Aggressiveness as a component of fighting ability in pigs using a game-theoretical framework Highlights
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The personality trait aggressiveness was studied as a component of fighting ability.
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Between size-matched pigs more aggressive individuals were not more likely to win.
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Aggressiveness did not affect fighting ability but did alter contest behaviour.
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Aggressiveness may form an honest signal of intent but dishonest signal of ability.
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There was no evidence that aggressiveness was part of an assessment strategy.
________________________________________Understanding animal contests has benefited greatly from employing the concept of fighting ability, termed resource-holding potential (RHP), with body size/weight typically used as a proxy. However, victory does not always go to the larger/heavier contestant and the existing RHP approach thereby fails to accurately predict contest outcome. Aggressiveness, typically studied as a personality trait, might explain part of this discrepancy. We investigated whether aggressiveness forms a component of RHP, examining effects on contest outcome, duration and phases, plus physiological measures of costs (lactate and glucose). Furthermore, using the correct theoretical framework, we provide the first study to investigate whether individuals gather and use information on aggressiveness as part of an assessment strategy. Pigs, Sus scrofa, were assessed for aggressiveness in resident–intruder tests whereby attack latency reflects aggressiveness. Contests were then staged between size-matched animals diverging in aggressiveness. Individuals with a short attack latency in the resident–intruder test almost always initiated the first bite and fight in the subsequent contest