Caribou

Rangifer tarandus

The caribou or reindeer (Rangifer tarandus) is a deer of the Arctic and subarctic: tundra, mountains and northern forests across North America, Greenland, Europe and Asia. Wild herds in North America are called caribou, while in Europe and Asia the same species is called reindeer, and millions of reindeer are herded by northern peoples. It is the only deer in which females normally grow antlers, and some herds make the longest known migrations of any land animal.

Also known as Wild reindeer, Reindeer

Caribou abilities

Both sexes grow antlers
Caribou are the only deer in which cows normally grow antlers too. Big bulls drop theirs after the autumn rut, but pregnant cows keep theirs all winter.
- New antlers start in spring and are finished by late August. Big bulls rub off the velvet in late August and early September, just before the rut.
- The biggest bulls shed their antlers from late October to December.
- Young bulls and cows that are not pregnant keep theirs until about April. Pregnant cows usually keep theirs until their calves are born in late May or early June.
Sources [1, 2, 14]
Gold → blue eyeshine, summer to winter
A reindeer’s eyeshine changes colour with the seasons: golden in the endless summer light, deep blue in the long winter twilight.
- The mirror behind the retina is made of tiny collagen fibres. In winter they sit closer together, so the mirror reflects bluer light.
- The blue mirror sends less light back out of the eye, and the retina becomes more sensitive in dim light.
- Scientists think pupils that stay wide open all winter raise the pressure inside the eye, and this squeezes the fibres closer.
- Reindeer are the only mammal known to retune their eyes to the season like this.
Sources [4, 5]
UV light reaches the retinaStill debated
A reindeer’s cornea and lens do not block all ultraviolet light, and its retina responds to it. What reindeer use this for is still an open question.
- Both rods and cones respond to UV, even though reindeer have no special UV-sensing cells.
- The Arctic is rich in UV light, scattered by the sky and bounced off snow and ice, especially in the long twilights of spring, autumn and winter.
- Scientists suggest UV vision may help reindeer pick out things that reflect UV differently from snow, such as some plants. This has not been tested in the wild.
Sources [6]
Click with every stepStill debated
Walking reindeer make a loud clicking sound with each step, and both bulls and cows do it.
- Park rangers in Alaska say tendons in the feet click as caribou walk.
- Scientists call it a “knee-click”. Reindeer are one of only a few hoofed animals that click loudly and regularly, along with Père David’s deer, white-lipped deer and eland.
- Exactly where the sound comes from is not proven. A 2022 study found a small oval opening in a tendon sleeve of the front leg that might play a part.
- In eland, clicks tell rivals how big a male is. Whether reindeer clicks help a herd keep together has not been tested.
Sources [10, 15]
“The one who paws” possible meaning of “caribou”
In winter, caribou dig through the snow with their broad hooves to reach the lichen underneath.
- Their concave hooves work as scoops as they paw through snow to uncover lichens and other plants.
- The name “caribou” may come from the Mi’kmaq word xalibu, “the one who paws”.
- Winter is the hungriest season. Caribou move less then than at any other time of year, saving energy.
- When rain falls on snow and freezes, an ice crust can seal the food away. In winter 2013–14 this starved 61,000 herded reindeer on Russia’s Yamal Peninsula.
Sources [2, 13, 16, 17]
+6 °C breath out when the air is −45 °C
A reindeer’s nose and coat are built to keep heat in. At −45 °C, its breath leaves the nose at only about +6 °C.
- Arteries and veins in the nose lining run side by side in opposite directions, so heat from outgoing breath is caught and kept in the body.
- In summer the system can switch to get rid of heat: on a +29 °C day, breath left the nose at +38 °C.
- The hair is hollow and holds heat, and the thick coat even helps a caribou float.
Sources [8, 9, 10, 11]
≈1,350 km longest round trip, straight line
Some caribou herds make the longest known migrations of any land animal: about 1,350 km in a straight line between their summer and winter ranges and back.
- A 2019 study compared migrations of big land mammals. Caribou and reindeer herds took the top six places; the Bathurst and Porcupine herds were longest, at about 1,350 km.
- That is the straight line. Following every twist and turn, caribou in northern North America moved up to 4,868 km in a year, though grey wolves moved even more.
- Once on the move, caribou can travel up to 50 miles (80 km) in a day.
- The Bathurst herd used to migrate up to 1,500 km; as the herd shrank, so did its journey.
Longest round-trip migrations
Caribou (Bathurst herd)≈1,350 km
Grey wolf (Northwest Territories)≈1,016 km
Mule deer (Wyoming)≈772 km
Wildebeest (Serengeti)≈650 km
Moose (Alaska)≈392 km
Straight-line distance between the two ends of the migration, there and back.
Sources [1, 18]
2 seasons long rims in winter, worn down in summer
Caribou hooves change through the year. In winter they grow long, with sharp edges that bite into crusty snow and ice; in summer, rocks wear them down again.
- The sharp hoof edges give a firm grip on ice and smooth rock.
- Wide-splayed toes and big dewclaws spread the weight on snow and boggy tundra.
- Hooves are made of keratin, the same stuff as your nails, and the pads and hooves flatten with each step to cushion it.
Sources [2, 12]

Tap a pin on the model or a part below.

≈1 m tall: 3 ft or more
- Caribou are the only deer in which both sexes grow antlers. A bull’s are large and massive; a cow’s are shorter, thinner and more irregular.
- Antlers grow from spring to late August under a fuzzy skin called velvet, full of blood vessels that carry food for growth.
- In Denali National Park, antlers of both bulls and cows can stand 3 feet (about 1 m) or more high.
Sources [1, 2, 3]
Gold → blue eyeshine, summer to winter
- Behind the retina is a mirror layer, the tapetum lucidum. In summer it shines gold; in the dark Arctic winter it turns deep blue.
- The blue winter mirror goes with a more sensitive retina, which helps in the long blue twilight of the Arctic winter.
- A reindeer’s cornea and lens let some ultraviolet light through, and its retina responds to it.
- Reindeer may not need a strong daily body clock: in their cells two key clock genes barely keep a daily rhythm, and the sleep hormone melatonin simply follows light and dark.
Sources [4, 5, 6, 7]
- Inside the nose, networks of arteries and veins run side by side, so heat from each breath out is caught before it escapes.
- In a winter test at −45 °C, a resting reindeer’s breath left its nose at only about +6 °C. That saves heat and water.
- In warm weather the blood flow switches round so the nose can get rid of heat instead.
Sources [8, 9]
Lichen main winter food
- In summer caribou eat grasses and other low-growing plants. In August they feed heavily on willow leaves and mushrooms to put weight back on.
- From September they switch to lichens (“reindeer moss”), dried sedges and small shrubs such as blueberry.
- By grazing and browsing, caribou help shape the plant and lichen communities they live in.
Sources [1, 10]
- In autumn a bull has a rich brown or grey and white coat and a fringe of white hair flowing from throat to chest.
- Bulls only call during the rut, and their voice is more “airy” than a cow’s.
- Cows and calves are the chattiest, calling to keep in touch, especially around calving.
Sources [1, 2]
Hollow hairs that hold heat
- Caribou hair is hollow and holds heat well.
- The thick, many-layered coat keeps out the weather and even helps a caribou float when it swims.
- Newborn calves have dark chocolate to reddish-brown hair.
Sources [1, 10, 11]
4 toes on each foot
- Large, concave hooves splay wide to carry a caribou over snow and soft tundra, and work as paddles when it swims.
- In winter the hooves grow long, with sharp edges that grip crusty snow, ice and smooth rock. In summer, rocks and hard ground wear them down.
- Each foot has 4 toes: 2 big hoofed toes and 2 large dewclaws set far back, which spread the weight even more.
- With every step, the foot pads and hooves spread and flatten to cushion the blow.
Sources [1, 2, 12]
- Caribou are cud-chewers, like cows. Their food is fermented in a big first stomach called the rumen.
- Ground and tree lichens are their main winter food. Living on lichen sets caribou apart from all other large mammals.
- Lichens are easy to digest and rich in energy, and this lets caribou survive on harsh northern ranges.
Sources [2, 13]

Real caribou and reindeer

Photos from Wikimedia Commons. Some of them can repaint the 3D model.

BullAdult male, 159–182 kg on average (up to 318 kg recorded), with large, massive antlers and, in autumn, a white fringe from throat to chest.Drops his antlers after the autumn rutA bull caribou in Alaska. Photo: Dean Biggins, U.S. Fish and Wildlife Service, Public domain
Cow with calfCalves are born dark brown to reddish brown in late May or June, weighing about 6 kg, and double their weight in 10–15 days.One calf a year; twins are very rareA cow, still wearing her antlers, and her calf on the winter solstice, Brooks Range, Alaska. Photo: BLM Alaska, Public domain
CowAdult female, 80–120 kg, with shorter, thinner and more irregular antlers.Pregnant cows keep their antlers until their calf is bornA female reindeer with antlers near Lake Khövsgöl, Mongolia. Photo: Bernard Gagnon, CC0
Peary caribouThe smallest North American caribou: mostly white, with a slate-grey back and a grey stripe down the front of the legs. Some look almost all white in winter.About 13,200 adults; Threatened in Canada (COSEWIC 2015)Peary caribou on Bathurst Island, Nunavut, Canada. Photo: Paul Gierszewski, CC BY-SA 4.0
Peary caribouThe smallest North American caribou: mostly white, with a slate-grey back and a grey stripe down the front of the legs. Some look almost all white in winter.About 13,200 adults; Threatened in Canada (COSEWIC 2015)A Peary caribou swimming the Thomsen River, Aulavik National Park, Canada. Photo: Paul Gierszewski, CC BY-SA 4.0
Part of a herd of about 60,000 Porcupine caribou in the British Mountains, Yukon, 1972Photo: Lee E Harding, CC BY-SA 4.0
A reindeer in the Kebnekaise valley, Swedish LaplandPhoto: Alexandre Buisse (Nattfodd), CC BY-SA 3.0
A wild caribou in Denali National Park, Alaska, late AugustPhoto: Diego Delso, CC BY-SA 4.0
Herded reindeer at Ljungris, Härjedalen, Sweden, in OctoberPhoto: Arild Vågen, CC BY-SA 4.0

Caribou by the numbers

Measured by wildlife agencies and scientists, with comparisons you can picture.

Bull weight: 159–182 kg; average adult bull; up to 318 kg recorded⁠[1]
Cow weight: 80–120 kg; average adult cow⁠[1]
Weight at birth: 6 kg; and doubles in 10–15 days⁠[1]
Antler height: ≈1 m; 3 ft or more, in bulls and cows⁠[3]
Longest round-trip migration: ≈1,350 km; Bathurst and Porcupine herds, straight line⁠[18]; Caribou1,350 kmSerengeti wildebeest650 km
Distance in a year: up to 4,868 km; caribou in northern North America, every step counted⁠[18]
Distance in a day: up to 80 km; 50 miles a day when migrating⁠[1]
Breath temperature: +6 °C; leaving the nose when the air is −45 °C⁠[8]
Wild tundra caribou and reindeer: 2.1 million; down 56% from 4.7 million in about 20 years (2018)⁠[20]
Herded reindeer: ≈3.4 million; kept by about 24 peoples in 10 countries⁠[21]

Caribou and reindeer: myth or fact?

Tap Myth or Fact for each claim, then check the answer.

0 of 8 answered

“Caribou and reindeer are two different animals.”
“Female reindeer grow antlers too.”
“Reindeer can fly.”
“Santa’s antlered reindeer must all be girls, because males lose their antlers before Christmas.”
“Reindeer eyes change colour with the seasons.”
“Walking reindeer make a clicking sound.”
““Reindeer moss” is a moss.”
“Caribou make the longest migrations of any land animal.”

Caribou records

Superlatives and record holders, each checked against its source.

Longest land migration
≈1,350 km
Caribou (Bathurst and Porcupine herds)
round trip, measured in a straight line between the two ends⁠[18]
Only deer with antlered cows
Both sexes
Caribou and reindeer
the only member of the deer family in which both sexes grow antlers⁠[1, 2]
Only mammal that retunes its eyes
Gold → blue
Reindeer
the only mammal known to adapt its eyes each year to the blue winter twilight⁠[5, 4]
The only domesticated deer
≈3.4 million
Reindeer
semi-domesticated reindeer, herded in 10 countries⁠[22, 21]
One of the farthest walkers
4,868 km a year
Caribou
one of only 4 species in the 2019 study to pass 3,500 km in a year, with grey wolves, khulan and Arctic foxes⁠[18]
Smallest North American caribou
Small and pale
Peary caribou
lives only on the islands of the Canadian Arctic⁠[19]

A caribou’s year

Calving, bugs, the rut and a long winter on lichen. Dates are for Alaska and northern Canada and shift a little from herd to herd.

Late May–June
Calves are born
Herds return to the same calving grounds year after year. Cows give birth to one calf each, almost all within a short time, so predators cannot eat them all.⁠[1]
Late May–June
Cows drop their antlers
Pregnant cows, who kept their antlers all winter, shed them around the time their calves are born.⁠[14]
June–July
Insect season
Huge groups gather on windy mountains and coasts, where wind and cool air keep mosquitoes and warble flies away.⁠[1]
August
Feasting
As insects die back, caribou spread out and feast on willow leaves and mushrooms. New antlers are finished by late August.⁠[1, 2]
Late Aug–September
Velvet off
Big bulls rub off their velvet, and the autumn migration begins. Bulls may carry more than 3 inches (7.6 cm) of fat on the back and rump for the rut.⁠[1]
September–October
The rut
Bulls spar, then fight for cows. In Alaska’s Western Arctic Herd the main rut is in mid to late October.⁠[1, 3]
Late Oct–December
Bulls drop their antlers
The biggest bulls shed their antlers after the rut.⁠[1, 2]
Winter
Lichen and low power
Caribou paw through snow for lichens and move less than at any other time of year to save energy.⁠[2, 13]
April
A new start
Young bulls and cows without calves shed their antlers, and new antlers begin to grow in spring.⁠[1, 2]

The great caribou migration

Many big herds walk between calving grounds on the tundra and winter ranges, often in the forest further south. Smaller herds may not migrate at all.

≈1,350 km
longest round trip
The Bathurst herd (Canada) and the Porcupine herd (Alaska and Yukon), measured in a straight line between the ends of their migration.⁠[18]
Top 6
places for caribou and reindeer
In a 2019 comparison of land migrations, caribou and reindeer herds held the top six. Next came a grey wolf population that follows caribou, at 1,016 km.⁠[18]
4,868 km
walked in a year
The real path, with every twist and turn, is far longer than the straight line.⁠[18]
>500 km
winter range shift
Between 2012 and 2020 Alaska’s Western Arctic Herd moved its main winter range more than 500 km, from coastal tundra to mountains further east, in one of the fastest-warming places on Earth.⁠[24]
1,500 → 1,250 km
shorter trips for a smaller herd
The Western Arctic Herd migrated about 1,500 km at its peak of nearly 500,000 animals around 2003, and about 1,250 km once its numbers had halved.⁠[18]

Each herd is defined by its own calving ground, though different herds may mix in winter.

Reindeer and herding peoples

Reindeer are the only deer that people have domesticated. Herding is a way of life, a source of food and clothing and a deep part of the culture of many northern peoples, from the Sámi of Norway, Sweden, Finland and Russia to the Nenets, Evenki and Chukchi of Siberia and the Dukha of Mongolia.

≈3.4 million
semi-domesticated reindeer
Kept by about 24 herding peoples in 10 countries: Norway, Sweden, Finland, Russia, Mongolia, China, Greenland, Canada, Alaska (USA) and Scotland.⁠[21, 25]
2 origins
for domestic reindeer
DNA shows reindeer were domesticated separately in Fennoscandia, by the Sámi, and in Russia.⁠[26]
Wild and tame
still side by side
Reindeer are still early in domestication: wild and herded reindeer live alongside each other across Eurasia.⁠[26]
61,000
reindeer lost to ice
After rain froze on the snow in November 2013, Nenets herders on the Yamal Peninsula lost 61,000 of about 275,000 reindeer to starvation that winter.⁠[17]

Herders and researchers say losing pastures to other land uses is the biggest challenge reindeer herding faces.

Caribou vs moose vs elk

Three big North American deer. Only one of them has antlered cows.

Caribou vs moose vs North American elk
	Caribou	Moose	Elk
Scientific name⁠[27, 28]	Rangifer tarandus	Alces alces	Cervus canadensis
Adult male weight⁠[1, 29, 28]	159–182 kg (up to 318 kg)	408–635 kg	≈318 kg
Adult female weight⁠[1, 29, 28]	80–120 kg	318–499 kg	≈227 kg
Antlers on females⁠[1, 29, 28]	Yes, normally	No	No
When bulls drop antlers⁠[1, 2, 29, 28]	Late October–December (big bulls)	Early winter	March–April
Young per birth⁠[1, 29]	1 calf (twins very rare)	Often twins, sometimes triplets	—
Longest migration (round trip)⁠[18, 28]	≈1,350 km	≈392 km (Alaska)	Seasonal moves to lower winter ranges

Moose are the largest members of the deer family. Caribou are the only deer whose cows normally grow antlers.

Are caribou endangered?

Worldwide, caribou and reindeer are Vulnerable. Millions remain, but many wild herds have shrunk fast since the 1990s.

IUCN Red List

Vulnerable (VU)

Population decreasing

Migratory tundra caribou and wild reindeer fell by 56%, from 4.7 million to 2.1 million, over about two decades. In 2018 only 2 of the 22 herds monitored were still at their peak.⁠[30, 27, 20]

IUCN Red List, 2016 assessment

Threats

Herds in steep decline>90%
Five herds in the Alaska–Canada region have fallen by more than 90% and show no sign of recovery.⁠[20]
Rain on snow61,000
Rain that freezes on snow locks lichen under ice. Icing caused a Peary caribou crash in the 1990s and starved 61,000 herded reindeer on Yamal in 2013–14.⁠[19, 17]
A changing climate
Scientists link falling survival of calves and adults to changing climate. Alaska’s Western Arctic Herd has moved its winter range by more than 500 km.⁠[20, 24]
Lost pastures
Herders and researchers say the loss of pastures to other land uses is the main threat to reindeer herding.⁠[21]

What’s helping

Counting and tracking
Biologists count herds each summer, when caribou gather in big groups, and follow them with GPS collars.⁠[1, 18]
Some herds bounce back+44%
The Porcupine herd grew 44% between 2001 and 2016, and Peary caribou recovered from 5,400 in 1996 to about 13,200 adults by 2015.⁠[20, 19]
Herders’ knowledge
Fieldwork with Nenets herders has helped scientists understand how ice, weather and sea-ice loss affect reindeer.⁠[17]

A caribou to know

Peary caribouNot Evaluated
In Canada, COSEWIC lists it as Threatened (2015): about 13,200 adults, down from 22,000 in 1987 after icing die-offs.⁠[19]

Caribou quiz

12 questions. Every answer is somewhere on this page.

Question 1 of 12Score 0

Which caribou grow antlers?

Caribou field notes

Diet, food web, safety and badges from the Snappit field guide.

Diet & Feeding

Caribou are herbivores that mostly munch on lichens, grasses, and small shrubs to survive.

Primary Foods

Lichen
Grasses
Sedges
Willow
Birch
Mushrooms
Foraging Method: Foraging

Ecological connections

Grey WolfEaten by
Main predator, often targeting calves or weaker individuals.
Grizzly BearEaten by
Opportunistic predator, especially on calves or during migrations.
WolverineEaten by
Preys on calves and scavenges caribou carcasses in winter.
Reindeer LichenDepends on
A critical winter food source, dug from under the snow.

Safety

Danger 2/5 · Low

Admire caribou from a safe distance and never approach them in the wild.

Traits

Collections

Mammals

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Family: Cervidae
Genus: Rangifer

Sources for these caribou facts

30 studies and references · checked Oct 16, 2026

Frequently Asked Questions

How to identify Caribou?

Compare ears, muzzle, tail, feet and coat markings. Size is hard to judge without something nearby for scale, and young mammals may not have adult coloring yet. Mammal Identifier: upload a photo and compare the visible details.

How long is Caribou?

120-220 cm

How much does Caribou weigh?

60-318 kg

How long does Caribou live?

10-15 years

What does Caribou eat?

Caribou are herbivores that mostly munch on lichens, grasses, and small shrubs to survive.

Where is Caribou usually found?

Tundra

How many babies does Caribou usually have?

1-2

Are caribou and reindeer the same animal?

Yes. Both are Rangifer tarandus. North Americans call wild ones caribou; in Europe and Asia the same species is called reindeer, and many reindeer are herded. Some scientists propose splitting the group into several species, but that is still debated.

Do female reindeer have antlers?

Yes. Caribou and reindeer are the only deer in which both sexes normally grow antlers. Cows’ antlers are smaller, and pregnant cows usually keep theirs until their calves are born in late May or June, long after big bulls have dropped theirs.

How far do caribou migrate?

The longest migrations, by the Bathurst and Porcupine herds, are about 1,350 km there and back in a straight line, the longest known for any land animal. Counting every twist and turn, caribou can walk up to 4,868 km in a year.

Why do reindeer eyes change colour?

The mirror layer behind the retina, the tapetum lucidum, is gold in summer and deep blue in winter. The winter version makes the eye more sensitive in the long blue twilight of the Arctic winter.

What do caribou eat?

In summer they eat grasses and other low-growing plants, then willow leaves and mushrooms. From September they switch to lichens (“reindeer moss”), dried sedges and small shrubs, and in winter they paw through snow to reach lichen.

Are caribou endangered?

The IUCN lists the species as Vulnerable. Wild tundra caribou and reindeer fell from 4.7 million to 2.1 million in about 20 years, and some herds have dropped by more than 90%, though a few, like the Porcupine herd, have grown.

Why do reindeer click when they walk?

Walking reindeer make a loud click with each step. Park rangers say tendons in the feet make the sound, and scientists are still working out exactly where it comes from and whether it helps a herd stay together.

Can reindeer see ultraviolet light?

Their eyes let some ultraviolet light through and the retina responds to it. Scientists think this may help in the UV-rich Arctic winter, but what reindeer actually use it for has not been tested in the wild.