Polar bears are iconic Arctic predators. While known for traversing frozen landscapes, their remarkable swimming capabilities are a defining characteristic. They navigate frigid waters with surprising agility and endurance.
Polar Bear Swimming Endurance
Polar bears can sustain long swims, covering considerable distances. A documented event involved an adult female polar bear swimming continuously for 232 hours (nearly 9.7 days), covering approximately 687 kilometers (426 miles) in the Beaufort Sea.
Studies document polar bears swimming up to 160 kilometers (100 miles) without resting, with one study observing 50 swims averaging 96 miles. Their swimming speed can reach 10 kilometers per hour (6.2 mph), though they typically maintain 3 to 4 kilometers per hour, similar to a person walking. These prolonged swims come at a high energy cost; the record-breaking female lost 22 percent of her body mass during her nine-day journey.
Polar Bear Adaptations for Water
Polar bears are physically adapted for water. A thick layer of blubber, up to 11 centimeters (4.3 inches) deep, provides insulation against cold water and aids buoyancy, helping them retain body heat in frigid Arctic seas.
Their dense fur coat is another adaptation, featuring water-repellent guard hairs that do not mat when wet, minimizing heat loss. These hollow hairs also trap air, enhancing buoyancy. Polar bears use their large, slightly webbed front paws as paddles for propulsion, while their hind legs act as rudders. Their streamlined body shape reduces drag, improving efficiency. They can also close their nostrils and ears when submerged, remaining underwater for over three minutes.
Reasons for Polar Bear Swims
Polar bears undertake long swims for various reasons, some natural and others driven by environmental shifts. Historically, these swims allowed them to move between scattered ice floes to hunt seals, their primary prey, or to reach distant landmasses and new feeding grounds. Their life cycle is linked to the sea ice, which serves as a platform for hunting, mating, and raising young.
However, the rapid melting of Arctic sea ice, largely due to climate change, forces polar bears to swim longer distances to find ice platforms or reach shore. As sea ice retreats earlier in spring and forms later in winter, bears have less time to hunt, leading to higher energy expenditure during these prolonged swims. These journeys carry risks, particularly for cubs, with one study showing a 45 percent mortality rate for cubs accompanying mothers on long-distance swims.