Polar bears, the Arctic’s apex predators, are highly specialized carnivores uniquely adapted to their icy environment. As the largest land carnivores, their survival relies heavily on the marine ecosystem. Their diet focuses on obtaining high-calorie sustenance to thrive in a harsh, cold climate.
Primary Prey
Polar bears primarily hunt seals. Ringed and bearded seals are common prey, but they also target harp and hooded seals. The high-fat content of seal blubber is essential for polar bears, providing energy needed to survive the Arctic’s frigid temperatures and periods of food scarcity. A single 55 kg ringed seal can provide enough energy for a polar bear for approximately eight days.
Hunting techniques are adapted to the sea ice environment. One common method is “still-hunting,” where a bear waits patiently for hours near a seal’s breathing hole. When a seal surfaces for air, the bear quickly seizes it. Polar bears also stalk seals resting on the ice, crawling slowly and freezing when the seal raises its head, before a final charge from about 6 meters away. During spring, they may locate and dig into snow lairs where seal pups are born, preying on the vulnerable young.
Opportunistic Feeding
When seals are scarce, polar bears feed opportunistically. They may prey on walrus calves or scavenge carcasses of larger marine mammals like beluga whales, narwhals, and bowhead whales. Polar bears have been observed killing beluga whales, particularly when they become trapped in ice openings. They also consume birds, bird eggs, fish, and small mammals like rodents and hares.
Carrion, including the remains of whales or other polar bears, can also be a food source, detected by their keen sense of smell. Polar bears may prey on larger land mammals like caribou or muskox, though these are not typical primary food sources due to the energy expenditure required to hunt them. Despite these varied options, these alternative foods offer less caloric value compared to seals and do not provide sufficient energy to sustain a polar bear population long-term.
Factors Influencing Diet
A polar bear’s diet is influenced by the availability and stability of sea ice. Sea ice serves as a platform for hunting seals, their main prey. The annual cycle of sea ice melting in summer and reforming in winter directly impacts hunting success and prey access. During summer when sea ice retreats, polar bears may be forced onto land, leading to periods of fasting or reliance on less calorie-dense opportunistic foods.
The extent of sea ice and its stability dictates how far bears must travel and how effectively they can hunt. Diminishing sea ice, linked to a warming Arctic, reduces the time polar bears have to hunt seals, particularly in spring when they build up fat reserves. Geographic location also plays a role, with regional variations in diet based on local prey populations and ice conditions. This dependence on sea ice underscores the connection between their habitat and their ability to secure nourishment.