it seems that deer can be pretty smart. We have a lot of them around here, and there will be periods when you see them standing near the road, happy & careless. Then there will be periods when you don't see them, and they are obviously much more cautious. I think I may have it figured out. Our mountain lions are said to have territories of around 50 square miles in New Mexico. I think when they cruise through this part of their territory the deer get a lot more careful.