Habitat Connectivity

Yes, this is a grizzly bear blog, but did you know that polar bears are very closely related to grizzly bears? They have evolved from brown/grizzly bears only over the last 250,000 years to become one of the most perfectly adapted creatures on the planet.

I guide expeditions to the far north each year to the Norwegian arctic islands of Svalbard – just 600 miles from the north pole. It’s an incredible landscape – surely one of the most beautiful in the world. But the most special thing about this isolated jewel is the population of polar bears that call it home. We generally see up to forty polar bears during each 10 day expedition, many of them hunting for ringed and bearded seals on the last remaining ice of the summer months.

2006 saw a surprising lack of summer ice – in fact, the pack was 100 miles further north than an average year, which meant that bears were more densely gathered around the few remaining sections of fast ice. It was a blunt reminder of the effects of climate change. I photographed the female and cubs below as they hunted seals on a quickly-shrinking piece of ice. Polar bears can not hunt successfully without ice – access to the prized ring seals generally happens in one of two ways – lying in wait over a seal’s breathing hole, or stalking across the ice in a surprise attack. Once the winter ice has disappeared the bears have no option but to rest up and conserve as much energy as possible until the winter months bring back their icy hunting substrate.

Climate change is warming the arctic environment at an unprecedented rate meaning that the period of ice-free months is
lengthening. This puts incredible strain on the metabolism of a polar bear that is waiting for a meal. Incredibly, they can go for months without eating a seal, but as the days grow warmer, the polar bears are increasingly affected. For example, research by Dr Ian Stirling and Dr Nick Lunn in Hudson Bay has shown that for every additional week that a polar bear is land locked (away from the hunting substrate of the ice) it is 10 kilograms (22 pounds) lighter! Let’s hope that today’s proposed listing of polar bears on the endangered species act will help secure a future for this species.

Excepts from an article written by Juliet Eilperin
Washington Post Staff Writer
Wednesday, December 27, 2006; A01

The Bush administration has proposed listing the polar bear as threatened under the Endangered Species Act, putting the U.S. government on record as saying that global warming could drive one of the world’s most recognizable animals out of existence. There are 20,000 to 25,000 polar bears worldwide, 4,700 of which live in Alaska and spend part of the year in Canada and Russia. The other countries with polar bears in their Arctic regions are Denmark (Greenland) and Norway.

Identifying polar bears as threatened with extinction could have an enormous political and practical impact. Because scientists have concluded that carbon dioxide from power-plant and vehicle emissions is helping drive climate change worldwide, putting polar bears on the endangered species list raises the legal question of whether the government would be required to compel U.S. industries to curb their carbon dioxide output.

This move stems from the fact that rising temperatures in the Arctic are shrinking the sea ice that polar bears need for hunting. Northern latitudes are warming twice as rapidly as the rest of the globe, according to a 2004 scientific assessment, and by the end of the century annual ocean temperatures in the Arctic may rise an additional 13 degrees Fahrenheit. As a result, researchers predict that summer sea ice, which polar bears use as a platform to hunt for ringed seals, will decline 50 to 100 percent.

The ice in Canada’s western Hudson Bay breaks up 2 1/2 weeks earlier than it did 30 years ago, giving polar bears there less time to hunt and build up fat reserves that sustain them for eight months before hunting resumes. As local polar bears have become thinner, female polar bears’ reproductive rates and cubs’ survival rates have fallen, spurring a 21 percent population drop from 1997 to 2004. Polar bears normally swim from one patch of sea ice to another to hunt for food, but they are not accustomed to going long distances. In September 2004, government scientists observed 55 polar bears swimming offshore in the Alaskan Beaufort Sea, an unprecedented spike, and four of those bears died. In a separate study that year, federal scientists identified three instances near the Beaufort Sea in which polar bears ate one another.

Footnote: Researchers disclosed today that a giant chunk of the Canadian Ice Shelf has recently fallen into the ocean. This shelf has shrunk by 90% since the 1930s. Food for thought!