Polar bears are apex predators inhabiting the harsh Arctic environment, uniquely adapted to survive its extreme cold. These animals are considered marine mammals due to their profound reliance on the ocean and its resources. Their survival in this challenging ecosystem is closely tied to their specialized diet, which provides the necessary energy and insulation.
Primary Prey: Arctic Seals
Polar bears are hypercarnivores, with seals forming the foundation of their diet. Ringed seals are the most frequently hunted prey, owing to their abundance and manageable size for the bears. Bearded seals also represent a significant food source, with adult male polar bears more successful in catching these larger animals. Other seal species, such as harp, hooded, and harbor seals, are consumed when encountered.
The high blubber content of seals offers a dense source of energy and insulation against frigid temperatures. Polar bears prioritize consuming the energy-rich blubber and skin of their kills.
Hunting Techniques
Polar bears primarily rely on sea ice as a stable platform for hunting their prey. A common strategy is “still-hunting,” where a bear patiently waits by a seal’s breathing hole in the ice. This requires patience, as a bear may remain motionless for hours to ambush a seal when it surfaces for air.
Bears also employ stalking techniques, using their white fur as camouflage to approach seals resting on the ice. They might also ambush seals at the water’s edge or swim stealthily underwater to surprise prey. During the colder months, polar bears may locate and raid snow dens where seal pups are born, providing access to easier targets.
Seasonal and Opportunistic Feeding
When their primary seal prey becomes scarce, particularly during periods of limited sea ice, polar bears exhibit opportunistic feeding behaviors. They may scavenge on the carcasses of other marine mammals, such as whales and walruses, that wash ashore. These large carrion can provide a temporary, substantial food source.
Less calorically dense options include birds, bird eggs, small mammals like lemmings or voles, and even certain types of fish or vegetation. However, these alternative food sources do not provide the sufficient energy or fat content found in seals.
Why Fat is Essential
A diet rich in fat is essential for polar bears to thrive in their Arctic environment. The blubber from seals serves as both an energy reserve and a thick insulating layer against the extreme cold. This fat storage enables them to maintain their body temperature and sustain themselves during extended periods without food.
Polar bears can accumulate fat deposits that constitute up to half of their total body weight. Their unique metabolism allows them to efficiently process these large quantities of fat without experiencing the cardiovascular health issues common in humans with high-fat diets. Genetic adaptations, including specific changes in genes related to fat transport and metabolism, underpin this remarkable ability.