The many successes of this approach, from Australia to Brazil to Florida, now are being undermined by the longliners. Studying sea turtle behavior is among biology's most difficult challenges, primarily because the reptiles spend virtually their entire lives in the water. Females return to land only for the few scant hours it takes to dig nests, lay about 100 eggs per nest and bury them. The nest is left unguarded, and the young have to dig out when they hatch. They then scuttle to the sea and disappear into the waves.
Most males never come ashore again.
The first extensive studies of sea turtle distribution began in the 1950s, when scientists started putting metal tags on turtles in great numbers. Tag recoveries helped biologists to gather the first good data on sea turtle movement. In the late 1980s, biologists turned to fitting large sea turtles with radio transmitters so they could track the animals by satellite for several months at a time. Because females usually return to nest on the beaches where they hatched, turtles from a given beach are often related. Consequently, a given mtDNA sequence can be characteristic of a particular beach, allowing scientists to determine any turtle's place of origin once the mtDNA of its nest beach has been sampled.