The lives of marine turtles involve a continual series of migrations. Hatchlings swim directly from their natal beaches into currents such as the Gulf Stream off our own coast. These serve as moving, open-ocean nursery grounds.
Later, the juveniles collect in coastal feeding areas that are hundreds or thousands of kilometers from the beaches where they hatched. And yet, when they become adult and are ready to reproduce, they have the ability to return to their regional beaches.
Green turtles nest on tiny Ascension Island situated in the Atlantic Ocean and far from the African coast. They regularly migrate from their Brazilian feeding grounds directly back to that tiny island to nest.
Kemp's ridley turtles scattered along our Atlantic coast and in the Gulf of Mexico, converge to nest on a single beach on the east coast of Mexico.
Loggerheads that hatch on beaches in Japan traverse the entire Pacific Ocean to the Baja Peninsula in Mexico before returning to Japan as adults to nest on the regional beaches.
Thus, the picture that emerges is that no stereotypical migratory pathway exists for the adults of a given species or even the population of a specific rookery. Instead, turtles converge on nesting beaches from widely dispersed feeding grounds, and each individual migrates back to its own feeding grounds after nesting is completed.
Satellite tracking of these migrating turtles show that they take a direct route to their destination. These tracked plots leave little doubt that the turtles know where they are going and that they must possess some navigational system to determine their geographic position relative to that goal.
The ability of the turtles to find their way has long intrigued marine biologists. Now it is believed that they must be sensitive to the earth’s magnetic fields. Working with hatchlings has proven to be experimentally easier than with the free-ranging adults for establishing their response to magnetic fields.
Therefore, technically sophisticated experiments were performed in Florida that involved changing the magnetic field in the vicinity of free-swimming hatchlings. It was observed that the hatchlings changed their direction of swimming to match changes both in magnetic field direction and inclination.
Difficult as it may be to believe, these so-called ‘lower’ animals apparently are aware of sensations that totally elude us more ‘advanced’ humans. It would appear that the Animal Kingdom had acquired the Global Positioning System long before Homo sapiens came along.