Grizzly mama of the Tetons sets out to break a record

Two-decade-old senescence study suggests that famous Grizzly 399 should again be able to bear cubs, even as she’s nearing the end of a normal grizzly lifespan.

By Mike Koshmrl WYOFILE

She’s 27 years old, reputed for being a stellar mother and knows her way around a crowd. 

If you live in Jackson Hole she might be your nosy neighbor. Regardless, her olfactory senses are terrific. 

Wyoming resident Grizzly 399 has lived a wild life that has garnered attention around the world. Like the best of us, she’s endured trials and tribulations and heartbreak. And her extraordinary life has inspired untold fans near and far. Hordes of the grizzly’s faithful fan club will surely be staked out in Grand Teton National Park in coming weeks awaiting her emergence from a months-long slumber. The big question is whether she’ll come out with her eighth litter and once again raise cubs. If that happens, the feat will undoubtedly add to Grizzly 399’s legend. 

At 27, she’d become the oldest monitored grizzly in the history of the Greater Yellowstone Ecosystem to bear a litter of youngsters. 

“We looked it up, and from what I’m finding the oldest known age of actual reproduction is 25,” Interagency Grizzly Bear Study Team leader Frank van Manen told WyoFile. “Of course, that might change this year if 399 comes out with cubs.” 

Will she? 

Although none of the Yellowstone region’s 1,100 or so grizzlies captured and collared since the 1970s was a reproducing sow quite so old, grizzly bear biology and research suggests that another stint at motherhood is a real possibility for Grizzly 399. Twenty years ago, former federal grizzly researcher Chuck Schwartz completed a study that queried grizzly populations around the world to ascertain the age grizzly bear reproduction declines and ceases — a phenomenon in mammals known as senescence.

Schwartz found that grizzly fertility shuts off around age 29. Fifteen bears that age or older were included in the dataset, and none of them was observed with first-year cubs. But 27 years old? Grizzlies that age are in steep reproductive decline, but can still pull off a litter. 

“We’re at the end of the curve where things change pretty rapidly,” van Manen said. “I wouldn’t give it a high probability [that Grizzly 399 will have cubs], more like 50/50.” 

Old moms’ club

Already, the matriarch sow bruin of the Tetons has surpassed most grizzly bear norms. For one, she’s still alive. Only 9% of female first-year cubs survive to reach age 27, van Manen said. 

But she’s got a ways to go outlive the oldest bears. There have been at least four females in the Yellowstone ecosystem that made it to age 30 or 31, according to the Interagency Grizzly Bear Study Team’s database. 

Although boars are generally shorter-lived, the oldest known bear in the Yellowstone region’s history, at 34, was male Grizzly 168, born in 1986 — the year Paul Simon’s Graceland came out and during an era when grizzlies were still concentrated in the Yellowstone region’s core. He died in 2020.

Grizzly 399 has also pushed the envelope on reproductive norms. 

In 2020, she lumbered into view seven weeks after the COVID-19 pandemic began changing life for humans. At her side were four little ones — a feat in itself. Four-cub litters comprise just 2% of all litters in the ecosystem. At that time, Grizzly 399, then 24, was the oldest sow being monitored with cubs in the Greater Yellowstone Ecosystem.

Since then, the old grizzly moms’ club has added to its ranks. Two 25-year-old females were documented with new cubs in 2022, van Manen said, tying the record — shared by four females — for the oldest age of reproduction documented in the Yellowstone region. 

One of them, Grizzly 416, is a Custer-Gallatin National Forest bear spotted with a couple of cubs. A Bridger-Teton National Forest denizen, Grizzly 499, joined her. 

It’s a sure bet that both those now 26-year-old bruins lead anonymous lives in the wild relative to their counterpart, who can command preposterously large crowds. Grizzly 399 has made a name for herself not just from roadside living in Grand Teton National Park, but also, infamously, from spending long stints in developed parts of Jackson Hole. She’s overcome incidents that frequently doom bears — like being purposefully fed — partly because state and federal wildlife managers have given her special treatment in recognition of her global fame. 

“She’s earned and deserved exception-status when it comes to the management,” said Cindy Campbell, a Red Top Meadows resident who’s among the legions dutifully tracking Grizzly 399’s every turn. “She’s touched hearts in every corner of the world, and that’s based on people that I’ve stood with on the side of the road. I’ve talked to people, and watched tears rolling down their faces when they’re minutes away from having to run to catch a plane to Portugal or Spain or China or Australia.” 

Notably, Grizzly 399’s progeny haven’t been extended the same special privileges. After two subadults from her 2020 quad litter dispersed to the Upper Green River Basin, a 2.5-year-old male, Grizzly 1057, was killed for frequenting residential areas. 

Will it happen? 

Grizzly 399 has a couple of things increasing the odds she’ll again reproduce. One, she was observed breeding last summer. 

“I saw her breeding with Bruno in June,” wildlife photographer Tom Mangelsen said.

That same male bear, Grizzly 679, was also seen mating with Grizzly 399 in June 2019, the year before she emerged with four cubs. 

Biologists say that Grizzly 399 also appears to have stayed in good shape.

“Our last confirmed sighting time was September 2022, and she was in good body condition,” said Justin Schwabedissen, the staff bear biologist for Grand Teton National Park. 

Van Manen agreed. Judging by the eye test, he said, Grizzly 399 is holding up well into her twilight years.

“Lactation takes a lot of energy,” van Manen said. “And just looking at the photos, she still seems to be in pretty good shape for having just raised a litter of four cubs.” 

Mangelsen’s description was blunter: She was straight “fat,” especially for that time of year. “I’ve never seen her that heavy before in September,” he said. 

The extra poundage boosts Grizzly 399’s odds of coming out with cubs, said Chris Servheen, a former U.S. Fish and Wildlife Service grizzly bear recovery coordinator. 

“They have to have a certain percentage of body fat in order to reproduce successfully,” he said. 

Oftentimes as older female grizzlies’ teeth wear down, their nutrition falls off and their body condition declines, Servheen said. Those old, lean sows may breed, but either the cubs won’t take or they’ll die in the den. Grizzly 399 is still looking pretty good, bucking the trend, he said. 

“She’s unusual that way, there’s no doubt about that,” Servheen said. “She’s right at the edge of her ability to keep reproducing. She’ll come out with cubs, or she won’t come out with cubs.” 

Campbell’s also not hazarding any guesses. She’s withholding her “wishes and opinions” and trying to relish the “mystery” of not knowing.

“Will she come out with cubs, will she come out alone, or will she come out at all?” Campbell asked. “To me, she reigns as the greatest grizzly bear to ever walk the Earth, whether or not she adds this next thing to her legend. In a lot of ways, what she does next doesn’t matter because of what she’s already achieved.”