Radar technology to detect polar bear dens | Polarjournal
A polar bear with her two young cubs. Females generally spend six months in a den with their young, still unable to survive the elements outside. Months of great vulnerability for the mother and her babies. Image: Michael Wenger

Scientists have tested new radar technologies for locating dens, aiming to increase protection for mother polar bears and their cubs.

While the use of radar and satellites is nothing new in tracking and monitoring polar bears, this latest technological advance focuses in particular on locating dens that are buried in the snow and almost invisible.

The result of a collaboration between Simon Fraser University and Brigham Young University (BYU), along with Polar Bears International, the pilot study was conducted in Churchill (Manitoba) in Canada in October 2021. The location is widely known for its gatherings of polar bears waiting there for the sea ice to form.

The researchers tested an imaging system based on synthetic aperture radar (SAR) with promising results showing a detection rate of 66%. This is twenty percent better than the system currently used and which relies on FLIR infrared aerial detection and a detection rate of 45%. In addition, the SAR system works regardless of temperature and weather conditions, a sine qua non condition in the Arctic environment.

SAR antennas are attached above the skids of a helicopter. The sensors are then connected to the radar electronics in the cabin. Image: Brent George et al.

Unlike FLIR, which uses thermal technology to track bears by their body heat, SAR uses microwave signals capable of penetrating ice and snow. “The system can ‘see’ both the top snow surface, the den roof surface and inside the den cavity”, says Bernhard Rabus, professor of engineering sciences and one of the authors of the article. This definitely is an advantage which allows not only to distinguish a bear from a rock but above all to avoid false positives or negatives often found in FLIR technology.

According to the authors, who published their results on October 12 in the journal URSUS, “SAR may be a promising candidate to become an effective tool for polar bear detection, particularly when coupled with other sensors such as FLIR.”

Churchill was chosen by researchers because of the many known bear locations in a small area. At the time of the experiment (October 2021), the bears were all on the surface and mobile, which allowed them to be distinguished from the ground, particularly from trucks or buggies. The ground team then took the GPS coordinates of bear’s location and transmitted them to the team responsible for planning the helicopter flight paths. A system that allowed testing whether animals could be identified on SAR images.

The birth period is a delicate time for polar bears because it is a time of great vulnerability. She gives birth to one to three cubs, which are blind, no fat reservers and poorly insulating thin fur. Thus, the female will nurse them with particularly rich milk for several months, usually from December to April. During this time, the bear will remain in her den, literally buried under ice and snow, renedering her basically undetectable.

That poses a real problem in regions where human activities, especially industrial activities, are developing, increasing the chances of disturbing bears and their cubs. Thus, there is an urgent need to develop and enhance technologies that enable increased detection of dens.

Mirjana Binggeli, PolarJournal

Link to the study : Brent George, Terri Bateman, Mckay Formica, Wyatt Gronnemose, Nicholas Hilke, Usman Iqbal, B.J. Kirschoffer, Bernhard Rabus, Tom Smith, Jeff Stacey, Lucas Stock, Evan Zaugg, David Long. On evaluating the efficacy of air-borne synthetic aperture radar for detecting polar bears: A pilot study. Ursus, 2023; 2023 (34e6) DOI: 10.2192/URSUS-D-22-00018

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