Scientists have captured the extremely rare moments when polar bear cubs leave their snowy dens for the first time.
Filmed in Norway's Svalbard archipelago, the video shows a polar bear (Ursus maritimus) making her way across the frozen landscape of the Arctic island as her three cubs emerge one after another from a hole in the ice before sliding and falling across the frozen surface.
The picture shows one of 13 den sites on Svalbard that scientists have been monitoring for almost a decade to study polar bears' den-building behavior. This is extremely difficult because the female polar bears create their dens underground in hard-to-reach places.
In a paper published Thursday (Feb. 27) in The Journal of Wildlife Management, the researchers described new aspects of bear behavior inside dens.
“It's absolutely amazing to see polar bear cubs walking out into this vast white landscape that seems so hostile,” lead study author Louise Archer, a research fellow at Polar Bears International at the University of Toronto Scarborough, wrote in an email to Live Science.
“On Svalbard, polar bears make their dens on the sides of steep mountainous areas, and it’s hard to imagine how the cubs could find shelter in this harsh terrain,” Archer said. “Watching them slide, tumble and even climb on top of their mother was truly impressive.”
The new study provides a glimpse into one of the most vulnerable and critical periods in a polar bear's life, the researchers said in a statement.
Polar bears spend the winter in their dens. Pregnant females give birth in early January and nurse their cubs until spring, when the family emerges to slowly make their way to the sea ice. Newborn polar bears are hairless and weigh only 1 pound (0.5 kg). However, they quickly gain weight from their mother's nutritious milk, reaching 22 pounds (10 kg) by the time they emerge from their dens.
Polar bear dens are underground shelters where the bears spend the winter months.
The sustainability of a healthy polar bear population depends on the survival rate of cubs, which is only about 50%, according to the statement. Cubs can only survive if their dens remain intact throughout the winter and they are allowed to roam the surrounding area once they emerge. Human activity threatens both of these conditions.
“Polar bears are facing increasing challenges in reproducing due to climate change and will likely face additional challenges due to the increasing human presence in the Arctic,” Archer said in a statement.
To assess the impact of humans on polar bear reproduction, researchers need to better understand denning behavior and timing. Ten years ago, Archer and her colleagues fitted 13 female bears with GPS collars that recorded their location, body temperature, and activity levels. They used that data to pinpoint the locations of the bears’ dens before traveling to Svalbard and setting up camera traps outside the dens.
The study was the first to combine collar data with camera footage of polar bears. “Each den we looked at had its own unique story,” Archer said.
Sourse: www.livescience.com
