Data from: Dietary habits of polar bears in Foxe Basin, Canada: possible evidence of a trophic regime shift mediated by a new top predator

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.