Predator avoidance can have immense impacts on fitness, yet individual variation in the expression of anti-predator behaviour remains largely unexplained. Existing research investigating learning of novel predators has focused either on individuals or groups, but not both. Testing in individual settings allows evaluations of learning or personality differences, while testing in group settings makes it impossible to distinguish any such individual differences from social dynamics. In this study, we investigate the effect of social dynamics on individual anti-predator behaviour. We trained 15 captive ravens to recognize and respond to a novel experimental predator and then exposed them to this predator in both group and isolation settings across 1.5 years to tease apart individual differences from social effects and evaluate two hypotheses: (1) weaker anti-predator responses of some individuals in the group occurred, because they failed to recognize the experimental predator as a threat, leading to weak responses when separated, or (2) some individuals had learned the new threat, but their scolding intensity was repressed in the group trials due to social dynamics (such as dominance rank), leading to increased scolding intensity when alone. We found that dominance significantly influences scolding behaviour in the group trials; top-ranked individuals scold more and earlier than lower ranking ones. However, in the separation trials scolding duration is no longer affected by rank. We speculate that, while top-ranked individuals use their anti-predator responses to signal status in the group, lower-ranking ravens may be suppressed from, or are less capable of, performing intense anti-predator behaviour while in the group. This suggests that, in addition to its recruitment or predator-deterrent effects, alarm calling may serve as a marker of individual quality to conspecifics.

中文翻译：

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社会动态影响圈养乌鸦 (Corvus corax) 群体的责骂行为

避免捕食者会对健康产生巨大影响，但反捕食者行为表达的个体差异在很大程度上仍未得到解释。现有的调查新捕食者学习的研究集中在个人或群体上，但不是两者兼而有之。在个人环境中进行测试可以评估学习或性格差异，而在群体环境中进行测试则无法将任何此类个体差异与社会动态区分开来。在这项研究中，我们调查了社会动态对个体反捕食者行为的影响。我们训练了 15 只圈养乌鸦来识别和响应一种新的实验性捕食者，然后在 1.5 年的时间里将它们在群体和隔离环境中暴露于这种捕食者，以梳理个体差异与社会影响并评估两个假设：(1) 群体中一些个体的反捕食者反应较弱，因为他们未能将实验性捕食者识别为威胁，导致分离时反应较弱，或者 (2) 一些个体已经了解了新的威胁，但他们的责骂由于社会动态（例如支配地位），强度在小组试验中受到抑制，导致单独时责骂强度增加。我们发现支配地位显着影响小组试验中的责骂行为；排名靠前的人比排名靠后的人骂得更多、更早。但是，在离职试炼中，责骂的持续时间不再受等级影响。我们推测，虽然排名靠前的乌鸦利用他们的反捕食者反应来表明群体中的地位，但排名较低的乌鸦可能会被抑制或能力较弱，在群体中执行强烈的反捕食者行为。这表明，除了其招募或捕食者威慑作用外，警报呼叫还可以作为个体质量的标志。