Life Of Siberian Reindeer Herders, Yamal, Russia.

Santa Claus's reindeer
In the Santa Claus myth, Santa Claus's sleigh is pulled by flying reindeer. These were first named in the 1823 poem "A Visit from St. Nicholas", where they are called Dasher, Dancer, Prancer, Vixen, Comet, Cupid, Dunder, and Blixem. Dunder was later changed to Donder and—in other works—Donner (in German, "thunder"), and Blixem was later changed to Bliksem, then Blitzen (German for "lightning"). Some consider Rudolph as part of the group as well, though he was not part of the original named work referenced previously. Rudolph was added by Robert L. May in 1939 as "Rudolph the Red-Nosed Reindeer".
According to the British comedy panel game QI, Rudolph the Red-Nosed Reindeer and all of Santa's other reindeer must be either female or castrated, because male reindeer lose their antlers during winter.