JACKSON — After two recent, high-profile grizzly attacks in the Greater Yellowstone Ecosystem and a media ecosystem that amplifies news of attacks nationwide, grizzly researchers say attacks are up — modestly.
But the full story is likely more complicated.
“When people say they’re more common, there is some truth to that in absolute numbers,” said Frank van Manen, leader of the ecosystem’s Interagency Grizzly Bear Study Team. “But that is primarily because bear range is three times larger than it was back in the ’70s and ’80s.”
Van Manen and other Yellowstone-area bear researchers also see evidence that bear attacks are proportionally flat, given how significantly grizzlies’ range has expanded, and how many more people and bears are occupying the same habitat.
When asked about trends in bear attacks, Kerry Gunther, Yellowstone’s bear management biologist, thinks about the growth of the human population in the Greater Yellowstone, the number of new homes being built on private land and the skyrocketing visitation to the area’s national parks. In Yellowstone, that number climbed from 2 million annual visits when Gunther started with the park 40 years ago to over 4 million today.
“If you look at just the number of attacks, the frequency is going up a little bit,” Gunther said, concurring with van Manen. “But if you look at it on a per capita basis, per visitor, it’s actually flatlining.”
Dan Thompson, large carnivore supervisor with the Wyoming Game and Fish Department, largely concurred with van Manen and Gunther. But he, like other biologists, cautioned that statistics are one thing.
“With millions of visitors and a lot of bears, five doesn’t seem like a lot. But if that’s you or your loved one, it’s a big deal, obviously,” Thompson said. “We know these things are going to garner media attention because they are rare, but there’s a visceral component to these things that is not really easily quantified.”
In the past few decades, grizzly bears have slowly occupied more and more habitat in the Greater Yellowstone Ecosystem. In 1990, they were largely confined to an area that federal officials deemed the “recovery zone,” roughly 9,200 acres around Yellowstone and Grand Teton National Park. Now, more than 30 years later, bears occupy some 42,000 square miles around Yellowstone in Wyoming, Montana and Idaho. Bears that inhabit the Northern Continental Divide Ecosystem around Glacier National Park are also inching closer.
As grizzlies have ranged farther and farther afield, leaving forests and entering more and more areas frequented by humans, attacks have trickled up.
But characterizing the increase depends on how you parse the numbers.
Van Manen, for example, was looking at attacks since 2005 — the first year attacks started to frequently occur outside of the demographic monitoring area, which state and federal officials consider “suitable habitat” for grizzlies. Outside of the demographic monitoring area, there’s more human development. Game agencies are also less likely to tolerate bears that hassle humans by getting into garbage or preying on livestock.
Before 2005, there were an average of 4.3 attacks a year in the Greater Yellowstone Ecosystem, according to Interagency Grizzly Bear Study Team data.
After 2005, that average bumped up to 6.1, largely due to two attack-heavy years in 2011, when 14 people were injured by bears, and 2020, when 11 people caught the wrong end of the omnivores’ claws.
But compared to the previous decade, the average is a bit down.
From 1992 to 2002, there were an average of 4.18 attacks annually. From 2002 to 2012, there were an average of 6.45 attacks. And from 2012 to 2022 there were an average of 5.45 attacks.
In concluding that fewer attacks are happening on a per-capita basis, van Manen keyed in on the “recovery zone,” which bears have occupied since well before 1992, the beginning of the grizzly study team’s data.
In the “recovery zone,” “attacks are more or less flat,” van Manen said. But visitation has skyrocketed.
“The reality is that there are more people using and recreating in that recovery zone, yet there is no trend in terms of incidents that result in human injuries,” van Manen said. “If anything, that would suggest to me that on a per-encounter basis, that number is probably actually declining.”
That, he, Gunther and Thompson said, is because people are better educated about how to deal with bears.
People know to avoid hiking and running alone, to make noise in the woods, to avoid moving through forested areas at dusk and how to respond if attacked by a grizzly bear: Use bear spray, or drop and cover if they don’t have bear spray, if it doesn’t work or if a bear actually makes contact with them.
“People are much more informed these days about how to respond to grizzly bear encounters, and they’re better prepared with bear spray and other things to deal with such an encounter,” van Manen said.
“So I think there’s actually some positive news in that,” he said.
Thompson said part of that is likely because agencies have worked tirelessly to educate people about how to reduce conflicts with bears, like by locking up garbage, compost and other attractants that can lure them into developed areas. That work, he said, has taken decades.
Bear attacks, however, have ticked upwards outside of the recovery zone because bears are occupying a larger range, van Manen said. Mostly, those attacks have happened since 2005.
“Those are the areas that were most recently colonized by grizzly bears,” he said.
As grizzlies’ range has expanded, Thompson said the timing of bear attacks has also changed.
“In the past more of our injury situations have occurred in the fall,” Thompson said. “We’re starting to see those spread out in the spring and summer.”
Data that Gunther is set to publish from Yellowstone in the scientific journal Human Wildlife Interactions show that bear attacks are far from the most frequent killer in Yellowstone’s history. Between 1872 and 2018, seven people were killed by bears in the park. In contrast, some 121 people died by drowning. Another 39 died by falling off cliffs. Seven were killed by falling trees. And another five were killed by lightning strikes.
But 26 people have died by suicide, which Gunther highlighted as a problem.
“We go to great lengths with bear safety,” Gunther said. “We maybe should do more for suicide.”
Other data, which Gunther recently published in the journal Human-Bear Conflicts, detail human-bear encounters reported to Yellowstone from 1991 to 2022. It shows that 55% of the time, bears reacted to human presence with no overreaction; 33% of the time, they walked or ran away; 3% of the time, they reacted curiously. Another 4% of the time, they reacted with stress, agitation or threatening behavior.
Grizzlies attacked people less than 1% of the time, and Gunther believes that estimate is likely biased toward aggression.
Most people who see a bear and casually observe it don’t report their sighting to the park. Reports typically come in when someone gets bluff charged or injured and needs medical assistance.
But Gunther also highlighted data showing that attacks are more frequent when people are off-trail in the backcountry, in areas where bears are less accustomed to human presence.
Still, those incidents are rare, Gunther said.
“It’s kind of a catastrophic event that rarely happens,” Gunther said. “That’s what makes the safety messaging so difficult. If there’s a one in 64 million chance, a lot of people just aren’t going to take the precautions, even though it can result in severe injury or death.”
This year, there have been two high-profile bear attacks on lands surrounding Yellowstone National Park.
In July, Amie Adamson, 48, of Derby, Kansas, was apparently attacked and killed by a bear in West Yellowstone, Montana.
Officials have said Adamson, a marathoner, was likely running at the time of the attack, which can surprise a bear and trigger a predatory response. She was traveling alone and not carrying bear spray — as countless others do in the Greater Yellowstone, including in Jackson Hole. Officials with Montana Fish, Wildlife and Parks said the bear was likely acting defensively.
“It’s completely normal and natural for grizzly bears,” Morgan Jacobsen, a spokesman with the state agency, said at the time. The department had no witnesses and no signs of the bear that killed Adamson. The cause of death was excessive blood loss caused by a bear mauling, the coroner’s office said.
Her mother, Janet Adamson, told “Good Morning America” that her daughter died doing what she loved: taking an early morning walk, hike or run. “Every morning, she just was almost in heaven,” Adamson said.
Then, in August, a man working in a remote corner of the Shoshone National Forest near Dubois was attacked by a bear after surprising it at close range.
The man has not been identified, and Thompson said he wants to remain anonymous.
He didn’t have time to deploy his bear spray, and instead dropped to the ground, covered his head and didn’t fight back against the bruin.
“The person responded textbook perfectly,” Thompson said. “He resisted the urge to run, dropped and covered, which is easier said than done. He did what he was supposed to do.”
The bear did bite the man a few times, but once there was no threat, the bear left, Thompson said. That man is recovering well, Thompson said.
“The big takeaway is that bears are actually pretty tolerant of us and these events are actually pretty rare,” Gunther said. “A lot of what could be done to prevent them would be human behavior changes.”
Van Manen put it differently.
“Bears are behaving like they always have,” he said. “They’ve remained very rare incidents, fortunately. But again, there’s no indication that bear behavior is changing or that bears are becoming more aggressive.”
But Thompson cautioned that statistics are only part of the story. An attack is an attack.
“If it does happen to you,” Thompson said, “what would that mean?”