Data from: Onset of autumn shapes the timing of birth in Pyrenean chamois more than onset of spring

1. In seasonal environments, birth dates are a central component for a species’ life history, with potential long-term fitness consequences. Yet our understanding of selective pressures of environmental changes on birth dates is limited in wild mammals due to the difficulty of data collection. In a context of rapid climate change, the question of a possible mismatch between plant phenology and birth phenology also remains unanswered for most species. 2. We assessed whether and how the timing of birth in a mountain mammal (isard, Rupicapra pyrenaica) tracked changes in plant growing season, accounting for maternal traits, individual heterogeneity, and population density. We not only focused on spring conditions but also assessed to what extent onset of autumn can be a driver of phenological biological events and compared the magnitude of the response to the magnitude of the environmental changes. We relied on a 22-year study based on intensively monitored marked individuals of known age. 3. Births were highly synchronized (80% of kids born within 25 days) and highly repeatable (84%; among-females variation of 9.6 days, withinfemale variation of 4.2 days). Individual phenotypic plasticity allows females to respond rapidly to inter-annual changes in plant phenology but did not prevent the existence of a mismatch: a 10-day advance in the autumn or spring plant phenology led to 3.9 and 1.3 days advance in birth dates, respectively. 4. Our findings suggest that plant phenology may act as a cue to induce important stages of the reproductive cycle (e.g., conception and gestation length), subsequently affecting parturition dates, and stressed the importance of focusing on long-term changes during spring for which females may show much lower adaptive potential than during autumn. These results also question the extent to which individual plasticity along with high heterogeneity among individuals will allow species to cope with demographic consequences of climate changes.1. 在季节性环境中，繁殖日期是物种生活史的核心组成部分，会对适合度（fitness）产生潜在的长期影响。然而，由于数据收集难度较大，我们对于环境变化对野生哺乳动物繁殖日期的选择压力（selective pressures）的认知仍十分有限。在气候快速变化的背景下，多数物种的植物物候（plant phenology）与繁殖物候（birth phenology）之间是否存在错配，这一问题至今仍未得到解答。 2. 本研究以山地哺乳动物比利牛斯臆羚（isard, Rupicapra pyrenaica）为研究对象，评估了其繁殖时间是否以及如何追踪植物生长季的变化，同时考量了母体性状（maternal traits）、个体异质性（individual heterogeneity）以及种群密度（population density）的影响。本研究不仅关注春季环境条件，还探讨了秋季物候起始在多大程度上可作为物候相关生物事件的驱动因子，并将物种对环境变化的响应幅度与环境变化本身的幅度进行了对比。本研究依托一项为期22年的长期监测数据，该数据来自对已知年龄的标记个体的密集监测。 3. 该物种的繁殖行为具有高度同步性（80%的幼崽均在25天内出生）与高度可重复性（组内相关系数达84%；雌性个体间的繁殖日期变异幅度为9.6天，个体内变异幅度为4.2天）。雌性个体的表型可塑性（phenotypic plasticity）使其能够快速响应植物物候的年际变化（inter-annual changes），但这并未完全避免物候错配的发生：秋季或春季植物物候每提前10天，对应的繁殖日期分别会提前3.9天与1.3天。 4. 本研究结果表明，植物物候可作为信号触发繁殖周期的关键阶段（如受孕（conception）与妊娠期时长（gestation length）），进而影响分娩日期（parturition dates）；同时研究强调了关注春季长期环境变化的重要性——雌性个体在春季的适应潜力（adaptive potential）远低于秋季。此外，本研究结果也引发了新的疑问：个体表型可塑性与种群内极高的个体异质性，能否帮助物种应对气候变化带来的种群动态后果（demographic consequences）？