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What the sources say

Reindeer (Caribou)Rangifer tarandus

Every figure, record and mechanism on the Reindeer (Caribou) profile was written from a source, and this is the working table behind it: 61 claims checked word for word against these sources. The left column is what the page says. The right column is the source's own words, copied, not paraphrased; a ... marks a cut and[brackets] an insertion. Open any source and check it yourself.

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Source
01

Alaska Department of Fish and Game 2025

Caribou (Wildlife Notebook Series). Alaska Department of Fish and Game, 2025.

The page saysthe only deer where cows grow antlers too
The source saysCaribou are the only member of the deer family (Cervidae) in which both sexes grow antlers.Note: tagline phrasing; moved from ADW (2000) to the ADF&G notebook (revised 2025)
The page saysis the only member of the deer family in which both sexes grow antlers
The source saysCaribou are the only member of the deer family (Cervidae) in which both sexes grow antlers.
The page saysIn Alaska, adult bulls average 350 to 400 pounds (159 to 182 kg)
The source saysWeights of adult bulls average 350-400 pounds (159-182 kg).Note: scoped to Alaska: the notebook describes Alaska's caribou ('Alaska has only the barren-ground subspecies') and follows the weights with how they vary across Alaska
The page saysthough weights of 700 pounds (318 kg) have been recorded
The source saysHowever, weights of 700 pounds (318 kg) have been recorded.
The page sayswhile mature cows average 175 to 225 pounds (80 to 120 kg)
The source saysMature females average 175-225 pounds (80-120 kg).
The page sayspregnant cows usually keep theirs until their calves are born in late spring
The source saysPregnant females usually retain their antlers until calves are born in late May or early June.
The page saysIn summer they eat the leaves of willows, sedges, flowering tundra plants, and mushrooms
The source saysIn summer (May-September), caribou eat the leaves of willows, sedges, flowering tundra plants, and mushrooms.
The page saysTheir large, concave hooves spread wide to hold them up on snow and soft tundra, like snowshoes, and work as paddles when they swim
The source saysCaribou have large, concave hoofs that spread widely to support the animal in snow and soft tundra. The feet also function as paddles when caribou swim.Note: 'like snowshoes' is a simile for the source's own mechanism (hooves that spread widely to support the animal in snow)
The page saysIn Alaska, large herds often migrate up to 400 miles between summer and winter ranges
The source saysLarge herds often migrate long distances (up to 400 miles/640 km) between summer and winter ranges.Note: scoped to Alaska: the notebook describes Alaska's herds, and FDA (2023) gives up to 1,000 miles for herds elsewhere, so 400 is not a species maximum
The page sayscovering up to 50 miles a day once they set off
The source saysOnce they decide to migrate, caribou can travel up to 50 miles a day.
The page saysthough smaller herds may not migrate at all
The source saysSmaller herds may not migrate at all.
The page saysWillow leaves, sedges, flowering tundra plants, and mushrooms in summer
The source saysIn summer (May-September), caribou eat the leaves of willows, sedges, flowering tundra plants, and mushrooms.Note: stats.diet

Source
02

Alaska Department of Fish and Game

Caribou. Alaska Department of Fish and Game.

The page saysCaribou live on Arctic tundra, mountain tundra, and in the northern forests of North America, Russia, and Scandinavia
The source saysCaribou live in the arctic tundra, mountain tundra, and northern forests of North America, Russia, and Scandinavia.
The page saysIn some areas, wolves, grizzly bears, and golden eagles kill large numbers of newborn calves
The source saysIn some areas, wolves, grizzly bears, and golden eagles kill large numbers of newborn calves.
The page saysCaribou swamp them: the cows in a herd give birth to a lot of calves in a very short time, more food than nearby predators can eat
The source saysCaribou “swamp” predators – the cows in a herd give birth to a lot of calves in a very short period of time, essentially overwhelming predators in the area with an overabundance of food.
The page saysArctic tundra, mountain tundra, and northern forests of North America, Russia, and Scandinavia
The source saysCaribou live in the arctic tundra, mountain tundra, and northern forests of North America, Russia, and Scandinavia.Note: stats.habitat

Source
03

U.S. Food and Drug Administration, Animal Health Literacy 2023

Fun Facts about Reindeer and Caribou. U.S. Food and Drug Administration, Animal Health Literacy, 2023.

The page saysCompared to body size, their antlers are the largest and heaviest of any living deer species
The source saysCompared to their body size, reindeer have the largest and heaviest antlers of all living deer species.
The page saysa bull's can be up to 51 inches long, and a cow's can reach 20
The source saysA male's antlers can be up to 51 inches long, and a female's antlers can reach 20 inches.

Source
04

Hinterland Who's Who, Canadian Wildlife Federation

Caribou. Hinterland Who's Who, Canadian Wildlife Federation.

The page saysmost cows carry a set
The source saysThis animal is unusual among deer family members in that most females, as well as males, carry antlers
The page saysThe large bulls lose theirs after the autumn mating season
The source saysThe large bulls lose their antlers after the autumn mating season
The page saysUsing lichens as their primary winter food sets them apart from all other large mammals and has let them survive on harsh northern range
The source saysThe ability of caribou to use lichens as a primary winter food distinguishes them from all other large mammals and has enabled them to survive on harsh northern rangeland.
The page saysWolves are the caribou's primary predator
The source sayswhich as prey species of the wolf, attract this primary predator of caribou
The page saysa wolf eats a variety of prey but needs food equal to 11 to 14 caribou a year
The source saysA wolf eats a variety of prey but requires food equivalent to 11 to 14 caribou a year.
The page saysGrizzly and black bears, cougars, wolverines, lynx, coyotes, and golden eagles also prey on caribou
The source saysOther predators of caribou include grizzly and black bears, cougars, wolverines, lynx, coyotes, and golden eagles.
The page saysIn danger, a caribou rears up on its hind legs and leaves a scent from glands at the base of its ankles that alerts other caribou
The source saysScent glands located at the base of the ankles are used when the caribou is in danger: the animal rears up on its hind legs and deposits a scent that alerts other caribou to the menace.
The page saysAntlers Mean Dominance
The source saysIn the deer family, antler size means dominance.Note: blockquote lead-in
The page saysBy late winter, when conditions are harshest, pregnant cows still carry their antlers long after the large bulls have dropped theirs
The source saysBy late winter when conditions are most severe, pregnant females are the dominant members of the herd, because they are the only ones to have retained their antlers. The large bulls lose their antlers after the autumn mating seasonNote: HWW's 'only ones to have retained their antlers' is not repeated: the ADF&G notebook (2025) says small bulls and non-pregnant cows keep theirs until April
The page saysThat makes them the dominant members of the herd, able to defend their feeding craters and even push larger caribou off favoured spots
The source sayspregnant females are the dominant members of the herd ... The females' dominance allows them to defend their feeding craters from larger caribou and even displace larger caribou from favoured sites.
The page sayslichens are the primary winter food
The source saysGround and tree lichens are the primary winter food of caribouNote: stats.diet
The page saysMost female caribou carry antlers, which is unusual among deer
The source saysThis animal is unusual among deer family members in that most females, as well as males, carry antlersNote: FAQ 3
The page saysin the deer family antler size means dominance
The source saysIn the deer family, antler size means dominance.Note: FAQ 3
The page saysThe large bulls lose their antlers after the autumn mating season
The source saysThe large bulls lose their antlers after the autumn mating seasonNote: FAQ 3
The page saysBy late winter, when conditions are harshest, pregnant cows are the dominant members of the herd because they still carry theirs
The source saysBy late winter when conditions are most severe, pregnant females are the dominant members of the herd, because they are the only ones to have retained their antlers.Note: FAQ 3; HWW's 'only ones to have retained their antlers' softened to 'still carry theirs', because the ADF&G notebook (2025) says small bulls and non-pregnant cows keep theirs until April
The page saysThat lets them defend their feeding craters from larger caribou and even push larger caribou off favoured spots
The source saysThe females' dominance allows them to defend their feeding craters from larger caribou and even displace larger caribou from favoured sites.Note: FAQ 3
The page saysmost pregnant cows keep their antlers until after they give birth in June
The source saysMost pregnant females will keep their antlers until after they give birth in June.Note: FAQ 3

Source
05

Denali National Park & Preserve, National Park Service

Caribou. Denali National Park & Preserve, National Park Service.

The page saysfeet that click when it walks
The source saysCaribou produce a characteristic clicking sound as they walk due to tendons snapping past the sesamoid bones in their foot.Note: tagline phrasing
The page saysWalking comes with a click, the sound of tendons snapping past sesamoid bones in the foot
The source saysCaribou produce a characteristic clicking sound as they walk due to tendons snapping past the sesamoid bones in their foot.
The page saysthe click a caribou makes as it walks, from tendons snapping past the sesamoid bones in its foot
The source saysCaribou produce a characteristic clicking sound as they walk due to tendons snapping past the sesamoid bones in their foot.Note: vibe.reason, settled in #182: replaces 'vast subarctic tundra resonance', which argued from geography; the frame-drum beat now rests on the walking click

Source
06

AnAge: The Animal Ageing and Longevity Database, Build 15 2023

Rangifer tarandus. AnAge: The Animal Ageing and Longevity Database, Build 15, 2023.

The page saysOn average a reindeer lives 10 to 11 years, in the wild or in captivity
The source saysAverage lifespan in captivity is similar to what is observed in wild populations (10-11 years).
The page saysthe record in captivity is 21.8 years
The source saysRecord longevity in captivity is 21.8 years

Source
07

Fosbury & Jeffery 2022

Fosbury & Jeffery (2022). Reindeer eyes seasonally adapt to ozone-blue Arctic twilight by tuning a photonic tapetum lucidum. Proceedings of the Royal Society B: Biological Sciences.

The page saysEyes that shine deep blue in the Arctic winter
The source saysDuring the long Arctic winter, with the sun below the horizon, the reflection transforms to a deep blue.Note: tagline; 'shine' is the tapetum's reflection (eyeshine), not the iris
The page saysReindeer are the only mammal known to seasonally adapt their eyes to the extremely blue Arctic twilight
The source saysReindeer are the only mammal known to seasonally adapt their eyes to the extremely blue colour of the extended twilight that occupies a large part of the winter 24 h cycle in their Arctic habitat.
The page saysBehind the retina sits a tapetum lucidum, a mirror-like layer that sends light back through the light-sensing cells for a second pass
The source saysa layer directly behind the retina that acts as a mirror ... to redirect incoming light back through the photoreceptors for a second pass
The page saysIn summer it reflects gold and turquoise, like many other mammals' eyes
The source saysDuring the extended exposure to summer daylight, the tapetum reflection shows a gold-turquoise colour similar to many other mammals.
The page saysIn the long Arctic winter it turns deep blue
The source saysDuring the long Arctic winter, with the sun below the horizon, the reflection transforms to a deep blue.
The page saysits peak matching the color of twilight
The source saysWhile the first-order peak in winter matches the spectral distribution of twilight
The page saysResearchers propose how: the fluid between its collagen fibers shrinks, letting the fibers pack closer together
The source saysWe propose that this happens by a decrease of the spacing of the parallel rod-shaped fibrils in the crystal when the volume of the inter-fibril fluid decreasesNote: the paper frames the mechanism as a proposed, tested model; the fibrils are collagen ('photonic crystal of parallel collagen fibrils')
The page saysmirror layer behind the retina
The source saysa layer directly behind the retina that acts as a mirrorNote: stats.superpower
The page saysshifts from gold-turquoise in summer to deep blue in winter
The source saysDuring the extended exposure to summer daylight, the tapetum reflection shows a gold-turquoise colour ... During the long Arctic winter, with the sun below the horizon, the reflection transforms to a deep blue.Note: stats.superpower
The page saysto match Arctic twilight
The source saysWhile the first-order peak in winter matches the spectral distribution of twilightNote: stats.superpower
The page saysBehind a reindeer's retina sits a tapetum lucidum, a mirror-like layer of collagen fibers that sends light back through the retina's light-sensing cells for a second pass
The source saysa layer directly behind the retina that acts as a mirror ... to redirect incoming light back through the photoreceptors for a second passNote: FAQ 1; collagen from the abstract's 'photonic crystal of parallel collagen fibrils'
The page saysIn summer it reflects gold and turquoise
The source saysDuring the extended exposure to summer daylight, the tapetum reflection shows a gold-turquoise colour similar to many other mammals.Note: FAQ 1
The page sayswith a peak that matches the color of twilight
The source saysWhile the first-order peak in winter matches the spectral distribution of twilightNote: FAQ 1
The page saysThe researchers who measured it propose how: the fluid between the fibers shrinks, letting them pack closer together
The source saysWe propose that this happens by a decrease of the spacing of the parallel rod-shaped fibrils in the crystal when the volume of the inter-fibril fluid decreasesNote: FAQ 1

Source
08

Hogg et al. 2011

Hogg et al. (2011). Arctic reindeer extend their visual range into the ultraviolet. Journal of Experimental Biology.

The page saysIn Arctic reindeer the cornea and lens also let some ultraviolet light through, and the retina's rod and cone cells both respond to it
The source saysthe cornea and lens in Arctic reindeer do not block all UV and that the retina responds electrophysiologically to these wavelengths. Both rod and cone photoreceptors respond to UV at low-intensity stimulation.
The page saysThat may help them pick out differences in how Arctic vegetation and types of snow reflect it
The source saysA specific advantage of this short-wavelength vision is the use of potential information caused by differential UV reflections known to occur in both Arctic vegetation and different types of snow.
The page sayspaired with a retina that also responds to ultraviolet light
The source saysthe retina responds electrophysiologically to these wavelengthsNote: stats.superpower; 'these wavelengths' are the UV named earlier in the sentence
The page saysArctic reindeer extend their visual range into ultraviolet wavelengths
The source saysthe retina responds electrophysiologically to these wavelengths. Both rod and cone photoreceptors respond to UV at low-intensity stimulation. ... Reindeer thus extend their visual range into the short wavelengths characteristic of the winter environmentNote: FAQ 2; the abstract's 'short wavelengths' are the UV of its preceding sentences, and the paper's title says 'into the ultraviolet'
The page saystheir cornea and lens do not block all ultraviolet light, and the retina's rod and cone cells both respond to it
The source saysthe cornea and lens in Arctic reindeer do not block all UV and that the retina responds electrophysiologically to these wavelengths. Both rod and cone photoreceptors respond to UV at low-intensity stimulation.Note: FAQ 2
The page saysThat may help them pick out differences in how Arctic vegetation and different types of snow reflect ultraviolet light
The source saysA specific advantage of this short-wavelength vision is the use of potential information caused by differential UV reflections known to occur in both Arctic vegetation and different types of snow.Note: FAQ 2

Source
09

Holand & Mizin 2025

Holand & Mizin (2025). Rangifer tarandus. The IUCN Red List of Threatened Species 2025: e.T29742A224359765.

The page saysVulnerable
The source saysIUCN Red List category: Vulnerable (VU).Note: stats.conservationStatus, 2025 assessment

How the table was made: a writer drafted the profile from these sources and logged each claim with its quote, a reviewer with nothing but this table checked every sentence said no more than its quote, and a script confirmed each quote appears word for word in the source. The method is in the site'sAbout page.