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Polar Bear Photos (Ursus maritimus)
Of all mammals, the Polar bear captures the imagination as the great lord of the Northern Hemisphere. It's solitary existence in remote and severe locations provoke mystery and intrigue. As the top trophic level carnivore in the remote arctic, they have uniquely adapted to this harsh and unforgiving environment.
Polar bears and brown bears evolved from a common ancestor and are still closely related, as demonstrated by matings and production of fertile offspring in zoos. Polar bears are similar in size to large brown bears.
Adaptations by the polar bear to life on sea ice include:
Cubs weigh between 1 and 2 pounds (0.5-0.9 kg) at birth. An extremely large adult male may weigh 1,500 pounds (680 kg). Most mature males weigh between 600 and 1,200 pounds (273-545 kg), and are between 8 and 10 feet (2.4-3.0 m) in length. Mature females weigh 400 to 700 pounds (182-318 kg).
Polar bears, other than family groups of females and young, are solitary most of the year. During the breeding season in late March, April and May, males actively seek out females by following their tracks on the sea ice.
Distribution and migrationPolar bears are most abundant near coastlines and the southern edge of the ice, but they can occur throughout the polar basin. They make extensive movements related to the seasonal position of the ice edge.
FoodsThe main food of polar bears adjacent to Alaska is the ice-inhabiting ringed seal. Bears capture seals by waiting for them at breathing holes and at the edge of leads or cracks in the ice. They also stalk seals resting on top of the ice and catch young seals by breaking into pupping chambers in snow on top of the ice in the spring.
Bears prey to a lesser extent on:
Polar bears occur in areas under the jurisdiction of five nations--Russia, Norway, Denmark, Canada, and the United States--and also on the high seas where jurisdiction is not clearly defined. In Alaska prior to the late 1940s, nearly all polar bear hunting was by Eskimos with dog teams. Sport hunting, sometimes with the use of aircraft, started in the late 1940s and continued through 1972. In 1972 the state of Alaska prohibited the use of aircraft in polar bear hunting. With the passage of the Statehood Act, Alaska began a polar bear management program. State regulations required sealing of skins, provided a preference for subsistence hunters, and protected cubs and females with cubs.
The federal Marine Mammal Protection Act (MMPA)
The MMPA of 1972 transferred management authority from the state to the federal government and placed a moratorium on hunting of marine mammals by people other than Alaska Natives. This resulted in a reduced total harvest, but an increase in the proportion of female bears and cubs. The MMPA includes provisions that allow for waiver of the moratorium or transfer of management authority back to states. At intervals since 1972, the state of Alaska has made efforts at regaining polar bear management. State management could allow a resumption of sport hunting and produce increased economic opportunities in coastal rural communities. For a variety of reasons, efforts to regain state management have been discontinued. Polar bear meat, other than that of males in the rut, is quite palatable when boiled. It is a favored subsistence food in some areas. Meat should be cooked thoroughly before eating as polar bears have a high incidence of trichinosis, the round worm which occurs in pork and in other bear species.
Representatives of the five polar bear nations prepared an international agreement on conservation of polar bears in November 1973. The pact was ratified in 1976. It allows bears to be taken only in areas where they have been taken by traditional means in the past and prohibits the use of aircraft and large motorized vessels as an aid to taking. The agreement has created a high seas polar bear sanctuary but does not prohibit recreational hunting from the ground using traditional methods. In Canada, recreational hunting of polar bears currently provides significant economic benefits to Native people.
The stocks of polar bears in Alaska are shared with other nations and national management programs should be coordinated. In 1988, the North Slope Borough Department of Wildlife Management (representing Alaska Natives) and the Inuvialuit Game Council (representing Canadians) signed an agreement to provide for coordinated management of the Beaufort Sea polar bear stock. Negotiations are currently underway between the U.S. and Russia for an agreement on management for the Chukchi stock.
Degradation to polar bear habitat is currently of more concern than effects of hunting on populations. Human activities, especially those associated with oil and gas exploration and extraction, pose the greatest immediate threat. Oil exploration and drilling activities in denning areas could cause bears to den in less suitable areas. Oil spills from offshore drilling and transportation of oil through ice covered waters could contaminate bears and reduce the insulating value of their fur, or adversely affect animals in the food chain below them. Severe environmental conditions would hinder or prevent containment of a spill, and currents and ice movement could distribute oil over large areas.
Text by Jack Lentfer
Polar bear on sea ice in the Beaufort Sea, Arctic Ocean, off the coast of Alaska. © Patrick J. Endres
Polar bears have uniquely adapted to life in the Arctic environment. However, their population has been shrinking and scientists attribute the decrease to a warming climate and therefore habitat alterations in the Arctic. © Patrick J. Endres
Twin cubs are common among polar bears. © Patrick J. Endres
Polar bears live a solitary existence most of the year. © Patrick J. Endres
Polar bears are well insulated from the cold by nearly 4 inches of blubber.© Patrick J. Endres
Polar bears play in Churchill, Manitoba, CANADA © Patrick J. Endres
Polar bear coexist with Alaska native villages. © Patrick J. Endres
Degradation to polar bear habitat is currently of more concern than effects of hunting on populations. Human activities, especially those associated with oil and gas exploration and extraction, pose the greatest immediate threat. © Patrick J. Endres