Fortunately, a new study shines light on how these most wondrous of creatures do this, Mashable reports.
Female sea turtles swim for thousands of miles before reaching their birthplace, and the study illustrates that they rely on magnetic signatures along the coast.
Exactly how they do this has mystified scientists for more than 50 years, noted the study’s lead researcher, J. Roger Brothers, a graduate student of biology at the University of North Carolina at Chapel Hill.
“Our results provide evidence that turtles imprint on the unique magnetic field of their natal beach as hatchlings, and then use this information to return as adults,” Brothers said in a statement, per Mashable.
Earlier studies showed that sea turtles use Earth’s magnetic field to guide them along the way, but it wasn’t clear if magnetic features also worked to steer them toward the nesting sites chosen by their mothers, according to the researchers.
So, the scientists decided to investigate. They did this by examining a database of records that covered 19 years of loggerhead sea turtle (Caretta caretta) nesting along Florida’s east coast. This area is the largest sea turtle rookery in North America.
Earth’s magnetic field is like a giant invisible shield that protects the planet from dangerous solar radiation, and it changes over time. With it’s iron core, Earth is surrounded by molten metal that sloshes around, causing fluctuations in the magnetic field. As this happens some areas strengthen while others weaken, Mashable reports.
For sea turtles, the commute is a long and difficult struggle. The magnetic field changes slowly over time and loggerhead turtles have to shift their nesting locations in response, the study, published January 15 in Current Biology, found, per National Geographic.
“It’s pretty fascinating how these creatures can find their way through this vast expanse of nothing,” said Brothers, a co-author of the study.
Weighing about 250 pounds (113 kg.), loggerheads have a huge range that spans all but the very coldest parts of the world’s oceans, and these marvelous reptiles travel hundreds of miles out to sea. These carnivores do, however, prefer coastal habitats, and National Geographic reports that they are the most abundant of all marine turtle species in U.S. waters.
Each year, thousands of volunteers patrol Florida’s sandy beaches and count loggerhead nesting sites, and this provides scientists with a treasure trove population data set.
Researchers have also been tracking the subtle shifts in Earth’s magnetic field along Florida’s coasts, and to do so, they use compasses that measure how the field’s strength and other properties are changing over time.
If loggerhead sea turtles really do use Earth’s magnetic field to return to the beaches of their birth, then shifts in the field should also lead to corresponding shifts in loggerhead nesting sites, National Geographic reports.
Brothers and his colleagues combined the data collected by volunteers regarding turtle nests along with official data about the magnetic field to create a dynamic map that showed how each variable changed over time, National Geographic reports.
Upon examination of the data, which was recorded from 1993 and 2011, this concept was confirmed, The Science Times reports. During certain periods the Earth’s magnetic field shifted so that the signals from nearby beaches moved closer together. When this occurred, the turtles’ nests covered these areas more densely. Where the magnetic field diverged, the nests were further apart, which is what the scientists had predicted.
The results supported their hypothesis. Indeed, the loggerhead nests moved in tandem with shifts in the magnetic field.
“Our results provide the strongest evidence to date that sea turtles find their nesting areas at least in part by navigating to unique magnetic signatures along the coast,” Brothers told The Science Times.
Scientists still don’t completely know how the turtles detect this magnetic field, but it may be that tiny magnetic particles in their brains help these ancient reptiles find their way. The researchers hope to continue investigating this.
“The only way a female turtle can be sure that she is nesting in a place favorable for egg development is to nest on the same beach where she hatched,” Brothers says. “The logic of sea turtles seems to be that ‘If it worked for me, it should work for my offspring.'”
Brothers added that the results could be used to influence conservation strategies for these endangered reptiles. Pollution, shrimp trawling, development where they nest and other factors have caused sea turtle populations to decline.
He also noted that many conservationists surround loggerhead nests with wire cages. Because the cages are often metallic, the practice may be interfering with the turtles’ ability to find their way home.
Turtles appeared before the dinosaurs, The Rosenstiel School of Marine and Atmospheric Science reports. It is not known when these ancestral turtles began swimming in the ocean to become sea turtles, but over time, these magnificent reptiles have adapted quite well to a marine environment. They are so well adapted, in fact, that they can remain underwater without air for more than 45 minutes, and if they are resting, they can stay submerged for hours at a time.
Organizations like Sea Turtle Inc. are dedicated to saving these beautiful turtles. If you’re interested in helping, contact them here.
