Biologists with IGBST and the National Park Service fit a grizzly bear with a radio collar in 2016. Once a bear is radio collared, biologists can track its movements with telemetry. (USGS)

The Yellowstone Ecosystem grizzly bear population fell by 10 bears from 2019 to 2020 and now numbers 727, according to new estimates from an interagency team of scientists. 

The figure accounts for the grizzly bear population in the 19,270-square-mile demographic monitoring area in and around Yellowstone National Park. Bears in that area are monitored under the auspices of the Endangered Species Act.

The decline — about 1.4% — is no reason to worry about the population’s size, a top team biologist wrote.

“There is no biological significance to a 10-bear difference in the estimate from one year to the next (up or down), considering the inherent variation in these estimates,” Frank van Manen, supervisory research wildlife biologist with U.S. Geological Survey’s Interagency Grizzly Bear Study Team, wrote in an email.

The estimate meets the 500-bear goal necessary to qualify as a recovered population under the Endangered Species Act, although managers seek a buffer above the figure. Grizzlies remain listed as a threatened species while the U.S. Fish and Wildlife Service resolves court-specified deficiencies in plans to remove federal protections.

The 2020 summary (see below) is a factual report, van Manen wrote, not a policy document that determines whether numbers meet ESA population recovery goals. “Given the science role of IGBST, we provide the demographic findings for managers to determine whether demographic monitoring criteria are met,” he wrote.

The IGBST releases the full annual report later in the year.

At the hand of man…

In the last five years annual population estimates have ranged between 695 in 2016 to a high of 737 in 2019. Thirty grizzly bears were known to have died or probably died in the DMA last year, the summary states.

Twenty-eight of those died due to human causes, according to the 2020 summary. That means human-caused mortalities account for 93% of the known and probable deaths.

Wildlife managers in 2020 euthanized a 34-year-old old grizzly bear caught killing cattle after they saw its worn teeth and poor condition. (Wyoming Game and Fish Department)

Human-caused mortalities included bears captured and euthanized after killing livestock or frequenting developed areas after becoming habituated to human food, or after being struck by vehicles. Several deaths remain under investigation, a category encompassing grizzlies killed by hunters or others claiming self-defense.

Thirteen of the human-caused mortalities were “management removals” — mostly involving high-conflict, dangerous or unfit bears euthanized after run-ins with people or their property.

The summary provides other clues to the health of the population, including the sightings of females with cubs in the ecosystem’s core. The center of the ecosystem — an area covering 48% of the DMA — is subdivided into 18 bear management units where grizzly mothers are highly valued.

Observers documented females with young in all 18 of the units in 2020, a figure that’s held constant for three years running.

The summary also pegged estimated mortality for independent females in the DMA at 7.5%. That figure that will be considered along with previous years’ information before managers determine whether recovery goals involving that metric have been met.

Another reason the 10-bear difference is insignificant is the “conservative nature of the Chao2 estimation technique,” that was used to arrive at the figure, he wrote.

The Chao2 model gave scientists a high degree of confidence there are between 648 and 806 bears in the DMA, according to the team’s summary of monitoring in 2020.

Scientists also compiled information on several grizzly food sources and determined that a key one — whitebark pine nuts — appears to be holding up. Beetle infestations threatened the species abundance in the ecosystem. 

The number of whitebark pine cones found along delineated survey routes remained “similar to the long-term average,” the summary states. “These data suggest the mountain beetle outbreak has run its course,” the paper reads.

Certainly, many Yellowstone grizzlies live unseen lives, rarely observed or counted by humans even after their demise. Nevertheless, the monitoring program includes exhaustive detail gathered from ground observations, flights to spot bears hunting army cutworm moths in talus fields, surveys of spawning trout and other data-gathering. 

Grizzly skulls and other remains found years after a bear’s demise are eventually incorporated into the database.

Wyoming conflict captures decline

Last year wildlife managers also recorded 19 grizzly deaths outside the DMA, where the population is irrelevant to federal recovery goals. Wyoming Game and Fish Department tracks statewide grizzly activity, reporting 26 captures in Wyoming in 2020, down from 33 in 2019.

Eighteen of the bears caught for conflicts in Wyoming were removed in coordination with the U.S. Fish and Wildlife Service. That’s the same number taken out in 2019 and includes bears inside and outside the DMA.

The location of grizzly captures in Wyoming in 2020. The red boundary marks the limit of the ecosystem core recovery area and the black one the edge of the demographic monitoring area. (Wyoming Game and Fish Department)

Some bears trapped for conflicts get another chance. Game and Fish last year relocated nine bears it trapped, down from 15 in 2019.

The availability of natural foods has the biggest influence on the ebb and flow of capture and removal numbers, said Brian DeBolt, Wyoming Game and Fish Department’s large carnivore conflict coordinator. The recent high tide of grizzly removals in 2018 illustrates that point, he said.

“It was just the result of poor natural foods,” he said. “We had a lot more bears encountering a lot more people.”

Grizzlies were “aggressive in the backcountry,” in 2018 he said, another indication of that poor food year. A grizzly killed a hunting guide in the Teton Wilderness that year.

Game and Fish dealt with more than 200 conflicts in 2020, DeBolt said. The agency resolved most of those without having to capture a bear.

In about 80% of cases, “we were able to resolve that conflict in some other way,” he said. “We were able to erect an electric fence … or remove the attractant.”

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Removals of grizzlies protected by the Endangered Species Act “are not taken lightly” he said. Those decisions rest with the U.S. Fish and Wildlife Service, which largely relies on Game and Fish field personnel for trapping, relocation and information. “We try to target those individual bears that chronically cause problems,” DeBolt said.

Angus M. Thuermer Jr. is the natural resources reporter for WyoFile. He is a veteran Wyoming reporter and editor with more than 35 years experience in Wyoming. Contact him at or (307)...

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  1. Everyone is sure worried about the bears. If the game dept. was half as worried about the deer and elk populations they wouldn’t worry about the bears. When the bears get most of the elk calves is certain areas , the elk population has to go down but nothing is said about that. You have idiots from the east coast that think they have more to say about the game in wyo. than we do. why don’t you come out with a survey that is conducted without bias to the worthless bears and you would know that most people would vote to shoot bears on sight. The same goes for the wolves. When more people go to other states than they do now just because there aren’t the deer and elk like thee was 20 years ago that is when the game dept . feel it it their fat pocket book. I am 77 years old and have hunted the dubois area for years and the last 4 or 5 years you don’t see any elk like there was. Don’t have to tell me it is the habitat. I heard that from the silly wardens before. I guess it is time the game dept got there head out of their rear and started taking care of the bears and wolves like they should.

    1. I understand that you have an axe to grind with the game and fish. However, elk populations have been increasing the past couple of years. I, and others, provided the links for you after your last comment about never seeing any elk anymore.

      You can be critical of the game and fish, but at least use fact based arguments. Saying that there aren’t any elk anymore is disingenuous and dishonest.

      As I said in my last reply to you on this subject, you should try getting off the road to hunt. You might have better luck.

  2. I am suspicious of any “numbers” generated by state agencies in a state that favors environmental plundering for its income, one that worships a public-welfare-supported livestock industry that contributes next to nothing to the national food supply or to the state domestic product (or whatever economists call it these days), in a country where propaganda is regarded as gospel. The Fish and Wildlife Service has yet to recover from trump’s idiocy.

  3. I appreciate the reporting here, but I find the title misleading. These are not “counts” you’ve reported but “estimates.” A count is when someone does a survey and reports the number of individual bears they saw. An estimate is generated based on count data, but also attempts to figure out how many bears are _actually_ there (i.e., those we saw, plus those we missed). Secondly, because this is an estimate it can’t be properly viewed as just one number. These estimates, as you’ve reported, encompass a range of values. Plus or minus ten bears is well within the range of what was observed in the previous year, so higher or lower estimate of this magnitude can’t properly be viewed as a increase or a “slip”, respectively, in bear numbers.