How to protect Yellowstone's epic migrations

Conservationists, hunters, and policymakers are collaborating to improve conditions for the park’s migrating mammals.

Photograph by Joe Riis, Nat Geo Image Collection
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A band of pronghorn ford the Green River on their way towards Grand Teton National Park.
Photograph by Joe Riis, Nat Geo Image Collection

A new movement is helping animals make epic migrations across the American West by removing some of the barriers humans have thrown up over recent decades.

The Greater Yellowstone Ecosystem, which spans roughly 18 million acres in and around Yellowstone National Park, is home to what are arguably the most impressive mammal migrations outside of Africa. Each year, thousands of elk, pronghorn antelope, and mule deer must make long, arduous journeys across Yellowstone’s rugged landscape in order to reproduce and avoid starvation.

Making these migrations means running a gauntlet of fences, highways, and housing developments. But now, a group of conservationists, hunters, ranchers, and policymakers are coming together to remove these obstacles.

For example, pronghorn antelope, which happen to be the fastest terrestrial mammals in North America, traverse more than 100 miles of treacherous terrain each winter as they migrate from their winter range in Wyoming’s Green River Basin to their summer range in Grand Teton National Park. This epic route is known as the Path of the Pronghorn.

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Hundreds of migrating elk pass through the Spence & Moriarity Wildlife Habitat Management each winter. This protected swatch of land near Dubois, Wyoming was purchased by the state in 1991 to provide migrating animals with a safe haven.

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Swimming through fast-moving rivers is one of the most dangerous natural challenges that pronghorn face. Crossing roads, of course, is much more hazardous.

But, like the migratory routes of the elk, mule deer, and other ungulates that move through the Lower 48, the path of the pronghorn extends across a patchwork of federal, state, and private lands that, in many places, are littered with barbed-wire fences, highways, housing developments, and other man-made obstacles.

A difficult journey

Ten years ago, National Geographic contributing photographer Joe Riis began photographing migrating elk, mule deer, and pronghorn with the goal of sharing their journey with the world.

“It’s been my goal to show the difficulties [migrating ungulates face] but also show the wildness of the middle of America,” Riis says.

Riis hoped that by sharing their journey with the world, he could shed light on the man-made perils they face along the way. One of Riis’ most evocative images, published in the May 2016 issue of National Geographic, was of a pronghorn with its leg caught in a barbed-wire fence.

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The Hoback Basin, nestled between the Wyoming and Gros Ventre Mountain ranges, serves as the summer range for mule deer.

That fence and many others have since been removed or retrofitted thanks to a nascent movement to preserve migratory corridors, inspired in large part by Riis’ photographs. Over the last decade, hunters, conservationists, private landowners, and policymakers have come together to identify and eliminate man-made obstacles from migratory corridors in and around Yellowstone National Park.

Nowhere is this change more evident than along the 12-mile stretch of Highway 191 that sits west of Pinedale, Wyoming. This section of highway, known as Trappers Point, cuts right through the path of the pronghorn. As a result, auto accidents involving pronghorn were once common.

Building bridges

“Trappers Point was a really dangerous place for people and migrating pronghorn,” says Riis. At least 100 pronghorn, mule deer, and other ungulates used to die trying to cross this stretch of highway each year, he says. But in 2012, a series of wildlife crossing bridges were built across the highway to ensure safe passage for the pronghorn. (Read more about how wildlife bridges protect animals—and people.)

Now, Riis says, wildlife collisions are almost nonexistent. “It’s a success that a lot of people are proud of,” he says. “It wasn't one nonprofit, one person, or one agency that did it. It was a combination of the community, the county commissioners, a whole bunch of different nonprofits, the Wyoming Game and Fish Department, and the Wyoming Department of Transportation. They all came together and made it happen.”

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Pronghorn crossing the wildlife bridge at Trappers point, completed in 2012, which was built to allow migrating animals to safely avoid highway 191.

Riis argues that such a success would not have been possible without bipartisanship and cooperation. “These animals’ seasonal journeys span tens, even hundreds of miles. This means that no single government agency, non-profit organization, or landowner can conserve their migrations alone.”

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Pronghorns crossing highway 191 in 2008. Since the wildlife bridge was built in 2012, there are almost zero collisions, which is heralded as a success in the area.

And that means state and federal government must find ways to work with landowners for the benefit of wildlife, says Jim Lyons, who served as the Department of Interior's deputy assistant secretary for land and minerals management under the Obama administration.

“It takes that kind of collaborative work across a landscape to ensure that [migrating ungulates] remain a part of this unique ecosystem,” Lyons says.

Tough road ahead

February 2018, Interior Secretary Ryan Zinke signed a secretarial order to improve habitat quality and preserve migration corridors​ for ungulates such as antelope, elk, and mule deer. The order seeks to foster better collaboration between states and ​private landowners to ensure that “robust big game populations continue to exist,” according to a press release.

The order could help ensure these animals have the means to migrate across the lower 48 states. But hunters and conservationists have expressed doubts that the administration will follow through on its commitment and worry about the prospect of oil development, which has expanded under this administration.

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The Thorofare Plateau lies just outside the southeast corner of Yellowstone National Park. Commonly known as "The Thorofare," it is so-named becuse it serves as the main route for thousands of ungulates and other large animals who traverse it during their annual migrations.

“Secretary Zinke has made a commitment to protect more of these migratory corridors, but at the same time, the department he oversees is leasing portions of those migratory corridors for oil and gas development and mining,” says Lyons, who is now a lecturer at the Yale School of Forestry and Environmental Studies. "I am concerned about the conservation commitments of the current administration."

Hunter and Wyoming field representative for the Theodore Roosevelt Conservation Partnership Nick Dobric says words alone won’t satisfy the sportsmen in his community. He and his group like the policy outlined in the order, he says, "but what we really need now is implementation.”

See more of Joe Riis’s work on his website. He recently published a book titled Yellowstone Migrations.
Editor's note: This story was updated June 20, 2019.