Yes! They do work

by Karen
(Central Texas )

We have used these whistles for 13 years. We live in a very high deer traffic area in the Texas hill country and there are deer along all the roads and highways. We would not be without them. Years ago my husband was a TX highway patrol officer and they had these whistles on their cars and swore by them. Because of these whistles I have not had a deer jump and run as I drive by. Most often they just glance up and then go back to browsing. The whistles work by giving the deer a heads-up that you are coming and so they don't panic and and run or jump into the road. It's like petting a horse to let him know before you go behind him. He knows you are there and is not startled. Once one fell off the passenger side of our car and I knew immediately that is was gone by the deers' reactions along the road on that side of the car. They were much more skittish and prone to jump, sometimes into the road. I feel much safer with them, especially at night when the deer are hard to see.