Researchers document successful wildlife overpass
Researchers at Utah State University took part in a study to document animal activity at a wildlife overpass in Parleys Canyon. The overpass was designed specifically with mule deer in mind to prevent deer-vehicle collisions in the canyon but also helped many other species of animals safely cross the eight-lane highway.
Nicki Frey, a USU extension wildlife specialist, said the project was highly successful. Frey and other researchers used video footage to monitor mule deer and other animals to see how often they approached the overpass and either crossed it or turned away.
According to this footage, 98% of mule deer and 100% of moose crossed the overpass after approaching it. Over 35 other species including porcupines, weasels, bobcats, squirrels and coyotes also used the overpass.
“To us, that’s very successful because it infers that wildlife see this overpass as part of their environment, not something scary to be worried about,” Frey said. “We had a den of coyotes living right next to it, and they would play around on the overpass, so they were clearly incorporating it into their daily lives.”
Since the overpass targeted prey species, Utah Department of Transportation, or UDOT, engineers and designers kept the overpass open without shrubbery or trees that could conceal a predator.
Frey said UDOT studied animal behavior for several years before building the overpass, identifying high-collision areas and natural crossing patterns. The overpass was designed with these natural behaviors in mind, and a variety of factors like fences helped to organically guide animals to the overpass.
Blake Ledbetter, a research assistant on the project, was surprised by how quickly mule deer incorporated the crossing into their range. He said researchers put six cameras at the crossing, returning every two weeks and reviewing the footage to determine successful versus unsuccessful crossings and identify things like the species, sex and crossing patterns of the animals using the overpass.
“If they’re not using the crossing to get from one way to the other, then they’re going to eventually find their way onto the road, past the fence, where they stand the risk of getting hit by a vehicle,” Ledbetter said. “It’s really important for us to look at these results and say ‘Okay, this was worth the money.’”
Ledbetter believes their research will help the state design crossings that match the needs of different target species. Though the overpass was highly effective for mule deer and moose crossings, elk only successfully used the overpass once, highlighting the need for species-specific design.
Frey said the overpass is not just good for animals. It also makes financial sense.
“This overpass cost $5 million, which sounds like a lot, but $5 million is less money than what all of the deer-car collisions cost a year, so they paid back the cost of that overpass in just a couple of years,” Frey said.
Ledbetter says wildlife-human conflicts are unavoidable, but projects like the overpass keep both humans and animals safer.
“We need to use roadways to get from one place to another. There’s no avoiding that,” Ledbetter said. “It’s extremely important that we adapt with wildlife, not only to help the wildlife out, but it also saves human lives when we implement these crossings and they’re successful.”
According to Frey, research on the overpass helped to increase support and funding for future projects, and both she and Ledbetter expect to see more wildlife overpasses throughout the state in the future.
Frey said the value of these overpasses goes beyond just reducing collisions. They also give smaller species a way to survive.
“We’re always focused on the things that impact us, like deer-car collisions or moose collisions, which are important, but environmentally, it’s also important that porcupines can cross safely and rabbits can cross safely and foxes can cross safely,” Frey said.