Every Christmas Eve, as the story goes, a team of reindeer led by red-nosed Rudolph flies a sleigh carrying Santa Claus around the world to deliver toys to children.
The rest of the year, the reindeer live at or near the Arctic Circle around Santa's homeland at the North Pole.
I've seen reindeer in Iceland, but I've never seen them fly. So I asked Santa about his reindeer. Here's what I learned:
Santa's reindeer are described as "tiny" in the poem "The Night Before Christmas," but they're actually big animals that look like elk. They stand about 5 feet tall at the shoulders, reach a length up to 7 feet from head to tail, and can weigh as much as 700 pounds.
"They just look tiny the way a jet airplane does when it's high in the sky," Santa said.
Reindeer are in same Cervidae mammal family as white-tailed deer in Texas.
Caribou in Alaska and Northern Canada are actually reindeer in the species Rangifer tarandus.
Reindeer live in boreal forests and tundra in Arctic and Subarctic regions.
Footpads on hooves become sponge-like in summer to walk on damp tundra and shrink in winter so that hoof rims can step firmly on ice and snow.
Acute vision may see ultraviolet light to discern objects on glaring-white Arctic landscape.
Reindeer eat lichens, willow and birch leaves, grasses, herbs, berries.
They can swim 6 mph across a lake or large river.
Santa's lead reindeer does have a red nose, but so do the others. That's because a reindeer's cone-shaped nose contains dense capillary vessels carrying large amounts of blood, keeping the nose warm and often making it reddish.
"Rudolph's red nose is just brighter," Santa said.
A reindeer's circulatory system also keeps the legs warm while two layers of fur keep the body warm. The inner layer of fur acts like a wool blanket, and the outer layer has hollow hairs that retain air for insulation against winter wind, rain and snow.
Many generations of reindeer have pulled Santa's sleigh, all bearing the original names.
New generations begin with the mating season from September to November when males lock horns with each other and battle for the right to mate with females. The strongest males get more than 15 females for mates. But battling for breeding rights takes a toll on the males, as they stop eating and thin down to only 5 percent body fat.
Both males and females grow antlers, with the male's rack measuring up to 3 feet wide and 41/2 feet long. Most males shed their antlers by early December, whereas females retain their thin, delicate-looking antlers all year. Which raises a question about whether the antlered reindeer pulling Santa's sleigh are males or females?
"I never told anyone the reindeer were all males," Santa said. "Ever stop to think that Dancer, Prancer and Vixen could be females?"
But I still wondered how Santa gets his reindeers to fly.
"You know," Santa said, "flying reindeer are not the only miracle of Christmas."