Iowa researchers look to ID, minimize ‘hot spots’ of vehicle-wildlife collisions

Everyone is familiar with the classic “deer in the headlights,” but what about turtles on the tarmac?

For centuries, Iowa’s turtles have relied on their shells to keep them safe by providing built-in camouflage and acting as armor against the many dangers of the natural world. It’s an adaptive feature that has worked for eons, but it never stood a chance against the mechanical beast.

“With turtles, their defense mechanism when they perceive a threat is not to scurry away like a squirrel would. It’s to pull into their shells and stay still,” said Brock Struecker, protected species biologist with the Iowa Department of Transportation. “And that doesn’t work so well when there’s a car barreling toward you.”

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The results of such collisions have become common along Iowa roads, particularly during nesting periods in late spring and early summer: Crushed shells, sanguine smears and for many drivers, a guilty conscience.

The scene speaks to a growing issue in Iowa and one that’s affecting more than just turtles: An increase in wildlife-vehicle collisions resulting in animal death, human injury and costly property damage.

Iowa State University researchers — in collaboration with the Iowa DOT — are looking to address that issue by pinpointing “hot spots” where vehicle-wildlife collisions happen most frequently and identifying potential infrastructure solutions.

To identify those problem areas, researchers are examining variables such as road width, traffic counts and speed limits to compare alongside a species distribution model showing where different animals typically live and travel within Iowa.

Researchers can also use citizen-submit reports of areas with unusually high instances of roadkill to build out their findings.

Work on the project began last year using federal funds provided to states for transportation research and will continue through the summer of 2027. Once complete, Struecker said the results will be integrated into the DOT project review process for future road improvements.

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Preventing collisions has environmental, economic benefits

The state of Iowa has approximately 115,000 miles of public roadways to accommodate the regular movements of the more than 4.6 million vehicles registered within the state and the millions more drivers that visit each year.

That infrastructure is necessary and useful, Struecker said, but it can also be harmful to the state’s non-human residents due the risk of direct mortality from vehicle collisions, fragmentation of key habitat and barriers to movement that result in isolated populations.

And those risks can spell trouble for the average Iowa driver, too: the Federal Highway Administration estimates that, each year, there are anywhere from 1 million to 2 million collisions between vehicles and large mammals nationwide.

Those crashes result in thousands of injuries, hundreds of deaths and millions of dollars in vehicular repairs and medical treatment, and that doesn’t even begin to account for the smaller collisions that occur daily between vehicles and smaller creatures like songbirds, rodents and reptiles.

“We have a lot of instances where reptiles are crossing the road to get from one wetland to another and they just get smoked by a car,” said Paul Frese, wildlife diversity specialist with the Iowa Department of Natural Resources. “We always think about deer getting hit on the road, and that’s of course a huge issue. But the smaller guys definitely get those challenges, as well.”

By identifying where those collisions are most common, Struecker said it’s possible to reduce their frequency through infrastructure interventions such as additional fencing, increased signage or manmade wildlife crossings like the one found beneath Highway 100 in Cedar Rapids.

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When the highway was extended in 2014, Iowa DOT staff installed a box culvert near Xavier High School that stretched beneath the busy roadway to allow safe passage between adjacent ponds for deer and other wildlife — including the Blanding’s turtle, a threatened species in Iowa.

Blanding’s turtles — recognizable by their bright yellow necks — have experienced species decline in recent decades due to habitat loss that occurred in tandem with the near elimination of Iowa’s original wetlands.

The addition of a dedicated wildlife underpass beneath Highway 100 helped mitigate the potential for additional habitat fragmentation by allowing the semi-aquatic reptiles the means of traversing the area without having to cross the roadway.

Study will focus on at-risk species, ID solutions

Over the course of their research, ISU researchers will investigate the feasibility and design of such underpasses and other wildlife-friendly crossings to learn more about which could be most useful in Iowa.

In doing so, Struecker said the team will direct particular attention to sites where those collisions involve species of greatest conservation need that were previously identified in the state’s Wildlife Action Plan.

Given Iowa’s general topography, Struecker said wildlife underpasses like the one in Cedar Rapids are typically more feasible — and more effective — than wildlife overpasses or wildlife bridges found in the western U.S.

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The overall study will examine a wide variety of potential solutions, however, and offer roadway mitigation plans for 10 of the identified collision hot spots to exemplify what future improvements might look like.

The final report also will create a geospatial map of current and predicted future collision sites to help prioritize future sites for potential mitigation work, as well as a proposed monitoring plan for evaluating the efficacy of those interventions.

At times, collision mitigation could be looped into the DOT’s more routine road improvement calendar. Where funding is available, however, high collision counts could call for a stand-alone project.

“The general idea of wildlife crossings and evaluating those (alongside) motor safety has gotten a lot of steam” in the last few years, Struecker said. “We’re still in the middle of this and we have a lot of work to do, but we’re hopeful we’ll get some tangible results.”

Comments: grace.nieland@thegazette.com