"It's pretty fascinating how these creatures can find their way through this vast expanse of nothing," said study co-author J. Roger Brothers, a biology graduate student at the University of North Carolina, Chapel Hill.
Lost and Found
Loggerhead turtles, which weigh about 250 pounds (113 kilograms), have an enormous range that encompasses all but the most frigid waters of the world's oceans. (See " 5 Amazing Animal Navigators
Though they travel hundreds of miles out to sea, the carnivores seem to prefer coastal habitats, and are the most abundant of all marine turtle species in U.S. waters.
Every year, thousands of volunteers walk along Florida's sandy beaches to count loggerhead nesting sites, which provides scientists with a rich population data set.
At the same time, researchers have been tracking subtle shifts in Earth's magnetic field along Florida's coasts, using compasses to measure how the field's strength and other properties change over time.
So if the loggerhead sea turtles really use Earth's magnetic field to return to the beaches where they were born, then shifts in the field should lead to corresponding shifts in loggerhead turtle nesting sites. (See National Geographic's sea turtle pictures.)