Dermochelys coriacea (Leatherback turtle)

Leerrug-seeskilpad [Afrikaans]

Life > Eukaryotes > Opisthokonta > Metazoa (animals) > Bilateria > Deuterostomia > Chordata > Craniata > Vertebrata (vertebrates)  > Gnathostomata (jawed vertebrates) > Teleostomi (teleost fish) > Osteichthyes (bony fish) > Class: Sarcopterygii (lobe-finned fish) > Stegocephalia (terrestrial vertebrates) > Tetrapoda (four-legged vertebrates) > Reptiliomorpha > Amniota > Reptilia (reptiles) > Anapsida > Chelonia (turtles and tortoises) > Cryptodira > Family: Dermochelyidae > Genus: Dermochelys

   
   

Identification

A very distinctive species with its spindle-shaped body and leathery, unscaled, keeled carapace (the protective covering on top of the animal). It is the largest species of chelonian (the group containing the turtles, terrapins and tortoises) in the world and one of the largest living reptiles; it is exceeded in size only by a few large species of crocodile. The largest individual yet recorded was 2.56 m long and weighed 916 kg.

Distribution and habitat

The Leatherback turtle is pelagic, living in the open sea, and is found in oceans worldwide. Although living in the surface waters most of the time, these turtles are also able to dive to depths of over 900 m. Unlike most other reptiles, it is endothermic (warm-blooded), thus being able to generate internal heat to keep its body warmer than its surroundings. This capability, along with the insulation provided by a protective thick and oily skin, has resulted in the Leatherback turtle being superbly adapted to cold water conditions. As a result, it occurs not only in tropical and subtropical seas but also penetrates into the cool seas such as into the Gulf of Alaska and around Scandinavia.

Life cycle

  • A female comes ashore on beaches at night, digs a hole in the sand above the high water mark, lays 46-160 eggs, covers them up and returns to the sea.
  • She lays 4-7 clutches in a season, 9-10 days separating each clutch.
  • In South Africa, leatherbacks breed along the coast in northern KwaZulu-Natal and egg laying is from late October to late January.
  •  After an incubation period of 50-78 days (depending on temperature and humidity), the hatchlings emerge, dig out of their nest, and make their way down to the sea. Hatching takes place from late December to early April in South Africa.
  • They reach sexual maturity after 13-14 years, by which time their carapace length has reached about 1.25 m. They can live for 30 years or more.

Food

The Leatherback turtle feeds mainly on jellyfish but also on other surface-dwelling soft-bodied invertebrates, including pyrosomes (Davenport and Balazs 1991) and cephalopods.

Ecological interactions

  • Eggs are eaten by a variety of animals including monitor lizards (Varanus leguwaan in Afrikaans), monkeys and mongooses. Harvesting of eggs by people has caused drastic declines in populations.
  • Hatchlings are exposed to extensive predation in their journey from the nest into the sea, being attacked by various predatory birds and mammals. Once in the water, they are caught by seabirds (e.g. frigatebirds, gulls) and by carnivorous fishes and squids.
  • In the sea, both juveniles and adults are attacked by sharks and adults can be eaten by killer whales (Orcinus orca).

Status

The World leatherback turtle population dropped from about 115 000 adult females in 1982 to about 25 000 in 1996, constituting a 78% reduction in numbers. This decrease has been caused by excessive harvesting of eggs, killing of adult females on beaches to obtain oil or for eating, entanglement of adults in fishing nets, and capture of adults on long-line hooks. They also die quite frequently from consuming plastic packets and bottles floating in the sea, which they seem to mistake for jellyfish. This serious situation for leatherbacks is being addressed through: (1) legislation prohibiting egg collecting and killing of females; (2) CITES regulations that prohibit international trade in all sea turtle products; and (3) the creation of coastal reserves in breeding areas. The capture and death of these turtles through fishing practices has yet to be addressed adequately.

Links

Publications

  • Davenport J, Balazs GH. 1991. 'Fiery bodies' - are pyrosomas an important component of the diet of leatherback turtles? British Herpetological Society Bulletin 37: 33-38.

 


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