Galicia Melissa P, Thiemann Gregory W, Dyck Markus G, Ferguson Steven H, Higdon Jeff W
Department of Biology York University Toronto Ontario M3J 1P3 Canada.
Faculty of Environmental Studies York University Toronto Ontario M3J 1P3 Canada.
Ecol Evol. 2016 Jul 28;6(16):6005-18. doi: 10.1002/ece3.2173. eCollection 2016 Aug.
Polar bear (Ursus maritimus) subpopulations in several areas with seasonal sea ice regimes have shown declines in body condition, reproductive rates, or abundance as a result of declining sea ice habitat. In the Foxe Basin region of Nunavut, Canada, the size of the polar bear subpopulation has remained largely stable over the past 20 years, despite concurrent declines in sea ice habitat. We used fatty acid analysis to examine polar bear feeding habits in Foxe Basin and thus potentially identify ecological factors contributing to population stability. Adipose tissue samples were collected from 103 polar bears harvested during 2010-2012. Polar bear diet composition varied spatially within the region with ringed seal (Pusa hispida) comprising the primary prey in northern and southern Foxe Basin, whereas polar bears in Hudson Strait consumed equal proportions of ringed seal and harp seal (Pagophilus groenlandicus). Walrus (Odobenus rosmarus) consumption was highest in northern Foxe Basin, a trend driven by the ability of adult male bears to capture large-bodied prey. Importantly, bowhead whale (Balaena mysticetus) contributed to polar bear diets in all areas and all age and sex classes. Bowhead carcasses resulting from killer whale (Orcinus orca) predation and subsistence harvest potentially provide an important supplementary food source for polar bears during the ice-free period. Our results suggest that the increasing abundance of killer whales and bowhead whales in the region could be indirectly contributing to improved polar bear foraging success despite declining sea ice habitat. However, this indirect interaction between top predators may be temporary if continued sea ice declines eventually severely limit on-ice feeding opportunities for polar bears.
在几个具有季节性海冰状况的地区，北极熊（Ursus maritimus）亚种群由于海冰栖息地减少，身体状况、繁殖率或数量出现了下降。在加拿大努纳武特地区的福克斯盆地，尽管海冰栖息地同时减少，但北极熊亚种群的规模在过去20年里基本保持稳定。我们利用脂肪酸分析来研究福克斯盆地北极熊的觅食习性，从而有可能确定有助于种群稳定的生态因素。从2010年至2012年期间捕获的103只北极熊身上采集了脂肪组织样本。该地区内北极熊的饮食组成在空间上存在差异，环斑海豹（Pusa hispida）是福克斯盆地北部和南部的主要猎物，而哈德逊海峡的北极熊消耗的环斑海豹和格陵兰海豹（Pagophilus groenlandicus）比例相当。海象（Odobenus rosmarus）的消耗量在福克斯盆地北部最高，这一趋势是由成年雄性北极熊捕获大体型猎物的能力推动的。重要的是，北极露脊鲸（Balaena mysticetus）在所有区域以及所有年龄和性别类别的北极熊饮食中都有贡献。虎鲸（Orcinus orca）捕食和生存捕猎导致的北极露脊鲸尸体，可能在无冰期为北极熊提供重要的补充食物来源。我们的结果表明，尽管海冰栖息地减少，但该地区虎鲸和北极露脊鲸数量的增加可能间接有助于北极熊觅食成功率的提高。然而，如果海冰持续减少最终严重限制北极熊在冰上的觅食机会，这种顶级捕食者之间的间接相互作用可能是暂时的。
