The Diet of the Arctic's Apex Predator
Polar bears (Ursus maritimus) are the world's largest land carnivores, and their diet is almost exclusively meat-based. Unlike their brown bear cousins, polar bears have evolved over thousands of years to rely almost entirely on marine prey. Understanding what they eat — and how — reveals just how perfectly adapted they are to life in one of Earth's harshest environments.
Primary Prey: Ringed Seals
The ringed seal (Pusa hispida) is the cornerstone of a polar bear's diet. These seals are small, abundant, and critically important to polar bear survival. They are rich in fat and calories — exactly what a polar bear needs to build and maintain its thick layer of blubber.
- Fat content: Ringed seals carry a thick blubber layer that provides enormous caloric value per kill.
- Availability: They are the most numerous seal species in the Arctic, making them the most accessible prey.
- Year-round target: Polar bears hunt ringed seals throughout the year, though with varying success depending on sea ice conditions.
Secondary Prey Species
While ringed seals dominate their diet, polar bears are opportunistic feeders and will consume a variety of other prey when the chance arises:
- Bearded seals – Larger than ringed seals and a prized, high-calorie meal.
- Harp seals and hooded seals – Hunted seasonally as they migrate through polar bear territory.
- Beluga whales – Occasionally hunted when trapped in small openings in the ice (a phenomenon called sassats).
- Walruses – Rarely attacked due to their size and aggression, but polar bears may scavenge walrus carcasses.
- Narwhals – Similar to beluga whales, targeted when they become stranded under ice.
What Polar Bears Eat When Prey Is Scarce
During summer months when sea ice retreats and seal hunting becomes difficult, polar bears may resort to supplemental food sources to avoid starvation. These include:
- Bird eggs (particularly from eider ducks nesting on tundra)
- Small mammals like arctic foxes or rodents
- Kelp and other vegetation — though this provides very little nutritional value
- Berries and grasses in coastal areas
- Carrion (the carcasses of beached whales or other large marine mammals)
It's important to note that plant material and small land animals do not provide enough calories or fat to sustain a polar bear. These are survival stopgaps, not dietary replacements.
How Much Do Polar Bears Eat?
Polar bears consume enormous amounts when food is available. During peak feeding season, a bear can eat over 45 kg (100 lbs) of fat and meat in a single sitting. They primarily eat the fat and skin of seals, often leaving behind the muscle and organs — though a very hungry bear will consume the entire carcass.
Seasonal Feeding Patterns
| Season | Feeding Activity | Primary Food |
|---|---|---|
| Spring | Peak feeding | Ringed seal pups (high fat content) |
| Summer | Reduced / fasting | Opportunistic scavenging, vegetation |
| Autumn | Moderate | Seals as ice begins to reform |
| Winter | Active hunting | Ringed and bearded seals |
Why Fat Is So Important
In the Arctic, calories — especially from fat — mean survival. Fat insulates polar bears from freezing temperatures, fuels long swims between ice floes, and sustains pregnant females through months of denning without food. A polar bear that cannot build sufficient fat reserves before summer may not survive the lean months ahead.
This fat dependency is also why the loss of sea ice is so devastating — without stable hunting platforms, polar bears cannot catch enough seals to maintain their body condition.