In southern portions of their range, like Hudson Bay, Canada, there is no sea ice during the summer, and the polar bears must live on land until the Bay freezes in the fall, whereupon they can again hunt on the ice. While on land during the summer, these bears eat little or nothing.
In just 20 years the ice-free period in Hudson Bay has increased by an average of 20 days, cutting short polar bears' seal hunting season by nearly three weeks. The ice is freezing later in the fall, but it is the earlier spring ice melt that is especially difficult for the bears. They have anarrower timeframe in which to hunt during the critical season when seal pups are born. As a result, average bear weight has dropped by 15 percent, causing reproduction rates to decline. The Hudson Bay population is down more than 20 percent.