Despite increasing empirical evidence demonstrating that the variation in behaviour at the individual level plays a key role in ecology and evolution, the proximate mechanisms leading to these individual differences are not yet fully understood. There is especially a paucity of data on wild populations of large mammals such as fallow deer Dama dama (image © Crispin Rodwell). In Amin et al.’s study, “In utero accumulated steroids predict neonate anti-predator response in a wild mammal” (Funct Ecol. 2021;35:1255–1267. https://doi.org/10.1111/1365-2435.13790), the authors found that neonate fallow deer fawns (age 1-14 days old) exhibit striking and repeatable individual differences in how they cope with an adverse situation similar to a predator attack, i.e. human capture and handling. Amin and colleagues illustrate how these differences in neonate behaviour are predicted by in utero accumulated levels of cortisol and testosterone, suggesting that the in utero environment may be involved in shaping early individuality in wild large mammals.

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尽管越来越多的经验证据表明个体水平的行为变化在生态学和进化中起着关键作用，但导致这些个体差异的直接机制尚未完全了解。尤其缺乏大型哺乳动物野生种群的数据，例如小鹿Dama dama（图片 © Crispin Rodwell）。在 Amin 等人的研究中，“子宫内积累的类固醇可预测野生哺乳动物的新生儿抗捕食者反应”（Funct Ecol. 2021;35:1255–1267. https://doi.org/10.1111/1365-2435.13790 )，作者发现新生的小鹿小鹿（1-14 天大）在如何应对类似于捕食者攻击的不利情况（即人类捕获和处理）方面表现出惊人且可重复的个体差异。Amin 及其同事说明了如何通过子宫内积累的皮质醇和睾酮水平来预测新生儿行为的这些差异，这表明子宫内环境可能与野生大型哺乳动物的早期个性形成有关。