How Sea Turtles Navigate

Lohmann, Kenneth

As soon as they hatch, sea turtles swim across hundreds of miles of featureless ocean; as adults, they navigate home to nest. Research has begun to identify the biological compasses and maps that guide them... A turtle's ability to orient itself seems quite sophisticated and reliable. For some sea turtle populations, the initial offshore migration appears to be just the first step of a transoceanic journey lasting several years. After leaving Florida as hatchlings, for example, loggerhead turtles (Caretta caretta) are not seen again in U.S. waters until their shells have grown to more than half a meter in length. No one has yet tracked the tiny turtles through the miles of open sea into which they vanish. Circumstantial evidence, however, suggests that the Florida loggerheads eventually cross the Atlantic and navigate back. There is an orderly progression of juvenile turtle sizes along the North Atlantic gyre, the clockwise oceanic current system that encircles the Sargasso Sea (the relatively still portion of the central north Atlantic). Thus, after entering the Gulf Stream, young turtles may swim eastward across the Atlantic, then south around the Sargasso Sea and westward back to the Florida coast. Adult turtles navigate even more skillfully than young turtles do. For instance, green turtles (Chelonia mydas) that frequent feeding grounds off the coast of Brazil regularly migrate eastward across more than 1,400 miles of open ocean to reach their nesting grounds at Ascension Island.

How Sea Turtles Navigate

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