Polar bear in Arctic

Polar Bear

Ursus maritimus
  • CLASS: Mammalia (Mammals)
  • ORDER: Carnivora
  • FAMILY: Ursidae
  • GENUS: Ursus
  • SPECIES: maritimus







Small bumps on the pads of a polar bear’s large, wide paws may add traction and help the bear walk on slippery ice. Polar bears spend their days hunting and sleeping after a good meal. For some, these meals need to last them during the upcoming months when the Arctic ice has melted, and they are forced to spend their days on land waiting for the fall cold to once again form the very important ice. 

When not hunting, polar bears are resting, perhaps as much as 20 hours a day. Polar bears are great bed makers, building nest-like beds in seaweed piled up on the coast, digging deep caves of snow into the bluffs, or resting in a shallow snow bed and letting the blowing snow cover them, making for a snug day den.


Polar bear swimming under water.
A polar bear can swim at a speed of up to 6 miles per hour (8 knots).

Polar bears live throughout the Arctic, in areas where they can hunt seals in wide cracks in the sea ice or at breathing holes. The taxonomic name for polar bears is Ursus maritimus, which means sea bear, a fitting name for these champion swimmers. They have been known to swim more than 60 miles (about 100 kilometers) without rest in search of food, using their broad front feet for paddling and their back legs like rudders to steer. Unfortunately, due to loss of ice, the bears are now having to swim longer distances, as much as a few hundred miles, which takes a toll on their energy and fat storage.

Despite the long, harsh winter, polar bears don’t hibernate. In fact, most of them (except pregnant females) continue to hunt seals throughout the winter. When the weather is extremely cold and hunting is impossible, bears may seek temporary shelter in show dens until conditions improve.

A pregnant female stays in a snow den throughout her pregnancy, the birth of her cubs, and the first few months of the cubs’ life, without leaving the den. Changes in her metabolism allow her to go without food, water, defecation, or urination for as long as eight months. For most mammals, fasting during pregnancy would be life threatening, but the female bear gains a massive amount of weight before she dens. Her stored fat reserves provide all the energy she needs to sustain herself and her cubs. Still, she wakes easily. This process is called winter sleep.

Polar bears have no natural enemies. Strong, ferocious, intelligent, and patient hunters, they top the food chain in the Arctic, where they dine primarily on seals. The bears can remain motionless for hours above a seal's breathing hole in the ice, just waiting for a seal to pop up. The polar bear's nose is so powerful it can smell a seal on the ice 20 miles (32 kilometers) away, sniff out a seal's den that has been covered with snow, and even find a seal's air hole in the ice up to 1 mile (1.6 kilometers) away. No wonder many people call them "noses with legs!" 


Stiff fur on the sole of each foot keeps the bear from slipping on the ice. It also muffles the sound of the bear’s approach when sneaking up on a sleeping seal. It costs a polar bear twice as much energy as most other mammals to move about in its Arctic environment. This helps explain their preference for resting frequently and hunting for seals using ambush techniques rather than stalking their prey.

The ringed seal is the polar bear’s main prey, as it is the most numerous seal in the Arctic. One ringed seal provides a polar bear with enough energy for 11 days. Polar bears typically kill and eat every four to five days. These bears eat just about anything, if they have the opportunity, but it is important to remember that they need access to the high-calorie diet that seals provide. While they will eat walrus, caribou, beached whales, grass, and seaweed, none of these have been shown to provide adequate and reliable nutrition for wild polar bears.

Polar bears at the San Diego Zoo get a fortified meat-based commercial carnivore diet, dog kibble, trout and other fish, as well as root vegetables and lettuce as treats. Cow femur bones and thawed rabbits are added once or twice per week. Polar bears get very little nutrition or calories from vegetables, so these items are offered as treats, and the whole carrots keep their teeth clean.


A mother polar bear and young cub.
A polar bear cub stays with its mother until it is about two years old.

Polar bears are highly intelligent and playful. In the wild, two or more bears sometimes form “friendships” that last for weeks or even years. These bears wrestle as a form of play and may also feed and travel together. Individual polar bears have been observed sliding repeatedly downhill or across ice for no apparent reason other than just for the fun of it!

Polar bears are fairly quiet animals. Females and cubs in the den make a pulsating hum. These calls are most frequent in a cub’s first few months. Young bears also make a chuffing call to each other, which is infrequent in adult bears. 

Except for females with cubs, polar bears are solitary. Sometimes several bears scavenge together at a whale carcass or human garbage dump. Dominance is based on size, but for the most part, each animal behaves independently. Polar bears have large, overlapping home ranges and are faithful to general geographic regions, but they don’t defend territories. 

Each spring, beginning in about March, adult males begin to search for mates. Incredible as it may seem, researchers suspect that males detect the scent of a female in the footprints she makes in the snow! Once a male finds a receptive female, the two bears remain together for about two weeks. 

A fertilized polar bear egg doesn’t implant or develop right away. Instead, it implants when triggered by the female’s body condition and environmental factors, most often between September and November. This is known as delayed implantation, an adaptation that ensures cubs will be born to healthy mothers at a time of year when their chances for survival are greatest.

Breeding season for polar bears goes from about March to mid-July. A pregnant female digs a maternity den, usually into a snow bank, in October or November. The den is often no bigger than a telephone booth, but it can be about 40 degrees warmer in there. The female gives birth to one to three cubs, usually twins, in December or January.

For such a big animal, they sure start out small! Cubs weigh about 1 pound (0.45 kilograms) when born and are hairless and have their eyes closed at birth. They depend on the mother to keep them warm and fed. Milk from polar bear mothers is 36 percent fat, the richest milk of any bear species. This helps the cubs grow quickly, and by April, they weigh more than 20 pounds (9 kilograms) and start exploring with their mother outside the den. At about two years of age, they are ready to be on their own.








Today, Kalluk is our biggest bear; he weighs around 1,280 pounds (581 kilograms) and is also the tallest of the three. When he stands with all four feet on the ground, he is eye level with you if you are 5 feet (1.5 meters) tall. But when he stands up on his hind feet, he reaches over 10 feet (3 meters)! Chinook and Tatqiq are much smaller because they are females. Chinook weighs around 660 pounds (299 kilograms) and Tatqiq weighs around 580 pounds (263 kilograms). Chinook is a little rounder and shorter than Tatqiq. All three love to swim and play, and to explore the vegetation and ever-changing enrichment items keepers provide throughout the Polar Bear Plunge exhibit.




A polar bear crosses a melting iceberg.
The polar bear's habitat is in peril.








Polar bear


San Diego Zoo Polar Bear Cam.  Watch Now.



Median life expectancy is 24.2 years for females; 20.7 years for males


Gestation: With delayed implantation, pregnancy can last 6.5 to 7.1 months; actual fetal gestation is about 60 days

Number of young at birth: 1 to 3; most commonly 2

Weight at birth: 1.3 pounds (.6 kilograms)

Age of maturity: Females 5 to 6 years; males 10 to 11 years


Length: Females, 5 to 8 feet (1.5 to 2.4 meters); males, 6.6 to 10 feet (2 to 3 meters)

Height: up to 5.3 feet (1.6 meters) at the shoulder

Weight: Females, 330 to 650 pounds (150 to 294 kilograms); males, 700 to 1,200 pounds (317 to 544 kilograms)



To clean their fur, polar bears roll in the snow.



A polar bear in the snow.

Climate Change Makes Polar Bears Work Harder

Survival for polar bears is all about energy. They must capture enough calories, in the form of seals, to survive in the Arctic cold...