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ESR 36:1-14 (2018)  -  DOI:

Changes in winter and spring resource selection by polar bears Ursus maritimus in Baffin Bay over two decades of sea-ice loss

Kristin L. Laidre1,2,*, Harry Stern1, Erik W. Born2, Patrick Heagerty3, Stephen Atkinson4, Øystein Wiig5, Nicholas J. Lunn6, Eric V. Regehr1, Richard McGovern1, Markus Dyck4

1Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA 98105, USA
2Greenland Institute of Natural Resources, PO Box 570, Nuuk 3900, Greenland
3Department of Biostatistics, University of Washington, Seattle, WA 98195, USA
4Wildlife Research Section, Department of Environment, Government of Nunavut, PO Box 209, Igloolik, Nunavut X0A 0L0, Canada
5Natural History Museum, University of Oslo, PO Box 1172, Blindern, 0318 Oslo, Norway
6Environment and Climate Change Canada, CW-422 Biological Sciences Building, University of Alberta, Edmonton, AB T6G 2E9, Canada
*Corresponding author:

ABSTRACT: Loss of Arctic sea ice has implications for the distribution and population structure of ice-dependent species such as polar bears Ursus maritimus. We used remotely sensed sea-ice concentration data for Baffin Bay, Canada, and satellite telemetry for adult female polar bears in the 1990s (n = 43) and 2000s (n = 38) to assess whether sea-ice habitat changes have influenced movements and habitat selection. Both the timing and availability of sea-ice habitat changed significantly between the 1990s and 2000s. Mean sea-ice concentration in June-October declined from 22 to 12%. Spring sea-ice retreat occurred 2 wk earlier and fall sea-ice advance 2 wk later in the 2000s. These changes translated directly to changes in habitat use by polar bears. In the 2000s, bears used significantly lower sea-ice concentrations in winter and spring. Also, bears were significantly closer to land in all months, except at the end of spring breakup when they remained on offshore sea ice as long as possible, likely to maximize foraging time prior to coming on land where they are largely food deprived. The presence of summer offshore sea ice facilitated broad movement of bears in the 1990s; however, this ice disappeared in the 2000s and resulted in significant declines in monthly movement rates. In the 2000s, adult females selected for lower sea-ice concentrations if they facilitated access to the continental shelf (<300 m). Our findings indicate that significant changes in available sea-ice habitat and habitat use in Baffin Bay have occurred since the mid-1990s and this subpopulation will likely experience negative population-level impacts related to a changing climate in the coming decades. In some other parts of the Arctic, such changes have preceded negative nutritional and demographic impacts.

KEY WORDS: Arctic · Canada · Greenland · Habitat models · Polar bear · Ursus maritimus · Sea ice

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Cite this article as: Laidre KL, Stern H, Born EW, Heagerty P and others (2018) Changes in winter and spring resource selection by polar bears Ursus maritimus in Baffin Bay over two decades of sea-ice loss. Endang Species Res 36:1-14.

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