Leatherback Sea Turtle

The Leatherback Sea Turtle (Dermochelys coriacea) is the biggest of all living turtles, reaching a length of over 2.7 m (8 ft) and weight of 900 kg (1,500 lb). The Leatherback Sea Turtle is found in all tropic and subtropic oceans. It is the only extant species in the genus Dermochelys and the family Dermochelyidae. This species has many unique features that distinguish it greatly from other sea turtles. Its shell lacks the bony scutes of other turtles, comprising mainly connective tissue. Its metabolic rate is about 3 times higher than one would expect for a reptile of its size; this, coupled with counter-current heat exchangers, the insulation provided by it's oily body and large size, allow it to maintain a body temperature as much as 18 °C (64 ºF) above that of the surrounding water. Some scientists hypothesize that the leatherback might have some capacity to generate its own body heat (like a mammal), although reptiles in general have been defined as ectotherms ("cold-blooded") and are thought not to be able to do so.

Physical characteristics

The Leatherback is the largest of all living turtles. It is very different from other turtles in both appearance and physiology. It has a smooth, blackish carapace with ridges running from head to tail. This shell is not made of bone plates, or scutes, as in most sea turtles, but of soft connective tissue. The carapace does not meet the plastron at a sharp angle like in other turtles, but a gentle curve, giving the animal a semi-cylindrical appearance.

The front flippers of the Leatherback turtle are much larger than those of other turtles, both in proportion and in absolute size. Those of adults can span 8.85 ft (270 cm) from tip to tip.

The beak of the Leatherback turtle is specially hooked to help it bite jellyfish and its throat has backward-facing barbs to help it swallow them. These throat hooks have caused Leatherbacks problems - they swallow plastic bags, which look like the gelatinous animals they prey on, and these indigestible bags then clog up their throats, preventing them feeding and eventually killing them. Dead leatherbacks have been found with plastic bags, pieces of hard plastic, and monofilament fishing line in their stomachs.

The world's biggest recorded Leatherback was washed ashore on Harlech beach, Gwynedd, in September 1988. It had drowned in fishing nets. It was one of the oldest recorded turtles, measuring almost nine feet (2.74 metres) in length and weighing 914 kg (2015 lb). Although popular media reported the turtle as 100 years old, aging techniques remain uncertain in leatherbacks, and their early growth rate is high, suggesting that even large adults may not be as ancient as other turtle species.

Diet

Leatherback turtles subsist on a diet of jellyfish, as well as other aquatic plants and animals. Giant leatherback turtles travel each year from the Caribbean to the UK and Europe, following the Gulf Stream in order to eat the jellyfish found there.

Range and habitat

The leatherback turtle is found throughout the Atlantic, Pacific and Indian oceans, from as far north as Labrador, Alaska and Norway to as far south as Chile, the Cape of Good Hope, Argentina, and the southern end of New Zealand.

In the summer months, Atlantic Leatherback turtles are most common from the Gulf of Maine in the north to the coast of central Florida in the south. They have been sighted as far north as the Gulf of St. Lawrence in Canada. Pacific Leatherback turtles are most often seen off the Hawaiian Islands, where they are known to congregate north of the archipelago.

The turtles prefer deep water but are most often seen within sight of land. In the summer they are often seen basking near the surface, particularly in the Long Island Sound, where they have been injured by collisions with boat propellers.

Threats and conservation

In the United States the Leatherback turtle has been classified as endangered across its range since 1970. It is also endangered in Canada. It is also listed on Appendix 1 of the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES). This makes it illegal to harm or kill the turtles.

Adult Leatherback turtles are large animals that are not particularly vulnerable to natural predators. Eggs and hatchlings are most vulnerable to predation of all kinds. Birds, dogs and other opportunists are known to dig up nests and consume eggs. New hatchlings are also vulnerable on their journey from nest to sea. Once they enter the water they become prey to many new predators and very few survive to adulthood.

Human activity endangers Leatherback turtles in many ways. Though it is forbidden, eggs are harvested by people in Puerto Rico, the surrounding islands, and possibly in other places. Development of beaches can disturb or destroy the particular kind of habitat that Leatherbacks need to nest, and the lights of development can cause hatchlings to move away from the sea rather than toward it. Human use of beaches can crush nests and hatchlings or bury eggs too deep for the hatchlings to emerge. Finally humans may disturb nesting females out of curiosity.

While adults are at sea their major threats are all from humans. Ingesting plastic, rubber, tar, oil, and other synthetic materials can kill an adult Leatherback or severely injure it. Many have been injured by colliding with boats, especially in shallow water. The equipment associated with commercial fishing, including lines, nets, ropes, and cables can entangle adult turtles and cause them to drown. Though "Turtle Exclusion Devices" are mandated on nets, they often fail to allow an animal the size of an adult Leatherback to escape. The US NOAA estimates that about 640 adult Leatherback turtles are killed each year by commercial fishing enterprise.

Nets are purposely set for other kinds of sea turtles in some areas of Puerto Rico. Though they are not intended for Leatherbacks, some are occasionally caught. Despite its illegality, the practice continues.

Morphology of the leatherback turtle skeleton

View 3D computed tomographic (CT) animations of the skeleton of a hatchling leatherback turtle, and learn more about its distinctive carapace, at Digimorph.org .

Taxonomy and Extinct Species

Family Dermochelyidae
- Genus Corsochelys
  - Corsochelys haliniches (extinct)
- Genus Mesodermochelys
  - Mesodermochelys undulatus (extinct)
- Genus Protosphargis
  - Protosphargis veronensis (extinct)
- Genus Eosphargis
  - Eosphargis gigas (extinct)
  - Eosphargis breineri (extinct)
- Genus Natemys
  - Natemys peruvianus (extinct)
- Genus Egyptemys
  - Egyptemys eocaenus (extinct)
  - Egyptemys oregonensis (extinct)
- Genus Cosmochelys
  - Cosmochelys dolloi (extinct)
- Genus Psephophorus
  - Psephophorus calvertensis (extinct)
  - Psephophorus polygonus (extinct)
  - Psephophorus rupeliensis (extinct)
  - Psephophorus terrypratchetti (extinct)
- Genus Dermochelys
  - Dermochelys coriacea (Modern Leatherback Sea Turtle)

References

Database entry includes justification for why this species is critically endangered
Wood R.C., Johnson-Gove J., Gaffney E.S. & Maley K.F. (1996) - Evolution and phylogeny of leatherback turtles (Dermochelyidae), with descriptions of new fossil taxa. Chel. Cons. Biol., 2(2): 266-286, Lunenburg.

External links

Parismina Turtle Commission
Audubon Observes Florida Sea-Turtles The great naturalist James Audubon observes the nesting behavior of Florida Sea-Turtles including the Leatherback Sea-Turtle (1832).
Kawana Campain paper: Leatherback Turtles, Dermochelys coriacea, Nesting in French Guiana, 1978-1995 with more sources
Irish Sea Leatherback Turtle Project

Sea turtles | Fauna of Guyana

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