Wilderness crossings, fences likely to reduce road fatalities by 75% on S. Hwy 89 | Ecological
For years, mule deer crossing South Highway 89 in the winter often met a horrendous end, getting crunched by cars traveling the highway between Jackson and Hobuck.
In January 2017, when heavy snow drove ungulates from higher elevations to lower developed areas, the problem was so severe that the Wyoming Department of Transportation told the Jackson Hole Daily that its workers were removing one road-killed deer per day from the highway. . But now, five years later, numbers compiled by University of Montana researchers show that 8-foot-tall wire fencing and underpasses for wildlife can reduce the number of deer killed by as much as 75%.
“At this point, it’s clear that collisions across the entire stretch between Hobuck and Jackson have decreased,” said Hannah Specht, Ph.D. research fellow at the University of Montana in Missoula. Specht is working with WYDOT to oversee the benefits of fences and underpasses.
A total of 14 miles of 8-foot fencing — 7 miles on both sides of the highway — and six underpasses for wildlife and intersections are planned along the Highway 89 South corridor, said Bob Hammond, WYDOT resident engineer. The final holes in the fence are scheduled to be filled this fall as WYDOT widens Highway 89 north of the Hobuck interchange, Hammond said. But even with the fence partially complete, Specht’s research shows a significant reduction in wildlife-vehicle collisions in the area.
Looking at data from the winter of 2014 to 2019, an average of 21 animals were killed each year on the section of highway that is now fenced off. After some fencing and underpasses were completed in the spring, summer and fall of 2019, the following winter, the number of animals killed at the site dropped to five, a quarter of the normal average. That’s according to data from WYDOT and the Jackson Hole Wildlife Foundation. The following year, the decline continued, with only five animals meeting their deaths in front of icy bumpers, which is 76.64% less than the winter average from 2014 to 2019.
“What we can say is that the number of collisions has clearly decreased,” Specht said. “The most obvious predictor is the fence.”
Renee Seidler, executive director of the Jackson Hole Wildlife Foundation, said it was a success.
“WYDOT is only halfway done with this project and the mitigation they’re doing,” she said. “But the four miles or so where mitigation has been in place for several years, it seems to be working.”
Hitting a deer or other ungulate is dangerous not only for the animal. In a 2008 Federal Highway Administration report, the average cost of hitting a deer was $8,388, including vehicle damage, injuries, fatalities, towing, carcass removal and the monetary value of removing the animal from the wild. The cost of shooting the moose was $18,561. Estimated cost of shooting a moose? 30,773 US dollars.
Specht’s preliminary analysis was detailed in a recently released report on wildlife-vehicle collisions by the Jackson Hole Wildlife Foundation, which covered data on wildlife-vehicle collisions collected from May 2019 to April 2021 by WYDOT, the Department of Game and Fish of Wyoming and citizen scientists working with the Wildlife Foundation.
That report found that the three-year average number of wildlife-vehicle collisions in southern Teton County dropped to about 217 animals per year between 2019 and 2021. Grand Titan National Park maintains its own data and was not included in the report. The 217 animals recorded over this three-year period are below the record set between 2016 and 2018, when an average of 274 animals were killed by motor vehicles per year.
As of 2012, the vast majority of animals reported killed by vehicles are ungulates, with 67% of reported collisions involving deer, followed by moose (16%), elk (7%) and a host of other small animals accounting for approx. 1%. These species include coyotes, porcupine, red fox, striped skunk, and white-tailed deer. While Highway 22, which connects Jackson and Wilson and spans Teton Pass, has been the most dangerous for elk, Highway 89 South has been the preferred killer of elk and deer — at least in recent years.
But aside from the fence and underpass project on Highway 89 South, wildlife researchers and officials aren’t sure exactly why vehicle strikes have declined across the county over the past three years.
“These raw numbers don’t really tell us what’s going on in the big picture,” Seidler said.
That’s in part, Seidler said, because Teton County’s sample size is relatively small. This makes statistical inferences about causality difficult. As a result, wildlife officials are wondering why the number of wildlife-vehicle collisions in general is on the decline. So did wildlife watchers, who asked the News&Guide if cars have killed so many animals in Teton County that there are fewer animals left for drivers.
Ali Kurtmanch, a wildlife biologist with the Wyoming Department of Game and Fish Resources, said that’s likely not the case.
“The population size hasn’t changed much in the short term,” Courtmanch said, although she acknowledged that Jackson’s elk herd has declined over the past 20 years.
Instead of hypothesizing fewer animals and fewer collisions, Seidler and Courtemanch, who were involved in the study, hypothesized another hypothesis based on previous research by Karinna Riginas, director of science for the Wyoming Department of Conservation.
Two Jackson-area wildlife biologists said traffic can reach a threshold that prevents animals from crossing the road, a “barrier effect.” Riginas’ research found that in Wyoming, vehicle collisions with wildlife tend to decrease when there are more than 15,000 vehicles per day on a given stretch of road.
“At a certain level of traffic, the road becomes almost a barrier that animals don’t even try to cross,” Kurtmanch said. “In a way it’s good if it means they don’t get hit. But it’s bad when they need to get to food, water, or some other resource, and they can’t do that.”
But it is unclear whether the barrier effect is behind the recent drop. The Wildlife Foundation’s report did not specifically examine the issue, and the number of vehicles at Highway 22 and Moose Wilson Road did not increase, according to the 2022 city-county performance report.
Average weekday summer traffic has increased from about 14,000 vehicles per day in 2016 to 16,000 vehicles per day in 2021 on North Highway 89, which runs through Grand Teton National Park. But the parkway was not included in the wildlife-car collision report. And since 2016, summer traffic on Highways 22 and 390 has hovered around 22,000 vehicles per day and 15,000 vehicles per day, respectively.
But for the people behind the wildlife-vehicle collision report, one conclusion goes beyond conjecture: that the fence and underpasses along Highway 89 South are working.
Specht can’t say for certain that the fence has reduced the number of wildlife-vehicle collisions in the area. But she said she looked at the number of animals and the speed of traffic along the highway as possible predictors of the decline, and the data was too noisy to link the change.
Fences and underpasses, Specht said, are “the clearest variable explanation” for the decline.
Areas north and south of the fence have also seen a decrease in wildlife-vehicle collisions, but Specht couldn’t say why: “We just think of it as a change in the system.”
But the University of Montana researcher said she can “comfortably” say the collisions are happening along South Highway 89, likely because of the section with guardrails and underpasses.
Hammond, WYDOT’s resident engineer, said that’s a recipe for more of the same.
“The best tool we have is wildlife crossings and fences,” Hammond said. “Therefore, on the future project on [Highway] 22, we plan to do the same: crossings and fencing for wildlife.’
To date, Hammond estimates the transportation department has spent $10 million to $12 million on the guardrail and underpass project along South Highway 89, which is part of a larger $100 million widening. And in the summer of 2023, WYDOT plans to begin rehabilitating the Snake River Bridge and upgrading the intersections of Highways 22 and 390, installing a series of wildlife crossings in the area.
“We’re optimistic that once the Snake River Bridge reconstruction project gets underway, we’ll also see a decrease in wildlife encounters in this moose-heavy hotspot,” Seidler said.
In recent years, when moose have been hit by cars in the area, residents have mourned publicly, laying flowers on the animals’ carcasses and putting up hand-painted signs urging drivers to slow down and protect the West Bank’s beloved ungulates.
“The best tool we have is wildlife crossings and fences.” — Bob Hammond, Wydot Engineer