Polar bears are inefficient predators of seabird eggs

Climate-mediated sea-ice loss is disrupting the foraging ecology of polar
bears (Ursus maritimus) across much of their range. As a result, there
have been increased reports of polar bears foraging on seabird eggs across
parts of their range. Given that polar bears have evolved to hunt
seals on ice, they may not be efficient predators of seabird eggs. We
investigated bears’ foraging performance on common eider
(Somateria mollissima) eggs on Mitivik Island, Nunavut,
Canada to test whether bear decision-making heuristics are
consistent with expectations of optimal foraging theory. Using
aerial-drones, we recorded multiple foraging bouts over
eleven days, and found that as clutches were depleted to
completion, bears did not exhibit foraging behaviours matched to resource
density. Bears visited fewer nests overall as the season
progressed, but marginally increased their visitation to
nests that were already empty. Bears did not display different
movement modes related to nest density, but became less selective
in their choice of clutches to consume. Lastly, bears that
capitalized on visual cues of flushing eider hens
significantly increased the number of clutches they consumed;
however, they did not use this strategy consistently or
universally. The foraging behaviours exhibited by polar bears in this
study suggest they are inefficient predators of seabird eggs, particularly
in the context of matching behaviours to resource density.