POLAR BEAR

POLAR BEAR

The polar bear (Ursus maritimus) is a bear native largely within the Arctic encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the world's largest landcarnivore and also the largest bear, together with the omnivorous Kodiak bear, which is approximately the same size. An adult male weighs around 350–680 kg (770–1,500 lb), while an adult female is about half that size. Although it is closely related to the Brown Bear, it has evolved to occupy a narrow ecological niche, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting the seals which make up most of its diet. Although most polar bears are born on land, they spend most of their time at sea. Their scientific name means "maritime bear", and derives from this fact. Polar bears can hunt consistently only from sea ice, which is why they spend much of the year on and near the edge of the frozen sea.

WHERE DO THEY LIVE?

The polar bear is often regarded as a marine mammal because it spends many months of the year at sea.Its preferred habitat is the annual sea ice covering the waters over the continental shelf and the Arctic inter-island archipelagos. These areas, known as the "Arctic ring of life", have high biological productivity in comparison to the deep waters of the high Arctic.The polar bear tends to frequent areas where sea ice meets water, such aspolynyas and leads (temporary stretches of open water in Arctic ice), to hunt the seals that make up most of its diet.Polar bears are therefore found primarily along the perimeter of the polar ice pack, rather than in the Polar Basin close to the North Pole where the density of seals is low.

WHAT DO THEY EAT?

FOOD INTAKE

1. A polar bear's stomach can hold an estimated 15% to 20% of its body weight. A polar bear generally eats this much only when its energy demands are high. A bear can assimilate 84% of the protein and 97% of the fat it eats. 2. Polar bears need an average of 2 kg (4.4 lb.) of fat per day to obtain enough energy to survive. A ringed seal weighing 55 kg (121 lb.) could provide up to eight days of energy for a polar bear. 3. Hibernating polar bears do not eat.

FORAGING AND EATING

1. Still hunting. • Still hunting is the most common method of hunting year-round. • The polar bear remains motionless beside a breathing hole or lead edge waiting for a seal to surface. When a seal surfaces, the polar bear bites onto the head or upper body, then flips the entire seal onto the ice. • Still hunting usually takes less than one hour, but polar bears will wait much longer. 2. Stalking on land. • Stalking is a hunting method used when seals haul out on sea ice. • Once spotted, the seal is slowly and steadily stalked by the polar bear. At 15 to 30 m (49-98 ft.) away, the polar bear suddenly charges the seal. With its claws or teeth, the polar bear grabs the seal before the seal can leave the ice. 3. Aquatic stalk. • The aquatic stalk is a method also used to hunt seals hauled out on sea ice. • The polar bear swims toward a hauled-out seal. Once the polar bear reaches the ice edge, the bear quickly emerges from the water and grabs the seal with its claws or teeth. 4. Stalking birth lairs. • Stalking ringed seals at their birth lairs is a hunting method polar bears use in spring, when ringed seals give birth to their pups. • Ringed seal birth lairs are caves built under snow drifts next to a hole in the ice. The snow drifts are on stable sea ice attached to land. • Once a polar bear identifies a birth lair, it slowly and quietly positions itself next to the lair. If a polar bear smells or hears a seal in the lair, it slowly raises up on its hind legs and crashes down with its front paws to break through the lair's roof. • To break the roof's hard surface, several tries are sometimes needed, which may allow the seal to escape into the water. • This method is most commonly used by polar bear females with cubs under one year old. ° Mother seals and pups have the high fat content needed for hungry polar bear mothers and their growing cubs. ° Male polar bears that may attack young polar bear cubs don't normally hunt seals in birth lairs. ° Birth lairs are usually on sea ice attached to land, allowing young cubs (who have little protective fat) to avoid crossing water. 5. Eating. • Once a seal is captured, a polar bear bites it several times on the head and neck to disable it before dragging it several meters from the water to feed. • A polar bear eats the skin and blubber first, then the meat. • Polar bears often stop to wash during feeding, using water nearby or rubbing in the snow. • Polar bears don't always eat the entire kill. Carcass remains are scavenged by other bears, arctic foxes, and gulls.