Department of Behavioral and Cognitive Biology, University of Vienna, Vienna, Austria.
Arctic Centre, University of Groningen, Groningen, The Netherlands.
J Anim Ecol. 2021 Apr;90(4):809-819. doi: 10.1111/1365-2656.13411. Epub 2021 Jan 8.
Parental care, such as nest or offspring defence, is crucial for offspring survival in many species. Yet, despite its obvious fitness benefits, the level of defence can consistently vary between individuals of the same species. One prominent adaptive explanation for consistent individual differences in behaviours involves state dependency: relatively stable differences in individual state should lead to the emergence of repeatable behavioural variation whereas changes in state should lead to a readjustment of behaviour. Therefore, empirical testing of adaptive state dependence requires longitudinal data where behaviour and state of individuals of the same population are repeatedly measured. Here, we test if variation in states predicts nest defence behaviour (a 'risky' behaviour) in a long-lived species, the barnacle goose Branta leucopsis. Adaptive models have predicted that an individual's residual reproductive value or 'asset' is an important state variable underlying variation in risk-taking behaviour. Hence, we investigate how nest defence varies as a function of time of the season and individual age, two state variables that can vary between and within individuals and determine asset. Repeated measures of nest defence towards a human intruder (flight initiation distance or FID) of females of known age were collected during 15 breeding seasons. Increasing values of FID represent increasing shyness. We found that females strongly and consistently differed in FID within- and between-years. As predicted by theory, females adjusted their behaviour to state by decreasing their FID with season and age. Decomposing these population patterns into within- and between-individual effects showed that the state-dependent change in FID was driven by individual plasticity in FID and that bolder females were more plastic than shyer females. This study shows that nest defence behaviour differs consistently among individuals and is adjusted to individual state in a direction predicted by adaptive personality theory.
亲代照顾，如筑巢或保护后代，对许多物种的后代生存至关重要。然而，尽管它具有明显的适应优势，但同一物种个体之间的防御水平仍然存在差异。个体行为差异的一个突出的适应性解释涉及状态依存性：个体状态的相对稳定差异应该导致可重复的行为变异的出现，而状态的变化应该导致行为的重新调整。因此，适应性状态依存性的实证检验需要纵向数据，即在同一种群的个体的行为和状态被反复测量。在这里，我们测试了个体状态的变化是否可以预测一种长寿物种——凤头䴙䴘的巢防御行为（一种“冒险”行为）。适应性模型预测，个体的剩余繁殖价值或“资产”是冒险行为变化的一个重要状态变量。因此，我们调查了巢防御如何随着季节和个体年龄的变化而变化，这两个状态变量可以在个体之间和个体内部变化，并决定资产。我们在 15 个繁殖季节中，对已知年龄的雌性个体进行了多次针对人类入侵者的巢防御（飞行启动距离或 FID）的重复测量。FID 值越大，代表越害羞。我们发现，雌性个体在年内和年际之间的 FID 存在强烈且一致的差异。正如理论预测的那样，雌性个体通过随季节和年龄降低 FID 来调整其行为。将这些种群模式分解为个体内和个体间的效应表明，FID 的状态依赖性变化是由 FID 的个体可塑性驱动的，而更勇敢的雌性比更害羞的雌性具有更高的可塑性。这项研究表明，巢防御行为在个体之间存在明显差异，并根据适应性人格理论调整到个体状态。
