for National Geographic News
Sea turtles and salmon may use their sensitivity to Earth's magnetic field to guide them home at the end of their epic coming-of-age journeys, suggest scientists aiming to solve one of nature's enduring mysteries.
The newly proposed theory is one of several ideas being explored under the banner of an emerging scientific field dubbed movement ecology.
According to the field's proponents, the study of movement is central to understanding where animals and plants live, how they evolve and diverge, and why they become extinct.
By making movement central to ecological studies, scientists hope general theories about movement will emerge.
Such theories could, for example, help scientists predict how organisms will respond to global climate change and prevent the spread of pests and diseases.
Kenneth Lohmann, a marine scientist at the University of North Carolina, Chapel Hill, applied the concept of movement ecology to sea turtles and salmon.
His aim was to develop a hypothesis for how such animals navigate to their natal areas from distant oceanic locations.
Juvenile sea turtles and salmon leave their birthplaces with an inescapable wanderlust, swimming hundreds or even thousands of miles away.
But after years on the high seas, the biological urge to reproduce calls the creatures home, and they return to the very spots in which they were born.
How they do this has eluded scientists for decades. Lohmann says the secret to the marine animals' navigational success may lie in the variability of Earth's magnetic field.
Each coastal area has a unique magnetic signature, he said.
Previous studies, including work in Lohmann's lab on sea turtles, indicated both the turtles and salmon are sensitive to the magnetic field.
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