Did you hear the prancing of little hooves on your roof the other night? If that noise was followed by the sound of someone sliding down the chimney, the hooves probably belonged to reindeer. And they weren't just tapping their feet because they were cold: Reindeer never get cold. They were pawing for their favorite food, a many-branched grey lichen called reindeer moss. If you left them cookies and milk instead, it's time you learned what reindeer are really like. That way you'll be prepared next year and will be a more gracious host.

First, take a field trip to the Ellipse where nine reindeer are available for closer scrutiny than you can achieve by craning your neck out the window on Christmas Eve. The first thing that will strike you about them is that, although they have names like Cupid and Vixen, they don't look anything like the reindeer in all those animated Christmas specials we just got deluged with. They look rather lovable in a shaggy sort of way, but they don't have turned-up noses or fluttering eyelashes -- not even the females. In fact, it's pretty hard to tell the sexes apart. Unlike other deer, reindeer of both sexes grow antlers.

Only Santa Claus can make reindeer fly, but the Lapps of northern Scandinavia have been making a living from reindeer for thousands of years. Reindeer provide them with milk, meats, hides for tents and clothing, transportation and money.

In return for all this, the Lapps go where the reindeer want to go, following the herds to where the lichens are lush and the insects few. The Lapps make the seasonal treks in boat-shaped sleds called pulkas pulled by reindeer. Nowadays they also use snowmobiles, mainly to track down stray deer.

The main social event in Lapland is the annual mid-winter roundup festival, which features reindeer races. The reindeer sometimes pull sleds, sometimes skiers. And although they don't fly in the over-the-rooftops sense, they do go fast. A reindeer once beat the time of Finland's fastest racehorse, covering 2,000 meters in 2:56.8.

Although the Lapps live on reindeer meat, Lapp children also keep reindeer as pets. Lapp children believe that their Santa, Joulupukki, borrows every pet reindeer in Lapland for his Christmas Eve ride. But he always returns the pets before their young owners wake up Christmas morning.

Reindeer today live only near the Arctic. Circle -- the North Pole. But during the Ice Age, they wandered as far south as what is now France and Spain where Ice Age artists etched their impressions of reindeer in caves. At about this time, reindeer probably wanderd across a land bridge into what is now Alaska. But when white settlers came to North America, they found a taller, heavier variety of deer, which they called caribou.

Never tamed, the caribou were hunted almost to extinction by European settlers and Indians. But in the late 19th century, Alaska's deer population got a boost. An alert bureaucrat, alarmed because commercial whaling was pricing whale meat out of the Eskimos' range, thought reindeer ranching might provide an alternative food source. This technical aid program not only brought reindeer to Alaska but also Lapps -- to teach herding skills to the Eskimos. The program was a great success, and Alaska now has a healthy reindeer herd.

More recently, in 1977, Finland repeated the gesture on a smaller scale by presenting two reindeer, Salla and Anta, to Amy Carter, who turned them over to the National Zoo. Salla and Anta are now on the Ellipse and with the rest of the deer will return to the zoo after the Pageant of Peace ends. The other deer, who have those Clement Moore names only around this time of year, are descendants of a herd presented to President Eisenhower by Alaska when it became a state.

At the zoo, the reindeer live on a diet of hay, grains and vegetables. So it might be a good idea to lay in a supply of those items for next Christmas, in case your local gourmet delly doesn't stock reindeer moss. In fact, it might be a good idea to pay periodic visits to the reindeer off-season. Reindeer aren't exactly the zoo's star attraction, but drop by anyway. In spring, baby reindeer are born -- friskly, dark-brown fawns. By next Christmas fawns born in the spring will be almost full-grown, big enough to pull Santa's sled. If they've seen you at the zoo, maybe they'll put in a good word for you with Santa.