The Imprint Happens on the Very First Night
A loggerhead sea turtle hatchling weighs about 20 grams when it breaks out of its shell. Within hours, it is already doing the most important thing it will ever do: reading the Earth's magnetic field. Research published in Current Biology by Kenneth Lohmann and his team at the University of North Carolina showed that hatchlings imprint on the unique magnetic signature of their natal beach within the first hours of entering the ocean. This is not a general sense of direction. The turtle is recording a precise geomagnetic coordinate, the specific combination of magnetic field intensity and inclination angle that exists at that one stretch of sand, and storing it for life.
