Mechanisms of decision making during contests in green anole lizards: prior experience and assessment

Prior contest experiences can predictably alter an individualʹs contest performance and probability of contest success. Although winner and loser effects have been well studied across many animal taxa, the mechanisms underlying these effects and their adaptive value currently are topics of intense interest. Two predominant hypotheses posit that contest experiences alter either an individualʹs perceived fighting ability or its actual fighting ability. We addressed these hypotheses, and potential physiological and behavioural mechanisms driving experience effects in the green anole lizard, Anolis carolinensis. Prior losers went on to lose a significant proportion of future contests while prior winners were equally likely to win or lose against size-matched opponents. Further analysis revealed that the loser effect arose as a result of individuals updating their perceived fighting ability following a loss. Both prior losing and winning experiences influenced future contest performance with prior losers decreasing and prior winners increasing their aggressiveness in subsequent contests. Status-dependent changes in metabolic physiology were not associated with the presence of the observed loser effect. However, contest status and contest performance interacted to influence metabolic physiology. Plasma glucose concentrations decreased as a function of the frequency of high-risk, escalated behaviours performed by eventual losers, and muscle lactate concentrations increased as a function of the frequency of low-risk threat displays performed by eventual winners. Our results support the notion that prior contest experiences influence an individualʹs perceived, not actual, fighting ability and that status-dependent changes in metabolic physiology are not a likely mechanism underlying the presence/magnitude of experience effects.