Many factors can affect the probability for an individual to obtain a high social rank, including size, weaponry, and behavioral attributes such as aggression. Recent experiences of winning or losing can also affect the chances of winning future contests, commonly referred to as 'winner-loser effects'. Individuals often differ in behavior in a consistent way, including in aggression, thereby showing differences in personality. However, the relative importance of recent experience and aspects of personality in determining rank, as well as the extent to which winning or losing affects aggression, have rarely been studied. Here we investigate these questions using male domestic fowl. We matched males for body size, comb size and aggression in pairwise duels to: A) study the effect of contest outcome on aggression, and B) compare the effect of individual aggression and contest experience on future social status in small groups. We found that aggression was a highly repeatable personality trait, and that aggression increased after winning, but remained unaffected after losing. Nevertheless, such a winner effect was not enough to increase the odds of becoming dominant in a small group. Instead, aggressiveness measured prior to a contest experience best predicted future rank. Boldness and exploration did not predict rank, and of the two, only boldness was positively correlated with aggressiveness. We conclude that for male domestic fowl in contests among phenotypically matched contestants, aggressiveness is more important for obtaining high rank than winner-loser effects, or other aspects of personality.
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