By Renee Seidler and Jon Beckmann
Migration is essential to pronghorn. They migrate to find the food, habitat, and resources they need to survive, and this past spring, a band of 200 pronghorn migrated north to Grand Teton National Park (GTNP) in Wyoming to give birth to fawns. With the cold weather now setting in, however, it’s time to migrate with their fawns back to their crucial wintering range—150 kilometer (approximately 93 miles) to the south in the Upper Green River Basin. At the end of this journey—one of the longest ungulate migrations in the contiguous U.S.—the pronghorn will be rewarded with access to woody shrubs for winter forage.
These pronghorn are traveling a route known today as the “Path of the Pronghorn”. As biologists for the Wildlife Conservation Society’s North America Program (WCS), we have been studying these and other pronghorn of western Wyoming for almost a decade. Along with GTNP and Bridger Teton National Forest, WCS worked to bring about the designation of the Path as the first and only federally designated migration corridor in the U.S.
To protect this special corridor, however, we first had to define it by literally following the pronghorn. We did this through the use of Global Positioning System (GPS) radio collars. Employing satellite-tracking technology enables scientists to monitor wildlife movements, understand behavior, collect critical conservation information, and in the case of pronghorn, document their migration patterns without continuous direct observation. Our pronghorn monitoring data have been used by conservationists, land-use planners, and others to ensure that pronghorn persist in a world where they are increasingly being constrained by barriers.
Scientists are able to track the movements of pronghorn with the use of GPS radio collars like the one shown here.
We are currently in the field observing the fall migration. While this migration spectacle will occur over several weeks in the Greater Yellowstone Ecosystem (GYE), each individual animal will average only three days to travel the entire 150 kilometer distance as they hurry south through the difficult terrain and challenging weather conditions—much as pronghorn have done along the Path for 6,000 years. But only more recently have the animals faced the myriad threats of fences, roads, rural sprawl, energy development infrastructure, and other impediments that fragment their habitat and the passages that link them.
Increasingly, pronghorn are encountering barriers that block their migration like the fencing shown here.
Soon, the pronghorn will get some good news as wildlife overpasses (where animals can pass over the highway) and underpasses (where animals can pass under the highway) are being installed on US Highway 191 near Trapper’s Point in western Wyoming. The structures are being built specifically to protect motorists and provide safe passage during migration for pronghorn and other wildlife in the southern GYE. Trapper’s Point has historically been a “bottleneck” problem area for the migrating pronghorn and each year, thousands of animals cross traffic lanes on US Highway 191, creating a perilous situation for humans and wildlife alike.
The Wyoming Department of Transportation has committed $9.7 million in an effort to reduce collisions along Highway 191, increasing both human safety and habitat connectivity for important wildlife populations. Installation of the highway crossing structures began this summer and will continue into 2012. The location of the structures were informed by five years of WCS data from our GPS collars and data from the Wyoming Game and Fish Department that identified crossing points preferred by pronghorn as they migrate across the highway.
Underpass construction on Highway 191
The construction crews have been working hard to install the structures and 13 miles of requisite 8-foot high woven wire fencing on either side of the highway to funnel the animals to the eight safe passage points. The structures and fencing are not complete however, and we as WCS scientists are on the ground anxiously awaiting the returning pronghorn to observe and document their reaction to the fencing, crossing structures and the general appearance of the area. We will observe whether the animals proceed through the underpass and overpass locations or whether the structures in their present form, are avoided altogether. We look forward to sharing our observation in the next installment.
Nearly completed underpass
Dr. Jon Beckmann is an Associate Conservation Scientist in the WCS North America Program. He is the Principle Investigator or Co-PI on several projects in the Greater Yellowstone Ecosystem and in other regions of North America. He is lead author of the book, Safe Passages: Highways, Wildlife, and Habitat Connectivity.
Renee Seidler began working with WCS in 2003 and helped to launch the Wildlife and Energy Development project in the Upper Green River Basin in 2005. She has conducted behavioral and ecological research on coyotes, wolves, moose, pronghorn, small mammals, and birds in Montana, Wyoming, Colorado, New Mexico, and Panama.