Abstract

The Pacific walrus (Odobenus rosmarus divergens) is an iconic Arctic marine mammal and an important resource to many Alaska Natives. A decrease in sea ice habitat and unknown population numbers has led to concern of the long-term future health of the walrus population. There is currently no clear understanding of how walrus physiology might be affected by a changing Arctic ecosystem. In this study, steroid hormone concentrations (progesterone, testosterone, cortisol and estradiol) were analysed in walrus bones collected during archaeological [3585–200 calendar years before present (BP)], historical [1880–2006 common era (CE)] and modern (2014–2016 CE) time periods, representing ~ 3651 years, to track changes in reproductive activity and cortisol concentrations (biomarker of stress) over time. Our results show that modern walrus samples have similar cortisol concentrations (median = 43.97 ± standard deviation 904.38 ng/g lipid) to archaeological walruses (38.94 ± 296.17 ng/g lipid, P = 0.75). Cortisol concentrations were weakly correlated with a 15-year average September Chukchi Sea ice cover (P = 0.002, 0.02, r² = 0.09, 0.04, for females and males, respectively), indicating a possible physiological resiliency to sea ice recession in the Arctic. All steroid hormones had significant negative correlations with mean walrus population estimates from 1960 to 2016 (P < 0.001). Progesterone in females and testosterone in males exhibited significant correlations with average September Chukchi Sea ice cover for years 1880–2016 (P < 0.001 for both, r2 = 0.34, 0.22, respectively). Modern walruses had significantly lower (P = < 0.001) reproductive hormone concentrations compared with historic walruses during times of rapid population increase, indicative of a population possibly at carrying capacity. This is the first study to apply bone as a tool to monitor long-term changes in hormones that may be associated with changes in walrus population size and sea ice cover.

中文翻译：

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三千年来收集的太平洋海象骨骼中的类固醇激素表明了对估计种群规模和环境变化的生理反应

摘要

太平洋海象（Odobenus rosmarus divergens）是一种标志性的北极海洋哺乳动物，也是许多阿拉斯加原住民的重要资源。海冰栖息地的减少和未知的种群数量引起了人们对海象种群未来长期健康的担忧。目前还不清楚北极生态系统的变化如何影响海象的生理机能。在这项研究中，分析了考古[距今3585-200历年（BP）]、历史[1880-2006公元（CE）]和现代收集的海象骨骼中的类固醇激素浓度（黄体酮、睾酮、皮质醇和雌二醇）。 （2014-2016 CE）时间段，代表约 3651 年，用于跟踪生殖活动和皮质醇浓度（压力生物标志物）随时间的变化。我们的结果表明，现代海象样本的皮质醇浓度（中位数 = 43.97 ± 标准差 904.38 ng/g 脂质）与考古海象相似（38.94 ± 296.17 ng/g 脂质，P = 0.75 ）  。皮质醇浓度与 15 年平均 9 月楚科奇海冰盖的相关性较弱（女性和男性分别为P  = 0.002、0.02、r ²  = 0.09、0.04），表明北极海冰退缩可能具有生理弹性。从 1960 年到 2016 年，所有类固醇激素与海象平均种群估计值均呈显着负相关（P  < 0.001）。女性黄体酮和男性睾酮与 1880-2016 年 9 月楚科奇海平均冰覆盖量表现出显着相关性（ 两者P < 0.001， r2 分别 = 0.34、0.22）。 在种群快速增长时期，现代海象的生殖激素浓度显着低于历史海象（P = < 0.001），这表明种群可能具有承载能力。这是第一项应用骨骼作为工具来监测激素长期变化的研究，这些变化可能与海象种群规模和海冰覆盖的变化有关。