With sizes ranging up to 2 metres long, the Leatherback turtle Dermochelys coriacea, is the largest of any turtle, and one of the largest living reptiles in the world. They come from the family Dermochelyidae, which roots trace back over 100 millions years, and are said to be the last of the family.
As seen in fig. 1 the Dermochelys coriacea differs from other turtles due to the characteristics of their shell, flippers and mouth. Whereas most shells are a bony and hard shell, the Leatherback turtle has a more flexible shell, and feels rubbery due to the carapace. Their carapace is made from a leathery skin type material holding together dermal bones, the dermal bones also create the ridges of the shell and come together at a blunt point at the bottom of the shell. These ridges on the carapace allow the turtle to be more hydrodynamic. They do not have claws and scales on their front flippers, unlike the other 6 species of sea turtle, and are also much greater in length. The last distinctive characteristic is their mouth. They possess “pointed tooth-like cusps and sharp-edged jaws” as well as spines in the mouth and throat that point backwards, which allow them to consume their prey of jellyfish, salps and other invertebrate creatures in the open water.
The Leatherback turtle is also adapted to conserve, as well as generate heat, allowing them to survive in both temperate and tropical waters. Their global distribution is the widest of any reptile. This is because the species is known, due to tagged individuals, to travel thousands of miles in order to return to their birth place for breeding season, with the biggest nesting grounds being found in West Africa and Northern South America. They were found in every ocean, excluding the Arctic and Antarctica, however these numbers have heavily declined (over 90% in the last two decades), and the turtle, as well as the other 6 species, has now been classed as endangered and put under the U.S. Endangered Species Act. The global population decline is mainly due to fisheries, coastal development and egg harvesting. Temperature change has also had a small affect on the population. As they can create mass damage to trawler netting, when accidently caught up in the catch, they are often killed and sold on for meat and decoration within illegal trades in order for fisherman to afford the costs of either new netting, or for materials to repair their original net. In order to protect these turtles from extinction a joint conservation effort is needed between countries, especially in the U.S, due to the vast distances they travel when migrating. To stop the turtles being mistakenly caught by fisheries within the U.S, modifications to netting and equipment, and changing times and locations of fishing has been implemented by the NOAA, National Oceanic and Atmospheric Administration. This and many other organisations work individually to their area, as well as together, in order to enrich the life of both aquatic and non aquatic life, to create a sustainable environment. The use of TEDs, turtle excluder devices, which are placed within the fishing nets, have also lowered the death rates of the Leatherback. As well as working with fisheries to increase the population, conservation and protection organisations also work with communities that are close to nesting grounds and turtle habitats, discouraging poaching and providing new opportunities for their livelihood. Management plans is crucial in the protection of the Leatherback turtle.
Nesting occurs 2-3 times a year, like most turtles this occurs in the same area as each turtle was hatched, however the Leatherback turtle is different to other sea turtles as it is not always on the same beach. Nesting occurs during breeding season after mating at sea. Nests are produced in the sand where approximately 80 fertilised eggs and 30 unfertilised eggs are buried in a deep hole. The unfertilised eggs are placed on top of the fertilised ones to increase the likelihood of hatching, as they were less likely to be eaten by predators, and the temperature is optimum. Around the nest, the female turtle will disturb the sand in order to blend the nest in with the surrounding area, so predators are less likely to find the nest and hatchling survival rates increase. With all this protection put in place, it could be said that the number of hatchlings must be great, wrong, only 1/1000 are said to survive to adulthood, mainly due to the removal of eggs for human consumption. The gender of the hatchlings is not due to chromosomes, but due to the temperature of the nest. Around 29.5 degrees Celsius is the temperature that produces both genders. The higher the temperature, then gender becomes female, the lower the temperature, the hatchlings will be male.
National Geographic – http://animals.nationalgeographic.com/animals/reptiles/leatherback-sea-turtle/
NOAA Fisheries – http://www.nmfs.noaa.gov/pr/species/turtles/leatherback.htm
Wildlife Conservation Society – http://www.wcs.org/saving-wildlife/ocean-giants/leatherback-sea-turtle.aspx
Sea Turtle Conservancy – http://www.conserveturtles.org/seaturtleinformation.php?page=leatherback