Interactions among performance capacities predict male combat outcomes in the field cricket

P>1. There is a growing appreciation that male fighting ability is influenced by multiple traits. In particular, studies of male combat have identified a variety of performance capacities that predict victory in conflicts between conspecifics in several animal species. However, while multiple aspects of male fighting ability are often examined with a single study, the interactions among traits are rarely considered. 2. We conducted fight trials between size-matched males in the black field cricket, Teleogryllus commodus, with the aim of testing how two whole-organism performance traits, jumping ability and bite force, together with weight at eclosion, interact to determine combat outcomes. We then examined the relationships between these traits and the outcome of a fight using: a univariate framework, where we examined the difference between winners and losers for each trait separately; and, a multivariate framework known as response surface analysis, where we examined how the interactions among traits predict the outcome of a fight. 3. We show that males that won fights tended to exert significantly more force when biting, but were neither better jumpers nor heavier at eclosion than their rivals. However, when we examined the effects of these three traits while statistically controlling for one another in a multiple regression, we showed that overall fighting ability depends not only on contributions of individual traits to contest resolution but also on the interactions among traits and their relationship to the capabilities of rival males. We found that the probability of winning was highest for a male with the greatest positive difference from his rival in the combination of bite force, jump power and weight at eclosion. 4. These findings highlight how studying multiple performance capabilities in isolation from each other may obscure the importance of some variables. Our multivariate analyses revealed that the interactions between multiple dimensions of performance are important in male combat. We discuss the broader implications of these findings, including the potential role of whole-organism performance in determining male quality.