Scientists with the Wildlife Conservation Society (WCS) observing the fall migration of pronghorn from Grand Teton National Park to the Upper Green River Basin announced that for the second year, the animals have successfully used the newly constructed overpasses that provide safe passage over U.S. Highway 191 in Trapper's Point, Wyoming. More telling, the scientists report that unlike the first year, the pronghorn showed no hesitation in using the overpass and have apparently adapted to the structure.
The overpass at Trapper's Point is one of eight safe passages constructed by the Wyoming Department of Transportation (WYDOT) along a 13-mile stretch of highway. In addition, eight-foot high barrier fencing was placed along the highway to channel animals to the crossing points. In all, two overpasses and six underpasses have been constructed and accommodate pronghorn, mule deer, moose , elk and other wildlife, and in seasonal drives across the highway, livestock. The two overpass structures were specifically located and designed to address pronghorn migration conservation needs.
Last year, scientists noted that it often took groups of pronghorn several hours to the better part of a day to cross the overpass. The groups would follow their established route, stop at the new fencing, and then spend time moving back and forth, in some cases passed the open overpass several times before finally crossing.
"What a difference a year makes," said WCS Northern Rockies Program Coordinator Jeff Burrell. "While it was great to see pronghorn first using the overpass last year, it was clear that the fences and structures were confusing to them. This year, groups numbering from one to two hundred moved along a new route directly to, and over, the overpass with no delays, demonstrating their comfort with the overpass and the structure's conservation value. The overpass not only reduces mortality but also allows the pronghorn to move with less energy and stress."
Last year's completion and opening of the overpass marked a new era of reduced risk of wildlife/vehicular collisions in the area, and the culmination of years of cooperation among conservationists, government officials, land and transportation planners, and others.
WCS Conservation Scientist Jon Beckmann said, "This was an inspiring project that brought together many groups with many areas of expertise to accomplish a worthy goal that benefits both wildlife and people. Congratulations to WYDOT for committing the resources to this project and seeing it through successfully."
The locations of the structures completed were informed by data collected by WCS, the Wyoming Cooperative Fish and Wildlife Research Unit, and the Wyoming Game and Fish Department, and identified the pronghorn's preferred migration routes and highway crossing points.
WCS Field Biologist and Pronghorn Field Leader Renee Seidler said, "The behavioral research that the WCS is conducting as well as the photo-documentation work that Western Ecosystems, Inc. is doing will help us better understand why these particular crossing structures are such a success and translate this to future wildlife crossing structure projects."
WCS has long studied an approximately 93-mile (150 km) migration of pronghorn between wintering grounds in the Upper Green River Basin and summering grounds in Grand Teton National Park (GTNP)—a migration corridor known as the "Path of the Pronghorn." WCS worked with many partners including Grand Teton National Park and Bridger-Teton National Forest to bring about the designation of the Path as the first and only federally designated migration corridor in the United States.
As part of their research, WCS scientists used GPS tracking collars to collect information over the course of five years on the location and timing of pronghorn movements and impediments to migration such as fences, roadways, pipelines, and other energy development infrastructure.
Using this information, the Wyoming Department of Transportation (WYDOT) was able to locate and build the structures as part of an effort to protect motorists and provide safe passage for migrating pronghorn and other wildlife in the Greater Yellowstone Ecosystem. Trapper's Point has historically been a "bottleneck" problem area for the pronghorn each year, causing thousands of the animals to cross traffic lanes on U.S. Highway 191, and creating a perilous situation for humans and wildlife alike.
Pronghorn are North America's fastest land animals. They numbered an estimated 35 million in the early 19th century. Today, about 700,000 remain and more than half of those live in Wyoming. The animals migrate to find food, mating opportunities, suitable habitat, and other resources they need to survive.
While WCS scientists study pronghorn throughout western Wyoming, those that follow the Path are of particular interest. They travel farther than the others and their continued journeys to and from GTNP ensure that the park's ecosystem remains ecologically whole and that a 6,000 year-old migration remains a part of our national heritage.
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