Polar Bears

Polar bears inhabit Arctic sea ice, water, islands, and continental coastlines

Biologists estimate their population at 22,000 to 27,000 bears, of which around 15,000 are in Canada.

Class: Mammalia (Mammals)
Order: Carnivora
Family: Ursidae
Genus: Ursus
Species: maritimus
Shoulder height: up to 5.3 feet (1.6 meters)
Length: 6.6 to 10 feet (2 to 3 meters)
Weight: males—660 to 1,760 pounds (300 to 800 kilograms); females—330 to 660 pounds (150 to 300 kilograms)
Life span: 25 to 30 years in the wild, up to 45 years in zoos
Gestation: 6.5 months
Number of young at birth: 1 to 4, with two being the average
Size at birth: 1.3 pounds (.6 kilograms)
Age of maturity: males—10 to 11 years; females—5 to 6 years

•  Order - Carnivora-The scientific order Carnivora includes bears, dogs, cats, raccoons, otters, weasels, and their relatives. All typical carnivores have well developed claws and a pair of specialized cheek teeth for cutting hard foods. 
•  Family - Ursidae- All bears belong to this family. The family is divided into three subfamilies, Ursinae (black bears, brown bears, polar bears, sloth bears, and sun bears), Tremarctinae (spectacled bears), and Ailuropodinae (giant pandas).
• Genus, species - Ursus maritimus. 
  •  There are five other species in the genus Ursus: brown bears, American black bears, Asiatic black bears, sun bears, and sloth bears. Species can be distinguished by size, build, coloration, and habitat.
  • . Ursus maritimus is Latin for "sea bear".

From United Nations Environment Programme (UNEP)

Polar bears spend much of their time at or near the edge of the pack ice. This is where they are most likely to find food. As the southern edge of the arctic ice cap melts in summer, some bears will follow the retreating ice north to stay close to seals and other prey. Other bears spend their summers on land, living off body fat stored from successful hunting in the spring and winter. When the ice returns in the fall, the bears leave land to resume life on the sea ice.The world's southern-most polar bears live year-round in James Bay, Canada. The species range extends as far south as the winter maximum sea ice extent and includes adjacent land masses

The polar bear, or “Nanuuq,” as the Eskimos call it, lives only in the Northern Hemisphere, on the arctic ice cap, and spends most of its time in coastal areas. Polar bears are widely dispersed in Canada, extending from the northern arctic islands south to the Hudson Bay area. They are also found in Greenland, on islands off the coast of Norway, on the northern coast of the former Soviet Union, and on the northern and northwestern coasts of Alaska in the United States. Some polar bears may make extensive north-south migrations as the pack ice recedes northward in the spring and advances southward in the fall. They also may travel long distances during the breeding season to find mates, or in search of food.

A polar bear rides a summer sea-ice raft off Norway's Svalbard archipelago. Sea ice provides crucial habitat for the Arctic's top predator, but warming temperatures are creating extended ice-free periods that tax bears. www.visionsofthewild.com

Appearance 

The polar bear is the largest member of the bear family, with the exception of Alaska’s Kodiak brown bears, which equal polar bears in size. Males stand from 8 to 11 feet tall and generally weigh from 500 to 1,000 pounds, but may weigh as much as 1,400 pounds. Females usually stand 8 feet tall and weigh 400 to 700 pounds, but may reach 700 pounds. Part of the reason the polar bear weighs so much is that it stores about a 4-inch layer of fat to keep it warm.

The polar bear has a longer, narrower head and nose, and smaller ears, than other bears. 

Although the polar bear’s coat appears white, each individual hair is actually a clear, hollow tube. Some of the sun’s rays bounce off the fur, making the polar bear’s coat appear white. During the summer months, adult bears molt, or gradually shed their coats and grow new ones, which look pure white. By the following spring, the sunshine has caused their coats to turn a yellowish shade. Polar bears also sometimes may have a yellowish shade to their coats caused by staining from seal oils. 

Polar bears live on ice and snow, but that’s not a problem—these bears have some cool ways to stay warm!

• Hair— A dense, thick undercoat of fur is protected by an outer coat of long guard hairs that stick together when wet, forming a waterproof barrier to keep them dry. Even though polar bears look white, their hair is really made of clear, hollow tubes filled with air.
• Blubber— Blubber helps insulate polar bears from the freezing air and cold water, and acts as a nutritional reserve when food can’t be found. This blubber also helps the bears float in the water. It is 2 to 4 inches (5 to 10 centimeters) thick.
• Winter Sleep— When the temperature outside drops, many bears stay warm by making a den and sleeping. Polar bears do not hibernate, but their body functions do slow down at this time. Many scientists call this “winter sleep,” because the bears can easily be awakened. A mother polar bear can give birth and nurse her young while still in her winter sleep.

Photographer Florian Schulz watched a Svalbard male (background) stalk a female with two cubs, alert to danger

www.visionsofthewild.com

The polar bear’s coat helps it blend in with its snow-covered environment, which is a useful hunting adaptation. The polar bear’s front legs appear slightly bowllegged and pigeon-toed, and fur covers the bottoms of its paws. These adaptations help the polar bear keep them from slipping on ice.

 Feeding Habits 

Polar bears are mainly meat eaters, and their favorite food is seal. They will also eat walrus, caribou, beached whales, grass, and seaweed. Polar bears are patient hunters, staying motionless for hours above a seal's breathing hole in the ice, just waiting for a seal to pop up.

Because the polar bear rarely eats vegetation, it is considered a carnivore, or meat-eater. The ringed seal is the polar bear’s primary prey. A polar bear may stalk a seal by waiting quietly for it to emerge from its blow hole or “atluk,” an opening seals make in the ice allowing them to breathe or climb out of the water to rest. The polar bear will often have to wait for hours for a seal to emerge. Because the polar bear’s coat is camouflaged against the whiteness of the ice and snow, the seal may not see the bear. Polar bears typically eat only the seal’s skin and blubber, or fat, and the remaining meat is an important food source for other animals of the Arctic. For example, Arctic foxes feed almost entirely on the remains of polar bear kills during the winter. Polar bears also prey on walrus, but, because of the walrus’s ferocity and size, bears are usually only successful preying on the young. The carcasses of whales, seals, and walrus are also important food sources for polar bears. In fact, because of their acute sense of smell, polar bears can sense carcasses from many miles away. 

Credit: USFWS

Polar bears can cover significant distances on land, but are most agile in the sea. They are excellent swimmers, and can reach speeds of up to 6 mph in the water. They are good divers, too. When being pursued by hunters in open water, polar bears have been known to escape by plunging 10 to 15 feet below the surface and resurfacing a good distance away. They also have been seen swimming 100 miles or more from ice or land. 

Credit: Steve Hillebrand / USFWS

Reproduction 

Polar bears reach breeding maturity at 3 to 5 years of age. Males may travel great distances in search of female mates. While breeding usually takes place in April, the embryos may not implant (develop) until the following year, depending on whether the mother has had a stable enough supply of food to sustain herself while allowing her to feed the developing cubs through the winter. 

Credit: USFWS

In October and November, male polar bears begin to head out on the pack ice where they spend the winter. Pregnant females, however, seek sites on the mainland or on sea ice to dig large dens in snow where they will give birth and spend the winter. The temperature inside the polar bear’s den can be as much as 40 degrees warmer than outside. Usually two cubs are born in December or January. When the cubs first arrive, they are blind, hairless, and no bigger than squirrels. However, the cubs grow rapidly from the rich milk provided by their mother. 

As soon as spring comes, the mother bear leads her cubs to the coast along the open sea, where seals and walrus are abundant. The mother will fiercely protect her cubs from any perceived danger. The cubs remain with their mother for 2-1/4 years. Because of this, most adult female polar bears breed only every third year. 

Protection 

Polar bears have traditionally played an important role in the culture and livelihood of Eskimos and other Native people of the North. They depend on the animals for food and clothing. In the United States, polar bears are a federally protected species under the Marine Mammal Protection Act of 1972. This protection prohibits hunting of polar bears by non-Natives and establishes special conditions for the importation of  polar bears or their parts and products into the United States. Eskimos and other Alaska Natives are allowed to harvest some polar bears for subsistence and handicraft purposes. The U.S. Fish and Wildlife Service is the federal agency responsible for managing polar bears under the Marine Mammal Protection Act. 

Arctic Circle (Oct. 2003) -- Three Polar bears approach the starboard bow of the Los Angeles-class fast attack submarine USS Honolulu (SSN 718) while surfaced 280 miles from the North Pole. Sighted by a lookout from the bridge (sail) of the submarine, the bears investigated the boat for almost 2 hours before leaving. Commanded by Cmdr. Charles Harris, USS Honolulu while conducting otherwise classified operations in the Arctic, collected scientific data and water samples for U.S. and Canadian Universities as part of an agreement with the Artic Submarine Laboratory (ASL) and the National Science Foundation (NSF). USS Honolulu is the 24th Los Angeles-class submarine, and the first original design in her class to visit the North Pole region. Honolulu is as assigned to Commander Submarine Pacific, Submarine Squadron Three, Pearl Harbor, Hawaii. U. S. Navy photo by Chief Yeoman Alphonso Braggs.

 A young Polar bear stands up to get a better look at the Los Angeles-class fast attack submarine USS Honolulu (SSN 718) while surfaced 280 miles from the North Pole.U. S. Navy photo by Chief Yeoman Alphonso Braggs

As seen through the periscope of the Los Angeles-class fast attack submarine USS Honolulu (SSN 718), a young Polar bear investigates the open water around the submarine’s rudder U. S. Navy photo by Chief Yeoman Alphonso Braggs

An international conservation agreement for polar bears signed in 1976 by the United States, the former Soviet Union, Norway, Canada, and Denmark (Greenland) also provides for cooperative management of polar bears. The Fish and Wildlife Service and the United States Geological Survey’s Alaska Science Center work together to monitor polar bears in Alaska, where they number approximately 4,700, and study their behavior. Cooperative efforts with Canada involve monitoring polar bears in the Beaufort Sea, and the agencies work with the Russian government to monitor the animals in the Chukchi Sea. 

Polar bear with cub. Credit: Scott Schliebe/USFWS

Another treaty, the “Agreement between the Government of the United States of America and the Government of the Russian Federation on the Conservation and Management of the Alaska-Chukotka Polar Bear Population,” unifies the American and Russian management programs that affect this shared population of bears. Notably, the treaty calls for the active involvement of Native people and their organizations in future management programs. It will also enhance long-term joint efforts such as conservation of ecosystems and important habitats, harvest allocations based on sustainability, collection of biological information, and increased consultation and cooperation with state, local, and private interests. The Fish and Wildlife Service also undertakes education and outreach efforts to inform the public about how polar bears can be protected from over-harvest. 

Polar Bear at Cape Churchill (Wapusk National Park, Manitoba, Canada) photo taken by Ansgar Walk

Polar Bears at Risk

• The area covered by arctic sea ice is melting at an unprecedented rate. Polar bears need sea ice to access their food, and to move from hunting grounds to their denning or summer resting areas.
  
  
• Toxic chemicals transported to the Arctic from the south have long-term effects on polar bear health and longevity.
  
  
• Oil exploration in the Arctic affects polar bears by fragmenting and disturbing their habitat, and by introducing oil and other toxic substances to their environment.
  
  
• Although much of the traditional harvesting in local communities is sustainable, the main threat to polar bears in some areas is still over-hunting.

In Alaska, demands for oil, natural gas, and other resources have led to some conflicts between polar bears and humans. A number of protective measures have been taken to reduce human activities along the coast in polar bear denning areas. This is when the animals are most sensitive to outside disturbances. For example, oil and gas pipelines and roads have been routed to avoid these areas. The Fish and Wildlife Service also provides expertise to industries on how to minimize conflicts with bears while conducting their operations. Today it is estimated that there are 20,000 to 25,000 polar bears worldwide. With continued cooperative management, these great marine mammals, and the unique arctic environment on which they depend, can be protected for generations to come.

Polar bears range throughout the Arctic in areas where they can hunt seals at open leads. The five "polar bear nations" where the ice bears are found include the U. S. (Alaska), Canada, Russia, Denmark (Greenland), and Norway.

Near the North Pole (Apr. 27, 2003) -- During Exercise ICEX 2003, the Seawolf-class attack submarine USS Connecticut (SSN 22) surfaced and broke through the ice. This polar bear, attracted by the hole which can be used to find food, was seen through the sub's periscope and these photos were captured as the image was projected on a flat-panel display. After investigating the Connecticut for approximately 40 minutes, the bear left the area, with no damage to the sub or to the bear. U.S. Navy photo by Mark Barnoff

Biologists estimate their population at 22,000 to 27,000 bears, of which around 15,000 are in Canada. In 1973, the five nations with polar bear populations (Canada, Denmark, which governed Greenland, Norway, the U.S., and the former U.S.S.R.) entered into the International Agreement for the Conservation of Polar Bears. Here is what they encounter in each nation:

• In Norway, polar bears are completely protected and have been since 1973. On the glacial Svalbard islands, their population has rebounded from a low of about 1,000 to roughly 2,000 bears. Scientists are worried, however, about the effects of pollution on the bears. PCB levels in the polar bears of Norway and western Russia are two-and-a-half to seventeen times higher than those in North American populations.
• In Canada, Hudson Bay's ice melts about three weeks earlier each spring than it did just 25 years ago, which has greatly shortened the time that the bears can hunt for food. (Polar bears need a platform of ice from which to hunt seals.) Canadian scientists have observed that today's polar bears are smaller in stature, weigh less, and have fewer cubs. The bears in certain areas of Canada have excessive levels of PCBs and other contaminants. In Canada, native hunting is allowed under the provision of the International Agreement. Each community is given a quota, and natives are permitted to sell their right to hunt a bear to non-natives. Roughly 500 bears are harvested each year
• In Alaska, about 100 polar bears are harvested every year by natives under the subsistence provision of the Marine Mammal Protection Act. The only restriction in place is that if they kill a bear, the carcass must be used in some way. Natives are not allowed to sell the skins, but may make and sell products from them.
• In Greenland, which is governed by Denmark, natives may hunt polar bears but are forbidden from selling any bear parts. Roughly 100 bears are harvested each year.
• Russia's polar bears face an uncertain future. Russian natives were recently granted the right to hunt, which worries Russian scientists because the breakdown of law and order and the collapse of the Russian economy has led to widespread poaching problems. They worry that legal hunting will encourage further poaching. In addition, polar bears in western Russia are exposed to dangerously high levels of pollutants.

A polar bear cub curiously stands on its hind legs while its mother stays nearby. The two bears approached within 200 meters of the ship.
credit: NOAA

Scientists analyzing decades of data from Arctic Sea ice recently reported a significant reduction in the thickness of the ice during the last decade. The scientists found a decrease in sea ice all across the Arctic Ocean. Polar bears need sea ice so they can hunt for seals. A retreat and loss of sea ice could make it harder for these animals to get enough food. Pregnant females and those with cubs may be particularly at risk.

• Climate changes on prey species will have a negative effect on polar bears
  • increased snow can result reduced success in successfully entering seal birth lairs
  • decreased snow or increased seasonal rain patterns could effect seal pupping by not providing adequate snow for construction of birth lairs or if rain fall by collapsing birth lairs thus reducing seal productivity
  • prey reductions could effect polar bear condition and ultimately cub production and survival
• Changes that alter the period of ice coverage could affect distribution and impact polar bears
  • bears may spend greater amounts of time on land
  • extended use of terrestrial areas would ultimately effect physical condition of bears when forced to rely on fat stores
  • decreased physical condition could effect production and survival
  • bears using deteriorating pack ice may experience increased energetic costs associated with movements and swimming
• Denning could be impacted by unusual warm spells
  • access to high quality denning areas may be limited or restricted
  • use of less desirable denning habitat could have impacts on reproduction and survival
  • rain or warming could directly cause snow dens could collapse or be opened to ambient conditions
  • loss of thermal insulative properties in opened dens could effect litter survival

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Credit: U.S. Fish & Wildlife Service, San Diego Zoo, Sea World, NOAA, International Bear Association, United States Navy