Scientists capture heartwarming and rare moment as polar bear mom adopts a cub that isn’t her own

When female polar bear X33991 emerged from her maternal den in northeastern Manitoba this spring, she was accompanied by just one cub. Months later, researchers spotted her again, and this time, she wasn’t alone with just one young bear. X33991 was seen moving across the landscape with two cubs in tow, prompting scientists to take a closer look.



Their conclusion: a rare and confirmed case of polar bear cub adoption.



Researchers say this marks the 13th documented instance of cub adoption within the western Hudson Bay subpopulation, one of the most closely studied polar bear groups in the world. Around 4,600 bears have been tracked in this region over the past 45 years.



X33991 was first observed in March leaving the denning area of Wapusk National Park, where scientists fitted her cub with an ear tag. When the bear was seen again in mid-November near Churchill, Manitoba, she had two cubs with her — one tagged, one untagged. The trio was captured on video near Hudson Bay, where hundreds of polar bears gather each fall while waiting for sea ice to reform.



Further investigation confirmed that X33991 had adopted the second cub. Both cubs are estimated to be 10 to 11 months old. The mother, fitted with a GPS tracking collar, is around five years old. Polar bear cubs typically remain with their mothers for two to three years before heading onto the sea ice to hunt on their own.

What happened to the cub’s biological mother?

Scientists don’t yet know what became of the adopted cub’s biological mother. Genetic samples taken from the cub may provide answers. Researchers say the DNA could match a female bear already known to scientists, helping determine whether she is still alive.



It’s also possible the cub was never orphaned at all. Polar bear mothers have previously been known to switch litters or temporarily take on extra cubs.



“There must be some sort of confusion going on,” says Evan Richardson, a scientist with Canada’s environment and climate change department, in a video statement provided to media. “But we really think it’s just because they’re so maternally charged and such good mothers and they can’t leave a cub crying on the tundra, so they pick them up and take them along with them.”




Globally, polar bear cub survival rates hover around 50 percent during their first year. But for orphaned cubs, the outlook is far worse.



“If a cub becomes orphaned for some reason, it has almost no chance,” says Alysa McCall, director of conservation outreach and a staff scientist with Polar Bears International, in a social media video.



“When we got confirmation that this was an adoption, I had a lot of mixed feelings, but mostly good,” she adds in a separate video statement provided to media. “It gives you a lot of hope when you realize that polar bears maybe are looking out for each other out there.”



Despite the hopeful signs, experts urge caution. Of the 13 known adoption cases in the western Hudson Bay subpopulation over the past five decades, only three adopted cubs have survived, according to The Guardian, citing reporting by Leyland Cecco.

Life on thinning ice

For now, GPS tracking data suggests the small family is doing well, moving across the sea ice in Hudson Bay as expected.



Polar bears depend heavily on sea ice to hunt seals, their primary food source. But as global temperatures rise, sea ice is forming later in the fall and melting earlier in the spring, forcing bears to spend longer periods on land.



The Arctic Ocean, home to all 20 known polar bear subpopulations, is warming roughly four times faster than the rest of the planet. Scientists estimate that about 26,000 polar bears remain in the wild, spread across regions including Canada, Alaska, Russia, Greenland and Norway.



In Norway, only one cub adoption has ever been documented, Jon Aars, an ecologist at the Norwegian Polar Institute who was not involved in the Canadian case, told The Washington Post’s Victoria Bisset. Still, researchers believe the behavior may be more common than records suggest.



“The bears need all the help they can get these days with climate change,” Richardson says in the 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.”