What Do Polar Bears Eat? Seals, Sea Ice and Summer Fasting

The main prey: ringed and bearded seals

The polar bear depends on a few species of ice-living seals. The most important is the ringed seal, the smallest and most common seal of the Arctic, usually around 1.5 m (5 ft) long. Ringed seals live under the sea ice all year, keeping breathing holes open with the claws on their front flippers, so polar bears can find them almost anywhere on the ice.

The second main prey is the bearded seal, a much larger animal that can weigh over 300 kg (660 lb). Bearded seals are harder to hold on to, so they are taken mainly by big adult males. In the Atlantic Arctic, bears also catch harp and hooded seals, and in the Bering and Chukchi seas they take spotted and ribbon seals. Young walruses, belugas and narwhals stranded in small openings in the ice are occasional prey.

How polar bears hunt seals

Polar bears do not chase seals through the water, because seals are far faster swimmers. Instead they use patience and surprise.

• Still-hunting: the most common method. A bear finds a breathing hole by smell and waits beside it without moving, sometimes for hours. When a seal comes up for air, the bear grabs it with its claws and teeth and hauls it onto the ice.
• Stalking: when a seal is resting on the ice, the bear creeps forward, lowering its head and freezing whenever the seal looks up. It may approach through water channels before lunging out at the last moment.
• Breaking into lairs: in March to May, ringed seals give birth in snow caves on top of the ice. A bear smells the hidden pup, rears up and crashes through the snow roof with its front paws.

Most attempts fail, and a bear may go several days between kills. That is why access to good sea ice in spring and early summer, when seal pups are plentiful, is so important for the whole year.

Why polar bears eat mostly blubber

When a polar bear catches a seal, it often eats the skin and blubber first and may leave most of the meat. Fat contains about twice as much energy as protein, and digesting fat produces water, which helps a bear living on frozen ground. Studies of polar bear energy needs suggest an adult needs on average around 2 kg (4.4 lb) of seal fat a day, but in practice bears feast and then go without.

The leftovers feed many other animals. Arctic foxes follow polar bears for this reason, and ravens, gulls and young polar bears also pick at the remains. The fox’s side of the story is in what do Arctic foxes eat?

Scavenging whales and other foods

Polar bears are skilled scavengers. A dead whale washed up on a beach or frozen into the ice can feed many bears for weeks, and in parts of northern Alaska bears gather each autumn at the remains of bowhead whales from the regulated Indigenous subsistence harvest.

In summer some bears also eat seabirds and their eggs, raid nesting colonies of eiders and gulls, and occasionally catch reindeer or fish. They have been seen eating berries, grass, kelp and seaweed. These foods matter for some bears, but research in Hudson Bay suggests that land foods cannot supply nearly enough energy to replace seals.

Summer fasting on land

Where the sea ice melts completely in summer, as in Hudson Bay, polar bears must come ashore and wait for the ice to return in late autumn. For around four months they eat very little and live mainly off the fat they built up in spring. They save energy by resting, lying in shallow pits and moving slowly.

Pregnant females fast even longer. A mother may stay ashore through the summer, then dig a den, give birth and nurse her cubs through the winter, going up to about eight months without a proper meal. This only works if she has stored enough fat beforehand, which is why early ice break-up is so harmful.

Climate change and the polar bear’s food

The polar bear’s diet ties it tightly to the sea ice. When the ice breaks up earlier in spring, bears lose weeks of their best hunting season and come ashore thinner. Long-term studies in Western Hudson Bay and the Southern Beaufort Sea have linked shorter ice seasons to lower body condition and fewer surviving cubs. Read more in how many polar bears are left?

Do polar bears eat penguins?

No. This is a common mix-up, but polar bears and penguins live at opposite ends of the planet. Polar bears are found only in the Arctic and wild penguins only in the Southern Hemisphere, so a polar bear has never eaten a wild penguin. See do polar bears live in Antarctica?