Body condition among Svalbard Polar bears Ursus maritimus during a period of rapid loss of sea ice

TL;DR

This study examines how polar bears in Svalbard are coping with rapid sea ice loss and finds unexpected changes in their body condition.

Contribution

The study provides the first assessment of body condition trends in the Barents Sea polar bear population amid rapid sea ice decline.

Findings

Body condition index declined until 2000 but increased afterward despite rapid sea ice loss.

Warmer climate and habitat loss did not show predicted negative effects on polar bear condition.

Increased availability of some prey species may offset reduced access to seals.

Abstract

Polar bears are only found in Arctic areas with sufficient access to sea ice and seals on which they prey. Studies have highlighted negative effects on condition and demographics in areas where sea ice cover is declining due to warmer climate, but condition of the Barents Sea polar bear population have not been examined yet. Loss of sea ice rate has been considerably higher here than in other areas with polar bears. We investigated variation in body condition index (BCI) among 770 adult bears, 1188 captures, in March-May 1995–2019, in Svalbard, Norway (western part of the Barents Sea). We assessed how intrinsic (female reproductive state, age) and both males and females, BCI declined until 2000, but increased afterwards, during a period with rapid loss of sea ice. In models including sea ice metrics and climate (Arctic Oscillation), there was no support for the predicted negative effect of warmer weather and habitat loss. This indicates a complex relationship between habitat, ecosystem structure, energy intake, and energy expenditure. Increases in some prey species, including harbour seals, reindeer, and walrus, may partly offset reduced access to seals. Our findings underline the importance not to extrapolate findings across populations.

The online version contains supplementary material available at 10.1038/s41598-025-33227-9.

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