Rudolf, Dasher, Comet, Dancer, Cupid, Prancer, Donner, Blitzen and Vixen. They are the deer that help Santa carry his carriage full of presents on Christmas Eve. Specifically, they are reindeer (their scientific name is Rangifer tarandus), one of the forty or so species of deer that exist in the world and the only one that can be found living in the Arctic. But the fact that they are native close to his home is not the only reason that Santa might have chosen them as his companions. They also love travelling, some of them covering distances of up to 5000 km in a year, making their migration the farthest one of any terrestrial mammal. Reindeer are also very well equipped to cope with the cold. From the soles of their hooves to the tips of their noses, they are all covered in hair, which is so good at insulating their body heat that they can lie down on the snow without melting it.
Their noses are also very special—not only because of Rudolf’s red one. They have very intricate nostrils with an increased internal surface area to warm up the incoming cold air. Their nostril's insides are also covered with thin hairs where water in the air can condense and then be sniffed in into the throat. Of course, being so good at maintaining their body temperature, they can also afford getting much of their water from eating snow. All species of deer belong to the Artiodactyla order of mammals which includes all hoofed animals whose weight is supported by two toes, for example pigs, cattle, goats and sheep, as well as giraffes and hippos. The first deer might have appeared over 20 million years ago, the oldest known reindeer fossil has been dated to 400,000 years ago - the time that the last Ice Age started. So reindeer have been around for a long time and Santa has certainly not been the only one to use them for transportation. Archaeological evidence indicates that Siberian tribes were riding reindeer 2,000 years ago and many tribes today still ride them or use them to pull their sledges.