Scientists tracking free-roaming polar bears in northern Canada witnessed something exceedingly rare this autumn: a female bear taking in a cub that was not biologically her own.
The half-decade-old mother and her 10- to 11-month-old cubs were spotted and filmed during the annual polar bear migration along the Hudson Bay's western shore near the Manitoba town of Churchill, an area renowned for its concentration of Arctic bears.
"It's unusual," stated a researcher with a polar bear conservation group. "We don't really know why it occurs...but we know it is a rare event at all."
It's only the thirteenth documented instance of fostering out of nearly five thousand bears studied for nearly five decades in that region.
The mother bear was first captured as she came out from her birthing den this spring. Initially, she had a single offspring, which scientists marked for research.
In the autumn, she was spotted once more, but this time with a pair of cubs - the original cub and another that was untagged. Scientists aren't sure what became of the new cub's birth mother, but they are attempting to identify her using genetic samples.
"These animals need every advantage they can get in the current era with a warming climate," commented a wildlife biologist. "If females have the opportunity to pick up an additional youngster and care for it and successfully wean it, it's a positive development for the bears."
Polar bears in the natural world only have a fifty-fifty survival rate of surviving into maturity, but having a mother caring for them boosts their chances.
The young bears appear to be healthy, according to experts, and they will likely remain with their adoptive mother until they are about two-and-a-half years old.
Next, the family is anticipated to venture out to sea ice, where the cubs will learn from their mother bear how to hunt seals and live on their own.
"It is heartening to know that the animals are caring for each other," concluded the researcher.