Young sea turtles have an amazing ability. With a built-in compass, they can navigate home using magnetic fields for directional orientation while they migrate from ocean to ocean across the world. A new study done by satellite shows that adult sea turtles can also use magnetic fields to orient themselves.
Marine biologists knew that young sea turtles could make epic trans-continental voyages by themselves with seemingly no directional markers, from the moment they enter the ocean for the first time. These migrations can span up to 1,400 miles.
Kenneth Lohmann, the lead author of this new study about how sea turtles use magnetic fields to guide them, was able to prove in a previous study that young sea turtles can detect magnetic fields. However, this mechanism had been previously unstudied in adult sea turtles. Adult sea turtles seem to learn their way around areas, developing "maps" that they can use to find specific areas. Lohmann noted that adult sea turtles are difficult to study because of their immense size. Adult leatherback sea turtles, the largest species, can reach sizes of up to 1,000 pounds, measuring six feet.
Lohmann's new study was published online in the journal Current Biology on January 15. Lohmann's team chose a group of female turtles that had just laid eggs on the same island. They split the turtles into three separate groups, and attached satellite trackers to each turtle. The researchers then attached magnets to the turtles in two of the groups to see if that would disturb the turtles' natural guiding mechanism. The turtles were then taken away by boat to see if they could find their way back to the eggs.
The team found that each group of turtles successfully navigated home. Two of the groups took unnecessarily complicated routes, though the scientists posited that this may have been due to ocean currents preventing the turtles from moving in the direction they wanted to. Allowing for the effect of ocean currents, the team found that the group of turtles without a magnet placed on them were able to find their home more directly than the turtles who had a magnet on them, showing that turtles are likely using magnetic fields as a guiding principle. This makes adult sea turtles unique in using magnetic fields for navigation, as well as using their own memory of a place.