Yep, it's all related to testosterone levels in the buck. But the reason you are seeing so many variances mrbb is there are a LOT of factors contributing to the testosterone levels. And every Buck is different. Some factors, but not even close to ALL are, weather patterns, number of Does in the area disseminating their hormones, actual rut activity (number of Does bred), mineral content in the food coming up to rut, and literally tons more stuff that contribute to them dropping and when.