Caribou Reindeer
Credit: AER Wilmington DE, Flickr

They don't get all that much press at other times of the year, but as they get ready to embark on their annual present-hauling mission, reindeer are very much in the spotlight. So what do you really know about Santa's favourite pack animals? Here are ten weird and wonderful facts about Rudolph and his kin. Merry Christmas!

(A note on naming: We use 'reindeer' here, but they're known by several other labels, including 'caribou' in North America. Names aside, they're all members of the same species, Rangifer tarandus.

1. They might be survivors from the last Ice Age, but modern-day climate change could wipe them out

The IUCN lists them as a species of least concern, but recent research suggests that climate change and the resulting loss of suitable habitat could spell trouble for the species. Some reindeer populations are likely to become more and more isolated, which is bad news for genetic diversity and therefore bad news for their ability to adapt and survive in a changing world. According to the research, certain reindeer subspecies will lose up to 90 percent of their habitat in the next 60 years. 

2. They have incredible shrinking hooves

The ‘shrinking’ hooves are all about adapting to the seasons. When winter turns the ground icy and hard, reindeer footpads respond by shrinking and tightening for better grip. In summer, the footpads become soft and sponge-like for extra traction in soft, wet earth.  

3. They’re masters of migration

Migration’s not for every reindeer, but those that do favour the nomadic life are pretty darn skilled at it. According to the IUCN, some North American populations may travel 5,000 km (3,000 miles) in a year, the longest documented movements of any terrestrial mammal.

4. They swim like pros

If a body of water requires crossing on that extensive migratory route, reindeer are more than ready for the challenge. When swimming, adults can maintain a speed of 6.5 kpmh (4 mph) ... or even 10 kmph (6 mph) if there's a hurry.


5. The entire body of a reindeer was once found INSIDE a Greenland shark

Yes, this fact is less about reindeer and more about the adventurous eating habits of the Greenland shark … but it’s true nonetheless. The sharks are known for feeding on carrion and are attracted to the smell of rotting meat floating in the water, so the reindeer meal was most likely a scavenge on the shark's part. (Other unusual things inside found Greenland shark stomachs? Polar bears, horses and moose!)

6. They’re mostly committed vegetarians, but sometimes they eat lemmings (and magic mushrooms!)

When they’re not feasting on Christmas fare up at the North Pole, reindeer need to keep themselves well fed in order to survive in the extreme and barren environments they often call home (like the Arctic tundra). Most of the time, grasses, leaves and lichens (reindeer moss Cladonia rangiferina is a favourite) do the trick. But sometimes, reindeer opt for a little supplementation. There’s evidence that lemmings (those adorable little rodents plagued by that infamous mass-suicide myth) form part of reindeer diets in summer. And then there are reindeer snacks of the psychedelic kind … at least according to one theory. Some mycologists (mushroom specialists) claim the classic story of Santa and his flying reindeer has its roots in ancient shamanic ceremonies: reindeer would munch on hallucinogenic mushrooms and Sami shamans would then drink the filtered reindeer urine ... the resulting 'high' made them believe the animals were 'flying'. 

7. Come Christmas, their eyes change colour

Aah, those reindeer and their crazy chameleon eyes! Earlier in 2013, a research team that included a neuroscientist from University College London specialising animal vision revealed why reindeer eyes are golden in summer and deep blue in winter. So what's that colour-changing secret? In summer, the golden glow of reindeer eyes is due to the light-reflecting tapetum lucidum or cat’s eye (a mirrored layer situated behind the retina). But in the fading light of winter, the tapetum undergoes a complex transformation (details here) that changes the type of light it can reflect – and also gives it a blue appearance.  

8. Reindeer parasites are a little terrifying

We're talking myiasis ... also known as parasitic infestation by fly larvae. In the case of reindeer, the culprit is Hypoderma tarandi (aka warble fly). The flies deposit their eggs on reindeer fur, and when the larvae hatch, they shimmy down the hair shaft, burrow under the reindeer's skin and wriggle about until they find a suitable spot to hunker down for a cozy winter. (And just in case you think myiasis is a reindeer thing, you should know you're very wrong. Myiasis is common. Humans are not immune.)

9. Way before Santa and his sleigh, reindeer and flying went together
Reindeer Stones
Credit: Alix Guillard, Wikimedia Commons

In his book ‘The Reindeer People’, anthropologist Piers Vitebsky looks back through ancient history to trace the link between reindeer and flight in much older cultures and mythologies. Amongst the evidence are ‘reindeer stones’ dating back thousands of years to the Bronze Age. The upright stones, scattered all over the world but concentrated in Siberia and Mongolia, are carved with various animals, but most often with reindeer. Vitebsky writes:

On these stones, the reindeer is depicted with its neck outstretched and its legs flung out fore and aft, as if not merely galloping but leaping through the air. The antlers have grown fantastically till they reach right back to the tail, and sometimes hold the disc of the sun or a human figure with the sun as its head. The flung-out hooves seem to represent more than just a leap: it is as if the artist has caught the reindeer in the act of flying through the sky in an association with a deity of the sun.

10. Santa’s sleigh runs on girl power (probably)

Unlike other members of the deer family, both male and female reindeer grow antlers in most populations. But when it comes to figuring out whether Santa’s sleigh is pulled by Rudolph or Rhonda, the key thing is when those antlers are shed. The argument for an all-female pulling team is based on the fact that older male reindeer usually shed their antlers in early December – which would leave them antlerless at Christmas (and Santa’s reindeer are always depicted with head gear on show). In contrast, female reindeer shed their antlers well into the spring, which makes them far better contenders for Santa’s sleigh. But there are other options to consider. The shedding cycle is affected in males that are neutered and younger male reindeer can delay their antler-shedding until April ... so there's hope for Rudolph after all.

Top header image: Patti Haskins, Flickr