What is the primary diet of a polar bear?

The primary diet of a polar bear is seals.

Polar bears are highly carnivorous Arctic predators, and seals—especially ringed seals—provide their main food. They hunt where sea ice meets water, using the ice as a platform from which to stalk seals, wait beside breathing holes, or break into snow-covered birth lairs containing seal pups. Bearded seals are another important prey species, particularly for larger adult males.

The most valuable part of a seal is its energy-rich blubber. Polar bears need this concentrated fat to maintain body temperature, travel across sea ice, reproduce, and survive periods when seasonal ice disappears. They may eat the meat as well, but bears often focus on blubber and leave portions of a carcass for scavengers such as Arctic foxes.

Polar bears sometimes consume walruses, beluga whales, narwhals, birds, eggs, fish, berries, grass, or carrion. These foods can matter locally or seasonally, especially when bears are forced onto land, but they do not replace seals as the normal foundation of the species' diet. This dependence is why shrinking sea ice threatens access to their principal prey.