When sea ice retreats, polar bears fast while relying on fat reserves until the ice re-forms in winter, allowing them to resume hunting seals from the ice.

Hudson Bay (Canada) polar bears face increasingly prolonged ice-free periods, with recent decades showing a 24 to 34-day increase in ice-free days compared to the 1980s. This extended fasting period challenges their survival, particularly for sub-adults and adult females. Adult males, while initially stable due to their diverse diet and ability to steal kills, are also seeing reduced weights and survival rates. If the ice-free period extends, rapid declines in adult male survival are anticipated. Earlier ice retreat is also correlated with decreased survival of younger and females bears, as it increases food-related stress and decreases reproductive success.

Global warming, which has already exceeded 1°C above pre-industrial levels, threatens to further extend the ice-free period, potentially reaching critical thresholds that could result in significant polar bear mortality. Additionally, earlier sea ice breakup could severely impact cub recruitment, leading to long-term population declines. The loss of snow cover, essential for ringed seal habitat and polar bear denning, will also negatively impact polar bear populations.

Proactive measures, such as reducing fossil fuel, are crucial to mitigate these effects and support the survival of Hudson Bay's polar bears and the livelihoods of the indigenous communities relying on this ecosystem.