Polar bears (Ursus maritimus) rely on sea ice for hunting marine mammal prey. Declining sea ice conditions associated with climate warming have negatively affected polar bears, especially in the southern portion of their range. At higher latitudes, the transition from multi-year ice to thinner annual ice has been hypothesized to increase biological productivity and potentially improve polar bear foraging conditions. To investigate this possibility, we used quantitative fatty acid signature analysis to characterize the diet composition of 148 polar bears in two high-latitude subpopulations from 2012 to 2014: (1) Viscount Melville Sound, where little is known about marine mammal ecology, and (2) Northern Beaufort Sea, a subpopulation considered stable with comparatively more ecological data. We used adipose tissue lipid content as an index of body condition. To characterize long-term habitat conditions, we examined trends in sea ice metrics from 1979 to 2014 in both regions. Although the diets of bears in both subpopulations were dominated by ringed seal (Pusa hispida, mean biomass consumption = 45%), bears in Viscount Melville Sound showed higher proportional consumption of beluga whale (Delphinapterus leucas; mean biomass consumption = 37%) than any other polar bear subpopulation studied to date. Although the three-year duration of our study precludes long-term insights, relatively lighter sea ice conditions in Viscount Melville Sound were associated with reduced consumption of preferred prey (i.e., ringed seal), especially among female polar bears. Further, polar bears in Viscount Melville sound were in poorer body condition than those in the Northern Beaufort Sea. Our results do not indicate that declining sea ice has had any positive effect on polar bear foraging at high-latitudes.

北极熊 ( Ursus maritimus) 依靠海冰捕猎海洋哺乳动物的猎物。与气候变暖相关的海冰条件下降对北极熊产生了负面影响，尤其是在其分布范围的南部。在高纬度地区，从多年冰层到更薄的年冰层的转变被认为会提高生物生产力并有可能改善北极熊的觅食条件。为了研究这种可能性，我们使用定量脂肪酸特征分析来表征 2012 年至 2014 年两个高纬度亚群中 148 只北极熊的饮食组成：（1）梅尔维尔湾子爵，那里对海洋哺乳动物生态知之甚少，以及（ 2）北波弗特海，一个被认为稳定的亚群，具有相对更多的生态数据。我们使用脂肪组织脂质含量作为身体状况的指标。为了表征长期栖息地条件，我们检查了两个地区 1979 年至 2014 年海冰指标的趋势。尽管两个亚种群中熊的饮食都以环斑海豹为主（Pusa hispida，平均生物量消耗 = 45%），梅尔维尔湾子爵的熊表现出比迄今为止研究的任何其他北极熊亚群更高的白鲸（Delphinapterus leucas；平均生物量消耗 = 37%）的比例消耗。尽管我们为期三年的研究排除了长期的洞察力，但梅尔维尔子爵湾相对较轻的海冰条件与首选猎物（即环斑海豹）的消费减少有关，尤其是在雌性北极熊中。此外，梅尔维尔子爵湾的北极熊的身体状况比北波弗特海的北极熊更差。我们的结果并未表明海冰减少对北极熊在高纬度地区的觅食有任何积极影响。