A Sense of Snow: Mapping Suitable Habitat for Polar Bear Dens

1/26/2012 5:31:02 PM

A Sense of Snow: Mapping Suitable Habitat for Polar Bear Dens

Polar bear mothers with cubs are snug in their snow dens at this time of year, completely hidden from view. No one wants to disturb a denning family—but how does anyone know if dens are there?

Scientists from three different organizations have teamed up to map snow characteristics of maternal polar bear denning sites along Alaska's Arctic coast to help refine den-detection techniques. The project is funded by two agencies: the U.S. Fish and Wildlife Service (USFWS) and the National Fish and Wildlife Foundation (NFWF). Biologists Craig Perham from the USFWS and Dick Shideler from the Alaska Department of Fish and Game (ADF & G) are the polar bear experts on the project.

Why is detecting polar bear dens important? Polar bears den on the Arctic coast of Alaska in some of the same locations where industrial activities, including oil and gas development, is occurring and where local residents venture. If a mother polar bear in a den is disturbed, it may affect the survival of newborn cubs by causing the mother to leave the den before the cubs are ready to survive in the harsh arctic environment. Disturbing unknown dens may also be dangerous to workers or residents in the area.

Three methods of den detection are currently being used by the two biologists. Two of the methods require the use of Forward-Looking Infrared (FLIR) sensors that can detect the mother polar bears under the snow by measuring the infrared radiation (heat) they give off in the den. One technique involves using the FLIR sensor mounted on a helicopter or plane. The other method uses hand-held FLIR systems on land. The team heads out into the field in the beginning of February using the FLIR system on land to detect dens. At this time the mother polar bear will still be in the den with her cubs, so careful attention will be paid to not disturb her, her cubs, and her den!

The third technique involves using trained scent dogs. The FLIR sensor cannot accurately detect dens when there is interference with wind, snow, blowing snow, or fog. These conditions can be quite common in arctic Alaska in the winter. However, dogs are less affected by adverse weather. The team of biologists will return in March using dogs to detect the bear dens. They've established careful techniques have been with the dogs to ensure the mother polar bear and cubs are not disturbed.   

In April, the research team will venture out to the dens once again after the mother polar bear has emerged from her den with her cubs. This will enable the third scientist in the group, snow scientist tand modeler Dr. Glen Liston of Interworks Consulting, to gather critical snow measurements on the vacant dens.

Dr. Liston will measure and record snow depth, snow-water equivalence (SWE), snow density, snow permeability to air flow, thermal insulation, and snow grain and crystal size of the snow in the areas around the dens. He will also record the location and topography of the dens. He will then take these data and combine them with a snow drift model to simulate snow drift location, size, and evolution. This blowing snow model mimics the physical interaction of snow, wind, topography, and land cover, to determine when, how far, and how much snow is transported and deposited in response to topographic variations. This tool will allow the scientists to map potential bear denning sites and the key factors that determine their denning locations. Therefore, in the future, industry and residents can know key areas that need to be avoided for the preservation and protection of the polar bears.

Accompanying the scientists is an educator, April Cheuvront from Avery Middle School, who, along with assisting with the snow measurements and field work, will post web and video blogs to websites of agencies involved with the project, documenting the science in action. She'll also generate lessons for students and classroom teachers to utilize on polar bear denning behavior.

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