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Polar Bears can be found in all of the northern regions of the world. This includes Russia, Norway, Greenland, the United States and Canada. They inhabit Arctic Sea ice, water, islands, and continental coastlines. Polar bears prefer sea ice habitat with leads, next to continental coastlines or islands. Air temperatures in the Arctic average - 34 C in winter and 0 C in summer. The coldest area in winter is northeastern Siberia, where the temperature has been recorded as low as - 69 C.
The ocean temperatures in the Arctic are about - 1. 5 C in summer and in winter the ocean temperatures can drop to 2 C, at which point seawater freezes. There are about 6 - 7 different types of Polar Bears and their differences stem from the fact that the different types grow up in different regions. These groupings have developed as a result of separate ice movement patterns. It is estimated that there are currently somewhere between 20, 000 and 40, 000 Polar Bears. The Polar Bear is a large mammal and is one the largest of the bear family. They have short, fur covered ears and a very short tail.
This heavy fur varies from pure white to more of a yellow hue in color. The white fur is important camouflage for the bears as they hunt their prey on the ice flows. The coat consists of two layers, an undercoat of fine white hair and an outer coat composed of long guard hairs. The actual color of the skin of a Polar Bear is black. The forepaws on a Polar Bear are very large, with a diameter approaching 30 centimeters, and partial webbing between their toes enabling them to propel rapidly through the water. In general, adult Polar Bears stand approximately 1 meter tall when on all fours and have an approximate body length from nose to tail of 250 to 350 centimeters.
Females typically weigh in the area of 300 kilograms where as males are generally larger and usually weigh 500 to 600 kilograms. Polar bears are able to attain speeds of 40 kilometers per hour for short distances and have a life span of 15 years to 30 years in the wild. Polar Bears are almost exclusively meat eaters and top the food chain in the arctic. They like to eat animals such as the ringed seals, bearded seals and the walrus pup. Polar Bears can also go weeks between meals because heir large stomach capacity is designed to allow them to take advantage of unexpected large meals which will to tide them over during the slower months when food might be hard to find. When the ice has melted during the summer and early fall, the bears are stranded on land.
During this period of limited food sources, the bears will try to minimize their weight loss by scavenging the shoreline and a short distance inland for washed up carrion, bird eggs, rodents, berries and anything else that is edible. They also act as scavengers, and will eat the dead bodies of seals, whales, or anything else that washes up. Starvation is not a cause of death for Polar Bears because of their ability to store body fat, which enables them to go long periods without food. Pregnant Polar Bear females are the only polar bears who will enter a winter den and hibernate for any length of time. Other bears will occasionally build a temporary shelter to overcome an extremely severe winter storm or to avoid summer heat and insects. As with other bears, the pregnant female will try to put on as much reserve fat as possible in order to have the resources to hibernate, bring her embryos to term and then nurse the newborn cubs until she leaves the den and is once more able to eat.
The pregnant Polar Bear will usually dig a maternity den into a south-facing slope a short distance inland from the coast. The den is usually an oval chamber 2 to 3 meters connected to the surface by a long entrance tunnel. Within the chamber, the temperature may rise above freezing due to the heat given off by the mother and the excellent insulating qualities of snow. While hibernating, a bears heart rate drops from between forty to seventy beats per minute to only eight to twelve beats per minute and metabolism slows down by half.
Its body temperature only undergoes a minor reduction of 3 to 7 degrees Celsius. During the period of hibernation, the Polar Bear will neither pass urea or solid fecal waste. While urea poisoning causing death would occur in all other animals within a week, bears have developed a unique process of recycling the urea into usable proteins. During the hibernation period, all bears lose a great deal of weight. Female Polar Bears normally become sexually mature in their fifth or sixth year while males in their eighth year.
Mating normally occurs out on the pack ice between late March and mid-July. Females will mate with a number of males over the approximate three weeks of the breeding season. The mother will enter the den in October or November with the cubs being born sometime in December or January while the mother is still hibernating. The number of cubs born normally ranges from one to four with two cubs being average. At birth, the cubs are blind, toothless, hairless and very tiny. They weigh approximately 600 to 700 grams, roughly the size of a chipmunk.
Virtually helpless they are still able to move sufficiently to suckle on their mother who remains asleep. Her milk is very rich containing over 40 % fat. Within the next several weeks, the cubs will develop rapidly on this rich diet so that they will be able to follow their mother when she leaves the den in late March or early April. Six out of ten polar bears die in their first year, due to starvation, accidents, or attacks. Females with cubs will avoid other adult male Polar Bears, due to the risk of attack from the males but will protect the cubs if pursued.
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