Abstract Social life is profitable, but it facilitates conflicts over resources and creates interdependence between individuals. Separating highly social animals triggers intense reactions aimed at re‐establishing lost connections. Less is known, however, about behavioural and physiological responses to separation in socially facultative species, where individuals temporarily form groups and may subsequently leave them. Non‐breeding common ravens (Corvus corax) gather in large numbers at feeding and roosting sites, but otherwise spend time seemingly solitary or in small subgroups. We here studied how ravens cope with being socially isolated, and investigated the life characteristics that might explain potential individual differences. For this, we individually separated captive subadult ravens (n = 25) and housed them in physical and visual isolation from their group members across 4 d. During the separation period, we collected behavioural data and measured the amount of immunoreactive corticosterone metabolites from bird droppings to assess the ravens’ physiological stress response. We found behavioural indicators of stress at the start of the separation, when ravens showed higher levels of tension than of comfort – a pattern that reversed at the end of the separation. Furthermore, we found that the upbringing of ravens affected their behaviour during separation. Hand‐raised birds produced more vocalisations in the beginning of the separation, and were less active at the end, while the reverse pattern occurred with parent‐raised ravens. Contrary to our predictions, we did not find differences in hormonal responses between the beginning and end of the separation period or any link between hormonal responses and behaviours. Ravens’ behavioural responses to social separation stress seem to be dependent on their arousal states, although possible links with hormonal reactions remain unclear. Our results show that behavioural reactions are not always linked with hormonal responses to stress, and further emphasise the importance of investigating effects of early‐life experiences.

中文翻译：

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乌鸦、乌鸦座对社会分离的行为和荷尔蒙应激反应

摘要 社交生活是有利可图的，但它会促进资源冲突并造成个人之间的相互依赖。分离高度社会化的动物会引发强烈的反应，旨在重建失去的联系。然而，关于社会兼性物种分离的行为和生理反应知之甚少，在这些物种中，个体暂时形成群体，随后可能离开它们。非繁殖性的普通乌鸦（Corvus corax）大量聚集在觅食和栖息地，但除此之外，它们似乎是孤独的或成群结队的。我们在这里研究了乌鸦如何应对社会孤立，并研究了可能解释潜在个体差异的生活特征。为了这，我们将圈养的亚成年乌鸦（n = 25）单独分开，并在 4 d 内将它们与群体成员进行物理和视觉隔离。在分离期间，我们收集了行为数据并测量了来自鸟粪的免疫反应性皮质酮代谢物的量，以评估乌鸦的生理应激反应。我们在分离开始时发现了压力的行为指标，当时乌鸦表现出的紧张程度高于舒适度——这种模式在分离结束时逆转。此外，我们发现乌鸦的养育影响了它们在分离过程中的行为。人工饲养的鸟类在分离开始时会发出更多的声音，而在分离结束时则不太活跃，而父母饲养的乌鸦则相反。与我们的预测相反，我们没有发现分离期开始和结束之间激素反应的差异，也没有发现激素反应和行为之间的任何联系。乌鸦对社会分离压力的行为反应似乎取决于它们的唤醒状态，尽管与荷尔蒙反应的可能联系尚不清楚。我们的结果表明，行为反应并不总是与荷尔蒙对压力的反应有关，并进一步强调了调查早期生活经历影响的重要性。