How sea turtles and other aquatic life find their way across the open ocean far from any real navigation aids or natural signposts has long intrigued biologists. A new study shows that turtles have basic steering built in, but they still rely on luck and perseverance to find a destination.
Scientists fitted 22 hawksbill turtles with gps trackers to see the routes they would take back to their original areas after they were bred. The routes taken were rather circuitous.
One turtle traveled a total of 1,306 kilometers to find an island that was just 176 kilometers away from its starting point. The researchers found that there was a lot of swimming around in circles before the animals were able to settle on dry land again.
The researchers wrote in their paper that their results provided compelling evidence that hawksbill turtles only have a relatively crude map sense in the open ocean.
The existence of widespread foraged and breeding areas on isolated oceanic sites points to target searching in the final stages of migration being common in sea turtles.
Sea turtles are well known for being able to migrate huge distances across the ocean, often landing upon small and isolated islands a long way from anywhere else, so the question is how they are finding these remote spots surrounded by open water.
It hasn't been clear how precise or accurate the magnetic mapping technique is, despite previous research that shows turtles have a sense of Earth's magnetic field.
The tagged turtles swam twice as far as they needed to find the sites. Hawksbill turtles have relatively short migratory distances compared to other turtle species.
Multiple species use changes in the strength and direction of the magnetic field to figure out which way to go. The navigation aid appears to work in the case of these turtles.
It doesn't allow straight-line migration, but it does tell them when they're getting a long way off route.
The researchers found some evidence of course correction in both open water and shallow water close to land. Many of the findings in this study are similar to what has been observed in green turtles.
The researchers could not tell if the ocean currents affected the way the turtles got from A to B.
The behavior and navigation of the turtles is very different from sea birds, who usually find their destinations quickly, and most probably use smells carried on the wind to do so. Sea turtles don't seem to have any signals to make decisions.
Sea turtle navigation abilities are not perfect, but may be as good as possible within the constraints of their sensory ability, according to the researchers.
The Journal of the Royal Society Interface has published the research.
All Rights Reserved © 2024
