The threatened polar bear has become an icon for the potentially devastating effects of global warming. The animal depends on sea ice for its survival, and this ice is disappearing, no more so than in the Chukchi Sea — the remote stretch of ocean between Alaska and Russia.
U.S. biologists don't know much about the bears that live there, but they're trying to learn as much about the population as they can before their habitat melts away.
One hundred miles from land in the middle of the Chukchi Sea, round sheets of ice are broken up occasionally by a strip of inky blue water. To the human eye, it looks like a starkly barren landscape. But to a polar bear, it is a rich environment to which they are brilliantly adapted.
Eric Regehr, a biologist with the U.S. Fish and Wildlife Service, crouches down next to a sedated bear to examine one of its paws.
"You can see they have very sharp hooked claws like that for gripping on the ice and for gripping onto their seal prey," he says. "And you can feel how sharp these are."
This is a relatively small bear, and Regehr guesses he is about four years old — an adolescent.
"He has pretty big feet, like a puppy — big feet they have to grow into," he says.
While the bear sleeps, Regehr learns as much as he can about him — he takes blood, hair and fat samples, and he measures his length and weight. This bear is about 7 feet tip to tail and weighs in at close to 700 pounds — tiny compared to many full grown males. And Regehr has weighed a lot of huge bears this year — one even set a springtime record in Alaska, at 1,266 pounds.
"He was borderline obese," Regehr says. "He was a very fat bear for this time of the year. If you looked at him in profile, his belly almost scraped the ground, so he was a really fat good-looking bear, and in general most of the bears have appeared quite healthy."
The bears may be in good shape now, but the ice that allows them to gorge on blubbery seals is retreating at an alarming rate. Regehr says the future for Alaska's polar bears is grim, and he's already seeing one potentially troubling sign — very few females with cubs.
The bear Regehr is studying today is the 39th he has examined this season. His last step is to draw that number with fur dye on the polar bear's back. Each bear is also outfitted with ear tags and a lip tattoo that will allow Regehr to track their progress if he captures them again next year.
It will take several seasons of study to understand how the polar bears in this region are reacting to their changing environment.
Rosa Meehan, who heads the marine mammal division of the U.S. Fish and Wildlife Service in Anchorage, says the knowledge will make it easier to help the bears through difficult times ahead.
"The thing that I focus on is the need to give bears as much of a break as we can during this impending climate crisis, in the hopes that we can get our hands on climate change and address it in a realistic fashion," Meehan says. "If we can do that, then there's hope that the environment will stabilize and come back, and we'll still have bears there to come back and repopulate."
Meehan says one idea is to set up land refuges where polar bears may be able to eek out a meager existence for a while. But, she says, that's a frightening possibility to consider for a species meant to live on the sea.