New Study: Polar Bear Cubs Emerging From Maternal Dens

Svalbard, Norway – February 27, 2025 – Researchers from Polar Bears International, San Diego Zoo Wildlife Alliance, the Norwegian Polar Institute, and the University of Toronto Scarborough reveal the first detailed look at polar bear cubs emerging from their dens, captured through nearly a decade of remote camera footage in Svalbard, Norway. 

This research, published today 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, which is notoriously difficult to study as polar bear moms build their dens under the snow in remote areas. The researchers present new insights into the timing of den emergence and post-emergence behaviors alongside new tools to monitor polar bear dens across the Arctic. 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,” says Dr. Louise Archer, lead author and Polar Bears International Postdoctoral Fellow at the University of Toronto Scarborough, adding, “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.” 

Key Findings:

• Altered Den Emergence Periods: The researchers report that 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. 

• Variable Den Presence: 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. 

• Den Switching: Some moms switched dens – they left their original dens and were observed moving their family to a new den.

• Maternal Dependence: 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, cubs depend on their mom for up to 2.5 years. 

• Circumpolar Conservation Implications: The study underscores 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.

• Introducing Wildlife Management Tools: The researchers combined collar data and timelapse cameras both to uncover insights about denning behavior and to create a data-driven tool to understand polar bear denning across the Arctic. This research provides the foundation for improved wildlife management, enabling the reduction of potential clashes between polar bear denning areas and human activity.

“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,” says 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,” says Dr. Jon Aars, Senior Researcher at the Norwegian Polar Institute, adding, “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.”

Methodology: Female polar bears were fitted with GPS satellite collars that recorded their location, temperature, and activity. 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 (2016 - 2020 and 2023). The study 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. 

What are polar bear cubs doing right now? Newborn polar bear cubs are currently snuggled in dens with their mothers across the Arctic. Polar bears typically give birth around New Year, at which point the cubs are blind, hairless, and just a 1/2 kg (or 1 lb, roughly the size of a stick of butter). They grow quickly, nursing on their mom’s milk which is 31% fat, reaching around 10kg – up to 20 times their birth weight – by the time they leave the den in spring. Polar bears emerge from their birthing dens between February and April of each year, with the timing varying depending on where they live– Polar Bears International created International Polar Bear Day (February 27th) to honor the time when moms and cubs are about to exit their dens. The duration of the denning period, timing of den emergence, and time spent at the den site after emergence all contribute to the survival of polar bear cubs. 

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About Polar Bears International

Polar Bears International’s mission is to conserve polar bears and the sea ice they depend on. The organization works to inspire people to care about the Arctic, the threats to its future, and the connection between this remote region and our global climate. Polar Bears International is the only nonprofit organization dedicated solely to wild polar bears and Arctic sea ice, and the staff includes scientists who study wild polar bears. The organization is a recognized leader in polar bear conservation. For more information, visit www.polarbearsinternational.org.

Media Contacts

Annie Edwards, for Polar Bears International 
annie@fabricmedia.net
+44 0 7307 139782

About The Norwegian Polar Institute

The Norwegian Polar Institute (NPI) provides scientific knowledge about the Arctic and the Antarctic and advice to the Norwegian authorities. NPI has the main responsibility for polar bear research in Svalbard, and has conducted research on polar bears since the 1960s. The main office is in Tromsø, Norway, but NPI also has offices in Longyearbyen and Ny Ålesund, Svalbard.

About San Diego Zoo Wildlife Alliance

San Diego Zoo Wildlife Alliance, a nonprofit conservation leader, inspires passion for nature and collaboration for a healthier world. The Alliance supports innovative conservation science through global partnerships and groundbreaking efforts at the world-famous San Diego Zoo and San Diego Zoo Safari Park, both leading zoological institutions and accredited botanical gardens. Through wildlife care expertise, cutting-edge science and continued collaboration, more than 44 endangered species have been reintroduced to native habitats. The Alliance reaches over 1 billion people annually through its two conservation parks and media channels in 170 countries, including San Diego Zoo Wildlife Explorers television, available in children’s hospitals across 14 countries. Wildlife Allies—members, donors and guests—make success possible.

About the University of Toronto Scarborough

Founded in 1964, the University of Toronto Scarborough is an anchor institution in the eastern Greater Toronto Area. Situated in one of Toronto’s most diverse and multicultural neighbourhoods, the campus fosters a vibrant culture of community engagement. Here, students cross academic and geographic boundaries in their pursuit of knowledge. Experiential learning is one of the hallmarks of our approach to education. We are proud to be part of the University of Toronto, recognized as the most sustainable university in the world and Canada’s top university. U of T has a long history of challenging the impossible and transforming society through the ingenuity and resolve of its faculty, students, alumni and supporters. We are part of one of the top research-intensive universities, bringing together top minds from every conceivable background and discipline to collaborate on the world’s most pressing challenges. Together, we continue to defy gravity by taking on what might seem unattainable today and generating the ideas and talent needed to build a more equitable, sustainable and prosperous future.