Many animals are on the move when seasons change, but where do they go and how do they get there? The following animals have fascinating travel tales--no matter what time of year they make their move. 1. Whales In autumn whales move from subpolar to subtropical seas to reproduce, returning to colder, food-rich waters in late spring. They may be guided by a magnetic substance (called magnetite) in their brains that functions as a magnetic compass. 2. Bluefish Known for their sharp teeth and insatiable appetites, bluefish migrate in dense packs each spring, preying on other fish that come inshore to spawn. Bluefish often leave a trail of blood for miles as they consume other fish in a feeding frenzy. 3. Lemmings When overpopulation of the Norway lemming leads to a food scarcity and habitat overcrowding, thousands of the animals migrate overland in search of food. Many lemmings die during the migratory process--lemmings that reach the sea drown while attempting to swim the ocean as if it were a river. 4. Lobsters Each year, the spiny lobster makes an astounding migration. Individual lobsters join large numbers of others to march single file across the ocean's floor. Scientists don't fully understand why the spiny lobsters do this, but it is believed to have something to do with their reproductive cycle. 5. Turtles Each year thousands of female green turtles swim more than 1,000 miles from the coast of Brazil to tiny Ascension Island in the South Atlantic Ocean. There they haul themselves onto the sandy beaches, scrape out shallow nests, and deposit their eggs. Then they swim back to Brazil. 6. Eels Freshwater eels spend most of their lives in North American and British lakes and rivers, but to reproduce they swim from each side of the Atlantic to an area of the Sargasso Sea between Bermuda and Puerto Rico. Land barriers are no problem: The eels just slither overland through dewy grass. After breeding, they return to their freshwater homes. 7. Monarch Butterflies The monarch butterfly is known for its extraordinarily long migrations: Monarchs that live east of the Rocky Mountains fly to central Mexico, and those that live west of the Rockies migrate to the California coast. The longest recorded flight for a tagged adult is 1,800 miles. 8. Plovers The American golden plover travels about 8,000 miles from nesting areas in the Arctic to the southern tip of South America--one of the longest migrations known. The trip includes about 2,000 miles over open ocean. 9. Salmon Juvenile salmon memorize the odor of the stream in which they were born. Years later they use this knowledge to navigate from the ocean back to the mouth of their home river; they then follow its distinctive odor upstream.