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Polar Bears Essay Polar bears are found in the Northern hemisphere inside the US, Canada, Russia, Denmark and Norway. It is estimated that there are twenty thousand to twenty five thousand polar bears in the world. Adult male polar bears can measure eight to ten feet tall with a weight of two hundred and fifty to seven hundred kilograms. Adult female bears are much smaller weighing ninety to three hundred and twenty kilograms. Seals are the primary prey of the polar bear. The ringed seal is the favorite diet of the polar bear. Polar bears usually eat only the fat if hunting is good and leave the rest of the carcass for scavengers. Polar bears are also known to eat walrus and beluga whales. They have been known to hunt reindeer, birds, kelp and beached whales. The polar bear is at the top of the food chain in the Arctic. It helps to maintain the balance of nature by preventing the overpopulation of seals. The average life span of a polar bear is between fifteen to eighteen years. Some bears have been found to live until their thirties (Bruemmer 23,1989). Female polar bears have two cubs in a litter. They have one of the slowest reproductive rates of any mammal. The cubs are born in snow dens called maternity dens. Scientists have recognized that there an estimated nineteen distinct populations of polar bears without any subspecies. Polar bears do not have enemies but they might view humans as potential adversaries. The biggest threat facing the polar bear is the change in the climate. Polar bears are adapted to survive in the harsh conditions of the Artic where the temperatures can plunge to -50 F. Polar bears have two layers of fur which provide good protection and insulation that prevents any heat loss. They also have a thick layer of blubber which measures four inches (Matthews 41, 1993). Another adaptation of the polar bear is the compact ears and small tail which prevent heat loss. While being protected from the cold, they experience problems with overheating which can occur even in cold weather. Polar bears have small bumps called papillae which help protect their feet from slipping on ice. They have strong powerful claws that allow them to catch seals. They have a powerful nose enough to detect prey which is miles away (Hemstock 63, 1999). The polar bear can adapt to the harsh environment of the Arctic because it has a thick fur coat which provides protection. Long and dense guard hairs are present outside the thick fur coat. An undercoat consists of short woolly hairs in the polar bear. Sunlight can directly make contact with the polar bear’s skin using guard hairs which act as hollow tubes. The color of the bear’s skin inside is black while from the outside it looks white. The dark skins help in absorption of heat. The layer of blubber under its skin helps keep it warm in icy water as well as on land. For human beings, the Arctic appears to be a harsh environment but for animals like the polar bear with the correct adaptations, it does not become a harsh environment for them. Polar bears live in an environment which is characterized by the freezing of the ocean which forms sea ice. The bear has paws which provide a good grip on the slick and cold surface. It helps in keeping the footing on slippery ground. Another adaptation of the polar bear is the rough pads which gives it a non slip grip. The bear ensures its feet are warm because of the thick fur between the pads. The front paws have sharp and curved claws which act like hooks that provide climbing abilities to the polar bear on ice. They also help in digging in the ice while hunting seals. Although polar bears do not hibernate in the true sense, some bears especially female pregnant bears can dig dens and hibernate. They give birth to cubs inside the dens in early winter. They stay inside the den till spring. The den’s temperature can be around forty degrees Fahrenheit because of the presence of a warm and big bear.   Hibernation is an adaptation by the polar bear which they usually do when storms and blowing snow make travel and hunting difficult (Lockwood 23, 2006). They curl up and let the snow cover them. They find themselves being warm inside the snow as compared with the air. Polar bears have a yellowish shade to their coats which can occur due to staining from seal oils. This coat allows it to blend with the snow covered environment. It is an important hunting adaptation by the polar bear in the harsh environment of the Arctic. The front legs are bowl legged and pigeon toed which is another protection from slipping on the ice. The marine environment in which polar bears live has made them evolve many adaptations to survive. They have white coloration which helps camouflage them and gives them an advantage during hunting of seals. They have water repellent guard hairs and dense under fur which helps in absorbing heat. Polar bears have the ability to make a solid grip on slippery ice using small suction cups on the soles of their feet.   Teeth of the polar bears are suitable for a carnivorous diet. Their ability to store huge amounts of fat helps protect them during food scarcity (Sage 147, 1986).   They have teeth which are specialized for a carnivorous rather than omnivorous diet. This storage capacity can help for feeding purposes if hunting season is not good. While seals are the favorite food of polar bears, walruses and whales can also be hunted and eaten by them. They can even eat carcasses and carrion of whale and seals which are found along the coast. They have excellent swimming abilities which help them cross bays or leads. Their swimming abilities are powerful as they enable the bear to swim over long distances. Research conducted by scientists has found out that polar bears can swim continuously for one hundred kilometers (Rosing 78, 1996). The front paws can help propel them through the water. Flat hind feet and legs help the polar bear to use them as rudders. The polar bear can stay warm inside the cold water due to the thick layer of blubber. Polar bears can attain a swimming speed of ten kilometers per hour. They can remain underwater by closing their nostrils. They catch their prey by making shallow dives inside the cold water. They swim under water of depths of three to four meters. They can remain underwater for a time period of two minutes (Domico 25, 1988). The body temperature of a polar bear is normally ninety eight degree Fahrenheit.   Temperature regulation is achieved by the thick layer of fur and tough hide. Additional heat regulation is attained by insulating layer of blubber. Insulation is so powerful that even during temperature drops the bear remains warm. However the problem of overheating remains because of the strong insulation. In order to prevent their bodies from getting overheated, the polar bears periodically take rests and move at a slow speed. The polar bear can release excess heat from the body in areas where the fur is absent like nose, ears, inner thighs and shoulders. Excess heat can also be released through blood vessels which are closer to the skin (Dalziel 14, 1994). Swimming is an adaptation by the polar bear by which they can cool themselves during hot days or after physical activity. Polar bears enter a state of carnivore lethargy which is similar to hibernation. Their vital body functions continue and the body temperatures remain constant during carnivore lethargy. The body temperature drops slightly as the female polar bear fasts throughout hibernation. They may lose most or all of their fat stores. Research has concluded that polar bears which do not hibernate during times of food shortages can efficiently use their energy reserves like hibernating bears. The harsh environment of the Arctic has resulted in the polar bear using many adaptations to the challenges of such an environment. Scientists have appreciated how polar bears using their adaptations can survive for two decades or more on the glacial ice of the Arctic Circle (Derocher 140, 1990). The grizzly bear is found in the jungles, streams and mountains of western North America. Compared with the polar bear, the grizzly bear is found in the uplands of western North America. It is a solitary animal which lives near streams, lakes and rivers. Females produce one or four young cubs which hare small. They can reach weights of one hundred and eighty kilograms. They have hind legs as males are larger than females. The huge size of the bear helps in attracting females for breeding purposes. The color of the grizzly bear is different from the polar bear due to the different environments with regard to diet and temperature (Lyman 23, 1982). The grizzly bear has powerful digging abilities because of the large hump over its shoulders. Grizzly bears have large round heads which provide good running speeds for them. They are slower running downhill because of the large hump of muscle over their shoulders. Grizzly bears have longer claws and cranial profiles as compared with the polar bear. Grizzly bears tend to eat eighty to ninety pounds of food per day to allow it to hibernate in the winter. It can build beds under branches or dig holes under the ground which is an adaptation that allows it to be protected without the need for food. Grizzly bears have long claws as compared with polar bears as they need to catch salmon and dig. It gives the grizzlies an easier time to catch food for its young cubs and itself. Like polar bears they have also developed a keen sense of smell to find food for their young cubs. They do not have good eyesight as compared with polar bears. The grizzlies have adapted to their less harsh environment by having a good sense of smell which allows them to sniff out things (Nowak 52, 1991). The harsh arctic environment of the polar bear has forced it to create many adaptations which help to ensure its survival. The polar bear’s favorite prey is the seal. It helps to prevent the overpopulation of the seal. Sometimes polar bears can also eat carrion and carcasses of seals and whales which come across the coast. Polar bears have excellent swimming skills which allow them to swim at high speeds. They can swim for many long hours and remain underwater for a time period of two minutes. They use their diving skills to look for prey. They have small suction cups which provide good traction during slippery grounds. The polar bear can adapt to the harsh environment of the Arctic because it has a thick fur coat which provides protection. Long and dense guard hairs are present outside the thick fur coat. Polar bears have a yellowish shade to their coats which can occur due to staining from seal oils. This coat allows it to blend with the snow covered environment. It is an important hunting adaptation by the polar bear in the harsh environment of the Arctic. Compared with grizzly bears, the polar bear has different adaptations because of the different environments in which they live. References: Bruemmer, Fred (1989). World of the Polar Bear. Toronto, ON: Key Porter Books. Matthews, Downs (1993). Polar Bear. San Francisco, CA: Chronicle Books. Hemstock, Annie (1999). The Polar Bear. Manakato, MN: Capstone Press. Lockwood, Sophie (2006). Polar Bears. Chanhassen, MN: The Childs World. Rosing, Norbert (1996). The World of the Polar Bear. Willowdale, ON: Firefly Books Ltd.. Derocher, A.E. and I. Stirling. Observations of aggregating behaviour in adult male polar bears (Ursus maritimus). Canadian Journal of Zoology 68, 1990 Dalziel, Ian W.D. Arctic. The World Book Encyclopedia. Chicago: World Book, Inc., 1994. Domico, Terry. Bears of the World. New York: Facts On File, 1988. Lyman, C. P., et al. Hibernation and Torpor in Mammals and Birds. New York: Academic Press, 1982. Nowak, Ronald M., ed. Walkers Mammals of the World. 5th edition. Volume 2. Baltimore: The Johns Hopkins University Press, 1991. Sage, Bryan. The Arctic and its Wildlife. New York: Facts On File Publications, Inc., 1986