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Dermochelys coriaceaLeatherback Sea Turtle

By Adam Farmer; Annamarie Roszko; Scott Flore; Kevin Hatton; Veronica Combos; Andrea Helton; Fermin Fontanes

Geographic Range

Leatherbacks are primarily pelagic animals. They travel great distances from their nesting beaches to their feeding grounds. Although leatherbacks are most often found in tropical waters, they are distributed around the globe in temperate oceans, and even on edges of subarctic water. The leatherback sea turtle travels further north than any other sea turtle. They live in Northern Atlantic waters as far north as Newfoundland, Nova Scotia, and Labrador. They also inhabit South Atlantic Waters, as far south as Argentina and South Africa. This turtle inhabits waters as far east as Britain and Norway.

During the nesting season they are discovered along the coasts of French Guiana, Suriname, Guyana, Trinidad, Gabon, West Africa, Parque Marino Las Baulas in Guanacaste, Costa Rica, Papua New Guinea, Andaman and Nicobar Islands, Thailand, in the U.S. on St. Croix, U.S. Virgin Islands, and in Puerto Rico and Florida. The largest nesting colony is in Africa, along the coast of French Guiana. More than 7,000 females laid as many as 50,000 eggs there in 1988 and again in 1992. There is one nesting record in Cape Lookout, North Carolina. (Eckert, 2006; Martof, et al., 1980; Spotila, 2004)

Habitat

Leatherback sea turtles live in many different oceans throughout the world. They are widely known as pelagic animals but are seen in coastal waters when searching for food. They live in tropical, temperate and even some subarctic oceans. They have been discovered in waters as deep as 1230 m, well below the photic zone.

Leatherbacks lay their eggs in the sand of tropical beaches. It is the only time they emerge onto land, and only the females do so. (Eckert, 2006; Spotila, 2004)

  • Range depth
    1230 (high) m
    4035.43 (high) ft

Physical Description

The leatherback sea turtle is the largest of living turtles. It may reach a length of ca. 2.13 m. Adults may have a span of ca. 2.7 m from the tip of one front flipper to the tip of the other. They have a secondary palate, formed by vomer and palatine bones. The leatherback has no visible shell. The shell is present but it consists of bones that are buried into its dark brown or black skin. It has seven pronounced ridges in its back and five on the underside. Leatherback hatchlings look mostly black when looking down on them, and their flippers are margined in white. Rows of white scales give hatchling leatherbacks the white striping that runs down the length of their backs.

These turtles feed in waters that are far colder than other sea turtles can tolerate. They have a network of blood vessels that work as a counter-current heat exchanger, a thick insulating layer of oils and fats in their skin, and are able to maintain body temperatures much higher than their surroundings. (Spotila, 2004)

  • Sexual Dimorphism
  • female larger
  • Range mass
    250 to 900 kg
    550.66 to 1982.38 lb
  • Range length
    145 to 160 cm
    57.09 to 62.99 in

Development

Hatching success of clutches is about 50% in an undisturbed nest. Many nests are destroyed by many different predators. Nest temperature determines the hatchlings' sex. At 29.5 degrees Celsius hatchlings are equally likely to be male or female, hatchlings incubated at 28.75°C or less will be male, above 29.75°C they'll be female. Hatchling turtles weigh 35-50 grams, and grow very fast. Leatherbacks may be the fastest growing reptile in the world, reaching adult size in 7 - 13 years. (Spotila, 2004)

  • Development - Life Cycle
  • temperature sex determination

Reproduction

The male leatherback turtles will migrate just offshore a common nesting beach generally before nesting season begins. There they will try and mate with as many females as possible. Also, studies have shown that the males will return to the same nesting beach if they were successful in the previous season. (Eckert, et al., 2005)

Leatherback sea turtles mate in the water, just offshore from the females' desired nesting beach. The female then swims ashore at night to nest and will produce a clutch of usually 50 - 170 eggs. However, a large percentage of those eggs are yolkless and will not develop further. The female will lay her eggs and then cover the nest with sand to discourage predation and moderate the temperature and humidity around the eggs. After the female has completed this process she will returns to the ocean. Male leatherback sea turtles never swim to shore and have no part in the nesting process. (Barbour and Ernst, 1972; Beacham, et al., 2000; Eckert, et al., 2005; Zug and Parham, 1996)

  • Breeding interval
    Leatherback Sea Turtles will lay about 5 to 7 nests per year, renesting every 9 to 10 days. Also, they will return to the same nesting location every 2 to 3 years.
  • Breeding season
    They generally reproduce between the months of April and November.
  • Range number of offspring
    50 to 70
  • Average number of offspring
    105
    AnAge
  • Range gestation period
    55 to 75 days
  • Average time to independence
    immediate (no parental investment past egg-laying) minutes
  • Range age at sexual or reproductive maturity (female)
    5 to 21 years

The only parental investment that occurs with leatherback sea turtles is when the female lays eggs on the shore and covers her nest after laying the eggs. No subsequent parental care occurs. (Barbour and Ernst, 1972)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • female

Lifespan/Longevity

We have no information on the lifespan of Dermochelys coriacea. (Barbour and Ernst, 1972; Pope, 1939)

  • Average lifespan
    Status: captivity
    30 years
    AnAge

Behavior

Leatherbacks are mostly solitary. They migrate great distances between nesting and feeding grounds. They seem to locate locations that have high concentrations of jellyfish, and feed near the surface or dive to find the highest concentrations of prey. (Alderton, 1988; Carr, 1952; Pope, 1939)

Food Habits

Leatherback turtles are carnivores that feed in the open ocean. Their main prey are gelatinous invertebrates, mainly jellyfish and salps. They are known to eat other kinds of food though, including small crustaceans and fish (possibly symbiotes with jellies), cephalopods, sea urchins, and snails.

Leatherbacks do not have the powerful muscles and hard crushing jaw apparatus that some other sea turtles have for eat hard-shelled prey. Instead they have sharp-edged jaws for biting soft-bodied prey. The esophagus in this species is lined with short spines that point downstream, preventing jellies from escaping once swallowed. (Caut, et al., 2006; Houghton, et al., 2006)

  • Primary Diet
  • carnivore
    • eats other marine invertebrates
  • Animal Foods
  • fish
  • mollusks
  • aquatic or marine worms
  • aquatic crustaceans
  • echinoderms
  • cnidarians
  • zooplankton

Predation

In modern times, humans have become the primary predator of this species, gathering eggs and killing adults.

Leatherback turtles eggs are consumed by a large variety of predators, including ghost crabs (Ocypode), monitor lizards (Varanus), wading birds such as turnstones (Arenaria), knots (Calidris), and plovers Pluvialis). Many mammals excavate nests as well, including raccoons (Procyon lotor) and coatis (Nasua), dogs (Canis), genets (Genetta), mongooses (Herpestidae) and pigs (Suidae). Most of these same predators will take hatchlings as the little turtles race for the sea, as will raptors (Falconiformes), gulls (Larus), and frigate birds (Fregatidae). In the ocean, small leatherbacks are attacked by cephalopods, requiem sharks (Carcharhinidae) and other large fish. Adult leatherbacks are large and powerful enough to have few predators, but jaguars (Panthera onca) and other large predators may attack nesting females, and killer whales (Orcinus orca) and large sharks may attack them at sea.

Nesting females pack the sand over their clutch of eggs, perhaps to obscure the scent of the eggs and make them harder for small predators to dig up. Hatchlings wait until nightfall to emerge and head for the water, to avoid predators. Throughout their lives leatherbacks are counter-shaded, dark on the dorsal surface and light underneath, to better blend with background light (though the dark dorsal surface is probably also better for basking).

Although they don't have the bony shell of most turtles, they do have a thick layer of connective tissue over bony plates covering much most of their body. Leatherbacks are strong and fast swimmers, and adults may defend themselves aggressively. One adult (c. 1.5 m long) was seen chasing a shark that had apparently attacked it, and once the shark fled, the turtle attacked the boat that the observers were in. (Caut, et al., 2006; Chiang, 2003; Ernst, et al., 1994)

Ecosystem Roles

Leatherback sea turtles are predators that eat mainly jellyfish and other soft-bodied marine animals. Their affect on prey population densities is unknown, but might have been substantial before their populations were reduced by harvesting.

Leatherback eggs and hatchlings may be a significant food source for egg predator populations near their nesting beaches.

Leatherbacks are the host of Conchoderma virgatum, a commensal species of barnacle. (Eckert and Eckert, 1987; Ernst, et al., 1994; Spotila, 2004)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Although the flesh of adult leatherbacks can sometimes be toxic, adults and eggs are used for food in some locations, and in a few places the oil from the bodies of adults is extracted for medicinal use and as a waterproofing agent.

Leatherbacks eat jellyfish that are pests for swimmers and fishermen, especially for marine fish-farming. Consumption estimates vary, one study estimated that adult leatherbacks probably eat about 1000 kg of jellyfish per year, an earlier study estimated 2900-3650 kg/yr. (Spotila, 2004; Ernst, et al., 1994; Spotila, 2004; United States Fish and Wildlife Service, 2007)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

This species does not harm humans or cause significant costs. It's flesh is sometimes toxic to humans and other animals, perhaps due to toxins ingested as part of its diet of jellyfish.

Conservation Status

This species is believed to be in serious decline. Populations of nesting females in the Pacific have declined as much as 70-80% in the last decade, and the status of the Atlantic population is unclear. Because females may nest on more than one beach each year, accurate counts are more difficult than for some other turtle species. The species is rated "Critically Endangered" by the IUCN, and "Endangered" by the U.S. Fish & Wildlife Service. It has been listed in Appendix I of the CITES, making any international trade illegal.

The primary threat to the species is commercial fishing: turtles accidentally trapped and drowned in nets and trawls, or hooked or tangled by longlines and trap lines. Harvesting of eggs is a significant problem as well. Also, leatherbacks apparently sometimes eat plastic debris they find in the water, probably mistaking it for jellyfish. This plastic debris is indigestible, and an increasing number of turtles are found dead with blocked digestive tracts.

Nature reserves have been established in the coastal areas where the turtles come to breed to prevent people from stealing the eggs. In some areas, scientists have taken the eggs into captive breeding programs to try to increase the population of the area. Some governments require use of turtle-exclusion devices on fishing gear, but this is not a widespread practice. (Ernst, et al., 1994; National Oceanic and Atmospheric Administration, Office of Protected Resources, April 13, 2001)

In July of 2004, the “Marine Turtle Conservation Act” was signed into law in the United States. The purpose of this bill was to aid in the conservation of marine turtles, as well as to assist foreign countries in preserving their nesting habitats. To support this bill there are hopes of creating a “Multinational Species Conservation Fund” to support conservation of imperiled marine turtles, including the leatherback. (Evans, 2004)

Contributors

Adam Farmer (author), Radford University, Annamarie Roszko (author), Radford University, Scott Flore (author), Radford University, Kevin Hatton (author), Radford University, Veronica Combos (author), Radford University, Andrea Helton (author), Radford University, Karen Powers (editor, instructor), Radford University.

Fermin Fontanes (author), University of Michigan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

coastal

the nearshore aquatic habitats near a coast, or shoreline.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

poisonous

an animal which has a substance capable of killing, injuring, or impairing other animals through its chemical action (for example, the skin of poison dart frogs).

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

semelparous

offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

Bronsgerma, L.D. Guide for the identification of standard turtles of British Coasts. London, British Museum of Natural History.1976.

Bustard, H. Roberts. Sea Turtles and the Turtle Industry of the West Indies, Florida and the Gulf of Mexico. Coral Gables. Fla., University of Miami Press (1974).

Chang, Eng Heng. The Leatherback Sea Turtle:a Maylasian Heritage. Kuala Lumpur, Malaysia: Tropical Press Sdn. Bhd.,1989.

Hartog, J.C. den. A study on the gut content of six leathery turtles Dermochelys coricacea:(Linneaus)(Reptilia:Testudines:Dermochelydae) from British waters and from the Netherlands. Leiden: Rijiksmuscum van Natururlijke Historie. 1984

Recovery Plan for the St. Croix population of Leatherback turtle. Washington D.C.: United States Fish and Wildlife Service. 1981.

Encyclopaedia Britannica, Inc. Peter B. Norton, Joseph J Esposito. Chicago. Vol.10, Vol. 11, Vol. 25, Vol. 26. 1986.

Alderton, D. 1988. Turtles & Tortoises of the World. New York, NY: Facts on File, Inc..

Barbour, R., C. Ernst. 1972. Turtles of the United States. Lexington, Kentucky: University Press of Kentucky.

Beacham, W., F. Castronova, S. Sessine. 2000. Beacham's Guide to the Endangered Species of North America, volume 1: Mammals, Birds, Reptiles. Detroit: Gale Virtual Reference Library. Accessed August 22, 2007 at http://www.gale.com/eBooks.

Carr, A. 1952. Handbook of Turtles. Ithaca, NY: Comstock Publishing Associates.

Caut, S., E. Guirlet, P. Jouquet, M. Girondot. 2006. Influence of nest location and yolkless eggs on the hatching success of leatherback turtle clutches in French Guiana.. Canadian Journal of Zoology, 84(6): 908-916.

Chiang, M. 2003. The plight of the turtle. Science World, 59: 8.

Committee on Sea Turtle Conservation, National Research Council, 1990. Decline of the sea turtles. National Academy Press.

Eckert, K., S. Eckert. 1987. Growth Rate and Reproductive Condition of the Barnacle Conchoderma virgatum. Journal of Crustacean Biology, Vol. 7/No. 4.: 682-690.

Eckert, S. 2006. High-use oceanic areas for Atlantic leatherback sea turtles (Dermochelys coriacea) as identified using satellite telemetered location and dive information. Marine Biology, 149/5: 1257-1267. Accessed August 22, 2007 at www.springer.com/journal/227.

Eckert, S., M. James, R. Myers. 2005. Migratory and reproductive movements of male leatherback turtles. Marine Biology, 147(4): 845.

Ernst, C., J. Lovich, R. Barbour. 1994. Turtles of the United States and Canada. Washington, D.C., USA: Smithonian Institution Press.

Evans, D. 2004. Raising awareness of sea turtle habitat. Endangered Species Bulletin, 29(2): 30-31.

Georgia Museum of Natural History, 2000. "Georgia Wildlife Web -- Leatherback, Dermochelys coriacea" (On-line). Accessed 11/26/07 at http://dromus.nhm.uga.edu/~GMNH/gawildlife/index.php?page=speciespages/species_page&key=dcoriacea.

Houghton, J., T. Doyle, M. Wilson, J. Davenport, G. Hays. 2006. Jellyfish aggregations and leatherback turtle foraging patterns in a temperate coastal environment. Ecology, 87/8: 1967-1972.

Martof, B., W. Palmer, J. Bailey, J. Harrison III. 1980. Amphibians and Reptiles of the Carolinas and Virginia. Chapel Hill: The University of North Carolina Press.

National Oceanic and Atmospheric Administration, Office of Protected Resources, April 13, 2001. "Leatherback Sea Turtle (Dermochelys coriacea)" (On-line). Accessed January 20, 2003 at http://www.nmfs.noaa.gov/prot_res/species/turtles/leatherback.html.

Pope, C. 1939. Turtles of the United States and Canada. Canada: The Ryerson Press.

Spotila, J. 2004. Seaturtles. Baltimore and London: The John's Hopkins University Press.

United States Fish and Wildlife Service, 2007. "Leatherback Sea Turtle" (On-line). Accessed 11/26/07 at http://ecos.fws.gov/speciesProfile/SpeciesReport.do?spcode=C00F.

Zug, G., J. Parham. 1996. Age and Growth in Leatherback Turtles, Dermochelys coriacea (Testudines: Dermochelyidae): A Skeletochronological Analysis. Chelion Conservation and Biology: Journal of the IUCN/SSC Tortoise and Freshwater Turtle Specialist Group and international bulletin of chelonian research, 2: 244-249.

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