Data for: Molt timing and duration of northern elephant seals

Life history timing influences many ecosystem processes including predator-prey interactions, information transfer, disease transmission, ecosystem services, and resource subsidies. Many animals and plants have species-typical annual cycles, but individuals vary in their exact timing of life history events. However, quantifying individual variation in the timing and duration of life history events requires longitudinal sampling and may necessitate advanced analytical techniques if observations are imperfect or asynchrony is prevalent. Our goal was to examine factors that influence variation in molt duration and timing across individual northern elephant seals (Mirounga angustirostris). We quantified the onset and progression of fur loss in 1,178 individual seals over seven years. We found a wide range of molt start dates (95% interval spanning 60.1 days within a single age-sex category) and rapid molt progression (6.0 days in adult females and 10.8 and 10.3 days in juvenile females and males, respectively) with high molt asynchrony (only 20% of individuals in the population molting at the same time). Individual variation in the timing of the molt within age-sex categories was much larger than between categories: 94% of the variation in haul-out duration, 74% of variation in molt start date, and 59% of variation in molt duration was among individuals within age-sex categories. Finally, we discovered that individuals arriving late for the molt spent less time on the beach than earlier arrivers, which allowed them to catch up if they fell behind in their annual cycles. These findings emphasize the importance of quantifying individual variation in critical life history events.

生活史时序（life history timing）会影响诸多生态过程，涵盖捕食者-猎物相互作用、信息传递、疾病传播、生态系统服务与资源补贴。许多动植物均具有物种特有的年度生活周期，但不同个体的生活史事件具体发生时序存在差异。然而，量化生活史事件发生时序与持续时长的个体差异，需要开展纵向采样；若观测数据存在缺陷或种群内异步性普遍存在，则需借助高级分析技术。本研究旨在探究影响北象海豹（Mirounga angustirostris）个体换羽时长与时序差异的相关因素。我们针对1178头北象海豹个体开展了为期7年的监测，量化了其毛皮脱落的起始与进展过程。研究发现，换羽起始日期跨度极大（单一年龄-性别类群内的95%区间跨度达60.1天），且换羽进展迅速：成年雌性个体换羽耗时6.0天，幼年雌性与雄性个体分别耗时10.8天与10.3天；同时种群换羽异步性极高，仅20%的个体同步换羽。年龄-性别类群内部个体间的换羽时序差异，远大于类群间差异：上岸停留时长（haul-out duration）变异的94%、换羽起始日期变异的74%以及换羽时长变异的59%，均来自类群内的个体差异。最后我们发现，换羽抵达时间较晚的个体，在海滩停留的时长短于早到个体，这使得它们能够在年度生活周期中弥补进度滞后的情况。本研究结果凸显了量化关键生活史事件个体差异的重要性。