Whistles and Whitetails

.....Reprinted with permission from Motorcycle Consumer News."

Randall P. Schwalbach, DEER AND DEER HUNTING, Nov., 1989.

Recently, several wildlife researchers questioned the validity of these claims [manufacturer claims that deer whistles work]. A need to physically test deer whistles and explore the absence of ultrasonic sound arose from the absence of scientific literature coupled with the general unwillingness of companies that market deer whistles to provide any meaningful data supporting their claims. Working independently and using different methods, researchers in both Georgia and Wisconsin arrived at similar conclusions.

These findings identify factors that indicate considerable doubt concerning the effectiveness of these whistles as deterrents to car/deer collisions:

1) Some deer whistles do not emit the ultrasonic sound under the advertised operating conditions [typically when the vehicle exceeds 30 mph].

2) The physical properties of ultrasonic sound negate its effectiveness at distances required to warn deer.

3) We know little about the auditory limits of deer, but what we do know indicates that deer hear approximately the same frequencies as humans.

4) If deer could hear ultrasound, we do not know that it would alarm them or induce a flight response.

The Georgia Game and Fish Department began their investigation by requesting data from the "scientific tests" the advertisers had used to support their product claims. In response, one distributor sent a packet of newspaper clippings and letters from sheriffs [sic] departments, all attesting the whistles were a godsend. One deputy had tested them by driving his whistle-equipped patrol car toward a herd of deer in a field. The deer scattered, he reported with enthusiasm. Such testimonials - of no scientific significance - prompted responsible evaluation.

The [Georgia Game and Fish] department recognized that rigorous investigation of the whistles' effect on animals was dependent on the whistles making the sound in the first place.... Using a Custom Telemetry Ultrasonic Receiver [plus more measuring equip], they did not detect any ultrasonic sounds [at speeds from 25-55mph]. According to Greg Schidwachter, "Apparently, the force of air through the device was too weak to produce sound of any frequency."

[Even if the device DID make the sound claimed at frequencies from 16 to 20 kHz] We found no published research indicating that frequencies from 16 to 20 kHz elicit a flight response in deer or other ungulates, such as cows and horses.

A study of the hearing ability of white-tailed deer at the University of Georgia sheds additional light. Unpublished results by Stattleman indicate that deer cannot hear sounds with frequencies of 6 to 20 kHz. In this respect, white-tailed deer hear approximately the same frequencies as humans.

To complete the study, the Georgia Game and Fish personnel blew the whistles by mouth near some captive deer. This did not affect their behavior in any way. The team concluded, "The whistle we tested does not emit an ultrasonic sound under the advertised conditions, and deer could not hear it, if it did."

Timothy J. Lawhern, an undergraduate student at the University of Wisconsin, Madison, arrived at similar conclusions through a separate and perhaps more rigorous investigation of deer whistles. In contrast to the Georgia study, Lawhern found the three devices he tested to produce ultrasonic frequencies up to 48 kHz; however, he still concluded that "it is highly unlikely deer would be capable of responding to this signal."

Interestingly, in the course of his research Lawhern tested the whistles in the presence of seven species of the deer family, including 45 white-tailed deer. Possible responses he looked for included ears or head turning, flinching, or looking in the direction of the sound. Out of all these animals, however, only one response was noted, this from a single bull elk. At the shrill sound of the lower pitched whistle (audible to human ears) he charged the enclosing fence, in the process breaking a 2X4 post. In prolonged rage, he then bugled and urinated.

[After testing for the frequencies which the devices produce] Lawhern concluded that "they do indeed produce ultrasonic frequencies." But as the Georgia study indicated, so did Lawhern discover that not all sounds produced fell within the range of ultrasound."

Lawhern summed it up: "Based on the knowledge of ultrasonic frequency coupled with observed field testing of various animal species, it is highly unlikely that an ultrasonic signal produced by the whistle devices would reach a deer at a decibel level such that it would be detected even at ten meters, much less than the 300 to 400 meters claimed."

Scott Craven, University of Wisconsin Extension Wildlife Specialist, agrees with Lawhern's conclusion. He believes that people who install whistles may be more likely to watch for deer. At the same time he explains, "Any cure is going to look attractive. Some people use the whistles and are happy with them because they haven't hit a deer."

Craven receives many requests for advice on the use of deer whistles and he concludes, "Until I see some solid evidence to support the use of deer whistles, I cannot, as a wildlife professional, recommend their use. I contend there is no substitute for driver education and awareness of the areas, seasons and times of day of vulnerability."

As expected, the number of car-deer collisions relates directly to the overall intensity of deer movement. Mid-Spring and mid-Fall (during the rut) require special attention. In mid-Spring, deer cross roads frequently as they try to graze on new herbaceous vegetation. . . . In northern states, the salt-drive phenomenon also causes deer to frequent roadsides as they search for residue from winter road-salting operations.

According to research in Michigan and Wisconsin, the rutting season in fall, with its increased deer movement represents a time of peak hazard. At this time deer are often oblivious to outside happenings as they pursue breeding activities. Through a chronology of 1,151 such collisions from 1976-78 in Columbia County, Wisconsin, Pils and Martin (1979) identified November as the peak month for car-deer collisions. . . . They also noted a surge late in November, which they attributed to the hunting season [and theorized that it was] probably because hunting disturbance caused greater deer movements.

Meanwhile, as deer remain primarily nocturnal at all seasons, night-time driving increases the chance of hitting a deer. Pils and Martin noted that most deer collisions occur at sunset.

In addition to seasonal peaks in deer movements across roads, deer cross some sections of road more frequently than others . . . . Motorists who do not honor [Deer Crossing] signs (by slowing down) or who simply do not notice these signs at all further increase their chances of hitting a deer.

[paraphrasing the summary]: If use of deer whistles results in increased awareness of deer dangers, then a motorist's chances of hitting a deer may be reduced. On the other hand, use of deer whistles may give him a false sense of security. Further reading : What Do Deer Hear?

Last update: 04:12 PM Sunday, September 26, 2004

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