Loggerhead turtles use geomagnetic field to navigate large distances

The loggerhead turtle can learn and remember the magnetic signature of an area and does a ‘turtle dance’ when in a location that they associate with food, a study in Nature reports. The research presents mechanisms of how migratory species navigate using the magnetic field of the Earth.

Sea turtles are renowned for their long-distance migrations and often return to feeding sites, even after seasonal journeys and displacements. Precisely how such species navigate remains undetermined, but growing evidence suggests the animals use the magnetic field of the Earth as a map and compass.

To determine whether turtles can learn the magnetic signatures of geographical areas, Dr. Kayla M. Goforth from the University of North Carolina at Chapel Hill, Chapel Hill, North Carolina and others housed juvenile sea turtles in tanks in which magnetic signatures related to specific geographical locations were recreated. The juveniles spent an equal amount of time in two magnetic fields but were fed in only one of them. When in the area associated with feeding, the turtles start to dance in anticipation. This finding presents strong evidence that turtles can learn to distinguish between magnetic fields, creating an internal ‘magnetic map’. The authors discovered this sense relied on a separate mechanism to the magnetic ‘compass’ of the turtle, implying that turtles have two distinct geomagnetic senses to facilitate navigation.

“Conditioned responses in this new magnetic map assay were unaffected by radiofrequency oscillating magnetic fields, a treatment expected to disrupt radical-pair-based chemical magnetoreception, suggesting that the magnetic map sense of the turtle does not rely on this mechanism,” the researchers write. “By contrast, orientation behaviour that required use of the magnetic compass was disrupted by radiofrequency oscillating magnetic fields. The findings provide evidence that two different mechanisms of magnetoreception underlie the magnetic map and magnetic compass in sea turtles.”

The findings suggest that migratory species such as loggerhead turtles use the geomagnetic field as a map when navigating large distances. The authors suggest the two distinct tools of magnetoreception could also be present in most vertebrate species, but more research is needed to determine the inner workings of these mechanisms.