Sea turtles use different cues to navigate the oceans. During the very early stage, when a turtle first enters the sea, it uses the direction of the waves for orientation. Usually, swimming directly perpendicular towards the waves will take hatchlings directly seaward and away from the shore. The juvenile turtles do not need to see the waves for that, but use the orbital movement of the waves, most likely detected with the inner ear (sense of balance).
Part of their navigation system in the open ocean is the earth’s magnetic field! Depending on the specific location on earth, the magnetic field has a specific inclination and intensity. Sea turtles seem to be able to sense this signature. When turtles are placed experimentally in the magnetic field of a different location with the use of an electric coil, they will adapt swimming directions as if they have changed to the location of the magnetic field!
References:
- Lohmann KJ and Lohmann CMF 1992. Orientation to oceanic waves by green turtle hatchlings. Journal of Experimental Biology 171: 1-13.
- Lohmann KJ, Lohmann CMF, Ehrhart LM, Bagley DA and Swimg T 2004. Geomagnetic map used in sea-turtle navigation. Nature 428: 909-910.
