Added September 14 2003.

Dermochelyidae

The Leatherback Turtle

Genus Common Name No. of species Location Notes

Dermochelys Leatherback Turtle [Fr: Tortue luth] 1 Worldwide throughout the oceans, as far north as Norway, Iceland and Alaska, and as far south as Chile: apart from egg-laying time, normally only found in deep waters. The sole species in this family is Dermochelys coriacea, the largest sea turtle in the world. It differs from the other sea turtles in two significant ways: firstly, the shell lacks horny plates and is covered with a leathery skin (hence the common name), and secondly, it has essentially an endothermic (warm-blooded) system. This allows them their long journeys into high latitudes and their entry into cold currents to feed. The primary adult diet appears to be jellyfish and also creatures such as sea squirts [Alderton]: juveniles may also take other floating organisms [Spawls et al]. The diving ability of the leatherbacks is also impressive, with at least 350m (about 1,000ft) being attained and possible much greater depths: the lungs of the creature are adapted to collapse without any damage during this activity. The shell is rather elongated and slopes backwards: males have concave plastrons. Both flippers and head are large, the head also appearing somewhat rounded. Size: maximum carapace length about 1.8m (5ft), maximum mass about 850kg [Spawls et al]. Coloration: black or deep brown, spotted with white and with paler skin ridges: plastron and underside of head is whitish. Each adult has a unique pink spot on the top of its head that can help identify individuals. Juveniles have shells covered with small blue-grey scales that appear black when wet: the ridges of the shell appear like a line of white beads [Spawls et al] and the flippers are edged with white or cream. Reproduction: Courtship and mating have never been observed, but as with all other sea turtles the females must come ashore to lay their eggs at night on a sandy beach. They can deposit up to 1000 eggs, which takes several trips, the female returning every 9-11 days. Before leaving the nest the female circles its nesting site, as do the hatchlings before they head for the sea [Alderton]. Egg fertility is very high, necessarily so because of the losses suffered by the hatchling turtles between egg deposition (nests may be raided) and hatching, and especially between hatching and the entry into the water, during which time they are vulnerable to large crabs, gulls and fish and any other predator. Hatchlings always emerge at night. Some juveniles may have claws, but by adulthood these are lost. Most if not all nesting sites are on continental mainland rather than islands [Alderton]. Conservation: although Dermochelys is in better shape than some of the other marine turtles, the principal danger to its future is degradation or uncontrolled exploitation of its nesting sites, eg by development or by wholescale human use of the eggs as food (this being an understandable problem in poorer countries). The other danger comes from marine pollution: some leatherbacks have been found choked to death on plastic bags and similar items, probably having mistaken them for jellyfish [Spawls et al].

Bibliography

Turtles and Tortoises of the World, David Alderton, Blandford, London 1999.

A Field Guide to the Reptiles of East Africa, Stephen Spawls, Kim Howell, Robert Drewes and James Ashe, Natural World/Academic Press, London 2002.

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Genus	Common Name	No. of species	Location	Notes
Dermochelys	Leatherback Turtle [Fr: Tortue luth]	1	Worldwide throughout the oceans, as far north as Norway, Iceland and Alaska, and as far south as Chile: apart from egg-laying time, normally only found in deep waters.	The sole species in this family is Dermochelys coriacea, the largest sea turtle in the world. It differs from the other sea turtles in two significant ways: firstly, the shell lacks horny plates and is covered with a leathery skin (hence the common name), and secondly, it has essentially an endothermic (warm-blooded) system. This allows them their long journeys into high latitudes and their entry into cold currents to feed. The primary adult diet appears to be jellyfish and also creatures such as sea squirts [Alderton]: juveniles may also take other floating organisms [Spawls et al]. The diving ability of the leatherbacks is also impressive, with at least 350m (about 1,000ft) being attained and possible much greater depths: the lungs of the creature are adapted to collapse without any damage during this activity. The shell is rather elongated and slopes backwards: males have concave plastrons. Both flippers and head are large, the head also appearing somewhat rounded. Size: maximum carapace length about 1.8m (5ft), maximum mass about 850kg [Spawls et al]. Coloration: black or deep brown, spotted with white and with paler skin ridges: plastron and underside of head is whitish. Each adult has a unique pink spot on the top of its head that can help identify individuals. Juveniles have shells covered with small blue-grey scales that appear black when wet: the ridges of the shell appear like a line of white beads [Spawls et al] and the flippers are edged with white or cream. Reproduction: Courtship and mating have never been observed, but as with all other sea turtles the females must come ashore to lay their eggs at night on a sandy beach. They can deposit up to 1000 eggs, which takes several trips, the female returning every 9-11 days. Before leaving the nest the female circles its nesting site, as do the hatchlings before they head for the sea [Alderton]. Egg fertility is very high, necessarily so because of the losses suffered by the hatchling turtles between egg deposition (nests may be raided) and hatching, and especially between hatching and the entry into the water, during which time they are vulnerable to large crabs, gulls and fish and any other predator. Hatchlings always emerge at night. Some juveniles may have claws, but by adulthood these are lost. Most if not all nesting sites are on continental mainland rather than islands [Alderton]. Conservation: although Dermochelys is in better shape than some of the other marine turtles, the principal danger to its future is degradation or uncontrolled exploitation of its nesting sites, eg by development or by wholescale human use of the eggs as food (this being an understandable problem in poorer countries). The other danger comes from marine pollution: some leatherbacks have been found choked to death on plastic bags and similar items, probably having mistaken them for jellyfish [Spawls et al].