Research on polar bear health and abundance is critical to understanding how the animals are responding to declining sea ice in the warming Arctic.
But changes in the ice are also presenting challenges for researchers, who go out and collect information on the bears. So they’re trying to adapt.
For eight seasons now, wildlife biologist Todd Atwood has been part of a team that’s flown over the Beaufort Sea during the spring in a helicopter, looking for polar bears.
When they see one, and the conditions are right, they dart it with a sedative and land on the sea ice to collect information from the animal. They weigh the bear, age the bear, and collect a variety of biological samples.
Atwood works for the U.S. Geological Survey — one of the agencies that does research on polar bears in Alaska. Their research informs management decisions made by other government agencies.
The information they get through this research helps them come up with an estimate for the bear population. It also helps them determine if the animals are getting enough food, or if they have any other health issues.
But changes in the sea ice are affecting USGS scientists’ ability to do that kind of bear capture research.
“What we’re experiencing more recently is that the ice conditions are just terrible,” Atwood said.
For one, he said they’re increasingly encountering a lot of open water during their research season in March and April. That creates complications for flying, and they also worry about a sedated bear trying to escape to open water and drowning. Ideally, they try to find a large, stable pan of ice where they can spend about an hour getting data from the bear.
Of the ice they do find, a large part of it is now rubble ice — as Atwood put it: “Ice that looks like it just went through a blender.”
Ice is more likely to look like that if it’s first-year ice — meaning it melted completely in the summer and grew back over the course of one winter. First-year ice is increasingly common in the Arctic, where warming has lead to a decline in thicker, multi-year ice.
Atwood said that rubble ice makes it harder to see the bears from the helicopter because they kind of blend into it. It also limits where they can land.
These challenges mean they’re sampling fewer bears, and that will affect the conclusions they can draw from their research.
“There’s probably going to be a greater amount of uncertainty with some of the information that we’re able to provide, because it’s simply not going to be as precise as it used to be,” Atwood said.
USGS is already changing the way they collect data for population estimates. They’re relying more on making observations of bears from the air without landing, and on methods like biopsy darting — where they shoot a dart that collects a small tissue sample from the bear and doesn’t require them to sedate it. They can also collect DNA samples from tufts of hair they snag at hair snare stations.
And other researchers are looking into other methods.
“There’s some interesting work out there that suggests that collecting DNA from tracks left by polar bears in the snow might be a way to move forward,” Atwood said.
But Atwood said that when it comes to things like the bears’ weight, age and detailed health information, there’s still really no replacement for bear capture.