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New findings published in the Journal of experimental Biology demonstrate that young loggerhead sea turtles rely on a unique “magnetic touch” to pinpoint their location during long-distance migrations, solving a decades-old mystery about how these creatures navigate the open ocean.
Loggerhead turtles embark on amazing journeys spanning thousands of kilometers immediately after hatching, and can continue for decades. Scientists have long known these hatchlings aren’t simply drifting; they possess an innate magnetic compass for direction and a magnetic map for location. However, the specific mechanism they use to read that map remained elusive.
Researchers have understood for some time that animals can perceive magnetic fields in two primary ways. One involves light-sensitive molecules that potentially allow animals to see magnetic patterns. The other relies on magnetite crystals within the body, which shift in response to magnetic forces, effectively allowing the animal to feel the field.determining which of these senses loggerhead hatchlings utilize has been a key focus of recent investigation.
Previous work by Kayla Goforth, Catherine Lohmann, Ken Lohmann, and their colleagues established that hatchlings can learn to associate specific magnetic fields with the reward of food. This learning manifests in a distinctive behavior: an energetic “dance” involving raising their bodies, opening their mouths, and moving their front flippers.
“They are very food motivated and eager to dance when they think there is a possibility of being fed,” explained a researcher from the University of North Carolina at Chapel Hill. This eagerness provided a unique opportunity to test which magnetic sense was at play.
The research team exposed hatchlings to a strong magnetic pulse,temporarily disrupting their ability to sense magnetic forces. The logic was simple: if the turtles stopped dancing after the pulse, it would indicate they normally rely on a touch-based magnetic sense. Conversely, continued dancing would suggest they depend on a different form of magnetic detection.
training the turtles was a labor of patience. Researchers, including Alayna mackiewicz and Dana lim, spent two months feeding eight newly hatched loggerheads while exposing them to the magnetic field around the Turks and Caicos Islands. Another group was trained to recognize the magnetic field near Haiti. Each turtle was then subjected to the magnetic pulse after being trained.
Evidence Points to a ‘Feel-Based’ System
The results where conclusive. After exposure to the pulse, the hatchlings danced significantly less frequently enough, providing compelling evidence that they utilize a feel-based magnetic sense to determine their location on their inherited map, rather than relying on vision.
The researchers acknowledge that hatchlings likely integrate multiple cues for navigation, but the ability to feel the Earth’s magnetic field is clearly central to their success. They also note that the turtles employ a separate magnetic sense – potentially vision-based – to determine direction. These two abilities work
