By October, polar bears have had little to eat since spring. They're hungry and the if the females don't eat soon, their babies won't thrive. If they can't find food, they may wander into the tiny seaport of Churchill, Manitoba and snack on anything that moves. But the staple of their diet is seals, and they need sea ice to hunt for them. Every year, polar bears congregate around the town, waiting for ice to form on Hudson Bay. And every year, the ice forms later and later in the year.