We've just got closer to the Secret of How Turtles Navigate in the Open Ocean

We've just got closer to the Secret of How Turtles Navigate in the Open Ocean ...

Biologists have long enthusiastic about how sea turtles and other aquatic life discover their way across the open ocean, far from any real navigation aids or natural signs. Until now, a new study reveals that turtles have a basic geomagnetic steering built in, but they''re still relying on perseverance and luck to find a destination.

Scientists fitted 22 hawksbill turtles (Eretmochelys imbricata) with GPS trackers to determine the routes they would take back to their original foraging grounds after mating and breeding. Those trackers revealed that the routes taken were fairly circular.

One turtle travelled 1,306 kilometers (812 miles) to find a region just 176 kilometers away from its beginning point, for example. Luckily, researchers discovered that swimming in circles was prevalent before the animals could settle on dry land again.

According to the researchers in their published study, "Our findings provide compelling evidence that hawksbill turtles only have a relatively crude map sense in the open ocean."

"The existence of large foraging and breeding areas on isolated oceanic sites indicates that search in the final stages of migration will become common among sea turtles."

Sea turtles are well-known for being able to travel huge distances across the ocean, often landing on small and isolated islands a long way from anywhere else, therefore the question is how they''re working to find these remote spots surrounded by open water.

Although previous research has demonstrated that these turtles have some understanding of Earth''s magnetic field, which can assist in their route planning, it hasn''t been clear how precise or exact this magnetic mapping technique is.

Usually, the tagged turtles went twice as far as they needed to go to foraging sites. Despite their appearance, these hawksbill turtles have relatively limited migration distances to cover.

Multiple species in the world are using changes in the strength and direction of the magnetic field around Earth to determine which path to go. In the case of these turtles, that navigation assistance appears to work, but only to a certain extent.

"It does not allow pinpoint straight-line migration, but it does not tell them when they''re coming off the road," said marine ecologist Graeme Hays of Deakin University in Australia.

Both open water and less shallow water are closer to land, according to the researchers. Many of the results in this study match up with what''s previously been observed in green turtles (Chelonia mydas).

Ocean currents did not affect the way the turtles went from A to B, as far as the researchers could tell. Nor did the turtles appear to wait for a certain set of local weather conditions before embarking on their journeys just after breeding.

The behavior and navigation of the turtles is in a great contrast to some sea birds, who often find their destinations quickly, and most likely utilize smells carried on the wind to do so. It appears that sea turtles do not have any clues to make a decision.

"Our findings suggest that sea turtle navigational abilities are far from adequate, but they may simply be as good as possible within their sensory abilities," say experts.

The report has been published in the Journal of the Royal Society Interface.

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