Leatherback turtle  (Dermochelys coriacea)

The leatherback turtle is classified as Critically Endangered (CR) on the IUCN Red List (1). Listed on Appendix I of CITES (3) and Appendix I of the Convention on Migratory Species (CMS or the Bonn Convention) (4).

The leatherback turtle (Dermochelys coriacea) 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. The leatherback turtle is dark in colour, with white and pink spots. Females also have a characteristic 'pink spot' on the top of their heads (6). 

In addition to its huge size, the leatherback turtle can be easily identified by the seven narrow ridges running the length of the carapace, and by its particularly large front flippers (6).

With the widest distribution of all the marine turtles, the leatherback turtle is found throughout the world's oceans. It 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).

As strong swimmers that inhabit the open seas, adult leatherback turtles are truly pelagic. Mature females prefer to nest on sandy tropical beaches with deep-water approaches, although shallow water beaches are also used in certain regions (8). 

Very little is known about juvenile leatherback turtles in the ocean, although recently some small individuals have been found concentrated in waters off western Africa (8).

Adult leatherback turtles 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 organised 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 metres in search of prey (11). 

To nest, female leatherback turtles emerge at night on 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). Mature female leatherback turtles return to the same beach to nest every few years, but within one season a female can lay four to ten clutches (2). The sex of the hatchlings is influenced by incubation temperatures: hotter nests produce all females and cooler nests produce all males (12).

Perhaps the greatest threat to the leatherback turtle is global climate change. This is expected to affect this species through habitat loss, physiological changes and loss of prey (13). 

Average global temperatures are predicted to increase by at least 2 degrees Celsius in the next 40 years due to climate change. An increase in the temperature of the sand used for nesting could have serious consequences for the leatherback turtle, as gender of the hatchlings is determined by incubation temperature. The outcome of this is likely to be an increase in the number of females relative to males in populations. This could threaten the stability of leatherback turtle populations in the future. In addition, increases in temperature have also been shown to lead to hatchling abnormalities and other developmental problems in young leatherback turtles (13). 

Ocean levels are thought to have risen at an average rate of 1.8 millimetres per year since 1961. Ocean levels are predicted to rise even more rapidly in the future, while increases in storm frequency and severity are also expected. This is likely to lead to increased beach erosion and degradation, which could wash away leatherback turtle nests and decrease nesting habitat (13). 

Changes in ocean currents are also expected due to climate change. This may affect juvenile leatherbacks in their migrations following hatching, as well as adults’ navigation. In addition, changes to ocean currents are likely to affect the abundance and distribution of jellyfish and other leatherback turtle prey species (13). 

The leatherback turtle’s ability to adapt to climate change is severely compromised by the rate of the change. Such rapid changes, in combination with the leatherback turtle’s long and slow maturing life history, may limit the species’ capacity to adapt quickly enough to prevent severe population impacts (13). 

Numerous other threats are also compromising the leatherback turtle’s ability to adapt to climate change. 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 (14). Other threats to the leatherback turtle worldwide include habitat loss, boat strikes, and ingestion of discarded plastics, which the turtles mistake for jellyfish (14).

The leatherback turtle is protected throughout most of its range (1), and international trade in the leatherback turtle and products is banned under Appendix I of the Convention on International Trade in Endangered Species (CITES) (3). Many conservation projects have been set up on leatherback turtle 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 (12). 

Despite encouraging signs of stable or increasing leatherback turtle 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 2,000 breeding females in the eastern Pacific, making this population extremely vulnerable (12).

The UK Biodiversity Action Plan for this species is available at UK BAP.

To learn more about a Whitley Award-winning conservation project for this species, click here.

To help conserve this species by working in the field with Earthwatch, click here.

View information on this species at the UNEP World Conservation Monitoring Centre.

More on the leatherback turtle and its conservation:

• Marine Turtle Newsletter:
  www.seaturtle.org/mtn/
• WWF:
  http://www.worldwildlife.org/species/finder/leatherbackturtle/leatherbackturtle.html
• Tagging of Pacific Pelagics:
  www.toppcensus.org