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Gregory R. Mann, Ph.D. {ret.}

Leatherback Sea Turtle

“Dermochelys coriacea”

Leatherback Sea Turtles are the largest of the sea turtles reaching up to 2.4 meters in length and weighing 227-907 kilograms. Their flippers span an average of 2.7 meters from the tip to tip. The “shell” of the Leatherback is actually its bones underneath its firm dark brown or black skin which has 7 pronounced vertical ridges on its back and 5 ridges on its ventral side. Leatherback Sea Turtles are named for their tough, oil-saturated, rubbery skin which is strengthened by a mosaic of small bones beneath the skin. This gives the turtle a leathery appearance and feel. Leatherbacks are the only sea turtle species that lack scales and a hard shell. A tooth-like cusp is located on each side of the upper jaw; the lower jaw is hooked anteriorly. The Leatherback Sea Turtle can dive to great depths. Individuals equipped with depth recorders dove to over 1,000 meters deep. The shallowest dives occurred at dusk and the deepest at dawn. These Leatherbacks were probably feeding on sea jellies that concentrate below 600 meters during the day and move into surface waters at dusk. The turtles dove almost continuously with only brief intervals at the surface to breathe. Leatherback Sea Turtles can rest or sleep underwater for several hours at a time but submergence time is much shorter while diving for food or to escape predators. Breath-holding ability is affected by activity and stress, which is why turtles drown in shrimp trawls and other fishing gear within a relatively short time. Because Leatherback Sea Turtles are difficult to study in the open ocean, scientists are just beginning to learn about their life history. Today, radio transmitters attached to nesting turtles to help track the sea creatures on their travels and provide valuable information.

Leatherback Sea Turtles can be found in tropical and temperate seas in the Atlantic, Pacific and Indian Oceans. Their range is as far north as British Columbia, Newfoundland and the British Isles and as far south as Australia, Cape of Good Hope and Argentina. The Leatherback is the most migratory of all sea turtles. They are omnivorous, feeding on their primary food source sea jellies as well as crabs & fishes. They are also known to eat sea urchins, squid, crustaceans, tunicates, blue-green algae & seaweed. It is estimated that Leatherbacks reach sexual maturity between 6-10 years of age. Although Leatherback Sea Turtles move swiftly in the ocean, they are slow and defenseless on land. Males almost never leave the water. Adult females require sandy nesting beaches backed with vegetation and with proximity to deep water and generally rough seas. Like other sea turtle species, Leatherback females are fertilized at sea then leave the water at night to dig their nests where they deposit between 70-80 eggs. Incubation takes from 55-75 days and their eggs hatch at night to avoid predation during the hatchling’s return to the sea. It is estimated that 26,000-43,000 females nest annually worldwide, a decline of more than half since 1980. Exponential declines in Leatherback nesting have occurred along the Pacific coasts of Mexico and Costa Rica.

The Leatherback Sea Turtle nesting population in Mexico, once the world’s largest at 65% of the global nesting population is now less than 1% of what it was in 1980. The largest nesting populations now occur in the western Atlantic in French Guiana (4,500-7,500/year) and Colombia (3,000/year). The 2nd largest nesting populations are now found in the western Pacific in Indonesia (about 600-650/year). In the United States, small nesting populations occur on the Florida east coast (35 females/year), in the U.S. Virgin Islands (50-100 females/year) and in Puerto Rico (30-90 females/year). In the U.S., nesting occurs from March-July during which time females will nest 5-7 times with an observed maximum of 11 nests. The average inter-nesting interval is about 9-10 days. Most Leatherback Sea Turtles re-migrate to their nesting beaches at 2-3 year intervals.

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