The olive ridley sea turtle (Lepidochelys olivacea), also known commonly as the Pacific ridley sea turtle, is a species of turtle in the family Cheloniidae. The species is the second-smallest and most abundant of all sea turtles found in the world. L. olivacea is found in warm and tropical waters, primarily in the Pacific and Indian Oceans, but also in the warm waters of the Atlantic Ocean. This turtle and the related Kemp's ridley sea turtle are best known for their unique synchronised mass nestings called arribadas, where thousands of females come together on the same beach to lay eggs.
Taxonomy The olive ridley sea turtle may have been first described as Testudo mydas minor by Georg Adolf Suckow in 1798. It was later described and named Chelonia multiscutata by Heinrich Kuhl in 1820. Still later, it was described and named Chelonia olivacea by Johann Friedrich von Eschscholtz in 1829. The species was placed in the subgenus Lepidochelys by Leopold Fitzinger in 1843. After Lepidochelys was elevated to full genus status, the species was called Lepidochelys olivacea by Charles Frédéric Girard in 1858. Because Eschscholtz was the first to propose the specific epithet olivacea, he is credited as the binomial authority or taxon author in the valid name Lepidochelys olivacea (Eschscholtz, 1829). The parentheses indicate that the species was originally described in a different genus. The generic name, Lepidochelys, is derived from the Greek words lepidos, meaning scale, and chelys, which translates to turtle. This could possibly be a reference to the supernumerary costal scutes characteristic of this genus. The etymology of the English vernacular name "olive" is somewhat easier to resolve, as its carapace is olive green in color. However, the origin of "ridley" is unknown, perhaps derived from "riddle". Lepidochelys is the only genus of sea turtles containing more than one extant species: L. olivacea and the closely related L. kempii (Kemp's ridley).
Description Growing to about 61 cm (2 ft) in carapace length (measured along the curve), the olive ridley sea turtle gets its common name from its olive-colored carapace, which is heart-shaped and rounded. Males and females grow to the same size, but females have a slightly more rounded carapace as compared to males. The heart-shaped carapace is characterized by four pairs of pore-bearing inframarginal scutes on the bridge, two pairs of prefrontals, and up to nine lateral scutes per side. L. olivacea is unique in that it can have variable and asymmetrical lateral scute counts, ranging from five to nine plates on each side, with six to eight being most commonly observed. Each side of the carapace has 12–14 marginal scutes. The carapace is flattened dorsally and highest anterior to the bridge. It has a medium-sized, broad head that appears triangular from above. The head's concave sides are most obvious on the upper part of the short snout. It has paddle-like fore limbs, each having two anterior claws. The upper parts are grayish-green to olive in color, but sometimes appear reddish due to algae growing on the carapace. The bridge and hingeless plastron of an adult vary from greenish white in younger individuals to a creamy yellow in older specimens (maximum age is up to 50 years). Hatchlings are dark gray with a pale yolk scar, but appear all black when wet. Carapace length of hatchlings ranges from 37 to 50 mm (1.5 to 2.0 in). A thin, white line borders the carapace, as well as the trailing edge of the fore and hind flippers. Both hatchlings and juveniles have serrated posterior marginal scutes, which become smooth with age. Juveniles also have three dorsal keels; the central longitudinal keel gives younger turtles a serrated profile, which remains until sexual maturity is reached. The olive ridley sea turtle rarely weighs over 50 kg (110 lb). Adults studied in Oaxaca, Mexico, ranged from 25 to 46 kg (55 to 101 lb); adult females weighed an average of 35.45 kg (78.2 lb) (n=58), while adult males weighed significantly less, averaging 33.00 kg (72.75 lb) (n=17). Hatchlings usually weigh between 12.0 and 23.3 g (0.42 and 0.82 oz). Adults are sexually dimorphic. The mature male has a longer and thicker tail, which is used for copulation, and the presence of enlarged and hooked claws on the male's front flippers allows him to grasp the female's carapace during copulation. The male also has a longer, more tapered carapace than the female, which has a rounded, dome-like carapace. The male also has a more concave plastron, believed to be another adaptation for mating. The plastron of the male may also be softer than that of the female.
Distribution
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