The giraffe is the tallest of all animals, reaching 18 feet (5.5 m). It has a series of valves in the vessels if its vascular system to ensure a blood supply to the head. It also has three skin-covered horns, two on top of the head and one between the eyes. Giraffes' principal food are acacia and mimosa leave. They live on tree-dotted grasslands south of the Sahara in Africa.