When life gives you lemons… study ice instead.
GPS tracking collars placed on polar bears typically provide researchers with data on the bears’ location and movement to provide insight into, well, polar bears. Sometimes collars fall off or are removed prematurely and left behind.
Rather than bemoaning the lost data opportunity when that happens, researchers in Canada studied the data transmitted from 20 high-accuracy GPS telemetry collars to track sea ice drift instead. Since the collars were not able to track the movement of the wayward polar bears, the team studied the detailed movement, speed and other characteristics of sea ice flow, which is often a “prohibitively expensive or practically unfeasible” task, according to their report.
Ice drift is considered in models for geographic, environmental, climate change, and ecological research according to the study. Because of the remote, vast and changing nature of the Arctic, sea ice studies often rely on computer models and remotely sensed data rather than on-the-ground (or on-the-ice) information gathering.
Computer models by their nature rely on inputs and assumptions and inherently have certain limitations. The researchers compared the collar data to a widely used sea ice drift dataset produced by the National Snow and Ice Data Center (NSIDC). The findings show the traditional model tended to underestimate the magnitude and speed of drifts and well as the horizontal and vertical components of drift.
Ron R. Togunov of the University of British Columbia, and team members Natasha J. Klappstein, Nicholas J. Lunn, Andrew E. Derocher, and Marie Auger-Méthé published their report, “Opportunistic evaluation of modelled sea ice drift using passively
drifting telemetry collars in Hudson Bay, Canada” in The Cryosphere in June 2020. They’ve also made the position data of their drifting collars available here.
The team had fitted polar bears (Ursus maritimus) in western Hudson Bay with satellite-linked GPS collars in the August and September months between 2004 to 2015. To get close enough to the bears, the animals were given a rapid-acting anesthesia, Telazol, in accordance with government standards of care, according to the researchers.
According to the website Polar Bears International, only female polar bears are collared since male polar bears’ necks are too thick and collars would slip off their heads. Younger bears grow rapidly in size so are able to be collared. Collars for polar bears are made of flexible, synthetic material that can withstand water and ice. The devices need to stay flexible in cold temperatures but be strong enough to withstand Arctic marine conditions.
The study’s researchers note that sometimes collars may slip off a bear, be removed prematurely or the bear may die while its collar continues to transmit location data.
Polar Bear International notes that some collars are designed to detach remotely and fall off a bear before the battery is drained. Wear and tear or salt water corrosion on the release mechanism may also cause the collar to fall off.
According to Polar Bear International’s website, if a collar battery was able to provide 12 months of operation “scientists are pretty happy.”