Ringed Seals Accept Polar Bear Risk for Diet Variety, UBC Study Shows

Ringed seals in eastern Hudson Bay will enter high polar bear activity zones and dive for longer durations when fish diversity is especially varied, even at elevated predation risk, according to new research published in Ecology Letters by scientists from the University of British Columbia and collaborating institutions. The findings suggest that climate change is reshaping both prey distribution and predator-prey dynamics in Arctic ecosystems simultaneously.

Researchers tracked 26 ringed seals and 39 polar bears using GPS and dive data in eastern Hudson Bay, combining the information with daily sea-ice maps and yearly models of fish species diversity. The study found that seals avoided areas with very high bear activity by moving through them quickly but dived longer in bear hotspots when fish variety was high — a behaviour the team attributes to a portfolio effect, whereby animals diversify food sources to reduce exposure to unpredictable ocean conditions. In safer locations, greater fish variety led to shorter dives, consistent with easier foraging.

The research underscores how climate change is simultaneously altering sea ice extent, zooplankton availability, fish distributions and predator presence in the Arctic. As sea ice shrinks, relative polar bear density on remaining ice could spike in the short term, temporarily raising predation risk for seals even as long-term bear numbers decline. The study notes that seals may lack effective detection tactics against killer whales, which are gaining access to Arctic waters as ice retreats, posing a different class of predation threat compared to polar bears.

The researchers argue that habitat protection models must incorporate both food availability and predation risk to accurately reflect where animals actually live. Building maps of critical habitat while ignoring predator-prey interactions risks protecting areas that animals are actively avoiding in a climate-changed future, lead author Katie Florko said. Senior author Marie Auger-Methe of UBC noted that more accurate population maps also support food security and wildlife management for communities across the North that depend on healthy seal and fish populations.

Key figure — 26 ringed seals and 39 polar bears tracked across eastern Hudson Bay