Data from: Individual aggression, but not winner-loser effects, predicts social rank in male domestic fowl

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, has rarely been studied. Here, we investigate these questions using male domestic fowl. We matched males for body size, comb size, and aggression in pair-wise duels to: 1) study the effect of contest outcome on aggression and 2) 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 and decreased after losing. Nevertheless, such winner–loser effects were 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 2, 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.

诸多因素可影响个体获得高社会等级的概率，涵盖体型、争斗武器以及攻击性等行为特质。近期的胜负经历同样会影响个体在后续争斗中获胜的概率，这一现象通常被称为“胜负效应（winner–loser effects）”。个体的行为往往存在稳定的个体差异，攻击性亦在此列，由此体现出人格层面的差异。然而，目前鲜有研究探讨近期经历与人格特质在决定社会等级中的相对重要性，以及胜负经历对攻击性的影响程度。本研究以家鸡公鸡为实验对象，对上述问题展开探究。我们通过成对决斗对公鸡的体型、鸡冠大小以及攻击性进行匹配，以此达成两个研究目标：其一，探究争斗结果对攻击性的影响；其二，对比个体攻击性与争斗经历对小型群体中未来社会等级的影响。研究结果显示，攻击性属于高度可重复的人格特质，且获胜后攻击性会提升，失败后则会下降。尽管如此，这类胜负效应并不足以提升个体在小型群体中成为优势个体的几率。相较而言，争斗经历前测得的攻击性能够最佳预测个体未来的社会等级。大胆性与探索性均无法预测社会等级，且在这两项特质中，仅大胆性与攻击性呈正相关。综上，对于表型匹配的家鸡公鸡群体间的争斗而言，相较于胜负效应或其他人格特质，攻击性对个体获取高社会等级的作用更为显著。