Polar Bear

The only carnivorous land mammals on Earth are polar bears. Their length is about seven to eight feet, measured from the nose to the tip of their very short tail. Male polar bears are a lot heavier than female polar bears. A big male can weigh more than 1,700 pounds, while a big female can weigh more than half that amount (up to 1,000 pounds). After a good hunting season, bears will weigh around 50 percent more than at the beginning of the next one; much of this extra weight is accumulated fat. A newborn polar bear only weighs about 1.5 pounds. They are outstanding swimmers. Polar Bear scientific name is Ursus maritimus, which means "sea bear," according to the San Diego Zoo. As rudders, they use their broad front feet to paddle and their back legs. These bears are known to swim more than 100 km (60 miles) without resting.

Life History

In the late spring, polar bears breed when the temperatures in the Arctic start to rise. However, they don't really get pregnant at the time of breeding, like other bear species, as the tiny embryo (or blastocyst) would not implant in the uterus of the female until fall, when true gestation begins. This is called delayed implantation and enables a female bear to physiologically evaluate her condition for the next three years before beginning conception and the pregnancy, nursing, and carrying the process for her offspring. The actual gestation period following implantation is just roughly 60 days.

In the population of Hudson Bay, where the reproductive biology of polar bears has been most extensively studied, it appears that to have the blastocyst implant and begin gestation, a polar bear female carrying a blastocyst must attain a bodyweight of at least 490 pounds. The blastocyst will reabsorb if this threshold is not reached, the female will continue to hunt seals all winter, trying to be fatter a year later and ready to carry out a healthy pregnancy.

A pregnant female will dig a den in a snowbank at the beginning of the winter and begin the gestation process. Pregnant females can enter dens at any time between early October and December, depending on the location. The exit time from the dens takes place between late February and April. In a snowbank on land, most females dig their dens, but some even den on the floating sea ice. Women can dig a den in the ground in Hudson Bay instead, but they use places where the snow can build up to provide insulation. Female polar bears give birth to cubs in the middle of winter in some of the coldest areas on Earth. The size of the litter is typically two cubs, but occasionally the litter can be one, three, or, very rarely, four cubs.

In the Hudson Bay area, female polar bears spend extraordinary amounts of time fasting, the longest recorded of any species of mammal. This fasting cycle before denning takes around 180 to 186 days on average and in dens. Pregnant females will successfully fast for as long as 240 days in Hudson Bay. The long fasting period makes this species extremely vulnerable to environmental changes, such as a warming climate, which decreases the amount of time they have to build up the fat reserves they need to sustain fasting and bring about a healthy pregnancy.

What is a Polar Bear's Habitat

Polar bears live in countries bordering the Arctic Circle: Canada, Russia, Greenland, Norway, and the United States (in Alaska). Temperatures are normally around minus 29 degrees Fahrenheit (minus 34 degrees Celsius) in the Arctic during the winter and can reach as low as minus 92 F  (minus 69 C). The temperature of the water is also cold, touching, according to PBS Nature, as low as 28 F (minus 2 C), the freezing point of the seawater. Many of the physical adaptations help it retain heat in the body and cope with its icy habitat. The outer layer of the fur of the bear is hollow and absorbs light, giving a white colour to the fur that lets the bear stay camouflaged. In fact, the skin under the fur of the polar bear is black; this black is noticeable only on the nose. Polar bears often have a dense layer of fat below the surface of the skin, which serves as heat-trapping protection for the body. While swimming and during the cold Arctic winter, this is particularly necessary. The large size of the bear decreases the amount of surface area that is exposed to the cold per unit of heat-generating body mass (pounds of flesh). These are all important factors in a Polar Bear habitat. 

Where Do Polar Bears Live?

Polar bears live in ice-covered waters in the Arctic. Polar bears rely on sea ice to reach, as well as to rest and breed, the seals that are their primary source of food. The overall population of polar bears is grouped into 19 units or subpopulations. Of the sub-populations, sixty percent are in Canada. In the wild, there are 22,000–31,000 polar bears.

Polar Bear Size & Appearance

The largest species of bear are also polar bears. For bears, height, when the animal is on all fours, is generally measured at the shoulder. The polar bear height is on average 3.5 to 5 feet tall, but when standing on its hind legs, the height of the adult male polar bear may exceed 10 feet. Lengthwise, from head to rump, they are 7.25 to 8 feet (2.2 to 2.5 m). Their tail adds 3 to 5 inches of additional (7.5 to 12.5 centimeters). Polar Bear weight is about 775 to 1,200 lbs (351 to 544 kilograms). According to Polar Bear International, the largest polar bear ever weighed 2,209 pounds (1,000 kg). At just 330 to 650 lbs, females weigh half as much as their male counterparts (50 to 295 kg).

Offsprings

Females typically give birth after a gestation period of eight months during the months of November or December. The animals dig a cave from a snowbank in which to have their cubs, in preparation. A maternity den is called this tunnel. Usually, a female polar bear gives birth to twins, although they have documented singles and triplets. A cub weighs only 1.3 pounds (about half a kilogram) at birth, but they grow very fast. According to the San Diego Zoo, cubs depend upon their mothers for warmth and fattening milk, which is 36 percent fat. The cubs are out of the den by spring, exploring, and they are fully mature at two years of age. Polar bears live for 15 to 20 years or so.

Polar Bear Characteristics

• Comparatively lean, long-neck body

• Narrow head with wide eyes and ears on the outside

• Paddle-like paws with their toes webbed

• The tail is Short (7 to 13 centimeters)

• Five non-retractable, short claws

• With the exception of the lips, nose, and part of the soles of the feet. 

• With the exception of the lips, nose, and part of the soles of the feet. 

• Underwool up to 5 centimeters, hair guard/top hair up to 15 centimeters at the belly

• Heat-insulating fat layer under the skin (up to 10 centimeters)

• Hollow hairs, almost translucent and light-conducting 

• 42 teeth 

Diet

Polar bears are almost exclusively meat eaters, unlike other bear species (carnivorous). They feed primarily ringed seals, but can eat bearded seals as well. By waiting for them to come to the surface of sea ice to breathe, polar bears hunt seals. The polar bear will bite or catch the seal and drag it to land to eat as the seal reaches the surface. Walruses and whale carcasses are also eaten by them. Bird eggs and other food sources will be hunted for by polar bears, but none of these are sufficiently abundant to support the large body mass and dense polar bear populations.

Seal pups that are born and live in dens in the Arctic ice are another important source of food in most regions. In order to catch the young seals, the polar bear recognizes these dens through scent and other markers and pounces through the roof of the den. The supply of seal pups in the spring in Hudson Bay is rapidly reduced by earlier ice melting. Polar bears are at the top of the food chain in the Arctic; they consume everything and they eat none (except native hunters).

Hunting

Typically, these strong predators prey on seals. They visit areas of moving, cracking ice in search of this quarry, where seals may surface to breathe air. They even stalk ice edges and holes for ventilation. Polar bears can also eat carcasses, such as those of dead whales, if the opportunity presents itself. The rulers of their world are these Arctic giants who have no natural enemies.

Behavior 

In this Polar Bear Information, let’s discuss their behavior. Except when mating, when a female raising her cubs forms a family group, or when several bears are drawn to a food source like a beached whale, polar bears appear to live solitary lives. Young polar bears, most often with their siblings, will also play with each other while spending the summer offshore on the Hudson Bay coast. On the coast of Hudson Bay, polar bears near Churchill are also known to play with chained sled dogs without killing them, which they could easily do.

Polar Bear Facts

• In the Arctic, polar bears live.

• Polar bears have black skin and are actually translucent, while their fur appears white.

• It is the largest carnivore that lives on land (meat-eater).

• In order to hunt seals, polar bears use sea ice as a base.

• Seals make up much of the diet of polar bears.

• Male polar bears are capable of weighing up to 680 kg.

• Typically, female polar bears only weigh about half as much as males.

• Most of the time, polar bears spend their time at sea.

• It is estimated by scientists that there are about 20000 polar bears.

• They have 42 teeth.

• 'ursus maritimus' is the scientific name for the polar bear.

• Thanks to nearly 10 cm of blubber under the surface, polar bears stay warm.

• The scent of polar bears is excellent, with the ability to track seals over a mile away (1.6 km).

• On land, polar bears can reach speeds of up to 40 kph (25 mph) and in the water of up to 10 kph (6 mph).

• In Calgary, Canada, the polar bear was the mascot for the 1988 Winter Olympics.

What is the Polar Bear lifespan?

Polar bears can live up to the age of 30 in the wild, but this is rare. Before they reach 25 years old, most adults die. The conditions that are emerging in Hudson Bay are such that women will no longer be able to give birth and raise a few cubs successfully. The adult bears will live until they die of old age when this occurs and the population will be doomed. Scientists are concerned that as the amount of Arctic ice begins to shrink, this trend is also beginning to occur in the more northern polar bear populations.

Threats for Polar Bear lives

• Global warming around the globe (pack ice melting, less hunting time)

• Ocean emissions (poisonous chemicals, crude oil)

• Overfishing (less food for the seals)

• Disturbances caused by raw material extraction, military use, shipping, tourism

• Company Hunts (in some populations)

• Illegal trade in the products of polar bears (e.g. gall bladders)

Conservation

Because of climate change, polar bears are in extreme danger of going extinct. In 2008, because of expected climate change, the polar bear became the first vertebrate species to be listed under the U.S. Endangered Species Act as threatened. The Secretary of the Interior classified the polar bear as endangered but limited the protection of the Endangered Species Act, and so the survival of the polar bear is still very much at risk. The loss of its sea ice habitat due to climate change is the greatest threat to the polar bear. In fact, as its particular scientific name (Ursus maritimus) implies, the polar bear is a marine mammal that spends much more time at sea than it does on land. The polar bear is making a living on the Arctic ice, which is why climate change is such a significant threat to its well-being. Polar bears are being affected in many ways by climate change.