Fatty acid-based diet estimates suggest ringed seal remain the main prey of southern Beaufort Sea polar bears despite recent use of onshore food resources

Ecology and Evolution
By: , and 

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Abstract

Polar bears (Ursus maritimus) from the southern Beaufort Sea (SB) subpopulation have traditionally fed predominantly upon ice-seals; however, as the proportion of the subpopulation using onshore habitat has recently increased, foraging on land-based resources, including remains of subsistence-harvested bowhead whales (Balaena mysticetus) and colonial nesting seabirds has been observed. Adipose tissue samples were collected from this subpopulation during the springs of 2013-2016 and analyzed for fatty acid signatures. Diet estimates were generated for the proportional consumption of ringed seal (Pusa hispida), bearded seal (Erignathus barbatus), and beluga whale (Delphinapterus leucas), relative to onshore foods, including bowhead whale remains and seabird, as represented by black guillemot (Cepphus grylle mandtii) nestlings and eggs. Quantitative fatty acid signature analysis (QFASA) showed that the ice-obligate prey, ringed seal, remained the predominant prey species of SB polar bears (46.5 ± 1.2%), with much lower consumption of bearded seal (19.4 ± 2.0%), seabird (17.1 ± 1.2%), bowhead whale (15.0 ± 1.4%), and hardly any beluga whale (2.0 ± 0.5%). Adult and sub-adult females appeared to depend more on the traditional ringed seal prey than adult and sub-adult males. Diet estimates of SB polar bears showed significant inter-annual variability for all prey (F3,439 = 6.84, p < 0.001). The diet estimates suggested that both types of onshore prey, bowhead whale remains and seabird, have represented a moderate proportion of the food resources used by SB polar bears since at least the start of the 21st Century.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Fatty acid-based diet estimates suggest ringed seal remain the main prey of southern Beaufort Sea polar bears despite recent use of onshore food resources
Series title Ecology and Evolution
DOI 10.1002/ece3.6043
Edition Online First
Year Published 2020
Language English
Publisher Wiley
Contributing office(s) Alaska Science Center Biology MFEB
Country United States
State Alaska
Other Geospatial Southern Beaufort Sea