Home is on the sea ice. A polar bear's home range can be enormous—far greater than any other species of bear. The size of a polar bear's range depends on two main factors: habitat quality and availability of seal prey.
Polar bears respond to seasonal changes and the distribution of seals and sea ice. In food-rich areas, they have smaller home ranges and their habitat often overlaps with other bears.
A Polar Bear’s Home Range
Polar bears in sea ice regions with hard-to-reach prey travel farther and have longer fasting periods.
Unlike other large carnivores, polar bears don’t have territories, partly because their sea ice habitat is always moving and seasonally changing.
When a young polar bear grows up, it may travel more than 1,000 kilometers to set up a home range apart from its mother's, although subadult dispersal remains a scarcely studied topic, because tagging and tracking a quickly maturing animal is tricky.
Scientists believe that most polar bears limit travel to home ranges of a few hundred miles. However, they know of one satellite-tracked female that trekked 4,796 kilometers —from Alaska's Prudhoe Bay to Greenland to Canada's Ellesmere Island and back to Greenland.
The Four Sea Ice Regions
Polar bears need a platform of sea ice to more easily reach their seal prey. But, not all sea ice is equal.
A World Of Ice
Some sea ice lies over productive hunting areas, and some ice regions will melt sooner than others in a warming Arctic.
Governments and scientists have designated 19 populations of polar bears based in four different sea ice regions in the North Circumpolar Region (the Arctic).
These sea ice regions function as distinct management units and are spread out among five countries: Canada, the United States (Alaska), Greenland, Russia, and Norway.
Roughly 60% of polar bears call Canada home.
The following four sea ice ecoregions differ in geography, status, sea ice levels, and vulnerability to climate change.
1. Seasonal Ice
Baffin Bay, Davis Strait, Foxe Basin, Southern Hudson Bay, and Western Hudson Bay
Seasonal ice areas occur at the southern extreme of the polar bear's range and include places like Canada's Hudson Bay, where the ice melts completely each summer and the bears must wait for freeze-up in the fall until they can hunt again.
Status of these populations: Polar bears in seasonal ice areas are the most endangered, with longer and longer ice-free seasons testing the limits of their fat reserves.
2. Polar Basin Divergent Ice
Barents Sea, Chukchi Sea, Kara Sea, Laptev Sea, and the Southern Beaufort Sea
In these areas, sea ice forms along the shore and then retreats, especially in summer. As the sea ice retreats farther and farther from shore in a warming Arctic, these polar bears are faced with a choice of coming ashore—and fasting until the ice returns in the fall—or swimming long, exhausting distances to reach the remaining pack ice.
However, because ice located far offshore lies over less productive waters, bears in these areas may successfully complete a marathon swim yet still not find any seals to hunt.
Status of these populations: Polar bears that live in these areas are at great risk—from longer and longer swims, prolonged fasting periods, and encounters with humans on shore.
3. Polar Basin Convergent Ice
Eastern Greenland, Northern Beaufort Sea, and the Queen Elizabeth Islands
Sea ice formed locally and transported from other parts of the Arctic collects along the shore of these habitats, providing polar bears with access to seals over productive waters.
Status of these populations: Polar bears in these areas are faring well now, but scientists predict that ice in these areas will disappear within 75 years—and, with it, resident polar bear populations—unless action is taken to reduce carbon emissions.
4. Archipelago Ice
Gulf of Boothia, Kane Basin, Lancaster Sound, M'Clintock Channel, Norwegian Bay, and the Viscount Melville Sound
Islands in the Canadian High Arctic and Greenland are far enough north that sea ice remains along the coast even in summer, providing hunting grounds for the bears.
Status of these populations: This ecoregion is likely to provide a last refuge for polar bears and their sea-ice prey, but ultimately it too is threatened, without action on climate change.
Why does it help to divide the Arctic into sea ice regions?
It allows scientists to make informed estimates about how a population is faring, based on the health and condition of well-studied populations within the same region or across various regions.
It’s the best tool for making comparisons.
Getting Around The Arctic
Polar bears are natural travelers in the Arctic. Here we take a look at the way polar bears make their moves across the sea ice.
Well known for their slow, plodding gait, polar bears walk at about five to six kilometers per hour. Females with small cubs walk more slowly, about two-and-a-half to four kilometers per hour.
Polar bears are able to gallop as fast as a horse over short distances but prefer to amble leisurely.
Norwegian scientist Nils Oritsland showed us that polar bears expend more than twice the energy of most other mammals when walking or running, showing higher-than-average increases in temperature and in oxygen consumption.
Walking bears expend 13 times more energy than resting bears. This partly explains their preference for still-hunting, which usually involves a long, patient wait for a seal to surface at a breathing hole in the sea ice.
Polar bears are natural sprinters and can run as fast as 40 kilometers per hour—but only for short distances.
Younger, leaner bears are the best runners. They can cover two kilometers without stopping, whereas older, larger bears will quickly overheat.
Sharing The Arctic
Polar Bear FAQ
Are polar bears endangered?
Polar bears are listed under a variety of classifications depending on international, national, and regional regulations. Internationally, they are listed as a vulnerable species by the IUCN. In Russia, polar bears are classified as a Red Data Book species, a listing that includes animals considered rare or endangered. In the U.S., polar bears are listed as a threatened species under the Endangered Species Act. Canada considers polar bears a species of special concern under the National Species at Risk Act. On a regional level in Canada, polar bears are listed as threatened in both Manitoba and Ontario under provincial endangered species legislation.
In all cases, the primary conservation concern for polar bears is habitat loss and reduced access to their seal prey due to climate change. Scientists predict that as the Arctic continues to warm, two-thirds of the world's polar bears could disappear within this century. Research also shows that hope remains if action is taken to greatly reduce greenhouse gas emissions soon.
While rapid loss of sea ice is the primary threat to the polar bear’s long-term survival, other challenges include pollution, increased commercial use of the Arctic, overharvest, disease, and inadequate habitat protection (denning and seasonal resting areas).
At the 2014 meeting of the PBSG, the world's leading polar bear scientists reported that of the 19 subpopulations of polar bears, three were declining, six were stable, and one was increasing. They lacked sufficient data on the status of the remaining nine.
How many polar bears are there?
Scientists can only provide informed estimates. The latest IUCN report estimates there are approximately 26,000 of them.
How big are polar bears?
Very big! Adult males normally weigh 350 to more than 600 kilograms (775 to more than 1,300 pounds). Adult females are smaller, normally weighing 150 to 295 kilograms (330 to 650 pounds). Researchers in Canada estimated one male bear at 800 kilograms (1,700 pounds)!
Scientists usually refer to how tall bears are by measuring them at the shoulder when on all fours. Those heights are typically 1-1.5 meters (3.3-5 feet) for adult polar bears. An adult male may reach over three meters (10 feet) when standing on its hind legs.