Olive Ridley Turtle

Turtle patient Heidi, ghost gear victim
Heidi, a male olive ridley sea turtle and ghost gear victim.

The olive ridley turtle (Lepidochelys olivacea) is the smallest and most abundant of all sea turtles, growing up to 80 cm and weighing less than 50 kg. The olive ridley gets its name from its heart-shaped, olive green coloured carapace. Males and females grow to the same size; however, females have a slightly more rounded carapace. The olive ridley turtle has 5 to 9 pairs of costal scutes and either one or two claws on each flipper. Indian Ocean olive ridley turtles are, on average, smaller than individuals found in the Pacific and the Atlantic.

Biology and Behaviour

Female olive ridley nesting on the beach during arribada. Image.
Female olive ridley turtle nesting on the beach during arribada ©Susie Gibson

Olive ridley turtles reach sexual maturity at approximately 15 years of age, an early age compared to other sea turtles. Many females nest every year, some even twice a season. They lay clutches of approximately 100-110 eggs, which take from 45 to 65 days to hatch. The nesting female leaves track marks that are 70-80 cm wide and have asymmetrical forelimb marks. Tail drag marks are absent. Olive ridley turtles use three different strategies to nest: arribadas, solitary nests and mixed strategy.

Olive ridleys on the beach during arribada. Image.
Olive ridley arribada ©Susie Gibson

An arribada is a mass-nesting event when thousands of turtles come ashore at the same time to lay eggs on the same beach. More commonly, olive ridley turtles nest in a dispersed way (individual nesters are not synchronous). In certain places, some females can use both strategies. The time period between nesting events is approximately 14 days for solitary nesters and 28 days for arribada nesters.

Olive ridley sea hatchling leaving the nest. Image.
Olive ridley hatchling. ©Susie Gibson

Olive ridley hatchlings are charcoal grey with a greenish hue along their sides. They measure around 38 mm long and weigh 17g at birth.

Olive Ridley Turtle Diet

Injures Olive Ridley Turtle being fed at ORP Marine Rescue Centre
An olive ridley turtle patient being fed tuna at the ORP Marine Turtle Rescue Centre in Maldives

Olive ridley turtles have a varied diet, eating algae, lobsters, crabs, tunicates, jellyfish, shrimp, fish, and fish eggs. They can dive to depths of over 200 metres to find food are opportunistic feeders in the open ocean, eating just about anything they can find.

Habitat and Distribution

Olive ridley turtle nesting during arribada event, Mexico. Image.
A female olive ridley turtle nesting during an arribada event in Mexico ©Susie Gibson

The olive ridley turtles are globally distributed in the tropical and warm-temperate regions of the South Atlantic, Pacific, and Indian Oceans. Though mainly pelagic, they have been found to inhabit coastal areas, including bays and estuaries. Olive ridleys often migrate thousands of kilometres between pelagic feeding and coastal breeding grounds. In fact, fishermen have spotted adult olive ridleys over 4,000 km from land in the Pacific.

Little is known about the juvenile stage of the olive ridley. However, it is thought to spend its first few years floating in oceanic currents and foraging for planktonic plants and animals. Satellite tracking studies of female olive ridleys nesting in Bangladesh show that they travel widely in the Bay of Bengal, coming very close to the coasts of India and Sri Lanka. The tracking of rehabilitated turtles released from the Maldives shows that they travel with the predominating currents, either east towards Sri Lanka and India, or north through the Lakshadweep Islands and into the Arabian Sea. Despite the enormous number of olive ridleys that nest in Orissa, India, this species is not commonly seen throughout much of the Indian Ocean.

Olive Ridley Turtles In The Maldives

Olive ridley sea turtle pulling ghost gear under water Maldives
Entangled olive ridley turtle in Maldives

There are very few documented records of olive ridley turtles nesting in the Maldives. Olive ridleys appear to be most commonly sighted offshore and most of the recorded turtles were either sub-adults or adult females. Though previous studies report no particular season for encountering olive ridley turtles in the Maldives, more recent data suggest that this species is most often seen entangled in ghost nets between January and April. The turtles are likely on their way to or from their nesting beaches in India and Sri Lanka and encounter marine debris along the way.

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Sea Turtle FAQ – The Answers to All Your Sea Turtle Questions

Male hawksbill popping head above surface for air, Maldives. Image.
Marvin, male hawksbill, coming up for a breathe, Maldives.

Sea turtles can hold their breath for several hours, depending on their level of activity.

If they are sleeping, they can remain underwater for several hours. In cold water during winter, when they are effectively hibernating, they can hold their breath for up to 7 hours. This involves very little movement.

Although turtles can hold their breath for 45 minutes to one hour during routine activity, they normally dive for 4-5 minutes and surfaces to breathe for a few seconds in between dives.

However, a stressed turtle, entangled in a ghost net for instance, quickly uses up oxygen stored within its body and may drown within minutes if it cannot reach the surface.

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References:

  • Hays GC, Akesson S, Broderick AC, Glen F, Godley BJ, Luschi P, Martin C, Metcalfe JD & Papi F 2001. The diving behaviour of green turtles undertaking oceanic migration to and from Ascension Island: dive durations, dive profiles and depth distribution. Journal of Experimental Biology 204: 4093-4098.
  • Hays GC, Hochscheid S, Broderick AC, Godley BJ & Metcalfe JD 2000. Diving behaviour of green turtles: dive depth, dive duration and activity levels. Marine Ecology Progress Series 208: 297-298.
  • Hochscheid S, Bentivegna F & Hays GC 2005. First records of dive durations for a hibernating sea turtle. Biology Letters 1: 82-86.
  • Lutz PL and Musik JA (eds.) 1996. The Biology of Sea Turtles Volume I. CRC Press.

The actual documentation of a sea turtle’s age in the wild is difficult or nearly impossible. Individual turtles can be tracked for a shorter time of six month to three years with the help of satellite transmitters. Longterm studies rely on capture-recapture principle, just like our turtle photo id project. Each photo of a turtle represents a recapture event documenting that the individual is still alive.

A study of nesting green turtles in Hawaii observed female turtles returning to nest for up to 38 years after they were first identified. Assuming the average age at first nesting activity of 24 years, this would show that green turtles can live to up to at least 62 years.

Similar estimates have been made for loggerhead turtles.

An adult green turtle resting on a reef in Maldives, image
An adult green turtle
Hawksbill turtle resting on the reef, Maldives
An adult hawksbill turtle

References:

  • Dodd C 1988. Synopsis of the biological data on the loggerhead sea turtle. Ecology 88.
  • Humburg IH and Balazs GH 2014. Forty Years of Research: Recovery Records of Green Turtles Observed or Originally Tagged at French Frigate Shoals in Northwestern Hawaiian Islands, 1973-2013. NOAA Technical Memorandum NMFS-PIFSC-40.

When sea turtles are juveniles, it is very difficult to tell their sex by eye as they do not differ externally. However, after reaching sexual maturity male sea turtles develop a long tail, which houses the reproductive organ. The tail may extend past the hind flippers.

Female turtles have a short tail, which generally doesn’t extend more than 10 cm (4 inches) past the edge of the carapace. Male sea turtles (except leatherbacks) have elongated, curved claws on their front flippers to help them grasp the female when mating.

The sex of a sea turtle embryo is determined by the temperature of the sand: warm temperatures result in more females while cooler temperatures result in more males.

Male green turtle tail
Male green turtle tail
Female green turtle tail
Female green turtle tail

The olive and Kemp’s ridley sea turtles are the smallest species, growing only to about 70 cm (just over 2 feet) in shell length and weighing up to 45 kg (100 lbs). Leatherbacks are the largest sea turtles. On average leatherbacks measure 1.5 – 2m (4-6 ft) long and weigh 300 – 500 kg (660 to 1,100 lbs). The largest leatherback ever recorded was 2,56 m (8.4 ft) long and weighed 916 kg (2,019 lbs) !

Kemp’s Ridley

Nesting female kemp's ridley turtle, nicknamed
Nesting female kemp’s ridley turtle, nicknamed “Mij”, laying 116 eggs on Galveston’s East Beach. ©Ron Wooten, Wildscreen Exchange.

55.6-66.0 cm carapace length, weight range of 25-54 kg for nesting females.

References:

  • Marquez-M R 1994. Synopsis of Biological Data on the Kemp’s Ridley Turtle, Lepidochelys kempi (Garman, 1880). NOAA Technical Memorandum NMFS-SEFSC-343.

Olive Ridley

Female Oliver ridley turtle nesting on the beach during arribada
Nesting female olive ridley turtle ©Susie Gibson.

Curved carapace length 52.5-80.0 cm, weight less than 50 kg (average 35.7 kg) for nesting females.

References:

  • Qureshi M 2006. Sea turtles in Pakistan. In: Shanker K and Choudhury BC (Eds.). Marine Turtles of the Indian Sub- continent. Heydarabad: India Universities Press, pp. 217–224.Reichart HA 1993.
  • Reichart HA 1993. Synopsis of biological data on the olive ridley sea turtle Lepidochelys olivacea (Eschscholtz 1829) in the western Atlantic. NOAA Technical Memorandum NMFS-SEFSC-336.

Hawksbills

Adult male hawksbill turtle swimming in the blue, Maldives. Image
Adult male hawksbill, Maldives.

Nesting females reported between 53.3 and 95.5 cm carapace length, with weight between 27.2 and 86.2 kg.

References:

  • Witzell WN 1983. Synopsis of biological data on the hawksbill turtle, Eretmochelys imbricata (Linnaeus, 1766). No. 137. Food & Agriculture Org.

Green turtles

Adult green turtles mating, Malsdives. Image.
Adult green turtles mating, Maldives.

Nesting green females reported curved carapace length 75-134 cm, weight (after egg deposition) 45-250 kg (!).

References:

  • Hirth HF 1997. Synopsis of the Biological Data on the Green Turtle Chelonia mydas (Linnaeus, 1758). Vol. 2. Fish and Wildlife Service, US Department of the Interior.

Flatbacks

Nesting flatback sea turtle ©Lyndie Malan / CC BY-SA.

Ones study (Ref. 1) found nesting females have a mean curved carapace length 86.3 cm, and mean weight of 67.4 kg. Another study (Ref. 2) found flatbacks to be between 87.5-96.5 cm.

References:

  • Schäuble C, Kennett R and Winderlich S 2006. Flatback Turtle (Natator depressus) nesting at Field Island, Kakadu National Park, Northern Territory, Australia, 1990-2001. Chelonian Conservation and Biology 5: 188-194.
  • Limpus CJ 1971. The Flatback Turtle, Chelonia depressa Garman in Southeast Queensland, Australia. Herpetologica 27: 431-446.

Loggerheads

Adult female loggerhead, Oman.

Adult loggerhead turtles measure between 65 and 115 cm in curved carapace length and typically weigh between 40 and 180 kg. The largest recorded loggerhead weighed 545 kg and measured 213 cm in presumed total body length. On average, nesting, and therefore adult, female loggerheads have a curved carapace length of 65.1-114.9 cm and weigh between 40.0 and 180.7 kg. Males fall into the same size range (79.0-104.0 cm curved carapace length).

References:

  • Brongersma LD 1972. European Atlantic turtles. Zoologische Verhandlingen 121, Leiden.
  • Dodd C 1988. Synopsis of the biological data on the loggerhead sea turtle. Ecology 88: 1-119.
  • Ernst CH and Lovich JE 2009. Turtles of the United States and Canada, 2nd edition. John Hopkins University Press.

Leatherbacks

Leatherback Turtle, Claudia Lombard, USFWS
Adult leatherback turtle ©Claudia Lombard, USFWS.

143.8-169.5 cm curved carapace length, weight 259-506 kg recorded for nesting females all around the world. Largest ever recorded specimen was found dead on a beach on the coast of Wales. The adult male turtle weighed 916 kg and its shell was 256.5 cm long. An autopsy revealed that it had drowned.

References:

  • Eckert KL and Luginbuhl C 1988. Death of a Giant. Marine Turtle Newsletter 43: 2-3.
  • Eckert KL, Wallace BP, Frazier JG, Eckert SA and Pritchard PCH 2012. Synopsis of the Biological Data on the Leatherback Sea Turtle (Dermochelys coriacea). Biological Technical Publication BTP-R4015-2012, US Fish & Wildlife Service.

Each sea turtle species feeds on a specific diet and all lack teeth:

  • Flatbacks are mainly carnivorous turtle feeding in shallow waters on soft bottoms.
  • Green turtles are vegetarian and prefer sea grasses, sea weeds and algae as adults, however, green turtle hatchlings are omnivorous, eating jellyfish, snails, crabs, and shrimp.
  • Hawksbills have a bird-like beak that is used to cut through soft coral, anemones and sea sponges.
  • Kemp’s ridleys are omnivores at the beginning of their lives, feeding on seaweed and small creatures like crabs and snails. As adults, Kemp’s ridleys look for food on the seabed, feeding on crustaceans, fish, molluscs, squids and jellyfish.
  • Leatherbacks feed mostly on jellyfish.
  • Loggerheads feed mainly on hard-shelled organisms such as lobsters, crustaceans, and fish.
  • Olive ridleys are omnivorous, mostly eating jellyfish, snails, crabs, and shrimp but they will occasionally eat algae and seaweed as well.

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References

  • Florida Fish & Wildlife Conservation Commission. Guidelines for Marine Turtle Permit Holders: Nesting Beach Surveys: Crawl Identification Guide. 2014.
  • Hudgins J, Mancini A and Ali K 2017. Marine turtles of the Maldives – A Field Identification Guide. Gland, Switzerland: IUCN and Government of Maldives. 90 pp.
  • Islam MZ, Akonda AW, Ehsan F and Adnan R 2016. Community based sea turtle monitoring and conservation project in Bangladesh. Proceedings – The Rufford in-country conference – Sri Lanka: 15-17.
  • McNahon CR, Bradshaw CJA and Hays GC 2007. Satellite tracking reveals unusual diving characteristics for a marine reptile, the olive ridley turtle Lepidochelys olivacea. Marine Ecology Progress Series 329: 239-252.
  • Qureshi M 2006. Sea turtles in Pakistan. In: Shanker K and Choudhury BC (Eds.). Marine Turtles of the Indian Sub-continent. Heydarabad: India Universities Press, pp. 217-224.
  • Reichart HA 1993. Synopsis of biological data on the olive ridley sea turtle Lepidochelys olivacea (Eschscholtz 1829) in the western Atlantic. NOAA Technical Memorandum NMFS-SEFSC-336.
  • Spotila JR 2004. Sea Turtles: A Complete Guide to Their Biology, Behaviour and Conservation. The John Hopkins University Press, Baltimore, USA.
  • Tripathy B 2008. An Assessment of Solitary and Arribada Nesting of Olive Ridley Sea Turtles (Lepidochelys olivacea) at the Rushikulya Rookery of Orissa, India. Asiatic Herpetological Research 11: 136-142.
  • Whiting SD, Long JL, Hadden KM, Lauder ADK and Koch AU 2007. Insights into size, seasonality and biology of a nesting population of the Olive Ridley turtle in northern Australia. Wildlife Research 34: 200-210.