Sea Turtle Migrations:
Migratory Route of Florida Loggerheads
Each population of sea turtles has its own characteristic patterns of movement. In these web pages we will focus primarily upon loggerhead sea turtles that hatch along the east coast of Florida.
Hatchling loggerheads from this population leave their natal beaches and migrate east to the Gulf Stream current. The Gulf Stream is a major oceanic current that sweeps northward along the southeastern United States coast. The migration from the beach to the Gulf Stream is referred to as the "offshore migration". Most loggerheads complete this journey during their first few days in the ocean, a period known as the "frenzy" because turtles are continuously active and strongly motivated to swim. The offshore migration helps the small, defenseless turtles survive by getting them away from shallow, inshore waters, where predatory birds and fish are particularly abundant.
The offshore migration is just the first step in a much longer transoceanic migration. By entering the Gulf Stream current, turtles become entrained in the North Atlantic gyre, the circular current system that flows around the Sargasso Sea. A highly generalized diagram of the North Atlantic gyre is shown below.
|Generalized diagram of the North Atlantic
gyre. The red arrows represent the main pattern of currents.
(Detailed current movements are considerably more complex than this
diagram suggests.) Near Portugal the Gulf Stream divides; the northern part moves toward Great Britain as the North Atlantic Drift, whereas the southern part veers southward.
The warm waters of the North Atlantic gyre provide young sea turtles with a favorable habitat for growth and development. Most Florida loggerheads remain within the gyre for at least several years. During this time they cross to the eastern side of the Atlantic Ocean before returning as large juveniles to the North American coast, where they take up residence in coastal feeding grounds.
Although all Florida loggerheads appear to spend a period of years within the North Atlantic gyre, different turtles probably do not follow precisely the same migratory route. In the diagram below, the red lines indicate some possible migratory paths that different individuals may take. In addition, whereas most turtles appear to circle the gyre only once, some individuals may make more than one circuit, others may spend time in the Sargasso Sea, and a few have been captured in the Mediterranean.