my yearly reindeer rant: both male and female reindeer grow antlers in the summer each year but male reindeer drop their antlers at the beginning of winter, usually late November to mid December. Female reindeer retain their antlers till after they give birth in the spring. Therefore, according to every historical rendition depicting Santa's reindeer, every single one of them, from Rudolf to Blitzen ... has to be a female.
In the old nature religion (in which the divine was often perceived as feminine) it was the female horned reindeer who reigned supreme as the great goddess of the winter solstice. http://gathervictoria.com/2014/12/04/doe-a-deer-a-female-deer-the-spirit-of-mother-christmas/
Although antlers may be considered a masculine symbol, goddesses and female shamans wear them. Deer women appear throughout world mythology. Bendis, Artemis, Elen of the Ways, Satet, and many reindeer goddesses. Female reindeer, btw, have antlers and they are among humanity's oldest deities. (For the less spiritual, you can just enjoy this photo as a sexy Hannibal cosplay.)
Prague's Zoo Praha has two new baby reindeer, a boy and a girl. The male was born on Friday the 13th and the female came along about three days later. They went out in the zoo's large paddock for visitors to see for the first time on April 20. The mothers can be seen with their babies following closely behind them. The father of both is Mirda, who himself was born in Prague Zoo.