Reindeer and caribou are two names for the same species (Rangifer tarandus), with reindeer generally referring to the domesticated variety that are herded by humans and pull sleds.
The domesticated reindeer live mostly in Scandinavia and Siberia and are typically smaller with shorter legs than their wild caribou relatives. Here, a reindeer in Svalbard, Norway.
A close-up view of a reindeer in the Arctic.
Researchers have found the reindeer change the color of their eyes from summertime's golden to blue in the winter. Here, winter (a) and summer (b) eyes following the removal of the cornea, lens and vitreous. The winter eye looked deep blue while the summer eye was golden with elements of turquoise around the edges, also shown in c and d where the eye cups were flattened.
Neuroscientist Glen Jeffery, who investigates vision at University College London, was sent a collection of reindeer eyes from the Arctic, some from reindeer killed in the summer, some in the winter. Here, a golden eye from a summer reindeer (right) and a blue peeper from a winter reindeer (left).
Researchers found the blue eyes reflect far less light out of the eye, helping the reindeer cope with the nearly continuous Arctic winter darkness.
In addition to blue eyes, reindeer may also sport Rudolph-red noses. Reindeer, it seems, have 25 percent more capillaries carrying red, oxygen-rich blood in their nasal architecture than humans, say scientists from the Erasmus Medical Center in Rotterdam, the Netherlands, and the University of Rochester in New York.
Reindeer Sheds Antlers
Trainee hoofstock keeper Marc Enderby holds up the antlers shed by male reindeer Lenni at Scotland's Highland Wildlife Park.