Despite having been a driver for nearly 50 years, I have never been in a deer-vehicle collision. Though, I have had a few near misses. Michael Conover from Utah State University says that up to 1.5 million drivers are NOT as fortunate each year.
Several methods have been suggested to reduce deer-vehicle collisions. These include highway fencing, animal guards and overpasses as well as biological repellents, lure crop, road salt alternatives, warning reflectors and driver education. Unfortunately, not all of these methods have been scientifically tested.
The most common type of vehicle-mounted whistles is the deer whistle. Many motorists rely on vehicle mounted whistles to avoid deer-vehicle collisions. Manufacturers claim that they are easy to use and inexpensive. However, research suggests otherwise.
Can Deer Hear Deer Whistles?
Hunting deer is a difficult task because they have sensitive ears. Dietland Müller-Schwarze, a well-known researcher, compares deer’s hearing abilities to that of a satellite dish. He says it “points to the heavens, collecting signals for its owner to sort out, and tune in.”
Deer can sense whether sound is coming from the front or back, even when its ears remain stationary. Deer can use their ears to pivot towards the sound and compare the signals from both ears to pinpoint its source.
Our Editor, Josh, says that sounds are described based upon two qualities:
The frequency is the distance sound waves are from each other. It’s measured in cycles per second (called hertz). Higher frequencies equal higher pitches.
This is the measurement of how loud sound waves are. It is measured in decibels. The scale increases by 10 factors.
Gino D’Angelo and coworkers at the University of Georgia found that white-tailed deer are able to hear in the range of 0.25-30 kilohertz. Their best hearing sensitivity is between 4 and 8 kHz. Note: A kilo is equal to 1,000.
D’Angelo’s team used an auditory brainstem test to evaluate whitetail hearing ability. The procedure involved placing electrodes strategically on the heads of drug-immobilized whitetail deer and testing their brain responses to different sound frequencies. Finally, the electrical responses were displayed on a monitor for analysis.
As one might expect, the best hearing range of whitetails overlaps with primary frequencies of vocal communication. Sonographic analysis has previously identified 12 vocalizations in whitetails. The majority were composed of frequencies between 1 and 8 kHz.
The frequency range of 2 kHz to 5 kHz is the best for human hearing. There is a maximum limit of 20 kHz. The University of Georgia group recommended that further research be done on ultrasonic whistles because deer can detect higher frequencies.
The Heffners, from the Whitetail Deer Research LLC, Ohio, obtained behavioral audiograms of two captive deer using a “conditioned-suppression avoidance procedure.” In simple terms, they conditioned thirsty deer to drink from a metal bowl that was wired to present a mild shock. The sounds were presented at random intervals and then followed by mild electric shocks. The shock was avoided by the deer by breaking contact with a bowl. This indicated that the animal had heard the frequency of the sound.
Heffner’s study revealed that the whitetail’s hearing range is between.115 kHz and 54 kHz. The hearing range can be increased by increasing the volume of the sound (to over 90 decibels) to reach 64 kHz. The Heffners found that whitetailed deer has better low-frequency hearing than humans and have better high-frequency hearing.
Background on Deer Whistles
Deer whistles were invented in Austria in 1979 and are still being sold by many companies across Europe and the United States. While simple air-activated whistles can be purchased online for as low as $5-10 per piece, electronic systems can cost hundreds of dollars. These devices attach to the vehicle’s front and emit ultrasonic frequencies that warn animals about approaching vehicles. This is said to reduce deer-vehicle collisions.
Researchers Larry Dalton and Laura Romin in Utah found no difference in the responses of 150 free-ranging muledeer groups to vehicles with and without deer whistles. Some deer did run away from the vehicle, but they did so regardless if whistles were present or not.
Sharon Valitzki, University of Georgia researcher, recently reviewed the effectiveness of deer whistles. She found similar negative results: “Previous research regarding vehicle-mounted auditory repellents was confounded with commercially manufactured devices lacking proper function and sound intensity that can be audible by deer in road conditions.
Some commercially available deer whistles don’t produce ultrasonic sound, contrary to what is claimed. Some emit no sound under normal operating conditions.
The Deer Whistles are now in the forefront of science
It is important to understand that deer whistles produce a consistent, continuous sound of equal intensity at the same frequency. These “pure tones” can also be made with standard sound equipment.
Valitzski and her team tested a variety of pure-tone sounds to alter whitetail behavior along roads in order to prevent deer-vehicle collisions. The study was done at Berry College Wildlife Refuge in northwestern Georgia. It covers an area of approximately 100 deer per square meter.
Georgia-based researchers built a test vehicle equipped with four high-frequency speakers that could deliver frequencies between.28 and 28 kHz. The speakers were designed to emit sounds both in front and to the sides of the vehicle. The sound intensity was set to 70 decibels so that the deer could hear both the transmitted sounds and vehicle noise within 10 meters (32.8ft) of the vehicle.
The study area of influence was divided into two areas. Each zone included a 10-meter buffer zone and a roadway. Each test was conducted by an observer who recorded the deer’s behavior during each of the six randomly chosen treatments. The vehicle-mounted sound system produced five frequencies and a control (no sound) as the vehicle drove 30 mph through the area.
To maximize deer sightings and to preserve the sound quality, each trial was conducted at dawn or dusk. The behavior of select (i.e. focal) deer were recorded before and after exposure to the test vehicle. These behaviors were then recorded by the observers.
1. Deer reaction — likely to cause an accident between deer and vehicle;
2. A positive interaction – deer reaction less likely to cause a deer-vehicle collision;
3. Neutral interaction — there is no increase in the risk of a deer-vehicle collision.
The researchers concluded that the pure tones didn’t alter the behavior of deer in a way that would prevent them from colliding with other vehicles. The simulated deer whistles did not have the same effect as any sound.
Overall, 54% to 71% of observations were classified neutral. This means that more than half of deer’s behavior was not affected by the test vehicle. Only the lowest frequency (.28 kHz), produced significant responses. This was because deer were more likely than others to cross the road in response to the treatment.
All sound frequencies tested were audible to deer, unlike some deer whistles. The investigators recommend the following because of the deer’s inability to respond:
1. Deer might not have enough time to respond as quickly as they want.
2 Deer might not have the ability to efficiently process alarm information to allow them to respond in a desired manner.
3 Deer may not recognize the sounds of threatening.
These results were made using tones that are similar to deer whistles mounted on vehicles. It was determined that these products wouldn’t be effective in preventing deer-vehicle collisions.
How to use Deer Whistles
Deer whistles must be heard as far as possible from the vehicle so they can be heard by the deer. The Georgia tests were conducted in ideal weather conditions. However, researchers were unable to transmit ultrasonic frequencies beyond the 10-meter by 30-meter zone of their influence without damaging sound-producing equipment. Hearing safety for pedestrians is also a concern. Certain laws limit the maximum allowed noise.
The Georgia group examined the effectiveness of pure tones similar to vehicle-mounted deer whistles. Natural sounds, on the other hand, are complex because they emit different frequencies simultaneously.
Although complex sounds that alternate between low and high frequencies might be more effective in changing deer behavior and preventing collisions with deer-vehicle vehicles, the associated research is not encouraging. However, I have not seen any studies that show deer are frightened of a certain frequency or decibel level of sound. This is contrary to claims made by the manufacturers of these devices. Deer can even become habituated to sounds that initially scare them.
Based on their research experience, Georgia-based researchers concluded that auditory deterrents are not appropriate for preventing deer-vehicle collisions.