Many reindeer (also known as caribou) live in the area around the North Pole called the Arctic. There's no land at the North Pole, but the sea there is so cold that its surface freezes and turns to thick ice. Arctic animals have to survive freezing temperatures for much of the year, and life is tough. Reindeer have thick, fur coats to keep them warm. Some have a layer of fat for extra warmth. In the summer reindeer feed from the tundra which is blanketed in hardy grasses, lower-growing shrubs, clumps of moss and patches of a plant-like organism known as lichen.