Corinna Riginos speaks at the Buffalo Bill Center of the West.

Every hand in the Buffalo Bill Center of the West’s cafeteria shot into the air.

The Nature Conservancy’s Corinna Riginos had just asked how many people in the audience were worried about hitting a deer while driving Wyoming roads.

A Ph.D. biologist, Riginos was presenting as part of the museum’s lunchtime exhibition series of speakers, and addressing one of the most pressing driver safety topics in the West.

In Wyoming alone, Riginos said, the Wyoming Department of Transportation counted over 6,000 instances in which a deer was struck by a vehicle last year. While she credited WYDOT for counting such collisions at all, Riginos called that figure “a pretty dramatic underestimate” due to the difficulty of collecting accurate data.

High Costs

The large number of crashes caused by deer has a major impact on the state.

In addition to killing and wounding many people yearly, WYDOT figures indicate the crashes are a significant economic drain.

Riginos was the principle investigator for a study of the problem published by WYDOT in September 2015.

According to that study, reported deer-vehicle collisions incur an average cost of $11,600 per incident in property damage and medical care for victims.

It doesn’t end there, however. Each deer killed also costs the state roughly $4,000 from lost hunting opportunities and meat, making for a whopping $15,600 average cost per reported crash.

In injuries and vehicle damage alone, Riginos estimates deer collisions cost the state between $24-29 million per year. 

The price of lost tags and dead deer adds another $20-23 million in “wildlife costs,” meaning the total cost of such incidents in Wyoming is between $44-51 million annually.

Deer are far and away the animal most likely to cause crashes, accounting for 87 percent of tabulated wildlife collisions in Riginos’ study.

About 4 percent of the total deer population is struck in any given year, the biologist added, with almost every crash resulting in the death of the animal.

“These kinds of dynamics aren’t good for wildlife and they aren’t good for people,” Riginos said.

A Fragmented West

The problem, in many ways, is one of roads.

Riginos called them “a source of fragmentation of the landscape,” and said deer in particular struggle to adapt to their presence.

Deer are migratory animals that travel hundreds of miles a year, Riginos said, but those ancient pathways have been increasingly impeded by highways.

Major highways such as Interstate 80 actually choke off migration routes entirely, with the deer unwilling to hazard a crossing at all. 

“Beyond some threshold, there are just too many cars to even try,” Riginos said.

For that reason, despite their high speeds and numerous vehicles, those roads generate few collisions annually.

Instead, Riginos said, her study found the most dangerous places featured more moderate traffic levels. She called a stretch of US 30 near Cokeville “the single worst mile in the State of Wyoming [for deer crashes].”

Traffic volume and migration habitat value, her study found, account for a large majority of the differential in the number of deer collisions on a road per year.

Speed limit, cover and other factors are also predictors, but their effects are comparatively small, Riginos found.


While well-intentioned, Riginos said mitigation efforts had yielded, at best, mixed results.

The most popular remedies may not have any effect at all.

Riginos broke mitigation efforts into two categories:  at-grade crossings, where deer and other animals are expected to cross at road level and separated crossings – under or over passes animals can use to cross roads.

At-grade crossing mitigation strategies include efforts to decrease driver error by decreasing speed limits at night, adding warning signs and making them flash. While acknowledging those tactics are “far, far cheaper,” Riginos said. “The majority of these measures simply aren’t very effective.”

Traffic engineers say people quickly habituate to signs and begin to ignore them. 

Speed limit reductions at night are being studied as another possible fix, but may require greater enforcement in large, empty places in order to be effective.

“People don’t slow down unless the road is designed for people to go slower,” Riginos said she’s been told by traffic engineers.

By contrast, few question the effectiveness of separated crossings, which Riginos called “the

 gold standard” of mitigation.

The animal bridges and tunnels reduce crashes by 80-90 percent, studies have found. 

In the last decade, crossings installed near Pinedale have dramatically decreased crashes on that section of US 191. At a cost of $9.7 million to WYDOT, the crossings are expected to pay for themselves with reduced crashes over a dozen years.

Such structures face a number of barriers, including social resistance and high up-front costs.

To achieve crash reduction in the 80-90 percent range, such crossings must include six miles of fencing to funnel the animals to the proper spot. 

Fences can cost up to $1 million per mile to install, leading Riginos to say, “these crossing structures are expensive, let’s be honest about that.”

Despite the investment required, Riginos said the savings from reduced crashes will pay for the structures in high-risk areas over 75 years. 

“Anywhere that has a lot of collision problems is worth mitigating financially,” she said. “It is worth it.”

Riginos said efforts to decrease costs of the crossings could make them more palatable options in the future.

And she credited WYDOT and the Wyoming Game and Fish Department for being “highly engaged in finding solutions” to the issue.

While the problem is a challenging one, Riginos views it as low-hanging fruit in her field. 

Compared to addressing human caused climate change or trying to fight the spread of chronic wasting disease, Riginos said, lowering the number of deer-vehicle collisions was “an easy conservation problem.”

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