Charapata Patrick, Horstmann Lara, Misarti Nicole
College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, PO Box 757220, Fairbanks, AK 99775, USA.
Department of Biology, Baylor University, One Bear Place, Waco, TX 76706, USA.
Conserv Physiol. 2021 Jan 19;9(1):coaa135. doi: 10.1093/conphys/coaa135. eCollection 2021.
The Pacific walrus () 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, = 0.75). Cortisol concentrations were weakly correlated with a 15-year average September Chukchi Sea ice cover ( = 0.002, 0.02, = 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 ( < 0.001). Progesterone in females and testosterone in males exhibited significant correlations with average September Chukchi Sea ice cover for years 1880-2016 ( < 0.001 for both, = 0.34, 0.22, respectively). Modern walruses had significantly lower ( = < 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.
太平洋海象（）是北极标志性的海洋哺乳动物，对许多阿拉斯加原住民来说是一项重要资源。海冰栖息地的减少以及种群数量不明引发了人们对海象种群未来长期健康状况的担忧。目前尚不清楚北极生态系统变化会如何影响海象的生理机能。在本研究中，分析了在考古时期（距今3585 - 200年前（BP））、历史时期（公元1880 - 2006年（CE））和现代时期（公元2014 - 2016年（CE））收集的海象骨骼中的类固醇激素浓度（孕酮、睾酮、皮质醇和雌二醇），这些时期跨越约3651年，以追踪生殖活动和皮质醇浓度（应激生物标志物）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（38.94 ± 296.17 ng/g脂质， = 0.75）相似。皮质醇浓度与楚科奇海9月海冰覆盖面积的15年平均值呈弱相关（雌性和雄性的分别为 = 0.002，0.02， = 0.09，0.04），这表明北极海冰消退可能对其生理机能具有一定的恢复能力。所有类固醇激素与1960年至2016年海象种群平均估计数量均呈显著负相关（ < 0.001）。雌性的孕酮和雄性的睾酮与1880 - 2016年9月楚科奇海平均海冰覆盖面积呈显著相关（两者均 < 0.001，分别为 = 0.34，0.22）。与种群快速增长时期的历史海象相比，现代海象的生殖激素浓度显著更低（ = < 0.001），这表明该种群可能已达到承载能力。这是第一项将骨骼作为工具来监测可能与海象种群规模和海冰覆盖变化相关的激素长期变化的研究。
