Interesting observation. I spent 13 years doing whitetail research throughout the Midwest and east coast and have noticed similar situations. It is a combination of day length and the response of the pituitary and then the drop in testosterone levels. I have collected whitetails as early as mid October that have cast their antlers while others collected in late April still had one or both antlers. Most of the bucks were 3 years old or younger. One common link is some of the April examples was damage to the scrotum and testicles by whatever means. This definitely interferes with testosterone levels and might be contributing to bucks retaining their antlers longer. With that said, I have to wonder if there is another variable involved such as population dynamics and sex ratios in a given area and weather. I'm sure there is someone doing some graduate research out there that has published their findings in. A professional journal that might be of some assistance.
Tracy
