"Dancing" Turtles Feel Magnetism Through Crystals Of Magnetite, Helping Them Navigate

Some of Earth’s creatures are capable of extraordinary migrations, covering thousands of kilometers every year. But how do they know which way to go? For loggerhead sea turtles (Caretta caretta) the answer to that question rests inside their ability to detect the Earth’s magnetic field – but how are they doing this?

The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

There are two ways that animals have been found to be able to sense Earth’s magnetic field. Either the turtles possess light-sensitive molecules that are affected by the field and allow the animals to see it; or, there are tiny magnetite crystals inside the turtles' bodies that move in the field and allow them to feel magnetism. 

To find out more about how the turtles navigate, the team behind a new study built on previous knowledge that showed that hatchling turtles could learn to associate the magnetic field found at a location with food. In fact, to show their recognition the little turtles danced, lifting themselves out of the water, moving their flippers, and opening their mouths. 

One group was conditioned over a two-month period to associate food with the magnetic signature for Turks and Caicos, while the other group was rewarded with food for the Haiti magnetic signature. 

“They are very food motivated and eager to dance when they think there is a possibility of being fed,” laughed Alayna Mackiewicz from the University of North Carolina at Chapel Hill, according to a recent statement. 

By using this dancing, the team realized they could find out if the turtles were seeing the magnetic field or feeling it. Producing a strong magnetic pulse temporarily disables the hatchlings' ability to feel the magnetic field; if the turtles were seeing the field they would keep dancing, but if they were feeling it then the dancing would stop. 

When the pulse was applied the team found that the turtles danced less, suggesting that they were previously feeling the magnetic field and not seeing it. This suggests that magnetite receptors are the main way that these turtles are able to tune into Earth’s magnetic field. 

However, the team is cautious to rule out any other mechanisms for how the turtles might navigate.

The study is published in the Journal of Experimental Biology.