Studying polar bear dens in northern Alaska is no easy task: scientists worked in -30F temperatures to set up remote cameras.

© Geoff York/Polar Bears International

3/14/2017 9:34:54 AM

Snow, Blowing Snow, and Bitter Temperatures: Deploying Den Cameras in Alaska

By Geoff York, PBI Senior Director of Conservation and Staff Scientist 

Having spent 21 of my adult years in Alaska, flying North always feels a bit like coming home. This year marked the 16th year of our collaborative polar bear-maternal-den monitoring project with Dr. Tom Smith of Brigham Young University. What began as a short-term project to examine the potential for industrial activities to disturb denning polar bears has evolved into a non-invasive, long-term monitoring effort to catalog and understand den emergence behavior, log den exit and departure dates over time, and collect ongoing data on disturbances as situations allow.

Long view, unique challenges

The project is a classic example of “slow conservation” and the values of both persistence and patience, as annual sample sizes are typically small. In Alaska, polar bears den in snow caves excavated along coastal and river bluffs, or other features that collect drifting snow. Female bears do not generally return to the same location each year, as these features are transient, leaving us to rely on other methods to find dens. Historically, the USGS shared information with us on collared females denning within a reasonable distance of our base. But the agency’s research directives have shifted over time, and fewer females now have active tags. This year, no tagged bears chose dens along the central coast.

Another method of den location, though potentially less reliable, are the Forward-Looking Infrared (FLIR) surveys conducted by the oil industry ahead of winter operations in potential denning habitat. These surveys pinpoint “hotspots” or potential dens. If corroborated with visual evidence or other information (high historical use area, dog scent confirmation, etc.), these make good spots for setting up our den-monitoring camera systems.

Three sites this year

This year we were lucky, with three known polar bear den locations. One was adjacent to a steel causeway bridge actively used for vehicles and pipelines. This female was seen creating her den, and industry staff subsequently monitored the spot with infrared cameras showing a sustained “hotspot” through December and January after the den had drifted over. That location should provide interesting insights into denning behavior near industry. The other two dens were both “hotspots” from FLIR surveys that had either visual confirmation or were in a high probability location.

We were a little less lucky with the weather, arriving at the beginning of one blizzard, and departing just ahead of a second storm—giving us about 36 hours of weather that was “reasonable” enough to complete the mission. The day of our deployment began with a 20-mile round-trip snow machine ride out on the near-shore sea ice to one of our three den locations, with temperatures around -12 F and winds around 20 mph. We then had to trailer our equipment and drive 2.5 hours east to get closer to our final two dens—fortunately within five miles of one another. We finished the third installation in the dark, with northern lights dancing across the clear sky, no wind, and a temperature of -31F, which felt far better than the morning conditions.

The team will return in late April to recover the cameras and see what, if anything, they recorded. Look for an update this spring, and hopefully some unique footage of family groups at their dens. As this project has progressed we have learned more about den emergence behaviors, disturbance, and created a useful time series for den emergence in a rapidly changing Arctic.

Bitter cold is all part of a day's work when studying polar bear dens.

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