Olive Ridley Sea Turtle

The **olive ridley sea turtle** (*Lepidochelys olivacea*), also known as the **Pacific ridley sea turtle**, are the second smallest and most abundant of all sea turtles found in the world; this species of sea turtle is found in warm and tropical waters, primarily in the Pacific and Indian Oceans. They can also be found in the warm waters of the Atlantic Ocean.

The second smallest after the Kemp’s ridley, the olive ridley turtles weigh between 75-100 pounds (34 - 45 kg) and reach 2-2 ½ feet (roughly .6 m) in length. They are named for their pale green carapace, or shell and are the most abundant of sea turtle species. Like the Kemp's ridley's nest in masses referred to as arribadas. During arribadas, thousands of females may nest over the course of a few days to a few weeks. Adults reach sexual maturity around the age of 15 years.

## Taxonomy

The olive ridley was first described as *Testudo mydas minor*, Suckhow, 1798. It was later renamed *Chelonian olivacea*, Eschscholtz, 1829, and eventually *Lepidochelys olivacea* Fitzinger, 1843. Because Eschscholtz was the first to propose the specific epithet *olivacea*, though, he was credited with the valid name *Lepidochelys olivacea* Eschscholtz, 1829.

The genus name 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 scute counts 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 still somewhat unclear, 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).

Growing to about 2 feet in length, the olive ridley gets its name from its olive-colored carapace, which is heart-shaped and rounded. Males and females grow to the same size; however, females have a slightly more rounded carapace as compared to males.[4] The heart-shaped carapace is characterized by four pairs of pore-bearing inframarginal scutes on the bridge, two pairs of prefrontals, and up to 9 lateral scutes per side. Olive ridleys are unique in that they can have variable and asymmetrical lateral scute 6 to scute 8 counts, ranging from five to 9 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 varies from greenish white in younger individuals to a creamy yellow in older specimens (maximum age is up to 50 years).

## Description

Hatchlings are dark gray with a pale yolk scar, but appear all black when wet. Carapace length ranges from 37 to 50  mm. 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.

Olive ridleys rarely weigh over 50 kg (110 lb). Adults studied in Oaxaca, Mexico ranged from 25 to 46 kg; adult females weighed an average of 35.45 kg (n=58), while adult males weighed significantly less, averaging 33.00 kg (n=17). Hatchlings usually weigh between 12.0 and 23.3 g.

Adults are somewhat sexually dimorphic. Mature males have longer and thicker tails, which are used for copulation, and the presence of enlarged and hooked claws on the males' front flippers allows them to grasp the female carapace during copulation. Males also have longer, more tapered carapaces than females, which have round, dome-like carapaces. Males also have more concave plastrons, believed to be another adaptation for mating. The plastrons of males may also be softer than females.

## Distribution

Olive ridleys occur globally and are found mainly in tropical regions of the Pacific, Indian, and Southern Atlantic Oceans. They are primarily pelagic, spending much of their life in the open ocean, but may also inhabit continental shelf areas and venture into bays and estuaries. Arribadas occur in Mexico, Nicaragua, Costa Rica, Panama, Australia, parts of Africa, and a few beaches along the coast of India. The largest ones occur in Costa Rica, Mexico, and India. Nicaragua has a significant beach in La Flor Wildlife Refuge. Other solitary nesting areas include Guatemala, Brazil, Myanmar, Malaysia, and Pakistan. Worldwide, they nest in approximately 40 countries.

## Ecology and Behavior

**Reproduction**

Mating is often assumed to occur in the vicinity of nesting beaches, but copulating pairs have been reported over 1,000 km from the nearest beach. Research from Costa Rica revealed the number of copulating pairs observed near the beach could not be responsible for the fertilization of the tens of thousands of gravid females, so a significant amount of mating is believed to have occurred elsewhere at other times of the year.

The Gahirmatha Beach in Kendrapara district of Odisha (India), which is now a part of the Bhitarkanika Wildlife Sanctuary, is the largest breeding ground for these turtles. The Gahirmatha Marine Wildlife Sanctuary, which bounds the Bhitarkanika Wildlife Sanctuary to the east, was created in September 1997, and encompasses Gahirmatha Beach and an adjacent portion of the Bay of Bengal. Bhitarkanika mangroves were designated a Ramsar Wetland of International Importance in 2002. It is the world's largest known rookery of olive ridley sea turtles. Apart from Gahirmatha rookery, two other mass nesting beaches have been located, which are on the mouth of rivers Rushikulya and Devi. The spectacular site of mass congregation of olive ridley sea turtles for mating and nesting enthralls both the scientists and the nature lovers throughout the world.

**Feeding**

The olive ridley is predominantly carnivorous, especially in immature stages of the lifecycle. Animal prey consists of protochordates or invertebrates, which can be caught in shallow marine waters or estuarine habitats. Common prey items include jellyfish, tunicates, sea urchins, bryozoans, bivalves, snails, shrimp, crabs, rock lobsters, and sipunculid worms. Additionally, consumption of jellyfish and both adult fish (e.g. *Sphoeroides*) and fish eggs may be indicative of pelagic (open ocean) feeding. The olive ridley is also known to feed on filamentous algae in areas devoid of other food sources. Captive studies have indicated some level of cannibalistic behavior in this species.

## Threats

Threats to olive ridleys include the direct harvest of turtles and eggs for human consumption, entanglement of turtles in commercial fishing gear, and coastal development.