Space‐use strategies drive diet composition of Baffin Bay polar bears

• Published in: Ecosphere
• Main Authors: Stern, Jennifer H., Laidre, Kristin L., Born, Erik W., Wiig, Øystein, McKinney, Melissa A.
• Other Authors: Environment and Climate Change Canada, Government of Nunavut, National Aeronautics and Space Administration, Nunavut Wildlife Management Board, Pinngortitaleriffik
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2024
• Subjects: Baffin Bay; Greenland; Baffin; bearded seal; Beluga; Beluga*; Cystophora cristata; Delphinapterus leucas; Erignathus barbatus; glacier; hooded seal; Monodon monoceros; narwhal*; Pagophilus groenlandicus; Pusa hispida; Sea ice; Ursus maritimus
• Online Access: http://dx.doi.org/10.1002/ecs2.4826; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1002/ecs2.4826

Abstract Polar bears ( Ursus maritimus ) depend on sea ice to hunt their ice‐associated prey. However, climate‐induced sea ice loss is leading to changes in space‐use strategies of polar bears, with bears in some subpopulations spending more time on land or selecting alternative habitats. One such documented alternative habitat is glacier ice, which provides year‐round access to prey, although the feeding habits of polar bears using glacier ice relative to those following the retreating ice and/or seasonally moving onshore are not known. Here, we use adipose tissue from polar bears ( n = 104) from the Baffin Bay subpopulation live‐captured in Northwest Greenland during the springs of 2009–2013 to investigate dietary patterns between space‐use strategies inferred from satellite telemetry data, while considering demographic and interannual variation. Using quantitative fatty acid signature analysis (QFASA) to generate diet estimates, ringed seals ( Pusa hispida ) and bearded seals ( Erignathus barbatus ) were estimated as the primary and secondary prey of Baffin Bay polar bears for all sex/age classes and sampling years, apart from a single anomalous year (2009) with a relatively high proportion of beluga ( Delphinapterus leucas ) and narwhal ( Monodon monoceros ). While demographic and short‐term temporal variation was minimal, fatty acid signatures and QFASA‐generated diet estimates clearly differed between polar bears using coastal and offshore space‐use strategies. “Offshore” adult females ( n = 31), which make long‐distance movements across the Baffin Bay pack ice, had high proportions of C22‐chain length monosaturated fatty acids and diet estimates that included beluga, narwhal, harp ( Pagophilus groenlandicus ), and hooded seal ( Cystophora cristata ). “Coastal” adult females ( n = 6), which remain resident at glacier fronts in Northwest Greenland year‐round including during the sea ice‐free season, consumed proportionally more ringed seals (+13%) and similar proportions of bearded seal, but essentially no ...