Leatherback Turtle

Leatherback Turtle © Claudia Lombard, USFWS
Leatherback Turtle © Claudia Lombard, USFWS via Flicker CC BY 2.0

The largest of all the sea turtle species (and the largest living reptile) – the leatherback turtle (Dermochelys coriacea) – owes its name to its unique shell, which is composed of a layer of tough, rubbery skin strengthened by a matrix of thousands of tiny bone plates that look almost like a jigsaw puzzle. It is the only marine turtle without a hard carapace and without claws on its flippers.

Its leathery, dark grey to black carapace is mottled with white spots and marked by five ridges, and the plastron is cream to black in colour. The leatherback’s body is teardrop-shaped and tapers at the hind end to a blunt point. As a result, the shell is very hydrodynamic.

The largest ever recorded leatherback, an adult male, measured 256.5 cm in length and weighed 916 kg. Mature males and females today rarely reach a comparable size, on average measuring between 143 and 170 cm curved carapace length and weighing 259-506 kg. Leatherbacks mature between 8 and 15 years of age and are estimated to have a life span of around 45 years in the wild, but this is not well documented.

Leatherback Turtle Biology and Behaviour

Leatherbacks have a patch of pink skin on the top of their heads. Each spot, like our fingerprint, is unique. Although scientists are not sure about the function of this spot, they think that it might help the turtle sense light or determine where it is geographically.

Leatherback oesophagus ©Mdomingoa via Wikimedia Commons, CC BY-SA 4.0

Like all marine turtles, leatherbacks do not have teeth. Instead, they have two pointed cusps on their upper jaw and one on their lower jaw to help grasp their prey. Additionally, the leatherback’s oesophageal tract is lined with sharp, downward pointing spines. These are thought to prevent prey from escaping once caught, and to help shred food before it reaches their stomach.

Unlike other sea turtle species, female leatherbacks may use different nesting beaches from year to year (though they tend to stay in the same region). Because of their size, females prefer open-access beaches with a deep-water approach and soft sand. Leatherbacks usually nest every two to three years and from six to nine times per season. Females leave track marks about 150-200 cm wide, with symmetrical flipper marks and a deep median tail groove.

Leatherback hatchling scrambling to the water. ©Joana Hancock. Image.
Leatherback hatchling scrambling to the water. ©Joana Hancock.

Laying a nest takes the female from 1.5 to two hours, as she is extremely slow and clumsy on land. A clutch consists of an average of 61-104 eggs, with 22-46 % smaller, yolk-less and unfertilised eggs. Scientists are not sure about the function of these yolk-less eggs, but they think that they might prevent sand from falling between the fertile eggs, which allows more oxygen to circulate around them. Incubation takes about 65 days.

Hatching are around 50-75 mm long when born, and they are black with white along the flipper margins and the ridges down their back.

Leatherback Turtle Diet

Jelly fish, Kenya. Image
Jelly fish in Kenya. ©Joana Hancock

Leatherback turtles have delicate, scissor-like jaws, and feed exclusively on soft-bodied animals. A leatherback’s diet consists almost entirely of jellyfish, but they may also eat salps; gelatinous free-swimming marine invertebrates with transparent barrel-shaped bodies. They rarely feed on tunicates and cephalopods such as squid and octopus. This type of turtle can eat around 73% of its own body weight in jellyfish every day, packing in around 16,000 calories. That is around three to seven times more than they actually need to survive and allows them to fuel their long migrations.

Leatherback Turtle Habitat and Distribution

Leatherback turtle hatchlings emerging from nest
Leatherback turtle hatchlings © Elise Peterson Wikimedia Commons

As the most migratory and wide-ranging of all marine turtles, leatherbacks may have the widest global distribution of any vertebrate species on the planet. They inhabit the Atlantic, Pacific, and Indian Oceans, from the Gulf of Alaska to the waters of Tasmania. Even though the leatherback turtle is the least common turtle species in the Indian Ocean, important nesting populations exist in Indonesia, South Africa, Sri Lanka, and India’s Andaman and the Nicobar Islands.

Leatherbacks are powerful swimmers and regularly travel enormous distances, crossing entire ocean basins. However, very little information is available on the movements of leatherbacks in the Indian Ocean. Mostly pelagic in nature, leatherback turtles are also forage in temperate coastal waters. They travel from their tropical breeding and nesting grounds to find their favourite prey: jellyfish.

Scientists have a poor understanding of the distribution and developmental habitats of juvenile leatherbacks. However, it is thought that they remain in coastal tropical waters (above 26°C) until reach about one metre in length. Sightings of juvenile leatherback turtles are very rare. The leatherback’s pelagic habits make it especially at risk of interactions with fisheries, particularly longlines. Additionally, leatherback turtles cannot swim backwards. This means that once they become entangled in a net or line, they have little chance of escaping from it.

Leatherback turtles can dive to depths of over 1,200 metres, much deeper than any other marine turtle. They can stay underwater for up to 85 minutes, though a typical dive only lasts 3 to 8 minutes.

Leatherback Turtles in the Maldives

In the Maldives, the leatherback turtle is known as “musimbi”, which means Mozambique, and sightings are very rare. There are no confirmed nesting events in the last 100 years.

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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

  • 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 Pubication BTP-R4015-2012, US Fish & Wildlife Service.
  • Florida Fish & Wildlife Conservation Commission. Guidelines for Marine Turtle Permit Holders: Nesting Beach Surveys: Crawl Identification Guide. 2014.
  • Houghton JDR, Doyle TK, Davenport J, Wilson RP and Hays GC 2008. The role of infrequent and extraordinary deep dives in leatherback turtles (Dermochelys coriacea). The Journal of Experimental Biology 211: 2566-2575.
  • 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.
  • Spotila JR 2004. Sea Turtles: A Complete Guide to Their Biology, Behaviour and Conservation. The John Hopkins University Press, Baltimore, USA.
  • Stewart KR, Martin KJ, Johnson C, Desjardin N, Eckert SA and Crowder LB 2014. Increased nesting, good survival and variable site fidelity for leatherback turtles in Florida, USA. Biological Conservation 176: 117-125.