© Daniel J. Cox/Arctic Documentary Project
6/25/2018 4:58:24 PM
Svalbard Den Study
Our director of field operations, BJ Kirschhoffer, recently returned from Norway, where he took part in a Quark expedition in the Svalbard archipelago. While there, he stopped by the Norwegian Polar Institute field office in Longyearbyen to retrieve footage from this year’s Polar Bear Maternal Den Study, a joint project involving Polar Bears International, the San Diego Zoo Institute for Conservation Research, and the Norwegian Polar Institute.
We caught up with BJ to talk about this year’s field work, the third year of the study.
Q: You deploy remote cameras in late February, before polar bear families emerge from the dens. What is the goal of the study?
A: We hope to understand more about polar bear denning behavior in a changing climate. Our cameras record when families emerge from the dens, how long they remain at the den site before heading for the sea ice, and the health and condition of the moms and cubs.
Monitoring this is especially important in a warming Arctic. We already know that some polar bears are thinner due to sea ice loss, which reduces access to their seal prey. Polar bear mothers rely on stored body fat to withstand the months-long fast required to successfully den. Without adequate fat reserves, some mothers may choose to leave their dens before the cubs are ready. The longer the family can stay in the den, the better equipped the cubs are to begin life on the sea ice. So, an important part of the data we’re collecting is to assess the behavior and relative size of the cubs when they emerge.
We’re also really excited about the ability to calibrate the behaviors recorded by the camera with the data gathered by the accelerometer and thermometer on the collar. The original intent of the thermometer was to let the team know when the mother bear was inside the den and when she was out. But there’s a fair amount of noise and that hasn’t been as easy as we thought.
The accelerometers measure movements. We have a lot of data from them that we don’t know how to interpret. Now we can look at the footage and the accelerometer data and say, “Oh, mom’s digging at the den site. Oh, interesting, mom’s rolling now.” We can go back to that same timer on the collar and say, that’s what rolling looks like. It will help us understand real world behavior.
Q: How many cameras did you set out this year?
A: The Norwegian Polar Institute pinpointed the location of five dens by tracking satellite-collared females. Of the five den sites, one was an easy snow machine ride from Longyearbyen; the others required helicopter trips. In the end, we were able to deploy cameras at two dens, one reached by snow machine, the other by helicopter. The weather was too poor to reach the remaining three, which were at high elevations and wrapped in clouds. As our pilot put it, “We think we can get you there, but we’re not sure we can pick you up.” We decided it wasn’t worth the risk.
Q: What is the process for retrieving the cameras? How do you know when the moms and cubs have let the dens?
A: The Norwegian Polar Institute monitors GPS data from the satellite collars; once the collars show that the bears have moved from the area, they know it’s safe to pick the cameras up. Three members from their team—Dr. Jon Aars, Rupert Krapp, and Christian Zoelly—retrieved the equipment in April.
The den accessible by snow machine turned out to be a difficult trip. The route took them over glacial moraines, which have rocks and mud under the snow. When they set out the weather was pretty good, but it was rainy and foggy by the time they started the trek back. On the way home, the snow started melting quickly and they were hitting dark, muddy moraine stuff, struggling to pull big wooden sleighs piled with equipment. But they made it.
Q: What happens after you retrieve the cameras?
A: The Norwegian Polar Institute has a beautiful workshop and storage facility in Longyearbyen. When they return from the field, the team unloads and checks all the equipment; they also document what needs to be repaired and catalog everything. It’s such a huge asset to have that facility. In Alaska, we usually have to evaluate our gear outside in the cold.
Rupert transferred the data from the camera onto hard drives, and I collected all that when I was Svalbard. I’m in the process of transferring it onto our hard drives here and will then send a copy to Dr. Jon Aars at the Norwegian Polar Institute and to Dr. Megan Owen at the San Diego Zoo Institute for Conservation Research for data analysis.
Q: What have you learned so far?
A: Studies like this are long-term, but we’ve started to hone in on how many cubs are at the den site when they emerge versus how many are with their mom a month later. We also look at how much the cubs weigh compared to mom, and the height of each cub relative to other cubs in litter and to mom. We check how coordinated are they, what differences there, the timing of emergence, how long they hang around the den, and their general behavior. This project has a potential to answer a lot of basic questions in a rapidly changing ecosystem.
Special thanks to Utah’s Hogle Zoo, Yorkshire Wildlife Park, Ouwehands Zoo, Berlin Zoo, St. Louis Zoo, and Chicago Zoological Society for helping to underwrite this study.