2 Answers

1.  Polar bears feed mainly on ringed and bearded seals. Depending upon their location, they also eat harp and hooded seals and scavenge on carcasses of beluga whales, walruses, narwhals, and bowhead whales.

2.  On occasion, Polar Bears kill Beluga Whales and young Walruses.

3.  When other food is unavailable, polar bears will eat just about any animal they can get, including reindeer, small rodents, seabirds, waterfowl, fish, eggs, vegetation (including kelp), berries, and human garbage.

More info here>>>http://www.seaworld.org/animal-info/info-books/polar-bear/diet.htm

As both predator carnivores and scavengers, they will eat about anything they can kill, or find dead.  They like other bears are also omnivores, so they will eat plant matter also, not much growing where they live, but they will scavenge and eat at dumps when the opportunity poses itself for an easy meal.