Animals on the Move
Some animals live their whole lives in one location. Others migrate, or move from place to place ? sometimes over huge distances.
Animals migrate for several reasons: to find food or water, to reproduce, or to seek more favorable weather. Many kinds of animals migrate, including bats, birds, large herbivores like caribou and elk, butterflies, fish, and marine mammals.
- Pacific salmon are born in freshwater streams and travel to the ocean to grow. When they reach adulthood, they travel back upstream (often up to 2,000 miles) to spawn. After overcoming obstacles like swift currents, fishing nets, and even waterfalls, they return to the exact spot where they hatched, lay their eggs, then die.
- One of the longest animal migrations is made by the arctic tern. Every autumn, it flies from its home near the North Pole all the way to the Antarctic!
- The monarch butterfly is another long-distance flier: every year, it flies from its winter home near Mexico City, Mexico, to the northern United States. The longest recorded flight of a monarch was over 1,800 miles!
- Many migrating birds find their way by using the sun and stars. Some scientists also suggest that bird brains have a sort of internal compass, that lets them sense the earth's magnetic field.