Reindeer and caribou are one species, not two. The names mostly mark which side of the Atlantic you’re on.1Sedgwick County Zoo. Elk, Reindeer, and Caribou: What’s the Difference? The difference people sense is real in another way, though: many reindeer live alongside herders, while caribou are largely wild.
Why One Species Has Two Names
Scientists give both animals the same genus and species name, Rangifer tarandus.2Sedgwick County Zoo. Elk, Reindeer, and Caribou: What’s the Difference? In general use, “reindeer” refers to the Old World form in Europe and Asia, and “caribou” to the New World form in North America.3Cambridge University Press. Reindeer and caribou Rangifer tarandus in the wild and under pastoralism Both live in large groups, in the boreal forest and on the Arctic tundra.4Cambridge University Press. Reindeer and caribou Rangifer tarandus in the wild and under pastoralism
The two names grew from separate languages and histories, not from any biological split. Reindeer comes from Old Norse roots. Caribou was borrowed into English and French from a Mi’kmaq word usually translated as “snow shoveler,” for how the animals paw through snow to reach food. A traveler going from Norway to Newfoundland would meet the same species under a different label.
The name can also signal domestic versus wild. In Scandinavia, Finland and Russia, wild and herded animals are both generally called reindeer. In Canada and Alaska, wild herds are caribou, but Alaska also has herded reindeer descended from imported Eurasian stock, so both names can be correct there.
Signs and guides may list names such as woodland caribou or tundra reindeer. These describe local forms within the one species, not separate species.
Elk and moose add to the confusion. In Europe “elk” means the animal Americans call moose. Neither is a reindeer; they are separate deer species. A quick way to tell reindeer and caribou apart from other deer is that females routinely grow antlers.
Reindeer Herding and Domestication
Reindeer are not simply tame caribou. Genetic studies show domestic reindeer arose separately in Russia and in Fennoscandia.5PubMed Central. Genetic analyses reveal independent domestication origins of Eurasian reindeer That means the Sámi of northern Scandinavia and Finland tamed their own reindeer rather than adopting herds from western Russia.6PubMed Central. Genetic analyses reveal independent domestication origins of Eurasian reindeer Herders have often added wild animals to their herds through crossbreeding.7PubMed Central. Genetic analyses reveal independent domestication origins of Eurasian reindeer Yet some wild populations never contributed to domestic herds, which hints that not all reindeer are equally easy to tame.8PubMed Central. Genetic analyses reveal independent domestication origins of Eurasian reindeer Separate origins mean herding was not invented once and copied everywhere, and “the domestic reindeer” is a set of herded lines with different ancestries.
Herding grew gradually. Small-scale herding based on close cooperation and care appeared among the Sámi in the Late Iron Age.9Journal of Archaeological Research. The Archaeology of Reindeer Domestication and Herding Practices in Northern Fennoscandia A major shift to full reindeer herding came from the 15th century onward.10Journal of Archaeological Research. The Archaeology of Reindeer Domestication and Herding Practices in Northern Fennoscandia In northern Norway, domestic reindeer have largely replaced the region’s original wild genetic lines since medieval times.11Journal of Archaeological Science: Reports. From wild to domestic reindeer – Genetic evidence of a non-native origin of reindeer pastoralism in northern Fennoscandia
Tameness in an individual animal is different from domestication of a population. A wild caribou can be hand-raised, yet that doesn’t make its lineage domestic.
Herded reindeer usually roam large pastures and are gathered rather than kept in barns. They are less fully tamed than cattle and still behave much like wild animals. Herders depend on the animals’ natural tendency to stay together in groups, so the relationship is an ongoing one built through handling.
Traditional Sámi herding methods are still practiced.12Human Ecology. Shifting Strategies between Generations in Sami Reindeer Husbandry: the Challenges of Maintaining Traditions while Adapting to a Changing Context But fast-changing environmental conditions are pushing herders into situations where inherited knowledge may help less.13Human Ecology. Shifting Strategies between Generations in Sami Reindeer Husbandry: the Challenges of Maintaining Traditions while Adapting to a Changing Context
Differences in Size and Body Shape
Body shape varies more with habitat than with the name. Forest-dwelling forms are larger, longer-legged and darker than tundra forms.14PubMed Central. Available names for Rangifer (Mammalia, Artiodactyla, Cervidae) species and subspecies Their antlers are shorter, heavier and more branched.15PubMed Central. Available names for Rangifer (Mammalia, Artiodactyla, Cervidae) species and subspecies Forest and tundra populations also differ genetically in line with these body and lifestyle differences.16PubMed Central. Available names for Rangifer (Mammalia, Artiodactyla, Cervidae) species and subspecies Larger, longer-legged bodies suit moving through forest and deeper snow, while a compact build suits open, exposed tundra.
Leg length varies widely within herded reindeer and among wild ones.17Journal of Mammalogy. Factors Determining Leg Length in Rangifer tarandus Diet affects it, so poorer food in a herd’s history can produce shorter legs.18Journal of Mammalogy. Factors Determining Leg Length in Rangifer tarandus
This is behind the popular idea that reindeer are small and caribou are big. It usually comes from comparing a stocky, shorter-legged herded Eurasian animal with a large wild North American one, which isn’t a fair comparison of two species. A herded animal’s build reflects its management and food as well as its ancestry, and some wild Eurasian forest reindeer are large and long-legged too.
Norway’s semi-domestic mountain reindeer evolved on hard-packed tundra snow.19PubMed Central. Available names for Rangifer (Mammalia, Artiodactyla, Cervidae) species and subspecies They struggle in coniferous forests, especially in winters with deep, soft snow.20PubMed Central. Available names for Rangifer (Mammalia, Artiodactyla, Cervidae) species and subspecies
Why Female Reindeer Have Antlers
In this species both males and females grow antlers, unlike other deer.21Journal of Zoology. Biology of antlers Their antler cycle depends less on the reproductive organs than in other deer, though reproductive hormones still keep it in step with the breeding season.22Journal of Zoology. Biology of antlers
In females, the hormone estrogen drives antler growth, hardening and the shedding of velvet skin.23PubMed. Role of oestradiol in the regulation of the seasonal antler cycle in female reindeer, Rangifer tarandus Estrogen also keeps females from dropping hard antlers.24PubMed. Role of oestradiol in the regulation of the seasonal antler cycle in female reindeer, Rangifer tarandus Without the ovaries, females drop their antlers early, and antlers harden 1 to 3 months late.25PubMed. Role of gonadal hormones in the regulation of the seasonal antler cycle in female reindeer, Rangifer tarandus Spring antler growth always follows a seasonal rise in the hormone prolactin.26PubMed. Role of gonadal hormones in the regulation of the seasonal antler cycle in female reindeer, Rangifer tarandus
Antlers grow covered in soft, blood-rich skin called velvet, and animals rub it off when the antlers harden. Unlike horns, antlers drop off and regrow every year.
Females keep hard antlers through autumn and winter while pregnant.27PubMed. Role of oestradiol in the regulation of the seasonal antler cycle in female reindeer, Rangifer tarandus That is when competition for food dug from snow is fiercest, and antlers serve as weapons.28PubMed. Role of oestradiol in the regulation of the seasonal antler cycle in female reindeer, Rangifer tarandus Males usually drop theirs earlier in winter, after the breeding season. So antlered “reindeer” pulling a sleigh in late December are more likely female.
Caribou Migrations
Caribou and reindeer make the longest land migrations of any animal.29PubMed Central. Longest terrestrial migrations and movements around the world They were the only land animals recorded traveling more than 1,000 km in a round trip, apart from one wolf population that follows caribou.30PubMed Central. Longest terrestrial migrations and movements around the world
In northern Québec, spring migration averaged about 587 km over 48 days.31Journal of Mammalogy. Determinants of migration trajectory and movement rate in a long-distance terrestrial mammal Females there start and finish about 6 days earlier than males.32Journal of Mammalogy. Determinants of migration trajectory and movement rate in a long-distance terrestrial mammal That fits the idea that they are heading toward calving grounds, since newborns need to arrive when conditions favor survival.
Migrating caribou prefer tundra and avoid water, forest and high ground.33Journal of Mammalogy. Determinants of migration trajectory and movement rate in a long-distance terrestrial mammal Heavy rain or snow and deep snow slow them down.34Journal of Mammalogy. Determinants of migration trajectory and movement rate in a long-distance terrestrial mammal If lakes and rivers freeze later as the climate warms, caribou may have to detour around open water, costing distance and energy.35PubMed Central. Caribou, water, and ice – fine-scale movements of a migratory arctic ungulate in the context of climate change
Wild caribou choose their own routes between calving and winter grounds. Herded reindeer also migrate seasonally, but herders guide them between pastures. The herd’s built-in tendency to follow leaders is what makes herding possible.
Shared Arctic Adaptations
The reflective layer at the back of the eye is golden in summer.36PubMed Central. Shifting mirrors: adaptive changes in retinal reflections to winter darkness in Arctic reindeer In the dark Arctic winter it turns deep blue.37PubMed Central. Shifting mirrors: adaptive changes in retinal reflections to winter darkness in Arctic reindeer It then reflects more blue light, matching the blue twilight of winter.38Functional Ecology. Vision at high latitudes: High sensitivity without specific boreal adaptations in photoreception in reindeer (Rangifer tarandus L.) The layer sends light back through the retina, giving the sensitive cells a second chance to catch it.
Reindeer eyes also let in ultraviolet light, which most mammals’ eyes block.39Functional Ecology. Vision at high latitudes: High sensitivity without specific boreal adaptations in photoreception in reindeer (Rangifer tarandus L.) That lets them spot food plants and predators against snow in dim light.40Functional Ecology. Vision at high latitudes: High sensitivity without specific boreal adaptations in photoreception in reindeer (Rangifer tarandus L.) Snow reflects ultraviolet strongly, so plants and predators stand out as dark shapes against it.
Blood vessels in the nose run in opposite directions to recover heat from outgoing breath.41PubMed. Vascular basis for regulation of nasal heat exchange in reindeer Warm blood flowing out and cool blood flowing in pass close together, so heat moves between them. Outgoing breath is cooled and returning air is warmed, and the animal saves energy that would otherwise go to staying warm.
Fatty pads in the hooves cushion each step like a bumper.42PubMed Central. Macro-microscopic Research in Reideer (Rangifer Tarandus) Hoof Suitable for Efficient Locomotion on Complex Grounds The hoof spreads as weight moves forward, protecting it on long migrations.43PubMed Central. Macro-microscopic Research in Reideer (Rangifer Tarandus) Hoof Suitable for Efficient Locomotion on Complex Grounds
Gut bacteria attach to lichen and digest it from the inside.44PubMed Central. Ruminal microbial digestion in free-living, in captive lichen-fed, and in starved reindeer (Rangifer tarandus tarandus) in winter One gut bacterium can tolerate a toxic lichen chemical.45PubMed. Eubacterium rangiferina, a novel usnic acid-resistant bacterium from the reindeer rumen So reindeer can live on lichen, a winter food most animals can’t use.
Are Reindeer and Caribou Declining
Herds are declining across the Arctic as temperatures and rainfall rise and land is developed.46Global Change Biology. Global declines of caribou and reindeer Warming shifts seasonal timing, increases extreme weather and changes which species share ranges.47Global Change Biology. Global declines of caribou and reindeer Plants may grow at a different time than animals need them, extreme weather stresses animals that depend on predictable seasons, and newcomers can change competition and predation.
Responses vary because the species lives across such a wide area.48Environmental Reviews. Observed and predicted effects of climate change on Arctic caribou and reindeer One herd’s experience may not match another’s: some decline while others hold steady or even grow. Current trends support only cautious hopes for their future.49Environmental Reviews. Observed and predicted effects of climate change on Arctic caribou and reindeer
Ice is one worry. Rain-on-snow can form ice crusts that lock away food and cause starvation.50Ecological Monographs. Climate, snow, ice, crashes, and declines in populations of reindeer and caribou (Rangifer tarandus L.) Animals that dig for lichen may be unable to break through a hard crust over the plants. Still, evidence that ice drives declines widely is limited, and more snow or warmer winters sometimes increase established herds.51Ecological Monographs. Climate, snow, ice, crashes, and declines in populations of reindeer and caribou (Rangifer tarandus L.)