Maternal Den Studies

Maternal Dens
Den Acoustics
FLIR Den-finding Techniques

A PBI research team spends six weeks each spring in northern Alaska studying polar bear mothers and cubs as they emerge from their dens. Join them in the field through our Scientists & Explorers blog.

Maternal Dens
As the Arctic melts, more polar bear mothers are choosing to den on land. In late fall, pregnant females tunnel into coastal snow banks to claw out dens where they give birth to their cubs. Snow soon drifts across the entry holes, completely hiding the dens from view.

Unfortunately, many of the best coastal denning spots buzz with industrial activity. Yet little is known about polar bear denning behavior.

A PBI team led by Dr. Tom Smith of Brigham Young University, who serves on our Scientific Advisory Council, spends weeks in the bitter cold of Alaska's North Slope every year trying to find out:

  • When do polar bears typically emerge from their dens with cubs?
  • How long do families hang around at the den site before heading to the sea ice to hunt seals?
  • How sensitive to disturbances are denning polar bears?

This research give us a broader picture of denning behavior—increasingly important information as oil activity spikes and the sea ice shrinks.

Den Acoustics
PBI scientists recently completed a pioneering study of the polar bear's hearing range.

Now that we know how sensitive polar bear hearing is, Project Leader Megan Owen of the San Diego Zoo's Institute for Conservation Research and a member of our Advisory Council, is testing how noise from vehicles and machinery travels through the snow—where female bears dig their maternity dens.

To do this, Owen and her team created artificial dens on the North Slope of Alaska and equipped with them with recording devices. They're now documenting which industrial sounds penetrate the snow dens and from what distances.

The knowledge gained will help authorities set guidelines for Industry working in sensitive areas where female polar bears den with their cubs.

FLIR Den-finding Techniques
Scientists use Forward-Looking InfraRed (FLIR) technology to  detect polar bear dens under the snow. PBI researchers are refining techniques to improve the accuracy of this amazing tool, which detects a polar bear's body heat as scientists fly overhead.

Under the direction of Dr. Tom Smith, our researchers constructed a series of artificial dens on Alaska's North Slope. They equipped them with heaters that emit roughly the same amount of heat as a denning polar bear family. Scientists then fly overhead with FLIRs to discover which methods work best for finding the dens.

It's important to locate and map polar bear den sites each fall so that industry working in the area can avoid disturbing mothers with cubs.

Our thanks to the St. Louis Zoo and Utah's Hogle Zoo for helping to fund these studies.