Polar Bears

Polar bears are the largest carnivorous land mammals on Earth. A polar bear goes by many different names around the world. The Science community labels them Ursus maritimus (meaning sea bear). Indigenous people from the northern Europe call them "God's Dog" or "Old Man in the Fur Cloak." Inuit call them "Nanuk" (The ever-wandering one) Siberian tribes call them "Gyp" (meaning grandfather) Russia calls them "Beliy Medved" (the white bear)." Norway and Denmark call them "Isbjorn" (the ice bear).Polar bears are classified as marine mammals because they spend most of their lives on the sea ice of the Arctic Ocean. They have a thick layer of body fat and a water-repellant coat that insulates them from the cold air and water. Considered talented swimmers, they can sustain a pace of six miles per hour by paddling with their front paws and holding their hind legs like a rudder. They travel long distances over vast desolate expanses, generally on drifting oceanic ice flows, searching for seals, its primary prey. The polar bear has no natural predators and knows no fear of humans, making it an extremely dangerous animal.

Recent scientific findings suggest that polar bears evolved from a common ancestor of the brown bear between 350,000 - 6 million years ago. After beginning to branch off, the polar bear's ancestors went through a series of evolutionary changes in order to survive in the Arctic.Polar bears are stocky, with a long neck, relatively small head, short, rounded ears and a short tail. The male, which is much

larger than the female, can weigh up to 1,700 pounds, while a large female is about half that size. It grows to about 5.3 feet tall at the shoulders and 7.2 -8.2 feet in length. Sunlight can pass through the thick fur, where the heat can absorb into the bear's black skin.

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Life of the Polar BearMany of the polar bear's physical adaptations help it maintain body heat and deal with its icy habitat. The bear's outer layer of fur is hollow and reflects light, giving the fur a white color that helps the bear remain camouflaged. The skin under the polar bear's fur is actually black; this black is evident only on the nose. Polar bears also have a thick layer of fat below the surface of the skin, which acts as insulation on the body to trap heat. This is especially important while swimming and during the frigid Arctic winter. The polar bear's footpads have a kind of "non-slip" surface, allowing them to

get traction on slippery ice. They have strong legs and large, flattened feet with some webbing between their toes, which helps with swimming and walking on ice. The wide paws prevent sea ice from breaking by distributing the polar bear's weight as it walks. Strong, sharp claws are also important for gaining traction, digging through the ice and killing its prey. The webbed feet results in making polar bears unlike other bear species. They are considered marine animals along with seals, sea lions, walruses, whales and dolphins. However, they are still bears!Polar bears are different from their ancestors. Most polar bears don't den, however all brown bears do. Grizzly bears must den during the winter when their food is covered in snow, but polar bears have access to their food of choice (seals) all winter long, so there is no need for them to den. The exception to this is pregnant adult females. They must den so that their tiny newborn cubs are born in a warm protected environment. The cubs would otherwise freeze to death in the frigid temperatures of the far north. Most polar bears live north of the Arctic Circle to the North Pole. There are some

populations south of the Arctic Circle in the Hudson Bay of Manitoba, Canada. Polar bears live in Alaska, Canada, Russia, Greenland, and some northern islands owned by Norway.

Have you seen a polar bear in the wild or in a zoo?

What characteristics did you see?

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Polar Bear HabitatPolar bears depend on the sea ice, which forms above the open waters where their seal prey live. They spend over 50% of their time hunting for food. They are solitary and overwhelmingly carnivorous, feeding especially on the Ringed seal but also on the bearded seal and other aquatic mammals. The bear stalks seals resting on the ice, ambushes them near breathing holes and digs young seals from their snow shelters where they are born. Polar bears prefer ice that is subject to periodic fracturing by wind and sea currents, because these fractures offer seals access to both air and water. As their prey is aquatic, polar bears are excellent swimmers and

they are even known to kill beluga whales. In swimming, the polar bear uses only its front limbs. They are opportunistic as well as predatory; they will consume dead fish and carcasses of stranded whales and eat garbage near human settlements. Polar bears breed in the late spring as the temperatures begin to rise in the Arctic. They live solitary lives except when mating. However they don't really become pregnant at the time of breeding as the tiny embryo

will not implant in the female's uterus until fall, when true gestation begins. This is called delayed implantation and allows a female bear to physiologically asses her condition prior to starting gestation and the process of birthing, nursing, and carrying for her offspring for the next three years. The period of actual gestation following implantation is only about 60 days. For reproduction to continue, the female must achieve a body weight of at least 490 pounds to have the blastocyst (which develops into the embryo) implant and start gestation. If the threshold is not achieved, the blastocyst will reabsorb and the female will continue to get fatter for the next year to be able to acheive a successful pregnancy. Females dig a den in a snow bank and begin the process of gestation. She will enter the den anytime between early October and December. She exits the den between late February and April. Litter size is most commonly two cubs, but sometimes litters can be one, three or very rarely four cubs.

How does the delayed implantation benefit the mother and her cubs?What do you think are the dangers for polar bears?

How do you think climate change is affecting the polar bears?

Polar Bear PopulationsPolar bear population sizes and trends are difficult to estimate accurately because they occupy remote habitats and exist at low population densities. Polar bears are listed as "vulnerable" which indicates an expected population decrease of greater than 30% over the next three generations (abt. 34.5 years) due to the decline in their habitat and the quality of that habitat. Risks to the polar bear include climate change, pollution in the form of toxic contaminants, conflicts with shipping, oil and gas exploration and development, and human-bear interactions including harvesting and possible stresses from recreational polar-bear watching.

Climate Change:A recent study examining the population of the polar bear subpopulation in northeast Alaska and Canada have shown a 40% population loss due to the loss of sea ice caused by climate change. How does climate change affect polar bears so dramatically? Polar bears rely on sea ice to access the seals that are their primary source of food as well as to rest and breed. Polar bears hunt seals from a

platform of sea ice. Rising temperatures cause the sea ice to melt earlier in the year, driving the bears to shore before they have built sufficient fat reserves to survive the period of scarce food in the late summer and early fall. Reduction in sea-ice cover also forces bears to swim longer distances, which depletes their energy stores and occasionally leads to drowning. Thinner sea ice make it more difficult for polar bears to access the seals. Insufficient nourishment leads to lower reproductive rates in adult females and lower survival rates in cubs and juvenile bears, in addition to poorer conditions in bears of all ages.

Current Population:22,000 - 31,000

Worldwide estimate

Pollution:Polar bears accumulate high levels of organic pollutants such as polychlorinated biphenyl (PCBs) and chlorinated pesticides. PCBs cause birth defects and immune system deficiencies. Polar bears are at the top of the food chain with a heavy diet in blubber in which pollutants concentrate. Their bodies are among the most contaminated of Arctic mammals. PCBs and DDT have been internationally banned due to recognition of their harm on the environment. Their concentration in polar bear tissues continued to rise for decades after being banned as these chemicals spread through the food chain. The most recent study from 1996-2002 showed that DDT was only notably lower in the Western Judson Bay population...and nowhere else. Oil and Gas Development:Oil and gas development in polar bear habitats can affect the bears in a variety of ways. An oil spill in the Arctic would most likely concentrate in the areas where the polar bears and their prey live. Oil on the coats of the polar bears reduces their insulation value and put the bears at risk of dying from hypothermia. Bears licking their fur covered in oil causes death due to fatal kidney failure. Maternity dens used by pregnant females and by females with infants can also be disturbed by nearby oil exploration and development. The dens are sensitive sites and may trigger the mother to abandon her den prematurely, or abandon her cubs altogether. Human-Polar bear conflict:As powerful predators, polar bears pose a major risk to human life and property. Throughout the polar bear's range, attacks on humans and property continue to rise. In recent years, more than 20 attacks on humans have been reported within the polar bear's range. The powerful sense of smell attracts the bears to human waste, stored food, dog teams and animal carcasses. Climate change is causing the ice to melt, bringing the bears closer to shore. The bears can smell the settlement, dog food and dump site. The dramatic solution to the problem is to shoot them, which is legal when in defense of life or property. But given the pressures that polar bears are facing, it's vital to have non-lethal options. Many communities have launches a "polar bear patrol." Their goal is to drive away problem animals rather than having to shoot them. Today, Alaska, Canada, Greenland and Russia have polar bear patrols. The settlements are also working on making it less attractive to bears. Their main area is the town dump, a feast for starving bears. The towns have incorporated an incinerator and are trying to pack and ship out bear enticing waste.

What suggestions do you have to decrease polar bear and human conflict?

PredictionsThe U.S. Geological Survey scientists have predicted two-thirds of the world's polar bears may disappear by 2050, based on moderate projections for the shrinking of summer sea ice caused by climate change. Of course the prediction is hotly debated. Polar bears diverged from brown bears 400,000 to 600,000 years ago and have survived past periods of climate fluctuation. It has been claimed that polar bears will be able to adapt to terrestrial food sources as the sea ice they used to hunt seals disappears. However, most polar bear biologists think that polar bears will be unable to completely offset the loss of calorie-rich seal blubber with terrestrial foods, and that they will be outcompeted by brown bears in this terrestrial niche, ultimately leading to a population decline.

Controversy over species protection.Warnings about the future of the polar bears are often contrasted with the fact that worldwide

population estimates have increased over the past 50 years and are relatively stable today. Some estimates of the global populations were around 5,000 to 10,000 in the early 1970s, other estimates were 20,000 to 40,000 during the 1980s. Current estimates put the global population at between 20,000 and 25,000 or 22,000 and 31,000.There are several reasons for the apparent conflict between past and projected population trends. Estimates from the 1950s and 1960s were based on stories from explorers and hunters rather than scientific surveys. Second, controls on harvesting were introduced that allowed this previously over-hunted species to recover. Third, the recent effects of climate change have affected sea ice abundance in different areas to varying degrees. Debate over the listing of the polar bears under endangered species legislation has put conservation groups and Canada's Inuit population at opposing positions. The Nanuvut government and many northern residents have condemned the U.S. initiative to list the polar bear under the Endangered Species Act. Many Inuit believe the polar bear population is increasing and restrictions on commercial sport-hunting are likely to lead to a loss of income to their communities. They believe polar bear numbers are increasing because they are seeing more bears on land. But studies show the increased observations of bears on land are the result of changing habitat patterns and loss of sea ice, driving them towards land for survival and food.

1. Should the U.S. have the right to protect the polar bears and put them on the Endangered Species Act list, when it affects the indigenous tribes in the Arctic?2. What ways can we help protect the polar bears?3. Should the indigenous tribes be allowed to continue to hunt the polar bear?4. Do you think the polar bears will have difficulty adapting to their changing environment?5. Should sport-hunting for polar bear trophies be allowed?

Curious Dragonfly LLCTrina Terrellwww.curiousdragonfly.com303.903.5319

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