Such seasonal migrations also occur among mammals, such as caribou who move from the tundra to the forests, and the Greenland seal (Pagophilus groenlandicus) that makes a long journey from Greenland to Spitsbergen and Jan Mayn islands, where their young are born.
Many fish migrate from open water out at sea to warmer coastal waters and from the north to warmer southern regions during the winter months.
There are many theories trying to explain the origin of migrations and the physiological mechanisms that guide animals in migratory journeys. However, biologists have not all agreed on one specific theory.
The seasonal movements of birds and most other migrating animals happen because of both inside and outside stimuli that release a physiological migratory "trigger". Once an animal has begun a migratory journey, however, many factors act to keep it on the right path
Navigation by the sun or the stars seem to be involved in the migration of birds, and fish may be guided through the sea by minute traces of chemical odors from their ancestral rivers. Some scientist believe birds may be using the magnetic field of the Earth and are effected by its rotation around an axis. These two forces are different depending on where you are on Earth and maybe that is what directs the birds when flying!!
One of the coolest "migrates" is The Arctic tern.
Every fall it heads eastward across the Atlantic and down the west coast of Europe and Africa to winter in the Antarctic Ocean...Yes, by the South Pole!! In spring they return all the way north, following the East Coast of South and North America, a round trip that can total 22,000 miles (35,000 km). They see more daylight than any other living creature since they are in both the Arctic and Antarctic during the periods of the longest days.
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