Final Paper: The Magnificent Leatherback Turtle

This discussion topic submitted by Astrid Senturia ( senturaf@miamioh.edu) at 9:13 am on 5/19/00. Additions were last made on Wednesday, May 7, 2014.

The leatherback sea turtle, Dermochelys coriacea, has been on the endangered species list since the early 1970's. Like all other sea turtles, the leatherback is a reptile that breaths air and is cold-blooded. This phenomenal creature spends the majority of its lifetime in the open ocean. The only exceptions are for mating and breeding purposes, which brings the turtles either to shore or into shallow bays. Costa Rica is a reputable area of the world for leatherback turtle sitings and for nesting on its tropical beaches. This report will take a closer look at leatherback sea turtles, their habitat, and how they fit into the worlds' ecosystem, paying particular attention to Costa Rica.
I. Biology
Leatherback sea turtles are the largest turtles in the world. The average life expectancy of a leatherback turtle is thirty years. One identifying characteristic of these reptiles is that the majority of their body is black. In particular, adult leatherbacks have scaleless black skin while the underside is speckled pinkish-white and black. The neck is short and non-retractable, as sea turtles can not bring their head inside their shell. This turtle has sort of a barrelshaped figure. The average size of the turtles upper shell, carapace, is about 5 feet and has a rubber-like texture feel to it consisting mainly of oil-saturated connective tissue. On average leatherback sea turtles can weigh approximately 800 lbs. although many weigh more as well as less. The front flippers, which lack claws, span on average 9 feet. The lack of claws is another distinguishing characteristic that sets them apart from all other turtles. The hind flippers are broad and connected to the tail by folds of skin. These turtles have the capacity to eat the equivalent of their body weight in jellyfish on a daily basis. Sometimes minnows and small planktonic creatures such as sea squirts will have to make up the difference but nothing larger because leatherback turtles do not have teeth, so it is up to their jaws to do all of the work. Interestingly, leatherback turtles are poisonous if eaten. Humans as well as animals tend to have severe adverse reactions detrimental to one's health.
II. Distribution
The distribution of these sea turtles is unusual compared to other marine turtles. Leatherback sea turtles are no longer concentrated mainly in tropical waters, but can be spotted all over the world. The turtles ability to remain under water for several hours while resting, and only surfacing to breathe frequently when active, allows the turtles to venture far off of the coastline and diving to depths of more than 3,000 feet. Leatherback turtles have been found as far north as off of the coast of Norway; even in close proximity to the Arctic Circle and as far south as the waters of New Zealand. Due to their size and weight, their bodies can handle cold water temperatures, allowing them to venture away from tropical waters. This makes it difficult to tag and keep track of sea turtles, because of their free roaming nature. Due to their behavior the migration patterns of leatherback sea turtles remain a mystery to scientists. Due to the frequent migration and traveling nature of these turtles it is hard to accurately account for all living and reproducing leatherback turtles. Currently, scientists estimate that there are approximately 20,000-30,000 female leatherbacks alive in the world today (while other sources dispute this fact by claiming that there are at least 100,000 female leatherbacks accountable).
III.Reproduction
Mating takes place in offshore shallow bays, shortly before females come ashore onto the nesting beaches. Developing into a mature adult can take anywhere from five to fifteen years. After reaching sexual maturity around the age of ten, female leatherbacks nest every two to four years, approximately seven nesting times in each nesting season are feasible. Unfortunately the leatherbacks found in Costa Rica are only nesting on average 1.15 times each season. Nesting season begins in the late part of the wet season so that when the babies emerge the rainy season is over and the sand is dry. In the Northern Hemisphere specifically, nesting begins in October and continues through March. The nesting season in the Southern Hemisphere is typically from March to July. The start of the nesting season is directly correlated with the latter end of the rainy season so that the sand is dry and not an obstacle for hatchlings. The female leatherback comes ashore during the night, digs a nest in the sand and proceeds to lay a large quantity of eggs, a clutch. The first layer consisting of 60-84 eggs are considered to be fertilized--whole. The layer of eggs on top of the whole eggs is composed of smaller and yolkless eggs. There are about 30 eggs making up this layer. This is a natural defense mechanism against predators and poachers. The female then covers her nest and after only about two hours of work, returns to the sea. After sixty days of incubation the eggs are ready for hatching. Hatchlings are dorsally mostly black and are covered with tiny scales; the flippers are margined in white, and rows of white scales appear as stripes along the length of the back. Hatchlings average 2-2 1/2 inches long and 45.8 g in weight. As a group the hatchlings dig their way out of the sand and return to the water.
IV. Impacts on Leatherbacks
The threats that leatherbacks face grow daily. Whether by natural environmental causes or humans' intervention the leatherback sea turtle population on a global scale is on the decline. Everyday large amounts of sea turtles die as their lives are constantly threatened. Leatherbacks are seriously declining at all major nesting beaches throughout the Pacific. The decline is dramatic along the pacific coasts of Mexico and Costa Rica and coastal Malaysia. Despite the fact that they are an endangered species, these reptiles are still constantly at risk. Populations in certain areas of the world are declining due to invasion of beaches by humans. Which also contributes to poachers harvesting eggs. There is a recovery program for leatherback sea turtles taking place in the United States. The U.S. has a small nesting population of the southern coast of Florida. These populations however are frequently in danger of fisheries, marine pollution and growth in the human population in these areas. The marine turtle population all over the world is still presently in danger.
Leatherback sea turtles are protected by the U.S. Endangered Species Act and also appears on the list composed by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Most countries in which nesting occurs protect these sea turtles by law, but enforcing the law is another matter.
Some leatherbacks are killed for their oil or meat, which has been a more recent development. A common cause of death of leatherback sea turtles is the accidental entanglement of their bodies is shrimp fishing nets. It has become such a big problem that the EPA has mandated that TED's (Turtle Exclusion Device) be implemented in hopes of rescuing these endangered species. The effectiveness of these devices is still debatable. Adult leatherback sea turtles are most of the time too large to fit through the opening provided for them in the TEDís. Although TED's are required many fishermen refuse to use them and sometimes enforcing this policy is difficult. The National Marine Fisheries Service have taken charge of attempting to regulate the use of TED's and blocking fishermen access to waters highly populated with leatherbacks unless they implement the use of TED's. This is a very active way to help rejuvenate the leatherback population by cutting back on preventable accidental deaths.
Nesting females prefer open isolated beaches. This is becoming increasingly difficult with the world's growing population and development of once pristine areas. Heavy use of beaches, driving vehicles and heavy machinery over the sand can cause problems for hatchlings by compacting the sand and making it nearly impossible to crawl through the sand, out of the nest. It is also possible that these actions can even penetrate the nest. However the open beaches are prone to erosion which leads to the destruction of nests and loss of eggs. Hurricanes are a type of natural disasters that are detrimental to leatherback sea turtle nests. Temperature, which may effect embryo development, is yet another factor that effects nests. Discarding objects and debris on the beach can be detrimental to nests by covering the nest and ultimately effecting the temperature of the eggs.
Leatherback turtles eat a wide variety of marine debris such as plastic bags, plastic and styrofoam pieces, and balloons that are mistaken for jellyfish. Effects of consumption include interference in metabolism or gut function. While at sea, leatherbacks are victims of boat collisions. It doesnít matter if the sea turtles are on land or in the open waters, humans constantly pose a threat towards this species.
The magnificent leatherback sea turtle is a precious species that exists in the world today. It has endured and evolved through the years, and it would be terrible if humans put an end to their amazing existence. By learning more and taking an active role in supporting conservation programs, hopefully the leatherback population can grow and flourish.


Bibliography
Alderton, David. Turtles & Tortoises of the World. Facts on File, Inc., New York, NY
1988.
Lamar, William K. The World's Most Spectacular Reptiles & Amphibians. Tampa,
Florida, World Publications: 1997.
http://www.coas.drexel.edu/environ/leatherback/lb_mortality.html
http://www.ednet.ns.ca/educ/museum/mnh/nature/turtles/index.htm
http://leahi.kcc.hawaii.edu/~et/wlcurric/turtles.html
http://www.nmfs.gov/prot_res/turtles/turtle.html
http://www.nmfs.gov/prot_res/turtles/leathtur.html
http://www.turtles.org/leatherd.htm



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