Loggerhead Turtle

Loggerhead turtle returning to sea after nesting. Image.
Loggerhead turtle returning to sea after nesting. Boavista Cape Verde. © Stephanie Köhnk.

Loggerhead turtles (Caretta caretta) are named after their exceptionally large heads. They normally carry many encrusting organisms (epibionts), such as barnacles, on their head and carapace. 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.

Their heart-shaped carapace is orange to reddish-brown with a yellowish-brown plastron. They typically have five vertebral scutes down the carapace’s midline and five pairs of costal scutes along the borders.

Green Turtle Biology and Behaviour

Nesting loggerhead turtle. Image.
Adult female loggerehead turtle nesting. © Stephanie Köhnk.

The loggerhead turtle reaches sexual maturity at 15 to 30 years of age. There are no external differences between males and females until they reach sexual maturity. Adult males have longer tails and claws, and shorter plastrons. Males also have wider heads and wider and shallower carapaces. Their lifespan is thought to be 47-62 years.

Loggerhead turtles have a low reproductive rate. Females nest every two to three years at an average of four times per season. They lay between 40 and 190 eggs per clutch. Track marks measure 70 to 90 cm wide and have asymmetrical diagonal forelimb marks. The tail drag mark is usually absent.

Loggerhead Turtle Biology and Behaviour

Emme, a juvenile loggerhead, was brought to the Rescue Centre having been kept as a pet since she hatched. We have estimate her to be between 2-4 months old. Image.
Emme, a juvenile loggerhead sea turtle, was brought to the Rescue Centre having been kept as a pet since she hatched. We have estimate her to be between 2-4 months old.

Hatchlings have a light to dark brown carapace and light margins along their flippers. They measure 40-50 mm upon hatching.

Loggerheads spend around 85% of their day underwater. A normal dive is between two and 45 minutes depending in activity levels, but they can stay underwater for up to seven hours when hibernating. Loggerheads normally rest on the bottom of the sea, remaining motionless with their eyes half closed so that they are easily alerted. These are among the longest dives of any marine vertebrate.

Loggerhead Turtle Diet

Barnacle on loggerhead sea turtle. Image.
A loggerhead sea turtle with a barnacle on their face. © Kostas Papafitsoros.

Loggerheads have a more varied diet than any other species of sea turtle. Sponges, corals, sea urchins, squid, starfish, and even insects are on their menu. The loggerhead’s powerful jaws allow it to crush the hard shells of molluscs and crustaceans that inhabit the bottom of the ocean, such as giant clams and queen conches. They also feed on crabs, clams, mussels and other invertebrates. When they are migrating through open seas, loggerhead turtles feed on jellyfish, floating molluscs, fish eggs, and squid. Juvenile loggerheads prey on barnacles, crab larvae, fish-eggs, and hydrozoans living in Sargassum conches.

Loggerhead Habitat and Distribution

Loggerhead hatchling on the beach. Image.
Loggerhead hatchling on the beach. © Joana Hancock.

Loggerheads are distributed throughout the temperate and tropical regions of the Atlantic, Pacific, and Indian Oceans, as well as in the Mediterranean Sea. They can live in water as cold as 13°C. This species may be found in pelagic areas as well as in inshore areas such as bays, lagoons, salt marshes, creeks, and the mouths of large rivers. They frequently feed on coral reefs and in rocky areas, and, like all other marine turtles, they spend their entire lives at sea.

Loggerhead hatchlings find their way to mats of flotsam (often Sargassum seaweed) in the open ocean or in shallow estuaries, where they remain for the first 7-12 years of their lives. Recent studies suggest that they spend a lot of time on the surface in their first year. At this stage, they will migrate to nearshore coastal areas to forage and grow to maturity. Like other turtles, loggerheads migrate long distances between their foraging and nesting grounds. They appear to migrate along coastlines rather than cross open waters.

Loggerhead turtle, Oman.

Unlike other species of turtles, courtship behaviours do not take place near their nesting beaches, but along the way from the foraging grounds to the migration routes. Loggerheads nest on high-energy oceanic beaches and occasionally on estuarine shorelines. In the Northern Hemisphere, they nest between May and August, and in the Southern Hemisphere between October and March.

In the Indian Ocean, loggerhead turtles feed along the coasts of Africa, Oman, Yemen, and in the Arabian Sea. Loggerheads nest in few countries in the Indian Ocean, such as South Africa, Mozambique, Madagascar, Western Australia and Sri Lanka. However, the number of nesting females is generally small with the exception of Masirah Island in Oman, which is home to the second largest loggerhead population of the world.

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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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Deep dive into sea turtle science and conservation. Suitable for budding conservationists and those with an interest in the science surrounding turtles, their biology and conservation.

References

  • Baldwin R, Hughes GR and Prince RIT 2003. Chapter 14: Loggerhead Turtles in the Indian Ocean. In: Loggerhead Sea Turtles, Bolton AB and Witherington BE (eds.): 218-232. Smithsonian Books, Washington, USA.
  • 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.
  • Florida Fish & Wildlife Conservation Commission. Guidelines for Marine Turtle Permit Holders: Nesting Beach Surveys: Crawl Identification Guide. 2014.
  • Hochscheid S, Bentivegna F and Hays GC 2005. First records of dive durations for a hibernating sea turtle. Biology Letters1: 82-86.
  • 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.