Giraffe bulls are the largest land animals, reaching heights of up to six metres. Their necks can be two and a half metres long and they can weigh up to 250 kilograms. Nevertheless - just like us human beings - they only have seven cervical vertebrae. Giraffe bulls are so large, they can put their head through the window of the second floor of a building and say "hello". Their tongue is up to 50 centimetres long, is desensitised to prickly leaves, and has an unusual colour: it is dark blue. This colour helps protect it from sunburn when giraffes use it to wrap around and pluck leaves. Even animals as large as giraffes need to sleep between meals. When there is no threat of danger, they lie down for a nap, but in the wilderness they mainly sleep standing up.