I'm not what I would call a great hunter or wise one but I enjoy doing when I can a learning about it. I have heard it is . The moon phase . The weather. Ive heard it depends on the food that year. I've been told it happens a then it's over. I hunt 3 counties each has been different that I can see with my own eyes . Roan Loudon meigs I've seen chasing by a mature buck in Meigs this year while also still having does grouped saw around a 3.5 chasing in Loudon a still have does grouped. I think even if I haven't seen it my self when bucks start to cruise the first doe has been bred by a mature buck. May be even acouple that don't stay with the groups. I think the older buck or bucks know when the day shorten it's close to breeding time. find probably a mature doe a stay with an Around her a bring her in heat . An have bred weeks before we see prime action younger smell it a raises there test level an it snow balls from there.deer are no different than any other animal an every female is different from dog to cow . Some you can set a clock by some early some late. But the hot part is just the majority that comes in togather. This might be way off but I'd love to here any views