Do Car Deer Whistles Work?

do deer whistles work
The idea is that deer whistles alert animals to impending danger, but do they really get the job done?. AdShooter / E+ / Getty

High-speed collisions with deer are almost a matter of course in many areas, and they are devastating for all parties involved. Most deer struck by cars die, cars that strike deer can incur thousands of dollars worth of damage, and the people in those cars can suffer grievous injury, up to and including death. In the last few decades, deer whistles have emerged as the best way to prevent these deadly accidents, but questions remain about whether or not deer whistles work as advertised.

It’s only natural to look for ways to avoid deer collisions, and many people swear that devices like deer whistles really do work. However, all available evidence appears to favor technologies like adaptive headlights and collision avoidance systems, and techniques like defensive driving, as more effective at avoiding deer collisions than deer whistles.

The Growing Problem of Deer Collisions

According to the Insurance Information Institute, about 1:169 drivers in the United States collided with a deer in 2015. Since there are about 210 million licensed drivers in the country, that adds up to a tremendous number of collisions between deer and automobiles each year.

The frequency of deer collisions can be traced back to a number of causal factors, including habitat fragmentation, where deer are forced to cross roads to forage, and the gradual acclimation, over generations, of deer to road noise.

Deer populations have also rebounded in recent years, due to hunting restrictions and the eradication of predators like wolves from many deer habitats. Since there are also more licensed drivers on the road every year, and deer populations are exploding in many areas, an increase in deer collisions seems almost unavoidable.

Deer are heavy animals with a center of gravity that is elevated by long legs, which is why striking a deer is often catastrophic for both the animal and the vehicle. According to data from the Insurance Information Institute, the average damages incurred by a vehicle in a deer collision add up to more than $3,000. For older cars and trucks, that’s often enough to total the vehicle.

While about 150 people died in deer collisions in 2008, and nearly 30,000 more were injured, deer still get the worse end of the deal. In fact, the total number of deer killed by hunters each year is only about six times larger than the number of deer killed in automobile accidents.

While hunters take more than six million deer each year in the United States, according to data from the American Institute of Biological Sciences, drivers strike and kill more than one million deer each year.

The Mechanism Behind Deer Whistles

The basic idea behind deer whistles is that they emit ultrasonic sounds that supposedly alert deer to impending danger and scare them off. The noise is typically generated by air passing through the whistle, which is often mounted on the front bumper or roof of a vehicle. Electric deer whistles are also available.

Manufacturers and proponents of deer whistles claim that deer and other animals can hear the ultrasonic frequencies generated in this manner, but the sounds are too high-pitched for humans to hear. Further, they typically claim that deer are naturally skittish animals, so the loud, high pitched sound from a deer whistle will cause them to either stop or run away.

At this time, all evidence that deer whistles work is anecdotal, which is to say that people who use them are often fervent supporters of the technology. Since many people who install deer whistles do so after a catastrophic collision with a deer, moose, or another large animal—or even several such accidents—a lack of further accidents is seen as proof that deer whistles work, and it’s hard to argue with personal experience.

So Do Deer Whistles Work?

While anecdotal evidence does say that deer whistles do work, and some companies even install deer whistles on all the cars or trucks their fleets or insist that their drivers install them on their own vehicles, the jury is still out.

For instance, if there was any real evidence that deer whistles work in any demonstrable way that could reduce accidents, and insurance claims, you might expect insurance companies to provide a discount or even offer free deer whistles to policyholders. However, the opposite is actually true.

Most insurance companies, which often give discounts for safety technologies like airbags or car alarms, do not promote the use of deer whistles, and many companies like Allstate and Geico actually recommend against using deer whistles.

Another sticky issue is whether deer whistles operate as advertised.

Companies that manufacture these devices typically say that they emit ultrasonic frequencies that scare away deer, which are naturally skittish animals. That seems to make sense, but it isn’t actually backed up by any real, non-anecdotal evidence. In fact, some studies have shown that deer whistles—or at least the specific products looked at in the studies—don’t even generate ultrasonic sound, which is generally accepted as frequencies above 20 kHz that fall outside the realm of human hearing.

Not all deer whistles claim to generate ultrasonic sound, so this disconnect is not necessarily an issue of truth in advertising. It’s also important to note that different deer whistles generate different frequencies, at different intensities, based on the design.

Some do generate sounds that deer are capable of hearing, so the question is whether those sounds are actually effective at preventing the animals from darting into a roadway.

Studies show that deer whistles are not effective, while anecdotal evidence says they are. However, these devices are relatively inexpensive, easy to install, and using deer whistles is unlikely to hurt anything even if they don’t work as advertised.

Evidence That Deer Whistles Don’t Work

While there are no studies that show deer whistles work, that doesn’t mean there haven’t been any studies on the matter. Numerous government agencies, universities and even insurance companies have looked at and tested deer whistles, and they all agree on a few points.

Most importantly, the available scientific data on deer whistles overwhelmingly points in the direction that there is no statistically relevant difference in deer reactions to vehicles without whistles as compared to vehicles with whistles installed.

Another point raised by multiple deer whistle studies is that it isn’t clear whether deer can even hear the ultrasonic sound frequencies that deer whistles are supposed to use to scare them away. While deer can hear higher frequencies than humans, studies have shown that the range of sounds which deer hear the best fall below the frequencies generated by some deer whistles.

For instance, one study published by the Acoustical Society of America found that closed-ended deer whistles produce frequencies of about 3.3 kHz, while open-ended whistles produce frequencies of about 12 kHz that vary widely based on air pressure, both of which fall short of the 20 kHz mark commonly associated with ultrasonic sound.

While 3.3 kHz falls within the best hearing range of deer, and 12 kHz is inside the range of sound frequencies they can hear under ideal conditions, the study also found that the intensities at which deer whistles created these sounds were “totally lost” in the ambient road noise created by a typical car or truck.

Evidence of this assertion was that while the closed-ended deer whistles generated a 3.3 kHz sound, which is well within the range of human hearing, human subjects were unable to separate the noise of the whistle from general road noise.

Although it is possible that deer could be better at identifying sounds at those frequencies, all of the available data shows no statistical difference in deer reactions to deer whistles versus cars with no deer whistles. Since deer clearly habituate to general road noise, it is possible that they do hear the whistles, but they eventually grow just as used to the higher frequency sounds as they are to other road noise.

Avoiding Deer Collisions Without Deer Whistles

With more deer living and grazing near roadways each year, and more licensed drivers on the road than ever before, devastating collisions between deer and cars are unlikely to go away. However, there are a number of ways to reduce the odds of striking a deer, even without deer whistles.

Defensive, attentive driving is the best way to avoid hitting a deer or any other animal and keeping a watchful eye whenever you enter a deer crossing sign is also of vital importance. Since deer often travel in groups, seeing one animal on the side of the road also increases the likelihood of seeing more, so slowing down in such a situation is an excellent preventive measure.

There are also a handful of car safety technologies that can help reduce the chance of hitting a deer, which is most likely to occur in the hours between dusk and dawn. Using high beams where appropriate can help identify animals on the road in time to stop, and adaptive headlights are useful in situations where an animal may be lurking beyond a corner, where normal headlights would shine uselessly off the road.​

Collision avoidance systems can also identify obstructions, up to and including deer, and provide a warning, precharge your brakes, or even automatically stop the vehicle short of striking the animal.

In the event that a deer does leap out in front of your vehicle, it is important to brake while remaining in your lane. While swerving may allow you to avoid the deer, it is also likely to place you, your passengers, and other drivers at greater risk. Swerving into the oncoming lane often can lead to a deadly head-on collision with another vehicle, and most rollover accidents occur when a car or truck runs off the road.

Some collisions are impossible to avoid, with or without deer whistles. But with deer collisions leading to more than 150 human fatalities each year, coupled with one million dead deer and more than four billion dollars in property damage, even small adjustments in behavior and the use of technology could make a huge difference.

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