Conservation & the West Up close

Wildlife crossings seek to reconnect the animal West

The emerging science of road ecology has been tallying the cost of collisions to animal populations and vehicle owners. Now western states are mitigating the danger, a process that new Federal money could accelerate.

A bighorn sheep lies dead by the side of U.S. Highway 85 in western North Dakota (North Dakota Department of Game and Fish)

By Felicity Barringer

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We explore the issues, personalities, and trends that people are talking about around the West.

Roads are built with a purpose: to get people and goods where they need to go. But in places like the American West, roads that connect society often interrupt the migration routes of animal species —like elk, mountain lions, moose, and bighorn sheep — that often date back to the end of the last Ice Age.

More and faster roads inevitably mean more roadkill. When cars hit larger wildlife, it can also lead to human casualties and hefty car repair bills. But a solution to this problem has taken hold around the region: wildlife crossings built under or over roads around the West, from San Antonio, Texas and North Dakota to Interstate 15 in Utah. 

The efforts to save both animals and people have led to a proliferation of road crossings for animals along traditional migration routes and other crucial locations.

The efforts to save both animals and people have led to a proliferation of road crossings for animals along traditional migration routes and other crucial locations. The practice originated in France in the 1950s and quickly spread to the Netherlands, which now is home of the world’s longest wildlife bridge. There are now underpasses in every western state.

An overpass in Beaver, Utah was the first such crossing in this country. It was built over Interstate 15 in 1975. Utah now has about 60 wildlife crossings. Other states were slow to follow its initial example until the 1990’s, when a tunnel, intended for frogs, was built in Davis, California.

The most recent and soon to be the largest wildlife bridge in the country is an $87 million structure being constructed north of Los Angeles in Agoura Hills, California. It will allow mountain lions, foxes, and other wildlife to cross 10 lanes of Highway 101 without encountering a car.

The Wallis Annenberg Crossing in Agoura Hills.

Further north, a 90-foot underpass is being built across California’s Highway 17, which runs between the south San Francisco Bay area and Monterey Bay. 

Congress whetted the appetite of states to construct their own crossings by including $350 million in the 2021 infrastructure act earmarked for this purpose.

Exploring the first wave of road crossings

In 2017, the road ecologist David Theobald led an effort to catalogue the wildlife crossings in the American West, and categorize them by type of structure, the animal species targeted and other details. Since then, such information has remained the province of individual state departments of transportation and a regional tally remains out of reach.

Source: Theobald, DM, V Landau, P Cramer, D Harrison-Atlas, C Monnroy, and J Lewis. 2017. A guide to the Wildlife Crossing Structures Database v1. Unpublished report, Conservation Science Partners, Truckee, CA, USA. May 15, 2017

Road ecology studies seek to make all journeys safer

With highways and animal migration routes intertwined everywhere, a new academic discipline emerged in the first years of the 21st century: road ecology. Developed by a Harvard landscape ecologist, Richard T. T. Forman, the field is described in a 2003 book “Road Ecology: Science and Solutions.” A 2010 abstract in the journal “Environment” carried the headline: “The four-million-mile U.S. road system ties the land together for us, providing unprecedented human mobility, yet it slices nature into pieces. Can the newly emerged science of road ecology provide solutions that lead to a gentler roadprint?” 

The University of California, Davis, has a center devoted to the field. Montana State University’s western transportation institute specializes in road ecology. Montana is a fitting location for the institute, since pressure from that state’s indigenous groups ensured it is home to the most concentrated group of wildlife crossings anywhere, most built in the Flathead Reservation along the 90-mile length of state highway 93. In 2000, the Confederated Salish-Kootenai Tribes conditioned their permission for easements to widen the road on the state’s commitment to protect regional wildlife, asking highway officials to respect their belief that “the road is a visitor and that it should respond to and be respectful of the land and the Spirit of Place.”

Chart showing number of animal crossings by type

In 2005, the Montana Department of Transportation started to construct 29 road crossings for wildlife – mostly underpasses. The amount paid for crossings, over and above construction costs not associated with wildlife, was calculated at $21.4 million. These crossings, one of the densest collections of such structures in the world, got wide attention, along with videos of the deer, black bear, coyotes, foxes, and other critters using them. The state now has 120 wildlife accommodations — mostly underpasses — on its roads. 

Patricia Cramer could be called the high priestess of road ecology. For two decades, Cramer, ​​director of the Wildlife Connectivity Institute, has been advising state transportation departments, from Colorado to Wyoming to Florida, about where and how to build wildlife crossings. “There was a sporadic creation of crossings in the early years” of the century, she said. Florida’s need to protect its native panther made it an early leader.

With vivid images, wildlife cameras raise awareness

Deer crossing a new overpass on I-80 at Parley’s Canyon in 2020.   Utah Department of Wildlife Resources via Facebook

The big leap forward, she said, came in 2004 when a company called Reconyx developed wildlife cameras that produce photos and videos of the animals using the crossings. “Those cameras are motion-triggered; they could take 10 pictures per trigger. That changed the game; we could show the engineers, ‘Yes, they do work,’” Cramer said. She credits the Federal Highway Administration for pushing state transportation agencies to build crossings — for all animals, migratory or not — when widening or repairing roads. 

From driver safety to threats to individual species, the impetus for each state’s experience with wildlife crossings has been a little different.

From driver safety to threats to individual species, the impetus for each state’s experience with wildlife crossings has been a little different. In Colorado, the issue came to a head in the early 2000s as federal regulators, seeking to protect endangered species like lynx and boreal toads, pushed for them. “Lynx was the big driving force behind the crossing phenomenon in Colorado,” said Jeff Peterson, wildlife program manager at Colorado’s Department of Transportation.

Patricia Cramer

A few years later, in 2006, he said, they started collecting data on roadkill. “A lot more animals were being hit than we ever thought,” he said. “We got a little concerned about that, not because of the animals’ sake, sadly, but because of the safety issue.” Now the state has 29 structures built specifically for wildlife, including three bridges. The process, he said, “has accelerated a lot….We’re reducing the animal-vehicle collisions by 80-90 percent in most cases when we put a crossing in.” He added, “now we’re really fired up because we’re going to start competing for those [infrastructure] grants.”

In New Mexico, in the 10 years ending in 2018, the annual average of collisions with animals like deer, pronghorn, elk, and other large mammals was just under 1,000, according to Ryan Darr, assistant information chief of the state Department of Game & Fish. He noted that, to steer the wildlife into crossings over or under the highways, eight-foot fences are built along the route. Research in western states, he said, shows large wildlife can take a few years to adapt to using crossings, but eventually make the transition, cutting collisions with vehicles up to 95 percent. Earlier this year New Mexico issued a plan describing 11 priority spots needing road crossings.

Arizona Department of Fish and Game

Since 2005, the Regional Transportation Authority in Arizon’s Pima County has earmarked excise tax revenues for road improvements, with $45 million originally set aside for critical wildlife linkages. Local jurisdictions assess their need for crossings and apply to the authority to cover their costs

A quarter century ago, even before Montana’s embrace of wildlife crossings, the Canadian government began to build its internationally admired crossings of the Trans-Canada Highway in Banff National Park. There are now six overpasses and 38 underpasses; in 2017, collisions with wildlife had been reduced by an estimated 80 per cent.

In Canada’s Banff National Park, collisions with wildlife had been reduced by an estimated 80 per cent.

There perhaps is no greater barrier to western wildlife than Interstate 80, particularly in Wyoming but also in Utah and Nevada. In 2013, Nevada installed a crossing over the highway.

Five years later, Utah built its own I-80 crossing and distributed videos of the animals using it. 

In Wyoming, conservationists have long advocated for solutions to help wildlife whose migrations are blocked by the interstate. 

A 2016 federal-state study showing the frequency of vehicle collisions with deer focused attention on the problem; the state’s first crossing over Interstate 80 — a highway built about 50 years ago — was just announced. The $10 million in state funds designated for this and two other projects related to wildlife controls will be matched by federal infrastructure funds.

And Washington State recently completed its own overpass vaulting a superhighway – in this case, Interstate 90 in the Cascades, about nine miles east of Snoqualmie Pass. Until the Los Angeles-area overpass is completed, this will be the nation’s largest wildlife overpass. 

Washington Department of Transportation

But while saving big game from peril might grab people’s imaginations, road crossings also serve less charismatic creatures, such as Davis’ frog tunnel in the 1990’s; Colorado is now contemplating tarantula tunnels on roads in its southeastern corner. “That all started because of the tarantula migration–mating movement” this time of year, said Mr. Peterson of the state transportation department. 

Tarantulas have made the area a tourist attraction. People stop their cars on truck-filled roads between Pueblo and La Junta to take pictures. Pueblo’s population, Peterson said, “is growing more and more and the situation was getting worse and worse.” But for now the problem is simply being assessed; no decisions have yet been made. “…We have not committed anything – no funds, no plans,” he said. “We’re just setting up cameras.”


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Felicity Barringer

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A national environmental correspondent during the last decade of her 28 years at The New York Times, Felicity provided an in-depth look at the adoption of AB 32, California’s landmark climate-change bill after covering state’s carbon reduction policies. MORE »

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Geoff McGhee specializes in interactive data visualization and multimedia storytelling. He is a veteran of the multimedia and infographics staffs at The New York Times, Le Monde and MORE »

Xavier Martinez

Xavier Martinez

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Xavier graduated from Stanford in 2023 with a degree in economics and is currently a master’s student in Stanford’s journalism program. He has written about the high phone call costs faced by U.S. inmates, temporary Mexican workers’ interactions with the labor market and the efficacy of government healthcare assistance programs. A lifelong lover of charts and maps, he enjoys combining data journalism with narrative-style reporting. 

‘& the West’ is published by the Bill Lane Center for the American West at Stanford University, which is dedicated to research, teaching, and journalism about the past, present, and future of the North American West.

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