Antelope can't count legs! Well done. :thumbsup:
( Will Gere made that point to Robert Redford in " Jeremiah Johnson" when they used a horse to get close to an Elk.)
Yes, Antelope like all prey species, have lousy depth perception. Their eyes are mounted at the side of their heads, preventing them from seeing forward, and using " Binocular vision " to triangulate distance. That doesn't mean they don't see well, or recognize movement. The " trick " in using a cow decoy, is not to move any faster than a wandering cow. That is usually a " slow walk " pace, with many stops to taste and eat the available grasses. If you are going to make your own, make it with a head that can move up and down , and with a rope for a tail to make a stiff but flexible tail for reality.
If you watch cows enough, you will note that when they are happy and eating, the tail moves very little. The most movement you will see of a cow's tail is when its warm, and the flies are bothering it. Then the tail becomes the fly swatter. If the flies are not out, don't expect to see much tail action.
Like other prey species the tail moves before the head comes up. And, the tail often moves before the cow begins walking again. The cow, like the antelope, will take a look around for other animals and predators, when its head comes up.
If the antelope move, the cow will stop and watch them, trying to figure out if they are prey or predator, and prepare to flee.
If the antelope run towards the cow, the cow will run, too, in the same direction that the antelope are running. The cow figurs that something is chasing the antelope. However, if you are within 50 yards of the antelope, the cow is likely to face the potential threat, and look for it. It can easily stomp a coyote that would pose a serious threat to the antelope.
Watch the winds. If they pick up, get down off the high ground. Not only will it make it difficult for you to hold that piece of plywood up, but cows get out of the winds when they can. They rely on their hearing to warn them of potential threats, as much as do antelope. Winds destroy both their hearing, and their ability to smell other animals.