The state Transportation Department is continuing its work on the I-17 Willard Springs Wildlife Overpass project south of Flagstaff. It’ll result in a bridge above the freeway allowing animals to safely cross.
The money to build it comes from a federal pilot program to build wildlife crossings across the country. Part of the goal is to reduce the number of animals who are hit and injured or killed by vehicles.
Nicole Walker has long been interested in this issue and wrote a piece about it for a recent edition of Arizona Highways Magazine.
Walker teaches creative writing at Northern Arizona University and serves as writer-in-residence for the Center for Ecosystem Science and Society there. The Show spoke with her earlier about this and started with what first got her thinking about this.
Full conversation
NICOLE WALKER: I feel like I’ve always been counting the number of animals, sadly, hit by cars on the side of the road. It’s omnipresent, and I’ve lived in a number of states, particularly in the West — in Oregon and Utah and Arizona. And it becomes just part of the scenery sometimes, unfortunately. I feel like when I do take notice, I’m at least serving the animal to some degree to say, "Hey, I’m sorry that this happened to you, and I’m sorry that you’ve passed this way." I’ve wondered what can be done to mitigate this pretty prevalent problem.
MARK BRODIE: One of the things that a lot of states, including Arizona, seem to be doing is trying to create ways for animals to cross roadways, specifically highways, I think, in many cases, overpasses or other trails in ways that animals can cross freeways or roads to get to where they need to go without getting hit by cars. What you found was pretty interesting about how that’s happening here.
NICOLE WALKER: Absolutely. So, I did a lot of research, and this project has been ongoing for many years. You know, the highway that goes from Kingman to Las Vegas was one of the early ones, and this one helps bighorn sheep cross. That seems tremendously, you know, these creatures are pretty rare, and to find a way to help them survive is incredible.
This process didn’t start in Arizona, although Arizona was an early adopter. But I’m originally from Salt Lake City, Utah, and I drive from Flagstaff to Salt Lake a lot. One of the first wildlife crossings was across I-15. But driving up and down these many years, I didn’t even know it. And so once I learned that this wildlife overpass was being constructed over I-17, I became more and more fascinated and went deep into research about how these bridges work, how many there are in the state and across the country and even internationally. And then I learned, too, there’s culverts that go under the roads, which are really great for bears and ocelots and beavers and all kinds of smaller creatures.
MARK BRODIE: How successful are these in terms of trying to cut down on the number of animals killed? I mean, obviously, we can never tell how many animals are not killed, right? But have states and state officials seen a reduction since some of these overpasses and culverts have gone into effect?
NICOLE WALKER: Yeah, many researchers have found that some of these wildlife crossings have brought the number of automobile interactions from about 400 a year in some spots to zero. As I write in the article, over 2 billion animals are killed each year — 335 million in the United States alone — every year with automobile collisions. And so what they found is that it takes a minute, for example, elk to learn how to use the wildlife overpasses, but the number of interactions with vehicles reduces about 40% every year until it gets to a relatively low amount for that area.
MARK BRODIE: So how does it work? I mean, if you build one of these crossings, obviously, animals are not going to be able to read the signs that you post. So how do they learn that this crossing is the way to get where they need to be?
NICOLE WALKER: That was one of the most fascinating parts of the research, I thought, was figuring out how do animals figure out where to cross? Where should I go? There are no signs, there are no stoplights. So what they use is some fences that steer the animals this direction, and they sort of gather them up and entice them to go these directions. There’s fences, of course, across the bridge itself, and then they try to replicate the vegetation across the bridge that would induce them to come across as well. And so a combination of natural effects like vegetation and these man-made devices to help steer the animals that way is really quite fascinating that it works and that it works so well.
MARK BRODIE: Does it seem to work equally well for all different species of animals? Are some sort of picking up on it more quickly?
NICOLE WALKER: It really does seem to work for all animals. The culverts, bears, and wolves and coyotes might use primarily. But the bridges themselves, I think they feel a little bit safer crossing because they can see further, and they cross readily for most creatures.
One of the most interesting things I learned was that pronghorn ... are very shy about crossing highways, which is good in some ways because they’re not getting in collisions with automobiles as often. But one of the problems is that then they sequester themselves in these smaller areas, which leads to inbreeding. And so even pronghorn ... who are shy about crossing highways, are much more likely to use these wildlife bridges to cross. And this is great for their species in general.
MARK BRODIE: How do wildlife officials decide where they’re going to put these crossings?
NICOLE WALKER: So they do years of investigations. Jeff Gagnon, who works for the Arizona {Game and Fish,) he told me a lot about the process of how they figured out how to do this particular wildlife crossing. And the process began in the mid-aughts, 2007 or something. And so they study and they tag elk in particular, right? I think the I-17 corridor is primarily to reduce the number of elk that are hit. They collar the elk and then they study their habits and their behaviors and figure out where are they most likely trying to cross, where are the most accidents happening, how can we, again, where should the fencing go that sort of steers them across that corridor?
And so it’s not an easy process to figure out, and they’re not just guessing. They’re definitely doing tons of years of studies to figure out how many and how best to find the space, the spot exactly where they should build this bridge.
MARK BRODIE: Right. And I would imagine that’s pretty important because these crossings are not free to build. They take a lot of money. And in a time when, for example, the state of Arizona has a lot of competing factors for a not unlimited amount of money, you got to get that right.
NICOLE WALKER: Absolutely. And also in getting it right, you think about what this Arizona might have looked like before it was bisected and transected by highways. And animals had natural paths that they took that they’re, I’m sure you’ve been on hikes before when you’ve seen these wildlife trails.
One of the ways I think they also try to figure out where to put these crossings is to track what those natural pathways look like. And that also gives them a lot of confidence in the place that they put these bridges. It’s definitely expensive, but it’s also very expensive to take care of these automobiles that get in these accidents and to manage wildlife in other ways that is less — I’ll put it — less hopeful.
MARK BRODIE: Nicole Walker teaches creative writing at Northern Arizona University and is the writer-in-residence for the Center for Ecosystem Science and Society there. We were talking about a piece she wrote for Arizona Highways Magazine, and you are listening to The Show.
EDITOR'S NOTE: This story was updated to clarify that pronghorns are a distinct species.
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