Polar bear in northern Manitoba adopts second cub in the wild in rare case

Alex Karpa reports researchers document one of the rarest polar bear behaviours ever recorded.

Researchers tracking polar bears in northern Manitoba have witnessed something that is extremely rare: a wild mother bear has adopted a cub that was not biologically her own.

This rare behaviour was observed and captured on camera during the annual polar bear migration along western Hudson Bay in Churchill.

It’s just the 13th known case of adoption, out of the 4,600 bears studied for more than 45 years in the region.

“When we got confirmation that this was an adoption, I had a lot of mixed feelings, but mostly good,” said Alysa McCall, the director of conservation outreach and a staff scientist with Polar Bears International.

“It’s just another reason why this species is so incredible, why they’re so fascinating and interesting, and it gives you a lot of hope when you realize that polar bears may be looking out for each other.”

“It’s also balanced by some concern, like what happened to the biological mom?” she added.

How do researchers know the cub is adopted?

The mother, who is known and is being tracked as bear ‘X33991’, was encountered by researchers from Environment and Climate Change Canada earlier this spring.

As she came out of her maternity den, the mother only had one cub, which was tagged.

When she was seen again in the fall, she had two cubs, one with a tag and one without.

“Obviously that cub got picked up somewhere along the way and is an indication that she adopted this particular cub,” said Evan Richardson, a polar bear research scientist with Environment and Climate Change Canada. “To encounter this in the field is very unique.”

“Most of the other cases of cub adoption have been determined using genetics, so we can assign paternity [and] maternity to polar bears in our study population, but to actually see it in the field was a first for me,” he said.

The polar bear tracker shows the mom and her cubs on the move, starting in early November south of Churchill, moving her way north along the western shores of the Hudson Bay in southern Nunavut.

The latest data from Dec. 17 shows the mom on the Hudson Bay ice, in what would appear to be her hunting for food.

Researchers estimate the mother is around five years old and the cubs are between 10 and 11 months.

Polar bears in the wild only have a 50 per cent chance of surviving into adulthood, but having a mother provides a much better chance. Cubs typically stay with their mom between two and two-and-a-half years.

Richardson says there is evidence of adopted cubs surviving to adulthood in the western Hudson Bay area, with three out of 13 adoption cases having shown this survival.

But how does a polar bear cub get adopted? Well, Richardson says there are many different scenarios.

“Their own mother didn’t survive, so they were orphaned,” he said. “We don’t have any information to support that for this particular bear yet, but we are looking at the genetics to see if its mom is still around.”

He said bears in large groups could also get confused and separated, so these cubs may end up following another female and sticking with her.

“We don’t know why it happens, but it happens in a number of different mammal species. Over 60 species of mammals are known to adopt offspring, and it really appears that these females are maternally charged to take care of these young cubs, and are willing to take on an extra offspring,” he said.

Mother bear wearing GPS tracker

The mother is wearing a GPS tracking collar as part of a research program by Environment and Climate Change Canada and the University of Alberta.

The collars help scientists track polar bear movements and habitat use, survival, denning areas, and time spent on sea ice for feeding, which provides critical information for better protecting the species in a changing climate.

McCall with Polar Bears International says this is one of the only ways researchers can study what polar bears are doing throughout the year.

“They are out on the sea hunting seals, they are super dangerous and difficult to access, but with GPS technology, we can better understand where the polar bears are moving, when, why, what types of ice they need, and how this may be shifting over time,” she said.

“With this sort of technology, we can better understand polar bears and can better protect them, so she is part of this critical research that is helping us learn a lot more about what her species needs,” McCall said.

Researchers will continue to monitor the family and will remove the collar in 2027 to download the data and better understand the mom’s movements over the course of the last two years.

Is this rare behaviour related to climate change?

Researchers, like Richardson, do not believe that cub adoption is related to climate change. It is more of a behavioural link to how maternally charged these female polar bears are to take care of offspring.

“Because we have such a long-term study, we have documented cub adoption from the early 1980s, when climate change really wasn’t an influence on this particular group of bears, all the way to present,” he said. “We haven’t seen any changes in the frequency of cub adoption in this population, so there is really no linkages to climate change as of yet.”

“It’s relatively unique and nature can be cruel and harsh, but to see that the bears are looking out for each other, it’s really a feel-good story and puts a smile on your face,” he said.