Alaska and other plaintiffs that include hunters and the California Cattlemen's Association are appealing a federal court ruling last year that upheld the Interior Department's 2008 designation of the bears as threatened because their icy habitat is melting away.

Murray Feldman, a lawyer for Alaska and other appellants, told the U.S. Court of Appeals for the District of Columbia that the government had failed to show how the big white bears likely would be nearing extinction at the middle of this century.

The department's decision on the Arctic mammals was "arbitrary and capricious" since it was based on flawed models, Feldman said in oral arguments before a three-judge panel.

Katherine Hazard, a lawyer for the department's Fish and Wildlife Service, said that the designation relied on decades of research and long-term trends underpinned it.

"The agency needs to make a determination based on the best available science, which the agency did here," she said.

A designation that a species is threatens means that it is likely to become endangered within the foreseeable future in all or a significant part of its range.

Bruce Woods, a Fish and Wildlife spokesman, said the listing drew more attention to the bears' plight and also triggered funding for programs including patrols to limit contact with humans and a recovery plan for the bears.

Arctic sea ice shrank to a record low of 1.32 million square miles (3.41 million square km) by mid-September, the National Oceanic and Atmospheric Agency reported this month.

A decision by the appeals court is not expected for months.

Alaska and oil companies have argued that Endangered Species Act protections for polar bears diminish opportunities for Alaska energy development.

The state has said in its appeals court filing that bears have survived previous warming periods and most populations have grown or remained stable despite shrinkage of ice.

The case is Safari Club International et al v. Ken Salazar et al and Center for Biological Diversity et al, No. 11-5219.

(Reporting by Ian Simpson; Editing by Paul Simao)

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