The leatherback turtle has persevered for more than 20 million years but is now in danger of extinction. What will it take for this amazing creature to survive the next decade?

Last month the intense activity on the beaches of the Caribbean island of Trinidad added an important chapter to the survival story of the leatherback turtle.

The leatherback is the largest reptile and one of the oldest living animals on Earth. Measuring up to 6 feet long and weighing up to 800 pounds, this giant travels the farthest of all sea turtles, from nesting areas in warm tropical waters to feeding areas north of the Arctic Circle.

Scientists in Trinidad report that between 250 and 500 of the giant turtles have come ashore to lay their eggs this season, compared to an average of only five turtles in previous nesting seasons. The dramatic increase, say the scientists, is partially the result of laws against killing leatherbacks and taking their eggs.

The leatherback's survival is more in doubt at other nesting locations. Scientists and volunteers from the Earthwatch Institute are working in the Central American country of Costa Rica to understand and protect these creatures.

There are plenty of unanswered questions. How does this huge reptile regulate its body temperature from one extreme to the other? Where do hatchlings go once they leave their nests? How are they able to navigate such long distances and then return years later to the beaches where they were born?

Five years ago, scientists estimated that the number of leatherbacks nesting on beaches worldwide was 34,500, down from 115,000 in 1980. Today, thanks to conservation efforts, the number has increased to 50,000.

• By what percentage did the worldwide turtle population decline from 1980 to 1995?
  

• By what percentage has the population declined between 1980 and today?

The estimates of the turtle population are based on female leatherbacks because only the females come ashore to nest. Once the male turtles hatch, they spend their entire life at sea and are rarely seen by humans, except when they are accidentally caught in fishing nets.

Researchers are finding that the Pacific population of turtles appears to be in greatest danger of extinction, although the Atlantic population is also critically low.

• Look at a world map to compare locations of leatherback nesting colonies in different regions.

What are the reasons for the worldwide decline of leatherback turtles? Human activities are the main culprit—people taking eggs from nests, developers destroying nesting habitats by building beachside homes and hotels, fishing boats accidentally capturing and injuring turtles in nets, plastic bags discarded into the ocean. All are factors driving the species toward extinction.

Earthwatch Institute

Earthwatch Institute puts people in the field where they can assist scientists in their field work. They are part of the action, they learn new skills, and they develop a deeper understanding of their roles in building a sustainable future.

Research scientists have been studying the nesting habits of leatherback turtles at Playa Grande in Costa Rica since 1988.

This narrow 4-mile strip of beach on that country's western coast has historically been one of the largest nesting colonies in the Pacific. In the past, thousands of leatherbacks have come ashore from October to February each year to lay eggs. A female, once she is 6 to 10 years old, will return every 2 to 3 years to nest. During a single season, she will come ashore 7 to 9 times to lay eggs.

The sight of an 800-pound turtle dragging her "mini-tractor"-size body 100 feet up the beach is unforgettable. Within a couple of hours, she digs a 3-foot hole, deposits 80 to 100 eggs, and then returns to the sea before dawn. About 60 days later, the hatchlings emerge. The tiny 2-ounce tortuguitas (Spanish for "little turtle") instinctively make their way back to the water and disappear into the ocean.

Out of 100,000 eggs laid during a season, only about half will hatch successfully. Although it's difficult to estimate accurately, researchers say that maybe one in a thousand of those hatchlings may survive to adult maturity.

• About how many turtles will survive to adulthood from a single nesting season?

Last year at Playa Grande, there were only 120 nesting turtles compared to 1,646 female leatherbacks in 1988.

• What percentage has the leatherback turtle population at Playa Grande dropped during the last decade?

To reverse this trend, three biologists (Dr. Frank Paladino from Indiana-Purdue University and Drs. James Spotila and Richard Reina from Drexel University) have for the past eight years enlisted the help of hundreds of volunteers through Earthwatch Institute, an environmental education organization based in Massachusetts.

Each season, from October through February, teams of Earthwatch volunteers walk the beaches. Together with the scientists, they keep track of how many turtles nest each night and count how many eggs are laid in each nest. They record ID tag numbers of returning turtles and give "new" turtles their own ID tags. Earthwatch teams also help relocate eggs to hatcheries for protection from predators and high tides.

These research and conservation efforts have helped to establish a new national park at Playa Grande, Parque Marino Las Baulas. Now, park officials patrol the beach for egg poachers—people who take eggs illegally. The guards also regulate the number of tourists visiting the beach.

Are these initiatives to increase hatchling survival making a difference? Data from the 1999-2000 season may shed some light on the situation.

As reported on the Web site of the Las Baulas Leatherback Turtle Project, the weekly totals for numbers of nesting turtles appear to have increased since last year.

• Compare, for example, the number of nestings during the week of 11/19/98 with the number during 11/19/99. How much greater was the number in 1999?
  
  
• Do comparisons of other weeks show similar increases?

The number of nestings do not tell the whole story, however. More nests may mean more eggs and more hatchlings in the future. But they do not tell us if the number of individual turtles has increased because a single turtle nests several times during a season.

Researchers must also examine the number of individual turtles coming to nest each season. How many turtles are returning from previous years? How many turtles are "new"? New turtles were perhaps hatchlings 10 years ago. They have now reached sexual maturity and are showing up to nest for the first time.

You actually can count the number of individual turtles on the Las Baulas Leatherback Turtle Project Web site. Scroll down to the Turtle Calendar, and count all the boldface tag numbers. Boldface indicates turtles coming ashore for the first time each season. New turtles include #026, #029, and #030.

• Did the number of individual turtles increase from the 120 last year?
  
  
• What percentage were "new" turtles?

Dr. Reina cautions that it's too early to get excited.

Factors that must be considered include occurrences such as El Niño. Higher water temperatures caused by an El Niño event could have diminished food supplies available to leatherbacks. This may have decreased their numbers during 1998-1999, resulting in the unusually low number of 120.

The real threats to the survival of turtles, Paladino, Reina, and Spotila all agree, are inappropriate fishing methods in which turtles are needlessly injured or killed in fishing nets.

By attaching transmitters to leatherbacks that send signals to satellites, the Las Baulas research scientists have been able to track the movement of turtles and follow their migrations from Playa Grande into the Central Pacific. They have found that many of the tracked turtles hit a zone in the Pacific where the transmitters and the turtles seem to disappear. The scientists suspect that turtles are being caught on long-lines and gill-nets off the coasts of Ecuador and Chile.

Recently conservation groups closed down Hawaii's longline fishing operations in the Pacific. However, dealing with other countries is more complicated. The World Trade Organization recently ruled that the U.S. TED (Turtle Excluder Device) Law could not be enforced on the fleets of foreign importers of shrimp.

As part of a personal crusade, Paladino has chosen not to eat shrimp unless he is sure they are "turtle-safe" shrimp from fleets using TEDs. He has also written to all the seafood chains and fresh-frozen seafood processors in America and pleaded that they continue to purchase only "turtle-safe" shrimp.

Learn More

• To better appreciate the dynamics of population growth, try the following Riverdeep activities:
  
  
  • Middle School Gateways: Factors Affecting Population Growth
    
    
  • Biology Gateways: Population Growth Curve
    
    
  • Biology Explorer: Observing Population Growth
    

• Learn about another endangered species in the Riverdeep Today article, "Manatees or Humanity?"

More Links

• Get more information about the Earthwatch Institute's scientific research on leatherback turtles:
  
  
  • Costa Rican sea turtles
  
  
  • Teams and scientists working at Playa Grande, fall 1998
    
    
  • Teams and scientists working at Playa Grande, Jan.-Feb. 1999

• The Caribbean Conservation Corporation provides informative and interactive maps on turtle migration.
  
  
• The organization EuroTurtle provides an in-depth look at turtle biology.
  
  

• Get Biology and Conservation of Sea Turtles.

Meg Warren is the Manager of Earthwatch Institute's Collaborative Technology Projects. In 1998 she was a team member of the Costa Rican Sea Turtle Project.