WASHINGTON - The polar bear has become an icon of global warming vulnerability, but a new study has found an Arctic mammal that may be even more at risk to climate change: the narwhal.

The narwhal, a whale with a long spiral tusk that inspired the myth of the unicorn, edged out the polar bear for the ranking of most potentially vulnerable in a climate change risk analysis of Arctic marine mammals.

The study was published this week in the peer-reviewed journal Ecological Applications. Polar bears are considered marine mammals because they are dependent on the water and are included as a species in the US Marine Mammal Protection Act.

Scientists from three countries quantified the vulnerabilities that 11 year-round Arctic sea mammals have as the world warms. After the narwhal - which is also known as the "corpse whale" - and polar bear, the most at risk are the hooded seal, the bowhead whale, and the walrus.

"What we wanted to do was look at the whole picture, because there's been a lot of attention on polar bears," said study coauthor Ian Stirling, a polar bear and seal specialist for the Canadian government. "We're talking about a whole ecosystem. We're talking about several different species that use ice extensively and are very vulnerable."

The study looked at nine variables that help determine ability to withstand future climate changes. Those factors included population size, habitat uniqueness, diet diversity, and ability to cope with sea ice changes.

This doesn't mean the narwhal - with a current population of 50,000 to 80,000 - will die off first; polar bear counts are closer to 20,000, and they are directly harmed by melting ice, scientists said.

But it does mean the potential for harm is slightly greater for the less-studied narwhal, said study lead author Kristin Laidre, a research scientist at the University of Washington.

Stanford University biologist Terry Root, who wasn't part of the study, said the analysis reinforces her concern that the narwhal "is going to be one of the first to go extinct" from global warming despite their population size.

"There could a bazillion of them, but if the habitat or the things that they need are not going to be around, they're not going to make it," Root said.

Polar bears can adapt a bit to the changing Arctic climate, she said, and narwhals can't.

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