Researchers have learned a great deal about how this curious creature could make such a phenomenal voyage. Some of the most valuable information was gained from a single voyage. Scientist Wallace J. Nichols released the captive loggerhead turtle, Adelita, into the Pacific a decade ago. Over the course of a year, Adelita did what no sea turtle had ever done before, she took researchers and turtle enthusiasts along on her journey, to her beach, to nest. Since then, researchers have shed much light on how sea turtles like loggerheads navigate the astounding trip. One of the more fascinating aspects of this navigation is the turtle’s use of magnetic mapping to chart its course.

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Online content for Voyage of the Lonely Turtle was originally posted April 2007.

More than a decade ago, Wallace J. Nichols had the idea to satellite-tag an adult female loggerhead sea turtle named Adelita. Over the course of about a year, Adelita, Nichols and a great many internet onlookers made a 9,000-mile voyage from Mexico across the Pacific to nesting grounds in Japan. Adelita was the first animal ever tracked across an ocean basin, turtle or otherwise. Her story was also the first discovery that loggerheads make such a long journey to nest. NATURE spoke with Nichols on the ten-year anniversary of the trip.

Q: WHO WAS ADELITA?

A: Adelita was a loggerhead sea turtle who was caught by a fisherman in the Gulf of California. She was raised in captivity. We weren’t quite sure how old she was. We think she was just a few years old based on her size. She was as big as a large plate. Mexican researchers eventually got a hold of Adelita and decided to put her in captivity. People were still-hunting and eating turtles so they felt that would be safer for her. She became part of genetic studies for a few years.

WHY DID YOU DECIDE TO RELEASE HER AND FOLLOW HER JOURNEY?

I was a graduate student studying these turtles in Baja. We started asking where all of these loggerheads in Baja were coming from, so we started searching for a loggerhead-nesting beach. We knew there was a nesting beach in Japan but thought that was way too far for loggerheads to journey to. So we had a big mystery on our hands. How did they make that trip?

Adelita had been facing a life in a tank in a research facility. As she grew, we knew we were not prepared to hold a growing loggerhead. So we had very few options. We could hold her indefinitely in captivity or release her. We decided it would be great to get Adelita out.

At the time, people were starting to use satellite telemetry but the early efforts were not so successful. Transmitters are expensive but I had a recycled transmitter and decided to try using it for Adelita’s journey. A fisherman helped me figure out how to attach this transmitter to a turtle shell. But we had no idea if this would work if the transmitter would fall off or the batteries would go dead.

Adelita

WHAT DID YOU THINK WOULD HAPPEN? WHERE WOULD SHE GO?

There were lots of unknowns. First of all, she had lived most of her life in captivity so she could just have revealed that captive turtles do odd things. We didn’t know if she could survive in the wild. But we knew she was healthy. She would eat anything dead or alive. If your sunglasses fell in the tank, she would eat those. Basically, she would eat whatever she found. Turtles are not particularly social animals. There’s no pod she would have to join. There’s no parental care. They are somewhat carnivorous. They’re also highly instinctual. She was very healthy in terms of fat storage. And we knew she was sexually mature because she was big enough. My concern was: was she in good enough shape for it?

WHAT WERE THE FIRST MOMENTS OF THE JOURNEY THAT YOU WITNESSED LIKE?

It was pretty amazing. This turtle spent all of her time in tanks 10 feet in diameter across. When she first got out of the tank, she kept swimming around the outside of the tank and stopping as if she was planning on hitting a wall. But there was no wall. I took a video of her swimming away. It’s pretty interesting. At one point, when she realized nothing was holding her in, she just took off. She went out into the Pacific Ocean and just swam across it; she swam continuously for 368 days. What was interesting was that in captivity she was always hanging out on the west side of the tank-the direction of Japan.

HOW DID THE INTERNET PLAY A ROLE IN HER JOURNEY?

At the time, the internet was new so it was a new tool we had of letting people know what Adelita was doing along her journey. It was one of the only live shows on the web at the time. But it’s pretty amazing to think about people stopping their day and thinking about what Adelita was doing. It’s pretty mind-blowing. It changes people’s perspective and helps them understand how big the Pacific Ocean is.

Also, I needed to share the data I was getting. I could sit there and accumulate data on my hard drive or share it. It became my responsibility to share the information and to answer questions. So for about a year, I had 50 students a day emailing me questions about Adelita.

WHAT DID YOU LEARN FROM ADELITA?

The East Pacific Barrier between Japan and Mexico is known as the East Pacific Desert. It’s an unproductive clearwater. It was thought that animals couldn¹t cross because it was so unproductive. The idea was that this was a barrier. Turns out to be completely wrong. Adelita was the first piece of the puzzle proving that was wrong. Now we know lots of species do the same thing. And now, all kinds are being tracked through the Pacific. It’s revolutionary in terms of the number of animals being tracked and what we know about the ocean today.

WHAT EFFECT HAS ADELITA HAD ON TURTLE CONSERVATION?

Adelita has raised this idea that all of these places are connected in the life history of a turtle. This was not something people knew about so much. Now it¹s just standard but back then it was a big lesson.

Adelita changed the way people in Baja and Mexico and Japan thought about sea turtle conservation. This turtle has opened up all kinds of connections between Japanese, Mexican, American people. We need to collaborate with people at the other side of the planet. Protecting nests in Japan only will get us poor results if the turtles are not safe in Baja.

What we learned from Adelita has also changed the way fishermen think about sea turtles. The animals themselves are more interesting to them. Given the opportunity to leave them alive rather than cut them open, take out their liver and throw them back in ocean, they might leave them alive now.

HOW MUCH DID YOU KNOW ABOUT WHERE ADELITA VENTURED ALONG HER JOURNEY?

We didn’t know exactly what Adelita was doing but we were pretty sure about where she was. The satellite tracking of the locations were really accurate — up to 150 meters. You could draw a circle and she’d be in it-about as large as a football field. This is pretty tight when you think in terms of the entire Pacific Ocean. Most of the time, Adelita was in very deep water, not close to the bottom. When she was closer to the coasts, it was a bit different. We knew she would encounter females or rest in caves.

DID YOU WORRY ABOUT HER SAFETY?

Once Adelita started swimming to Japan, I was worried about her daily. She’s trying to swim home and all sorts of threats face her. I experienced hope and fear imagining where she’s going. Every day, not knowing if that would be her last day, was emotional. Maybe the transmitter would fall off. Or the battery could go dead. But unbeknownst to her, millions of kids were hovering over their computers to track her journey. It felt like we were all on her back.

HOW DID YOU LEARN OF THE END OF HER JOURNEY?

Finally Adelita made it to Japan and the hope was that she would find a mate and lay eggs that would become hatchlings. But that’s not the way it worked out. At the time, I wasn’t sure what had happened. The data was erratic. Eventually I went to Japan and went to the last location where she was recorded. It was a fishing port with squid fishing boats. The fishermen told me that summer they had caught a lot of loggerheads so Adelita could have been caught by a fisherman. But it was still fuzzy. Maybe she was caught and the transmitter pulled off. Maybe she was thrown back in. I didn’t want to come out and say Adelita is dead.

But I started to see this as an opportunity to tell a real story. Once they’ve reached maturity, they’re out of reach of predators except for sharks and their biggest threats are hooks, nets and plastic bags. The reality is that turtles die in nets and on hooks. So here was this opportunity to tell that part of the story.

WHAT DOES YOUR RESEARCH FOCUS ON NOW?

We’re still tracking turtles. Right now, we’re tracking over 50 turtles of various species.

The focus is on protection for the key areas of their life cycle. Over the years, people have concentrated on nesting beaches and I think we need to couple that with protecting feeding areas because by-catch rates in Mexico in these places are really high. So we’re working on getting a federal-reserve designation for a Baja feeding hotspot. We¹re working with the Mexican government to declare it a marine conservation environment. And we’re working with the fishermen, who are actually really in favor of it. One thing we’re doing is we’re working on ecotourism opportunities: if fishing opportunities are taken from the fishermen, we can work on other financial incentives, like whale-watching tours.

THE FILM WASN’T ABOUT ADELITA BUT IT WAS BASED ON HER VOYAGE, WHAT DID YOU THINK ABOUT THAT?

Adelita’s journey is a really inspiring story. Her story connects Asia, Latin America, and the US. It gets into people’s hearts and minds. But what’s compelling about it is that it’s a real story; not a Hollywood story. The trend in nature filmmaking is to show the edgy, dangerous situations. I’ve been asked, “Can you show me turtles getting eaten by a shark or turtles gone bad.” But this film is just the voyage of a lonely turtle. It’s just that. It’s not about being edgy. It’s a peaceful story. It isn’t trying to be MTV. At the same time, this feels fresh. It’s an epic, transoceanic story with incredible footage.

Adelita was really just the beginning. We’re in the middle of this. She was by no means just a one-off.

Voyage of the Lonely Turtle depicts a loggerhead sea turtle’s remarkable journey across an ocean back to its familial nesting site. Venturing across thousands of miles of open ocean to emerge on the very beach where it was born years earlier, the loggerhead performs one of the most remarkable feats of orientation and navigation in the animal kingdom.

“Turtles do return to the beach where they’re born,” says Wallace J. Nichols “Sometimes it will be hundreds of miles away. Sometimes thousands. For a loggerhead in California it was thousands.” That turtle, and the one the NATURE film is based on, was called Adelita. A captive loggerhead who trekked from her feeding site in Baja, Mexico to her place of birth in Japan, Adelita was the first animal ever tracked across an ocean basin. A decade ago, Adelita made her astounding journey of 9,000 miles, defying exhaustion and death, just to lay her eggs on one very special beach. Though Adelita’s trip shed new light on transoceanic migration, Nichols and other marine researchers have continued to fill in more of the unknowns in sea turtle migration.

Green turtle on the beach

HOW DO THEY DO IT?

“Turtles are master navigators,” says Wallace J. Nichols, “we can barely even imagine it.” With a lack of visible landmarks, strong currents, poor vision and the inability to raise their heads more than a few inches out of the water, navigating through thousands of miles of featureless ocean requires serious skills of another kind. But researchers believe these abilities are instinctual rather than strategic.

Early experiments with hatchlings seem to prove that sea turtles have the ability to detect the earth’s magnetic fields even before they venture into the ocean. Detecting the earth’s magnetic field could enable a sea turtle to determine its latitude and longitude, and thus to plot its course or change its course along its migratory route.

“It’s sort of like an extra sense,” says Nichols. Along with visual cues like sea mountains, which are potentially used as signals as turtles move away from the continent, or other sensory stimuli like smell, detecting magnetic fields is a key feature of a sea turtle’s navigational abilities.

WHY DO THEY DO IT?

Even with these astonishing skills that allow them to find their way across open ocean to a destination, the journey still offers considerable risk to sea turtles. Deadly predators, the raging sea, utter exhaustion-in the face of such threats, sea turtles head out for distant shores when it comes time to nest, even though they are surrounded by a coast of beaches in their feeding grounds. Researchers have been intrigued by this particular aspect of sea turtles for years. A creature that risks life and limb because only one beach will do appears to take fastidiousness to the extreme.

Ancient programming, in essence, explains this mystery. A particular nesting choice may reflect centuries-old conditions when temperature, beach profiles or the lack of predation made some areas preferable to sea turtles. “A turtle beach is a special kind of beach,” says Nichols: “the slope, humidity, temperature, types of predators.” In the world of sea turtle real estate, nesting beaches are prime property. They must offer open-water access, especially for larger sea turtles such as leatherbacks and loggerheads. They should have just the right slope so that a mother turtle can hoist herself to her nesting spot but not worry about flooding. The texture of the sand should be loose enough for gas diffusion, yet dense enough to prevent collapse during digging. Nearby offshore reefs and dune vegetation are both pluses. The location of a nest is critical to the survival and development of eggs and hatchlings. If a nest is too near the water, the eggs will become saturated with sea water and fail to develop. If it is too far up the beach, many threats arise: the roots from vegetation can invade the nest; the nest will be closer to predators; the hatchings will have a longer way to travel to reach the water.

In the end, turtle real estate decisions are not too difficult for humans to understand. The determination to make an exhausting, risky journey through the territories of predators and the daunting unknown comes down to historical experience. “If you were born on a beach,” says Nichols, “and it worked for your mom, it will work for you. Their strategy is to go back to the beach they were born. It’s been proven.” “To nest where they feed would represent a break with tradition,” says Nichols. As contemporaries of dinosaurs, the sea turtles have been employing their migratory strategy for a long time, and it looks like they’ll be sticking with it for the immediate future. “Pick a good beach and hatchlings survive. Clearly over millions of years, turtles have done just that,” says Nichols.

With all their ancient history and remarkable abilities, turtles today are faced with a relatively new danger, and one that may prove their undoing: the activities of humans are the greatest threat to the future success of sea turtles. In the year 2000, 1.4 billion hooks were cast into the world’s oceans through industrial fishing. These hooks snagged more than 200,000 loggerhead turtles and killed tens of thousands of them. Humans are also threatening sea turtle nesting beaches through actions that lead to beach erosion. We are disrupting nesting itself with our artificial lighting. Researchers believe that the damage we cause is likely have lasting effects on future nesting populations. With their life cycle dependent on specific nesting beaches and their need to roam the open ocean freely without the threat of becoming a by-catch, sea turtles must now depend on the consideration of humans to ensure that their epic journeys continue in future generations.

Photo © Mark Fletcher

As master navigators of the sea, sea turtles like loggerheads have confounded scientists for years, setting off a research frenzy to uncover the secrets to their navigational expertise. Research on sea turtle navigation began with acclaimed zoologist Archie Carr in the 1950s. It was Carr’s 1956 book, The Windward Road, that first brought attention to the extraordinary homing skills of sea turtles. In the half century since then, the search has never abated. Through the years, scientists have collected a substantial pool of data on this “extra sense,” as Carr called it. They have tried to understand how two-inch long hatchlings can embark on a solo journey across open ocean, finding their way to a feeding beach thousands of miles away. And how adult turtles are able to navigate back thousands of miles with pinpoint accuracy to their natal beach. Researchers have hypothesized that it is a built-in global positioning system that guides turtles on these epic journeys. Though many questions remain, scientists have found that a sea turtle’s GPS unit is not one guided by satellites. Instead, it relies on one of the strongest forces on earth-the planet’s magnetic field.

Scientists believe loggerheads detect magnetic fields and react to that information.

The Earth’s magnetic field acts as a shield from charged particles that emanate from space, mainly from the sun. The field deflects the speeding particles toward Earth’s Poles. The magnetic field is like an enormous bar magnet that is strongest near the poles and weakest near the equator. The intensity results from the fact that the field lines emerge from the southern pole of the Earth, wrap around the planet, and re-enter in the northern half. The Earth’s magnetic field comes from a very deep ocean of liquid iron and nickel that sits above the planet’s inner core. This “outer core” is an electrically conducting fluid in constant motion. The motion of the conducting fluid generates electric currents and, as a result, a magnetic field.

Magnetic field can be determined at a particular location by knowing its inclination angle, or the isoline of inclination. This angle varies with latitude. Points along the Earth have their own angle of inclination specific to their location. At the equator, where field lines are parallel to the Earth’s surface, the inclination angle is said to be 0°. North from the equator, field lines become progressively steeper. At the northern magnetic pole, the field lines are directed almost straight down into the Earth and the inclination is said to be 90°. Intensity, or strength, of field lines at a given location can also be described.

Research on sea turtles suggest these animals possess a type of compass that enable them to detect both the direction and strength of the earth’s magnetic field, and this allows them to determine their location. As they move from place to place, animals like turtles essentially build a magnetic map in their minds. Just as a compass needle aligns with the north-south magnetic axis, the turtle’s compass relays directional information to it, providing it with a reference for its position. Researchers believe that turtles use such prompts in tandem with other environmental information such as underwater volcanoes or smells. Sensing magnetic signals is not a skill confined to sea turtles. Salamanders, sparrows, spiny lobsters, hamsters and bacteria all use magnetic field to get along in the world.

Recently scientists have shown how loggerheads detect magnetic fields and react to that information. In one recent study, baby loggerheads were observed while exposed to different magnetic fields that simulated three key locations along their migratory route. The direction in which each animal swam was recorded and analyzed. Animals exposed to a simulated northern field responded by swimming south while those in subjected to a simulated southern field swam toward the north. In each case, turtles swam in the general direction that would have taken them homeward, had they been swimming in the ocean and encountering the earth’s actual magnetic field. What’s even more fascinating, these turtles had been hatched in captivity and never had any experience of the open ocean. So it emerges that the loggerhead’s navigational abilities are probably innate and not learned.

Other studies on hatchling loggerheads have shown that even one-day-old newborns detect magnetic inclination angle as well as field intensity to navigate their way across the world. Some researchers suspect that turtles may geonavigate by detecting both magnetic features and then using a form of “bicoordinate” magnetic navigation. Such a multi-variable system might enable turtles to return to a home area from nearly any oceanic location. For example, if a turtle learns the inclination angle at a given feeding area along the coast, it might simply compare that information to the inclination angle that exists at its home area. If the inclination angle is too steep, the turtle knows that it is too far north and therefore needs to travel south to reach home. If the angle is too shallow, then the turtle knows it is too far south. They can also apply the technique to detecting isolines of magnetic field intensity. Researchers believe the geomagnetic abilities of turtles becomes more sophisticated and complex as they grow older.

While there is undoubtedly more knowledge to gain in how sea turtles process magnetic field cues to navigate, researchers have made astonishing leaps since the days of Carr. With luck, sea turtles will be able to make continued journeys of epic proportions and researchers will be able to study those journeys and unravel their mysteries.

Adelita’s Story
http://www.turtles.org/adelita.htm
Website describes Adelita’s remarkable journey a decade ago. Maps and graphics included.

The Ocean Conservancy
http://www.oceanconservancy.org/site/PageServer?pagename=home
Website associated with researcher Wallace J. Nichols. Focuses on critical ocean conservation issues such as restoring American fisheries and reducing human impact on wildlife.

Sea Turtle Conservation Network/Grupo Tortuguero
http://baja.seaturtle.org/
A network of people and organizations working for the recovery of Baja California’s sea turtles. Efforts focusing on fishing communities along the length of the 1000 mile-long peninsula and support enforcement of Mexico’s strong conservation laws.

Caribbean Conservation Corporation
http://www.cccturtle.org
The mission of the Caribbean Conservation Corporation to ensure the survival of sea turtles within the wider Caribbean basin and Atlantic through research, education, training, advocacy and the protection of the natural habitats

Seaturtle.org
http://www.seaturtle.org/tracking/
A Web site that tracks the courses of over 1500 sea turtles. Allows users to sponsor their own sea turtle. Adelita’s complete migration can be found here.

Personal web site of Dr. Wallace J. Nicols
http://web.mac.com/wallacejnichols/iWeb
Dr. Wallace J. Nichols was the first researcher to place a satellite tag on a loggerhead sea turtle. His research led to the discovery that loggerheads make a long journey to nest. He is Co-Director of Ocean Revolution, an international program developed to inspire and empower a new wave of young leaders to protect the oceans.

Related episodes:

The Reptiles: Turtles and Tortoises
http://www.pbs.org/wnet/nature/reptiles/turtles.html
This Nature program takes a close look at the reptiles that have changed little in 200 million years.

Books:

Bernard Devaux, Bernard De Wetter. On the Trail of Sea Turtles. New York: Barrons Educational Series Inc, 2000.

Carr, Archie. The Windward Road. New York: Alfred A. Knopf, 1956

Carr, Archie. The Reptiles. New York: Time-Life Books, 1977.

Carr, Archie. The Sea Turtle–So Excellent A Fishe. Austin, Texas: University of Texas Press, 1986.

Davidson, Osha Grey. Fire in the Turtle House. New York: Public Affairs Press, 2002.

Rudloe, Jack. Time of the Turtle. New York: Truman Talley Books–E.P. Dutton, 1989.

Safina, Carl. Voyage of the Turtle. New York: Henry Holt & Co., 2006.

Turtle Links
http://www.tortoise.org/cttclink.html
The California Turtle & Tortoise Club’s guide to turtle and tortoise resources.

Turtles on Death Row
http://www.conservation.org/xp/news/press_releases/2003/051503.xml
Top 25 species of endangered turtles.

Helmeted Terrapin
http://www.eti.uva.nl/Turtles/Turtles3a.html
Facts and photos about this African hunter.

Interesting Turtle Facts
http://www.petplace.com/Articles/artShow.asp?artID=4385
Amazing tidbits about this ancient creature.

American Tortoise Rescue
http://www.tortoise.com
A nonprofit organization that rescues and rehabilitates tortoises and turtles.

World Chelonian Trust
http://www.chelonia.org
Organization that promotes the conservation of all tortoises and freshwater turtles.

Turtle Homes Rescue
http://www.turtlehomes.org
A nonprofit organization dedicated to the safety and welfare of turtles and tortoises worldwide.

The Turtle Ranch
http://www.theturtleranch.com
Web page of a sanctuary for turtles and tortoises who cannot survive in the wild.

Turtle Facts
http://www.angelfire.com/realm2/spellcast/turtlefacts.html
More about the odd and wonderful world of turtles.

Turtle Stewardship
http://www.wtgrain.org/turtle/w3ncare.htm
Useful tips and how-to’s.

Books

Dodd, C. Kenneth. NORTH AMERICAN BOX TURTLES: A NATURAL HISTORY. Norman, Oklahoma: University of Oklahoma Press, 2002.

Ernst, Carl. TURTLES OF THE UNITED STATES AND CANADA. Washington, D.C.: Smithsonian Institution Press, 2000.

Orenstein, Ronald. TURTLES, TORTOISES AND TERRAPINS: SURVIVORS IN ARMOR. New York: Firefly Books, 2001.

Palika, Liz. TURTLES & TORTOISES FOR DUMMIES. New York: John Wiley & Sons, 2001.

Wilke, Haarmut. TURTLES AND TORTOISES: CARING FOR THEM, FEEDING THEM, UNDERSTANDING THEM (Family Pet Series). New York: Barrons Educational Series, 1998.