Polar bears are the Arctic’s largest land predators, uniquely adapted to survive in one of Earth’s harshest environments. Their immense size, thick fur, and insulating layer of blubber are supported by a highly specialized diet. This diet is fundamental to their existence, providing the substantial energy required to maintain body temperature and thrive in icy landscapes. As apex predators, their feeding habits play a significant role in the Arctic food web.
Primary Dietary Staples
Polar bears primarily rely on a fat-rich diet, with seals forming the vast majority of their caloric intake. Ringed seals (Pusa hispida) are the most common and important prey species across much of the polar bear’s range. These seals offer a high-fat, high-energy food source, essential for building and maintaining their insulating blubber layer, crucial for survival in frigid temperatures.
Bearded seals (Erignathus barbatus) also constitute a significant part of the polar bear’s diet, particularly in areas where they are abundant. While larger and more challenging to subdue than ringed seals, their substantial blubber reserves make them a highly valuable catch. The high fat content of these marine mammals provides the concentrated energy polar bears need to sustain their large body mass and fuel their extensive hunting expeditions.
Other seal species, such as harp seals (Pagophilus groenlandicus) and hooded seals (Cystophora cristata), can be part of their diet, especially during specific times of the year or in certain geographical regions. However, these are generally less common than ringed and bearded seals.
Hunting Methods
Polar bears employ various hunting strategies, primarily adapted for capturing seals on or near sea ice. One common technique is “still-hunting,” where a bear patiently waits by a seal’s breathing hole in the ice. With an acute sense of smell, they can detect seals beneath the snow and ice, sometimes from a distance of up to 20 miles.
When a seal surfaces to breathe, the bear rapidly pounces, using its strength to pull the seal onto the ice. Another method involves stalking seals resting on the ice, often near the edge of floes. The bear uses available cover, like snowdrifts or ice ridges, to approach undetected before launching a swift attack.
Polar bears also target seal pupping lairs, which are snow dens where mother seals give birth and nurse their young. Using their powerful forepaws, they can break through the snow and ice roof of these lairs to access the pups and mothers inside. This method is particularly effective during the spring pupping season.
Opportunistic Feeding and Adaptations
While seals are their primary food source, polar bears are also opportunistic feeders. They may consume carrion, such as the carcasses of whales or other marine mammals that wash ashore or are found on the ice. These large finds provide a temporary, significant food source, though they are unpredictable.
During the summer months when sea ice recedes and seals become less accessible, polar bears might turn to terrestrial food sources. This can include birds and their eggs, particularly during nesting seasons, or even small mammals. They have also been observed consuming vegetation like berries, kelp, and mosses, but these offer minimal nutritional value for a carnivore with high energy demands.
Other large prey, such as walruses (Odobenus rosmarus) or beluga whales (Delphinapterus leucas), are rarely hunted by polar bears due to the significant risk involved. While a polar bear might attack a walrus, it is a dangerous endeavor and typically only attempted against young, sick, or injured individuals. The physiology of a polar bear is adapted for a high-fat, carnivorous diet, meaning that non-seal food sources generally do not provide sufficient calories for long-term survival.