Context dependent fitness costs of reproduction despite stable body mass costs in an Arctic herbivore

1. The cost of reproduction on demographic rates is often assumed to operate through changing body condition. Several studies have found that reproduction depresses body mass more if the current conditions are severe, such as high population densities or adverse weather, than under benign environmental conditions. However, few studies have investigated the association between the fitness and body mass costs of reproduction. 2. Using 25 years of individual-based capture-recapture data from Svalbard reindeer (Rangifer tarandus platyrhynchus), we built a novel Bayesian state-space model that jointly estimated inter-annual change in mass, annual reproductive success, and survival, while accounting for incomplete observations. The model allowed us to partition the differential effects of intrinsic and extrinsic factors on both non-reproductive mass change and the body mass cost of reproduction and to quantify their consequences on demographic rates. 3. Contrary to our expectation, the ...1. 繁殖对种群统计速率的代价通常被认为通过改变身体状况（body condition）来发挥作用。多项研究已证实，当当前环境条件严苛（如高种群密度或恶劣天气）时，繁殖对体重的抑制效应相较于温和环境条件下更为显著。然而，鲜有研究探讨繁殖的适合度（fitness）代价与体重代价之间的关联。 2. 本研究依托斯瓦尔巴德驯鹿（Rangifer tarandus platyrhynchus）长达25年的个体重捕（capture-recapture）标识数据，构建了一种新颖的贝叶斯状态空间模型（Bayesian state-space model），该模型可联合估计体重的年际变化、年度繁殖成功率与存活率，同时校正不完全观测（incomplete observations）带来的偏差。该模型使我们能够拆解内源与外源因素对非繁殖性体重变化以及繁殖相关体重代价的差异化影响，并量化其对种群统计速率的作用效应。 3. 与我们的预期相悖的是，……