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Variation in energetic balance among free-ranging polar bears during the spring mating and foraging season

January 21, 2025

Large carnivores are capable of consuming substantial biomasses that can significantly alter their body mass and condition over short periods. Here we examine the intra-seasonal variation of polar bear (Ursus maritimus Phipps, 1774) body mass, energy intake, and condition in the spring from two subpopulations. We evaluate the biological and temporal factors that may have driven changes in body mass of 31 individuals captured and recaptured over 2–39 days and assess whether these changes influenced their estimated condition. Body mass changed by –61 to 33 kg ( = –2 kg) with bears exhibiting increases in mass with increasing age and decreases with greater initial mass. On average, estimated intake was 57 MJ/day. Estimated daily mass-specific body mass changes exhibited greater variation relative to previous measures in polar bears or brown bears (U. arctos Linnaeus, 1758). Yet, across all bears, measures of condition remained similar between captures. The marked variation in mass gains or losses highlights the varying behavioral and physiological limitations that influence foraging success within this apex carnivore during a season when two key life history events converge wherein feeding is often reduced during mating activities despite the importance of the spring hyperphagia period to long-term energy balance.

Publication Year 2025
Title Variation in energetic balance among free-ranging polar bears during the spring mating and foraging season
DOI 10.1139/as-2024-0051
Authors Anthony M. Pagano, Stephen N. Atkinson, Louise C. Archer
Publication Type Article
Publication Subtype Journal Article
Series Title Arctic Science
Index ID 70262797
Record Source USGS Publications Warehouse
USGS Organization Alaska Science Center Ecosystems
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