It is well-known that the giraffe is the animal of the tallest height. Its head, perched atop an over-sized neck, needs a heart of more than 11kg, able to pump so strongly as to take blood up to the brain. The giraffe spends much of its time snatching the foliage that it alone can reach. Its tongue can reach length of 50cm and is coloured blue. This colour is the subject of much debate, but theories have been put forward that this blueness protects the giraffe from sunburn and the toxicity of acacia trees.