Yes. Polar bears are strong swimmers. They paddle with their big front paws at up to about 6 mph (10 km/h), and some have swum for days at a time. The longest swim on record is 687 km (426 miles) over nine days, made by a female in the Beaufort Sea in 2008. She lost about a fifth of her body mass, and her yearling cub did not survive.
How polar bears swim
A polar bear swims much like a large dog. The forepaws act as paddles and the hind legs trail behind and steer like rudders. The front paws can be up to 30 cm (about 12 inches) across, and the National Park Service describes them as large and webbed.
Several features help in cold water:
- Water-shedding fur. Long guard hairs over a dense undercoat repel water. Each hair is hollow and air-filled, and the skin underneath is black.
- A fat layer. Polar bears carry roughly 2 to 4 inches (5 to 10 cm) of fat under the skin, which insulates them and adds buoyancy.
- Short dives. Polar bears also dive, mostly to sneak up on seals resting on the ice. The longest dive researchers know of lasted 3 minutes and 10 seconds, by a bear stalking a seal in Svalbard.
How far and how fast can a polar bear swim?
| Measure | Figure |
|---|---|
| Swimming speed | Up to about 6 mph (10 km/h) |
| Distance without rest | More than 60 miles (100 km) reported |
| Longest recorded swim | 687 km (426 miles) in 9 days |
| Average speed on that swim | About 76 km (47 miles) per day, roughly 2 mph |
| Energy cost | Three to four times the cost of walking |
The 6 mph figure is a cruising pace for stretches of swimming. Over the record nine days, the female averaged only about 2 mph, so it is not what a bear holds for days on end.
A study of GPS-collared females in the Beaufort Sea found long swims ranged from about 54 km to 687 km, and from less than a day to nearly 10 days. The authors concluded that long swimming is a response to shrinking summer sea ice. Another female in the same research swam for more than 12 days but appears to have found places to rest along the way.
What long swims cost
The record swim was not a triumph for the bear. Researchers had collared the female in late August 2008 and recaptured her in late October. In between, she swam 687 km in nine days and then kept traveling over the ice. She lost 22 percent of her body mass. Her yearling cub died at some point between the start of the swim and the next time researchers saw the mother on land.
Swimming is expensive. Polar Bears International reports that it costs three to four times as much energy as walking. A different adult female swam 462 km over 10 days and used almost five times the energy of a bear resting, walking and hunting on sea ice.
Why polar bears swim
- Hunting. They slip into the water to cross gaps between floes and to stalk seals resting on the ice.
- Getting from ice to ice. When ice breaks up, bears swim to the next floe or back to land.
- Reaching land or remaining ice. In summer, when the ice retreats, some bears swim to shore or to ice that lasts longer.
Researchers link more long swims in the Beaufort Sea to years of extensive open water. Every long swim burns fat that a bear would otherwise save for the lean months.
Can polar bear cubs swim?
Not from birth. Newborn cubs weigh about 1 pound, are blind, and spend their first months in a snow den. They leave the den at about three to four months, usually in March or April. Cubs stay with their mother for just over two years, and swimming is one of the things they learn from her.
Young cubs have less fat to insulate them in cold water. Polar Bears International notes that yearlings handle swims better than younger cubs, and that mothers with new cubs avoid big swims where they can.
Are polar bears marine mammals?
Yes, legally. The U.S. Marine Mammal Protection Act classifies polar bears as marine mammals. Seals, mainly ringed seals, are their main prey, and they hunt from the sea ice. Even so, they are bears that walk on ice and swim between patches of it, not fully aquatic animals like seals or whales.
The polar bear lineage is fairly young. Polar Bears International gives a best estimate of less than 500,000 years ago for the split from brown bears, and says scientists are still working on it. For how they compare with their closest relatives, see polar bear vs grizzly size and polar bear vs Kodiak bear.
Where polar bears stand today
About 26,000 polar bears live in 19 subpopulations across the Arctic. The IUCN lists the species as Vulnerable, and in the United States it is protected under the Endangered Species Act and the Marine Mammal Protection Act. Loss of sea ice is the main long-term threat, because bears need the ice as a platform for hunting seals.
Sources
- Polar bear (U.S. Fish and Wildlife Service)
- Longest Polar Bear Swim Recorded, 426 Miles Straight (National Geographic)
- Polar Bears Expend More Energy in a Melting Arctic (Polar Bears International)
- How long can a polar bear stay underwater? (Polar Bears International)
- Polar bear (San Diego Zoo Wildlife Alliance)