This is the second installment of a two-part blog by WCS Scientists Renee Seidler and Jon Beckmann who are reporting from the field at Trapper’s Point, Wyoming.
- Jeff Burrell – © WCS
Pronghorn at Trappers Point, Wyoming
By virtue of six underpasses and two overpasses placed within a 13-mile stretch of Highway 191 at Trapper’s Point, the Wyoming Department of Transportation (WYDOT) is trying to keep motorists and migrating wildlife off a collision course. The structures should be finished in 2012. As Wildlife Conservation Society (WCS) scientists, we’ve taken the opportunity during this fall’s pronghorn migration to observe the animals as they encounter the highway and their reaction to the safe passages in mid- construction.
Since our last entry, we’ve observed over 1,000 migrating pronghorn coming through Trapper’s Point in groups of about 20 animals at a time. We were delighted to see several wearing radio collars. These were animals that we had collared in previous years, had spent this summer in Grand Teton National Park (GTNP), and had traveled the Path of the Pronghorn to get here.
While WCS scientists study pronghorn throughout western Wyoming, those that follow the Path are of particular interest. They have traveled 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.
It didn’t take long to be reminded of the challenges that pronghorn face as we watched them try to cross Highway 191. Eventually, 8-foot high fences will guide the animals to the under- and overpasses. Today, both the fencing and structures are incomplete. The animals are struggling as they have for many years in navigating the highway. The potential for collisions with passing motorists exists and it is easy to see why the structures are important.
- Jeff Burrell – © WCS
After frantically dodging traffic and trying to find openings in ranch fencing (which will be bypassed when the safe passages are complete), many pronghorn eventually crawled under fences despite risking injury.
Pronghorn, understandably, become exceedingly anxious when attempting to cross roads. In 2007, more than 20 pronghorn were killed in a single collision event after being hit by a gas field water-hauler truck on a western Wyoming road. We observed very uneasy behavior in the pronghorn as they approached Highway 191–some even looked both ways before crossing. One group of animals was led by an adult doe that anxiously approached the highway and made several attempts to run across. She turned back when an approaching vehicle took her off guard. The group moved like a school of fish behind her, following her lead, moving to and fro as one.
Other females appeared to have greater confidence in the success of their operation. The group cued off the lead animal and in cases where the female advanced with confidence, the group proceeded with poise, moving single file and successfully crossing the road.
Pronghorn cross Highway 191 in an orderly fashion
The situation was more chaotic to the northwest of Trapper’s Point where the fences were nearly complete and animals were forced to negotiate crossings near construction points. We observed a pronghorn buck attempt to lead his group across the road near the construction site of one of the underpasses as workers hustled about the highway. Eventually, the buck crossed the highway surface at grade, but his group did not follow. On the other side of the highway, it took him almost an hour of intense searching to find the fence opening to freedom. Later that morning, 75 pronghorn were reported caught in the same spot. After being alerted to the issue, Wyoming Game and Fish Department personnel arrived to open gates and help put the animals back on course.
Having penetrated the initial fence line, a group of pronghorn cautiously wait for an opportune time to cross Highway 191 at Trapper’s Point, Wyoming.
We did not anticipate that the pronghorn would use the underpasses—particularly in their current unfinished form. Though they have been shown to use them before, underpasses may not be preferred structures when compared to overpasses, an idea that we will investigate. It is for this reason that the WYDOT plan includes a series of both underpasses (to be used primarily by mule deer, moose, and elk) and overpasses to be used by pronghorn.
- Courtesy Wyoming Department of Transportation
Artist’s rendition of completed overpass crossing Highway 191 at Trapper’s Point, Wyoming.
At present, the Trapper’s Point overpass consists of 30-foot berms built on either side of Highway 191 that will eventually support a connecting structure on which the pronghorn will pass over the highway. Despite other options, some of the pronghorn scaled the berms then descended across 191 and were on their way. This lack of fear for the overpass bodes well for its use once it is complete and the 8-foot high woven wire fence is tied-in and guides pronghorn to the structure.
- Jeff Burrell – © WCS
Pronghorn follow their instinctive route which this year takes them over a partially constructed overpass
Despite the challenges and a few surprises, pronghorn were able to travel along their traditional migration routes. As the construction progresses, the pronghorn come that much closer to safer highway crossings in western Wyoming. Providing safe passages that are amenable to species with differing requirements and instinctual drivers is critical to preventing wildlife-vehicle collisions and the preservation of extraordinary ecological phenomena like long distance migration.
After descending the overpass berm and crossing Highway 191, pronghorn anxiously make their way through a temporary “bottleneck” in the fencing and continue on to their wintering grounds
Many questions remain and we await next year’s migration with great anticipation. Will the pronghorn use the underpass structures as well as the overpasses? How long will it take them to adapt to using these new structures once they are complete? How far will a pronghorn travel along an impermeable fence to find the opening that provides safe access across the highway? Until next year….
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.