Turtle Magnetism

Loggerhead sea turtles use the Earth’s magnetic fields to find their way home.

Jan 19, 2015
Jenny Rood

WIKIMEDIA, US FISH AND WILDLIFE SERVICEThe magnetic signatures of Florida’s beaches lead loggerhead sea turtles back to their birthplace to hatch the next generation, researchers reported last week (January 15) in Current Biology.

The Earth’s magnetic field is in constant flux, yet the turtles use it to navigate in the open ocean. Until now, however, the turtle’s magnetic senses weren’t explored as a possible explanation for the adult females’ incredible homing ability. J. Roger Brothers and Kenneth Lohmann of the University of North Carolina hypothesized that if the turtles also followed the magnetic field back to their birthing beaches, shifts in the field should impact where on the beach loggerhead mothers-to-be landed. In particular, a change in the distances between the magnetic addresses, or isolines, on the beach would lead to a change in the density of turtle nests.

By comparing volunteer-collected nesting data and the positions of the isolines along the Florida coast over a 19-year period, Brothers and Lohmann found that when the distances between the magnetic signatures shrank, so did the distance between the nests. When the field shifted to create greater distances between isolines, the turtles were more spread out. “These results provide strong evidence that nesting sea turtles use Earth’s magnetic field to locate their natal beaches,” the authors wrote in their paper. In addition, since many other species also follow the Earth’s magnetic fields to reach their destinations, the suggestion that turtles might be storing magnetic information from birth to maturity could impact the understanding of other animals’ journeys as well.