Leatherback Sea Turtle
The Leatherback Sea Turtle, Dermochelys coriacea, is the biggest of all living turtles. It reaches a length of over 8.8 feet and a weight of 2,000 pounds. It is the world’s 4th largest reptile. It is found in all tropical and subtropical oceans. It is the only extant species in the genre Dermochelys and the family Dermochelyidae.
This species has many unique features that distinguish it greatly from other sea turtles. Its shell lacks the bony scales of other turtles, comprising mainly of connective tissue. Its metabolic rate is three times higher than one would expect for a reptile of its size. It can maintain a body temperature as much as 64 degrees above that of the surrounding water.
Leatherbacks mate at sea. Males never leave the water once they hatch. Females mate every three to four years, returning to the beaches where they themselves hatched, to deposit their eggs. A female may lay as many as ten clutches in one breeding season. Females usually mate with multiple males to insure against male infertility and sperm depletion to allow selection of highest quality sperm and increase the genetic variation amongst offspring.
Cells begin to develop within hours of fertilization, but become suspended while the mother is laying eggs from a previous mating. Development soon resumes, but the embryos remain susceptible to movement-induced mortality in their nests until the membranes fully develop through the first 20 to 25 days of inception.
The nesting beach must be comprised of soft sand because their soft leatherback shells are easily damaged by hard rocks. The beach must also have a shallow approach angle from the sea. This is a source of vulnerability for the turtles because such beaches are easily eroded. Females excavate a nest above the high-tide line with their flippers. They then begin to lay their eggs, producing about 110 ova, 70 of which are large and fertile, the remaining 40 smaller and sterile. The female carefully back-fills the nest, making sure to disguise it from predators with a scattering of sand.
The eggs hatch in about 60 days. Like some other reptiles, the ambient temperature of the nest determines the gender of the hatchlings. The eggs hatch while still buried under the sand. After nightfall, the hatchlings dig their way to the surface and make their way to the sea. Once they reach the ocean they are generally not seen again until maturity. Very few survive this mysterious period to become adults. Most are eaten by birds or other reptiles before they have a chance to reach the water. When the lights of a city are visible from a hatching site, Leatherback hatchlings are attracted to the lights and away from the sea. Many of these hatchlings are struck by traffic or otherwise perish.
The diet of the leatherback consists of jellyfish and other aquatic animals and plants. Giant leatherbacks travel each year from the Caribbean to northern US, Canada, UK and Europe, following the Gulf Stream in order to eat the jellyfish found there. Although they prefer deep water, they are mostly seen within sight of land. In warmer climates and summer months to the north, they are often seen basking near the surface.