The olive ridley sea turtle is the smallest of the sea turtles. Hatchlings are black. The carapace is broad and rounded, with four inframarginal scutes joining the plastron and carapace. Each of these scutes is perforated with one pore. Costal scutes are often irregularly divided, so that they number from five to nine and are often asymetric. Males have a longer, thicker tail than females; one enlarged, hooked claw on each front flipper; and a concave plastron. The posterior marginal scutes of hatchlings are serrated. Young olive ridley turtles are also characterized by three longitudinal dorsal keels that disappear with age.
Can be Confused With
In the Atlantic, olive ridley turtles may be confused with their cogener, the Kemp’s ridley turtle (Lepidochelys kempi). The Kemp’s ridley turtle consistently possesses five costal scutes, whereas the olive ridely often has more than five due to divisions of the scutes.
The olive ridley sea turtle is tropical, found in the Pacific, Indian, and Atlantic Oceans. They are the most common sea turtle in the eastern Pacific Ocean, nesting from southern Sonora in Mexico to Columbia and the Galapagos Islands. Non-nesting olive ridleys have also been reported along the Pacific coast of the United States. The species is scarce in the western Pacific. In the Indian Ocean, olive ridley turtles are abundant along the coasts of Sri Lanka and eastern India. In the Atlantic Ocean, they occur widely on the western shores of Africa and occasionally in South America along the coasts of northern Brazil, French Guiana, Surinam, Guyana, and Venezuela. They are also found in the Caribbean on rare occasions.
Ecology and Behavior
Olive ridley turtles typically nest in large aggregations. Males and females begin to assemble near nesting beaches two months before the nesting season. Some mating occurs at this time, but is believed to also occur prior to aggregation. Nesting occurs year round, but peaks in spring or early summer. Females nest between one and three times in a year, depositing approximately 100 eggs in each nest. The age of sexual maturity is unknown, but carapace length of nesting females has been measured at greater than 60 cm. Olive ridley sea turtles are coastal, but may migrate thousands of kilometers in order to exploit different feeding grounds and reach nesting sites. Little is known about the hatchlings, but they may be associated with floating vegetation at convergence zones offshore.
Feeding and Prey
There is little data regarding the diet of olive ridley turtles, but adults exploit a wide variety of foraging habitats and are generalist carnivores. Their diet is known to include salps, jellyfish, tunicates, crabs, fish, molluscs, algae, bryozoans, fish eggs, sipunculids, and ascidians. Known adult prey species include Metcalfina sp., Pleuroncodes planipes, Pelagia sp., Pyrosoma sp., Salpa sp., Clypeaster humilis.
Threats and Status
The olive ridley sea turtle is probably the most abundant sea turtle in the world. Nonetheless, the species is classified as endangered by the IUCN. In the United States, the olive ridley is classified as threatened, with the exception of the Mexican population, which is endangered. Continuing decline in population may lead to the olive ridley sea turtle being listed as endangered in the United States.
Ernst, C.H. and R.W. Barbour. 1989. Turtles of the world. Smithsonian Institution Press, Washington, DC.
Lutz, P.L, and J.A. Musick (eds). 1997. The Biology of Sea Turtles. CRC Press LLC, New York, NY.
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, MD.
National Marine Fisheries, Office of Protected Resources. 2011. Olive Ridley Turtle (Lepidochelys olivacea). Available online here.
Status - ESA, U.S. FWS -
E (Mexican nesting pop.) T (Except where endangered)