The giraffe is the tallest animal in the world, attaining a height of 5.5m, its incredibly long neck accounting for much of its height. The long neck has resulted in a complex blood circulatory system, which is not yet fully understood by zoologists. Adult males generally reach a height of about 5 metres and females about 4,5 metres. Big males can weigh a massive 1 200 kilograms while females usually weigh some 800 to 900 kilograms. Their skin colour is tan with light brown patches on females and dark brown patches on males. Both males and females have short horns covered in skin.