Final: The Decline of the Leatherback Sea Turtle (sorry, I sent the rough draft b4)

This topic submitted by Brandon J. Meyer ( brjmeyer@indiana.edu) at 10:01 PM on 5/14/02.

Our group prepares to leave Lighthouse Cave, San Salvador, Bahamas.

Tropical Field Courses -Western Program-Miami University


From times as early as the dinosaurs roamed the earth, the Leatherback sea turtle (Dermochelys coriacea) has ruled the Pacific Ocean, dominating as the largest of all eight sea turtle species, as well as the world’s most ancient living reptile (Tyson 54-57). Weighing around 800 pounds each and reaching lengths to about 6 feet, these massive creatures are unique due to their soft and leathery backs. Ironically, unlike most turtles, the home that they carry with them is not actually a shell, but a series of interlocking bony plates reinforced by a layer of profuse, skin covered fat. Despite their awkward size and appearance, their body is very well equipped and aids them suitably in swimming. The sleek design of their body, highly tapered carapace, and smooth skin makes swimming long distances a great ease. As a result, leatherbacks can dive deeper and migrate farther than any other reptile. Leatherbacks have been known to swim in all of the world’s oceans, as well as live most of their lives down deep at great depths. Because of their collapsible body frame with minimal fused ribs and a low bone-to-catilage ratio, these amazing turtles can withstand pressure up to 1,500 PSI, which is near the depth of 3,000 feet deep (Tyson 54-57). On top of that, leatherbacks get all of their energy from eating only jellyfish. What a diet! (Gilbertas 30-36)

Even with its unique attributes, the leatherback is headed towards extinction. In the past two decades alone, the survival of the Leatherback turtle population has seriously declined at an alarming rate of about 1/3 their total numbers each year. The only time the leatherback can be studied is when it comes back year after year to the nesting beaches to lay eggs in the sand. At Playa Grande in Costa Rica, the world’s largest nesting colony (Knight) and 4th largest colony of the species (Kaufman 1109), Dr. James Spotila of Drexel University in Philadelphia has been studying all that he can about the leatherback during this time. Since 1988, he has kept data over all of the number of returning nesting females. In 1988, the number of nesting females that laid eggs on the beach totaled 1,367. In 1999, however, the number has declined to only 117 (Kaufman 1109). If the decline in nesting females stays on target, the leatherback species will fall around 50 in 2003 and may in fact go near extinction by the year 2005 (Allen 10). Spotila utilizes the leatherback nesting period to find out anything he can because it is the only time that anyone can get this close to the leatherback species. After all, they spend 99.9% of their lives at the bottom of the ocean (Tyson 54-57). That’s part of the problem right there.

There are many reasons why the species of the leatherback turtle is declining at an unpredictable rate. At sea, while swimming, the turtles are highly prone to getting entangled in funnel shaped shrimping nets (Gilbertas 30-36). Commercial fishermen are a prime threat to the survival of leatherbacks. If a turtle gets tangled up in any kind of fishing net, most of the time they cannot make it up for air and as a result, die at sea. Other times leatherbacks get confused and chomp on what they think is a jellyfish, but in reality is only a net or piece of garbage. Not only do the leatherbacks have trouble in the seas, land is a different story. While laying eggs on a beach, some poachers hunt sea turtles for their meat and eggs. They are a delicacy in Asia and are quickly sold there for a nice sum of money. Others use leatherbacks as bait for shark fishing. Today tourists are also a big problem; they accidentally disrupt turtle nests and proceed to take the eggs home and keep the baby turtles as pets (Tyson 54-57). On top of that, many people decide to move to the ocean and build homes
right on top of the nesting sites themselves!

Despite all of the interruptions, the process of nesting and hatching has been a ritual for the leatherback for millions of years. When the moon is right, the female leatherback makes her way out of the choppy waves onto the dry beach just above the tidal mark. After finding the perfect location, the nester proceeds to pile a mound of sand onto the site before digging an oval shaped hole with her spoon-like hind flippers. After digging about two and a half feet down, the female proceeds to lay about 70 circular white eggs. Following soon after come 30 sterile eggs that act as a protection barrier and help incubate the nest along with the packed sand that is placed on top (Gilbertas 30-36). The whole process takes about two hours to complete and it is evident that it is an exhausting task due to the tears the worn out turtle sheds. Inside the incubation chamber, different temperatures determine what the sex of the turtle will be. If the temperature is below 29.5 degrees Celsius, then males will be born. In return, any temperature above that results in a female (Gilbertas 30-36). As soon as the first newborn pokes its way through the shell, a chain reaction goes off. Every egg then breaks open and a mad rush of baby turtles attempt to make their way down towards the surf.

Even though many eggs are laid, and lots of little baby turtles are ready to escape their eggs, there are many dangers that lurk throughout this process. Before hatching, the eggs are sometimes interrupted by other nesting turtles who happen to dig new nest close by. Many are also dug up by mongooses and dogs who roam the beaches (Tyson 54-57). Other threats to the eggs include burrowing mole crickets and and sand crabs. Once the babies emerge from the sand, many species wait by to snatch to new born, soft-shelled critters. Such animals include owls, black vultures, herons, crab-eating raccoons, shore crabs, ariid catfish and even nesting shark in the bay (Gilbertas 30-36).

Since Dr. Spotila started his research on the leatherback turtle two decades ago, the effort to save the species has increased dramatically (Allen 10). Spotila discovered that the key to unlocking more information about leatherbacks lied where the turtles went after birth and where they journeyed when they weren't nesting. The idea was to find some method of tracking the turtle with a device of some sort. The first to do so was a man by the name of Eckert who used instruments called microprocessor-contolled time-depth recorders (TDRs) which were earlier used to track penguins and seals when they dived at different depths (Tyson 54-57). With the help of the devices attached to the shells of the leatherbacks, a whole new world opened up for scientists trying to solve the sea turtle mystery. Leatherbacks, as well as other sea turtles, migrated great distances year round. According to the TDRs, every time a leatherback would come up for air, a satellite signal would fix on its location and transmit it to laboratories across the globe. The longer the turtle stayed up for air, the more precise the location the satellites sent. This, however, became a quick problem. For TDRs to get a solid fix, the leatherback must be surfaced for 5 minutes in order to send the signal. Unfortunately, leatherbacks don’t wait 5 minutes every time they come up for air. Leaping over the problem, Eckert quickly thought of a new system that would use the Global Positioning System (GPS) to follow the turtles on there migration patterns (Tyson 54-57). With the advanced technology of this tool, satellite signals could be sent and received in a time of less than 20 seconds. This greatly improved the accuracy of the leatherback migration research.

With the GPS, collecting data was very easy. It also enabled scientists to get a better look at where the migration patterns led to. What the data showed was very surprising to Eckert and Spotila. According to the satellite signals, the turtles all followed the same underwater pathway like a highway at the bottom of the sea (Monastersky 342). What was even more amazing was the fact that different leatherbacks followed the same trail, even years apart from one another. With knowledge of this migration path way, scientists can warn fishing boats to stay away from these areas in hopes to eliminate many leatherback deaths in the future.

Besides studying the leatherback migration patterns, other experiments are beginning to yield new information about these mysterious animals. A study on heart rate discovered that leatherbacks do not experience a dramatic bradycardia during routine diving (Southwood 1115). When descending, the heart rate of the turtles slowed dramatically. Because this is so, they can reach outstanding depths. When resurfacing, the heart rate then speeds back up to normal. Another study about blood perfusion in leatherbacks led to the conclusion that they have a cardiovascular physiology that prevents overheating in warmer waters and minimizes the loss of body heat in colder waters (Penick 125A). This idea comes from a survival method used by the dinosaurs millions of years ago called gigantothermy (Spotila 206). This method allows the leatherbacks to survive in colder areas due to the restriction of blood flow to the body. As a result, the whole body core of the turtle is kept warm.

With advancing technology, many new things are being discovered about the leatherback turtle today in hopes to stop it from going into extinction. Even so, there is still much scientists do not know about leatherbacks. We need a better understanding of where leatherbacks go, what they do out there, and especially what they need to survive. Until then, all scientists can do is preserve sea turtle nesting sights and make people aware of the existence of these endangered leatherbacks. If everyone pulls together to make a difference, things can change. Efforts like creating turtle nesting parks are underway in hopes to get people to notice that they are a serious matter. If people realize what is happening to these defenseless animals, they will do their part to.

Works Cited

1. Allen, Jodie T., et al. “The Environment - Great Vanishing Turtles.” U.S. News & World Report 12 June 2000: 10.

2. Gilbertas, Bernadette. “Up From the Sand.” International Wildlife September-October 1998: 30-36.

3. Kaufman, Kevin C. “Pacific Leatherback Turtles Face Extinction.” Business Wire 1 June 2000: 1109.

4. Knight, Danielle. “Environment: Pacific Leatherback Sea Turtles Near Obliteration.” Environment Bulletin 1 June 2000.

5. Monastersky, Richard. “Do Sea Turtles Stop and Ask For Directions?” Science News 30 November 1996: 342.

6. Penick, D.N. and James R. Spotila. “Blood Perfusion of Leatherback Sea Turtles.” American Zoologist November 1998: 125A.

7. Southwood, Mary L., et al. “Heart Rates and Diving Behavior of Leatherback Sea Turtles.” Journal of Experimental Biology May 1999: 1115-1121.

8. Spotila, James R. “Turtle’s Cold Water Survival Strategy.” Science News 26 September 1992: 206.

9. Tyson, Peter. “High-tech Help for Ancient Turtles.” MIT’s Technology Review November-December 1997: 54-57.


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