Grim news about polar bears struggling to survive in a changing world isn't new, but one small light flickers against the dark. There's a healthy population of the big bears living along the shore and islands of the Chukchi Sea.
There are 19 recognized polar bear subpopulations, but it's difficult to track the size of the groups due to their roaming lifestyle and remote locations. The International Union for Conservation of Nature, which maintains the Red List of Threatened Species, reports there are an estimated 26,000 to 31,000 polar bears in total, so the Chukchi Sea group's size puts it at the high end for the known subpopulation numbers.
The Chukchi Sea animals have healthy amounts of body fat and a good survival rate for cubs. A study from early 2018 tracked nine bears in the Beaufort Sea north of Alaska and found the majority of them lost body mass when they should have been packing on fat. The researchers traced the problem to the bears' struggles with hunting in a place where sea ice is disappearing.
A team led by researchers from US federal agencies and the University of Washington tracked bears in the Chukchi Sea between 2008 and 2016. The team sedated bears to collect biological samples, tagged them and attached GPS transmitters to some of the animals.
The collected data powered a new model designed to estimate population size, which can be challenging when you have large carnivores roaming over wide areas.
The loss of sea ice due to climate change is affecting another US polar bear group in the southern Beaufort Sea, adjacent to Alaska and Canada. University of Washington polar science researcher Eric Regehr says those bears are showing signs of stress as ice disappears and restricts their ability to hunt and breed.
While a healthy population of polar bears is positive news, it may not last.
"It doesn't mean that bears in the Chukchi Sea won't be affected by ice loss eventually," Regehr said. "Polar bears need ice to hunt seals, and the ice is projected to decline until the underlying problem of climate change is addressed."