Olive Ridley Sea Turtle

Lepidochelys olivacea

Description

The olive ridley is a relatively small sea turtle, reaching a carapace length of 23-32 in (58-81 cm) and a weight of around 90 lbs (41 kg). Its light-green shell is mottled with darker green, and its forelimbs are broad.

Behavior

Olive ridley turtles may nest at any time during the year, with seasonal peaks that vary with the nesting beach. Females tend to emerge from the water to nest in synchronized groups called arribadas, which is Spanish for "arrival." The females make their way up the sandy beach, dig a shallow nest with their hind limbs above the surf zone, lay a clutch of 74-166 eggs, cover the eggs with sand, and then return to the water. Each female lays two to three clutches each season. The incubation period is about 55 days. The hatchlings emerge as a group and head for the sea together. Adult turtles may dive deeply to feed on bottom-dwelling crustaceans, or forage on crustaceans that rise close to the surface at night. The main food items are crab and shrimp, supplemented by jellyfish, other small invertebrates, and fish eggs.

Habitat

Adult olive ridley turtles are most commonly found over good foraging habitat in warm-temperate, subtropical, and tropical waters. The tropical nesting beaches are sandy. Most nesting occurs along mainland beaches, and sometimes on islands.

Distribution

The olive ridley turtle is a circumglobal species, and is found in tropical, subtropical, and warm-temperate regions of the Pacific, Atlantic, and Indian Oceans.

Threats

The olive ridley turtle has declined in abundance in many parts of its range, and numerous breeding populations have become severely depleted or extirpated. This decline has been caused by excessive hunting of the adults for meat, and the collecting of eggs from nesting beaches. The adults are also taken as by-catch in the shrimp fishery. In some areas nesting habitats have been lost to residential and tourism-related developments. Natural predators of eggs and hatchlings take a huge toll in most areas, and there are also many pelagic predators. It has been suggested that most populations of the olive ridley turtle are in danger and may not be self-sustaining over the long term. The largest arribadas, estimated at up to 500,000 females in the late 1970s, use two nesting beaches in Costa Rica. Beaches in India and Mexico each attract up to 300,000 individuals per year. There are no estimates of the total population of this species, but it is in decline.

Conservation and Recovery

Some of the important nesting sites of the olive ridley turtle are now protected. Santa Rosa National Park in Costa Rica protects an important site known as Nancite. Ostional, another major site in Costa Rica, was pronounced a sanctuary for marine turtles in 1982. Another significant site is found within Bhitar Kanika Sanctuary, at Gahirmatha beach in India. These sanctuaries provide effective protection to the species while it nests, yet when the olive ridley turtles are at sea they may still be severely exploited. International trade is banned by the Convention on International Trade in Endangered Species (CITES). To stop the olive ridley fishery, Ecuador has instituted a major preservation plan. In many other areas, protective legislation exists, but is not enforced. Conservation of this rare sea turtle requires the designation of additional protected areas of its nesting habitat. National parks and other reserves should be adequately protected, and existing laws against hunting and egg-collecting should be enforced. Areas containing large numbers of the species, especially those areas near nesting beaches, should institute restricted fishing zones. High priority should be given to the development and use of fishing equipment that prevents the incidental by-catch of sea turtles; the use of turtle excluder devices on shrimp-fishing boats should be required. Because of the nature of this turtle's distribution, regional agreements on its conservation are essential.

Contact

Instituto Nacional de Ecología
Av. Revolución, 1425
Col. Campestre, C.P. 01040, Mexico, D.F.
http://www.ine.gob.mx/

Reference

National Marine Fisheries Service and U.S. Fish and Wildlife Service. 1998. Recovery Plan for U. S. Pacific Populations of the Olive Ridley Turtle (Lepidochelys olivacea ). National Marine Fisheries Service, Silver Spring, Maryland.