Ayaapeensa Kiilhswa (Young Buck Moon) is one of two lunar months named for White-tailed deer (Odocoileus virginianus). To the best of our knowledge, this month is associated with the beginning of the rut (breeding cycle) for White-tailed deer.
In some years, the younger males lose their antlers by the end of this month. Today, there is a lot of variation within the White-tailed deer populations regarding when bucks drop their antlers. It appears that historically, the young White-tailed deer bucks dropped their antlers first. The loss of antlers marks the end of the rut (the breeding cycle) for these younger male deer.
*photo from Michigan State University – http://deer.fw.msu.edu/management/history.php/