Turtles





**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.

**Adelita's Amazing Journey** 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. THE JOURNEY OF ADELITA The journey of Adelita the sea turtle is the true story of a resilient loggerhead sea turtle, wearing a state-of-the-art satellite transmitter, who made her way from Baja California, Mexico to the shores of her birthplace in Japan, some 6,000 miles and 368 days across the Pacific ocean. This is a heart-warming story of an endangered species that speaks to the human condition about the struggle for survival and freedom. Caught by a fisherman in the Gulf of California, Mexico, she was raised in captivity. Nobody knew her age, maybe a few years old based on her size (about as big as a large plate). Mexican researchers eventually got hold of her and decided to put her in captivity, becoming involved in genetic studies. People were still-hunting and eating turtles in the area. Eventually Adelita met Dr. Wallace J. Nichols, then a graduate student studying turtles in Baja California Sur (now a PhD and co-founder of SEE Turtles). J. and his colleagues wanted to know where the loggerheads came from; some nest along the nearby Mexican Pacific coast and others as far away as Japan. With the turtle quickly outgrowing its tank, the researchers decided to release her back to the ocean. Satellite tagging, following an animal’s movements with transmitters, was a new tool in studying wildlife. Nichols was given a recycled transmitter and a fisherman helped to figure out how to attach it to her shell (see photo at right). With no idea if the transmitter would work or where she would go, the team put Adelita into the water on August 10, 1996. Having spent most of her life in small tanks, at first she didn’t realize she was free and swam around the outside of the tank. Then she figured it out and disappeared into the Pacific. For almost exactly a year, the young loggerhead made its way west, past Hawaii, eventually reaching the coast of Japan (see map at right). Her journey measured 9,000 miles, crossing a barren area of ocean that scientists previously believed was a barrier to migration. The first creature tracked across an entire ocean, Adelita’s story ended in mystery. The transmitter stopped sending signals off the coast of Japan, in an area frequented by fishing boats. Despite the mystery, Adelita’s Journey had a far reaching impact, changing perceptions about turtle migration, how different countries are linked by wildlife, and capturing the imagination of thousands. At one point during the trip, as many as 50 students would contact the researchers per day, representatives of thousands of children watching one of the internet’s first live reality shows. Now fishermen from Baja, Hawaii, and Japan collaborate on ways to protect turtles while fishing (see photo at right). Many schools in the US, Mexico, and Japan have integrated conservation studies and programs, including the satellite tracking of sea turtles and their incredible travels across and around the Pacific Ocean. They are able to log on to seaturtle.org and follow the progress of these wondrous prehistoric creatures.

__**Pictures of Adelita**__



__**Map of Adelita's Journey**__

Check out 'Last Journey for the Leatherback' (26mins) about the plight of the leatherback turtle and the efforts humans are taking to save them from extincion. []

Tasks:

After watching 'Turtle: An Incredible Journey' and reading the above information, use your research skills to find out about one other type of turtle. Create a fact file on the turtle that includes information such as appearance, food, habitat, migrations, nesting etc.