How to Count Polar Bears

From a New York Times Magazine story by Malia Wollan headlined “How to Count Polar Bears”:

“Look for a small, slightly yellow-colored speck on the white sea ice,” says Kristin Laidre, principal scientist at the University of Washington’s Polar Science Center. Get an aerial vantage, preferably from a helicopter flying 500 feet above the ice. Your eyes will need practice, but even Laidre, who has been on more than 40 Greenland expeditions, can still mistake an iceberg lump for a bear. If you spot fresh tracks, follow them until you find an animal. Sometimes you won’t; a single bear can roam hundreds of miles. “We’ll fly for a couple of hours and not find a bear,” Laidre says.

Polar bears evolved to roam the ice, subsisting on seals; on land, they can’t hunt and mostly go without. But sea ice is shrinking, making life more difficult for bears and counting them more dangerous for scientists. Your census will never capture every individual. Instead, sample and extrapolate. The most common method for polar bears is “capture-mark-recapture,” whereby researchers nab bears, mark them, let them go and then later nab more, using the ratio of marked to unmarked animals to make population estimates. “You can’t squirt a polar bear with a blotch of paint,” Laidre says.

Once you’ve located a bear, shoot it with a tranquilizer, land the helicopter on the ice and mark the animal with both a permanent white plastic ear tag and a small tattoo inside the upper lip. “Work as fast as you can,” Laidre says. If the bear begins to move, don’t fret — full wakefulness takes a while.

Use genetic marking if you’re in an area where the sea ice can’t support the helicopter, or if you prefer not to handle the bears. Shoot the animal’s rump with a biopsy dart that extracts a bit of hair and skin before falling to the ground. Jump from the hovering helicopter onto the ice to collect the dart and use the bear’s unique DNA code as a mark. Ideally, counting efforts won’t get bogged down in matters of state. Polar bears live in Greenland, Canada, Russia, the United States and Svalbard, Norway, and are known to regularly cross international borders. “Polar-bear research should transcend politics,” Laidre says.


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