The researchers found that the green turtles they observed tended to move in a straight line and not just get carried away by ocean currents.
This suggests that these animals have some navigation mechanism that, in the open sea, does not involve the use of reference points or, probably, the stars.
If this mechanism did not exist, its movements would be more aligned with those of the currents. Combining this data with evidence from previous studies, the researchers suggest that this mechanism is most likely geomagnetic.
In a new one, published this Wednesday in Science Advancesresearchers placed devices that recorded the location and heading of six female green turtles (Chelonia mydas), which took about a month to travel more than 1600 kilometers westwards, crossing the Indian Ocean.
According to , the team also found that the sea turtles reoriented themselves periodically and very gradually, over the course of about 15 hoursslightly adjusting its direction. This means they travel in a succession of relatively straight lines, at slightly different angles.
Scientists say these reorientations provide evidence that turtles not only use a kind of internal map to estimate their approximate location, but also a internal compass to understand the direction in which they are oriented. This combination results in a navigation system that the article describes as “imperfect but adequate“.
“We demonstrated that, even in the open sea, far from the coast, they still know, very roughly, where they are,” said the first author of the study Graeme Hays.
“In shallow water, especially near their destination, they are likely to navigate using landmarks, just as one might use the GPS in the car on a trip home, but when they arrive in the neighborhood, turn off the GPS and orient themselves only by landmarks around the house,” the researcher concluded.
