Introduction to Turtle Migration
Sea turtles have been gliding through the oceans since the days of the dinosaurs, some 150 million years ago. These marine reptiles are some of the most amazing members of the animal kingdom. Of seven extant species, the leatherback turtle is the largest, growing to more than 1.7 m (6.5ft) in length and weighing over 900 kg (2,000 lbs). 
Inhabiting the warm and temperate regions of every sea (excluding the Arctic), sea turtles have an extraordinary life history that can span 80 years and over 22,500 km (14,000miles).  How sea turtles navigate, sometimes to within meters of a particular area, as they progress through numerous life stages,
still remains a partial mystery.
(Figure by Meylan 2011)
Sea turtles begin an arduous and complicated life’s journey the night they hatch and emerge on the sandy beaches of subtropical waters all around the globe. Hatchlings crawl, from well above the high tide mark, down to the water’s edge where they slip into the sea and swim out into open ocean.
Sea turtles spend their first year or two of life in the epipelagic zone, the surface waters of the open ocean, feeding and growing. This stage of their life is also called the “lost year”, “ocean phase”, or “pelagic phase”.
(Photo courtesty of National Geographic)
Juvenile sea turtles then move in shore during a benthic or nertic phase, in which they inhabit the sea floor of the intertidal zone. Here, sea turtles forage for a variety of intertidal life including sea grass, algae, and benthic macroinvertebrates such as shrimp and crabs. 
(Photo courtesy of Seaturtle.org)
After sufficient growth, sea turtles migrate to an adult feeding ground. Sea turtles have been shown to frequent specific feeding grounds with great fidelity; loggerhead turtles have been observed in the same 0.05 km2 area up to 4 times per week. 
(Photo courtesy of National Geographic)
Breeding adults exhibit natal philopatry, migrating to their place of birth to reproduce. Mitochondrial DNA analysis has shown that females reliably return to the beach they hatched from. The paternity of hatchlings, however, shows more variation leading researchers to believe that though males also display natal philopatry, sea turtles may mate before they reach their nesting ground therefore increasing genetic diversity within nesting sites. 
(Photo courtesy of National Geographic
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