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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

Deer 'raise the white flag' as a warning. Plywood cutouts of flagging deer were set on roadsides to scare away deer, to no avail. © Stephen J. Lang
Deer 'raise the white flag' as a warning. Plywood cutouts of flagging deer were set on roadsides to scare away deer, to no avail. © Stephen J. Lang

October 2004

Deer in the headlights

Split-second actions can help you avoid and survive highway collisions with deer.

David L. Sperling


Drive to survive | Testing the deterrents
How deer deterrents stack up

On a crisp, blustery day just before Halloween last year, a small group gathered on a rise overlooking Governor Nelson State Park near the shores of Lake Mendota in Dane County. The commanding view of grasslands, the nearby County M highway, surrounding farm fields, open spaces and country homes was a pastoral scene for a get-together, but this was no picnic. Speakers dressed in warden gray, State Patrol blue and business suits held a press conference urging motorists to drive defensively, stay alert and watch out for deer as the fall rut and the annual peak in deer-vehicle crashes approached.

There was good reason for the warning. Last year proved the deadliest on record in Wisconsin with 13 fatalities, more than 800 injuries and almost 22,000 reported collisions between cars and deer. As both the deer herd and the number of miles driven in Wisconsin climb, the odds of seeing deer crossing roads also grows. Avoiding serious crashes means practicing better defensive driving skills.

"Deer are creatures of habit and they are driven by strong natural forces," said DNR Wildlife Biologist Michelle Windsor. "During the rut that starts in October and peaks out in the first two weeks of November, the deer are looking for mates, they are looking for food and they are much more active."

Statistics compiled by the Wisconsin Department of Transportation bear out those observations. Forty percent of the deer-vehicle crashes occur from mid-October through November. A surprising number of injuries also occur in May and June when pregnant does chase off their young from the previous year and start dropping spring fawns. Groups of wandering, inexperienced deer are more likely to feed and walk slowly along roadsides, oblivious to the dangers of oncoming vehicles.

On the human side of the equation, motorcyclists are especially vulnerable to serious injury in a deer collision. In 2002 only two percent of the cars and 1.3 percent of the utility trucks crashing into deer resulted in serious human injury or a fatality, but 75 percent of the motorcycle-deer crashes resulted in serious injury or death to the cyclist.

Drive to survive

Avoiding and surviving deer collisions is a mixture of luck, anticipation and preparation. The State Patrol, insurance companies and the American Automobile Association (AAA) offered tips for minimizing the occurrence of collisions and the damage they cause:

  • Stay aware and alert – That's the advice given by Dave Collins, Superintendent of the Wisconsin State Patrol. Deer are more active in fall. They move between resting and feeding areas at dawn and dusk when it is hard to see, and they blend into the landscape. Crash reports verify deer accidents are most likely to occur between 5-10 p.m. in fall and early winter; 8 p.m. to midnight in spring through summer.

  • Slow down, heed road signs, and drive defensively – Roads that cut between forested patches, roadside brush, openings and valleys in farm fields form natural paths for deer. Road segments with histories of crashes are often marked with yellow deer crossing signs. Slow down to give yourself more time to react in these areas. Allow more space between vehicles. Wear safety belts and make sure all your passengers are buckled in.

  • Watch for deer sign – Collins added that "reading" the landscape and using your peripheral vision to watch for reflections in deer's eyes or roadside movement can give you an early warning of nearby deer activity. If you have passengers, have them scan the road edge as well. If you see one deer, slow down. Deer often travel in groups: where one deer crosses the road, others will follow. Watch the deer and the roadside; slow down as best you can; and alert other vehicles with your lights and horn, which will also prompt the deer to keep moving or head back into the brush.

  • Keep your car/truck in good repair – Check that your tires and brakes are in good condition and be sure headlights are properly aimed. Trucks and SUVs ride higher, so check that headlights hit the roadway evenly and don't shine in the eyes of oncoming traffic.

  • Remain in your lane – "In an emergency situation, this can be the hardest piece of advice to practice, but it definitely saves lives," said Ted Gamble, president of AAA Wisconsin. Hit your brakes, hit your horn and hit the deer if you must, but don't swerve. The chances of serious injury are much greater when cars swerve to avoid a deer, Gamble said. Swerving into traffic and hitting an incoming vehicle, swerving to the side and hitting a fixed object, or leaving the road are all more dangerous than hitting a deer. Deer can accelerate from 0 to 30 mph in 1.5 seconds; if you continue in a straight line and brake, the deer may be gone before you reach the point of impact.

Collins observed that the driver's instinct is to avoid crashing into a deer. But to lessen the chance of serious injury, the driver needs to stay in control of the car or truck. Slipping into a ditch, swerving and causing the vehicle to roll, leaving the pavement, hitting a fixed object or crossing the center line and hitting another vehicle are all much more dangerous than the collisions people typically have with deer. As deer also scramble to avoid a collision the chance of a glancing blow is more common than a head-on, full body hit. Given the prevalence of large SUVs, trucks and minivans, it is also less likely a deer will come above the hood and crash into the windshield.

All the speakers agreed: The odds of surviving a crash and staying alive increase significantly when drivers keep their cool, don't swerve and stay in their lane.

Testing the deterrents

Given the growing nationwide deer herd and steady increase in vehicle traffic, "road ecology" is a serious consideration as highways, overpasses and ramps are designed and built. Across the nation, traffic engineers are experimenting with road designs and other features to make crossing safer for wildlife and people. Examining the effectiveness of those designs and sorting out manufacturers' claims to determine if deer deterrents are effective calls for analysis by a neutral source.

One reliable center for such information is the Deer-Vehicle Crash Information Clearinghouse (DVCIC) at the University of Wisconsin-Madison. Funded by the Wisconsin Dept. of Transportation, the center compiles statistics about deer-vehicle crashes in Wisconsin, Minnesota, Michigan, Illinois and Iowa. DVCIC also evaluates the effectiveness of countermeasures designed to reduce such crashes. Center Director Keith Knapp of the UW-Madison Dept. of Civil Engineering and several graduate students recently completed a review of deterrents designed to reduce deer-car collisions. Here's what they said:

  • In-vehicle technologies – Some new cars are being equipped with infrared or heat sensors that provide some night vision for drivers. Currently the technologies are costly (in excess of $2,500 as a vehicle option) and are largely untested.

  • Deer whistles – Air-activated or electronic devices attached to the front vehicle bumper are supposed to emit sounds deer can hear from a distance, alerting them to an approaching car or truck. Research shows deer are sensitive to low sounds (2-6 kilohertz) below the range of human hearing. Only some of the deer whistles emit sounds in this range. The researchers did not find convincing evidence that deer hear and react to vehicle-mounted whistles, especially given other traffic noise. Such whistles may give drivers a false sense of security that deer will stay away from their moving vehicles.

  • Roadside lighting – Additional lights do not appear to reduce deer accidents, change deer crossing patterns or reduce average vehicle speeds. The results are a bit surprising given that limited tests reported an 18 percent reduction in deer crashes per deer crossing on segments with additional lights. Adding and lighting a taxidermy mount of a full-size deer in the emergency lane did reduce car speeds by an average of eight mph, but more tests are needed.

  • Speed limit reductions – This simple tactic hasn't been tested enough to reach conclusions. It appears drivers choose their operating speeds based on road conditions and roadway design more than posted speed limits in the absence of law enforcement.

  • Road salt alternatives – Like people, animals are attracted to salt, and salt melts snow and ice, exposing vegetation that might attract deer. One study considered how salt concentrations attract moose to the roadside area. Whether road salt draws deer near road edges is largely unstudied.

  • Artificial deer flagging – Whitetails raise their tails to expose the white underside as a warning. In one study wooden silhouettes of deer displaying this warning behavior were installed along a roadside. The field researchers concluded they had failed to demonstrate the models were effective in deterring deer from crossing roads or in reducing the number of deer along highway rights-of-way.

  • Intercept feeding – Can an easy meal lure deer away from the roadside? "Intercept feeding" can reduce the likelihood of crashes for a short period of time, but long-term results are inconclusive. Several studies have shown the incidence of deer road kills is not proportional to the deer populations living near those roadsides. There is no research on whether deer become dependent on roadside feeding stations. If deer congregate at feeding stations, then this method would not be practical in regions affected by CWD (chronic wasting disease, which is spread by close contact between animals).

  • Deer crossing signs and technologies – In a few places highway engineers have experimented with lighted signs warning of deer crossings or even radio collars on deer that trigger a lighted sign near the roadside warning drivers of deer activity. Researchers call for more testing or more designs before concluding if such approaches will slow down drivers and reduce the number of deer-vehicle collisions.

  • Roadside reflectors and mirrors – If the bright light from headlights were reflected into the surrounding land, would deer freeze or change their behavior to avoid roads? Five of the 10 studies concluded reflectors don't reduce road kills or crashes; two concluded they did. The other three studies were inconclusive. In fact most of the studies evaluating deer reaction to reflected light were either inconclusive or suggested that deer did not appear to react to light quickly enough to change their habits and avoid the light patterns formed by oncoming vehicles. Researchers called for better designed, longer-term studies to evaluate this technique for dissuading deer from roadsides.

  • Repellents – Repellents are "field tested" continually by homeowners, orchardists and others trying to keep deer away from their gardens, landscaping and livelihoods. There were no documented attempts to use repellents to deter deer from crossing or feeding by roadsides. Other repellent studies looked at kinds of repellents (predator, urine, odor, taste), how repellents were applied (sprays or pastes), concentrations, and effectiveness after rainfall. All repellents can reduce feeding somewhat, but studies haven't been repeated enough to make recommendations. Reviews of many kinds of repellents concluded that those leaving predator odors or putrescent odors like rotten eggs were more effective, but they haven't been tested to reduce roadside browsing. Further tests should be conducted at sites where deer-vehicle collisions frequently occur.

  • Hunting and herd reduction – Reducing deer populations clearly reduces unwanted consequences like overbrowsing, but it is unknown if smaller herds proportionally reduce the number of crashes along roadsides.

  • Driver information and education campaigns – The part of this equation most within human control is an attentive driver. Annual or more frequent reminders to motorists might change driving behavior during critical time periods. Awareness of the problem, suggestions to make motorists more attentive and strategies for minimizing damage all can help. Changing our driving habits to slow down in the seasons, times of day and locations when deer are especially active can save lives. Both deer and people need a little more reaction time to reduce the number of collisions.

  • Curbing roadside vegetation – Some have speculated that natural vegetation or intentional plantings along roadsides may attract deer and increase the chance of a collision. Several studies have documented which plants deer prefer, and it is clear woody shrubs will encourage wildlife use. However, no study concludes that plantings increase the number of deer killed along roadways. Two studies showed cutting back vegetation at least 65 feet along railroad rights-of-way can reduce moose/train collisions but the costs, aesthetics and habitat loss of such programs need to be evaluated.

  • Exclusionary fencing – Research shows erecting fences at least 8-10 feet high can reduce deer deaths by 60-97 percent. It is effective, but not a panacea. Fencing has consequences too. Quality fencing is expensive to install and maintain. It interrupts normal animal migrations for wildlife large and small. The restricted movement can isolate local populations of a species, which may create groups too small to survive or lead to inbreeding and a depletion of the gene pool. Fencing may not be attractive and must be designed with one-way gates to allow animals trapped in the road right-of-way to escape. Fencing is also impractical in very uneven terrain. All that being said, fencing will clearly continue as a strategy as roadways are built or expanded.

  • Wildlife crossings – A newer strategy in road building and modification is to establish overpasses and underpasses where wildlife habitually cross roads along major transportation routes. These artificial structures should be located along natural paths commonly used by deer or other animals. Successful crossings aim to maintain natural vegetation at the entrances, natural ground cover within the structure, and minimize human contact with the wary wildlife. Research suggests underpasses must be at least seven-eight feet high and at least 20-25 feet wide. Overpasses that are square or hourglass shape and at least 100 feet wide at their narrowest point have been successful. Two current studies are evaluating crossing designs and sizes.

Improvements in road design and other safety features, while welcome, are not the sole solution to the problem of car-deer collisions. "No driver should rely on these countermeasures or get overly confident they will prevent an accident," Knapp said.

Alert drivers who proceed with caution at this time of year are still our best lines of defense to avoid collisions and increase the chances that both animal and people will survive the surprise encounter.

David L. Sperling edits Wisconsin Natural Resources magazine.

How deer deterrents stack up
Techniques with generally positive results
Exclusionary fencing
Wildlife crossings

Techniques with conflicting results
Deer whistles
Roadside reflectors/mirrors

Techniques used, but rarely studied
Speed limit reductions
Deer crossing signs and technology
Hunting and herd reduction
Roadside vegetation management

Techniques used and not studied
In-vehicle technology
Salt de-icing alternatives
Public information/education campaigns

Techniques not generally used and rarely studied
Roadway lighting
Deer-flagging models
Intercept feeding
Roadway repellents