The reindeer is widely distributed mainly across the Arctic and sub-Arctic regions, inhabiting tundra, mountains, and taiga. Body size varies greatly by region, with a body length of 1.5–2.3 m and a shoulder height of 0.9–1.4 m. Both males and females carry branched antlers; the breeding season is in autumn, and after a gestation period of 225–235 days a single calf is usually born. In summer they feed on a variety of plants, while in winter their main food is lichens. They have excellent insulation and show marked cold adaptations, such as seasonal changes in eye color. They are highly migratory and undertake seasonal movements in large herds, but their numbers have been declining in recent years and they are listed as Vulnerable (IUCN Red List category II).