Olive Ridley Turtle

Reptiles of Ecuador | Testudines | Cheloniidae | Lepidochelys olivacea

English common names: Olive Ridley Turtle, Olive Ridley Sea Turtle.

Spanish common names: Golfina, tortuga golfina, tortuga lora, tortuga olivácea.

Recognition: ♂♂ 72.3 mmThis is a measurement of the straight length of the carapace. ♀♀ 79 cmThis is a measurement of the straight length of the carapace.. Lepidochelys olivacea is unique among sea turtles found in Ecuador because it has 6–9 pairs of costal shields. Although adult males and females of this species have a similar body size, males are distinguished by their longer, thicker tails and larger front flipper claws, which they use to grasp females during copulation.

Natural history: Extremely common along the coast of mainland Ecuador, where it is the most common sea turtle species. Rare in Galápagos. After hatching on tropical beaches, hatchlings of Lepidochelys olivacea frantically swim for 1–3 days in an offshore direction until they reach open ocean "nursery" habitats where they spend several years actively swimming and drifting along with surface currents.1,2 During this early stage, the young L. olivacea spend 78% of the day diving at depths of 100–150 cm.2 At night, they spend most of their time floating on the surface.2 Around the world, Olive Ridley Turtle hatchlings are preyed upon by mammals (including whales, dogs, and coyotes), a variety of bird species, iguanas, lizards, snakes, Leatherback Sea Turtles (Dermochelys coriacea), crocodiles, sharks, fish, and crabs.3–5

After the semi-passive drifting post-hatchling life stage, juvenile and adult Olive Ridley Turtles become nomads of vast oceanic areas2 or establish their foraging ranges in 23–31 °C waters6,7 within 15 km of mainland shores.3 From this point onwards, the young Lepidochelys olivacea become opportunistic generalist2 predators of both deep water and surface prey,6 such as fish and their eggs, crustaceans (including crabs, lobsters, shrimp, and barnacles), sea urchins, molluscs (including squid, bivalves, and snails), jellyfish, bryozoans, planktonic tunicates, sea squirts, marine worms, and algae.6,8–10

Olive Ridley Turtles spend up to 98% of their time conducting 10–50 m deep dives near the sea bottom,11 although they can dive down to 290 m and for up to three hours.12 During the remaining time, they bask on the water surface.3 Some adults of Lepidochelys olivacea are residents of 138–1,260 km2 foraging home ranges in coastal waters.11 Others are mostly migratory. They use major oceanic currents6 to travel (probably using geomagnetic cues) up to 83 km per day13 to distant (up to 7,282 km away)6 rookeries, foraging grounds, or nesting beaches.

Olive Ridley Turtles becomes sexually mature at 13–16 years old.14,15 From this age on, they gather for months16 in polyandrous (a female copulates with more than one male)17 breeding rookeries in shallow waters 2–5 km from the nesting beaches.18 Here, copulation takes place at depths of 0–28 m.18 Hybridization between Lepidochelys olivacea and other sea turtle species such as Caretta caretta,19 Chelonia mydas,20 and Eretmochelys imbricata,21 occurs. Female Olive Ridley Turtles are capable of storing sperm throughout the breeding season,22 and in some populations 31–92% of the resulting clutches are sired by multiple males.23 They nest every 1–8 (but usually every 1–3) years3,24 on roughly (less than 5.6 km apart)25 the same beaches season after season, which may also be the same beaches on which they themselves hatched. Females may also sometimes select different beaches up to 320 km apart.24

Along the coast of mainland Ecuador but not in Galápagos, nesting females can be seen throughout the year, but most nest during the rainy season (from December to May) with a peak in February.26 Others migrate from Mexican and Central American nesting grounds to forage in large numbers in Ecuadorian waters about ~48–64 km from the coast.27

During a single season, females may lay 1–3 clutches3 at intervals of 4–75 (but usually 12–23) days.11,28 They produce 17–182 eggs per clutch3,29 and lay them on sandy beaches with high humidity levels.29 The eggs are laid in 21–69 cm deep30 nests in sand or soil,4 usually at night9,31 but also during the daytime.3 In Lepidochelys olivacea, nesting emergences last 45–60 minutes.4,32 The process may be solitary,23 as it is in Ecuador, or occur in huge in aggregations known as arribadas, with as many as ~800,000 females nesting over 7–8 consecutive nights.33 The incubation period is 48–70 days,4 and 0.8–88% of the eggs hatch.4,34 Temperature determines the sex of the offspring.35 The proportion of female hatchlings increases with incubation temperature.36

At nesting grounds throughout the world, eggs of Lepidochelys olivacea are preyed upon mostly by mammals (including pigs, dogs, dingoes, jackals, coyotes, hyenas, domestic cats, mongooses, raccoons, coatis, and opossums), but also by caracaras, caimans, crocodiles, lizards, snakes, crabs, and beetles.4,5,37 They are also occasionally lost to erosion,38 inundation,38 and disturbance by other nesting turtles.2 The eggs are also widely harvested for human consumption2 (although they may cause food poisoning).3 The eggs hatch synchronously and usually at night or late in the afternoon.39 During nocturnal emergence, the presence of artificial lighting affects the orientation of hatchlings, which may result in mortality caused by traffic, desiccation, and starvation.40

In addition to predation by sharks,41 large fish,42 crocodiles,43 whales,42 coyotes,3 and jaguars,44 causes of mortality of adult Olive Ridley Turtles include ingestion of plastic,45 collision with boats,26 interactions with fishing gear,46, direct harvesting for meat consumption (although their meat may cause food poisoning),3 and harvesting for the leather market.26 Individuals of Lepidochelys olivacea are parasitized by a variety of worms47 and leeches48 and colonized by barnacles, amphipod crustaceans, crabs, remoras, and hydrozoans.10,48,49 Turtles of this species are estimated to live up to 40 years.3

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Conservation: Vulnerable.50 Lepidochelys olivacea is listed in this category because its global populations have declined 31–36% over the past three generations as a result of direct harvesting of eggs and adults for meat, incidental mortality due to interactions with artisanal and industrial fisheries, and degradation of marine and nesting habitats.50 Another threat faced by L. olivacea is the increase of the average global temperature, which may result in the complete feminization of some populations and the large-scale mortality of embryos due to lethal field temperatures.51 Under some scenarios of global sea level rise, up to 43% of the area of some L. olivacea nesting beaches may be lost by 2100.52

In the waters off the coast of mainland Ecuador, Lepidochelys olivacea is also under threat. Olive Ridley Turtles make up the majority of the bycatch of artisanal fisheries in Ecuador.53 Additionally, they were the most heavily exploited sea turtle in the country during the 1970s, with ~100,000–148,000 individuals per year slaughtered for consumption and the leather market.26,54 Finally, enigmatic mass mortality events of Olive Ridleys attributed to several causes such as bycatch, sea surface temperature anomalies, and outbreaks/diseases have also been reported to have occurred along the Ecuadorian coast during the past decade.55

Distribution: Tropical and subtropical waters of the Atlantic, Indian, and Pacific oceans.

Distribution of Lepidochelys olivacea along mainland Ecuador Distribution of Lepidochelys olivacea in Galápagos

Etymology: The generic name Lepidochelys, which comes from the Greek words lepidos (meaning “scale”) and chelys (meaning “turtle”),56 is probably a reference to the scutes covering the carapace. The specific epithet olivacea, which comes from the Latin word oliva (meaning “olive tree”),56 refers to the color of the carapace.

See it in the wild: Although members of Lepidochelys olivacea nest along the coast of mainland Ecuador, roughly on the same beaches during the same months, witnessing such events is rare. However, swimming Olive Ridley Turtles can be seen with ~40–60% certainty while navigating on motorized boats off the coast of Machalilla National Park. However, this species cannot be expected to be seen reliably in Galápagos, since individuals transiting through the archipelago's waters are rarely spotted and there are no records of females nesting on the islands.

FAQ

How did the Olive Ridley Sea Turtle become endangered? The Olive Ridley Sea Turtle is considered to be facing a high risk of extinction in the mid-term future because its populations have declined 31–36% over the past three generations as a result of direct harvesting of eggs and adults for meat, incidental mortality due to interactions with fisheries, and degradation of marine and nesting habitats.50

How many eggs do Olive Ridley Sea Turtles lay? Olive Ridley Sea Turtles lay 17–182 eggs per clutch.3,29

What do Olive Ridley Sea Turtles eat? Olive Ridley Sea Turtles are generalist opportunistic predators. They feed on fish and their eggs, crustaceans, sea urchins, molluscs, jellyfish, bryozoans, planktonic tunicates, sea squirts, marine worms, and algae.6,8–10

What does arribada mean? Arribada is a mass nesting behavior of some sea turtle species such as the Olive Ridley Turtle in which thousands of females nest on the same beach over a short period of time. Arribadas do not take place in Ecuador, only solitary nesting.

Where is the Olive Ridley Sea Turtle found? Olive Ridley Sea Turtles occur in tropical and subtropical waters of the Atlantic, Indian, and Pacific oceans.

Which is the world's most important nesting beach for Olive Ridley Sea Turtles? Gahirmatha Beach in eastern India is the world's most important nesting beach for Olive Ridley Sea Turtles. As many as 800,000 females nest on this beach over 7–8 consecutive nights.33

Why do Olive Ridley Sea Turtles lay so many eggs? Olive Ridley Sea Turtles have evolved to lay many eggs in order to improve the chances of an egg hatching and surviving into adulthood, since the majority (up to 99%) of the hatchlings are likely to perish before reaching maturity.

Why do Olive Ridley Turtles migrate? Olive Ridley Turtles routinely migrate between feeding and breeding areas because the most productive feeding grounds are usually not near the most suitable nesting beaches. Breeding gatherings may last months16 and usually take place in areas where food is scarce. Thus, the turtles spend most of their remaining time growing their energy reserves in distant feeding grounds.

Authors: Alejandro ArteagaaAffiliation: Khamai Foundation, Quito, Ecuador. and Juan M GuayasaminbAffiliation: Laboratorio de Biología Evolutiva, Universidad San Francisco de Quito (USFQ), Quito, Ecuador.,cAffiliation: Galapagos Science Center, Galápagos, Ecuador.,dAffiliation: Centro de Investigación de la Biodiversidad y Cambio Climático, Universidad Tecnológica Indoamérica, Quito, Ecuador.

Academic reviewers: Juan José Alava.

Photographers: Alejandro ArteagaaAffiliation: Tropical Herping (TH), Quito, Ecuador.

How to cite? Arteaga A, Guayasamin JM (2020) Lepidochelys olivacea. In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: www.reptilesofecuador.com

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