The reindeer is one of the most iconic animals of the cold northern hemisphere. Known as the caribou in North America, this large mammal is perfectly adapted to Arctic and sub-Arctic environments and plays a key ecological, cultural, and economic role for many northern communities.
From changing eye color to clicking knees and legendary journeys across snowy landscapes, reindeer have a lot of surprising traits. Here are 10 of the most interesting reindeer facts.
1. What do reindeer eat?
In winter, when the ground is buried under deep layers of snow and ice, reindeer rely on their highly developed sense of smell to detect and dig up lichens beneath the snow.
These lichens are the main food source in the coldest months.
They provide enough energy and nutrients to survive temperatures that can drop below –40 °C.
In summer, when the tundra bursts back to life, reindeer dramatically change their diet. They feed on:
Grasses and herbs
Leaves and tender shoots
Wildflowers
Fungi (mushrooms)
The short Arctic summer is their opportunity to regain body weight, build up fat reserves and recover from the harsh winter.
2. How are reindeer different from moose?
Reindeer and moose both belong to the deer family (Cervidae), but they represent very different branches of that family tree.
Reindeer (caribou) are adapted to the open Arctic and sub-Arctic, from Scandinavia and Siberia to Alaska and northern Canada.
Moose prefer boreal forests, wetlands and shrubby areas, where they can browse leaves, twigs and aquatic plants.
Social life and behavior
Reindeer live in large herds and are famous for their long migrations, covering hundreds or even thousands of kilometers each year.
Moose are mostly solitary, more territorial and move more slowly, often staying within a fairly fixed home range.
Size and appearance
Moose are the largest deer species on Earth, reaching up to 2.1 m at the shoulder and often exceeding 600 kg. Their antlers are broad, flat and shovel-like, sometimes more than 1.5 m across and over 20 kg in weight.
Reindeer are smaller and more compact, with shorter legs and lighter bodies, better suited to moving quickly and efficiently over deep snow.
3. Do reindeer eyes really change color?
Yes – and it’s one of their most remarkable adaptations to life in the far north.
In summer, when the sun can shine almost 24 hours a day, reindeer eyes appear golden-brown. This color helps reflect and control the intense light, reducing glare while they graze under the midnight sun.
In winter, when darkness dominates for weeks, their eyes shift to a deep blue tone.
This color change affects the tapetum lucidum, the reflective layer at the back of the eye. The winter “blue mode” reflects less light back out of the eye and instead scatters more light inside the retina. That increases light sensitivity and helps reindeer detect even very faint contrasts in the dim Arctic twilight — almost like a natural night-vision upgrade.
4. How many types of reindeer are there?
Scientists recognize more than 9 subspecies of reindeer within the species Rangifer tarandus. Broadly, they are split into two big groups:
Eurasian reindeer – found in Scandinavia and Russia
North American caribou – living in Alaska, Canada and parts of Greenland
Although people often use “reindeer” and “caribou” as if they were different animals, they’re actually the same species. The difference lies in region and lifestyle:
In Eurasia, they are usually called reindeer, and many populations are semi-domesticated, herded and managed by Indigenous peoples for transport, meat, milk and hides.
In North America, wild populations are generally known as caribou, from a Mi’kmaq word meaning “the one who scratches the snow”, referring to their habit of scraping away snow to reach lichens.
There are also size and antler differences:
Domestic reindeer are often smaller, calmer and more compact, shaped by centuries of human management.
Wild caribou herds in Alaska and Canada tend to have larger bodies and more impressive antlers, as they have not undergone the same domestication process.
5. What is the ecological role of reindeer?
Reindeer and caribou play a crucial role in Arctic and sub-Arctic ecosystems. As they migrate across vast territories, they:
Fertilize the soil with their droppings, adding nutrients to otherwise poor tundra soils.
Transport seeds in their fur and feces, helping plants to colonize new patches of ground.
Serve as a key food source for predators such as wolves and bears.
In many northern food webs, reindeer are a keystone species: if their populations decline or their migration routes are disrupted, it can have cascade effects on predators, vegetation and even local human communities.
6. How are reindeer different from “typical” deer?
When people think of deer, they often imagine red deer, white-tailed deer or roe deer living in forests and meadows. Reindeer are quite different in both build and lifestyle.
Deer (general)
Live in a wide range of habitats: temperate forests, grasslands, mountains and even urban edges.
Tend to be more slender and fast, built to move quickly through forests and escape predators.
Have a lighter coat that is not as specialized for extreme cold.
Enjoy a varied diet available all year in many regions: leaves, fruits, shoots and agricultural crops.
Reindeer
Are specialists in extreme cold.
Have a stockier body, shorter legs and broad hooves, ideal for walking over snow and ice without sinking.
Their fur is very dense and hollow, trapping warm air for insulation, and they carry a thick layer of fat for additional warmth.
While other deer look for shelter in harsh winter storms, reindeer are built to thrive in them.
7. Are reindeer masters of navigation?
Some herds of caribou in northern Canada and Alaska travel more than 5,000 km a year, crossing frozen rivers, mountain ranges and vast tundra that, to human eyes, all look almost identical.
Despite the lack of obvious landmarks, these herds:
Use a combination of memory, environmental cues and possibly the Earth’s magnetic field to stay on track.
Return to the same calving and feeding grounds year after year, following ancient migration routes.
Their orientation and endurance make reindeer some of the greatest migratory mammals on the planet.
8. Do reindeer really make clicking sounds with their knees?
Yes – and it’s not a defect; it’s a clever adaptation.
When reindeer walk, their leg joints produce a distinct “click” or “clack” noise with each step. This sound:
Helps individuals keep track of each other inside the herd when visibility is poor — for example, during snowstorms or in the polar night.
Acts almost like an acoustic GPS, allowing them to follow the group even when they can’t clearly see their neighbors.
In the endless white of the Arctic, where sight is often limited, this clicking is a simple but effective communication tool.
9. Does a reindeer’s nose warm the air it breathes?
Another impressive cold-weather adaptation hides in the nose. A reindeer’s nasal passages act as a natural heat exchanger:
When they inhale icy air, it passes through a complex network of narrow passages and blood vessels.
Warm blood heats the incoming air and adds moisture, protecting the lungs from extreme cold.
When they exhale, part of the heat and moisture is recaptured, so they lose less energy with each breath.
This system helps reindeer avoid heat loss and dehydration in extremely dry, freezing air – a vital trick for surviving Arctic winters.
10. What is the connection between reindeer, Christmas and northern legends?
Today, reindeer are global Christmas icons, thanks to stories of Santa’s sleigh racing across the night sky. But their cultural importance in the north is much older than modern Christmas traditions.
For many Indigenous peoples of the Arctic, such as the Sámi and other northern communities, reindeer have long been considered sacred animals.
They were seen as spiritual guides, connecting the earthly world with the sky, capable of traveling between realms thanks to their strength and endurance.
Over time, these ancient winter myths and the figure of the reindeer merged with Christian and modern festive stories.
In the 19th and 20th centuries, literature, poems and later advertising and films transformed the reindeer into Santa Claus’s flying helpers, pulling a magical sleigh loaded with gifts.
Behind the colorful lights and Christmas songs, the reindeer remains a powerful symbol of:
Adaptation to harsh environments
Nobility and endurance
The deep cultural connection between people and wildlife in the far north
Reindeer are much more than Christmas characters: they are expert navigators, Arctic survivors and key players in northern ecosystems and cultures. The more we learn about them, the easier it is to understand why they’ve captivated both scientists and storytellers for generations.
Bibliography
Rothschuh, U. (December 13, 2024). Reindeer or Caribou. BIOenciclopedia. Available at: https://www.bioenciclopedia.com/reno-o-caribu-1067.html
Fun Facts About Reindeer - Things You Didn't Know About Reindeer. The Thousand Answers. Available at: https://lasmilrespuestas.blogspot.com/2009/05/curiosidades-sobre-los-renos.html
Miller, M. L. (November 26, 2024). Real Reindeer Are More Amazing Than You Imagine. Nature. Available at: https://www.nature.org/es-us/participa/como-ayudar/animales-que-protegemos/renos-de-verdad-mas-increibles-que-imaginas/
Romero H., N. A. February 5, 2025. ExpertAnimal. What do reindeer eat? Available at: https://www.expertoanimal.com/que-comen-los-renos-27389.html
