Migration - Why do Animals Migrate?

Migration is a specific journey, and usually a very important one, that an animal takes regularly for a particular reason, usually at a particular time of year.  Animals migrate so that they can survive; it is a form of adaptation.

Many habitats have wet/dry or cold/hot seasons and are therefore difficult to survive in all year round, so the animals have to either move away (migrate) or hibernate in the winter.   Other areas may have more food or shelter or water available at certain times of year so the animals need to move there in order to survive.  Some species (e.g. elephants and wildebeest) need to eat special minerals which are only available in certain places so they need to go there regularly to get them.

Most mammals that migrate overland are herbivores (plant eaters) and they move as the

weather changes over the seasons, and the vegetation growth changes.  No carnivorous (meat-eating) land mammals regularly migrate, although packs of wolves may travel with caribou herds if food is scarce in their home territory.

As well as travelling in search of food, many birds will also migrate to places with fewer predators in order to breed and raise their young. 

Insects also migrate.  Some butterflies and moths fly very long distances.  Most migrating insects go much shorter distances.  Many, like termites and beetles, move downward into the soil. Earthworms also move down, some as far as six feet below the surface.

Of course some people migrate too.  They might move to another town, county or country to find work, start a family, avoid a war or famine, or if they are lucky enough, simply to have a holiday. Some of course choose never to come back (emigration); most return after their holiday or when it is safe to return.