Polar bears are the top predator of the icy Arctic. But these large, furry white mammals have to work hard for their food. when the ocean freezes in the winter, polar bears travel hundreds of miles over floating sheets of sea ice to hunt their favorite meal--seals. During this time, they build up fat that will help them survive the rest of the year. when the ice begins to melt, polar bears head back to land, where they stay during the Arctic summer.