Some models cost as little as $5.00. If you ever hit a deer, you might want to spend the money and put these on! What can it hurt?
Buying a deer whistle
A study conducted by the University of Wisconsin concluded that deer did not respond to the whistles, even when drivers were well within the quarter-mile limit designated by manufacturers. Anything blocking the signal of the whistle that stood between it and the deer would also impede the deer from receiving it. According to the study, the whistle did produce an ultrasonic sound at speeds of more than 30 mph, but there was no evidence indicating that the deer heard it.