Data from: Glucocorticoids negatively relate to body mass on the short-term in a free-ranging ungulate

Environmental fluctuations force animals to adjust glucocorticoids (GCs) secretion and release to current conditions. GCs are a widely used proxy of an individual stress level. While short-term elevation in GCs is arguably beneficial for fitness components, previous studies have documented that the relationship between long-term baseline GCs elevation and fitness components can vary according to ecological and individual factors and according to the life-history of the species studied. Using longitudinal data on roe deer (Capreolus capreolus) from two populations facing markedly different environmental contexts, we tested whether baseline GC levels negatively correlate with body mass – a trait positively associated with demographic individual performance – on the short- to long-term. In support, higher baseline GC concentrations were associated to lighter body mass, both measured during the same capture event, in adults of both populations. Overall, we showed that despite the marked environmental and demographic differences between populations and despite the between-sex differences in life history (i.e. reproductive tactics), the relationship between body mass and GCs is consistent across environmental contexts, but might differ according to the life history stage of an individual. This work opens promising perspectives to further explore the relationship between GC and fitness-related traits according to life history stages in free-ranging mammals across seasonal and environmental contexts. The timing and context-dependence of GC levels highlight the complexity of studying stress responses in the wild.

环境波动会迫使动物调整糖皮质激素（glucocorticoids, GCs）的分泌与释放，以适配当下的生存环境。糖皮质激素是衡量个体应激水平的常用替代指标。尽管短期糖皮质激素水平升高对个体适合度组分往往具有益处，但既往研究表明，长期基础糖皮质激素水平升高与适合度组分之间的关联，会因生态因素、个体因素以及所研究物种的生活史特征而异。本研究利用两个环境背景差异显著的狍（Capreolus capreolus）种群的纵向监测数据，检验了短至长期尺度下基础糖皮质激素水平是否与体重呈负相关——体重是与个体种群统计表现呈正相关的性状。研究结果支持该假设：两个种群的成年个体中，基础糖皮质激素浓度更高的个体体重普遍更轻，且两项指标均采集于同一次捕获事件中。总体而言，本研究证实，尽管两个种群间存在显著的环境与种群统计差异，且两性间的生活史特征（即繁殖策略）存在分化，但体重与糖皮质激素之间的关联在不同环境背景下均保持稳定，不过会因个体所处的生活史阶段不同而产生差异。本研究为后续探索野生哺乳动物中，基于生活史阶段、结合季节与环境背景来研究糖皮质激素与适合度相关性状之间的关联，提供了颇具前景的研究视角。糖皮质激素水平的时间依赖性与背景依赖性，凸显了野外应激反应研究的复杂性。