It’s grizzly mating season in Yellowstone National Park, and a pair of bears — a male called Quill and a female called Snow — didn’t let a crowd of onlookers disrupt their courtship.
The amorous grizzly scene near Yellowstone Lake caused a bear jam for at least a quarter mile in each direction for days this past week.
Despite the bears looking sweet and cuddly together at times, their mating habits shouldn’t be mistaken for what humans might call falling in love, a bear biologist said.
Grizzlies don’t go for long-term pair relationships, and a female can mate with multiple males during the spring.
Raspberry’s Daughter
Snow and her sister Jam are some of the park’s best-known bears. They’re the offspring of Raspberry, Yellowstone’s favorite bear. She has been missing for about a year and is presumed dead.
Grizzly watcher and photographer Rick Partlow told Cowboy State Daily that he was a huge fan of Raspberry, and noted that Quill tried courting both Snow and Jam last spring.
This past week, Quill and Snow put on a show, clearly visible in a meadow near the roadside.
At times, Quill would approach Snow, who seemed interested. Then, she’d apparently change her mind and run off a short distance.
Other times, she’d growl at Quill when he got too close. But then things would become more agreeable as the two bears cuddled in the grass.
Partlow said he watched the pair for quite a while on Wednesday. He thinks they mated successfully, but that act apparently took place “deep in the brush,” he said.
The bears were still together early Friday, he said.
“I drove by this morning and they were headed up over the hill,” he said.
‘1,000 Cameras’
Wildlife photographer Dominic Weskamp told Cowboy State Daily that he watched Snow and Quill for about three hours. He finally had to leave because it was getting cold and his camera batteries were running low.
“I hated to leave. It’s hard to walk away from two grizzlies,” Weskamp said. “They were in a little meadow that has a sort of dirt wall around it. It’s like they were in an arena."
He observed plenty of affectionate interaction between the bears, but no actual mating.
“With 1,000 cameras on you, that would be a little intimidating, even for an animal,” he said.
Multiple Mates
Snow and Quill’s antics are right on time, grizzly researcher Lana Ciarniello of British Columbia, Canada, told Cowboy State Daily.
Bears that are “eligible for breeding” usually do so through the end of May, she said.
“With grizzly bears, the male will try to sequester her away,” to avoid being interrupted by rival males, Ciarniello said.
It’s difficult to say how long a breeding female will stay with a particular male, she added.
However, there’s a good chance that Quill wasn’t Snow’s first mate this spring, and he might not be the last.
Females can pair up with several males during a single mating season, she said.
And when a female grizzly’s egg is fertilized by a male’s sperm, it doesn’t immediately attach to the uterine wall and start to gestate. Instead, it will “float around” in the uterus, she said.
So, it’s possible for a female grizzly to carry fertilized eggs from different males. And if a female shows up with multiple cubs the next spring, it’s possible they were all sired by different males, Ciarniello said.
Delayed Gestation
After a female grizzly carrying fertilized eggs goes into her winter den, “her body decides” whether it has enough fat reserves to gestate a cub, or cubs.
That determines whether no eggs, one egg, or two or more eggs attach to the uterine wall and start to gestate.
Researchers recently determined that in the Yellowstone ecosystem, gestation is timed for the cubs to be born in January. That means cubs will be about 5 months old when they emerge from the dens with their mothers in May.
Even outside of the usual mating season, a male grizzly might try killing a female’s cubs, in order to put her back into estrus, or heat.
It’s thought that male grizzlies won’t attack the cubs of a female they’ve mated with, Ciarniello said.
“They might not recognize the cubs, but they might recognize the female,” she said.
That’s another reason why it’s advantageous for female grizzlies to mate with multiple males, she said.
Mark Heinz can be reached at mark@cowboystatedaily.com.
