Polar bear use of a persistent food subsidy: insights from non-invasive genetic sampling in Alaska

Ursus
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Abstract

Remains of bowhead whales (Balaena mysticetus) harvested by Iñupiat whalers are deposited in bone piles along the coast of Alaska and have become persistent and reliable food sources for polar bears (Ursus maritimus). The importance of bone piles to individuals and the population, the patterns of use, and the number, sex, and age of bears using these resources are poorly understood. We implemented barbed-wire hair snaring to obtain genetic identities from bears using the Point Barrow bone pile in winter 2010–11. Eighty-three percent of genotyped samples produced individual and sex identification. We identified 97 bears from 200 samples. Using genetic mark–recapture techniques, we estimated that 228 bears used the bone pile during November to February, which would represent approximately 15% of the Southern Beaufort Sea polar bear subpopulation, if all bears were from this subpopulation. We found that polar bears of all age and sex classes simultaneously used the bone pile. More males than females used the bone pile, and males predominated in February, likely because 1/3 of adult females would be denning during this period. On average, bears spent 10 days at the bone pile (median  =  5 days); the probability that an individual bear remained at the bone pile from week to week was 63% for females and 45% for males. Most bears in the sample were detected visiting the bone pile once or twice. We found some evidence of matrilineal fidelity to the bone pile, but the group of animals visiting the bone pile did not differ genetically from the Southern Beaufort Sea subpopulation, nor did patterns of relatedness. We demonstrate that bowhead whale bone piles may be an influential food subsidy for polar bears in the Barrow region in autumn and winter for all sex and age classes.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Polar bear use of a persistent food subsidy: insights from non-invasive genetic sampling in Alaska
Series title Ursus
DOI 10.2192/URSUS-D-12-00030.1
Volume 24
Issue 2
Year Published 2013
Language English
Publisher International Association for Bear Research and Management
Contributing office(s) Alaska Science Center Biology MFEB
Description 16 p.
First page 148
Last page 163
Country United States
State Alaska
Online Only (Y/N) N
Additional Online Files (Y/N) N
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