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Skilful fighting encompasses an individual's ability not only to perform agonistic behaviours accurately and efficiently, but also to choose the most appropriate behaviour or tactic from its repertoire based on the information available. The efficacy of different tactics may depend both on the behaviour of the opponent and on the individual's internal state, for example a specific behaviour may become less effective over time as fatigue sets in. Furthermore, because fights are dynamic interactions, the ability to choose the appropriate tactic will require rapid information processing and may thus be constrained by an individual's cognitive ability. Here, we conducted a three-phase experiment to investigate the effects of reduced performance capacity induced by exposure to hypoxia and decision-making speed on skilful fighting in the European hermit crab, Pagurus bernhardus. During fights attackers attempt to elicit an eviction either by rapping on the defender's shell or by rocking the defender's shell back and forth. By analysing the effect of exposure to hypoxia and decision-making speed on the relative use of these tactics, we show that contrary to our prediction, neither performance capacity nor decision-making speed alone predicted the type of behaviour performed. Rather, these two traits interacted to determine the amount of effort (raps and rocks) attackers needed to exert to elicit an eviction. Furthermore, we show that while neither performance capacity nor decision-making speed predicted skill when fights were analysed as a whole, the effects of these variables became apparent when analysing the change in accuracy as fights progressed, likely due to the accumulating effects of fatigue. • The performance of agonistic behaviours varies in terms of vigour and skill. • Vigour is linked to energetic status, but the underpinnings of skill are unknown. • We explore the effects of performance capacity and decision-making speed on skill. • We measure two aspects of skill, accuracy and appropriateness (choice of tactics). • We find that performance capacity and decision-making speed impact skill over time. [ABSTRACT FROM AUTHOR]

What attributes make some individuals more likely to win a fight than others? A range of morphological and physiological traits have been studied intensely but far less focus has been placed on the actual agonistic behaviours used. Current studies of agonistic behaviour focus on contest duration and the vigour of fighting. It also seems obvious that individuals that fight more skilfully should have a greater chance of winning a fight. Here, we discuss the meaning of skill in animal fights. As the activities of each opponent can be disrupted by the behaviour of their rival, we differentiate among ability, technique and skill itself. In addition to efficient, accurate and sometimes precise movement, skilful fighting also requires rapid decision-making, so that appropriate tactics and strategies are selected. We consider how these different components of skill could be acquired, through genes, experiences of play-fighting and of real fights. Skilful fighting can enhance resource holding potential (RHP) by allowing for sustained vigour, by inflicting greater costs on opponents and by minimizing the chance of damage. Therefore, we argue that skill is a neglected but important component of RHP that could be readily studied to provide new insights into the evolution of agonistic behaviour. [ABSTRACT FROM AUTHOR]

Theoretical models of injurious animal contests, such as the cumulative assessment model (CAM), predict that an individual's decision to give up and retreat from a fight is determined by reaching a maximum cost threshold ( C max ). Under this model, an individual gives up when the accumulated costs of persisting exceed this threshold. CAM predicts that the velocity with which C max is reached depends on both the energetic (physiological) costs of remaining in the fight and the damage costs of injuries received. Here we propose that damage costs are accumulated not only by receiving injuries, but in some cases also by inflicting injury (attacking). We argue that these self-inflicted damage costs need to be incorporated into theoretical frameworks to fully understand what drives an individual to make the decision to give up, and we call for further research into this area. [ABSTRACT FROM AUTHOR]