I know several people that have hunted archery antelope in 21. The success is always zero. They have said it is hard to locate the antelope and it is a very hot hunt. In August the temperature is in the area of 110*. A friend had a tag there last year and, was hunting private land. he only saw 4 antelope, with only 1 being a buck.
A few years ago, I talked to the game manager for 21 and, he said the herd is "maintaining", not growing in other words. One of the problems is cattle are direct competitors for feed and the antelope have to migrate alot between feed and reliable sources of water.