A Nearly all animal migrations happen for one reason only—survival. For some animals, it is to find food. However, for others, it is to have their young in a place away from other dangerous animals. Animals do not have a calendar on their wall to tell them when to migrate. So how do they know when to leave? How do they find their way back to the place they were born many years ago? Or how do they know which direction to go on a 12,000-mile journey? Scientists are starting to understand more of the secrets of animal migration.