Avoiding Wildlife-Vehicle Collisions

Nothing ruins a summer picnic outing like fresh deer meat on the grill – of your car.

Then again, the best available science says that’s the best place for a deer to go if it’s caught in your headlights. It turns out humans misunderstand deer behavior almost as badly as deer fail to figure out cars.

“People assume deer will learn to look both ways, and the dumb ones will be selected out of the population,” said Sandra Jacobson, a wildlife biologist with the U.S. Forest Service’s Pacific Southwest Research Station in Davis, California. “That’s not going to happen. You think surely they will figure out they have to move, yet sometimes they make the completely incorrect response. That’s because they have sensory perceptions that make that impossible to happen.”

The first deer that Jacobson hit crossed safely in front of her, then turned around and jumped over the hood of her car. It was one of the average 1.2 million wildlife collisions motorists report every year. Of those, 2,600 people get injured and 200 get killed. The wildlife typically does not survive.

Given their job descriptions and work sites, it’s not surprising that Forest Service workers make up a significant number of those accidents. Jacobson said wildlife collisions typically form the No. 1 or 2 cause of accidents and property damage involving Forest Service personnel every year. So she decided to do something about it.

The result is a video aptly titled “Avoiding Wildlife-Vehicle Collisions.” It won a bronze Telly Award in 2013, and has been distributed in seven foreign countries.

“Sometimes there’s a lot of misinformation out there – that’s how you get the idea that a deer whistle on your vehicle is going to be effective,” said Lisa Outka-Perkins, project leader at the Forest Service’s Missoula Technology and Development Center. “When I first got the project, I was thinking, how are you supposed to avoid that? I couldn’t believe how much you could do as person to keep awareness and reduce your potential for collisions.”


Start by literally looking at the problem. Deer and people see things very differently.

Humans have predator eyes. They are placed facing the same way, which provides depth perception and helps gauge direction and speed – important factors when planning a chase. Unfortunately, since we evolved out of the full-time predator gig, we’ve let some capabilities slide. Low-light acuity – our ability to see in dawn or dusk – has gone especially lame.

Deer have prey vision. Their widely spaced eyes are great for detecting motion across a wide field of view, which serves as a sort of alarm trigger for new threats moving into range. Unfortunately, poor depth perception makes them lousy at judging distance. So a car coming head-on appears to get bigger, but not necessarily closer.

Deer also have great low-light acuity. Those glowing eyes you see in the dark are because the backs of their eyeballs reflect incoming light, which bounces off the front of the eyeball and back to the optic sensors – effectively amplifying what little light is available.

Except when the light comes from car headlamps, which overdrives the amplifier. Along a roadside, good night vision becomes a liability instead of an asset.

Our job as drivers is to get from home to work or play, and back again. A deer’s job is to eat and not be eaten. Because cars don’t hunt deer, deer don’t consider them predatory threats. So a road is just an obstacle between them and their next meal, with a random chance of sudden death.

Since deer can’t change their optical design and won’t give up eating, Jacobson looked for ways humans might adapt to the problem. She found several useful ideas.

The most common site for wildlife collisions is a two-lane road with a 55 mph or greater speed limit. Deer typically avoid larger freeways, and slower speeds make it easier to see and avoid collisions.

The best possible human response is to build under- or overpasses into these roads, such as the system now protecting U.S. Highway 93 north of Missoula. Those have reduced deer collisions almost to zero. But they’re also expensive and hard to retrofit into existing roads.

Digging deeper into the statistics, Jacobson found that most accidents occur at dusk and dawn, when wildlife is most active and human eyes are most compromised. One simple solution is to avoid driving at those times. That’s not going to work for morning and evening commutes, of course. But forewarned is forearmed.

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The next thing she found was that deer tend to cross at specific places – small bridges in particular. That’s because they’re moving along favorite routes with good cover, like stream beds, and have to cross the road where they can’t get through a small culvert or low bridge. Commuters who remember those places can be extra vigilant when passing.


Then there’s actually hitting a deer. The research found two surprising ideas.

“What kills most people is the wreck after avoiding a deer than hitting the deer,” Jacobson said. “Those things are way worse statistically than if you hit the deer."

That’s because the likelihood of a high-speed evasive maneuver going wrong and ending in tragedy is much higher than whatever damage a struck deer could do to the front of your car. You will likely survive that impact, whereas the chances of walking away from a rollover or head-on with oncoming traffic are much worse. Better to limit the incident to the initial parties involved rather than turn your pas-de-deux into a square dance of disaster.

The second idea is just as counterintuitive: Apply the brakes right up to the point of impact – then let go. Braking pushes the front of the car down. That turns your hood into a ramp leading straight to your windshield. Letting off the brakes at the last second raises the grill.

“That’s particularly important when you’re dealing with larger animals, like elk or moose,” Jacobson said. “When a passenger vehicle hits a moose, it knocks the legs out and the moose comes through the passenger cabin. Your chances of dying with a moose collision are considerably higher because of that.”

The video runs through the way deer see the world, the risk factors for collisions, advice for handling collision situations and what to do after an accident. Outka-Perkins said formatting the information as a documentary fits the way people teach themselves now.

“We wanted to introduce more science into the discussion, and there just wasn’t anything on the market,” Outka-Perkins said. “There were a lot of studies on deterrence, like deer whistles or reflectors, and they were shown to be ineffective. It’s better to have good situational awareness. Now, I’m looking where I am supposed to look, and that’s where they are.”

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