Polar bears are apex predators of the Arctic, uniquely adapted to survive in one of Earth’s most extreme environments. Their specialized biology allows them to thrive in frigid conditions. This article explores their distinct dietary habits and extraordinary eating capacity, behaviors central to their survival.
Their Primary Diet
Polar bears primarily rely on seals, particularly ringed and bearded seals, hunted from sea ice. Seal blubber provides the high fat and energy they require. While seals are their main diet, polar bears are also opportunistic feeders. They may consume other prey such as young walruses, beluga whales, or scavenge whale carcasses. During scarcity, they might also eat birds, eggs, or terrestrial animals, though these offer far less nutritional value than seals.
Feasting Capacity
Polar bears can consume vast amounts of food in a single feeding session. When prey is abundant, particularly during peak hunting seasons, they engage in feasting to rapidly accumulate energy reserves. A polar bear can eat up to 45 kilograms (100 pounds) of seal blubber in one sitting. Some reports indicate they can consume 10 kilograms of blubber in less than 30 minutes. An adult bear can consume as much as 20% of its body weight in a single meal. They prioritize eating the energy-dense blubber first, often leaving the remaining meat for scavengers like Arctic foxes or other bears.
Energy Demands and Metabolism
The immense eating capacity of polar bears is directly linked to their substantial energy demands for survival in their cold habitat. They possess a high metabolic rate, which helps them maintain a stable body temperature in the Arctic. Fat, primarily from seal blubber, serves as their main energy source, enabling them to build thick layers for insulation and long-term energy storage. Their bodies are efficient at processing and storing this fat. Studies indicate their metabolic rates are 1.6 times greater than predicted, requiring many seals for energy, a need further elevated by their large size and active hunting.
Periods of Fasting
Despite their capacity for feasting, polar bears frequently experience prolonged periods of food scarcity. These lean times are common during summer months when sea ice melts, making seal hunting difficult. During these periods, polar bears rely on extensive fat reserves accumulated during feasting, enduring months without food. Some populations, like Western Hudson Bay, fast up to four months on land awaiting sea ice, while pregnant females can fast up to eight months while denning and nursing cubs. Longer ice-free periods strain fat reserves and elevate energy expenditure, as terrestrial food sources do not provide enough calories to sustain them.