The world's biggest beasts have always captured the imagination. But whilst being big can have its advantages, it also comes with sizeable challenges. Take the world's largest lizard, the Komodo dragon, whosehuge appetite means it must take on prey ten times its weight, or the tallest animal of them all - the giraffe - who, with such a long neck, must control immense blood pressure. Nature's biggest beasts must go to extraordinary lengths to thrive. These are their epic survival stories!