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Olive Ridley Sea Turtle, Lepidochelys olivacea, Family Cheloniidae, pictures, stock photos, images

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Other common names: Olive ridley seaturtle, pacific ridley, olive loggerhead, tortuga golfina (Spanish) (Witherington, 2006)

The Olive Ridley Sea Turtle, Lepidochelys olivacea, is the smallest of sea turtles and the most numerous. It is characterized by its olive-green coloring, its rather large head, and its nearly round shell. It is unique among sea turtles in that the number of lateral scutes varies, from five to nine. Interestingly, some Olive Ridleys are asymmetrical, with more scutes on one side than on the other.

The Olive Ridley is a small sea turtle. Females weigh 35-45 kg (77 to 100 lbs) and have a carapace length of from 60 to 75 cm (25 to 30 in) (Witherington, 2006). They are rather highly domed, with a flattened top to the shell, giving them a flying saucer shape when seen from the side.

The coloring of Olive Ridley Sea Turtles is generally olive-green, but may approach brown, gray or black. They lack the beautiful patterns found on Hawksbill Sea Turtles, Eretmochelys imbricata, and Green Sea Turtles, Chelonia mydas. The underside, or plastron, is yellow, except for that of juveniles, which is white. Olive Ridleys have one claw on each front and rear flipper, two pairs of prefrontal scales, and from five to nine lateral scutes.

While several sea turtle species have inconspicuous openings leading from the Rathke’s glands on the lower portion of their shells, both Olive Ridley Sea Turtles and Kemp’s Ridley Sea Turtles, Lepidochelys kempii, are unusual in that their four gland openings are clearly visible. The purpose of the Rathke’s glands is unclear, but they may secrete pheromones or a substance that repels predators.

Olive Ridley Sea Turtles are primarily tropical, but with some sightings as far north as Alaska and as far south as New Zealand and Chile. Its range does not overlap that of Kemp’s ridley, as the Olive Ridley typically does not inhabit the Gulf of Mexico, home to the Kemp’s ridley. Olive Ridleys in the Atlantic are found mostly on the western coast of Africa and the Northeastearn coast of South America. In the Pacific, they are found in large numbers off the coasts of the Americas, but are rarely found near central Pacific islands. Large numbers are also found in the Indian Ocean. Notable nesting sites are located on the western coast of Central America, northeastern South America, and the eastern coast of India.

Hawksbill Sea Turtle underwater image
Picture of female olive ridley sea turtles, Lepidochelys olivacea, come and go from nesting beach during arribada (mass nesting) Ostional, Costa Rica, Pacific Ocean. Image #: 003581

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Class: Reptilia

Order: Testudines

Suborder: Cryptodera

Superfamily: Chelonioidea

Family: Cheloniidae

Genus Species: Lepidochelys olivacea

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The diet of Olive Ridley Sea Turtles is varied. In their pelagic phase, they feed on sea jellies, sea squirts, pelagic snails, shrimp and crabs. They also eat barnacles and algae they find on floating objects. They can dive up to 500 feet and feed on bottom dwelling shrimp, crabs, snails, sea urchins, and other invertebrates. They are sometimes caught on long lines baited with squid. In coastal areas, they feed on crabs, shellfish and fish.

Like most sea turtles, Olive Ridley Sea Turtles travel great distances from feeding grounds to the beaches they were born in order to nest. While some nest in isolation, the majority wait for other Olive Ridleys to gather, and as if by signal, they arrive on the nesting beach together in massive arribadas. What environmental factors trigger an arribada are uncertain, but winds, tides, moon phase, and the proximity of many other Olive Ridleys may be contributing factors.

When an arribada occurs, thousands, sometimes hundreds of thousands, of Olive Ridleys arrive at night on the same beach over the course of several days. The eggs from the earliest nests are often dug up and destroyed by later nesting turtles. About 100 eggs are laid, and it takes about 50 to 70 days for eggs to hatch. Females are ready to nest again in about two weeks, but they often wait longer for the event that signals an arribada. Olive Ridleys are thought to nest every year.

Why arribadas have evolved is also a matter of mystery. One hypothesis is that local beach predators quickly become satiated on eggs they find, allowing remaining eggs to reach maturity. However, since olive ridelys hatch en masse and enter the ocean almost simultaneously, ocean predators gather to take advantage of the enormous food source, thus largely negating the previous advantage.

Olive ridley sea turtle hatchlings weigh about 17 g (1/2 oz). They hatch at night and make a fast dash to the sea by the thousands. Some become pelagic while others make use of coastal environments. Olive Ridleys mature faster than most other species, reaching adulthood at between seven and sixteen years.

While massive arribadas encourage the notion that Olive Ridley Sea Turtles are plentiful, they are nonetheless decreasing in number worldwide. The IUCN lists the Olive Ridley as Endangered throughout their range. They are often caught in fishing vessels, especially shrimp trawlers, and are frequently hooked by longlines. They are also at risk from floating plastic garbage, which they ingest, and from pollution which destroys their nesting sites. Dogs, coyotes, pigs and other predators eat their eggs, as do humans in various parts of the world.

For a diagram helpful in identifying the Olive Ridley Sea Turtle, see: http://marinebio.org/species.asp?id=318

• Olive Ridley Sea Turtle information assembled from published and on-line sources by Kevin Miller on Nov. 9, 2006 for SeaPics.com.

Sources:

Perrine, D. Sea Turtles of the World, Voyageur Press, 2003

Ripple, J. Sea Turtles, Voyageur Press, 1996

Witherington, B. Sea Turtles, Voyageur Press, 2006