The leatherback turtle is the largest turtle, with no hard shell, which can survive in cool waters and dive deep in search of jellyfish and other food.
The largest of the marine turtles, the leatherback can reach a total length of about 1.8m (6ft) with a weight of about 540kg (1,200lb) and a span of about 2.7m from the tip of one front flipper to the tip of the other.
They have no obvious shell. Instead bones are buried in their dark brown or blackish skin and flexible bony plates are set on ridges.
There are seven longitudinal ridges on the turtles' back and five on their underside.
The flexible internal shell allows leatherbacks to withstand water pressure so they can dive to greater depths. They also differ from other turtles in that they do not have claws on their flippers.
Leatherbacks are found in Pacific, Indian and Atlantic oceans, particularly tropical regions.
They inhabit warm open seas throughout the world. They feed primarily on jellyfish, and have backward-pointing spines in their throat to prevent prey escaping.
Leatherbacks are strong swimmers and undertake long journeys. Tagged individuals have been known to cross the Atlantic, ending up of the west coast of the UK, including Cardigan Bay.
After nesting the females circle the site, possibly to reinforce it in their memory to aid return and the hatchlings also do this before heading to the sea.
They are deep divers, sometimes reaching depths of 1,000m in search of food and can hold their breath for up to half an hour.
Like other turtles, leatherbacks leave the sea to dig burrows in the sand and lay eggs. They choose moonless nights to come ashore to avoid being seen by predators. The hatchlings have small pearly scales that disappear as they get older.
Leatherbacks are listed as Critically Endangered by the IUCN Red List.
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