Our “Species of the Week” series highlights the flagship species of each of the 844 unique ecoregions contained within Earth’s bioregions.
In Western culture and folklore, reindeer magically pull Santa Claus’s sleigh, flying around the world delivering presents for children to open on Christmas morning. Yet in reality, reindeer play an even more significant role in our shared ecosystem. Known also as caribou in North America, reindeer are the largest, most numerous herbivores in circumpolar areas, making their grazing essential for healthy vegetation.
Reindeer are native to northern Europe, Siberia, and North America in the Arctic, subarctic, tundra, boreal, and mountainous regions.
Female reindeer, or cows, can measure up to 1.6-2 meters (5-6.6 ft) and weigh up to 120 kg (260 lb). Males, or bulls, are slightly larger with a body length of 1.8-2.1 meters (5.9-6.9 ft) and can weigh between 159–182 kg (351–401 lb). The heaviest bulls can weigh as much as 318 kg (701 lb). Weight can vary dramatically between seasons, though, with males losing as much as 40% of their summer size in the winter months.
The most distinct feature of reindeer is their antlers. Reindeer are the only species in the cervid, or deer, family where both males and females grow antlers. In March or April, males begin, and in May or June, the females follow. As the antlers grow, they are covered in thick velvet, filled with blood vessels. Bulls begin to shed their antlers in early to midwinter, while female reindeers keep theirs and acquire the highest ranks in the feeding hierarchy with them. This means that the reindeer pulling Santa’s sleigh would all be female.
Another characteristic of reindeer is their changing eye color. A study by the University College London in 2011 revealed that reindeer could see light within the ultraviolet range. This ability helps them survive in the Arctic as many objects blend into the white, snowy landscape. It also improves their vision during continuous darkness and helps spot predators. Reindeer have gold eyes in summer and blue in winter.
Some species of reindeer are sedentary and live alone, while others live in herds of 50,000 to 500,000 animals and migrate 19–55 kilometers (12–34 mi) a day. Regardless of lifestyle, reindeer consume large amounts of food. With a four-chambered stomach, a reindeer’s diet can consist of lichen, leaves, grasses, mushrooms, and even small rodents, fish, and bird eggs when nutritionally starved. Their mass amounts of grazing help keep plant species healthy, which provides more food and shelter to the biodiversity in their ecosystem.
To Indigenous peoples living in the Arctic, reindeer have been a sacred animal. Inuit of the Kivalliq Region in northern Canada, the Caribou Clan in the Yukon, the Iñupiat, the Inuvialuit, the Hän, the Northern Tutchone, and the Gwichʼin all rely on reindeer for food, clothing, and shelter.
Currently, reindeer are considered vulnerable in conservation status. Their habit is most prone to climate change as the Arctic is warming four times faster than the global average. Supporting projects like and helps reindeer by protecting their range. They are a revered species to many cultures.