The way I understand it is it has to do with the rut, weather and testosterone levels. I think how hard the winter is, is the biggest effect. So a buck that did a lot of breeding, and had a hard winter would make his testosterone level drop and he would drop his antlers before a buck in a different area with a more mild winter. This is what I've been told. It makes sense to me because where I shed hunt last year we had a harder winter and found sheds in January. This year we had a very mild winter and are just now finding sheds. Correct if I'm wrong. But its a good enough explanation for me