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Overview

Brief Summary

Description

The leatherback is the world's largest turtle; the largest recorded individual weighed a massive 916 kilograms (5). This turtle earned its common name because it lacks the typical bony plates on its carapace. Instead, its shell is flexible and covered in a thin layer of leathery skin. This turtle is dark in colour with white and pink spots. Leatherbacks are easily recognisable by the seven narrow ridges running the length of the carapace, and by their particularly large front flippers. Females also have a characteristic 'pink spot' on the top of their heads (6).
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Biology

Adult leatherbacks feed mainly on jellyfish and other soft-bodied species (9). They are exceptional amongst reptiles because they are partly able to maintain an elevated body temperature via thermal inertia and a specially organized blood supply system in their shoulders (10). These features allow leatherback turtles to travel to cold waters and to dive to depths greater than 1,000 meters in search of prey (11). To nest, females emerge at night on nesting beaches to lay their eggs. Using their rear flippers they excavate deep 'boot shaped' nests into which roughly 100 eggs are laid. Around 20 percent of the eggs in each nest are small and yolkless (2). Individuals return to nest every few years, but within one season a female can lay four to ten clutches of eggs (2). The sex of the hatchlings is influenced by incubation temperatures: hotter nests produce all females; cooler nests produce all males (12).
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Most sea turtle species live in warm water. You don't find abundantly numbers in the North Sea. However every once in awhile, a weakened animal is carried by the currents. Sometimes the Gulf Stream leads it into the North Sea. Green turtles in particular are the most common turtle species to wash ashore along the North Sea coast. These turtles are shipped across the world for human consumption. Leatherbacks live where jellyfish, the major part of their diet, are plentiful. That's why they occasionally swim in colder seas, such as the North Sea.
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Taxonomy

Dermochelys coriacea is the only living member of the Dermochelyidae family, sister taxon to the family Cheloniidae, which contains all other extant sea turtles (6 species in 5 genera).Dermochelyidae is distinguished by the lack of a hard, rigid carapace (shell) comprised of keratinous scutes - a feature that all other sea turtles share. Instead it has a carapace formed of flexible tissue, overlain by a matrix of small (1–2cm) bones called osteoderms and covered in a layer of skin.It possesses 7 lateral ridges running the length of the carapace, although other extinct Dermochelyidae species have been characterised by the possession of different numbers of such ridges.Its skeleton has a high cartilage ratio making it highly flexible and it has particularly long front flippers.
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Introduction

The leatherback sea turtle, Dermochelys coriacea, was first described by Vandelli in 1761. It is the only living member of the Dermochelyidae family and weighs 300–600kg. It rivals the saltwater crocodile as the world’s largest living reptile. Listed as critically endangered (International Union for Conservation of Nature 1990), along with many other sea turtles it faces threats from:
  • entanglement in fishing gear
  • over-harvesting of eggs
  • hunters who kill adults for meat and shells
The leatherback is found throughout the world’s oceans feeding on jellyfish and salps. It is also the deepest diver amongst the reptiles, reaching depths of 1,230m.It nests on beaches in the tropics where it lays 50–70 viable eggs.
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Comprehensive Description

Brief

"Largest and heaviest living reptile """" """"916 kg), Elongated shell tapered towards the posterior. Carapace bear 7 ridges , 5 on the plastron."
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Description

A distinctive, unique species; the largest of all marine turtles, reaching 1,800 mm in carapace length, 2,770 mm between forelimb tips. Carapace and plastron leathery, without horny plates;carapace depressed, elongate, with 7 longitudinal ridges, posterior edge smooth, ending with a narrow, pointed extensioover the tail. Plastron with 5 longitudinal ridges. Head relatively small; upper jaw with two tooth-like projections. Front limbs very long, with no claws. Not much difference in size between sexes, but males have longer tails. Color of carapace and dorsal sides of limbs and head blackish or bluish black with irregular whitish spots. Ventral sides pinkish white with some dark spots.

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Biology

Like other sea turtles, female Dermochelys coriacea, nest by hauling themselves onto tropical beaches at night and digging nest chambers.The leatherback may lay and cover somewhere between 50 and 70 eggs in the nest chamber, followed by a further 20–40 infertile and misshapen eggs or vanos (from the Spanish for ‘empty’ or ‘wasted’).It can nest 6 to 10 times a year during a nesting season of several months, which varies depending on the location.Approximately 10 days pass between each arrival, when further mating occurs. The female provides no parental care and young turtles hatch within 60–80 days. It can take further 5 days for them to emerge onto the beach to face a range of predators as they return to the sea.Leatherback nests have particularly low hatchling success - 50–60 percent is normal.The sex of the offspring is determined by the temperature within the chamber - high temperatures produce females and low temperatures males. The pivotal temperature is about 29.5°C during a critical sex-determining period.Little is known about the whereabouts of juvenile Dermochelys coriacea and it's unclear exactly how long it takes for the turtle to mature, or the what the average life-span is.
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Description

 The leatherback is the world's largest sea turtle, it has a carapace (shell) up to 2 m in length and can weigh a total of 0.5 tonnes. Characteristic features are a blackish leathery shell with 7 longitudinal ridges along the back, three of which are clearly visible when the animal is swimming at the surface. The skin is also black and relatively smooth with pale spotting. The leatherback is warm-blooded (endothermic), maintaining a body temperature of around 25 °C, which is unusual as most reptiles are cold-blooded (ectotherms).The leatherback is the sole living representative of the family Dermochelyidae. It is clear that the leatherbacks extensive migrations to British waters are to follow swarms of jellyfish which are the leatherbacks main prey item. Breeding occurs in shallow tropical waters, although female leatherbacks will come high up on the shore to deposit their eggs. Populations of leatherbacks are in serious decline due to a number of factors. These include loss of nesting habitats, destruction of nests by poachers, propeller wounds, interaction with commercial fisheries and ingestion of marine debris. 

Dermochelys coriacea is listed as Critically endangered on the Red list of Threatened animals 2000 and, therefore, considered to be of extremely high risk of extinction in the wild in the immediate future. It is listed under the UK Biodiversity Action Plan and is addressed under a marine turtles Species Action Plan. Dermochelys coriacia is listed on Appendix I of the Convention on the International Trade in Endangered Species of Flora and Fauna (CITES) 1975, Appendix II of the Bern Convention 1979, Appendices I and II of the Bonn Convention 1979 and Annex IV of the EC Habitats Directive. The loggerhead is also listed as a priority species on Annex II of the EC Habitats Directive. All five species are protected under Schedule 5 of the Wildlife and Countryside Act 1981 and the Conservation (Natural Habitats & c.) Regulations 1994 (Anon, 1999(ii)).

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Distribution

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.

Biogeographic Regions: oceanic islands (Native ); indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

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

Found throughout the world's oceans with the widest distribution of all the turtles, the leatherback has been recorded as far north as Alaska and as far south as the tip of South Africa (1). These turtles often undertake long-distance migrations, between feeding grounds in temperate waters and nesting beaches in the tropics, sometimes surpassing 7,000 kilometres over several months (7).
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occurs (regularly, as a native taxon) in multiple nations

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National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

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Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) This circumglobal species generally forages in temperate waters and nests in tropical and subtropical latitudes on beaches of the Atlantic, Indian, and Pacific Oceans. Leatherbacks appear to spend the first portion of their lives entirely in tropical waters; those less than 100 cm in carapace length occur only in waters warmer than 26°C, whereas adults may venture to high latitude waters in summer (e.g., see Goff and Lien 1988, Eckert 2002) and occur occasionally in inshore waters.

Significant nesting areas include Malaysia (at least formerly), Pacific coast of Mexico and Central America, and Atlantic shore of northern South America. Largest population worldwide is in the western Atlantic (Spotila et al. 1996). In the Western Hemisphere, nesting also occurs in Florida (very rarely north to Georgia), along the shores of the Gulf of Mexico, in the West Indies, and along the Atlantic shore of Central America and the Pacific shore of northern South America. In the western Caribbean, nesting is frequent from northern Costa Rica to Colombia and in eastern French Guiana and western Surinam. Some nesting occurs along the central Brazilian coast; important colonies are in northwestern Guyana and in Trinidad. In the Antilles, most nesting occurs in the Dominican Republic and on islands close to Puerto Rico, including Culebra and St. Croix (the largest, best-studied population in U.S. waters).

A general aggregation of leatherbacks is known to occur in the Pacific north of the Hawaiian Islands year-round, and in the Atlantic seasonal concentrations occur during the summer and fall months in the northeastern United States and Canada in areas such as Cape Cod Bay, the Gulf of Maine, the Scotian Shelf, and Cape Breton.

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Found in all oceans except the Antarctic, is a regular summer visitor to waters around Cape Cod, the Gulf of Maine, and Nova Scotia.
  • North-West Atlantic Ocean species (NWARMS)
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cosmopolitan warm water
  • UNESCO-IOC Register of Marine Organisms
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Range Description

Leatherbacks are distributed circumglobally, with nesting sites on tropical sandy beaches and foraging ranges that extend into temperate and sub-polar latitudes (see Figure 1 in attached PDF and global distribution map). See Eckert et al. (2012) for review of Leatherback geographic range.

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Widely distributed.
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Distribution in Egypt

Essentially a vagrant to Egyptian waters, not known to breed in or near Egypt. It has been recorded several times from Egyptian territory in both the Mediterranean and Red Sea. From the Mediterranean Flower (1933) reports a large individual from the Alexandria market, but was not sure of its capture locality. Baha El Din (1992) reports 3 dead animals found on the shore at Zaranik and El Arish. Clarke et al. (2000) reports a further dead individual found on the beach at Rafah in 1998. In the Red Sea Werner (1973) reports the species from Nuweiba and south of Abu Rudeis. Frazier and Salas (1984) report 2 old specimens found in the vicinity of Hurghada, which were in the Hurghada Marine Biological Station in the early 1980s.

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Global Distribution

Circum-global, more readily entering colder waters than any other marine turtle. Although this species largely nests within the trop¬ics, it ranges widely into subtropical and temperate waters, even reaching the Arctic Circle.

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Continent: Africa Oceania Near-East Middle-America Asia Caribbean South-America North-America Australia Europe
Distribution: Atlantic, Pacific, and Indian oceans,   Andaman Islands, Nicobar Islands  America: from British Columbia to Chile, Alaska, and south to Argentina, Chile, and the Cape of Good Hope; SE Mexico (incl. Baja California), Belize, Guatemala, Nicaragua, Costa Rica, Panama [Villa et al.], Colombia [Castro,F. (pers. comm.)], Galapagos Islands  Africa: West and East coast of Africa (Eritrea, Principé and São Tomé in the Gulf of Guinea, Gabon, etc.), United Arab Emirates (UAE), Somalia, Mauritania, Cameroon, Madagascar, Gambia  Asia: Japan, Bangladesh, Sri Lanka, Pakistan, Korea  Europe: Labrador, Iceland, the British Isles, Norway,Mediterranean Sea, Italy, Turkey, France, Portugal  Australia (New South Wales, North Territory, Queensland, Tasmania, West Australia)  according to the 1994 IUCN Red List of Threatened Animals: EC/WC/NE/NW/SE/SW Atlantic Ocean, E/W Indian Ocean, Mediterranean and Black Sea, EC/NE/NW/SE/SW/WC Pacific Ocean,  Angola, Anguilla, Antigua and Barbuda, Australia, Brazil, Colombia, Costa Rica, Cote d'Ivoire, Cuba, Dominica, Dominican Republic, Ecuador, El Salvador, Fiji, French Guiana, Ghana, Grenada, Guadeloupe, Guatemala, Guyana, Honduras, India, Indonesia, Israel, Liberia, Malaysia, Martinique, Mexico, Montserrat, Mozambique, Myanmar (= Burma), Netherlands Antilles, Nicaragua, Panama, Papua New Guinea, Peru, Puerto Rico, Senegal, Solomon Islands, South Africa, Sri Lanka, St Kitts and Nevis, St Lucia, St Vincent, Suriname, Thailand, Togo, Trinidad and Tobago, USA (Washington, Western Atlantic: Maine, New Hampshire, Massachusetts,  Connecticut, New Jersey, Delaware, Maryland, Virginia, North Carolina, South Carolina, Georgia, Florida, Alabama, Mississippi, Louisiana, Texas), Venezuela, Virgin Islands (British), Virgin Islands (US), Zaire  13 finds in waters of Russia are known: in the Sea of Japan's Peter the Great Bay and the Rynda Bay, S Kuril Islands (Sea of Okhotsk) and Barents Sea (fide KHALIKOV, pers. comm.).  
Type locality: "Mari mediterraneo, Adriatico varius" (=Mediterranean and Adriatic seas); restricted to Palermo, Italy by SMITH & TAYLOR 1950.
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Historic Range:
Tropical, temperate, and subpolar seas

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Ranges farther into cold temperate waters than other marine turtles. Atlantic, Pacific, and Indian Oceans. North as far as Iceland and Labrador, south to Australia and the Cape of Good Hope.
  • Lutz and Musick, 1997; Ernst and Barbour, 1989.
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Physical Description

Morphology

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.

Range mass: 250 to 900 kg.

Range length: 145 to 160 cm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: female larger

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Size

Length: 178 cm

Weight: 544000 grams

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The largest living turtle, growing to 244 cm carapace length.
  • Lutz and Musick, 1997; Ernst and Barbour, 1989.
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Diagnostic Description

No other sea turtle lacks scutes on the shell or has prominent dorsal longitudinal ridges.

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Ecology

Habitat

Marismas Nacionales-San Blas Mangroves Habitat

This taxon is found in the Marismas Nacionales-San Blas mangroves ecoregion contains the most extensive block of mangrove ecosystem along the Pacific coastal zone of Mexico, comprising around 2000 square kilometres. Mangroves in Nayarit are among the most productive systems of northwest Mexico. These mangroves and their associated wetlands also serve as one of the most important winter habitat for birds in the Pacific coastal zone, by serving about eighty percent of the Pacific migratory shore bird populations.

Although the mangroves grow on flat terrain, the seven rivers that feed the mangroves descend from mountains, which belong to the physiographic province of the Sierra Madre Occidental. The climate varies from temperate-dry to sub-humid in the summer, when the region receives most of its rainfall (more than 1000 millimetres /year).

Red Mangrove (Rhizophora mangle), Black Mangrove (Avicennia germinans), Buttonwood (Conocarpus erectus) and White Mangrove trees (Laguncularia racemosa) occur in this ecoregion. In the northern part of the ecoregion near Teacapán the Black Mangrove tree is dominant; however, in the southern part nearer Agua Brava, White Mangrove dominates. Herbaceous vegetation is rare, but other species that can be found in association with mangrove trees are: Ciruelillo (Phyllanthus elsiae), Guiana-chestnut (Pachira aquatica), and Pond Apple (Annona glabra).

There are are a number of reptiles present, which including a important population of Morelet's Crocodile (Crocodylus moreletii) and American Crocodile (Crocodylus acutus) in the freshwater marshes associated with tropical Cohune Palm (Attalea cohune) forest. Also present in this ecoregion are reptiles such as the Green Iguana (Iguana iguana), Mexican Beaded Lizard (Heloderma horridum) and Yellow Bellied Slider (Trachemys scripta). Four species of endangered sea turtle use the coast of Nayarit for nesting sites including Leatherback Turtle (Dermochelys coriacea), Olive Ridley Turtle (Lepidochelys olivacea), Hawksbill Turtle (Eretmochelys imbricata) and Green Turtle (Chelonia mydas).

A number of mammals are found in the ecoregion, including the Puma (Puma concolor), Ocelot (Leopardus pardalis), Jaguar (Panthera onca), Southern Pygmy Mouse (Baiomys musculus), Saussure's Shrew (Sorex saussurei). In addition many bat taxa are found in the ecoregion, including fruit eating species such as the Pygmy Fruit-eating Bat (Artibeus phaeotis); Aztec Fruit-eating Bat (Artibeus aztecus) and Toltec Fruit-eating Bat (Artibeus toltecus); there are also bat representatives from the genus myotis, such as the Long-legged Myotis (Myotis volans) and the Cinnamon Myotis (M. fortidens).

There are more than 252 species of birds, 40 percent of which are migratory, including 12 migratory ducks and approximately 36 endemic birds, including the Bumblebee Hummingbird, (Atthis heloisa) and the Mexican Woodnymph (Thalurania ridgwayi). Bojórquez considers the mangroves of Nayarit and Sinaloa among the areas of highest concentration of migratory birds. This ecoregion also serves as wintering habitat and as refuge from surrounding habitats during harsh climatic conditions for many species, especially birds; this sheltering effect further elevates the conservation value of this habitat.

Some of the many representative avifauna are Black-bellied Whistling Duck (Dendrocygna autumnalis), Great Blue Heron (Ardea herodias), Roseate Spoonbill (Ajaia ajaja), Snowy Egret (Egretta thula), sanderling (Calidris alba), American Kestrel (Falco sparverius), Blue-winged Teal (Anas discors), Mexican Jacana (Jacana spinosa), Elegant Trogan (Trogan elegans), Summer Tanager (Piranga rubra), White-tailed Hawk (Buteo albicaudatus), Merlin (Falco columbarius), Plain-capped Starthroat (Heliomaster constantii), Painted Bunting (Passerina ciris) and Wood Stork (Mycteria americana).

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Panamanian Dry Forests Habitat

This taxon is found in the Panamanian dry forests, but not necessarily limited to this ecoregion. The Panamanian dry forests ecoregion occupies approximately 2000 square miles of coastal and near-coastal areas on the Pacific versant of Panama, around portions of the Gulf of Panama. Plant endemism is intermediate, and vertebrate species richness is quite high in the Panamanian dry forests.This key ecoregion is highly threatened from its extensive ongoing exploitation. Beyond the endemism and species richness, the ecoregion is further significant, since it offers a biological corridor from the moist forests to the coastal mangroves.

Plant endemism is intermediate in value within the Panamanian dry forests, likely elevated due to the (a) isolation of this ecoregion from the surrounding and intervening moist forest habitat; (b) arid conditions which likely enhanced speciation and hence species richness; and (c) absence of prehistoric glaciation, which has extinguished many species in more extreme latitudes.

Many of the plants are well adapted to herbivory defense through such morphologies as spiny exteriors and other features. Forest canopies are typically less than twenty meters, with a few of the highest species exceeding that benchmark. Caesalpinia coriaria is a dominant tree in the Azuero Peninsula portion of the dry forests, while Lozania pittieri is a dominant tree in the forests near Panama City. The vegetative palette is well adapted to the dry season, where water is a precious commodity.

Faunal species richness is high in the Panamanian dry forests, as in much of Mesoamerica, with a total of 519 recorded vertebrates alone within the Panamanian dry forests. Special status reptiles in the Panamanian dry forests include the American  Crocodile (Crocodylus acutus), the Lower Risk/Near Threatened Brown Wood Turtle (Rhinoclemmys annulata), the Lower Risk/Near Threatened Common Caiman (Caiman crocodilus), the Lower Risk/Near Threatened Common Slider (Trachemys scripta), and the Critically Endangered Leatherback Turtle (Dermochelys coriacea). There are two special status amphibian in the ecoregion: the Critically endangered plantation Glass Frog (Hyalinobatrachium colymbiphyllum) and the Vulnerable Camron mushroom-tongued salamander (Bolitoglossa lignicolor).

Threatened mammals found in the Panamanian dry forests include the: Endangered Central American Spider Monkey (Ateles geoffroyi), the Vulnerable Giant Anteater (Myrmecophaga tridactyla), the Near Threatened Handley’s Tailless Bat (Anoura cultrata), the Vulnerable Lemurine Night Monkey (Aotus lemurinus), the Near Threatened Margay (Leopardus wiedii), the Near Threatened Yellow Isthmus Rat (Isthmomys flavidus), the Near Threatened White-lipped Peccary (Tayassu pecari), and the Near Threatened Spectral Bat (Vampyrum spectrum). There are two special status bird species occurring in the ecoregion: the Endangered Great Green Macaw (Ara ambiguus) and the Near Threatened Olive-sided Flycatcher (Contopus cooperi).

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Niger Coastal Delta Habitat

The Niger Coastal Delta is an enormous classic distributary system located in West Africa, which stretches more than 300 kilometres wide and serves to capture most of the heavy silt load carried by the Niger River at is mouth on the Atlantic. The peak discharge at the mouth is around 21,800 cubic metres per second in mid-October. The Niger Delta coastal region is arguably the wettest place in Africa with an annual rainfall of over 4000 millimetres. Vertebrate species richness is relatively high in the Niger Delta, although vertebrate endemism is quite low. The Niger Delta swamp forests occupy the entire upper coastal delta. Historically the most important timber species of the inner coastal delta was the Abura (Fleroya ledermannii), a Vulnerable swamp-loving West African tree, which has been reduced below populations viable for timber harvesting in the Niger Delta due to recent over-harvesting of this species as well as general habitat destruction of the delta due to the expanding human population here. Other plants prominent in the inner coastal delta flood forest are: the Azobe tree (Lophira alata), the Okhuen tree (Ricinodendron heudelotii ), the Bitter Bark Tree (Sacoglottis gabonensis), the Rough-barked Flat-top Tree (Albizia adianthifolia), and Pycnanthus angolensis. Also present in its native range is the African Oil Palm (Elaeis guineensis).

Some of the reptiles found in the upper coastal Niger Delta are the African Banded Snake (Chamaelycus fasciatus); the West African Dwarf Crocodile (Osteolaemus tetraspis, VU); the African Slender-snouted Crocodile (Mecistops cataphractus); the Benin Agama (Agama gracilimembris); the Owen's Chameleon (Chamaeleo oweni); the limited range Marsh Snake (Natriciteres fuliginoides); the rather widely distributed Black-line Green Snake (Hapsidophrys lineatus); Cross's Beaked Snake (Rhinotyphlops crossii), an endemic to the Niger Basin as a whole; Morquard's File Snake (Mehelya guirali); the Dull Purple-glossed Snake (Amblyodipsas unicolor); the Rhinoceros Viper (Bitis nasicornis). In addition several of the reptiles found in the outer delta are found within this inner coastal delta area.

There are a number of notable mammals present in the inner coastal delta, including the Near Threatened Olive Colobus (Procolobus verus) that is restricted to coastal forests of West Africa and is found here in the inner coastal Niger Delta. Also found here is the restricted distribution Mona Monkey (Cercopithecus mona), a primate often associated with rivers. Also occurring here is the limited range Black Duiker (Cephalophus niger), a near-endemic to the Niger River Basin. In addition, the Endangered Chimpanzee (Pan troglodytes) is found in the Niger Delta. The near-endemic White-cheeked Guenon (Cercopithecus erythrogaster, VU) is found in the inner coastal delta. The Critically Endangered Niger Delta Red Colubus (Procolobus pennantii ssp. epieni), which primate is endemic to the Niger Delta is also found in the inner coastal delta.

Five threatened marine turtle species are found in the mangroves of the lower coastal delta: Leatherback Sea Turtle (Dermochelys coriacea, EN), Loggerhead Sea Turtle (Caretta caretta, EN), Olive Ridley Turtle (Lepidochelys olivacea, EN), Hawksbill Sea Turtle (Eretomychelys imbricata, CR), and Green Turtle (Chelonia mydas, EN).

Other reptiles found in the outer NIger Delta are the Nile Crocodile (Crocodylus niloticus), African Softshell Turtle (Trionyx triunguis), African Rock Python (Python sebae), Boomslang Snake (Dispholidus typus), Cabinda Lidless Skink (Panaspis cabindae), Neon Blue Tailed Tree Lizard (Holaspis guentheri), Fischer's Dwarf Gecko (Lygodactylus fischeri), Richardson's Leaf-Toed Gecko (Hemidactylus richardsonii), Spotted Night Adder (Causus maculatus), Tholloni's African Water Snake (Grayia tholloni), Smith's African Water Snake (Grayia smythii), Small-eyed File Snake (Mehelya stenophthalmus), Western Forest File Snake (Mehelya poensis), Western Crowned Snake (Meizodon coronatus), Western Green Snake (Philothamnus irregularis), Variable Green Snake (Philothamnus heterodermus), Slender Burrowing Asp (Atractaspis aterrima), Forest Cobra (Naja melanoleuca), Rough-scaled Bush Viper (Atheris squamigera), and Nile Monitor (Varanus niloticus).

There are a limited number of amphibians in the inner coastal delta including the Marble-legged Frog (Hylarana galamensis). At the extreme eastern edge of the upper delta is a part of the lower Niger and Cross River watersheds that drains the Cross-Sanaka Bioko coastal forests, where the near endemic anuran Cameroon Slippery Frog (Conraua robusta) occurs.

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Comments: Marine; open ocean, often near edge of continental shelf; also seas, gulfs, bays, and estuaries. Mainly pelagic, seldom approaching land except for nesting (Eckert 1992). Concentrates in summer in waters mostly 20-40 m deep near Cape Canaveral, Florida. Dives almost continuously, to depths of up to at least several thousand meters; may linger at the surface at midday but spends most of time submerged.

Nests on sloping sandy beaches backed up by vegetation, often near deep water and rough seas. Largest colonies use continental, rather than insular, beaches (CSTC 1990). Absence of a fringing reef appears to be important. Deposits eggs in moist sand. Individuals sometimes change to different nesting beach between nestings during a single year; changed to sites 30-110 km away in West Indies (Eckert et al. 1989; see also Keinath and Musick 1993). May rapidly occupy newly formed nesting habitat (Pritchard 1992).

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Habitat and Ecology

Habitat and Ecology

D. coriacea is an oceanic, deep-diving marine turtle inhabiting tropical, subtropical, and subpolar seas. Leatherbacks make extensive migrations between different feeding areas at different seasons, and to and from nesting areas. Leatherbacks feed predominantly on jellyfishes, salps and siphonophores. Females usually produce several (3-10) clutches of 60-90 eggs in a reproductive season, and typically have a re-migration interval of multiple years (2+) between subsequent reproductive seasons. For a thorough review of Leatherback biology, please see Eckert et al. (2012).



Systems
  • Terrestrial
  • Marine
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General Habitat

Marine
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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.

Range depth: 1230 (high) m.

Habitat Regions: temperate ; tropical ; saltwater or marine

Aquatic Biomes: pelagic ; coastal

Other Habitat Features: intertidal or littoral

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Depth range based on 10078 specimens in 1 taxon.
Water temperature and chemistry ranges based on 9509 samples.

Environmental ranges
  Depth range (m): 0 - 4250
  Temperature range (°C): 2.275 - 29.522
  Nitrate (umol/L): 0.010 - 32.029
  Salinity (PPS): 30.381 - 37.189
  Oxygen (ml/l): 2.556 - 7.553
  Phosphate (umol/l): 0.031 - 2.072
  Silicate (umol/l): 0.616 - 33.109

Graphical representation

Depth range (m): 0 - 4250

Temperature range (°C): 2.275 - 29.522

Nitrate (umol/L): 0.010 - 32.029

Salinity (PPS): 30.381 - 37.189

Oxygen (ml/l): 2.556 - 7.553

Phosphate (umol/l): 0.031 - 2.072

Silicate (umol/l): 0.616 - 33.109
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Highly pelagic, spending much of its life far off­shore, but often also close to shore.

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 This species generally inhabits open seas and is capable of diving to 1200 m.
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Juveniles and adults are both pelagic.
  • Lutz and Musick, 1997; Ernst and Barbour, 1989.
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Adults are truly pelagic; they are strong swimmers inhabiting the open seas. Mature females prefer to nest on sandy tropical beaches with deep-water approaches, although shallow water beaches are also used in certain regions. Very little is known about juvenile leatherbacks in the ocean, although recently some small individuals have been found concentrated in waters off western Africa (8).
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Migration

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Moves hundreds or thousands of kilometers between nesting beaches and distant marine waters; transequatorial migrations have been documented. Pattern of epibiont colonization in Caribbean suggests that gravid turtles do not arrive from temperate latitudes until just prior to nesting, and that they go directly to a preferred nesting beach; nesters apparently arrive asynchronously (Eckert and Eckert 1988). Individual females may nest on multiple islands within a region; a female that nested on St. Croix, Virgin Islands, during the next 18 days, nested also on Isla Vieques and Isla Culebra (Keinath and Musick 1993); see also Boulon et al. (1996). Caribbean nesters apparently move north along Atlantic coast after nesting (appear at least as far north as the northeastern U.S. in late summer; Boulon et al. 1988). A leatherback tagged in Chesapeake Bay in late May 1985 was captured off southern Cuba in late July 1986 (Keinath and Musick 1990). Leatherbacks from nesting areas in Suriname and Costa Rica (Caribbean coast) were found in summer off Nova Scotia (James 2004).

Morreale et al. (1996) documented a migration corridor extending from the Pacific coast of Costa Rica through the vicinity of the Galapagos Islands.

A nesting female tagged in Suriname was captured off Ghana, West Africa, less than 1 year later (Eckert 1992).

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Trophic Strategy

Comments: Principal food is jellyfish, though other invertebrates, fishes, and seaweed sometimes are eaten. Pelagic foraging may focus on jellyfish in the deep scattering layer (Eckert 1992).

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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.

Animal Foods: fish; mollusks; aquatic or marine worms; aquatic crustaceans; echinoderms; cnidarians; zooplankton

Primary Diet: carnivore (Eats other marine invertebrates)

  • 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.
  • 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.
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Omnivorous, but prefers gelatinous animals such as jellyfish, salp, and pelagic tunicates.
  • Lutz and Musick, 1997; Ernst and Barbour, 1989.
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Associations

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.

Commensal/Parasitic Species:

  • 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.
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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.

Known Predators:

  • Chiang, M. 2003. The plight of the turtle. Science World, 59: 8.
  • Ernst, C., J. Lovich, R. Barbour. 1994. Turtles of the United States and Canada. Washington, D.C., USA: Smithonian Institution Press.
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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 21 - 80

Comments: This species is represented by a large number of nesting occurrences, but few of them have more than a few hundred nesting females (Spotila et al. 1996, UNEP 2003).

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Global Abundance

10,000 - 1,000,000 individuals

Comments: Pritchard (1982) estimated 115,000 breeding females worldwide, though his estimates may have been too high, especially for Mexico. Estimated world population in the early 1990s was reported as 136,000 breeding females by Pritchard (1992). In contrast, Spotila et al. (1996) estimated the worldwide population of nesting females at 26,200-42,000, with the majority of animals occurring in the Atlantic Ocean and Caribbean Sea where the population was estimated at 27,608. An estimated 100-900 leatherbacks occur in summer in waters off the northeastern U.S. (Shoop and Kenney 1992). See Cook (1981) for information on status in Canada.

Spotila et al. (2000) estimated total adult (breeding) population at 1,690 females in the eastern Pacific (down from an estimated 4,600-6,500 in 1996) and concluded leatherbacks are on the verge of extinction in the Pacific. Another estimate suggested a total of 2,300 adult females in the entire Pacific (Crowder 2000).

In Florida, between 1988 and 1992, annual reported leatherback nests varied between 98 and 188 (USFWS 1998). In the 1980s and early 1990s, about 18-55 females nested each year on St. Croix in the U.S. Virgin Islands (Boulon et al. 1996); increased to 100+ in 1997. In 1997, more than 80 females nested at Culebra Island, Puerto Rico.

Nest counts at the largest nesting colony in Mexico reported less than 250 in 1998-1999 (Eckert unpubl. results in Spotila et al. 2000). Spotila et al. (2000) predicted that without protection the population breeding at Playa Grande, Costa Rica (once the 4th largest nesting colony in the world), would be reduced to around 50 nesting females by 2003-2004.

In the mid-1990s, few beaches had more than a few hundred nesting females (Spotila et al. 1996). Only four nesting areas presently support more than 1,000 breeding females: the Pacific coast of Mexico probably fewer than 5,000 though formerly many more; Pacific coast of French Guiana, 4,500-6,500; peninsular Malaysia, 1,000-2,000; and the Kepala Burung region of Indonesia (UNEP 2003).

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General Ecology

Eggs and hatchlings incur high rates of mortality from predation; humans are significant egg predators. Adults often die from drowning in commercial fishing nets and from eating floating debris, especially plastic. In Malaysia, egg survivorship (to hatching) was 0.63 (see Iverson 1991).

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Distribution ecology

The leatherback turtle has the largest range of any sea turtle and is found from Alaska to the southern tip of Africa and present in both the Atlantic and Pacific Oceans.Adults mate in tropical waters and females nest on beaches throughout the tropics.They migrate great distances to cooler waters and are travelling almost constantly, swimming some 10,000km per year.An adult Dermochelys coriacea is able to survive in temperate and sub-arctic waters due to its large size (thermal inertia), insulating sub-epidermal fat and counter-current blood flow, allowing it to maintain a deep body temperature of at least 18°C.Although the range of juveniles is unknown, they appear to be unable to leave the warmth of tropical waters.They live a pelagic existence and adults feed primarily on jellyfish.
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Life History and Behavior

Behavior

Behaviour

Feeds largely on jellyfish and is capable of making dives as deep as 1,000 m below sea surface.

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Life Cycle

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.

Development - Life Cycle: temperature sex determination

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Life Expectancy

Lifespan/Longevity

We have no information on the lifespan of Dermochelys coriacea.

Average lifespan

Status: captivity:
30 years.

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

Maximum longevity: 30 years Observations: The leatherback sea turtle is intriguing amongst reptiles because it features a sort of endothermy. Even so, it lives at least 30 years with anecdotal evidence suggesting a maximum longevity of 70-80 years (Spotila et al. 2000).
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Reproduction

Lays up to 10+ (average 5 in Virgin Islands, 5-7 in Puerto Rico) clutches of 50-170 eggs (typically 70-90 normal eggs in the Atlantic, usually fewer than 60 in the eastern Pacific) at intervals of about 1-2 weeks; most individuals nest every 2-3 years. Nests at night, March-August in Western Hemisphere. Eggs hatch in 8-10 weeks. Reportedly sexually mature in 6-10 years, or possibly less, or perhaps 20-50 years; females in the Atlantic mature at a carapace length of 137-145 cm, Pacific females mature at slightly smaller size (Eckert 1992). Zug and Parham (1996) conducted a skeletochronological analysis and concluded that "for conservation management purposes, 9 years is a likely minimum age for maturity based on the youngest adult in the sample." Limited data indicate a post-maturation longevity of up to about two decades (Pritchard 1996).

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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.

Mating System: polygynandrous (promiscuous)

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.

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.

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.

Key Reproductive Features: semelparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous

Average number of offspring: 105.

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.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female)

  • Eckert, S., M. James, R. Myers. 2005. Migratory and reproductive movements of male leatherback turtles. Marine Biology, 147(4): 845.
  • Barbour, R., C. Ernst. 1972. Turtles of the United States. Lexington, Kentucky: University Press of Kentucky.
  • 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.
  • 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.
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Nests on tropical mainland beaches and on islands, normally at night. The nesting process takes approximately 1.5 hours. The female lays around 6 clutches in a reproductive season, each with about 81 eggs. Hatchlings are from 56-63 mm carapace length when they emerge. A female nests every 2 or more years. In the Atlantic, nesting takes place from April to November.
  • Lutz and Musick, 1997; Ernst and Barbour, 1989.
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Evolution and Systematics

Functional Adaptations

Functional adaptation

Vascular lining helps maintain body temperature: leatherback sea turtle
 

The vascular lining in the trachea of adult leatherback sea turtles helps them maintain body temperature while foraging in cold water via counter-current exchange.

   
  "[T]he trachea is lined throughout by a continuous vascular plexus. This  contains a high proportion of longitudinally arranged, large-diameter  blood vessels lying mainly in the deeper two-thirds of the mucosa, with  prominent cross-connections between them. The arrangement is consistent  with their functioning as a counter-current arrangement, retaining heat  and maintaining body temperatureWe believe that the vascular lining of the long adult leatherback trachea functions in analogous fashion to nasal turbinates." (Davenport et al. 2009:3445-6)
  Learn more about this functional adaptation.
  • Davenport J; Fraher J; Fitzgerald E; McLaughlin P; Doyle T; Harman L; Cuffe T; Dockery P. 2009. Ontogenetic changes in tracheal structure facilitate deep dives and cold water foraging in adult leatherback sea turtles. Journal of Experimental Biology. 212(21): 3440-7.
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Functional adaptation

Trachea enables deep dives: leatherback sea turtle
 

The trachea of adult leatherback sea turtles enables deep dives via a compressible cartilaginous structure.

   
  "Functionally it appears that the deep diving mammals have a cartilaginous tracheal design that will facilitate progressive collapse with increasing depth, whereas shallow divers have rigid upper portions of the tracheae that remain patent during divesthe adult leatherback trachea has a structure markedly different from that of other living sea turtles. It consists of an elliptical tube of nearcontinuous uncalcified cartilage, rather than a sequence of circular, closely packed tracheal rings. The tube is easily compressibleWe believe that the elasticity of tracheal cartilage (combined with expansion of the remaining tracheal air during ascents) will be sufficient to reinflate the trachea"  (Davenport et al. 2009:3440, 3445-6)

  Learn more about this functional adaptation.
  • Davenport J; Fraher J; Fitzgerald E; McLaughlin P; Doyle T; Harman L; Cuffe T; Dockery P. 2009. Ontogenetic changes in tracheal structure facilitate deep dives and cold water foraging in adult leatherback sea turtles. Journal of Experimental Biology. 212(21): 3440-7.
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Molecular Biology and Genetics

Molecular Biology

Barcode data: Dermochelys coriacea

The following is a representative barcode sequence, the centroid of all available sequences for this species.


There is 1 barcode sequence available from BOLD and GenBank.   Below is the sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen.  Other sequences that do not yet meet barcode criteria may also be available.

TCTACTAATCATAAAGACATTGGCACCCTATACCTAATTTTTGGGGCCTGAGCAGGAATAGTAGGCACAGCACTC---AGCCTATTAATCCGTGCAGAACTAAGCCAACCGGGAACCCTCCTAGGAGAT---GACCAAATTTACAATGTCATCGTTACAGCCCATGCCTTCATTATAATCTTCTTCATAGTTATACCAGTTATAATCGGCGGTTTCGGAAACTGACTTGTTCCCCTTATA---ATTGGAGCACCAGACATGGCATTCCCACGAATAAACAACATAAGCTTTTGACTTTTACCTCCCTCACTGTTACTACTTCTAGCATCATCAGGAATTGAAGCAGGTGCAGGAACAGGCTGAACAGTCTATCCTCCACTAGCTGGAAACCTAGCCCACGCTGGTGCTTCTGTAGACCTA---ACTATCTTTTCTCTGCACCTAGCTGGTGTTTCATCAATTTTAGGAGCTATTAACTTCATTACTACAGCAATCAACATAAAATCTCCAGCTATATCACAATACCAAACACCATTATTTGTATGATCTGTATTAATTACAGCCGTTCTATTATTACTCTCATTGCCAGTACTAGCTGCA---GGAATCACCATACTACTTACAGATCGAAACCTAAACACAACCTTTTTTGATCCTTCAGGAGGAGGAGACCCAATCCTATACCAACACCTATTCTGATTCTTTGGCCATCCAGAAGTATACATCCTAATTCTACCAGGATTCGGCATAATCTCACATATCGTCACCTATTATGCTGGTAAAAAA---GAACCATTTGGTTACATAGGAATAGTTTGAGCAATAATATCC
-- end --

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Statistics of barcoding coverage: Dermochelys coriacea

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Specimens with Barcodes: 16
Species With Barcodes: 1
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Conservation

Conservation Status

National NatureServe Conservation Status

Canada

Rounded National Status Rank: N2 - Imperiled

United States

Rounded National Status Rank: N2B - Imperiled

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NatureServe Conservation Status

Rounded Global Status Rank: G2 - Imperiled

Reasons: Oceanic distribution is nearly worldwide, but the number of nesting sites is few; many nesting areas have few breeding females and suffer from some human predation; range and number of occurrences have undergone reduction; recent severe population declines at some nesting locations.

Intrinsic Vulnerability: Highly vulnerable

Environmental Specificity: Very narrow to narrow.

Other Considerations: Individuals may move hundreds to thousands of kilometers between nesting beaches and distant marine waters; this increases vulnerability to incidental take.

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IUCN Red List Assessment


Red List Category
VU
Vulnerable

Red List Criteria
A2bd

Version
3.1

Year Assessed
2013

Assessor/s
Wallace, B.P., Tiwari, M. & Girondot, M.

Reviewer/s
Chaloupka, M.Y., Dutton, P.H., van Dijk, P.P., Mortimer, J.A., Casale, P., Bolten, A.B., Eckert, K.L., Nel, R., Musick, J.A., Pritchard, P.C.H., Dobbs, K. & Miller, J.

Contributor/s
Barragan, A., Amorocho, D., Beheret, N., Chacon, D., Chan, E., DeFreitas, R., Diez, C., Eckert, S., Entraygues, M., Felix, M., Formia, A., Garner, J., Girard, A., Guada, H., Hamann, M., Harrison, E., Honarvar, S., Hughes, G., Kalamandeen, M., Kapurusinghe, T., Livingstone, S., Lloyd, C., Lopez-Mendilaharsu, M., Marcovaldi, M., Meylan, A., Nel, R., Patino-Martinez, J., Pilcher, N.J., Reina, R., Sarti, L., Shanker, K., Stewart, K., Tomas, J., Turny, A. & Urteaga, J.

Justification

Rationale

The global population of Leatherback turtles (Dermochelys coriacea) comprises seven subpopulations (see Figure 2 in attached PDF) that vary widely in population size, geographic range, and population trends, and are the appropriate units for assessment of global conservation status for this species (Wallace et al. 2010, 2011). As such, we performed assessments for each of the seven subpopulations, in addition to the combined global population assessment required by the IUCN (see Table 1 in attached PDF). Due to this species’ geographically widespread distribution, Criterion A was the only appropriate criterion for assessment that could be applied to the global Leatherback population. Generation length was estimated as 30 years. Estimation of global population change based on subpopulation trends (weighted by subpopulation sizes relative to the global population size) produced an estimate of -40.1% decline over the past three generations (see Table 2 in attached PDF), corresponding to a category of Vulnerable based on Criterion A2 (i.e., threats are not reversible nor have they ceased), subcriteria b (i.e., an index of abundance appropriate to the taxon—annual nest counts—was used) and d (i.e., decline was due to actual or potential levels of exploitation). In contrast, assessment of the data under Criterion A4—past, present, and future abundance—revealed that the global Leatherback population trends over three generations will no longer meet thresholds for threat categories by 2020 (-29.4%), and will be increasing by 2030 (3%) and beyond (104% by 2040) (see Table 3 in attached PDF). Therefore, within the next ten years, the global Leatherback population might no longer qualify as “Threatened”—i.e. a category listing of Vulnerable, Endangered, or Critically Endangered—according to the IUCN Red List Criteria.

However, future population increases will be dependent on the success of conservation actions mitigating current and future threats to this species throughout its range, especially in breeding and foraging areas, and on no new threats arising (e.g. climate change) that could cause population declines. Moreover, nearly 99% of the global population (based on data available currently) will be contained within the Northwest Atlantic, which obscures the declines of the Pacific subpopulations and threatened status of other relatively small subpopulations (e.g. Southwest Atlantic, Southwest Indian) (see Figure 3 in attached PDF), not to mention data deficient subpopulations (Northeast Indian, Southeast Atlantic). While these results demonstrate that Leatherbacks, as a single taxonomic entity, will not go extinct globally in the next generation, the global listing is not an appropriate representation of the conservation status of the biologically relevant subpopulations that make up the global Leatherback population. For this reason, the subpopulation-level Red List assessments for Leatherbacks should be given priority in evaluating the true global extinction risk for this species.


Justification

Comprehensive analyses of 39 existing datasets—including 28 time series datasets with ≥10 years of data—of abundance of nesting females or their nesting activities on beaches revealed different population trends among subpopulations, but a global decline overall based on subpopulation trends weighted by subpopulation size three generations ago relative to combined global population size (see Table 2 in attached PDF for all datasets used). Overall, considering only datasets with ≥10 yr of abundance data, the total global abundance across Leatherback subpopulations had declined from 90,599 nests yr-1 to 54,262 nests yr-1 over three generations until 2010. Using average conversion factors from different subpopulations to provide bracketed estimates of nesting female abundance (i.e. 5 and 7 clutches per female, three years for re-migration intervals, intermediate between subpopulation averages; TEWG 2007, Reina et al. 2002), these annual nesting abundance values correspond to approximately 12,943-18,120 nesting females yr-1 (or 38,828-54,359 adult females) three generations ago and 7,752-10,852 nesting females yr-1 (or 23,255-32,557 adult females) in 2010. Because we did not include abundance data from several rookeries that had <10 yr of data—including Gabon, which is the largest Leatherback rookery in the world (Witt et al. 2009), as well as Grand Riviere and Fishing Pond, Trinidad, Armila, Panama, and Gulf of Urubá, Colombia (TEWG 2007, Patiño-Martínez et al. 2008)—in our annual and total abundance subpopulation and global abundance estimates, these values should be considered conservative estimates.

Overall, although the global listing for Leatherbacks was derived by abundance-weighted analyses of three-generation trends for all subpopulations with available data, it is not an appropriate representation of conservation status of biologically relevant population units (i.e. subpopulations) that make up the global Leatherback population. Subpopulation assessments demonstrated wide variation not only in status of individual subpopulations (as indicated by the Red List Categories), but also in how categories were derived for each subpopulation (as indicated by the Red List Criteria used) (see Table 1 in attached PDF). Specifically, final threat categories were triggered by thresholds under different criteria, depending on whether a subpopulation has declined significantly over time (e.g. East Pacific, West Pacific), was geographically constrained (e.g. Southwest Indian Ocean), or characterized by small (e.g. Southwest Indian Ocean) or very small population sizes (e.g. Southwest Atlantic Ocean). Therefore, the variation in conservation status among subpopulations warrants preference for subpopulation assessments over the global assessment when evaluating and describing the global conservation status of Leatherbacks.

Presently, the Northwest Atlantic subpopulation—i.e. from Florida, USA throughout the Wider Caribbean—is large and increasing (TEWG 2007) (Table 2 in attached PDF). Furthermore, the Southeast Atlantic subpopulation—i.e. West Africa, especially Gabon—is the largest in the world (Witt et al. 2009), but long-term trend data are not available for this assessment (TEWG 2007). The existence of these large (and increasing in at least one case) subpopulations makes it extremely unlikely that Leatherbacks globally will go extinct in the near future. If current trends in the Northwest Atlantic subpopulation continue, the global population trend might no longer meet thresholds for IUCN Threatened categories (i.e., Vulnerable, Endangered, Critically Endangered) within ten years (Table 3 in attached PDF). In fact, if current trends continue, future global population sizes are projected to increase to 184,662 nests yr-1 (approximately 26,380-36,932 females yr-1, 79,141-110,797 adult females total) within one generation (i.e. by 2040). The projected abundance of the Northwest Atlantic subpopulation alone will account for nearly 99% of the global Leatherback population abundance by that time (Figure 3 and Table 3 in attached PDF), and increase from 46% of historical global population abundance three generations ago.

In spite of the large and increasing Northwest Atlantic subpopulation, the magnitudes of declines for the East Pacific subpopulation (i.e., which nests along the Pacific coast of the Americas) and, to a slightly lesser extent, the West Pacific subpopulation (i.e., Malaysia, Indonesia, Papua New Guinea, Solomon Islands) over three generations were the main driver the global decline result. Specifically, the East Pacific subpopulation has declined by > 97% over three generations (from >35,000 nests yr-1 to <1,000 nests yr-1, or >5,000 nesting females yr-1 to < 140 nesting females yr-1) (Eckert 1993, Santidrián Tomillo et al. 2007, Sarti Martínez et al. 2007), and its historic abundance accounted for roughly 39% of the estimated global abundance three generations ago (Table 1 in attached PDF). Similarly, the West Pacific subpopulation has declined >80% over three generations, from >12,000 nests yr-1 (2,600 females yr-1) to <2,200 nests yr-1 (<500 females yr-1) (Eckert 1993, Chan and Liew 1996, Dutton et al. 2007, Hitipeuw et al. 2007, Tapilatu et al. 2013), and its historic abundance accounted for 14% of the estimated global abundance three generations ago. Both of these subpopulations are projected to decline further in coming decades (Table 3 in attached PDF). Population declines in these subpopulations (and others) have been attributed to extensive egg harvest and mortality due to incidental capture in fishing gear (Eckert 1993, Wallace and Saba 2009, Tapilatu et al. 2013). Considering the precedent of the collapse of the historically large Pacific subpopulations, the persistence of significant threats in all regions (see Wallace et al. 2011 and Eckert et al. 2012 for review) warrants concern for the future viability of even the largest subpopulations. Current efforts to protect Leatherbacks, their offspring, and their habitats must be maintained—or even augmented, where possible—to reverse declines in Pacific and Indian Ocean subpopulations and to sustain population growth in the Northwest Atlantic.

To explore future projections of Leatherback subpopulation and global abundance and trends, we also applied Criterion A4, which analyzes the global population trend within time intervals from the past, present, and future (Table 3 in attached PDF). Because the length of three generations (~90 yr) was greater than the length of our available datasets, we used the historical abundance values shown in Tables 3 and 4 (see attached PDF) as the baseline population sizes for “moving window” analyses. According to our assessment of the data under Criterion A4, it would no longer qualify as “Threatened” according to IUCN Red List Criteria by 2020 (three-generation decline of 29.4%), and would qualify as Least Concern by 2030 (3% increase) under IUCN Guidelines (IUCN 2011) (Table 3 in attached PDF). This discrepancy between A4 and A2 illustrates a dichotomy in how extinction risk is assessed by these two criteria, despite the same empirical data being used for assessments. Whereas A2 assesses percent decline over time, using the historical abundance as the baseline, A4 uses historical as well as current abundance to project future abundance, and as such accounts for recent growth in subpopulations in the global population estimate. Because the IUCN Guidelines stipulate that multiple criteria be evaluated, the criterion that triggers the highest threat category must be selected for the official assessment. Therefore, Leatherbacks globally are considered Vulnerable (A2b,d) based on IUCN Guidelines (IUCN 2011).

Nonetheless, these results further illustrate the inability of the global assessment to adequately characterize variation among subpopulations. The likelihood of global extinction of this species is extremely low (Tables 2 and 3 in attached PDF); however, the Northwest Atlantic subpopulation alone is projected to account for nearly 99% of total global Leatherback abundance by 2040, with four other subpopulations for which data were available for this assessment accounting for the remaining 1% (Figure 3 and Table 3 in attached PDF). Such a global assessment produces a result indicating no risk of species-level extinction based on the mere existence of any Leatherback subpopulation, while obscuring the dire conservation situation of declining or extinct subpopulations (e.g., the Pacific subpopulations). This type of assessment and its result are contrary to the IUCN SSC Marine Turtle Specialist Group’s (MTSG) mission to guide conservation of marine turtles and their ecological roles. For these reasons, the MTSG defined subpopulations (i.e., regional management units; Wallace et al. 2010) for all marine turtle species, including Leatherbacks, to provide a biologically described framework for evaluating conservation status of appropriate population segments. A global marine turtle population is an amalgam of its subpopulations, all of which are valuable for maintaining the health of the “species” in terms of evolutionary history, genetic diversity, and life history variations. For these reasons, the inability of marine turtle global assessments to appropriately account for variation among subpopulations (see Seminoff and Shanker 2008 for review) further supports the primacy of subpopulation assessments when describing conservation status of marine turtles globally.

Previous global Leatherback assessments (Pritchard 1982, Spotila et al. 1996), including the previous Leatherback Red List assessment (Sarti Martinez 2000), also described global declines in Leatherbacks. However, these previous assessments lacked the geographic breadth and rigour of time series datasets accessed for the current assessment. Spotila et al. (1996) estimated the global Leatherback population in 1995 to be approximately 34,500 adult females (range: 26,200-42,900 females), and stated that this value was roughly a third of the only existing global estimate at the time (115,000 adult females; Pritchard 1982). However, there were several significant assumptions in the Pritchard (1982) estimate that make its use as a reliable global population estimate tenuous, not the least of which was the lack of robust, nesting beach-based estimates of the East Pacific subpopulation abundance on which the regional and global estimates were constructed (see Mrosovsky 2003 for review). Sarti Martinez (2000) assessed the global Leatherback population as Critically Endangered largely on the evidence of significant declines in the East Pacific subpopulation (based on the Pritchard [1982] and Spotila et al. [1996] estimates) and Malaysian rookery, despite some indications of large populations in other regions, such as the Northwest and Southeast Atlantic.

In addition, abundance of several rookeries has increased substantially in the time since these assessments were conducted. For example, estimates for Trinidad, St. Croix, Puerto Rico, and Florida used by Spotila et al. (1996) were all substantially lower—by an order of magnitude in some cases—than current estimates (Table 3 in attached PDF). Furthermore, the current assessment only included time series datasets of a decade or longer in abundance estimates, whereas Spotila et al. (1996) included abundance estimates based on variable numbers of nesting seasons. The 2010 abundance estimates presented in the current assessment are generally lower, but overlap with the 1995 range in estimated abundance reported by Spotila et al. (1996). If abundance estimates from all rookeries with available nesting data (e.g. Panama [~8,000 nests yr-1], Colombia [2,300 nests yr-1], Trinidad [>40,000 nests yr-1, and especially Gabon [36,185-126,480 nests yr-1]; Table 3 in attached PDF) were included in the 2010 assessment, the total global abundance of Leatherbacks in 2010 would be much higher than the estimate shown in Table 3, and would exceed the average estimate of Spotila et al. (1996). However, this is not necessarily indicative of a global population increase, but rather an increase in available information. Therefore, given the availability of new datasets from all Leatherback subpopulations globally, use of previous estimates (Pritchard 1982, Spotila et al. 1996) to characterize global Leatherback population abundance is no longer appropriate.

Interpreting the current assessment (2010) in the context of previous assessments and available data at present, the global Leatherback population has not collapsed, and, in fact, appears to be larger than estimated in previous global assessments (Spotila et al. 1996). This result appears counter-intuitive with the Vulnerable category to which this subpopulation has been assigned, but it can be traced to the nature of the procedure for applying Criterion A to long-lived, widely distributed species like marine turtles (see Seminoff and Shanker 2008 for review). The change in IUCN Red List Category from Critically Endangered (in 2000) to Vulnerable (assessment year 2010) is mostly due to new datasets made available for assessment, and associated detection of increasing trends that were not reported previously, as well as a rigorous application of the IUCN 3.1 Criteria. The continued severe declines of the Pacific subpopulations require urgent and effective conservation interventions to prevent complete collapse (Spotila et al. 2000, Santidrián Tomillo et al. 2007, Sarti Martínez et al. 2007, Tapilatu et al. 2013). Furthermore, the projected increase in the global population is predicated entirely on continued growth of the Northwest Atlantic subpopulation alone, which itself depends on sustained conservation efforts to protect Leatherbacks, their offspring, and their habitats.

Assessment Procedure:

Given the widespread, long-lived nature of Leatherback turtles, Criterion A (i.e., decline in population of mature individuals over time) is the only appropriate criterion that could be used for this assessment; the restricted geographic range and small population size criteria (Criterion B, C, and D) did not apply, and no population viability analysis was available (Criterion E). However, Criteria A-D were applied in subpopulation assessments (see Leatherback subpopulation assessments for details; Table 1 in attached PDF).

We obtained time series datasets of abundance of nesting females or their nesting activities collected on Leatherback rookeries (i.e., nesting beaches) around the world, and organized data by subpopulations. For marine turtles, annual counts of nesting females and their nesting activities (more often the latter) are the most frequently recorded and reported abundance metric across index monitoring sites, species, and geographic regions (NRC 2010). Conversion from number of nests to number of nesting females requires estimates of clutch frequency (i.e. number of clutches per nesting female per breeding season) (e.g. Reina et al. 2002), which are not available for all rookeries and subpopulations. Therefore, we presented and analysed all abundance data in numbers of confirmed nests yr-1, as this metric was the most commonly available (Table 2 in attached PDF). See Sources of Uncertainty for discussion of caveats associated with these conversion factors.

We calculated annual and overall population trends for each rookery within a subpopulation, and then calculated average subpopulation trends by weighting rookery population trends by rookery abundance 3 generations ago relative to subpopulation abundance three generations ago. We then repeated this step to derive the global population trend by weighting subpopulation trends by subpopulation abundance three generations ago relative to global abundance three generations ago (Table 2 in attached PDF). We only included time series datasets of ≥10 yr in trend estimations, although we included all rookeries for which we obtained abundance values in the overall summary tables (Table 2 in attached PDF). Because rookeries represent varying proportions of total subpopulation sizes, we ensured that time series from major rookeries within each subpopulation were included in analyses such that the majority of subpopulation abundance was represented. In cases where that was not possible (e.g. Southeast Atlantic, Northeast Indian), we did not derive a subpopulation trend, and such cases were excluded from calculation of global trends.

The most recent year for available abundance data across all rookeries and subpopulations was 2010. Where time series ended prior to 2010, we estimated population sizes for each rookery through 2010 based on the population trend for existing years (e.g. French Guiana, Trinidad). Furthermore, if a longer time series for a rookery within a subpopulation was available that reflected a trend not captured by shorter time series, we estimated historical abundance to calculate overall declines for that subpopulation. For example, abundance data for three of five index sites in the Mexican Pacific—the East Pacific subpopulation—begin in the early 1980s, while the remaining sites (i.e., Barra de la Cruz and Cahuitán, Oaxaca) begin in the early 1990s (Table 2 in attached PDF). All other sites in Mexico, as well as other sites within the same subpopulation (i.e., those in Costa Rica), showed a decline of >97%, whereas the Barra de la Cruz and Cahuitán showed much less dramatic declines, because the time series began after the broader population decline had already begun to occur. Given the synchrony in inter-annual abundance fluctuations and historical reports of high abundance among these rookeries (Eckert 1993), we assumed that the abundance at Barra de la Cruz and Cahuitán was similar to that of other Mexican rookeries at the beginning of those time series, i.e., 1982 (L. Sarti Martínez pers. comm.). This allowed us to standardize trend and abundance estimates within the Mexican rookeries.

To apply Criterion A, three generations (or a minimum of ten years, whichever is longer) of abundance data are required (IUCN 2011). In the case of the Leatherback, we conservatively estimate its generation time as 30 years (see below). For criterion A2, data from three generations ago (~100 yr) are necessary to estimate population declines beginning three generations ago up to the present (i.e. assessment) year. The challenges of this requirement on long-lived species like turtles—with generation lengths of 30 yr or more—are obvious (see Seminoff and Shanker 2008 for review). Abundance data from ~100 yr ago are not available for Leatherbacks anywhere in the world. Extrapolating backward using population trends based on current datasets was considered inappropriate because estimates produced would be biologically unrealistic and unsubstantiated, given what is currently known about sea turtle nesting densities on beaches and other factors (Mrosovsky 2003). In the absence of better information, we assumed that population abundance three generations (~100 years, one generation estimated 30 yr; see below) ago was similar to the first observed abundance rather than to assume that the population has always been in a decline (or increase) of the same magnitude as in the current generation (Table 2 in attached PDF). A similar approach was used in the Red List assessment of another long-lived, geographically widespread taxon, the African Elephant (Blanc 2008). Thus, to apply Criterion A to subpopulations (see separate subpopulation assessments) and the global population, we assumed that the abundance at the beginning of an available time series dataset had not changed significantly in the preceding three generations, and therefore used the same abundance value in trend calculations.

We also evaluated to the global population against Criterion A4 (Table 3 in attached PDF), using the same overall scheme as described above. Criterion A4 permits for analysis of population trend during a “moving window” of time, i.e. over three generations, but where the time window must include the past, present, and future. Furthermore, multiple time-frames are to be examined, and the maximum decline calculated for a given time-frame is to be compared to the thresholds (IUCN 2011). Therefore, we made the same assumption about earliest available historical abundance being equivalent to the population abundance for generations past, and estimated future population abundance in 2020, 2030, and 2040, which all fall within the next generation (i.e., 30 yr). These future projections assume that the derived population trend will continue without deviation during the next generation. Implicit in this assumption is that no changes to degree of threats or conservation efforts impacting rookeries, subpopulations, or the global population will occur during that time. Based on available information, threats to Leatherbacks globally that have caused observed declines have not ceased and are not reversible (see Wallace et al. 2011 and Eckert et al. 2012 for review), making this a reasonable assumption in the absence of better information. The global population will no longer be “Threatened” according to IUCN Red List thresholds by 2020 (-29.4% decline over three generations), and will be increasing by 2030 (3% increase) and beyond (104% increase by 2040)—i.e. IUCN category of Near Threatened or Least Concern—according to Criterion A4, depending on the “time window” applied (Table 3 in attached PDF). This result is due mainly to the currently large and growing Northwest Atlantic subpopulation, and in spite of the lack of sufficient information for the Southeast Atlantic subpopulation and the continued declines in the East Pacific and West Pacific subpopulations.


Estimating Generation Length:

Leatherback age at maturity is uncertain, and estimates range widely (see Jones et al. 2011 for review). Reported estimates fall between 9-15 yr, based on skeletochronology (Zug and Parham 1996), and inferences from mark-recapture studies (Dutton et al. 2005). Furthermore, updated skeletochronological analyses estimated Leatherback age at maturity to be between 26-32 yr (mean 29 yr) (Avens et al. 2009). Extrapolations of captive growth curves under controlled thermal and trophic conditions suggested that size at maturity could be reached in 7-16 yr (Jones et al. 2011). Thus, a high degree of variance and uncertainty remains about Leatherback age at maturity in the wild. Likewise, Leatherback lifespan is unknown. Long-term monitoring studies of Leatherback nesting populations have tracked individual adult females over multiple decades (e.g. Santidrián Tomillo et al. unpublished data, Nel and Hughes unpublished data), but precise estimates of reproductive lifespan and longevity for Leatherbacks are currently unavailable.

The IUCN Red List Criteria define generation length to be the average age of parents in a population; older than the age at maturity and younger than the oldest mature individual (IUCN 2011). Thus, for the purposes of this assessment, we estimated generation length to be 30 yr, or equal to the age at maturity (estimated to be 20 yr on average), plus a conservative estimate of reproductive half-life of 10 yr, as assumed by Spotila et al. (1996).


Sources of Uncertainty

Although monitoring of nesting activities by adult female sea turtles is the most common metric recorded and reported across sites and species, globally, there are several disadvantages to using it as a proxy for overall population dynamics, some methodological, some interpretive (NRC 2010). First, because nesting females are a very small proportion of a sea turtle population, using abundance of nesting females and their activities as proxies for overall population abundance and trends requires knowledge of other key demographic parameters (several mentioned below) to allow proper interpretation of cryptic trends in nesting abundance (NRC 2010). However, there remains great uncertainty about most of these fundamental demographic parameters for Leatherbacks, including age at maturity (see Jones et al. 2011 for review), generation length, survivorship across life stages, adult and hatchling sex ratios, and conversion factors among reproductive parameters (e.g., clutch frequency, nesting success, re-migration intervals, etc.). These values can vary among subpopulations, further complicating the process of combining subpopulation abundance and trend estimates to obtain global population abundance and trend estimates, and contributing to the uncertainty in these estimates. Second, despite the prevalence of nesting abundance data for marine turtles, monitoring effort and methodologies can vary widely within and across study sites, complicating comparison of nesting count data across years within sites and across different sites as well as robust estimation of population size and trends (SWOT Scientific Advisory Board 2011). For example, monitoring effort on Matura beach, Trinidad, has changed multiple times since the early 1990s, which necessitated a modelling exercise to estimate a complete time series for years with reliable monitoring levels (Table 2 in attached PDF). Furthermore, there was a general lack of measures of variance around annual counts provided for the assessment, which could be erroneously interpreted as equally high confidence in all estimates. Measures of variance around annual counts would provide information about relative levels of monitoring effort within and among rookeries, and thus reliability of resulting estimates. For all of these reasons, results of this assessment of global population decline should be considered with caution. For further reading on sources of uncertainty in marine turtle Red List assessments, see Seminoff and Shanker (2008).


History
  • 2000
    Critically Endangered
  • 1996
    Endangered
  • 1996
    Endangered
    (Baillie and Groombridge 1996)
  • 1994
    Endangered
    (Groombridge 1994)
  • 1990
    Endangered
    (IUCN 1990)
  • 1988
    Endangered
    (IUCN Conservation Monitoring Centre 1988)
  • 1986
    Endangered
    (IUCN Conservation Monitoring Centre 1986)
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Source: IUCN

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Current Listing Status Summary

Status: Endangered
Date Listed: 06/02/1970
Lead Region:   Southeast Region (Region 4) 
Where Listed: Entire


Population detail:

Population location: Entire
Listing status: E

For most current information and documents related to the conservation status and management of Dermochelys coriacea , see its USFWS Species Profile

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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.

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.

US Federal List: endangered

CITES: appendix i

IUCN Red List of Threatened Species: critically endangered

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

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Conservation

Estimating Dermochelys coriacea population sizes and trends is difficult due to their enormous range and pelagic existence, although data from nesting beaches shows a dramatic decline in the Pacific leatherback population.The east Pacific population is thought to have declined from 4,638 adult females in 1995 to 1,690 just 5 years later, and the trend is similar for the rest of the Pacific leatherback sub-populations.Although the Atlantic population seems healthier, with numbers of nesting females actually increasing on some beaches, yearly fluctuations make it hard to assess the overall trend. Legislation and its implementation vary drastically between the countries in which females nest, and the harvesting of eggs and adults is common in many countries.There are, however, a great number of conservation projects and protected reserves worldwide:
  • females are monitored by tagging
  • reproductive data is straight-forward to acquire and is collected at many nesting sites
  • on beaches where poaching is commonplace, eggs are sometimes removed from their original nests and re-buried in hatcheries where they are protected until they are ready to be released into the sea
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Status

Classified as Critically Endangered (CR) on the IUCN Red List 2007 (1). Listed on Appendix I of CITES (3) and Appendix I of the Convention on Migratory Species (CMS or the Bonn Convention) (4).
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Population

Population

Leatherbacks are a single species globally comprising seven biologically described regional management units (RMUs; Wallace et al. 2010), which describe biologically and geographically explicit population segments by integrating information from nesting sites, mitochondrial and nuclear DNA studies, movements and habitat use by all life stages. RMUs are functionally equivalent to IUCN subpopulations, thus providing the appropriate demographic unit for Red List assessments. There are seven Leatherback RMUs (hereafter subpopulations): Northwest Atlantic Ocean, Southeast Atlantic Ocean, Southwest Atlantic Ocean, Northeast Indian Ocean, Southwest Indian Ocean, East Pacific Ocean, and West Pacific Ocean (Figure 2 in attached PDF). Multiple genetic stocks have been defined according to geographically disparate nesting areas around the world (Dutton et al. 1999, 2013), and are included within RMU delineations (Wallace et al. 2010; shapefiles can be viewed and downloaded at: http://seamap.env.duke.edu/swot).


Population Trend
Decreasing
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Threats

Degree of Threat: Very high - high

Comments: Major threats include egg collecting and mortality associated with bycatch in longline, trawl, and gillnet fisheries throughout the range (Spotila et al. 2000, Ferraroli et al. 2004, Lewison et al. 2004). Other concerns include harvest of adult females at nest beaches for meat and oil, nesting habitat loss, pollution, and adult ingestion of floating plastics and trash (Lewison et al. 2004).

Egg harvesting: Most nest beaches are now protected in Mexico and in other parts of range, but egg exploitation continues. A long history of egg collection contributed to population declines in Malaysia (Chan and Liew 1996). In the 1980s, cash value of leatherback eggs was still so high that the Trengganu Fisheries Department could only afford to buy back a small percentage of harvested eggs for incubation and release (Pritchard 1982).

Fisheries bycatch: Leatherback are especially threatened by longline swordfish and tuna fisheries of the United States, Europe, Asia, and South America, shrimp trawl fisheries, gillnet fisheries, and pot fisheries throughout the world. Even with the use of larger Turtle Excluder Devices (TEDs) developed to exclude leatherbacks, the U.S. offshore commercial shrimp fishery captures an estimated 640 each year (NOAA/NMFS 2005). Eckert and Sarti (1997) reported that "mortality associated with the swordfish gillnet fisheries in Peru and Chile represents the single largest source of mortality for East Pacific leatherbacks". Gillnet fisheries in these countries may kill an estimated 2,000 leatherbacks annually (this estimate does not include animals taken in the longline fishery; Eckert and Sarti 1997). During 2000, an estimated 20,000 leatherbacks were caught and 1,000-3,200 killed as bycatch in Pacific longline fisheries (Lewison et al. 2004). The U.S. contribution to total pelagic longline bycatch is only around 2 percent of the global take, so most of the threat of capture exists outside the United States(Lewison et al. 2004). From 1978-1981, 126 turtles were reported captured in the Japanese tuna longline fishery in the Atlantic/Gulf of Mexico, of which around 25 percent were leatherbacks (Spotila et al. 1996).

Other threats: Adults historically were taken for meat and oil on nest beaches, and poaching still occurs in some locations. Erosion, development, and disturbance of nest beaches threatens nest success and reduces available nesting habitat (Pritchard 1982, NOAA/NMFS 2005). Where space is limited, females have been observed constructing nests on occupied sites and destroying eggs already present. Nesting beaches throughout their range are subject to human-related impacts including: coastal development, beach armoring, dredging, and beachfront lighting. Ingestion of floating plastic trash mistaken for jellyfish is often fatal to leatherbacks; vessel dumping of discarded fishing gear and petroleum products is also of concern (Bolten and Bjorndal 1992, NOAA/NMFS 2005).

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Major Threats

Threats to Leatherbacks vary in time and space, and in relative impact to populations. Threat categories affecting marine turtles, including Leatherbacks, were described by Wallace et al. (2011) as:

1) Fisheries bycatch: incidental capture of marine turtles in fishing gear targeting other species;

2) Take: direct utilization of turtles or eggs for human use (i.e. consumption, commercial products);

3) Coastal Development affecting critical turtle habitat: human-induced alteration of coastal environments due to construction, dredging, beach modification, etc.;

4) Pollution and Pathogens: marine pollution and debris that affect marine turtles (i.e. through ingestion or entanglement, disorientation caused by artificial lights), as well as impacts of pervasive pathogens (e.g. fibropapilloma virus) on turtle health;

5) Climate change: current and future impacts from climate change on marine turtles and their habitats (e.g. increasing sand temperatures on nesting beaches affecting hatchling sex ratios, sea level rise, storm frequency and intensity affecting nesting habitats, etc.).

The relative impacts of individual threats to all Leatherback subpopulations were assessed by Wallace et al. (2011). Fisheries bycatch was classified as the highest threat to Leatherbacks globally, followed by human consumption of Leatherback eggs, meat, or other products, and coastal development. Due to lack of information, pollution and pathogens was only scored as affecting three subpopulations and climate change was only scored for two subpopulations. Enhanced efforts to assess and reduce the impacts of these threats on Leatherbacks—and other marine turtle species—should be a high priority for future conservation efforts.

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Climate change is likely to affect Leatherback Turtles in at least three important ways (IUCN 2009):

(1) Increasing feminization:
Average global temperatures are predicted to increase by at least 2°C in the next 40 years due to climate change. This temperature increase could have serious consequences for Leatherbacks, as well as for other species whose sex is determined by embryonic temperature. The predicted outcome of this change (barring significant adaptation of the sex determination system or nesting behavior) is an increase in the number of females relative to males in Leatherback populations, which could threaten the stability of these populations. Increases in temperature have also been shown to lead to hatchling abnormalities and developmental and other health problems in young Leatherbacks (IUCN 2009).

(2) Beach erosion:

Ocean levels are thought to have risen at an average rate of 1.8 mm per year since 1961 and are predicted to rise even more rapidly in the future. Increases in storm frequency and severity have also been predicted. This is likely to lead to increased beach erosion and degradation, which could wash away turtle nests and decrease nesting habitat in the longer term. While some climate change adaptation measures, such as sea walls, help mitigate sea level rise impacts on human populations, their increased construction is likely to further reduce the availability of Leatherbacks’ nesting habitat in the future (IUCN 2009).

(3) Dispersal and food availability:

Ocean currents are important for both juvenile and adult Leatherbacks. Juveniles use them to aid dispersal following hatching and adults use them as navigational aids. Thus, changes in currents could have a major impact on Leatherback populations. Altered currents are also likely to affect the abundance and distribution of jellyfish and other Leatherback prey species. Although climate change impacts on ocean currents are likely, the nature of these changes, and hence their effects on Leatherbacks, remains uncertain (IUCN 2009).

There is some hope that Leatherbacks may be able to adapt behaviorally to the changing climate. While females are known to return to the same region--and perhaps even nesting beach--to nest each year, Leatherbacks are nevertheless among the most flexible turtle species in their nest site choice. Over time, the Leatherback's flexibility may allow them to modify their nesting site choices to select more favorable areas (in fact, northward extensions of both nesting and feeding areas have already been noted for this species). For this to be possible, however, potentially suitable beaches need to be available in more favorable areas. Coastal developments and pressures from humans have already rendered many possible sites unsuitable, and increasing sea wall development and beach erosion are likely to further reduce beach availability.

As is the case for many other vulnerable species, the ability of the Leatherback to adapt to climate change may be challenged by other threats it faces, including active harvesting by humans, accidental capture by fisheries, coastal development, and mistaken consumption by Leatherbacks of plastic debris. Such ongoing threats are likely to make the Leatherback less resilient to
additional pressures such as climate change.

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Several populations of leatherback turtles in the Pacific have plummeted in recent years, principally due to accidental capture in fisheries and the over-harvest of eggs (13). Other threats to leatherbacks worldwide include habitat loss, accidental capture in fisheries, boat strikes, and ingestion of discarded plastics, which leatherbacks mistake for jellyfish (14).
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Management

Management Requirements: Basic needs are to: monitor occurrences; enforce protective regulations; conduct educational programs regarding sea turtles, particularly in Mexico, South America, and Malaysia; enact beach lighting ordinances; keep traffic off beaches; remove nest predators (e.g., raccoons, canids, coatis) if needed.

Frazer (1992) emphasized the primary need for clean and productive marine and coastal environments; installation of turtle excluder devices in shrimp trawl nets and use of low pressure sodium lighting on beaches were suggested as appropriate sea turtle conservation technologies, whereas headstarting, captive breeding, and hatcheries were regarded as ineffective at best.

See NMFS (Federal Register, 19 December 1996, pp. 66933-66947) for recent amendments to regulations pertaining to the use of turtle excluder devices along the Gulf and Atlantic coasts of the southeastern U.S.

At Sandy Point National Wildlife Refuge, U.S. Virgin Islands, nest relocations and protection from poaching possibly have resulted in a doubling of the number of emerging hatchlings (Boulon et al. 1996).

See Chan (1989) for information on handling eggs and artificial incubation.

A recovery plan is available for marine turtles: see Marine Turtle Recovery Team (1984). For detailed information on management and recovery, see also the recovery plans for the St. Croix population (1981), U.S. Pacific populations (NMFS 1998), and South Florida population (USFWS 1998).

Management Research Needs: Determine sustainability of egg harvest. Information needed on ecology, demographics, and migratory movements. Determine nest site tenacity.

Biological Research Needs: Better information is needed on ecology, demographics, migratory movements, nest site tenacity, bycatch, survivorship rates, and the status of stocks throughout the range.

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Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: The Inter-American Convention for the Protection and Conservation of Sea Turtles (IAC) is the only treaty devoted exclusively to sea turtles and aims to "promote the protection, conservation and recovery of sea turtle populations and of the habitats on which they depend, based on the best available scientific evidence, taking into account the environmental, socioeconomic and cultural characteristics of the Parties." This treaty involves 21 nations, including the United Staes, in preserving sea turtles as an internationally shared resource (seaturtle.org 2003, C. Ryder, pers. comm.).

Critical Habitat has been designated at St. Croix, Virgin Islands; Santa Rosa N.P., Costa Rica; and sites in Mexico.

NMFS (Federal Register, 12 May 1995) established a leatherback conservation zone extending from Cape Canaveral to the Virginia-North Carolina border and including all inshore and offshore waters; this zone is subject to shrimping closures when high abundances of leatherbacks are documented. For example, on 20 December 2001, NOAA Fisheries issued a temporary rule that required shrimp trawlers operating in Atlantic waters from the shoreline out to 10 nautical miles between 28 degrees north latitude, approximately Melbourne, Florida and the Florida/ Georgia border, to use Turtle Excluder Devices (TEDs) with escape openings modified to exclude leatherback turtles. This emergency rule, effective through 14 January 2002, was based on a number of factors including the presence of an extraordinarily high number of leatherbacks stranded along northeast Florida beaches in November and early December. According to state authorities, 15 dead leatherbacks washed ashore from St. Johns through Brevard counties in shrimp zones 28 and 29 between November 4 and December 10, 2001 (NMFS 2000). TED programs have been initiated in several other countries as well.

Larger TEDs that are more effective in excluding larger hard-shelled and leatherback turtles are now required in certain areas during specified times. Use of TEDs with openings large enough to accommodate leatherbacks is required of U.S. shrimp trawlers in the Atlantic and Gulf of Mexico.

In 1989, a law was passed (Section 609 of U.S. Public Law 101-162) prohibiting U.S. importation of shrimp harvested in ways that are harmful to sea turtles; only nations certified by the Department of State as having a sea turtle protection program similar to that in the United States (i.e., requiring and enforcing TED use) may avoid this trade embargo. Time length of individual shrimp trawls is also limited to reduce drowning risk to trapped sea turtles, and fisheries observers are required on a certain percentage of U.S. vessels fishing the North Pacific, Atlantic, and Gulf of Mexico.

Nest beaches are protected in most parts of the species' range, but outside of U.S. jurisdiction law enforcement is often insufficient (Showalter 2003).

Needs: Protection needs include the following: protect all existing occurrences (increase survival of eggs and hatchlings); reduce adult mortality, such as by reducing incidental catch (mandatory use of TEDs, elimination of drift nets); restrict dumping of plastics and other debris and pollutants.

See also recovery plans and Spotila et al. (1996).

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Conservation Actions

Conservation Actions

Leatherbacks are protected under various Conventions, national and international laws, treaties, agreements, and memoranda of understanding. A partial list of international conservation instruments that provide legislative protection for Leatherbacks are: Annex II of the SPAW Protocol to the Cartagena Convention (a protocol concerning specially protected areas and wildlife); the Leatherback’s inclusion in Appendix I of CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora); and Appendices I and II of the Convention on Migratory Species (CMS); the Inter-American Convention for the Protection and Conservation of Sea Turtles (IAC); the Memorandum of Understanding on the Conservation and Management of Marine Turtles and their Habitats of the Indian Ocean and South-East Asia (IOSEA); the Memorandum of Understanding on ASEAN Sea Turtle Conservation and Protection; and the Memorandum of Understanding Concerning Conservation Measures for Marine Turtles of the Atlantic Coast of Africa.

Long-term efforts to reduce or eliminate threats to Leatherbacks on nesting beaches have been successful in many places (e.g. Dutton et al. 2005, Chacón-Chaverri and Eckert 2007, Santidrián Tomillo et al. 2007, Sarti Martínez et al. 2007) but not all places (e.g. Chan and Liew 1996). Reducing Leatherback bycatch has become a primary focus for many conservation projects around the world, and some mitigation efforts are showing promise (Watson et al. 2005; Gilman et al. 2006, 2011). However, threats to Leatherbacks—bycatch mortality and egg consumption, in particular—persist, and in some places, continue to hinder population recovery (Alfaro-Shigueto et al. 2011, 2012; Tapilatu et al. 2013; Wallace et al. 2013). For depleted Leatherback populations to recover, the most prevalent and impactful threats must be reduced wherever they occur, whether on nesting beaches or in feeding, migratory, or other habitats (Bellagio Report 2007; Wallace et al. 2011, 2013); a holistic approach that addresses threats at all life history stages needs to be implemented (Dutton and Squires 2011). Therefore, current conservation efforts, legal protections, and resources supporting those mechanisms must be maintained—and augmented, wherever possible—to reverse population declines and sustain stable and increasing population trends among Leatherback subpopulations. Regional and local efforts to protect Leatherbacks, their offspring, and their habitats should be designed to address threats at appropriate scales, and implemented with participation of appropriate stakeholders.

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Populations of leatherback turtles (Dermochelys coriacea) in the eastern Pacific have declined by more than 90% during the past two decades, primarily due to unsustainable egg harvest and fisheries bycatch mortality (Shillinger et al. 2008 and references therein). To better understand habitat use and migration patterns of these turtles, Shillinger et al. (2008) undertook a multi-year satellite tracking study and identified a very consistent migration corridor. They suggest that their data will facilitate the identification of potential areas for mitigating fisheries bycatch interactions in the eastern South Pacific.

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Conservation

International trade in leatherback turtles and products is banned under Appendix I of the Convention on International Trade in Endangered Species (CITES), and the turtle is protected throughout most of its range (1). Many conservation projects have been set up on nesting beaches, with specific management protocols tailored to each location. The attachment of Turtle Excluding Devices (TEDs) to shrimp nets can help prevent the accidental capture of turtles (bycatch) and the US government has recently set up Leatherback Conservation Areas in the north Pacific that are off-limits to long-line fisheries during certain times of the year. Despite encouraging signs of stable or increasing populations in the Atlantic, conservationists are concerned that extinction of other populations is only a matter of time. Recent estimates have suggested there are no more than 2000 breeding females in the eastern Pacific, making this population extremely vulnerable (12).
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Relevance to Humans and Ecosystems

Benefits

Economic Uses

Comments: Eggs are harvested for human consumption in many areas. Adults generally are not exploited for food or commercial products, though sometimes the oil is rendered and used for caulking boats and for medicinal purposes (Van Meter 1983). Suarez and Starbird (1996) documented subsistence hunting of leatherbacks in Indonesia.

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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.

Negative Impacts: injures humans (poisonous )

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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.

Positive Impacts: food ; body parts are source of valuable material

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Wikipedia

Leatherback sea turtle

The leatherback sea turtle (Dermochelys coriacea), sometimes called the lute turtle, is the largest of all living turtles (as well as the largest extant sea turtle) and is the fourth largest modern reptile behind three crocodilians.[5][6] It is the only living species in the genus Dermochelys. It can easily be differentiated from other modern sea turtles by its lack of a bony shell. Instead, its carapace is covered by skin and oily flesh. Dermochelys coriacea is the only extant member of the family Dermochelyidae.

Anatomy and physiology[edit source | edit]

Leatherback turtles have the most hydrodynamic body design of any sea turtle, with a large, teardrop-shaped body. A large pair of front flippers power the turtles through the water. Like other sea turtles, the leatherback has flattened forelimbs adapted for swimming in the open ocean. Claws are absent from both pairs of flippers. The leatherback's flippers are the largest in proportion to its body among extant sea turtles. Leatherback's front flippers can grow up to 2.7 metres (8.9 ft) in large specimens, the largest flippers (even in comparison to its body) of any sea turtle.

Leatherback turtle covering her eggs, Turtle Beach, Tobago

The leatherback has several characteristics that distinguish it from other sea turtles. Its most notable feature is the lack of a bony carapace. Instead of scutes, it has thick, leathery skin with embedded minuscule osteoderms. Seven distinct ridges rise from the carapace, crossing from the anterior to posterior margin of the turtle's back. Leatherbacks are unique among reptiles in that their scales lack β-keratin. The entire turtle's dorsal surface is colored dark grey to black, with a scattering of white blotches and spots. Demonstrating countershading, the turtle's underside is lightly colored.[7][8]

Instead of teeth, the leatherback turtle has points on the tomium of its upper lip, with backwards spines in its throat to help it swallow food and to stop its prey escaping once caught. The teeth are not used for mastication.

Dermochelys coriacea adults average 1–1.75 m (3.3–5.74 ft) in carapace length, 1.83–2.2 m (6.0–7.2 ft) in total length and weigh 250 to 700 kg (550 to 1,500 lb).[7][9] In the Caribbean, the mean size of adults was reported at 384 kg (850 lb) in weight and 1.55 m (5.1 ft) along the curve of the carapace.[10] The largest ever found, however, was over 3 metres (9.8 ft) from head to tail, including a carapace length of over 2.2 metres (7.2 ft), and weighed 916 kilograms (2,020 lb).[11] That specimen was found on a beach on the west coast of Wales.[12] The leatherback turtle is scarcely larger than any other sea turtle upon hatching, as they average 61.3 mm (2.41 in) in carapace length and weigh around 46 g (1.6 oz) when freshly hatched.[10]

Dermochelys coriacea exhibits a suite of anatomical characteristics believed to be associated with a life in cold waters, including an extensive covering of brown adipose tissue,[13] temperature independent swimming muscles,[14] counter-current heat exchangers between the large front flippers and the core body, as well as an extensive network of counter-current heat exchangers surrounding the trachea.[15]

Physiology[edit source | edit]

Leatherbacks have been viewed as unique among reptiles for their ability to maintain high body temperatures using metabolically generated heat, or endothermy. Initial studies on leatherback metabolic rates found leatherbacks had resting metabolisms around three times higher than expected for a reptile of their size.[16] However, recent studies using reptile representatives encompassing all the size ranges leatherbacks pass through during ontogeny discovered the resting metabolic rate of a large Dermochelys coriacea is not significantly different from predicted results based on allometry.[17]

Rather than use a high resting metabolism, leatherbacks appear to take advantages of a high activity rate. Studies on wild D.coriacea discovered individuals may spend as little as 0.1% of the day resting.[18] This constant swimming creates muscle-derived heat. Coupled with their counter-current heat exchangers, insulating fat covering and large size, leatherbacks are able to maintain high temperature differentials compared to the surrounding water. Adult leatherbacks have been found with core body temperatures that were 18 °C (32 °F) above the water they were swimming in.[19]

Leatherback turtles are one of the deepest diving marine animals. Individuals have been recorded diving to depths as great as 1,280 metres (4,200 ft).[20][21] Typical dive durations are between 3 and 8 minutes, with dives of 30–70 minutes occurring infrequently.[22]

They are also the fastest-moving reptiles. The 1992 edition of the Guinness Book of World Records lists the leatherback turtle moving at 35.28 kilometres per hour (21.92 mph) in the water.[23][24] More typically, they swim at 0.5–2.8 metres per second (1.1–6.3 mph).[25]

Distribution[edit source | edit]

The leatherback turtle is a species with a cosmopolitan global range. Of all the extant sea turtle species, D. coriacea has the widest distribution, reaching as far north as Alaska and Norway and as far south as the Cape of Good Hope in Africa and the southernmost tip of New Zealand.[7] The leatherback is found in all tropical and subtropical oceans, and its range extends well into the Arctic Circle.[26]

There are three major, genetically distinct populations, in the Atlantic, eastern Pacific and western Pacific Oceans.[5][27]

While nesting beaches have been identified in the region, leatherback populations in the Indian Ocean remain generally unassessed and unevaluated.[28]

D. coriacea distribution - yellow circles represent minor nesting locations, red circles are known major nesting sites

Recent estimates of global nesting populations are that 26,000 to 43,000 females nest annually, which is a dramatic decline from the 115,000 estimated in 1980.[29] These declining numbers have energized efforts to rebuild the species, which currently is critically endangered.[29]

Atlantic subpopulation[edit source | edit]

The leatherback turtle population in the Atlantic Ocean ranges across the entire region. They range as far north as the North Sea and to the Cape of Good Hope in the south. Unlike other sea turtles, leatherback feeding areas are in colder waters, where there is an abundance of their jellyfish prey, which broadens their range. However, only a few beaches on both sides of the Atlantic provide nesting sites.[30]

Off the Atlantic coast of Canada, leatherback turtles feed in the Gulf of Saint Lawrence near Quebec and as far north as Newfoundland and Labrador.[31] The most significant Atlantic nesting sites are in Suriname, Guyana, French Guiana in South America, and Trinidad and Tobago in the Caribbean, and Gabon in Central Africa. The beaches of Mayumba National Park in Mayumba, Gabon host the largest nesting population on the African continent and possibly worldwide, with nearly 30,000 turtles visiting its beaches each year between October and April.[27][32][32] Off the northeastern coast of the South American continent, a few select beaches between French Guiana and Suriname are primary nesting sites of several species of sea turtles, the majority being leatherbacks.[33] A few hundred nest annually on the eastern coast of Florida.[6] In Costa Rica, the beaches of Gandoca and Parismina provide nesting grounds.[28][34]

Pacific subpopulation[edit source | edit]

Pacific leatherbacks divide into two populations. One population nests on beaches in Papua, Indonesia and the Solomon Islands and forage across the Pacific in the Northern Hemisphere, along the coasts of California, Oregon, and Washington in North America. The eastern Pacific population forages in the Southern Hemisphere, in waters along the western coast of South America, nesting in Mexico, Panama, El Salvador, Nicaragua, and Costa Rica.[27][35]

The continental United States offers two major Pacific leatherback feeding areas. One well-studied area is just off the northwestern coast near the mouth of the Columbia River. The other American area is located in the state of California.[35] Further north, off the Pacific coast of Canada, leatherbacks visit the beaches of British Columbia.[31]

Estimates by the WWF suggest there may only be 2,300 adult females of the Pacific leatherback remaining in the world, making it the most endangered marine turtle subpopulation.[36]

South China Sea subpopulation[edit source | edit]

A third possible Pacific subpopulation has been proposed, those that nest in Malaysia. This sub-population, however, has effectively been eradicated. The beach of Rantau Abang in Terengganu, Malaysia, once had the largest nesting population in the world, hosting 10,000 nests per year. The major cause for the decline was egg consumption by humans. Conservation efforts initiated in the 1960s were ineffective because they involved excavating and incubating eggs at artificial sites which inadvertently exposed the eggs to high temperatures. It only became known in the 1980s that sea turtles undergo temperature-dependent sex determination; it is suspected that nearly all the artificially incubated hatchlings were female.[37] In 2008, two turtles nested at Rantau Abang, and unfortunately the eggs were infertile.

Indian Ocean subpopulation[edit source | edit]

While little research has been done on Dermochelys populations in the Indian Ocean, nesting populations are known from Sri Lanka and the Nicobar Islands. These turtles are proposed to form a separate, genetically distinct Indian Ocean subpopulation.[28]

Ecology and life history[edit source | edit]

Leatherback turtle at Sandy Point National Wildlife Reserve
A leatherback turtle. Photo taken on Montjoly beach (French Guiana)

Habitat[edit source | edit]

Leatherback turtles can be found primarily in the open ocean. Scientists tracked a leatherback turtle that swam from Indonesia to the U.S. in an epic 20,000 km (12,000 mi) foraging journey over a period of 647 days.[7][38] Leatherbacks follow their jellyfish prey throughout the day, resulting in turtles "preferring" deeper water in the daytime, and shallower water at night (when the jellyfish rise up the water column).[18] This hunting strategy often places turtles in very frigid waters. One individual was found actively hunting in waters that had a surface temperature of 0.4 °C (32.7 °F).[39]

Its favored breeding beaches are mainland sites facing deep water and they seem to avoid those sites protected by coral reefs.[40]

Feeding[edit source | edit]

Adult D. coriacea turtles subsist almost entirely on jellyfish.[7] Due to their obligate feeding nature, leatherback turtles help control jellyfish populations.[5] Leatherbacks also feed on other soft-bodied organisms, such as tunicates and cephalopods.[41]

Pacific leatherbacks migrate about 9,700 kilometres (6,000 mi) across the Pacific from their nesting sites in Indonesia to eat California jellyfish. One cause for their endangered state is plastic bags floating in the ocean. Pacific leatherback sea turtles mistake these plastic bags for jellyfish; an estimated one third of adult leatherbacks have ingested plastic.[42] Plastic enters the oceans along the west coast of urban areas, where leatherbacks forage; with Californians using upwards of 19 billion plastic bags every year.[43] Several species of sea turtles commonly ingest plastic marine debris, and even small quantities of debris can kill sea turtles by obstructing their digestive tracts.[44] Nutrient dilution, which occurs when plastics displace food in the gut, affects the nutrient gain and consequently the growth of sea turtles.[45] Ingestion of marine debris and slowed nutrient gain leads to increased time for sexual maturation that may affect future reproductive behaviors.[46] These turtles have the highest risk of encountering and ingesting plastic bags offshore of San Francisco Bay, the Columbia River mouth, and Puget Sound.

Lifespan[edit source | edit]

Very little is known of the species' lifespan. Some reports claim "30 years or more"[47] while others state "80 years or more".[48]

Death and decomposition[edit source | edit]

Dead leatherbacks that wash ashore are micro-ecosystems while decomposing. In 1996, a drowned carcass held sarcophagid and calliphorid flies after being picked open by a pair of Coragyps atratus vultures. Infestation by carrion-eating beetles of the families Scarabaeidae, Carabidae, and Tenebrionidae soon followed. After days of decomposition, beetles from the families Histeridae and Staphylinidae and anthomyiid flies invaded the corpse as well. Organisms from more than a dozen families took part in consuming the carcass.[49]

Life history[edit source | edit]

Hatchlings leave their nest
A hatchling running to the sea

Like all sea turtles, leatherbacks start as hatchlings, climbing out of the sands of their nesting beaches. Leatherback turtles face many predators in their early life. Eggs may be predated by a diversity of coastal predators, including ghost crabs, monitor lizards, raccoons, coatis, dogs, coyotes, genets, mongooses and shorebirds ranging from small plovers to large gulls. Many of the same predators will try to feed on tiny baby turtles as they try to get to the ocean, as well as frigatebirds and varied raptors. Once in the ocean, young leatherbacks still face predation from cephalopods, requiem sharks and various large fish. Despite their lack of a hard shell, the huge adult faces fewer serious predators, though it is occasionally overwhelmed and preyed on by very large marine predators such as orcas, great white sharks and tiger sharks. Nesting females have been preyed upon by jaguars in the American tropics.[50][51][52] Apparently, the adult leatherback aggressively defends itself at sea from predators. A medium-sized adult was observed chasing a shark that had attempted to bite it and then turned its aggression and attacked the boat containing the humans observing the prior interaction.[53] Dermochelys juveniles spend more of their time in tropical waters than do adults.[41]

Adults are prone to long-distance migration. Migration occurs between the cold waters where mature leatherbacks feed, to the tropical and subtropical beaches in the regions where they hatch. In the Atlantic, females tagged in French Guiana have been recaptured on the other side of the ocean in Morocco and Spain.[33]

Mating takes place at sea. Males never leave the water once they enter it, unlike females which nest on land. After encountering a female (who possibly exudes a pheromone to signal her reproductive status), the male uses head movements, nuzzling, biting, or flipper movements to determine her receptiveness. Females mate every two to three years. However, leatherbacks can breed annually. Fertilization is internal, and multiple males usually mate with a single female. This polyandry does not provide the offspring with any special advantages.[54]

While other sea turtle species almost always return to their hatching beach, leatherbacks may choose another beach within the region. They choose beaches with soft sand because their softer shells and plastrons are easily damaged by hard rocks. Nesting beaches also have shallower approach angles from the sea. This is a vulnerability for the turtles because such beaches easily erode. They nest at night when the risk of predation is lowest. As leatherback turtles spend the vast majority of their lives in the ocean, their eyes are not well adapted to night vision on land. The typical nesting environment includes a dark forested area adjacent to the beach. The contrast between this dark forest and the brighter, moonlit ocean provides directionality for the females. They nest towards the dark and then return to the ocean and the light.

Females excavate a nest above the high-tide line with their flippers. One female may lay as many as nine clutches in one breeding season. About nine days pass between nesting events. Average clutch size is around 110 eggs, 85% of which are viable.[7] After laying, the female carefully back-fills the nest, disguising it from predators with a scattering of sand.[41][55]

Cleavage of the cell begins within hours of fertilization, but development is suspended during the gastrulation period of movements and infoldings of embryonic cells, while the eggs are being laid. Development then resumes, but embryos remain extremely susceptible to movement-induced mortality until the membranes fully develop after incubating for 20 to 25 days. The structural differentiation of body and organs (organogenesis) soon follows. The eggs hatch in about sixty to seventy days. As with other reptiles, the nest's ambient temperature determines the sex of the hatchings. After nightfall, the hatchings dig to the surface and walk to the sea.[56][57]

Leatherback nesting seasons vary by location; it occurs from February to July in Parismina, Costa Rica.[34] Farther east in French Guiana, nesting is from March to August.[33] Atlantic leatherbacks nest between February and July from South Carolina in the United States to the United States Virgin Islands in the Caribbean and to Suriname and Guyana.[citation needed]

Taxonomy and evolution[edit source | edit]

Taxonomy[edit source | edit]

Dermochelys coriacea is the only species in genus Dermochelys. The genus, in turn, contains the only extant member of the family Dermochelyidae.[58]

Domenico Agostino Vandelli named the species first in 1761 as Testudo coriacea after an animal captured at Ostia and donated to the University of Padua by Pope Clement XIII.[59] In 1816, French zoologist Henri Blainville coined the term Dermochelys. The leatherback was then reclassified as Dermochelys coriacea.[60] In 1843, the zoologist Leopold Fitzinger put the genus in its own family, Dermochelyidae.[61] In 1884, the American naturalist Samuel Garman described the species as Sphargis coriacea schlegelii.[62] The two were then united in D. coriacea, with each given subspecies status as D. coriacea coriacea and D. coriacea schlegelii. The subspecies were later labeled invalid synonyms of D. coriacea.[63][64]

The turtle's common name comes from the leathery texture and appearance of its carapace. Older names include "leathery turtle"[6] and "trunk turtle".[65]

Evolution[edit source | edit]

Relatives of modern leatherback turtles have existed in some form since the first true sea turtles evolved over 110 million years ago during the Cretaceous period. The dermochelyids are close relatives of the family Cheloniidae, which contains the other six extant sea turtle species. However, their sister taxon is the extinct family Protostegidae which included other species not having a hard carapace.[66][67]

Importance to humans[edit source | edit]

People around the world still harvest sea turtle eggs. Asian exploitation of turtle nests has been cited as the most significant factor for the species' global population decline. In Southeast Asia, egg harvesting in countries such as Thailand and Malaysia has led to a near-total collapse of local nesting populations.[68] In Malaysia, where the turtle is practically locally extinct, the eggs are considered a delicacy.[69] In the Caribbean, some cultures consider the eggs to be aphrodisiacs.[68]

They are also a major jellyfish predator[70][71] which helps keep jellyfish populations in check.

Conservation[edit source | edit]

Adult leatherback turtles have few natural predators once they mature; they are most vulnerable to predation in their early life stages. Birds, small mammals, and other opportunists dig up the nests of turtles and consume eggs. Shorebirds and crustaceans prey on the hatchings scrambling for the sea. Once they enter the water, they become prey to predatory fish and cephalopods. Very few survive to adulthood.

Leatherbacks have slightly fewer human-related threats than other sea turtle species. Their flesh contains too much oil and fat, reducing the demand. However, human activity still endangers leatherback turtles in direct and indirect ways. Directly, a few are caught for their meat by subsistence fisheries. Nests are raided by humans in places such as Southeast Asia.[68]

Many human activities indirectly harm Dermochelys populations. As a pelagic species, D. coriacea is occasionally caught as bycatch. As the largest living sea turtles, turtle excluder devices can be ineffective with mature adults. A reported average of 1,500 mature females were accidentally caught annually in the 1990s.[68] Pollution, both chemical and physical, can also be fatal. Many turtles die from malabsorption and intestinal blockage following the ingestion of balloons and plastic bags which resemble their jellyfish prey.[7] Chemical pollution also has an adverse effect on Dermochelys. A high level of phthalates has been measured in their eggs' yolks.[68]

Global initiatives[edit source | edit]

D. coriacea is listed on Appendix I of CITES, which makes export/import of this species (including parts) illegal.

Conserving Pacific and Eastern Atlantic populations was included among the top ten issues in turtle conservation in the first State of the World's Sea Turtles report published in 2006. The report noted significant declines in the Mexican, Costa Rican and Malaysian populations. The eastern Atlantic nesting population was threatened by increased fishing pressures from eastern South American countries.[72]

The Leatherback Trust was founded specifically to conserve sea turtles, specifically its namesake. The foundation established a sanctuary in Costa Rica, the Parque Marino Las Baulas.[73]

National and local initiatives[edit source | edit]

The leatherback sea turtle is subject to differing conservation laws in various countries.

The United States listed it as an endangered species on 2 June 1970. The passing of the Endangered Species Act three years later ratified its status.[74] In 2012 the National Oceanic and Atmospheric Administration designated 41,914 square miles of Pacific Ocean along California, Oregon and Washington as "critical habitat."[75] In Canada, the Species At Risk Act made it illegal to exploit the species in Canadian waters. The Committee on the Status of Endangered Wildlife in Canada classified it as endangered.[31] Ireland and Wales initiated a joint leatherback conservation effort between Swansea University and University College Cork. Funded by the European Regional Development Fund, the Irish Sea Leatherback Turtle Project focuses on research such as tagging and satellite tracking of individuals.[76]

Earthwatch Institute, a global non-profit that teams volunteers with scientists to conduct important environmental research, launched a program called "Trinidad's Leatherback Sea Turtles." This program strives to help save the world's largest turtle from extinction in Matura Beach, Trinidad, as volunteers work side-by-side with leading scientists and a local conservation group, Nature Seekers. This tropical island off the coast of Venezuela is known for its vibrant ethnic diversity and rich cultural events. It is also the site of one of the most important nesting beaches for endangered leatherback turtles, enormous reptiles that can weigh a ton and dive deeper than many whales. Each year, more than 2,000 female leatherbacks haul themselves onto Matura Beach to lay their eggs. With leatherback populations declining more quickly than any other large animal in modern history, each turtle is precious. On this research project, Dr. Dennis Sammy of Nature Seekers and Dr. Scott Eckert of Wider Caribbean Sea Turtle Conservation Network work alongside a team of volunteers to help prevent extinction of leatherback sea turtles.[77]

Several Caribbean countries started conservation programs, such as The St. Kitts Sea Turtle Monitoring Network, focused on using ecotourism to highlight the leatherback's plight. On the Atlantic coast of Costa Rica, the village of Parismina has one such initiative. Parismina is an isolated sandbar where a large number of leatherbacks lay eggs, but poachers abound. Since 1998, the village has been assisting turtles with a hatchery program. The Parismina Social Club is a charitable organization backed by American tourists and expatriates, which collects donations to fund beach patrols.[78] [79] Mayumba National Park in Gabon, Central Africa was created to protect Africa's most important nesting beach. More than 30,000 turtles nest on Mayumba's beaches between September and April each year.[32]

In mid-2007, the Malaysian Fisheries Department revealed a plan to clone leatherback turtles to replenish the country's rapidly declining population. Some conservation biologists, however, are skeptical of the proposed plan because cloning has only succeeded on mammals such as dogs, sheep, cats, and cattle, and uncertainties persist about cloned animals' health and life spans.[80] Leatherbacks used to nest in the thousands on Malaysian beaches, including those at Terengganu, where more than 3,000 females nested in the late 1960s.[81] The last official count of nesting leatherback females on that beach was recorded to be a mere two females in 1993.[27]

In Brazil, reproduction of the leatherback turtle is being assisted by the IBAMA's "projeto TAMAR" (TAMAR project), which works to protect nests and prevent accidental kills by fishing boats. The last official count of nesting leatherback females in Brazil yielded only seven females.[82] In January 2010, one female at Pontal do Paraná laid hundreds of eggs. Since leatherback sea turtles had been reported to nest only at Espirito Santo's shore, but never in the state of Paraná, this unusual act brought much attention to the area, biologists have been protecting the nests and checking their eggs' temperature, although it might be that none of the eggs are fertile.[83][dated info]

Australia's Environment Protection and Biodiversity Conservation Act 1999, lists D. coriacea as Vulnerable, while Queensland's Nature Conservation Act 1992 lists it as Endangered.

See also[edit source | edit]

Bibliography[edit source | edit]

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Names and Taxonomy

Taxonomy

Comments: Two described subspecies, D. c. coriacea (Atlantic Ocean) and D. c. schlegelii (Pacific and Indian oceans), seem to be poorly differentiated and currently are not recognized (Pritchard 1980). Should the populations in the Pacific prove to be a valid subspecies, the proper name would be D. c. angusta (Pritchard and Trebbau 1984). Brongersma (1996) determined that the source of the type material for the name schlegelii likely is Japan and not Guaymas, Mexico.

Crother et al. (2008) has returned to the use of "sea turtles" (rather than "seaturtles") as part of the standard English name for marine turtles. The combined name has not been used recently in the literature.

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