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CDOT says Vail Pass project an example of agency’s focus on creating safe passage for wildlife

New report says construction of new crossings will be key in creating contiguous habitat

A mule deer eyes I-70 on Vail Pass in this CDOT-provided image set up to capture wildlife in the area. A new project on Vail Pass will see the construction of six new wildlife underpasses.
CDOT/Courtesy photo

A new report on big game species in Colorado gets right to the point: Wild animals are suffering.

The report, published Sept. 27 and titled “Opportunities to Improve Sensitive Habitat and Movement Route Connectivity for Colorado’s Big Game Species” was a cooperative effort between the Colorado Department of Natural Resources, the Colorado Division of Parks and Wildlife and the Colorado Department of Transportation.

“The West’s iconic big game species, such as bighorn sheep, pronghorn, elk, moose and mule deer are important to natural systems, sporting enthusiasts and local economies, but some species and local populations have suffered significant declines in recent decades,” the report concludes.



“Between 2007 and 2013, Colorado’s estimated statewide deer populations declined from roughly 600,000 deer to approximately 390,000 deer,” according to the report.

Habitat loss and fragmentation stemming from residential, recreational, and industrial development is the major risk to the species, and a solution is seen in creating and preserving contiguous swaths of the sagebrush, grassland, and forest landscapes.



But habitat fragmentation can be exacerbated by roads, which undermine efforts to create contiguous swaths of habitat.

Among the major suggestions in the report is ‘facilitating safe passage along migration and movement routes — within and between seasonal ranges.“

In other words, the creation of more wildlife crossings below and above roadways in Colorado.

Lynx crossing

In 2021, CDOT and CPW created an interactive online map which shows all of the dedicated wildlife crossing structures along Colorado roads.

The interactive map went live in August and details the types of wildlife crossings found in Colorado along with their locations; it also details the species targeted in the creation of the crossings.

Most of the targeted species in Western Colorado include mule deer and elk, but on Vail Pass, another species is listed: the Canada lynx.

A screen shot from CDOT’s new wildlife crossings interactive online map, which went live in August. Canada lynx is listed among the target species on a wildlife crossing area in East Vail.
CDOT/Courtesy image

The lynx is protected under the endangered species act in the U.S. and was the subject of CDOT’s 2019 “Western Slope Wildlife Prioritization Study,” which said lynx use the bridges on Vail Pass to cross the highway “long natural drainages under eastbound span bridges at night, particularly during low traffic periods.”

After the last known lynx in Colorado was illegally trapped and killed on Vail Mountain in 1973, a reintroduction effort commenced in 1999, with 218 radio-collared lynx transported into Colorado from Alaska and Canada.

This map, published by the Colorado Department of Parks and Wildlife in 2012, shows collared lynx summer migration lines in yellow, winter migration lines in blue. The green squares represent areas where lynx have been hit and killed by automobiles on Vail Pass.
Screen shot/Colorado Parks and Wildlife map

While the reintroduction was deemed a success, vehicle collisions with lynx have been numerous since the reintroduction and are considered an important mortality factor for reintroduced lynx in Colorado. Since reintroduction, vehicle collisions have been the cause of 20 percent of all lynx deaths recorded in the state.

Two of the lynx deaths have occurred on Vail Pass between mile markers 187 and 190. Currently, the eastern-most underpass for lynx to use on Vail Pass in Eagle County is situated at Mile Marker 185. The next I-70 wildlife crossing to the east doesn’t occur for more than 60 miles, according to CDOT’s interactive wildlife crossings website.

Interesting mix

Currently under construction, CDOT’s $140 million I-70 West Vail Pass Auxiliary Lanes Project will construct six new wildlife underpasses between mile markers 187 and 190, where the lynx deaths have occurred.

It’s the culmination of an effort decades in the making, one that has created many memorable illustrations, but no actual crossings.

A Google image search shows different illustrations of ideas for wildlife crossings on Vail Pass.
Screen grab

The nonprofit group Wildlands Network, which seeks to reconnect North America in an effort to reduce species extinctions, has identified Vail Pass as a priority wildlife corridor within the Western Wildway, a 6,000-mile corridor of somewhat-connected public lands between Mexico and Alaska.

Wildlands Network Conservation Director Greg Costello says Vail Pass is critical in promoting north-south migration into southern Colorado and Northern New Mexico.

Vail Pass has “always, historically, been a huge mixing ground of species, species from warmer climes and colder climes, a big mixing zone of biodiversity,” Costello said.

Most I-70 wildlife crossings target mule deer and elk and, therefore, human safety in reducing collisions. And in East Vail, lynx currently adds an interesting mix to the species targeted in the existing wildlife crossings between mile markers 183 and 185.

With the six new wildlife crossings being constructed between mile markers 187 and 190, however, the targeted species list will really get interesting.

This I-70 West Vail Pass Auxiliary Lanes construction map shows where wildlife crossings will be constructed as part of the $140 million project which began in August.
CDOT/Courtesy image

Four small to medium sized underpasses will target small mammals including American marten, bobcat, coyote, red-tailed fox, short-tailed weasel, snowshoe hare and yellow-bellied marmot.

“And then two larger (underpasses) are based around lynx and deer and elk,” said civil engineer John Kronholm with CDOT.

Kronholm is currently studying wildlife cameras on Vail Pass, where he has seen coyote, fox, deer, elk, bighorn sheep, marmot, squirrels and chipmunks.

“There’s wildlife that come down to the highway, and there’s no doubt the highway is a barrier,” Kronholm said. “They either turn around, or they get run over.”

In the state’s recently published report on big game habitat in Colorado, CDOT is tasked with prioritizing new funding for transportation projects identified by CPW and CDOT which provide a clear benefit to wildlife populations.

It’s a task the department has already set about accomplishing, CDOT director Shoshana Lew said.

“It’s increasingly just a part of what our project planners are doing,” Lew said. “When I got to CDOT, not very long ago, there was a group that was very passionate about the wildlife crossings who was doing most of the work, since then, it’s just started to become a part of projects.”


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