Narwhal More at Risk From Warming Than Polar Bear?

April 29, 2008

A porpoise with a long, spiraled tusk that inspired the myth of the unicorn ranks higher than the polar bear on a new list of marine mammals most at risk due to Arctic warming.

That's because the narwhal, also known as the corpse whale, may be slightly more sensitive to habitat changes.

All Arctic marine mammals are at risk from warming, which is melting sea ice and shifting the distribution and abundance of prey, the report authors say.

Polar bears rely on sea ice to hunt, and at least one study has suggested that two-thirds of the bears could disappear by 2050 if climate change continues.

But the bears live all over the circumpolar Arctic, and their habitat is unlikely to melt all at once, giving them time to potentially shift their range.

The narwhal, by contrast, mostly sticks to waters between Canada and Greenland (see map), said study leader Kristin Laidre, an oceanographer at the University of Washington in Seattle.

The species' restricted geographic distribution, combined with specific migration routes and a specialist diet, make it just barely more at risk based on the criteria set out for the new analysis, Laidre said.

Her team's report, which ranked the vulnerability of 11 Arctic and subarctic marine mammals, was published last week in the journal Ecological Applications.

Faithful Narwhals

Narwhals spend a few months each summer in ice-free, shallow bays in the high Arctic. In the fall they migrate to deep, mostly ice-covered habitats where they feed.

"They have very specific migration routes and what we call site fidelity," Laidre said.

The animals never vary from their routes and return to the same summer and wintering grounds year after year.

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