Crain Danielle D, Karpovich Shawna A, Quakenbush Lori, Polasek Lori
Department of Biology, Baylor University, Waco TX, 76706, USA.
Alaska Department of Fish and Game, 1300 College Road, Fairbanks, AK 99701, USA.
Conserv Physiol. 2021 Jan 6;9(1):coaa115. doi: 10.1093/conphys/coaa115. eCollection 2021.
Rapid climate warming is decreasing sea ice thickness, extent and duration. Marine mammals such as bearded () and ringed () seals, which use sea ice for pupping, molting and resting, may be negatively affected. Claws from bearded and ringed seals store up to 14 and 12 years of sequential analyte data, respectively. These data can be used to compare reproduction, stress and diet across decades. In this study, we compare progesterone, cortisol and carbon and nitrogen stable isotopes in female bearded and ringed seals during 1953-1968 (pre-1968, a period prior to sea ice decline) to 1998-2014 (post-1998, a period during sea ice decline). When comparing these periods, bearded seals had statistically higher cortisol concentrations post-1998, and for both species δC was more negative post-1998, while progesterone and δN did not change. There was a positive relationship between progesterone and cortisol Z-scores for both species, except for ringed seals post-1998. There was a negative relationship between cortisol Z-scores and δC for bearded seals evident in post-1998 indicating that higher cortisol Z-scores are associated with more negative δC in bearded seals in recent years. This negative relationship between cortisol and δC in bearded seals suggests a shift to higher prey diversity, possibly due to changes in sea ice in the Pacific Arctic evident post 1998. Progesterone Z-scores corresponded to expected differences among non-pregnant, unimplanted, implanted and post-partum individuals. Using these data, pregnancy history was determined for reproductive years for each individual female sampled, which could allow for yearly pregnancy rates to be calculated given a large enough representative sample of the population. These results combine decades of observational studies with hormones and stable isotopes to infer changes in reproduction, stress and diet, as well as the connection between these life history parameters.
气候迅速变暖正在降低海冰厚度、范围和持续时间。髯海豹和环斑海豹等海洋哺乳动物利用海冰进行产仔、蜕皮和休息，可能会受到负面影响。髯海豹和环斑海豹的爪子分别存储了长达14年和12年的连续分析物数据。这些数据可用于比较数十年间的繁殖、应激和饮食情况。在本研究中，我们比较了1953 - 1968年（1968年前，海冰减少之前的时期）至1998 - 2014年（1998年后，海冰减少期间）雌性髯海豹和环斑海豹体内的孕酮、皮质醇以及碳和氮稳定同位素。比较这两个时期时，髯海豹在1998年后皮质醇浓度在统计学上更高，并且两个物种的δC在1998年后都更负，而孕酮和δN没有变化。除了1998年后的环斑海豹外，两个物种的孕酮和皮质醇Z分数之间都存在正相关关系。1998年后髯海豹的皮质醇Z分数与δC之间存在负相关关系，这表明近年来髯海豹中较高的皮质醇Z分数与更负的δC相关。髯海豹中皮质醇与δC之间的这种负相关关系表明向更高的猎物多样性转变，这可能是由于1998年后太平洋北极地区海冰的变化所致。孕酮Z分数与未怀孕、未着床、着床和产后个体之间的预期差异相对应。利用这些数据，确定了每个采样雌性个体繁殖年份的怀孕史，在有足够大的种群代表性样本的情况下，可以计算出年度怀孕率。这些结果将数十年的观察研究与激素和稳定同位素相结合，以推断繁殖、应激和饮食的变化，以及这些生活史参数之间的联系。
