Polar bears (Ursus maritimus) use sea ice to access marine mammal prey. In Alaska’s Southern Beaufort Sea, the declining availability of sea ice habitat in summer and fall has reduced opportunities for polar bears to routinely hunt on the ice for seals, their primary prey. This reduced access to prey may result in physiological stress with subsequent potential consequences to reproductive function (physiological changes that accompany reproduction), which can be measured via reproductive hormones. Hormone concentrations in hair can be used as a minimally invasive alternative to serum concentrations, which must come from animal captures. Hair samples also provide a long-term average measurement of hormone concentrations that is not influenced by short-term fluctuations like that of serum. The aim of this study was (1) to determine if a radioimmunoassay could be used to measure adrenal and reproductive hormones in polar bear hair, and (2) to determine what the relationship is between these hormones and other reproductive, condition, and demographic parameters of polar bears. We successfully validated this method for cortisol, progesterone, estradiol, and testosterone through the analysis of hair and serum of 141 free-ranging polar bears. We found that while hair cannot be used to estimate serum hormone concentrations during the breeding season, hormone concentrations in hair can be used to measure reproductive function in polar bears. Further, our findings support trends in previous studies measuring hormone concentrations in serum. We found that adrenal and some reproductive hormones were positively correlated in hair samples of females. Associations between hormone concentrations in hair and serum did not vary relative to reproductive status of adult females. Serum testosterone increased throughout the breeding season for adult males and was significantly associated with body mass index (BMI). Our research supports the use of hair as a measure of reproductive function in polar bears and allows us to monitor the future effects of climate change on polar bear physiology.

北极熊 ( Ursus maritimus) 利用海冰接近海洋哺乳动物的猎物。在阿拉斯加的南博福特海，夏季和秋季海冰栖息地的可用性下降，减少了北极熊经常在冰上捕猎海豹的机会，海豹是它们的主要猎物。这种接近猎物的减少可能会导致生理压力，从而对生殖功能（伴随生殖的生理变化）产生潜在的后果，这可以通过生殖激素来衡量。头发中的激素浓度可以用作血清浓度的微创替代品，血清浓度必须来自动物捕获。头发样本还提供激素浓度的长期平均测量值，不受血清等短期波动的影响。本研究的目的是 (1) 确定放射免疫测定是否可用于测量北极熊毛发中的肾上腺和生殖激素，以及 (2) 确定这些激素与其他生殖、状况和人口统计参数之间的关系北极熊。我们通过分析 141 只自由放养的北极熊的毛发和血清，成功验证了这种用于皮质醇、孕酮、雌二醇和睾酮的方法。我们发现，虽然毛发不能用于估计繁殖季节的血清激素浓度，但毛发中的激素浓度可用于测量北极熊的生殖功能。此外，我们的研究结果支持先前测量血清中激素浓度的研究的趋势。我们发现肾上腺和一些生殖激素在女性头发样本中呈正相关。头发和血清中激素浓度之间的关联并没有随成年女性的生殖状况而变化。成年雄性的血清睾酮在整个繁殖季节都在增加，并且与体重指数（BMI）显着相关。我们的研究支持使用毛发来衡量北极熊的生殖功能，并使我们能够监测气候变化对北极熊生理学的未来影响。