Maternal Den Studies
Q&A: Svalbard Maternal Den Study
Photo copyright Kt Miller/Polar Bears International.
Polar Bears International’s maternal den study in Svalbard takes place each spring in partnership with the Norwegian Polar Institute and San Diego Zoo Global. The study involves placing remote cameras at den sites to record the activity of emerging polar bear moms and cubs.
In this Q&A with BJ Kirschhoffer, our director of field operations, we find out more about the project and why it matters.
Q: First, could you tell us a little about polar bear moms and cubs in their dens?
A: It’s actually quite remarkable. Female polar bears dig dens in snowbanks in the fall and give birth to their cubs in late December or early January—a time of year when temperatures outside can plunge to -50. At birth, the cubs are blind, covered with light fur, and weigh roughly one pound. The cubs are quite vulnerable at that stage. They rely on their mother’s care and the shelter of the den for their survival. The family remains in the den for three or four months, hidden from view, until the cubs are strong enough to follow their mom to the sea ice in spring.
Q: This research project focuses on the time period when the family breaks free of the snow den in spring. What do you hope to learn?
A: Sea ice loss due to climate change is impacting denning polar bears across the Arctic. In Svalbard, Norway—where sea ice loss is most dramatic—we are observing fewer maternal dens, as well moms and cubs in poorer condition when they emerge from their dens. This issue could worsen as an ever-warming Arctic opens new opportunities for tourism and development in the North.
Unfortunately, very little is known about polar bear denning behavior—and even less is known about the impacts of human disturbance on denning bears. This project will help answer those questions, so wildlife managers can better protect moms and cubs.
Q: What does the study involve?
A: We monitor dens with remote camera systems that have been refined over years of field testing. The cameras are built to withstand harsh Arctic conditions while reducing disturbance to denning families. We set up the cameras while the bears are snug in their dens, hidden under the snow—and then we depart, leaving the cameras to do the work.
When the family emerges from their snow den in spring, the cameras capture their activity. The footage allows us to assess the body condition of the moms and cubs. It also provides information on how families spend their time and how long they remain at the den site before heading to the sea ice to hunt seals.
It’s a very non-invasive study. We return to retrieve the footage and the equipment after the bears have left their den.
Q: When did you start the project?
A: We started the Svalbard study in 2015, building on earlier den study work that we did in Alaska as part of a project led by Dr. Tom Smith of Brigham Young University. That work was motivated by the fact that more and more industrial activity was moving into the region, yet little was known about denning behavior and what impact it might have.
Since that early work in Alaska, our systems have changed greatly. The cameras are so small and energy-efficient now that our packages have shrunk from 300 pounds (and quite bulky!) to the size of a carry-on suitcase weighing about 35 pounds.
Q: How many dens do you typically monitor?
A: It varies from year to year, but generally three to five dens. Many of the known den locations are on steep mountain slopes. They are in such remote locations that the only way to reach them is by helicopter, landing a safe although in one low-snow year we mostly hiked in, pulling the sled with our equipment.
Q: Are there any differences between the study in Svalbard and the previous project in Alaska?
A: There are quite a few differences, starting with terrain. Along the North Slope of Alaska, the landscape is mostly flat and featureless—almost like being on the moon! Also, there is quite a bit of oil and gas activity in the region. Svalbard, on the other hand, is characterized by steep mountain slopes, glaciers, crevasses, and dramatic fjords. No industrial activity takes place in the denning areas, but snowmobilers and skiers visit the more accessible slopes. So, the types of human activity in the two regions are quite different, as are the denning conditions for the bears.
Q: Why does it take so long to learn anything from studies like these?
A: When studying behavior like denning, long-term studies are important because we are looking at an animal with a long lifespan. If we look at just one, two, or five years of a bear’s life, we get a very incomplete picture. Polar bears could have low—or high—birth rates for several years in a row, then completely reverse for the following 10 years. Polar bears require what we call a longitudinal study lest we make premature conclusions about them. The same holds true for monitoring the family’s body condition, the number of cubs, and so on. You need a long data set.
Q: Is there anything else you’d like to add about the project?
A: In Svalbard, we are constantly surprised about where the bears den. To anyone who knows snowy mountains and the danger of steep slopes and avalanches, it’s amazing to see how frequently the bears perch themselves in fairly precarious places. For a cub coming out of the den for the first time, he’d better know how to use his brakes! It’s remarkable how polar bear moms have figured out how to den on these steep slopes and then lead their young cubs to the sea ice. The more I learn about polar bears, the more amazed I am.
Special thanks to Seneca Park Zoo, Berlin Zoo, Ouwehand Zoo, Tierpark Berlin, and Saint Louis Zoo for helping to underwrite this project. We’re also grateful to our research partners, San Diego Zoo Global and the Norwegian Polar Institute, for their support and participation.