Dancing Baby Sea Turtles Help Researchers Unravel the Mysteries of Their Navigational Superpowers
Loggerhead turtles can identify specific magnetic signatures, according to a new study, hinting at how the aquatic reptiles manage to return to the same foraging and nesting sites over and over again
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Sea turtle migrations are impressive: These aquatic reptiles swim thousands of miles across the open ocean to return to the same foraging grounds and nesting sites. They don’t always take the shortest, most direct route, but they do eventually get to where they’re going.
Researchers have long marveled at these epic journeys. Over the years, they’ve been able to deduce that sea turtles navigate using Earth’s magnetic field—as though they have a built-in GPS system. But scientists have never understood exactly how the reptiles are using the magnetic field to orient themselves.
Now, a new study is offering more insights into this advantageous behavior. Baby loggerhead turtles can identify specific magnetic signatures, according to a new paper published Wednesday in the journal Nature.
“It is amazing that sea turtles have access to a wealth of invisible information that they use to navigate in ways that are hard for us to even imagine,” says study co-author Catherine Lohmann, a zoologist at the University of North Carolina at Chapel Hill, to Cosmos magazine’s Imma Perfetto.
The experiments suggest loggerheads have two different magnetic senses: one that they use like a compass, which tells them the general direction to travel in, and another that they use for mapping, which helps them home in on specific coordinates.
Scientists say these findings likely help explain why sea turtles are such skilled navigators.
“It’s a new way of thinking about how turtles are using the magnetic field to navigate,” says Katrina Phillips, a marine ecologist at the University of Massachusetts Amherst who was not involved with the paper, to New Scientist’s Chris Simms. “We still don’t understand how they’re even perceiving the magnetic field. So, this is getting at what is going on mechanistically.”
To unravel the mysteries of sea turtle navigation, researchers relied on an adorable behavior they noticed while studying the reptiles in captivity: When baby loggerheads in a laboratory know they are about to be fed, they dance. That means, when food is on its way, the juveniles lift their heads above the water line, flap their flippers and, often, spin around in circles.
Researchers realized they could use this habit to potentially study the loggerheads’ relationships to magnetic fields—by conditioning them to associate a specific magnetic field with food in a similar set-up to Russian physiologist Ivan Pavlov’s famous experiments with dogs and bells.
Earth’s magnetic field is not the same everywhere. It differs predictably from place to place, which means each location on the planet has its own unique magnetic signature. Researchers wondered if they could use the food dance response to show that loggerheads can identify specific magnetic signatures.
They placed individual juvenile turtles in tanks that were surrounded by coil systems, which created different magnetic field signatures.
In one experimental condition, they produced the magnetic signature for a location in the Gulf of Mexico and fed the turtles. In another, they created the magnetic signature of a site near New Hampshire and did not feed the turtles. They exposed the loggerheads to each field for similar amounts of time during a two-month conditioning period. It didn’t take long for the baby turtles to start dancing when presented with the food and the Gulf of Mexico magnetic signature.
Later, over several days, researchers placed the turtles back in that same magnetic field but did not feed them. The turtles danced anyway, which suggests they recognized the specific magnetic signature associated with food. Even up to four months later, some turtles danced in the Gulf of Mexico magnetic field.
They got similar results when they used magnetic signatures from other places, including sites near Cuba, Delaware, Maine, Florida and more, per CNN’s Julianna Bragg.
Scientists suspect sea turtles can remember magnetic coordinates for years, an adaptation that helps them survive in the dangerous—and often deadly—ocean ecosystem.
“It’s very important for young sea turtles to outgrow predator mouths as quickly as possible,” says Jeanette Wyneken, a marine biologist at Florida Atlantic University who was not involved with the research, to Scientific American’s Jack Tamisiea. “[The turtles] need to efficiently locate food to sustain their development and increase their chances of survival.”
In another similar experiment, researchers added radiofrequency waves—which are used in cellphones and radio transmitters—to see what effect, if any, they had on the turtles. Scientists had previously predicted that animals might be sensitive to the Earth’s magnetic field because of chemical reactions in their bodies, and these waves interfere with those processes.
When exposed to radiofrequency waves, the turtles could still perceive and identify the magnetic field signatures, but their ability to orient themselves with an internal compass appeared to be disrupted. This suggests sea turtles have two separate senses for perceiving magnetic fields.
“The magnetic map sense is a positional sense, kind of like a GPS, and their compass sense tells them which way to go,” says study lead author Kayla Goforth, who is now a biologist at Texas A&M University but conducted the research as a doctoral student at the University of North Carolina at Chapel Hill, to New Scientist. “This is probably how they’re getting back to important ecological locations such as feeding grounds and nesting areas.”
Though the study offers new insights into sea turtle navigation, many questions remain. Scientists are still searching for the underlying body part that allows the reptiles to pick up Earth’s magnetic fields in the first place.
“We know that for the visual sense, you have eyes; for the sense of smell, you have a nose; and for hearing, you have ears,” says Goforth in a statement. “But no receptor like that has been identified for the magnetic sense, and the mechanism remains unknown.”
