Just my theory. I in no may claim this to be fact. I am going to do a little testing this year though.

Deer can smell danger even before it is spotted. They run from dogs, coyote, wolf, humans, and I have even seen them run from a racoon. I have never seen a deer run from a horse or cow. Now this does not just occur at the mature adult level of deer only. This occurs at any age. Deer have a very small brain and are not capable of complex thought patterns. So here is my theory.

Years ago the government tested a device that would detect the scent of a meat eater. This could prove useful if the enemy was vegetarian. If this is possible, maybe the deer detect meat eaters as a scent trigger for danger. They run from dogs, coyotes, humans, etc which are all meat eaters. They do so without seeing them. A cow can tromp through the woods and will only move deer if they come in close contact. I have seen cattle and deer feeding with in 20 yards of each other in a pasture.

some say that the reaction to the scent is a conditioned response but why then don' t deer run from cars along the road. Many, many, many deer are killed by automobiles.

I am going to eat vegetable for 2-3 weeks before season and see what happens.

Now this is just my theory. I would love to hear your responses.