Hawksbill sea turtles will travel large distances to forage and nest, but how do they know where they’re going? They probably don’t, according to recent research. Recent research published in the Journal of the Royal Society Interface used GPS to trace the migration pathways of hawksbills (Eretmochelys imbricata). The authors thought that by using models, they would be able to answer the “long-standing conundrum” of how some species make their way across the ocean.
They calculated the most likely pathways between places of interest using a mapping system, looking at lengths ranging from tens of kilometers to thousands of kilometers. They then compared this to genuine wild hawksbill sea turtle migration patterns following mating season. The sea turtles’ itineraries were frequently discovered to be circuitous: long and convoluted trips from point A to point B. This meant they were swimming much longer lengths than a straight line between two sites, with one turtle going 1,306.2 kilometers (811.6 miles) while the shortest path would only have taken 176.4 kilometers (109.6 miles).
The study authors noted, “The navigational inaccuracy of turtles was obvious immediately at the outset of their marine migration, with their first departure orientations not tending to be target oriented, as is commonly the case with birds.” The idea of using geomagnetism to help turtles reach remote locations while swimming in the oceans has been raised. The authors of this new work, however, argue that the turtles only have rudimentary map awareness and use signals to correct and redirect themselves, based on their methods.
“Turtles appear to have a primitive map with a resolution of many tens or even a few hundred kilometers, and they often do not reorient until they are well of course,” they write. “Sea turtles use a broadly target-oriented ocean crossing, open ocean course adjustments, and finally a localized search closer to the target to discover isolated prey.” A turtle’s complicated and difficult life cycle reveals how navigating between food and mating places is only one of many fights they must fight to reach maturity.
While traversing seven times the required distance between two sites (such as our 811-mile turt) may not appear to be very adaptable, there may be some advantages to the method. One possibility, according to the scientists, is that these navigational flaws might help cope with the effects of climate change on coastal ecosystems. Current breeding beaches are threatened by sea-level rise linked to the climate crisis, but a more trial-and-error method to finding good nesting locations may allow sea turtles to locate new beaches in place of lost ones.
The similar strategy might make it easier to find previously unknown foraging spots. According to the scientists, hawksbill turtles have a “very poor map sense in the open ocean,” but what they lack in navigating skills, they may make up for in target hunting. Because of their adaptability, they occasionally take the scenic route, but they may also come upon life-sustaining ecosystems along the road.
