Scientists studying polar bears during a recent tracking expedition in northeastern Manitoba were greeted with a most unexpected surprise.
A polar bear mother and her cub were walking near Churchill in mid-November when scientists spotted her with a second cub, which they were able to prove was not hers. This is only the 13th case of cub adoption within the western Hudson Bay subpopulation.
“When we confirmed this adoption, I had a lot of mixed emotions, but mostly good,” Alyssa McCall, director of conservation outreach and staff scientist at Polar Bears International, said in a video provided to the media.
“That’s another reason why this species is so incredible, why they’re so fascinating and interesting, and it gives you so much hope when you realize that polar bears are out there looking for each other.”
Dr. Evan Richardson, a polar bear research scientist at Environment and Climate Change Canada, was in the field back in March. His team of researchers found the mother in a denning area in Wapusk National Park, south of Churchill.
Two of the bears had GPS tracking collars when they were photographed in November, while the new one was not added. (Dave Sandford Photography)
At the time of that scene, the mother had only one child, Richardson said in a separate video provided to the media.
Fast forward to fall and Richardson is surprised to find that a family of two has become a family of three. Two of the bears had previously been tagged with GPS-tracking collars and one was not with the newly adopted cub.
“It’s not that frequent though because in our long-term study we have over 4,600 individual bears that we’ve known over the last 45 years, and literally hundreds and hundreds of litters. [of cubs]” he said of adoption.
Evan Richardson, a polar bear research scientist at Environment and Climate Change Canada, suspects that strong maternal instincts lead mother bears to adopt single cubs. (Presented by Samantha Bayard)
Researchers estimate the mother to be about five years old, while the cubs are both 10-11 months old.
Richardson doesn’t know for sure why the mother adopted the lone-roaming cub, but she has a hypothesis.
“We really think it’s just the reason [polar bears are] Very motherly charged and good mothers like that, and they can’t leave a crying baby in the tundra. So they picked it up and took it with them,” he said.
After being spotted with just one cub in March, Pola the polar bear was spotted with two in November, after adopting a lone wandering bear. (Dave Sandford Photography)
Polar bear cubs typically stay with their mothers for two to two and a half years.
“It doesn’t take long for a polar bear to learn how to be, but they learn a lot of lessons during that time. The survival rate for a cub to make it to adulthood is about 50 percent … but if we learn that a cub doesn’t have a mother, it’s almost no chance,” McCall said.
Adopted children now have a better chance of becoming adults, she said.
It’s unknown what happened to the adopted cub’s biological mother, but Richardson hopes that the genetic data his team can obtain from the cub sample will be able to provide some insight.
The National Weather Service partners with both Polar Bear International and the University of Alberta’s Polar Bear Science Program to collect data on bears through GPS collars. The movements of tagged bears can also be tracked online.
Female polar bears in the western Hudson Bay region have been collared for decades, though it only happens to about 10 of them annually, McCall said.
Less frequently polar bear cubs are adopted, rarer still are seeing them in person.
“Bears need all the help they can get these days with climate change,” Richardson said. “Females have the opportunity to raise another cub and care for it and successfully wean it. That’s a good thing for Churchill’s bears.”
