Air-fed Deer Whistles Scientifically Tested
(Released: November 19, 2002)
By Janice Palmer, Office of University Communications
STORRS, Conn. -- Air-fed deer whistles, those small plastic
devices attached to car bumpers to scare deer from roadways, are
"acoustically ineffective". That is the finding of a
scientific study conducted by Peter Scheifele, an animal
bioacoustics and audiology expert at the University of
On highways and byways across North America, nearly 750,000
collisions occur each year between deer and vehicles. Manufacturers
promote deer whistles as "acoustic attention-getters",
alleging deer will react to the whistle by remaining still.
"There has been a lot of conjecture about whether the
whistles work or don't work, and we are one of the first
independent groups to scientifically test them," says
Scheifele, director of bioacoustic research at the National
Undersea Research Center at the University of Connecticut's
Avery Point campus and researcher in the Department of Animal
He and his team tested six air-fed whistles in the laboratory
and in the field. The study's goal was to determine the actual
frequencies generated by the whistles and the intensity at which
they are produced; compare that data to the hearing abilities of
deer; and then take the animal's acoustic behavior into
Following the directions on each package, the team mounted the
devices onto a car's front bumper. Using a road closed to the
public, they drove the car at speeds ranging from 30 to
45 miles per hour while recording sound and data.
"We tested them strictly from an acoustical point of
view," explains Scheifele. He found that the whistles
typically produce a signal either at a frequency of 3 kilohertz
(kHz) or 12 kHz. Both, as it turns out, are problematic.
The hearing range of white-tailed deer, the most common species
in the U.S., is between 2 and 6 kHz, so the animal is not capable
of hearing the 12 kHz signal. Although deer may be capable of
hearing the 3 kHz signal, it is only 3 decibels louder than the
road noise created by the car, so the signal is buried. Scheifele
points out that the condition would worsen with additional traffic
in the area or if the wind was blowing.
Since completing the study, a new electronic whistle has been
put on the market. Although Scheifele has not had an opportunity to
test it, he has examined its advertising claims. He says the specs
for the electronic whistle are considerably different from those of
the air-fed devices, so "there is a possibility that the
electronic whistle is more effective than the air-fed
But even if deer can hear the electronic signal, the UConn
scientist questions how one alerts rather than startles the animal.
This is where animal behavior comes into play.
"Think about the metaphor 'deer in the
headlights'," says Scheifele. "It is used to conjure
up an image of someone who is confused or frightened. When deer
sense something unusual, we do not know for sure how they are going
Will they freeze in their tracks, run off, or charge towards the
sound? Their behavior is related to the "fight-or-flight
response". According to scientific literature on the subject,
there is an amount of space in which an animal feels safe; but once
that boundary is violated, the animal's reaction is
unpredictable. Its response will depend on a number of factors,
including age, sex, type of enemy, and surroundings.
"All in all, the air-fed whistles do not make sense to me
acoustically," states Scheifele.
He has written a paper on his findings and submitted it to the
Acoustical Society of America's Acoustics Research Letters
Online where it will shortly be under review.
November 2002 Releases
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