting behaviours examined, but penultimate experiences significantly affected only the tendency to initiate a confrontation with attacks and the likelihood of escalation. These results indicated that prior experiences had the longest lasting effect on the potentially most costly fighting behaviour. Prior experiences influenced the outcome of nonescalated contests as well as the probability of escalation, but did not significantly affect the outcome of escalated contests. These results are consistent with the hypothesis that prior experiences modify the information that an individual has about its fighting ability but do not alter its actual fighting ability and that actual fighting ability becomes the more important influence on outcomes of escalated contests.