World

How to Catch a Polar Bear

From a helicopter, it can be hard to spot a polar bear against the frozen tundra. So when the polar bear biologist Jon Aars heads out for his annual research trips, he scans the landscape for flashes of movement or subtle variations in color — the slightly yellowish hue of the bears’ fur set off against the white snow.

“Also, very often, you see the footprints before you see the bear,” Dr. Aars said. “And the bear is usually where the footprints stop.”

Dr. Aars is one in a long line of polar bear researchers at the Norwegian Polar Institute, which has an outpost on Svalbard, an Arctic archipelago. Since 1987, the institute’s scientists have staged annual field trips into the icy wilderness to find and study Svalbard’s polar bears.

Over the decades, these research trips have shed light on the basic biology and ecology of the bears and, in recent years, helped scientists keep tabs on how the animals are coping with climate change. The rapid habitat changes are already affecting their behavior; with the sea ice retreating quickly, some of the bears now have to swim long distances in order to find places to den. But so far, the bears themselves still seem robust, Dr. Aars said.

If that begins to change, however, as researchers worry that it will, these annual field trips will help uncover problems early.

Here’s how scientists pull them off.

The trips often take place in the spring, when female bears are emerging from their dens with new cubs and the sea ice is solid enough to support what can be dangerous research. To maximize the area of study — and the odds of finding bears — the scientists traverse the archipelago by helicopter. “And, of course, if you have a helicopter and land on the ice and it’s thin, you risk having an accident with the helicopter,” Dr. Aars said.

Once airborne, the team, which typically includes two biologists, a veterinarian, a helicopter pilot and a mechanic, begins scanning the landscape for bears. When the researchers spot one, they take aim from the air with a tranquilizer dart. If they hit their mark, it typically takes just a few minutes before the bear is flat on the ice.

Then the researchers land and get to work. They wrap a piece of fabric — a scarf or blanket works well, Dr. Aars said — around the bear’s eyes to protect it from the sun’s fierce rays and set up equipment to monitor the bear’s heart rate, blood oxygen levels and body temperature.

They take a variety of physical measurements, tallying the animal’s length, girth and the size of its skull. They also examine its teeth, which can provide a good approximation of its age.

“When you’ve done that with hundreds of bears, you know, you start getting quite good at it,” Dr. Aars said. The female bears are also weighed, a delicate maneuver that requires hoisting them into the air on a stretcher attached to two spring scales. (The male bears are too heavy to weigh.)

Then they take blood, fur and fat samples, tucking the blood sample into a pocket so it does not freeze. “You just put it in your jacket, close to your body,” Dr. Aars said. Back in the lab, these samples will help the scientists answer all kinds of questions about the animal’s life: What is it eating? (Sometimes a bear is covered in blood when the researchers find it, a sign that it has just made a meal of a seal.) Does it have parasites? Has it been exposed to a lot of pollutants? They can also extract DNA from these samples to learn more about the genetics of the local polar bear population and sketch out ursine family trees.

Some of the female bears are given satellite collars, which track their location and activity. A “saltwater switch” on the collars activates when the bears drop into the water, allowing the researchers to calculate the amount of time the bears spend swimming.

Before finishing up, the researchers give the bears several identifying marks, adding an ear tag, implanting a microchip behind the ear and tattooing a number inside the lip. But they also add a more temporary mark, painting a number on each bear’s back. The number, which will disappear when the bear sheds its fur, prevents the scientists from capturing the same bear during the same field season. “We don’t want to hassle that bear twice,” Dr. Aars said.

The entire process takes about an hour for a single bear, longer for a female with cubs. When the researchers are finished, the veterinarian administers a drug to help reverse the sedative.

Sometimes the researchers wait for the bear to come to, just to make sure it is safely up and walking. They keep their distance, but for Dr. Aars, the work has become routine and he does not fear the bears as they awaken. “It’s not like the bear is saying ‘OK, I want to kill that guy,’” he said. “I think it’s more, like, seeing if it’s OK and probably having a bit of a headache and thinking about other things.”

And then they are back in the air, searching for their next bear.

Anna Filipova is a photojournalist based in the Arctic specializing in scientific topics who has covered the polar regions for 10 years.

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