About The Species
The olive ridley gets its name from the olive green color of its heart-shaped carapace (top shell). The species is among the smallest of the world’s sea turtles and is found primarily in the tropical regions of the Pacific, Indian, and Atlantic Oceans.
The olive ridley is considered the most abundant sea turtle in the world, with an estimated 800,000 nesting females every year. The species is greatly reduced from historical estimates (for example, 10 million olive ridleys in the Pacific Ocean), prior to overexploitation for turtle meat, eggs, and leather.
The olive ridley is one of two species of sea turtles that engage in "arribada" nesting, where large groups of females gather offshore and come onto the beach to nest all at once. Nesting in large groups may be a defense against predators, or a result of environmental factors influencing nesting. With many turtles coming ashore together and many nests subsequently hatching at the same time, it may help to reduce predation. The other species of sea turtle that nests en masse is the Kemp’s ridley.
Status
The olive ridley may be the most abundant sea turtle on the planet, but some argue that it is also the most exploited. According to the International Union for Conservation of Nature and Natural Resources Red List, there has been between a 30 and 50 percent reduction in global population size. Although some nesting populations have increased in the past few years or are currently stable, overall the reduction is greater than the overall increase in other populations.
In the western Atlantic Ocean, although there has been an 80 percent reduction in certain nesting populations since 1967, Brazil has reported an increase in their nesting population. In the eastern Atlantic Ocean, Gabon currently hosts the largest olive ridley nesting population with an estimated 948 to 5452 breeding females per year.
On the Pacific coast of Mexico, only a single arribada nesting beach remains in La Escobilla, Mexico, where an estimated 450,000 turtles nest. The Pacific coast of Costa Rica supports an estimated 600,000 nesting olive ridleys between its two major arribada beaches, Nancite and Ostional. Other countries in the Pacific hosting nesting populations producing between 100 and 2,000 nests per year include Guatemala, Honduras, El Salvador, Australia, Indonesia, and Vietnam. At-sea estimates of density and abundance of the olive ridley along the Mexico and Central American coasts show a yearly estimate of over 1 million, which is consistent with the increase seen on the eastern Pacific nesting beaches as a result of protection programs that began in the 1990s.
In the Indian Ocean, three arribada beaches occur in Odisha, India - Gahirmatha, Devi River mouth, and Rushikulya—with an estimated >100,000 nests per year. More recently, a new mass nesting site was discovered in the Andaman islands, India, with more than 5,000 nests reported in a season. Declines in solitary nesting of olive ridleys have been recorded in Bangladesh, Myanmar, Malaysia, and Pakistan. In particular, the number of nests in Terengganu, Malaysia, has declined from thousands of nests to just a few dozen per year.
The 2014 5-year review of the olive ridley sea turtle under the ESA provides additional information on abundance and population trends
Protected Status
ESA Endangered
1 distinct population segment
- Mexico's Pacific coast breeding populations
ESA Threatened
1 distinct population segment
Appearance
Olive ridleys look very similar to the Kemp’s ridley sea turtles. The two species are the smallest of all sea turtles.
Olive ridley turtles are an olive/grayish-green (darker in the Atlantic than in the Pacific) with a heart-shaped carapace (top shell) and 5 to 9 pairs of costal "scutes." Western Atlantic olive ridleys usually have a darker coloration than eastern Pacific olive ridleys. Each of the four flippers of an olive ridley has one or two claws. The size and form of the olive ridley varies from region to region, with the largest animals observed in West Africa. Also, the carapace of eastern Pacific olive ridleys is greater in height than in other populations.
Behavior and Diet
Sea turtles spend most of their lives in the ocean, but females leave the water to lay eggs. When they are active, olive ridley turtles must swim to the ocean surface to breathe every few minutes. When they are resting, they can remain underwater for much longer periods of time.
The olive ridley is omnivorous, meaning it feeds on a wide variety of food items, including algae, lobster, crabs, tunicates, mollusks, shrimp, and fish. Olive ridleys can dive to depths of 500 feet to forage on benthic invertebrates (those that live at the bottom of a body of water).
Where They Live
The olive ridley is mainly a pelagic (open ocean) sea turtle, but has been known to inhabit coastal areas, including bays and estuaries. Olive ridleys mostly breed annually and have an annual migration from pelagic foraging, to coastal breeding and nesting grounds, back to pelagic foraging. Trans-Pacific ships have observed olive ridleys over 2,400 miles from shore.
Olive ridleys are globally distributed in the tropical regions of the Atlantic, Pacific, and Indian Oceans. In the Atlantic Ocean, they are found along the coasts of West Africa and South America. In the Eastern Pacific, they occur from Southern California to Northern Chile.
Olive ridleys often migrate great distances between feeding and breeding grounds. Using satellite telemetry tags, scientists have documented both male and female olive ridleys leaving the breeding and nesting grounds off the Pacific coast of Costa Rica and migrating out to the deep waters of the Pacific Ocean.
Solitary nesting occurs extensively throughout this species' range, and nesting has been documented in approximately 40 countries worldwide. Arribada nesting, however, occurs on only a few beaches worldwide.
Lifespan & Reproduction
No one knows exactly how long olive ridleys live, but like other sea turtles, they are likely long-lived. Olive ridleys reach sexual maturity around 14 years with a range of 7 to 17 years.
The olive ridley sea turtle has one of the most extraordinary nesting habits in the natural world. Similar to Kemp’s ridleys, large groups of turtles gather offshore of nesting beaches. Then, all at once, vast numbers of turtles come ashore and nest in what is known as an "arribada" which means "arrival" in Spanish. During these arribadas, hundreds to thousands of females come ashore to lay their eggs. At many nesting beaches, the nesting density is so high that previously laid egg clutches are dug up by other females while excavating the nest chamber to lay their own eggs.
There are many theories on what triggers an arribada, including offshore winds, lunar cycles, and the release of pheromones by females. However, scientists have yet to conclusively determine why exactly arribadas occur. Not all females nest during an arribada—some are solitary nesters while others employ a mixed nesting strategy. For example, a single female might nest during an arribada, as well as nest alone during the same nesting season.
Arribada nesting is a behavior found only in the genus Lepidochelys which includes the Kemp's ridley sea turtles and the olive ridleys. Although other turtles have been documented nesting in groups, no other turtles (marine or land) have been observed nesting in such mass numbers and synchrony.
Females nest every year, one to three times a season, laying clutches of approximately 100 eggs. Incubation takes about 2 months. When finished laying, most sea turtles cover their eggs with sand using their rear flippers to pack it in firmly on top of their clutch. However, since the olive ridley is so small and relatively light, they do not have the power to use their rear flippers in this way—instead, they use their whole bodies, beating the sand down with their lower shells after covering the eggs.
Threats
Harvest of Eggs and Killing of Adults
The principal cause of the historical, worldwide decline of the olive ridley sea turtle is long-term collection of eggs and killing of adults on nesting beaches. The arribada nesting behavior concentrates females and nests at the same time and in the same place, allowing for mass killing of adult females, as well as the taking of an extraordinary number of eggs.
Bycatch in Fishing Gear
Incidental capture in fishing gear—primarily in longlines and trawls, but also in gill nets, purse seines, and hook and line—is a serious ongoing source of mortality that adversely affects the species' recovery.
Vessel Strikes
Vessel strikes can injure or kill sea turtles. Injuries or death may be caused by propellers and blunt force trauma from the vessel’s hull.
Ocean Pollution/Marine Debris
Marine turtles may die after ingesting fishing line, balloons, or plastic bags, which they can mistake for prey. They may also become entangled in marine debris and can be killed or seriously injured.
Scientific Classification
| Animalia |
Chordata |
Reptilia |
Testudines |
Cheloniidae |
Lepidochelys |
olivacea |
