A grizzly in Yellowstone National Park might have set a regional record with a litter of five cubs, and some of those cubs may have been adopted.
Yellowstone tour guide Andrea Baratte on Wednesday shared with Cowboy State Daily a video he’d taken that morning of a grizzly with five cubs in tow.
Some bear experts told Cowboy State Daily that they’d never heard of a grizzly litter of that size in the area.
But in the wild, female bears will occasionally adopt and raise cubs that aren’t their own, which might account for such an unusually large Yellowstone grizzly family.
New Record?
A grizzly litter of five could very well could be a first for Yellowstone Park, and perhaps for the entire region.
“Five cubs in a litter are the most we have ever observed in the park, at least from 1959 to present — the period of the park's history we have good records for,” National Park Service spokeswoman Linda Veress told Cowboy State Daily.
Federal bear researcher Frank van Manen agreed that it’s likely a first in Yellowstone country.
“A litter of five cubs would be a first for grizzly bears in the Greater Yellowstone Ecosystem,” said van Manen, the supervisory research biologist for the U.S. Geological Survey’s Interagency Grizzly Bear Study Team.
In Alaska, there have been rare instances of grizzlies with five cubs, and even one with a litter of six, he said.
Wyoming Game and Fish Large Carnivore Specialist Dan Thompson also said that a litter of five grizzly cubs is truly impressive.
“I have seen a few four-cub litters in my career, but have never witnessed five. That sure is a lot of mouths to feed!” he stated in an email to Cowboy State Daily.
399’s Quadruplets Were All Hers
Wyoming’s most famous bear, Grizzly 399, emerged from her den in Grand Teton National Park in the spring of 2020 with a litter of four cubs, all thought to be hers by birth.
She raised them to their independence over the next two years, a time period central to the story of the recently-released documentary film “399: Queen of the Tetons.”
Grizzly 399’s current lone cub, commonly called Spirit, was born last year and has been frequently described as “gigantic.” And many attribute his impressive size to the fact that he doesn’t have any siblings to compete with.
Adoptive Bear Moms
Although there’s no way of knowing for sure yet, there’s a good chance that the Yellowstone grizzly mom of five adopted some of those cubs, van Manen said.
“One important consideration is that this litter may be the result of an adoption event because there were recent observations in the area of two females with cubs in close proximity of one another; previous occurrences of adoptions have been documented through genetic analysis,” he said.
Veress also said it remains unknown if the five cubs are true quintuplets by birth, or if that particular grizzly mama has a blended family.
“We do not know if all five cubs are hers, or if she may have adopted some of them,” Veress said.
If all five cubs are to survive until independence, typically age 2 for grizzlies, they’re up against steep odds, Veress added.
“In Yellowstone, the average litter size for grizzly bears is two cubs. Approximately 49% of cubs survive their first year,” she said.
That One Time A Grizzly Maybe Had Sextuplets
Quadruplet grizzly cubs like 399’s 2020 litter are rare, but not unheard of, van Manen said.
“Litters of four are rare but have been documented in at least eight different North American brown bear populations,” he said. “The Interagency Grizzly Bear Study Team has documented 11 litters of four cubs so far in the Greater Yellowstone Ecosystem.”
Anything above four cubs is extremely rare, van Manen said.
There’s also been one documented grizzly litter of six, but it wasn’t determined whether those cubs were a true set of sextuplets from the same birth mother.
“Litters of five are very uncommon in North America, but a few have been documented in Alaska. There is one record of a litter of six cubs in Alaska, but in that instance adoption could not be ruled out,” van Manen said.
Contact Mark Heinz at mark@cowboystatedail.com
Mark Heinz can be reached at mark@cowboystatedaily.com.
