Sea turtle migration
[1] The feeding and nesting sites of adult sea turtles are often distantly separated meaning some must migrate hundreds or even thousands of kilometres.
Although the foraging movements of leatherbacks seem to be determined to a large part by passive drift with the currents, they are still able to return to specific sites to breed.
Juvenile and adult sea turtles engage in seasonal migration, likely due to finding other thermal habitats and seeking areas with sufficient food availability.
The research team concluded that the migrations done by the sea turtles are helpful in regulating temperatures, which overall increases their aerobic metabolic activity.
For sea turtles who are endangered, finding an area of lower predation helps to maximize their overall fitness and keep them as an existent species.
[9] For female sea turtles, traveling back to their natal beach in order to lay their offspring has been hypothesized to have an advantage towards parasitic resistance and disease.
[13] Hatchling loggerheads mature within the North Atlantic Gyre and it is important that they stay within this current system since here water temperatures are benign.
They may return to the beach where they hatched, an ability called natal philopatry; this has been demonstrated in green turtles using mitochondrial DNA analysis.
[2] The precision migration of adults across featureless and dynamic oceans requires more than a compass mechanism, something Darwin pointed out in 1873:[18] "Even if we grant animals a sense of the points of the compass ... how can we account for [green sea turtles] finding their way to that speck of land in the midst of the great Atlantic Ocean" [of the migration of green sea turtles from the coast of Brazil to Ascension Island, a journey of 2200 km to an island only 20 km in diameter].
An error in heading of only a few degrees would lead a turtle to miss the island by almost 100 km and animal compass analogues are not thought to be this precise.
[20] The post-nesting migration of adult female green sea turtles from Ascension Island to Brazil has been recorded using satellite transmitters as part of an experiment into their navigation.
[26] There is evidence that sea turtles do use a navigational compass such as bicoordinate mapping or geomagnetic imprinting when making long migrations.
For sea turtles who are endangered, finding an area of lower predation helps to maximize their overall fitness and keep them as an existent species.
[21] If sea turtles used astronomical cues, they would not be able to navigate in waters where light does not attenuate well, on cloudy days or when the Moon is blocked by clouds.
Narrowing out the astronomical hypothesis, the use of Earth's magnetic fields can be viewed as the navigational tool for long-migration patterns of sea turtles.
Earth's magnetic field is used for migration for a wide variety of species including bacteria, mollusks, arthropods, mammals, birds, reptiles, and amphibians.
The magnetite affects the cells of the nervous system of the sea turtle by producing a signal that references the forces of the magnetic field and the direction and magnitude that is applied.
[29] Regardless of the hypothesis, hatchling turtles have the ability to determine the direction and inclination angle of which they are swimming with aide from magnetic fields.
[31] Changes within the intensity or inclination of the Earth's magnetic field can deter a sea turtles direction of travel, so it is important for geographical coordinates to play a role in open-sea migration.
It has been shown that when placed into areas with the same latitudinal but different longitudinal coordinates, sea turtles are able to continue traveling in the same magnetic direction they began in.
This method of navigation is important for female sea turtles, as it has been proven that they will return to their natal beaches to lay their own eggs.
Previous research concluded that returning to the natal beach in order to lay offspring is an advantage towards parasitic resistance and disease, which overall increases the fitness of the turtles.
