Description: Growing to about 2 feet 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 to 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 1.5 to 2.0 inches. 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 110 lbs. Adults studied in Oaxaca, Mexico, ranged from 55 to 101 lbs.; adult females weighed an average of 78.2 lbs., while adult males weighed significantly less, averaging 72.75 lbs.. Hatchlings usually weigh between 0.42 and 0.82 ounces.

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

Habitat: Most observations are typically within 9.3 miles of mainland shores in protected, relatively shallow marine waters, 72 to 180 feet deep. Olive ridleys are occasionally found in open waters. The multiple habitats and geographical localities used by this species vary throughout its lifecycle.

Range: The olive ridley turtle has a circumtropical distribution, living in tropical and warm waters of the Pacific and Indian Oceans from India, Arabia, Japan, and Micronesia south to southern Africa, Australia, and New Zealand. In the Atlantic Ocean, it has been observed off the western coast of Africa and the coasts of northern Brazil, Suriname, Guyana, French Guiana, and Venezuela. Additionally, the olive ridley has been recorded in the Caribbean Sea as far north as Puerto Rico. A female was found alive on an Irish Sea beach on the Isle of Anglesey, Wales, in November 2016, giving this species its northernmost appearance. It was taken in by the nearby Anglesey Sea Zoo, while its health was assessed. A juvenile female was found off the coast of Sussex in 2020. The olive ridley is also found in the eastern Pacific Ocean from the Galapagos Islands and Chile north to the Gulf of California, and along the Pacific coast to at least Oregon. Migratory movements have been studied less intensely in olive ridleys than other species of marine turtles, but they are believed to use the coastal waters of over 80 countries. Historically, this species has been widely regarded as the most abundant sea turtle in the world. More than one million olive ridleys were commercially harvested off the coasts of Mexico in 1968 alone.

The population of Pacific Mexico was estimated to be at least 10 million prior to the era of mass exploitation. More recently, the global population of annual nesting females has been reduced to about two million by 2004, and was further reduced to 852,550 by 2008. This indicated a dramatic decrease of 28 to 32% in the global population within only one generation (i.e., 20 years).

Olive ridley sea turtles are considered the most abundant, yet globally they have declined by more than 30% from historic levels. These turtles are considered endangered because of their few remaining nesting sites in the world. The eastern Pacific turtles have been found to range from Baja California, Mexico, to Chile. Pacific olive ridleys nest around Costa Rica, Mexico, Nicaragua, and the northern Indian Ocean; the breeding colony in Mexico was listed as endangered in the US on July 28, 1978.

Found in these States: AK | CA | HI | ME | NY | OR | RI | WA

Diet: The olive ridley is predominantly carnivorous, especially in immature stages of its 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.

Reproduction: Mating is often assumed to occur in the vicinity of nesting beaches, but copulating pairs have been reported over 33.5 miles 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.

Olive ridleys generally begin to aggregate near nesting beaches about two months before nesting season, although this may vary throughout their range. In the eastern Pacific, nesting occurs throughout the year, with peak nesting events (arribadas) occurring between September and December. Nesting beaches can be characterized as relatively flat, midbeach zone, and free of debris. Beach fidelity is common, but not absolute. Nesting events are usually nocturnal, but diurnal nesting has been reported, especially during large arribadas. Exact age of sexual maturity is unknown, but this can be somewhat inferred from data on minimum breeding size. For example, the average carapace length of nesting females at Playa Nancite, Costa Rica, was determined to be 25 inches, with the smallest recorded at 21 inches. Females can lay up to three clutches per season, but most only lay one or two clutches. The female remains near shore for the internesting period, which is about one month. Mean clutch size varies throughout its range and decreases with each nesting attempt.

A mean clutch size of 116 (30 to 168 eggs) was observed in Suriname, while nesting females from the eastern Pacific were found to have an average of 105 (74 to 126 eggs). The incubation period is usually between 45 and 51 days under natural conditions, but may extend to 70 days in poor weather conditions. Eggs incubated at temperatures of 87.8 to 89.6 ℉ produce only females; eggs incubated at 82.4 ℉ or less produce solely males; and incubation temperatures of 84.2 to 86 ℉ produce a mixed-sex clutch. Hatching success can vary by beach and year, due to changing environmental conditions and rates of nest predation.

Status: The olive ridley is classified as vulnerable according to the International Union for Conservation of Nature and Natural Resources, and is listed in Appendix I of CITES. These listings were largely responsible for halting the large-scale commercial exploitation and trade of olive ridley skins. The Convention on Migratory Species and the Inter-American Convention for the Protection and Conservation of Sea Turtles have also provided olive ridleys with protection, leading to increased conservation and management for this marine turtle. National listings for this species range from endangered to threatened, yet enforcing these sanctions on a global scale has been unsuccessful for the most part. Conservation successes for the olive ridley have relied on well coordinated national programs in combination with local communities and nongovernment organizations, which focused primarily on public outreach and education. Arribada management has also played a critical role in conserving olive ridleys. Lastly, enforcing the use of turtle excluder devices in the shrimp trawling industry has also proved effective in some areas. Globally, the olive ridley continues to receive less conservation attention than its close relative, Kemp's ridley (L. kempii).