Beyond their sled-pulling capabilities and discrimination against those with red noses, what do you really know about reindeer?

1. Reindeer and caribou are the same thing.

Historically, the Eurasian reindeer and American caribou were considered to be different species, but they are actually one and the same: Rangifer tarandus. There are two major groups of reindeer, the tundra and the woodland, which are divided according to the type of habitat the animal lives in, not their global location. The animals are further divided into nine to 13 subspecies, depending on who is doing the classification. One subspecies, the Arctic reindeer of eastern Greenland, is extinct.

2. Reindeer have several names.

Reindeer comes from the Old Norse word hreinin, which means "horned animal.” Caribou comes from Canadian French and is based on the Mi'kmaq word caliboo, meaning “pawer” or "scratcher," in reference to the animal’s habit of digging through the snow for food.

3. Santa’s reindeer are most likely R. tarandus platyrhynchus, a subspecies from Svalbard.

pum_eva/iStock via Getty Images

Clement C. Moore’s poem, "A Visit from Saint Nicholas,” introduced the world to Santa’s reindeer and describes them as "tiny." The only reindeer that could really be considered tiny are the Svalbard subspecies, which weighs about half as much as most reindeer subspecies and are at least a foot shorter in length. That may prove useful when landing on roofs.

Strangely, you’ll almost never see these guys in depictions of Santa. Live-action films usually use full-sized reindeer and animations usually draw the creatures as a cross between a white-tailed deer and a reindeer.

4. It’s not always easy to tell the sex of a reindeer.

In most deer species, only the male grows antlers, but that’s not true for most reindeer. Although the females in certain populations do not have antlers, many do. During certain times of year, you can still tell the sex of a reindeer by checking for antlers. That’s because males lose their antlers in winter or spring, but females shed theirs in the summer.

5. Santa’s reindeer may or may not be female.

Since reindeer shed their antlers at different points of the year based on their sex and age, we know that Santa’s reindeer probably aren't older males, because older male reindeer lose their antlers in December and Christmas reindeer are always depicted with their antlers. Female Svalbard deer begin growing their antlers in summer and keep them all year. That means Santa’s sled either has to be pulled by young reindeer, constantly replaced as they start to age, or Santa’s reindeer are female.

6. Reindeer were originally connected to Santa through poetry.

Before Moore wrote “A Visit from Saint Nicholas” (a.k.a. “The Night Before Christmas”) in 1823, no one thought about reindeer in conjunction with Santa Claus. Moore introduced the world to Dasher, Dancer, Prancer, Vixen, Comet, Cupid, Dunder and Blixem (the last two of which were later changed from Dutch to German, becoming Donner and Blitzen). While the first six names all make sense in English, the last two in German mean “thunder” and “flash,” respectively.

As for little Rudolph, he wasn’t introduced until catalog writer Robert L. May wrote a children’s book in verse for his employer, Montgomery Ward, in 1939 titled “Rudolph the Red-Nosed Reindeer.”

7. Reindeer are the only mammals that can see ultraviolet light.

Humans can see light in a range of wavelengths, from about 700 nanometers (in the red spectrum) to 400 nanometers (in the violet spectrum). Reindeer can see light to 320 nanometers, in the ultraviolet (UV) range. This ability lets reindeer see things in the icy white of the Arctic that they would otherwise miss—kind of like viewing the glow of a white object under a blacklight. Things like white fur and urine are difficult, even impossible, for humans to see in the snow, but for reindeer, they show up in high contrast.

8. Reindeer evolved for life in cold, harsh environments.

Geoffrey Reynaud/iStock via Getty Images

Life in the tundra is hard, but reindeer have it easy-ish thanks to their amazing evolutionary enhancements. Their noses are specially adapted to warm the air they breathe before it enters their lungs and to condense water in the air, which keeps their mucous membranes moist. Their fur traps air, which not only helps provide them with excellent insulation, but also keeps them buoyant in water, which is important for traveling across massive rivers and lakes during migration.

Even their hooves are special. In the summer, when the ground is wet, their foot pads are softened, providing them with extra grip. In the winter, though, the pads tighten, revealing the rim of their hooves, which is used to provide traction in the slippery snow and ice.

9. some reindeer migrate longer distances than any other land mammal.

A few populations of North American reindeer travel up to 3100 miles per year, covering around 23 miles per day. At their top speed, these reindeer can run 50 miles per hour and swim at 6.2 miles per hour. During spring, herd size can range from 50,000 to 500,000 individuals, but during the winter the groups are much smaller, when reindeer enter mating season and competition between the bucks begins to split up the crowds. Like many herd animals, the calves learn to walk fast—within only 90 minutes of being born, a baby reindeer can already run.

10. Reindeer play an important role in Indigenous cultures.

In Scandinavia and Canada, reindeer hunting helped keep Indigenous peoples alive, from the Mesolithic and Neolithic periods all the way through modern times. In Norway, it is still common to find reindeer trapping pits, guiding fences, and bow rests dating from the Stone Age. And in Scandinavia, reindeer is still a popular meat, sold in grocery stores in fresh, canned, and dried forms. Almost all of the animal’s organs are edible and many are crucial ingredients of traditional dishes in the area. In North America, Inuit rely on caribou for traditional food, clothing, shelter, and tools.

11. Reindeer used to live farther south.

Reindeer now live exclusively in the northern points of the globe, but when Earth was cooler and humans were less of a threat, their territory was larger. In fact, reindeer used to range as far south as Nevada, Tennessee, and Spain during the Pleistocene area. Its habitat has shrunk considerably in the last few centuries. The last caribou in the contiguous United States was removed to a Canadian conservation breeding program in 2019.

As for how Santa's nine reindeer manage to fly while pulling a sled carrying presents for every child in the whole world, science still hasn’t worked that out.