Polar bear cubs filmed emerging from their dens for first time

By Stephen Beech

Polar bear cubs have been filmed emerging from their dens for the first time.

The extremely rare footage was captured by remote cameras deployed in the Arctic mountains for nearly a decade.

The pictures of polar bear moms and cubs emerging from their dens in Svalbard, Norway, shine valuable light on the reproduction process of the threatened species, say scientists.

The footage came from a study conducted by an international team including researchers from conservation group Polar Bears International, the San Diego Zoo Wildlife Alliance, the Norwegian Polar Institute, and the University of Toronto.

Polar bears usually give birth around New Year, at which point the cubs are blind, hairless, and weigh just half a kilo (1.1 lb).

They emerge from their birthing dens between February and April of each year.

The research, published on International Polar Bear Day in the Journal of Wildlife Management, marks the first combination of satellite tracking collars with remote camera traps to answer questions about polar bear denning.

Polar Bears International created International Polar Bear Day [Feb 27] to mark the time when moms and cubs are about to exit their dens.

The research team explained that it has been notoriously difficult to study before now as polar bear mothers build their dens under snow in remote areas.

For the study, female polar bears were fitted with GPS satellite collars that recorded their location, temperature, and activity.

Researchers used the collar data to locate dens, and they traveled through Svalbard’s mountains to deploy time-lapse camera traps at 13 den sites.

The team 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.

The researchers were able to obtain fresh insights into the timing of den emergence and post-emergence behavior of young polar bears.

They explained that cub survival is key to the survival of the species, and the denning period is the most "vulnerable" period of their life as less than 50% of cubs may make it to adulthood.

As industry expands in the Arctic, conservationists say the study highlights the importance of undisturbed denning areas to protect polar bear populations.

Study lead author Dr. Louise Archer, Polar Bears International postdoctoral fellow at the University of Toronto, said: "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.

“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.”

The research team found that polar bear families emerged around March 9th in Svalbard, and appeared to abandon the den earlier than previously recorded.

They say that changing the timing of denning could potentially jeopardize cub survival as they have less time to develop before venturing further afield to the sea ice.

The team also observed that, in some cases, bears emerged from the den for less than a minute before going back inside, while other emergencies lasted several hours.

The camera footage indicated that polar bears remain near their dens for an average stay of 12 days, but that varied massively between polar bear families, ranging from two to 31 days.

Some mothers left their original dens and were observed moving their family to a new den.

The footage also confirmed that cubs rely heavily on their mothers, rarely venturing outside the den alone.

Cubs were seen without their mothers only 5% of the time. In Svalbard, cubs depend on their mom for up to 2.5 years.

The team says the study highlights the need for monitoring and protection of denning areas to ensure the survival of future generations because cubs rely on the den emergence period to acclimatize to the external environment and to prepare for life outside the den.

Dr. Megan Owen, Vice President of Wildlife Conservation Science at San Diego Zoo Wildlife Alliance, said: “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.

“By combining innovative technology with long-term research, we’re gaining a deeper understanding of the challenges polar bear mums 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.”

Dr. Jon Aars, Senior Researcher at the Norwegian Polar Institute, said: “Studies including observational data at polar bear den sites have been few, and this study contributes significantly to our knowledge about denning ecology.

“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."

He added: "This is of great value as a lot of data from collared females that have been in a maternity den is available.”