Migration is the seasonal movement of animals from one region to another. Many animals migrate to other places, but not all animals migrate for the same reason. Some animals migrate to find food, mate and the change of weather. They have ways of knowing when to migrate. The Sun, Stars, and the magnetic field are like their maps of knowing when and where to migrate.
Many animals migrate, traveling to avoid bad weather, to find food, or to reproduce. Some migrators travel short distances, other go thousands of miles. Migrators travel by flying, swimming, walking, hopping, burrowing, or slithering. True migrators make a two-way trip each year from one place to another and back again.
The Arctic Tern migrates the longest distances of any animal. It flies over 21,750 miles (35,000 km) each year - roughly the circumference of the Earth. The whale that migrates the longest (and the longest-migrating mammal) is the Gray whale, which migrates about 12,500 miles (20,110 km) each year. The insect that migrates the longest is the desert locust, which travels about 2,800 miles (4500 km). The butterfly that migrates the longest is the Monarch, which migrates up to 2,000 miles, flying from Canada to central Mexico in the fall. The land animal that migrates the longest is the Caribou, which travels about 700 miles (1100 km).