Polar bear mother adopts cub in rarely documented case

Researchers tracking wild polar bears in northern Canada witnessed something exceedingly rare this fall: a mother bear adopting a cub that was not biologically her own.

The five-year-old mother bear and her 10- to 11-month-old cubs were observed and captured on camera during the annual polar bear migration along the Western Hudson Bay near Churchill, Manitoba, a town known for its polar bear population.

"It's unusual," Alyssa McCall, a scientist at Polar Bears International, said in a video. "We don't really know why it happens...but we know it doesn't happen often at all."

It's only the 13th known case of adoption out of the 4,600 bears studied for nearly five decades in the area.

The mother bear was first captured as she emerged from her maternity den this spring. At the time, she had one cub, which scientists tagged for study.

In the fall, she was seen again, but this time with two cubs - the original cub that had been tagged and another without a tag. Researchers aren't sure what happened to the new cub's biological mother, but they are trying to identify her with genetic samples.

"The bears need all the help they can get these days with climate change," Evan Richardson, a polar bear scientist with Environment and Climate Change Canada, said in a video statement. "If females have the opportunity to pick up another cub and care for it and successfully wean it, it's a good thing for bears in Churchill."

Polar bears in the wild only have a 50% chance of surviving into adulthood, but having a mother caring for them improves their odds.

The cubs appear to be healthy, researchers said, and they will likely stay with their mother until they are about two-and-a-half years old.

Next, the family is expected to head out to sea ice, where the cubs will learn from their mother how to hunt seals and survive on their own.

"It's just nice to know that the bears are looking out for each other," Richardson said.