Drive along Highway 21 from Boise, about 10 miles past Lucky Peak, and you’ll come upon a tunnel with a bridge above it. The bridge is not for cars to cross over the highway; it’s for animals. Metal fencing guides wandering creatures over the road.
“It looks fantastic,” said Gregg Servheen, who retired from the Idaho Department of Fish and Game (IDFG) after three decades.
Roads connect people and goods from point A to point B. But for animals, roads fragment important swaths of habitat. During his time at IDFG, Servheen recommended projects like this to help migrating wildlife safely move between their seasonal destinations.
Scattered across Idaho, there are a handful of tunnels carved under roads that allow wildlife to pass through and avoid collisions with cars. But this roughly $7 million bridge by Cervidae Peak is the state’s first overpass dedicated to wildlife. Some studies have shown animals like elk and moose prefer open overpasses compared with narrow underpasses.
“It’s been a lot of years in the making,” Servheen said on his first visit to the structure, which was completed last fall. “It’s so great to see.”
Infrastructure, ranging from bridges and tunnels, to roadside fences and culverts, are increasingly being employed to stitch together wildlife corridors. However, Servheen, and several experts knowledgeable about wildlife migrations, worry Idaho lags other western states in tackling wildlife-vehicle collisions and habitat fragmentation.
There are more than one million crashes between vehicles and large animals every year in the U.S., causing about 26,000 injuries to people and 200 human deaths.
The toll for animals is becoming more apparent, too. Wildlife managers now have a much clearer picture of how and where animals move compared to a decade ago, thanks to improved technology that sends high resolution data points from GPS collars.
Several experts lauded IDFG for its robust collection of migration data and its citizen-populated database of roadkill incidents, which helps pinpoint danger zones.
Put together, this information has revealed the significant disruption that roads cause to animal movements. For animals, approaching a highway can mean approaching prolonged suffering or death. It can also mean facing an impassable wall of cars.
“The deer turn around and no longer make the migration,” said Servheen, “and that's the beginning of the end in terms of the health of a population.”
Idaho’s first overpass stretches across a crucial route. More than 8,000 deer, elk and antelope migrate down to the Boise River Valley each winter when it’s too snowy in the central Idaho mountains. They make the trek back in the spring.
In 2016, Fish and Game counted 77 deer and elk carcasses along this highway stretch. As Boise’s population grows, more vehicles are on the road.
“As the traffic increases, it's just going to increasingly result in more dead deer,” said Servheen.
The Idaho Department of Transportation, which spearheaded the project, said the overpass will benefit both people and animals, and could reduce collisions by about 80%.
Across the country, wildlife crossings are gaining traction, boosted by federal and state investments. The federal government has allocated $350 million from the Bipartisan Infrastructure Law for building crossings over the next few years. Utah has over 50 wildlife bridges and tunnels and has committed $20 million in state dollars toward building more. Wyoming has more than 30 projects with 10 planned or in the works. In addition, its wildlife and transportation agencies have come together to form a statewide plan for reducing collisions.
“Yet, just over the border in Idaho,” said Brian Brooks, the director of the Idaho Wildlife Federation, “we're tiptoeing around these issues.”
According to the Idaho Department of Fish and Game, the state had 10 underpasses dedicated to wildlife before the construction of the first overpass in 2023.
In 2018, residents in Fremont County, Idaho, bordering Montana, resoundingly rejected a proposal for three wildlife overpasses in their county. Though the results were non-binding, 80% of voters opposed the crossings suggested by ITD on Targhee Pass along U.S. Highway 20.
Many residents were skeptical about erecting bridges and associated fencing, as detailed in a report by High Country News.
“We don’t want to be a community of just nothing but fences along Highway 20,” said Ann Marie Anthony, the publisher of Island Park News.
Some worried about impeding private property rights and access to public lands. For others, the opposition was based on the idea that those advocating for the crossings were coming from outside the community.
The outcry surprised Patricia Cramer, a transportation ecologist whose research was the basis of ITD’s proposal and who had worked on many similar transportation projects in other states.
“I was dumbfounded in some respects,” said Cramer. “Like, wait a minute, we're coming into a community saying, look, we're going to help make your life safer.”
State lawmakers got involved, and, in 2019, the Idaho Legislature passed a memorial urging the federal government to ensure that local stakeholders are “quickly and fully informed whenever wildlife crossing infrastructure is proposed as an option for a transportation project and that state transportation agencies be given clear guidance to that effect.”
ITD withdrew the plan that included crossings. IDFG, which had been helping supply wildlife information, backed away, too.
“Up until that point, the idea of bridges with trees on them was a pretty benign idea, at least politically,” said Brooks, whose organization supported the crossings.
In fact, a survey released by Colorado College this year found broad bipartisan support for wildlife crossings around the West. In Idaho, 89% of respondents said they support constructing such structures across major highways that intersect with migratory routes.
Still, Cramer, who is now working as a contractor for ITD on an updated map of collision hotspots, said the Targhee Pass dispute has had a lasting effect, at least in this part of the state.
“That experience totally has affected both the wildlife and transportation agencies,” she said. “They're very hesitant to suggest any wildlife crossings.”
Brooks with the Idaho Wildlife Federation agreed. He said the state is worried about another project getting politicized, so it’s moving slowly.
But Jacob Gray, a big game and migration program coordinator at IDFG, said that’s not necessarily a bad thing. Community input is important.
“That's a key foundation to where we want to work in Idaho,” he said. “We want to work where people want the work done.”
ITD is currently in the beginning stages of proposing another road project on US-20 in eastern Idaho. The two-lane road could be widened to four in some places to accommodate increasing traffic.
But it’s also a key corridor for moose, elk and deer moving in and out of Yellowstone National Park.
“If we don't figure out some sort of wildlife permeability strategy with that expansion, it'll have drastic and negative impacts on our big game in that area,” Brooks said.
It’s early in the planning process, but as of now, ITD is not suggesting regular wildlife crossings as part of the construction. It said it’s analyzing “mixed use” crossings, open to animals, but also people on ATVs and snowmobiles. Some environmental groups are concerned that’ll spook wildlife and they won’t use them.
In feedback sent to ITD, IDFG wrote that while the efficacy of wildlife crossings has been “rigorously evaluated and demonstrated to be effective in many locations,” the agency was “unaware of any evaluation regarding the effectiveness of roadway crossing structures designed to be used by wildlife and people (pedestrian or mechanized).”
Blair Dance, a Fremont County Commissioner, who was not in office during the Targhee Pass proposal, said the community might be more amenable to the mixed use crossings because their suggested locations are ones that would help recreationists safely cross the highway.
“With that, I believe the sentiment of opposition is reduced significantly,” he said.
A little more than a week after construction of Idaho’s first wildlife overpass near Boise was complete, IDFG installed a wildlife camera. That night, the camera snapped a picture of a deer crossing the bridge. About a month later, it captured a video of the first elk – a mature bull – using the crossing. Since then, red foxes and coyotes have also been spotted.
Servheen, who retired from IDFG, hopes this overpass is the first of many.
“We can do this,” he said. “It's doable. And I just hope we can do some catch-up here because we've got lots to do. We have tremendous elk, deer and antelope. We need to start taking care of them.”
ITD plans to start construction on three underpasses in southeastern Idaho next year, and locals in North Idaho recently received funds to transform an old bridge into an overpass.
As the state continues to grow and landscapes change with a warming climate, Servheen said, connecting habitat is only getting more important.
Find reporter Rachel Cohen on X @racheld_cohen
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