A Loggerhead turtle with tracking device.
Scientists Nathan Putman and Ken Lohmann have determined that turtles can navigate across entire oceans by using the earth’s magnetic fields to determine their longitude and latitude. To test this hypothesis, they used a special water tank that permitted them to alter the magnetic fields inside. They then placed the turtles in the tank to see how they would respond to simulations of different locations…
Using his coil-surrounded tank, Lohmann could mimic the magnetic field at different parts of the Earth’s surface. If he simulated the field at the northern edge of the gyre, the hatchlings swam southwards. If he simulated the field at the gyre’s southern edge, the turtles swam west-northwest. These experiments showed that the turtles can use their magnetic sense to work out their latitude – their position on a north-south axis. Now, Putman has shown that they can also determine their longitude – their position on an east-west axis.
He tweaked his magnetic tanks to simulate the fields in two positions with the same latitude at opposite ends of the Atlantic. If the field simulated the west Atlantic near Puerto Rico, the turtles swam northeast. If the field matched that on the east Atlantic near the Cape Verde Islands, the turtles swam southwest. In the wild, both headings would keep them within the safe, warm embrace of the North Atlantic gyre.