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Crossing U.S. Route 20

Major roads are often barriers to wildlife movement. When they cut across the edge of the world’s first national park, it’s an even big concern.

From the northwest corner of Yellowstone National Park, U.S. Route 20 crosses the Continental Divide at Targhee Pass and winds its way south into Idaho, past the mountain streams and waterfalls of Caribou-Targhee National Forest.

Busy highways through natural areas usually spell trouble for wildlife, especially wide-ranging species like grizzly bears, elk and moose.

A mother moose and calf stand near a roadside in the Greater Yellowstone Ecosystem. Photo: Kent Nelson.

As they slice through the landscape, roads decrease available habitat and pose a constant danger to animals trying to cross them. Beyond those obvious dangers, highways also fragment wildlife populations into smaller, isolated sub-populations—a process that decreases genetic diversity and degrades the long-term health of any species.

But U.S. Route 20 is not just any highway. It’s the first major road that animals encounter as they roam west out of the protected lands of the Greater Yellowstone Ecosystem, and it bisects several known migration routes for elk and moose, which cross the highway twice yearly in the spring and fall. Other animals, such as grizzly bears, are also known to cross the highway throughout the year as well.

A grizzly bear is surrounded by a herd of elk in Yellowstone National Park. Photo: Kent Nelson.

In 2015, Idaho Fish and Game, Idaho Transportation Department (ITD) and the Wildlife Conservation Society (WCS) teamed up to release a report, US 20 Island Park Wildlife Collision Study, which stressed the highway’s negative effect on wildlife movement.

Although wildlife-vehicle collisions occur along this entire stretch of road, the report’s authors identified several high-collision areas where wildlife fencing, crossing structures and other efforts could go a long way toward reducing wildlife-vehicle collisions overall.

With that and other studies revealing a clear call for action, several groups—including Y2Y, WCS and the Caribou Targhee National Forest—have come together to develop innovative ways to improve the highway.

Two bull moose near Yellowstone National Park; a pretty picture, but not in a collision. Photo: Kent Nelson.

Our collaborative effort involves identifying wildlife corridors to reduce wildlife-vehicle collisions, as well as determining the most effective structures (such as fencing and over- and underpasses) to serve that purpose, plus an education campaign to convince others of their overall importance.

Providing safe wildlife passage on U.S. Route 20 is a long-term vision. As the number of people visiting Yellowstone National Park and surrounding areas increases every year, so does traffic along this stretch of road.

Taking wildlife crossings into account for any future road upgrades is not only a boon for animals, but for drivers too. If done right, these efforts could serve as a positive example for countless other roadways bisecting ecosystems throughout the Yellowstone to Yukon region and beyond.

A migratory pronghorn in Greater Yellowstone. Photo: Kent Nelson.
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