Olive Ridley Turtle
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.
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
- Mexico's Pacific coast breeding populations
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 [link to profile in Drupal] 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.
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 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.
Olive ridley turtles are protected under the Endangered Species Act (ESA). The breeding colony on the Pacific Coast of Mexico is listed as endangered, while all other olive ridleys are listed as threatened. This means that the olive ridley turtle is in danger of extinction, now or in the foreseeable future, throughout all or a significant portion of its range. NOAA Fisheries is working to protect this species in many ways, with the goal that populations will increase worldwide.
In the United States, NOAA Fisheries and the U.S. Fish and Wildlife Service (U.S. FWS) have joint jurisdiction for sea turtles, with NOAA having the lead in the marine environment and U.S. FWS having the lead on the nesting beaches. Both federal agencies, along with many state agencies and international partners, have issued regulations to eliminate or reduce threats to sea turtles, while working together to recover them.
Recovery Planning and Implementation
To help identify and guide the protection, conservation, and recovery of sea turtles, the ESA requires NOAA Fisheries and U.S. FWS to develop and implement recovery plans, in close coordination with stakeholders, for each listed sea turtle species. Recovery plans provide a blueprint for conservation of the species and measurable criteria to gauge progress toward recovery.
The major recovery actions for olive ridley sea turtles include:
Support efforts of Mexico and the countries of South America to protect turtles and eggs on nesting beaches.
Protecting nesting and foraging habitats.
Reducing bycatch in commercial and recreational fisheries.
Reducing the effects of entanglement and ingestion of marine debris.
Working with partners internationally to protect turtles in all life-stages in foreign waters.
The recovery plan to recover and protect the U.S. Pacific populations of the olive ridley turtle was published in 1998.
The highly migratory behavior of sea turtles makes them shared resources among many nations, so conservation efforts for sea turtle populations in one country may be jeopardized by activities in another. This means that protecting sea turtles on U.S. nesting beaches and in U.S. waters alone is not enough to ensure the continued existence of the species. Learn more about international conservation efforts below.
NOAA Fisheries is working to minimize effects from human activities that are detrimental to the recovery of olive ridley turtle populations in the U.S. and internationally. Together with our partners, we undertake numerous activities to support the goals of the olive ridley turtle recovery plan, with the ultimate goal to delist the species.
Efforts to conserve olive ridley turtles include:
Rescue, disentanglement, and rehabilitation.
Eliminating the harvest of turtles and their eggs.
Eliminating the harassment of turtles on nesting beaches through education and enforcement.
Consult with federal agencies to ensure their activities are not likely to jeopardize the continued existence of listed species.
To reduce the incidental capture of sea turtles in commercial fisheries, we have enacted regulations to reduce bycatch in certain U.S. commercial fishing gears (gillnets, longlines, pound nets, and trawls) that have known bycatch of sea turtles. Measures include:
Changes to fishing practices.
In the Gulf of Mexico, NOAA Fisheries has worked closely with the shrimp trawl fishing industry to develop turtle excluder devices (commonly called TEDs) to reduce the mortality of sea turtles incidentally captured in shrimp trawl gear. TEDs that are large enough to exclude even the largest sea turtles are now required in shrimp trawl nets.
Since 1989, the U.S. has prohibited the importation of shrimp harvested in a manner that adversely affects sea turtles. The import ban does not apply to nations that have adopted sea turtle protection programs comparable to that of the U.S. (i.e., require and enforce the use of TEDs) or to nations where bycatch in shrimp fisheries does not present a threat to sea turtles (for example, nations that fish for shrimp in areas where sea turtles do not occur). The U.S. Department of State is the principal agency of this law, while we serve as technical advisor. We provide extensive TED training throughout the world.
We are also involved in cooperative gear research projects, implementation of gear mitigation technologies, and safe handling protocols designed to reduce sea turtle bycatch and mortality in the Gulf of Mexico and Atlantic pelagic longline fisheries, the American Samoa and Hawaii-based longline fisheries, the Atlantic sea scallop dredge fishery, the Chesapeake Bay pound net fishery, and non-shrimp trawl fisheries in the Atlantic and Gulf.
Bycatch in fishing gear is the primary anthropogenic source of sea turtle injury and mortality in U.S. waters. The most effective way to learn about sea turtle-fishery interactions is to place observers aboard fishing vessels. Under the ESA, NOAA Fisheries identifies commercial and/or recreational fisheries in the Atlantic Ocean, Gulf of Mexico, and Pacific Ocean that are required to have observers to record sea turtle interactions. The purpose of observing these fisheries is to:
Learn more about sea turtle interactions.
Evaluate measures to reduce fisheries impacts/bycatch of protected sea turtles.
Determine whether additional measures may be necessary to prevent sea turtle bycatch.
NOAA Fisheries determines which fisheries are required to carry observers to monitor potential interactions with sea turtles through an annual determination. Observers may also be placed on fisheries through our authorities under the Magnuson-Stevens Act.
Sea Turtle Stranding and Response
A stranded sea turtle is one that is found on land or in the water dead, injured, sick, or exhibiting usual behavior. One of the most well-known examples of mass strandings is when cold-stunned sea turtles strand during winter months on the Atlantic and Gulf coasts. During these events, thousands of turtles may require care.
The Sea Turtle Stranding and Salvage Network was established in response to the need to better understand the threats sea turtles face in the marine environment, to provide aid to stranded sea turtles, and to salvage dead sea turtles that may be useful for scientific and educational purposes. The network collects information on and documents strandings of marine turtles along the U.S. Gulf of Mexico and Atlantic coasts and includes federal, state, and private partners. This information is compiled into a centralized database.
NOAA’s Pacific Islands Fisheries Science Center’s Marine Turtle Biology and Assessment Program rehabilitates and studies stranded sea turtles throughout the Hawaiian Islands. Other state and local organizations respond to sea turtle strandings on the U.S. West Coast.
The actions taken by stranding network participants improve the survivability of sick, injured, and entangled turtles while also helping scientists and managers to expand their knowledge about diseases and other threats that affect sea turtles in the marine environment and on land.
The conservation and recovery of sea turtles requires international cooperation and agreements to ensure the survival of these highly migratory animals. We have a broad national and international program and work closely with partners under two international environmental agreements that deal exclusively with sea turtle conservation:
Additional international treaties and agreements include:
Convention on International Trade in Endangered Species (CITES): Listed in Appendix I, which prohibits international trade of wild flora and fauna.
Cartagena Convention: Protected under Annex II of the Specially Protected Areas and Wildlife (SPAW) Protocol.
The Mexican government has played a vital role in the conservation of the olive ridley sea turtle. In 1990, Mexico declared a total ban on killing sea turtles, outlawing the harvest of turtles and turtle eggs.
The olive ridley turtle was listed under the ESA in1978. The breeding populations in the Pacific coast of Mexico are listed as endangered—all other olive ridleys are listed as threatened.
In 1992, we finalized regulations to require turtle excluder devices (TEDs) in shrimp trawl fisheries to reduce interactions between turtles and trawl gear. Since then, we have changed these regulations as new information became available on increasing the efficiency of TEDs. For example, larger TEDs are now required to exclude larger turtles.
We have implemented additional measures to reduce sea turtle interactions in fisheries through regulations and permits under both the ESA and Magnuson-Stevens Fishery Conservation and Management Act including the use of large circle hooks in longline fisheries, time and area closures for gillnets, and modifications to pound net leaders. See all regulations to protect sea turtles.
We also conduct regular, 5-year reviews of species recovery plans to evaluate our progress in meeting the recovery goals:
For more information, please visit our regulations to protect marine turtles page.
Regulatory Actions & Documents
NOAA Fisheries conducts various research activities on the biology, behavior, and ecology of the olive ridley sea turtle. The results of this research are used to inform management decisions and enhance recovery efforts for the endangered and threatened olive ridley populations.
Turtle population assessments ideally include information on the species’ abundance and distribution, life history, and human impacts. This information can help us evaluate the effectiveness of conservation and recovery measures, and can help guide actions to enhance recovery. To estimate population abundance, researchers conduct aerial and vessel-based surveys of selected areas and capture and mark turtles in the water and on beaches. We also incorporate data collected on nesting beaches, via stranding networks, and from fisheries observer programs. Other information that informs sea turtle population assessments includes population structure (genetic analyses), age to maturity, survivorship of the various life stages (e.g., hatchling, juvenile, adult), foraging and reproductive behavior, movement and distribution, and habitat studies.
Tagging and Tracking Studies
Satellite telemetry allows researchers to track sea turtles as they swim from place to place. These satellite tags are designed and attached in a manner that minimizes disturbance to the turtle. The tags will eventually fall off. The data help us understand migration patterns, identify feeding areas, and identify where turtles overlap with their primary threats (e.g., fishing gear).
Fishing Gear Research
We engage in the development, evaluation, and modifications of fishing gear to promote sea turtle conservation while at the same time retaining a sustainable fisheries catch. This work includes TED development, use of circle hooks in longline fisheries, time and area closures for gillnets, and modifications to pound net leaders.
Sea Turtle Genetics
NOAA Fisheries’ National Sea Turtle Molecular Genetics Center serves as a worldwide central depository for sea turtle tissue and DNA samples and constitutes a major area of research supporting sea turtle conservation. For example, a turtle’s unique genetic “fingerprint” can be used to determine its nesting population and home nesting beach.
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