Turtles' map holds if magnetic field drifts

Migration of loggerhead turtles

source: Anil Ananthaswamy
New Scientist vol 213 no 2846 January 7 2012 p10

Loggerhead turtles use the earth's magnetic field to help them navigate. Turtles hatch on Florida's coast, then move the the North Atlantic, where they stay for between six and twelve years in the North Atlantic Subtropical Gyre, a circular current, before going back to breed on North American coasts. North Carolina University's Ken Lohman and team set up a simulation of the coast of Portugal, and found that turtles changed direction in the simulated south coast, swimming south-west rather than south, which may help them escape predators off North Africa, though it takes them away from the gyre. However, at any simulated location, not all young turtles behave the same way. This variation in migratory behaviour may help the species to adjust to changes in the Earth's magnetic field.
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