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Dancing turtles have proved for the first time that some animals use Earth鈥檚 magnetic field to create a personal map of their favorite spots, scientists said Wednesday.
Some animals that migrate across the globe 鈥� such as birds, salmon, and lobsters 鈥� are known to navigate using the magnetic field lines that stretch from Earth鈥檚 north to south pole.
Scientists knew the animals used this magnetic information as a compass to establish where they were. Now they increasingly believe the turtles are also able to plot a magnetic map featuring important places such as nesting or feeding spots.
This would require the migratory animals to 鈥渓earn the magnetic coordinates of the destination,鈥� according to a study in the journal Nature led by Kayla Goforth of the University of North Carolina.
The study said the research provides the first 鈥渄irect evidence that an animal can learn and remember the natural magnetic signature of a geographical area鈥�.
Exactly how they manage this remains unknown.
The researchers found that the turtles鈥� talent for map-making was separate from their inner compass, suggesting that the two forms of 鈥渕agnetoreception鈥� work in different ways.
For the experiment, the scientists put young loggerhead turtles in a tank surrounded by a magnetic coil that replicated the magnetic field of the Atlantic Ocean.
鈥楾urtle dance鈥�
Every day over two months, the scientists changed the magnetic field of the tank between the North American coast and the Gulf of Mexico.
The turtles however were only fed when they received the magnetic information of one of the areas.
When the turtles anticipated food, they flapped around, opening their mouths and spinning in circles in the water.
The researchers filmed this behavior, dubbed the 鈥渢urtle dance鈥�.
The turtles danced with the most enthusiasm in the tank they knew would give them with food.
This was 鈥渟trong evidence鈥� that turtles can learn the magnetic signatures of 鈥渟pecific geographical areas,鈥� the researchers said.
Even when tested four months later, the turtles still knew where they should dance.
No one knows聽exactly how animals tune into this magnetic information.
One theory is that some can detect the magnetic field鈥檚 influence during a chemical reaction between light-sensitive molecules.
But when the researchers tried to mess with this process by using what is called radiofrequency fields, the turtles kept on dancing on their spot, undisturbed.
A separate experiment testing the turtles鈥� inner compasses was more successful.
In a tank replicating the magnetic conditions of the West African archipelago Cape Verde, the radiofrequency emissions seemed to scramble the turtles鈥� compasses, sending them off in random directions.
The researchers concluded that 鈥渁 reasonable working hypothesis is that the compass sense relies on chemical magnetoreception, whereas the map sense relies on an alternative mechanism.鈥�
This hypothesis is backed up by signs that other migratory animals such as birds and amphibians may also have dual magnetic field receptors.