Published today on International Polar Bear Day, new research marks the first combination of satellite tracking collars with remote camera traps to answer questions about polar bear (Ursus maritimus) denning, which is notoriously difficult to study as polar bear moms build their dens under the snow in remote areas.
Archer et al. reveal the first detailed look at polar bear cubs emerging from their dens. Image credit: Jon Aars / Norwegian Polar Institute.
Cub survival underpins species survival, and the denning period is the most vulnerable period of their life — less than 50% of cubs may make it to adulthood.
As industry expands in the Arctic, the study highlights the importance of undisturbed denning areas to protect polar bear populations.
“Polar bear mothers are having increasing difficulties reproducing due to climate-driven changes, and are likely to face further challenges with the expansion of the human footprint in the Arctic,” said Dr. Louise Archer, a researcher at the University of Toronto Scarborough.
“We’re excited to introduce new tools to monitor bears during this vulnerable time and to gain insight into their behavior across the Arctic, so that we can work to protect cubs and therefore the species.”
“Every den we monitored had its own story, every data point adds to our understanding of this crucial time and supports more effective conservation strategies.”
In their research, the authors monitored behavior of polar bears at den emergence in Svalbard, Norway.
Female polar bears were fitted with GPS satellite collars that recorded their location, temperature, and activity.
The researchers used these collar data to locate dens, and they traveled through Svalbard’s mountains to deploy timelapse camera traps at thirteen den sites over six years.
They found that camera traps provided fine-scale insights into maternal den behavior, while satellite collars are accurate and useful for monitoring bears over longer periods and in more remote areas.
Families emerged around March 9th in Svalbard, and appeared to abandon the den earlier than previously recorded in this population, with further monitoring required to establish whether this is a continuing trend.
Changing the timing of denning could potentially jeopardize cub survival as cubs have less time to develop before venturing further afield to the sea ice.
In some cases, bears emerged from the den for less than a minute before going back inside, while other emergences lasted several hours.
In terms of departing the den for good, the camera footage indicated that polar bears remain near their dens for an average stay of 12 days.
However, this varied greatly between polar bear families, ranging from 2 to 31 days.
Some moms switched dens — they left their original dens and were observed moving their family to a new den.
Cubs rely heavily on their mothers, rarely venturing outside the den alone. Cubs were seen without their moms only 5% of the time. In Svalbard, they depend on their mom for up to 2.5 years.
“This study provides a rare glimpse into one of the most vulnerable and critical periods in a polar bear’s life, offering insights that can help guide our collective conservation efforts,” said Dr. Megan Owen, Vice President of Wildlife Conservation Science at San Diego Zoo Wildlife Alliance.
“By combining innovative technology with long-term research, we’re gaining a deeper understanding of the challenges polar bear moms and cubs face in a rapidly changing Arctic.”
“Protecting denning habitats is essential for population health, and this study provides invaluable insights that will help guide protective management.”
“Studies including observational data at polar bear den sites have been few, and this study thus contributes significantly to our knowledge about denning ecology,” said Dr. Jon Aars, senior researcher at the Norwegian Polar Institute.
“Further, as the data from satellite radio collars were available for all the mothers, the observational data made it possible to tell how changes in activity and temperature recorded correspond with behavior.”
“This is of great value as a lot of data from collared females that have been in a maternity den is available.”
The study appears in the Journal of Wildlife Management.
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Louise C. Archer et al. Monitoring phenology and behavior of polar bears at den emergence using cameras and satellite telemetry. Journal of Wildlife Management, published online February 26, 2025; doi: 10.1002/jwmg.22725
