Few of us ever see Santa's reindeer up close. But there are pictures of them, and in these pictures Dasher, Dancer, Prancer, and the rest often sport antlers. Which means that even Vixen is male, right?
Not so fast. Reindeer -- we call them Caribou in North America -- are unique among deer in that the females grow antlers, too. Another point worth mentioning is that mature male Caribou shed their antlers in the fall and are unadorned on Christmas Eve. Females and immature males, by contrast, don't shed their antlers until spring.
So the creatures that pull Santa's sleigh must be females or young bucks. The only other explanation is that flying somehow alters a Caribou's hormonal cycle so that even mature males keep their antlers through the holidays.
Click here to learn more about Caribou.