WWho would have thought that you could teach baby sea turtles to dance on command? Monkeys and circus elephants, perhaps, but turtles with their more modest brains? However, here's what study published today in Journal of Experimental Biology did to learn more about sea turtle navigation.
Researchers at the University of North Carolina at Chapel Hill used food rewards to condition newly hatched cutthroat trout.Caretta Caretta) “dance” when they encountered a familiar magnetic field, and then watch the turtles' reaction to the interruption of the field.
The “dance” of the turtle is not only entertainment. This behavioral term refers to the excited bobbing they do in anticipation of food, propelling themselves higher out of the water, flapping their fins and opening their mouths. The researchers knew from their previous research that newly hatched cutthroats can learn to associate food rewards with magnetic fields, as evidenced by dancing in response to certain magnetism. They hypothesized that during their long-distance annual journeys to feeding grounds, turtles remember areas rich in food based on the characteristics of their magnetic field.
But they wondered what innate navigational tool the baby turtles relied on to traverse Earth's magnetic fields. Animals, such as some species of fish and birds, that migrate long distances typically use either light-sensitive molecules in their eyes to see magnetic fields or crystals of the mineral magnetite in their bodies to sense magnetic fields. Sea turtles can use both.
Read more: “How sea turtles find their way»
Over the course of two months, eight cubs were trained to associate food rewards with two specific magnetic fields that simulated areas within their natural range (one in Turks and Caicos and the other near Haiti), which was “really fun, but quite time-consuming,” said graduate student and lead author of the study Alaina Mackiewicz in statement.
Once the turtles learned to expect food in these particular fields, each hatchling's ability to sense magnetic fields was interrupted by a strong magnetic pulse from an electromagnetic coil. Although this temporarily disabled the cubs' magnetic sense, the scientists returned them to the magnetic field, which they learned to associate with food. Their dancing died down, demonstrating that the turtles relied primarily on a sense of magnetism to mark their position as a foraging location.
The researchers concluded that “magnetite-based magnetoreceptors underlie turtles' map sense, as a magnetic pulse could potentially disrupt such receptors.” But because the turtles' dancing did not stop completely when their magnetic sense was turned off, the study authors leave open the question of whether sea turtles add senses other than magnetoreception to mapping food resources.
Regardless of how they manage it, it's quite remarkable how these little animals somehow find the best feeding spots across thousands of miles of ocean to return to again and again as they grow older.
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Main image: Hila Shaked/Wikimedia Commons
