Ancient Pronghorn Path Becomes First U.S. Wildlife Migration Corridor

This seasonal movement of pronghorn antelope, Antilocapra americana, between Grand Teton National Park and the Upper Green River Valley in northwestern Wyoming is the longest remaining migration of any land mammal in the lower 48 states.

"This represents a tremendous conservation victory and demonstrates that by working together we can find solutions to preserve our nation's wildlife heritage," said Dr. Kim Murray Berger, a biologist with the Wildlife Conservation Society who has studied the pronghorn migration since 2003.

Based at New York's Bronx Zoo, the Wildlife Conservation Society is part of a coalition of local, state, and federal agencies, conservation groups, and private citizens that has called for permanent protection of the migration corridor to prevent the animals from going extinct in Grand Teton National Park.

A pronghorn antelope in Wyoming (Photo by Julie Maher courtesy Wildlife Conservation Society)

Archaeological evidence indicates that pronghorn have traveled this same ancient migration route, which is less than 150 yards wide in some places, for at least 6,000 years.

By adopting the amendment to the Bridger-Teton National Forest Land and Resource Management Plan, the agency assures that future activities on Forest Service lands within the corridor will be compatible with the continued successful migration of pronghorn.

The amendment was signed on May 31 by Bridger-Teton National Forest Supervisor Kniffy Hamilton, who said, "With the signing of the amendment, we are pledging to assist the preservation effort of this corridor."

"This migration is an important part of Wyoming's history and we want to do all we can to maintain it," she said.

As the fastest land animal in North America, pronghorns migrate annually across tremendous distances, at speeds of up to 55 miles per hour. During the fall migration, the animals move southward 30 miles a day for three or four straight days. In the spring, the pronghorn move northward at a slower pace, as they follow the receding snowline.

Dr. Joel Berger, senior scientist with the Wildlife Conservation Society’s North America Program, studies pronghorn from his base at the WCS Teton Field Office, with scientists Dr. Kim Murray Berger and Dr. Jon Beckmann. He says natural gas exploration is making pronghorn migration difficult.

"The gas field proliferation in Wyoming has been daunting. In just five years, there has been more than a tenfold increase in traffic in areas where pronghorn winter," he says.

"We've seen up to six animals splattered on the road, all killed by a single vehicle," Berger says. "The habitat is being degraded and fragmented, and animals are starting to avoid areas they formerly relied on to make it through the winter. I understand our nation's need for energy, yet I also know many Americans have made massive commitments to protecting wildlife, and these are often ignored."

The amendment just signed does not protect the entire pronghorn migration - it applies only to 45 miles of the migration corridor located on Forest Service lands. The remaining 30 miles of the migration route occur on private lands and areas managed by the Bureau of Land Management, BLM.

Conservationists hope the BLM will follow the Forest Service and pledge to limit the construction of fences, roads, and natural gas wells that could interfere with the migration.

On private lands, voluntary conservation easements and construction of wildlife-friendly fences can facilitate wildlife movements.

Although pronghorn are not endangered, the population that summers in Grand Teton National Park numbers fewer than 200 animals. Because snow in the park is too deep to allow the animals to survive the harsh winters, obstruction of the migration corridor would result in the local extinction of pronghorn from Grand Teton National Park.

The National Park Service heralded the signing of the amendment as an important step in protecting the biological integrity of the ecosystem.

"We remain concerned about the long-term persistence of this migration corridor because it is a life link for our pronghorn population," said Steve Cain, senior wildlife biologist for Grand Teton National Park, who partnered with the Wildlife Conservation Society on the 2003 migration study. "We would not have pronghorn if the corridor became impassible."

Permanent designation of the entire migration corridor would mark another milestone for the state of Wyoming, which hosts the nation's first national park, Yellowstone established in 1872; the first national forest, the Shoshone established in 1891; and the first national monument, Devil's Tower established in 1906.

Globally, the designation of this wildlife migration corridor is important because long-distance migrations are disappearing, due to habitat loss and construction of roads, subdivisions, and other infrastructure associated with extraction of natural resources and human population growth.

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