Polar bears, iconic predators of the Arctic, are remarkably adapted to their icy environment and are exceptional swimmers. Their scientific name, Ursus maritimus, which translates to “sea bear,” reflects their strong connection to the ocean.
Masters of the Water
Polar bears possess a suite of physical adaptations that make them highly proficient in water. Their large front paws, up to 12 inches wide and slightly webbed, act like powerful paddles, propelling them in a doggy-paddle style. Their hind legs and feet are held flat, serving as rudders for steering and stability. The bear’s streamlined body shape further reduces water resistance, allowing for efficient movement.
Beneath their thick fur, polar bears have a substantial layer of blubber, up to 11 centimeters (4.3 inches) thick. This blubber provides crucial insulation against frigid Arctic waters and contributes significantly to their buoyancy. Their dense, water-repellent fur, composed of hollow hairs, also traps air, adding to insulation and buoyancy while preventing water absorption. These adaptations enable polar bears to swim up to 10 kilometers per hour (6.2 mph) and sustain swims for hours or even days. They can hold their breath for up to three minutes and dive to depths of up to 4.5 meters (14.8 feet) while submerged.
Why Polar Bears Take to the Water
Swimming is an integral part of polar bear survival in the Arctic. They use water to travel between ice floes or landmasses, navigating the dynamic sea ice environment. This ability allows them to access different areas for hunting and to follow the seasonal movements of ice.
While polar bears are adept swimmers, open water hunting is less successful than hunting from ice platforms, as seals are faster in the water. However, they utilize their aquatic skills to stalk prey by swimming quietly towards seals resting on ice or waiting at breathing holes. Swimming also serves as a way for polar bears to cool down, as their substantial insulation can lead to overheating, especially during physical activity or in warmer conditions.
Swimming in a Changing World
Despite their exceptional swimming abilities, environmental changes pose new challenges for polar bears. The ongoing loss of sea ice, driven by a warming climate, forces these animals to undertake increasingly longer and more frequent swims. As their ice habitat diminishes, polar bears must traverse larger expanses of open water to find stable ice for hunting seals or to reach land.
These extended swims demand significant energy, costing polar bears five times more energy than walking the same distance. Such increased energy expenditure can lead to a decline in body condition and a reduction in reproductive success. Female polar bears have been documented swimming hundreds of kilometers for multiple days, with one instance of a bear swimming 426 miles (686 km) over nine days, losing 22 percent of her body weight. These journeys also carry heightened risks for cubs, which are more vulnerable to hypothermia and exhaustion, leading to higher cub mortality rates.