Study: Crossings on Highway 9 reduced wildlife collisions by 90%

Amy Golden
SkyHi News
Wildlife is pictured using the overpass and underpass crossings along Colorado Highway 9 north of Silverthorne during a five-year study. Seventeen species used the crossings throughout the duration of the study.
Photos from Colorado Parks and Wildlife

KREMMLING — A total of 112,678 mule deer have successfully crossed Colorado Highway 9 in the past five years thanks to its seven wildlife crossings.

On Tuesday, June 22, Colorado Parks and Wildlife biologist Michelle Cowardin presented to Grand County commissioners the findings from the finalized monitoring research on the Highway 9 wildlife crossings.

The seven crossings from Green Mountain Reservoir north to Kremmling include two overpasses and five underpasses along with 10.3 miles of fencing, 29 wildlife guards and 61 escape ramps. The work on the 11-mile stretch of road was completed in 2016 by the Colorado Department of Transportation in cooperation with Parks and Wildlife and many other partners.

Wildlife-vehicle collisions reduced dramatically after the crossings were added, decreasing by more than 90% according to the reporting from three data sets, including carcass counts and crashes reported to law enforcement.

According to Parks and Wildlife, prior to installation, an average of 63 wildlife carcasses were recorded along the stretch of road each winter with 98% of those being mule deer.

The more than 100,000 crossings on the passages by mule deer alone far surpassed other projects, according to Cowardin.

“That number far exceeded any other studies that have been done in the West,” she said. “One reason for that, we believe, it’s also to date the only crossing project that has occurred within winter range. All the other crossing projects are occurring within these migration and movement corridors.”

Mule deer were the main species the crossings targeted, but there were 17 species that successfully used the crossings over the five-year monitoring period from November 2015 to May 2020. Elk, moose, pronghorn, white-tailed deer and bighorn sheep also used the passes.

“We never even anticipated or planned for sheep,” Cowardin added. “We didn’t even know sheep were (crossing Highway 9) until we caught them on camera the first year.”

Over the five-year study, 489 elk took the underpasses with use increasing over time. Elk tend to be more nervous about using the crossings but still had a 91% success rate, meaning the elk actually crossed after approaching.

Other animal users included badgers, black bears, bobcats, coyotes, mountain lions, rabbits, raccoons, foxes, skunks and — at least once — turkeys and river otters.

“Which was bizarre miles from any water,” Cowardin said about the otters.

The Blue Valley Acres underpass saw the highest use followed by the north and south overpasses.

As for the wildlife guards, hoofed mammals were deterred 81% of the time compared with 15% of the time for animals with padded feet. Round bars on top of the guards were best at deterring crossings, which Parks and Wildlife suggested the Colorado Department of Transportation use in the future on low-traffic roads.

The benefit-cost analysis by Parks and Wildlife’s consultants found that the $15.7 million mitigation project will pay for itself after 56 years due to the reduction in crashes. This is less than the minimum lifespan of the structures, which is 75 years.

“This project is touted around the country not only for the monitoring results but even more so the process that happened with the funding and how the project took shape,” Cowardin said, thanking the commissioners for the county’s contribution to the project. “… You’re saving lives. You’re saving a lot of human lives along with keeping our wildlife populations healthy.”

Most wildlife collisions are now happening between the south end of the fence and Green Mountain Reservoir. Cowardin said the Summit County Safe Passage plan is exploring the possibility of expanding the project, though there is no funding to do so.

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