Finding Polar Bears Dens Under the Snow

2/4/2012 9:30:50 PM

Finding Polar Bears Dens Under the Snow

How can you detect a white mama bear, with small white cubs, covered with white snow in a white, vast landscape—in below freezing temperatures, howling winds, and blowing snow?

By jumping into a tracked Arctic vehicle called a Tucker and heading out onto the sea ice near Howe Island off the coast of Prudhoe Bay! That was our mission on our first evening looking for polar bear dens in Prudhoe Bay.

April Cheuvront off Prudhoe Bay

Craig Perham, a U.S. Fish and Wildlife Service biologist based in Anchorage, Alaska, uses a Forward Looking Infrared detection system (FLIR) to look for dens along the island's coast. This involves having the Tucker vehicle  go at a speed of two-three miles-per-hour while Craig aims the camera system out of the window, pointed towards snowdrifts. He watches for small, subtle differences in heat to appear on his camera-like screen. Dick Shideler of the Alaska Department of Fish and Game assists the process by using a range finder to ensure that the vehicle keeps a safe distance of 40-60 meters away from possible denning sites.

The FLIR system can detect heat differences as small as 0.1 degree Celsius! Wow! A mother polar bear and cubs are expected to emit an average heat equivalent to a 120-watt light bulb, which may register as a 1-1.4 degree C difference. It sounds so easy and one just expects to see a den at any moment! However, many factors can interfere with the readings, such as blowing snow and bare rocks or vegetation.

Den example

After screening for four hours over seven miles of coastline, we were able to establish one possible hot spot for a den but no definitive denning site at this point. In March, this possible den site will also be surveyed with dogs to see if any bear signals are found.

For now, the team is happy with our sighting of polar bear tracks in the snow around the island, which means that a mother bear with two-year-old cubs was cruising the area within the last 48 hours. Tomorrow will bring more searching for dens on another island!

Bear tracks in the snow

Photos by April Cheuvront & Dr. Glen Liston.

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