I believe the deer that is most likely to get you is likely not the one you see grazing on the side of the road. It is the one in full flight that is crossing the road (without stopping to check traffic
). It is amazing how far they can travel each leap when they are in full flight.
I don't believe that 'deer whistles' work.
On numerous occasions I have been working ground in a field next to a busy interstate style highway and watching multiple deer grazing happily in the same field. Surely some of the vehicles going bay were 'whistle equipped'. The deer didn't care.
What I do think they don't like is a change in the sounds they hear. They ignore the tractor going up and down the field, just like they are ignoring the nearby freeway traffic.
But slow the equipment to an to stop and idle the engine and they look up. Open the door to get out for a better look or to take a picture and they seem to hear the click of the door latch releasing they are gone.