Polar bear mom and cub on sea ice, off the coast of Svalbard, Norway. (Credit:
Kt Miller / Polar Bears International)
In a nutshell
- Polar bear mothers carefully introduce their cubs to the outside world through a gradual process, with bears in Svalbard typically spending about 12 days at the den site after first breaking out before finally departing for sea ice.
- Weather plays a critical role in denning behavior. Warmer temperatures significantly increase the likelihood of both mothers and cubs venturing outside, suggesting cubs need time to acclimate to harsh Arctic conditions.
- Using both camera observations and satellite collar data, researchers developed models that can predict den breakout with 97% accuracy, providing valuable tools to protect these vulnerable animals from human disturbance at a critical life stage.
SVALBARD, Norway — In the frigid Arctic, polar bear mothers and their cubs emerge each spring from snow dens that have sheltered them through the bitter winter months. This critical transition, when fuzzy cubs first face the harsh Arctic environment, has been tough for scientists to study because of the challenge of accessing the remote locations of dens. But now, researchers have managed to capture this mysterious phase of polar bear family life by combining remote cameras with satellite tracking, giving us a rare window into how these iconic animals prepare their young for survival.
A new study published in the Journal of Wildlife Management shows us just how methodical polar bear mothers are about preparing their cubs for life on the sea ice. The research team, working in Svalbard, Norway, captured fascinating footage that reveals the careful, gradual process by which mothers introduce their cubs to the outside world.
“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,” says lead study author Dr. Louise Archer, Polar Bears International Postdoctoral Fellow at the University of Toronto Scarborough, in a statement. “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.”
With Arctic warming happening at up to four times the global average rate, understanding how polar bears reproduce and raise their young has never been more important. During denning, newborn cubs depend entirely on their mothers for warmth, protection, and nourishment. And with less than half of all cubs reaching adulthood, every insight into this vulnerable period counts for conservation efforts.
First Steps on Snow
Kt Miller / Polar Bears International)
The research team found that bears in Svalbard typically break out of their dens around March 9 and then hang around the denning area for about 12 days before finally heading out to the sea ice. During this period, mothers slowly introduce their cubs to the outside world, with weather playing a big role in when and how long they venture out.
It’s hard to imagine just how tiny and vulnerable polar bear cubs are at birth, weighing about the same as a grapefruit at just 600 grams. Born in the depths of winter inside snow dens, they rely on the relatively warmer den environment and their mother’s care for months. This protected space gives the tiny cubs time to develop until they’re ready to face the harsh Arctic environment.
Bear Monitoring Methods
This study combined time-lapse cameras at den sites with data from satellite collars worn by mother bears. By using both methods together, researchers could check how well the collar data (which is much more commonly collected in polar bear research) actually predicts real-world denning behaviors.
The team set up cameras at 13 suspected den sites over six years, with nine sites providing usable observations. These cameras caught mother bears introducing their cubs to the outside world. Interestingly, bears mostly came out during daylight hours, with only 6% of outings happening at night. Cubs showed up in 40% of these outings, suggesting mothers often scout the surroundings alone before bringing their vulnerable young outside.
The time spent outside varied dramatically, from less than a minute to almost eight hours, with an average of 27 minutes. Cubs rarely ventured out without mom and usually stayed right by her side, within about 2 meters of her in 78% of observations.
Family Matters
Some mothers actually moved their families to new dens during the study period. While researchers knew this could happen, the cameras captured this behavior in real-time, showing how bears adapt their denning strategy when needed.
As days passed after the initial breakout, both mothers and cubs gradually spent more time outside. Weather played a big role too. Warmer temperatures meant more time outdoors. For every 6.8°C increase in temperature, the chance of seeing a mother outside increased by 4.3%, while the chance of seeing cubs outside jumped by 7%.
This step-by-step introduction to the elements seems to serve a clear purpose: helping cubs get used to the harsh conditions they’ll face on the sea ice. Like a training program, this period allows cubs to build both physical resilience and behavioral skills before the family has to leave the safety of the den area to hunt seals.
Conservation Insights
“This study provides a rare glimpse into one of the most vulnerable and critical periods in a polar bear’s life,” says Dr. Megan Owen, Vice President of Wildlife Conservation Science at San Diego Zoo Wildlife Alliance. “Protecting denning habitats is essential for population health, and this study provides invaluable insights that will help guide protective management.”
When the researchers compared what they saw on camera with what the collar data showed, they found that collar information can predict den breakout quite accurately. By analyzing temperature and activity data from collars, they could predict den breakout with about 97% accuracy. However, catching those brief trips outside the den proved trickier, since collar data only comes in every two hours, compared to minute-by-minute camera observations.
“Studies including observational data at polar bear den sites have been few,” notes Dr. Jon Aars, Senior Researcher at the Norwegian Polar Institute. “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.”
Climate Change Concerns
Perhaps most concerning, the researchers noticed that bears left den sites earlier than was documented in previous Svalbard studies from the 1970s through 2010. While the sample size is too small to confirm a trend, this raises red flags about whether climate change might be forcing bears to alter their denning behavior in ways that could harm cub survival.
For wildlife managers and conservationists, the study offers practical tools to predict when bears are emerging from or leaving dens. This could help minimize human disturbance around den sites from activities like oil and gas exploration, snowmobile recreation, or industrial development. As human activity increases in the Arctic, keeping denning areas undisturbed becomes increasingly crucial.
Polar Bear Nurseries Today
Right now, newborn polar bear cubs are snuggled up in dens with their mothers across the Arctic. Born around New Year, these cubs start life blind, hairless, and tiny, weighing just half a kilogram. They grow rapidly on their mother’s incredibly rich milk (which is 31% fat), reaching about 10 kg (20 times their birth weight) by the time they emerge in spring. As we approach spring, many mothers and cubs are preparing to exit their dens and face the challenges of life on the sea ice.
Paper Summary
Methodology
The research team first used satellite collars on adult female polar bears to locate potential den sites in Svalbard, Norway, between 2016-2020 and in 2023. These collars transmitted location data, temperature readings, and activity measurements every two hours. Once they spotted likely den sites, they set up trail cameras to take photos every minute. To avoid disturbing the bears, researchers approached carefully on foot or ski after landing helicopters at least a kilometer away from the suspected den. Later, a technician analyzed up to 36,695 images per den site—tallying when bears emerged, how long they stayed outside, and how cubs and mothers interacted.
Results
The study revealed a remarkable variety in polar bear denning behavior. On average, bears first broke out of dens around March 9 and hung around the den site for about 12 days before leaving. During this period, the researchers documented 178 trips outside the den, ranging from just 2 emergences at one site to 68 at another. Bears mostly emerged during daylight, with cubs joining their mothers for 40% of these outings. Cubs almost never ventured outside alone (only 5% of emergences), and when they did, these solo adventures averaged just 5 minutes. In most cases (78%), cubs stayed practically glued to their mother’s side. The weather clearly influenced when bears came outside—warmer days meant more time outdoors. As more days passed since the initial den breakout, bears gradually spent longer periods outside, suggesting a deliberate process of acclimating cubs to their future environment.
Limitations
The study did have some limitations. The sample size was relatively small, with observations from just 9 den sites, all in one region of the Arctic. Cameras couldn’t always capture the entire denning area, and some sites had cameras that didn’t work at night. Plus, the mismatch between camera observations (typically one image per minute) and collar data (measurements every two hours) made it tricky to precisely correlate behaviors with collar readings.
Discussion and Takeaways
This research highlights just how important the post-emergence period is for cub development. The finding that bears might be leaving dens earlier than in previous decades points to possible changes in denning behavior that warrant close monitoring, especially given the rapid climate changes sweeping through the Arctic.
From a practical standpoint, the predictive models developed could help wildlife managers identify when bears are most sensitive to disturbance, enabling better protection of denning areas as industrial activities push further into the Arctic.
Funding and Disclosures
This research was funded by Mitacs through an Elevate Fellowship and by Polar Bears International, with additional support from WWF UK for fieldwork.
Publication Information
The study, titled “Monitoring phenology and behaviour of polar bears at den emergence using cameras and satellite telemetry,” was published in the Journal of Wildlife Management in 2025. The research brought together scientists from the University of Toronto Scarborough, Polar Bears International, Norwegian Polar Institute, San Diego Zoo Wildlife Alliance, and Carleton University.
