The School: Polar Bear Adaptations for Swimming
A weekly dose of education in the ocean.
Polar bears are considered marine mammals. Although they have four legs, and are related more closely to land mammals than they are to other marine mammals, the Arctic Ocean is their livelihood. Polar bears are specialized to hunt seals, so they must venture out onto the sea ice to survive. Most of a polar bear’s time is spent, if not always in the water, then on or around it. Some almost never set foot on land.
Polar bears are capable of spending long periods of time in the water, up to many days, and can swim over 100 miles (160 km). Although it’s not clear how often they undertake these journeys by choice, it demonstrates that they have impressive swimming abilities. They can swim at a speed of up to 6 miles per hour (nearly 10 km per hour). Polar bears are well suited to this marine lifestyle thanks to their hollow, water-repellant fur, buoyant fat layer, large paws, and tapered body shape.
Tapered Body Shape. Polar bears have an unusual silhouette for a bear. They have a large rump and smaller shoulders that lead up to a long, slender neck and skull. This helps make them more streamlined in the water, and helps them keep their head above the surface.
Large paws. Polar bear paws are enormous! They can be up to 12 inches (30 cm) wide. Not only is this helpful for walking on snow and ice, but when a polar bear is swimming, they act like large paddles, helping it get more power out of every stroke taken.
Water Repellant Fur. Two layers of fur are not only for protection from the cold air. Polar bear fur is a great insulator in water as well. According to Dr. Andrew Derocher, in his recently published book, Polar Bears, A Complete Guide to Their Biology and Behavior, polar bear cubs aren’t born with this water-resistant fur, since cubs’ fur has less insulative value, but they develop it as they get older. Since the fur doesn’t absorb water or mat when wet, a polar bear can just shake itself off to dry, minimizing heat loss.
Hollow hairs. Polar bear fur has another characteristic that is helpful for swimming. Each hair is hollow, and acts like a tiny float. This hollow coat makes the bear more buoyant.
Thick Layer of Fat. Polar bear fat can be up to 4 inches (10 cm) thick. It insulates from the cold and, as it is less dense than muscle tissue, it plays an important role in the animal’s buoyancy.
Photo courtesy of MacGillivray Freeman Films