Whistles: Deer warning whistles have been available to the public for more than 20 years. A
typical whistle is attached to a vehicle and produces ultrasonic noise in the range of 16-20 kHz when
vehicle speed exceeds about 30 mph (DeerCrash, 2003). Whistles are based on the presumption that deer
can hear and will be warned away from noise in this range. Twenty states reported using whistles in 1992
(Romin and Bissonette, 1997), although state wildlife agency and transportation department
administrators ranked whistle effectiveness lowest of all common methods (Sullivan and Messmer, 2003).
Romin and Dalton (1992) conducted the only high-quality study of whistle effects. They drove
past 150 groups of deer at distances up to 100 meters and a speed of 65 km/h, observing deer behavioral
responses. Two common brands of whistles had no effect on deer behavior, even when deer were within
10 meters of the road. Romin and Dalton were unaware of any research demonstrating that deer are
frightened by sound in the range produced by whistles. In a review of the effects of sound on animals and
birds of many species, Bomford and O達rien (1990) concluded that sounds of the type produced by
whistles (steady noise rather than specific alarm or distress signals) may influence movements in the short
term but that mammals and birds become accustomed to these sounds after long or frequent exposure.
Several less scientific reports and considerable anecdotal evidence either support or deny the
effectiveness of whistles. For example, Cline (1989) reported on a one-year test of whistles attached to
42 Michigan State Police vehicles in five locations; 43 vehicles in five other locations served as controls.
There were 14 DVCs involving police vehicles in the test locations and 5 in the control locations during
the prior year; during the experimental year, there were 5 DVCs in each location. Based on these results,
Cline concluded that the whistles were effective.
Roadside whistles, as opposed to vehicle-mounted whistles, are being tested in Saskatchewan
(Beaupr? 2002). A series of noisemaking devices together with vehicle detection sensors was mounted
along a 5 km section of highway. When the sensors detect a vehicle, the device warns deer with either
sound or light signals.
In summary, there is no firm evidence that whistles are effective and considerable evidence that
they are not. In the only high-quality study (Romin and Dalton, 1992), deer were not affected by
whistles. It is unclear whether deer can hear whistles, whether whistle noise is covered by traffic noise, or
whether deer become accustomed to whistle noise over time. In the absence of any solid studies that
whistles are effective, they cannot be recommended.
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