Many species of birds, mammals, insects, amphibians and fish migrate. While the reason for migration often differs among species, some reasons for migration include avoiding extreme weather, mating and finding food.
About 1,800 species of birds migrate every year. These migrations are seasonal and usually cover long distances. Birds often migrate north to south, moving further south during the winter. Some insects also migrate long distances, including some species of locusts, dragonflies and butterflies. A single monarch butterfly does not complete the long migration on its own. Instead, individual butterflies mate and reproduce on the journey. The successive generations then complete the next leg of their journey.
Often fish, crustaceans and other species migrate for breeding. Atlantic salmon begin their life in a river before migrating downstream into the ocean. They then return upstream years later to lay their eggs and begin the migration cycle over again. Some species of sea turtles such as the loggerhead migrate every year to the same beach where they were born to lay their own eggs.
Many species of bats migrate in order to hibernate. During warm months, bats live in trees outdoors. As the weather turns colder, bats migrate to caves where they live throughout the winter.