Leatherback turtle hatchling. Photo:Col Limpus EHP
Common name: leatherback turtle, leathery turtle
Scientific name: Dermochelys coriacea
Conservation status: This species is listed as Endangered in Queensland (Nature Conservation Act 1992) and Vulnerable nationally (Environment Protection and Biodiversity Conservation Act 1999). It is ranked as a critical priority under the Department of Environment and Heritage Protection Back on Track species prioritisation framework.
The leatherback turtle is a very large turtle and can grow to a length of 3 m. It is usually a uniform dark brown or black above, sometimes with paler marbling or with longitudinal rows of small, fine dots and usually with pale white, pink or cream spots and blotches on the sides. The throat and lower sides of neck are white, pale cream or pink mottled and blotched with dark brown or black and whitish or pinkish-white below. The hatchlings are finely beaded in appearance. The adult shell is covered by a thick, smooth, leathery skin, often pitted and pock-marked in older specimens. A series of seven prominent longitudinal ridges occur on the carapace (including the outer lateral pair) and four ridges along the plastron.
Habitat and distribution
An adult leatherback turtle. Photo: Col Limpus EHP
The leatherback turtle has the widest distribution of any marine turtle, occurring from the North Sea and Gulf of Alaska in the Northern Hemisphere, to Chile and New Zealand in the Southern Hemisphere. Leatherback turtles occur in tropical and temperate waters of Australia. Large numbers of leatherback turtles feed off the southern Queensland and New South Wales coasts and off Western Australia's coast, south of Geraldton. They are less abundant in the tropical waters of the northern Australian continental shelf. The best place to see leatherback turtles is Wreck Rock, north of Bundaberg in Queensland. This species has been recorded feeding in coastal waters of all the Australian states.
Most sightings are along the more heavily populated eastern seaboard of Australia where large adults are found year round in larger bays, estuaries and rivers. The frequency of sightings suggests that the species actively seeks out temperate feeding grounds, rather than simply straying to the south.
Life history and behaviour
Most leatherback turtles live in Australian waters but migrate to breed in neighbouring countries, particularly in Java and along the northern coast of Irian Jaya, Papua New Guinea and the Solomon Islands.
No large rookeries have been recorded in Australia. Scattered nesting occurs along the southern Queensland coast from Bundaberg to Round Hill Head and along the coast of Arnhem Land from Coburg Peninsula to Maningrida, including Croker Island. Breeding in Australia occurs mostly during December and January. Females lay on average about 83 large eggs and 47 small yolkless eggs.
Diet: The leatherback turtle is carnivorous and feeds mainly in the openocean on jellyfish and other soft-bodied invertebrates. Many casual observers have seen these turtles feeding on unidentified jellyfishes (apparently Catostylus mosaicus) and on bluebottles or Portuguese Man'o'War Physalia utriculus along the coast of New South Wales (Cogger 1994).
All marine turtle species are experiencing serious threats to their survival. The main threats are pollution and changes to important turtle habitats, especially coral reefs, seagrass beds, mangrove forests and nesting beaches. Other threats include accidental drowning in fishing gear and over-harvesting of turtles and eggs. Adults have been washed up on beaches in Sydney, New South Wales, after having drowned in shark nets.
- To conserve current populations it is imperative that major existing feeding and nesting sites are protected so that urban and industrial development can no longer threaten them;
- The control of feral animals and domestic dogs is essential at nesting sites along Queensland's coast to protect eggs from predation;
- Increase public awareness about the effect of light sources around nesting sites and promote the use of alternative lighting and protection of nesting sites to local councils;
- Encourage traditional hunters to comply with harvesting conditions;
- Fishing activities need to be monitored, in particular the use of Turtle Excluder Devices (TEDs) and the need for commercial fishers to check longlines, gillnets and lobster/crab pots frequently to disentangle any turtles caught accidentally.
What can you do to help this species
You can help this species by:
- remembering that rubbish you throw away can find its way to the sea, where turtles can mistake things such as plastic bags for jellyfish. Plastic swallowed by mistake can cause blockages of the stomach and intestines of marine animals such as turtles;
- being on the lookout to avoid turtles when out in your boat. Many turtles are struck by propellers of speeding boats and this can cause injury and death;
- following the regulations relating to Personal Water Craft (jet skis, waveriders and waverunners), avoid travelling over seagrass beds and shallow water, staying in the navigation channel when travelling in conservation zones and operating off the plane in "turtle and dugong go-slow areas".
Environment Australia and Marine Turtle Recovery Team 2003. Recovery plan for marine turtles in Australia. Department of the Environment and Heritage, Canberra.
Department of the Environment and Heritage 2005. Protected marine species identification guide. Department of the Environment and Heritage, Canberra.
Cogger, HG 1994. Reptiles and Amphibians of Australia. Fifth Edition. Reed Books, Chatswood, NSW