Scientists Say: Migration

Migration is the movement of animals or people from one place to another

an aerial view of African terrain shows a stream of dozens, perhaps hundreds of wildebeests crossing the landscape

Each year, more than 1 million wildebeests make a dangerous migration across Africa to follow seasonal rains.

Martin Harvey/Getty Images

Migration (noun, “My-GRAY-shun”)

Migration involves animals or people moving from one place to another.

In animals, migration refers to regular, often seasonal movements. Many animals move between habitats to find better weather, food or other conditions. And they often cross long distances in big groups to do it.

African wildebeests, for instance, migrate in huge herds. Each year, these antelope loop through Tanzania and Kenya to follow seasonal rains. Those rains provide the wildebeests with water to drink and grass to eat. Salmon are also migratory creatures. These fish are born in rivers and streams but swim out to sea to eat and grow. Later, the salmon return to fresh waterways to lay eggs nestled safely in gravel.

Many animals migrate to escape harsh winters. Bar-tailed godwits, for example, make the longest nonstop flights of any birds to cross the Pacific Ocean. In the summer, these birds eat, breed and enjoy long days in the Arctic. Then, they soar to New Zealand or Australia to avoid the bitter cold and scarce food of northern winters.

Likewise, monarch butterflies in North America go south for the winter. Millions flutter from Canada and the United States to Mexico each year. But the round trip is much longer than any single butterfly survives. So, the insects stop to lay eggs along the way. These eggs give rise to new generations that complete the migration cycle their ancestors started.

For animals, migration always involves a return trip. (When animals move to a new place without returning, it’s called emigration.) Human, migration, on the other hand, refers to a permanent change of residence.

Humans have been on the move since our oldest ancestors spread out from Africa. Today, some 270 million people around the world live in a country other than the one where they were born, according to the United Nations. Some people move to find better work or housing. Others migrate to escape war, famine or natural disasters. As climate change worsens storms, floods and droughts, more people may migrate to escape climate-related dangers.

In a sentence

Migration is a dangerous, often deadly journey for African wildebeests.

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Maria Temming is the Assistant Managing Editor at Science News Explores. She has bachelor's degrees in physics and English, and a master's in science writing.

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