Polar bears are Arctic predators adapted to extreme cold. Their survival depends on sea ice, a platform for their activities. These animals navigate frozen landscapes and frigid waters.
Remarkable Swimming Prowess
Polar bears are exceptional swimmers, with aquatic abilities essential for their survival. They propel themselves through the water primarily using their large front paws in a powerful dog-paddle style. Their hind legs remain extended and flat, functioning as rudders to steer and stabilize their movement. This efficient technique allows them to achieve swimming speeds of up to 10 kilometers per hour (6.2 mph). Polar bears can also hold their breath underwater, typically for 30 to 60 seconds when hunting, though they have been observed to remain submerged for over three minutes during dives.
Physical Traits for Water Life
Several adaptations enable polar bears to thrive in water. A thick layer of blubber, up to 11 centimeters (4.3 inches) thick, provides insulation in cold waters and aids buoyancy. Their dense fur consists of an outer layer of hollow guard hairs that are water-repellent, preventing water from soaking through to their skin and helping them dry quickly after a swim. Additionally, their large paws, up to 30 centimeters (12 inches) wide, are partially webbed, enhancing their propulsion in water. When submerged, polar bears can instinctively close their nostrils and flatten their ears to prevent water entry. Their streamlined body shape, with a large rump and smaller shoulders, also contributes to their efficiency in the water.
Why Polar Bears Take to the Water
Polar bears enter the water for hunting and travel. Their main prey, seals, are often found in water or on ice floes, requiring them to swim. While they are not faster than seals in open water, they use swimming to approach seals resting on ice or to wait at breathing holes. Swimming is also a common means of travel, allowing them to move between fragmented ice floes, cross open water leads, or reach distant landmasses. In warmer conditions or after strenuous activity, polar bears may swim to regulate their body temperature and cool down, as their thick insulation can lead to overheating.
Endurance and Aquatic Hazards
Polar bears are capable of long-distance swims, demonstrating their endurance in the Arctic. Studies have documented swims ranging from 51 km to over 687 km (426 miles), with some lasting for more than nine days.
These long journeys carry risks. Long-distance swimming is energetically demanding, consuming about five times more energy than walking. Such prolonged efforts can lead to exhaustion, substantial weight loss, and hypothermia, especially in colder waters. Cubs are particularly vulnerable during these long swims, as their smaller body size and limited fat reserves make them more susceptible to hypothermia and drowning. The increasing frequency of long-distance swims, often necessitated by diminishing sea ice due to climate change, poses a growing threat to polar bear populations.