Magnet and Anoki are polar bears at the Maryland Zoo in Baltimore. Magnet is on all fours on the left and Anoki is on the right. (Photos by Jeffrey F. Bill/THE MARYLAND ZOO IN BALTIMORE)

Polar bears are perfectly suited to life in the Arctic: Their hair blends in with the snow; their heavy, strongly curved claws allow them to climb over blocks of ice and snow and grip their prey securely; and the rough pads on their feet keep them from slipping.

The one thing they cannot survive is the loss of the ice, and the changes in worldwide climate threaten to melt the summer sea ice on which they hunt. Scientists say two-thirds of the world’s polar bears could disappear by about 2050.

So a group of American zoo and aquarium officials are asking the federal government to let them import orphaned bear cubs from Canada, so that some can be bred in captivity. Zoos have helped save endangered species before, such as the California condor and the Mexican wolf, which were bred in zoos and then set free into the wild.

“If you don’t build these insurance populations when you have the animals, then it’s too late,” said the Toledo (Ohio) Zoo’s mammals curator Randi Meyerson, chairman of the Association of Zoos and Aquariums’ polar bear species survival program. “We’re planning for something we hope we don’t need.”

Today 64 captive polar bears live in accredited institutions such as the Maryland Zoo in Baltimore, which has three. The National Zoo had 13 polar bears between 1959 and 1980, but it no longer has any and has no plans to try to get one because the bears are so expensive to care for.

Right now, polar bears cannot be imported into the United States for public display under federal law. Robert Gabel, with the U.S. Fish and Wildlife Service’s international affairs program, said that in order to bring bears into U.S. zoos, “we’d have to show that an import would either stabilize or increase the wild population of polar bears. It’s difficult to show how an import would accomplish that.”

Lily Peacock, a research biologist in the U.S. Geological Survey’s polar bear program, said the best way to help this threatened species is by cutting the heat-trapping gases that come from cars and trucks and burning coal to generate electricity.

“If the world cares about polar bears, reducing carbon concentrations in the atmosphere is the only way to preserve polar bears’ habitat,” she said.

Even backers of the zoo plan say that reducing carbon emissions is the top priority for saving polar bears.

Robert Buchanan, president of Polar Bears International, a group that works to help the animals, said displaying them in zoos could represent the best way to persuade the public to make such cuts.

“The only way at this time to save bears is to have people change their habits, and the way to do that is through zoos and aquariums,” he said. “Polar bears are just ambassadors for their friends in the Arctic.”