For decades, researchers have predicted that an uptick in traffic volume on western Montana’s busy highway corridors will present increasing challenges for the region’s grizzly bears, which frequently cross the roadways as they move between critical habitats.
So far this year, 27 grizzly bears have been removed from the Northern Continental Divide Ecosystem’s population, 13 of which are classified as removals due to “vehicle collisions.” Nine of those bears were killed in collisions, while four are orphaned cubs that have been or will be rehomed.
The year’s total is the most on record for the Northern Continental Divide Ecosystem (NCDE), a sprawling region situated in Northwest Montana, which includes Glacier National Park, portions of the Flathead and Blackfeet Indian reservations, parts of five national forests, Bureau of Land Management lands, as well as state and private lands.
And while the 2018 figures may represent an outlier, it’s grabbed the attention of those charged with researching, recovering and protecting the region’s grizzly bear population, which received federal protections under the Endangered Species Act along with all other grizzlies in the Lower 48.
On July 27, a motorist on U.S. Highway 93 ran into a sow grizzly and two of her cubs just south of Ronan. The accident apparently occurred when the family of bears emerged from an irrigation ditch and attempted to cross the highway after dark. All three bears died in the collision, which injured the driver and a passenger.
Meanwhile, biologists with the Confederated Salish and Kootenai Tribal (CSKT) Wildlife Management Program discovered a third cub nearby the following day, and are now trying to place it in an accredited zoo or sanctuary.
“An orphaned bear is still considered a removal from the population,” Stacy Courville, a tribal bear biologist with CSKT, said. “So far this year, we’ve had 13 bears removed from the population — seven males, five females and one unknown. And three of them were from right here.”
In May, a female cub was hit and killed on Highway 93 north of St. Ignatius.
And on July 24, Montana Fish, Wildlife and Parks officials discovered a dead adult female grizzly bear in the Spotted Bear area south of Hungry Horse Reservoir.
FWP researchers originally captured the 16-year-old grizzly bear in 2016 as part of a population-trend monitoring program. FWP fitted the bear with a GPS radio collar, and the collar alerted agency personnel of the possible mortality.
FWP staff discovered the dead bear and retrieved the collar on July 24. Due to decomposition of the carcass, FWP was unable to determine a cause of death.
“This is a big year for highway mortalities,” Courville said. “I don’t think we’ve ever hit this many bears.”
To put the mortalities in context, between 2004 and 2017, a total of 10 bears were killed on a 13-mile stretch of Highway 93 between Ronan and St. Ignatius; five have already been killed or orphaned due to collisions this year alone.
“I hope it’s not the new normal,” Courville said.
In comparison to the other highways in the NCDE — U.S. Highway 2, U.S. Highway 89, Montana Highway 200 and Montana Highway 83 — Highway 93 records the most deaths per mile.
Looking at a map of highway mortalities in the NCDE, Courville notes that grizzly mortalities are fairly spread out across the NCDE “except for on the reservation.
“I don’t know what we can do on Highway 93,” he said.
In fact, much has already been done on 93 to mitigate the risk of traffic on grizzly bears, to varying degrees of success.
In conjunction with the Montana Department of Transportation and the Federal Highway Administration, CSKT has worked to construct safe passage for wildlife, including 41 crossings that include the “Animals’ Trail,” a 197-feet wide vegetated bridge that spans the bustling highway, which are located in areas known to be popular for wildlife crossings, and which have high rates of mortality.
In Northwest Montana, 1,000 grizzlies are estimated to live in the NCDE. The area covers about 21,300 square miles between Glacier National Park and Missoula, and is slightly smaller than the Greater Yellowstone Ecosystem surrounding Yellowstone National Park.
Between 2012 and 2013, Glacier Park wildlife biologists John Waller and Clayton Miller measured vehicle traffic volume at two locations on U.S. Highway 2 along the park’s southern boundary, and compared the results to those collected between 1999 and 2001.
“We show that traffic volumes have increased substantially in the 11 years between counts and that the increases are most dramatic during the hours in which grizzly bears are most likely to cross the highway,” according to the study, “Decadal Growth of Traffic Volume on U.S. Highway 2 in Northwestern Montana.”
“Over the preceding decade, grizzly bears have lost two hours of suitable crossing opportunity and will, should observed growth rates and traffic continue, lose an additional three hours within five years,” the report states.
Although Highway 2 remains relatively lightly traveled by motorists compared to other arterials in western Montana, Waller said it’s growing, and hopes the research will help mitigate the continued swell in traffic volume and its impact on grizzly bear crossings and the connectivity of bear habitat.
The study, he said, could help inform construction and expansion projects on the highway corridor to include crossings and bridges, similar to CSKT’s.
“We’re trying to get ahead of it so when expansion does occur, the highway departments will be prepared,” he said.
Cecily Costello, a grizzly bear research biologist with FWP, said the agency’s mortality data tracks the first documented road-killed grizzly bear in the NCDE back to 1983.
“Since then, we have had 64 mortalities that we have been able to document,” she said, adding that “mortality” includes orphaned cubs. “This year, four mortalities were cubs that were captured and brought into captivity. We do see a little bit of an increase over time. We’re seeing an increase in bear numbers, an increase in human numbers, and we also know the grizzly population is expanding its territory. It’s not unexpected for this to increase, but obviously we are keeping an eye on it.”
In the past decade, grizzly mortalities due to vehicle collisions have averaged 2.7 bears annually, while the NCDE’s bear population is estimated to be growing at a rate of 2.3 percent annually.
With the NCDE slated to be delisted from the Endangered Species Act by the end of the year, and returned to management by the state, a conservation strategy is in place to prevent the bear population from slipping below a certain threshold, which the Interagency Grizzly Bear Committee has set at 800 bears.
To stay above that threshold, the strategy allows for an average of 25 grizzly mortalities or removals per year in the NCDE, a figure that is dependent on several factors, including snowpack, the health of berry crops, and other issues that can increase the chance of a conflict with a human.
This year’s mortality figures have already passed the threshold, and bears will continue to grow more active as they prepare for winter denning.
“It’s like this across the whole NCDE, so we need to pay attention,” Courville said. “The next closest year for mortalities was 2007, and that was only eight for the entire ecosystem. We’re already at 13.”
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