How do animals determine direction?

Two new studies reveal how animals use their inherent "compass" to identify directions. Researchers found that migrating sea turtles rely on regional magnetic fields to guide them in the North Atlantic. Turtles orient themselves along a circular flow system called the North Atlantic Gyre, avoiding dangerous cold waters. Sea turtle hatchlings from eastern Florida, USA, begin their long migration as soon as they enter the sea. They swim to the North Atlantic Gyre that surrounds the Sargasso Sea and spend several years swimming along it.

Scientists placed turtles in a large tank surrounded by a computer-controlled coil to study how hatchlings react to different magnetic fields. Each turtle was fitted with an electronic tracker that recorded its position. Turtles can respond to certain changes in the magnetic field by changing the direction they swim.

In another study of subterranean mole rats in Zambia, Czech and German researchers found that some nerve cells in a brain structure called the epithalamus are part of the animals' biological "compass." These groups of cells respond selectively to different magnetic field directions. Moles use this magnetic sensory information to synthesize a mental topographic map of their surroundings, while other animals use different sensory information to reach the same topographic map.

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