Baby loggerhead turtles use the Earth's magnetic field to identify specific regions along their migration route across the Atlantic Ocean, new research has found.

The researchers at the University of North Carolina say the turtles have an inborn ability to detect magnetic fields that makes their remarkable navigation feats possible.

The loggerheads' migration path follows a circular current called the North Atlantic gyre. Within the current, the water is warm and food is plentiful. But if the turtles wander outside of the gyre – and some do – they will die from the cold.

Photo: Kenneth J. Lohmann

The fact that any of the baby turtles make it across the Atlantic at all is remarkable, say the scientists.

"To me, one of the great wonders of the world is that baby sea turtles enter the ocean and the swim across the Atlantic and back all by themselves," says Kenneth Lohmann, associate professor of biology at UNC.

"How can they find their way along an 8,000-mile migratory route they've never before encountered? We're finally on the verge of understanding how they do it."

Lohmann and his colleagues tested the turtles in a fibreglass pool surrounded by computer-controlled magnetic coils.

They manipulated the magnetic field around the pool to mimic the Earth's field at different points along the turtles' migration route.

When the coils were set to produce a magnetic field like the one in northern Florida, the turtles swam east, which, if they actually were in northern Florida, would take them out into the Gulf Stream.

When the coils mimicked the field around the southern tip of the North Atlantic gyre, the turtles headed northwest, which would take them back to the U.S. east coast.

The researchers say their results show the turtles have more than a simple compass. The turtles, they say, can detect the direction, angle and intensity of the field and derive specific information from that.

The study appears in Friday's issue of the journal Science.