The Magnetic Compass

The Magnetic Compass

Procedure:

To determine if sea turtle hatchlings are able to use the Earth's magnetic field as an orientation cue, turtles were tethered in the orientation arena and permitted to swim under one of two ambient magnetic field conditions:

Half of the turtles swam in the Earth's magnetic field.
The other half swam in a reversed magnetic field -- one in which the direction of the field was changed 180° by the coil system.

Results:
Turtles tested in the Earth's field on average swam east to northeast, the direction that they normally follow while migrating offshore.
Turtles tested in the reversed magnetic field swam in approximately the opposite direction.
Results were similar for both loggerheads and leatherbacks.

Summary:
The results demonstrate that hatchling loggerhead and leatherback sea turtles have the ability to detect the Earth's magnetic field and use it as an orientation cue.

The Role of the Magnetic Compass in the Offshore Migration

References:
(Lohmann, 1991)
(Lohmann and Lohmann, 1993)