The first mortality investigation occurred last spring in Idaho, but by the first week of September, the description appeared with increasing regularity in the database federal biologists use to track grizzly bear deaths in the Yellowstone region.
By mid-October, the words “UNDER INVESTIGATION” had been entered 16 times, nine of them in relation to dead Wyoming grizzly bears.
Details will be held tight for months until investigations are complete, but those two words usually mean that a grizzly bear was shot and killed with a claim of self-defense. Typically, somebody is out hunting something else, like elk, and there’s an altercation: On average, hunter gunfire ends the lives of 10 grizzlies a year in the Greater Yellowstone Ecosystem.
The handful more under-investigation deaths that have already been logged with weeks to go before grizzlies den up for the winter is one sign that 2024 is shaping up to be an exceptionally deadly year for grizzly bears in the Yellowstone ecosystem, potentially even the deadliest to date — an unwelcome benchmark.
“We’re not necessarily shooting for the record,” said Dan Thompson, who leads large carnivore management for the Wyoming Game and Fish Department.
Dan Thompson, large carnivore supervisor for the Wyoming Game and Fish Department, in May 2023. (Mike Koshmrl/WyoFile)
As of Tuesday, the database tracking grizzly bear mortalities reached 65 deaths this year. That trails only 2018, a conflict-filled year that ended with 69 mortalities for the large carnivores, which remain federally protected by the Endangered Species Act after decades of population growth and range expansion. The figure swings significantly — mortality can be related to grizzly bear food sources, like berry crops. Two years ago, 54 grizzly deaths were logged. The 2023 toll was 47.
While there’s no one reason for the higher-than-usual death toll for Ursus arctos horribilis, the leading cause this calendar year has been depredation on livestock — an often unshakable habit that becomes a death sentence for bears.
“Livestock-related removals basically doubles the average from over that decade [2014-23],” Interagency Grizzly Bear Study Team leader Frank van Manen said. “It’s about 14 a year, and currently we’re at 28.”
Killing grizzly bears to stem livestock conflict in Wyoming started up on private land in April far outside of the Greater Yellowstone Ecosystem near the Bighorns. It didn’t let up until Oct. 3, when an adult male met his end south of Cody.
Although livestock conflict and suspected self-defense shootings are the leading causes, there’s a good-sized list explaining what’s been killing the Yellowstone Ecosystem’s grizzly bears, which last numbered an estimated 1,030.
Total abundance at den emergence for grizzly bears in the Greater Yellowstone Ecosystem, based on 1983–2023 data. (Global Ecology and Conservation)
A sow and her two cubs in August died in the cement-sided Heart Mountain Canal — a long-running cause of grizzly deaths. There was an unusually high number of cropland damage-related deaths: Seven mortalities fell into that bucket.
“There’s been unique situations this year,” Thompson said. “We had a couple of bears in Yellowstone that died of electrocution — scavenging cow elk that were electrocuted.”
In another situation, he said, a grizzly bear in the Beartooths took a liking to preying on domestic dogs.
“When we went in to investigate, it was specifically seeking out dogs to kill them and eat them,” Thompson said. “It went after our guys’ dogs and went after other people’s dogs — just very aggressive behavior.”
In addition to the near-record number of grizzly bear mortalities, the region is also touching on its record for conflicts, Thompson said.
The number of grizzly conflicts in Wyoming could potentially exceed the all-time record in 2024. This graph shows data from a recent decade. (Interagency Grizzly Bear Study Team)
The conflicts and grizzly bear deaths have not occurred uniformly across the landscape.
On the northern end of the biologically isolated ecosystem in Montana, the 10 grizzlies documented to have died makes for a pretty normal year, said Jedediah Smith, a grizzly bear specialist for Montana Fish, Wildlife and Parks.
“Morality varies,” Smith said. “We’re usually in, around or under 10 [deaths]. But sometimes we’ll go as high as 15 to 19.”
A significant portion of the grizzly mortality has also occurred on the fringes of the ecosystem. Grizzly bear numbers are only monitored in what’s called the “demographic monitoring area,” a 19,279-square-mile zone dominated by federal land. This year, 24 of the 65 grizzly bear deaths — 37% — occurred outside the monitoring area.
When wildlife managers take stock of the ecosystem’s population annually, deaths outside of the monitoring area don’t count toward thresholds that the three Northern Rockies states agreed to in their grizzly bear conservation strategy. In fact, van Manen doesn’t expect that the near-record mortalities will exceed any of the limits in place for independent females, males and dependent young.
A grizzly bear sow with her cub in Grand Teton National Park. (Leine Stikkel)
“I think we’re still going to see population growth, because we also had a pretty good year for females with cubs,” van Manen said. About 200 cubs, he said, are born into the population every spring, and about 30% of those survive to independence.
“That’s pretty solid recruitment into the population every year,” van Manen said. “That’s what keeps this whole dynamic on the positive side — still having population growth.”
The Montana and Wyoming biologists shared the belief that the relatively high mortality rate is not concerning from a population standpoint.
“We have a healthy, recovered grizzly bear population that’s going to sustain mortality,” Smith said.
The numbers are all relative, Thompson stressed. More living bears means more dying bears. The Yellowstone region’s grizzly population has steadily grown inside the monitoring area, and outside it’s swelled to an unknown degree.
“It’s a high number, but I still don’t think it’s limiting the bear population,” Thompson said about mortality. “We’ll be able to demonstrate that with our annual assessment.”
Whether the Greater Yellowstone Ecosystem reaches 70 grizzly deaths and sets a new record depends on how the last month or so goes while bears are out of the den.
“Some are already close to denning up,” van Manen said. “Their movement rates are starting to be reduced substantially, and that alone makes them less vulnerable.”
Nevertheless, 2024 “clearly has the potential” to set the high mark, Thompson said.
“I thought we’d hit it [the record] a few weeks ago, quite honestly,” he said.
The slowdown in grizzly bear conflicts and mortalities since mid-October has been welcomed — and not just for the bruins’ sake.
“It’s been a very mentally and physically stressful year for our people,” Thompson said.
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