Olive ridley sea turtle on beach. Photo: NOAA Fisheries
Olive ridley sea turtle on beach. Photo: NOAA Fisheries
About the Species
The olive ridley gets its name from the olive green color of its heart-shaped 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.
Olive ridley turtles are found throughout the world. The number of olive ridleys are greatly reduced from historical estimates (for example, 10 million olive ridleys in the Pacific Ocean), due to overexploitation for turtle meat and eggs. Bycatch in fishing gear and the direct harvest of turtles and eggs are the biggest threat facing olive ridleys.
NOAA Fisheries and our partners are dedicated to protecting and recovering olive ridley turtle populations worldwide. We use a variety of innovative techniques to study, protect, and recover these threatened and endangered populations. We engage our partners as we develop measures and recovery plans that foster the conservation and recovery of olive ridley turtles and their habitats. And we fund research, monitoring, and conservation projects to implement priorities outlined in recovery plans.
Population Status
Olive ridley turtles are found worldwide and listed under the Endangered Species Act. Their breeding colony populations on the Pacific Coast of Mexico are listed as endangered; all others are listed as threatened. According to the International Union for Conservation of Nature and Natural Resources Red List, there has been between a 30 to 50 percent reduction in global population size. Although some nesting populations have increased in the past few years or are currently stable, the overall reduction in some populations is greater than the overall increase in others.
In the western Atlantic Ocean, although there has been an 80 percent reduction in certain nesting populations since 1967, Brazil has seen an increase in their nesting population. In the eastern Atlantic Ocean, Gabon currently hosts the largest olive ridley nesting population in the region with 1,000 to 5,000 breeding females per year.
In the Pacific, large nesting populations occur in Mexico and Costa Rica. A single arribada nesting beach remains in La Escobilla, Mexico, where an estimated 450,000 turtles nest, and the Pacific coast of Costa Rica supports an estimated 600,000 nesting olive ridleys between its two major arribada beaches, Nancite and Ostional.
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 provides additional information on abundance and population trends for this species.
Protected Status
ESA Endangered
- Mexico's Pacific coast breeding populations
ESA Threatened
CITES Appendix I
Appearance
Olive ridleys look very similar to Kemp’s ridley sea turtles. The two species are the smallest of all sea turtles. Olive ridley turtles are an olive/grayish-green with a heart-shaped carapace (top shell) having 5 to 9 pairs scutes. 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.
Behavior and Diet
Olive ridley turtles, like all sea turtles, are marine reptiles and must come to the surface to breathe. Adult female sea turtles return to land to lay their eggs in the sand—they are remarkable navigators and usually return to a beach in the general area where they hatched.
Arribada nesting is a behavior found only in the genus Lepidochelys which includes the Kemp's ridley and olive ridley sea turtles. 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. 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.
Olive ridleys often migrate great distances between feeding and breeding grounds. Using satellite 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.
The olive ridley is omnivorous, meaning it feeds on a wide variety of food items, including algae, lobster, crabs, tunicates, and mollusks. Olive ridleys can dive to depths of 500 feet to forage on benthic invertebrates (those that live on the bottom).
Where They Live
The olive ridley is mainly a pelagic (open ocean) sea turtle, observed by trans-Pacific ships over 2,400 miles from shore, but they are also known to inhabit coastal areas. 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.
World map providing approximate representation of the olive ridley's range.
Lifespan & Reproduction
No one knows exactly how long olive ridleys live, but like other sea turtles, they are likely long-lived. Olive ridleys reach maturity around 14 years of age. 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.
Females nest every year, one to three times a season, laying clutches of approximately 100 eggs. 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. The sex of hatchlings is determined by the temperature of the sand, the eggs hatch and the hatchlings make their way to the water. Hatchlings orient seaward by moving away from the darkest silhouette of the landward dune or vegetation to crawl towards the brightest horizon. On developed beaches, this is toward the open horizon over the ocean.
Threats
Bycatch in Fishing Gear
A primary threat to sea turtles is their unintended capture in fishing gear which can result in drowning or cause injuries that lead to death or debilitation (for example, swallowing hooks or flipper entanglement). The term for this unintended capture is bycatch. Sea turtle bycatch is a worldwide problem. The primary types of gear that result in olive ridley bycatch include trawls, longlines, gillnets, and purse seines.
Direct Harvest of Turtles and Eggs
The principal cause of the worldwide decline of the olive ridley sea turtle was long-term collection of eggs and mass killing of adult females on nesting beaches. The arribada nesting behavior concentrates females and nests at the same time and in the same place, enabling the taking of an extraordinary number of eggs for human consumption. Historically, egg collection for human consumption was a significant problem, but this threat has been diminished in some countries with bans on the killing of turtles and collection of eggs.
Loss and Degradation of Nesting Habitat
Coastal development and rising seas from climate change are leading to the loss of nesting beach habitat for olive ridley turtles. Shoreline hardening or armoring (e.g., seawalls) can result in the complete loss of dry sand suitable for successful nesting. Artificial lighting on and near nesting beaches can deter nesting females from coming ashore to nest and can disorient hatchlings trying to find the sea after emerging from their nests.
Predation of Eggs and Hatchlings
The destruction and consumption of eggs and hatchlings by non-native and native predators (particularly feral pigs, coyotes, coatis, birds, and crabs) is a threat to olive ridley sea turtles.
Vessel Strikes
Vessel strikes are a threat to sea turtles near ports and waterways along developed coastlines throughout their range. Various types of watercraft can strike sea turtles when they are at or near the surface, resulting in injury or death. High boat traffic areas such as marinas and inlets present a higher risk. Adult sea turtles, in particular nesting females, are more susceptible to vessel strikes when making reproductive migrations and while they are nearshore during the nesting season.
Ocean Pollution/Marine Debris
Increasing pollution of nearshore and offshore marine habitats threaten all sea turtles and degrades their habitats. Olive ridley turtles may ingest marine debris such as fishing line, balloons, plastic bags, floating tar or oil, and other materials discarded by humans which they can mistake for food. They may also become entangled in marine debris, including lost or discarded fishing gear, and can be killed or seriously injured.
Climate Change
For all sea turtles, a warming climate is likely to result in changes in beach morphology and higher sand temperatures, which can be lethal to eggs or alter the ratio of male and female hatchlings produced. Rising seas and storm events cause beach erosion, which may flood nests or wash them away. Changes in the temperature of the marine environment are likely to alter the abundance and distribution of food resources, leading to a shift in the migratory and foraging range and nesting season of olive ridleys.
Scientific Classification
| Animalia |
Chordata |
Reptilia |
Testudines |
Cheloniidae |
Lepidochelys |
olivacea |
