Hawksbill Turtle

Keno, haksbill turtle, with raised flipper. Image.
Keno, hawksbill, Baa Atoll, Maldives.

The hawksbill turtle (Eretmochelys imbricata) gets its name from its narrow, elongated head that tapers sharply to a V-shaped lower jaw. Its other prominent feature is the saw-like appearance of its shell margins. The hawksbill is one of the smaller species of marine turtles, with adults measuring about 70-95.5 cm in length and weighing 70-86.2 kg.

Nesting females in most Indian Ocean populations tend to be smaller than their Pacific and Atlantic counterparts, with females measuring 70 cm and weighing 44 kg, on average. Males and females tend to be around the same size, but males may have longer claws and brighter colouring.

The carapace of the hawksbill is unique amongst the sea turtles as the scutes overlap. It has five central and four pairs of lateral scutes on its carapace. These scutes are streaked and marbled with amber, yellow, black, or brown and the turtle has a yellowish plastron.

Hawksbill Turtle Biology and Behaviour

Juvenile hawksbill swimming over colourful reef, Maldives. Image.
Brownie, juvenile hawksbill, on a reef in North Malé Atoll, Maldives.

Hawksbills reach maturity at a certain size, which is highly variable between nesting populations and might vary from 66 to 95 cm carapace length. It might take them anywhere from less than 10 to around 30 years to reach that size, depending on food availability.

They mate approximately every 2 years in secluded lagoons off their nesting beaches. Females may nest 2 to 5 times per season. In the Indian Ocean, the female lays an average of 100 to 180 eggs per nest, depending on the turtle population, and each nest takes about 60 days to incubate. Female hawksbills seem to prefer nesting in vegetation at the back of beaches. Track marks are about 70 to 85 cm wide, shallow, and have asymmetrical (alternating) forelimb marks. Tail marks may be present or absent.

Juvenile hawksbill ghost gear victim with beautiful shell. Image.
The beautiful shell of Ash, a juvenile hawksbill and previous patient at the ORP Marine Turtle Rescue Centre in the Maldives.

Hatchlings weigh around 25 g and are 40 mm long at birth. The hatchlings have a light-brown, heart-shaped shell, which elongates with age. Their life span remains unknown. Hawksbills often rest in caves or under ledges around reefs during the day and prefer to return to the same spot night after night to rest.

Hawksbill Turtle Diet

Hawksbill sea turtle foraging on a reef, Baa Atoll, Maldives. Image.
Hawksbill turtle foraging on a reef, Baa Atoll, Maldives.

The hawksbill’s narrow head and beak-like jaw shape allows them to forage in crevices in coral reefs. They feed mainly on sponges, but anemones, soft corals, urchins, jellyfish, squid, and shrimp are also in their diet. Both sessile and mobile animals are eaten and hawksbills appear to be opportunistic predators. Juvenile hawksbills eat sargassum seaweed as well as prey that can be found within the floating algae mats such as fish eggs, crabs, and other invertebrates.

Hawksbill Turtle Habitat and Distribution

Juvenile hawksbill turtle, North Male Atoll, Maldives.
Sonny, juvenile hawksbill turtle, Maldives.

This species can be found throughout the central Atlantic and Indo-Pacific regions; in fact, these two populations are sufficiently different to be considered subspecies. Post-hatchling hawksbills occupy the pelagic environment, taking shelter under algal mats accumulating at convergence points.

Hawksbills recruit to coastal foraging areas when they reach approximately 20-25 cm in length (around 1-4 years of age). This shift in habitat also involves a shift in feeding strategies: from feeding primarily at the surface to feeding on animals associated with coral reef environments below the surface.

Hawksbill turtle swimming in Ha Kelaa Atoll, Maldives. Image.
Hawksbill turtle swimming in Ha Kelaa Atoll, Maldives.

Adults forage almost exclusively on coral reefs and are seldom seen foraging in waters deeper than 20 metres. Once a convenient feeding area is located, hawksbills remain loyal to that site, moving only when there is increased competition, decreased food availability, or to make their nesting migrations.

Like other marine turtles, the hawksbill makes long nesting migrations and nests on both low- and high-energy beaches. Thanks to their small body size and great agility, they can traverse fringing reefs inaccessible to other species. They often nest on small, isolated islands and sometimes on mainland coasts.

Hawksbill coming up to breath, Maldives. Image.
Hawksbill coming up to breath, Maldives.

Although generally not found in large concentrations, hawksbills are widely distributed across the Indian Ocean. Nesting density is low throughout their global range and many populations are now severely depleted, though new, previously unknown, nesting populations were recently discovered in the central Pacific. In the Indian Ocean, larger nesting populations occur in the Seychelles, Australia and Oman. Smaller nesting populations can be found in the Lakshadweep Islands, The Andaman and Nicobar Island, Chagos Archipelago, Saudi Arabia, the Maldives and Madagascar.

c Expand All C Collapse All

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.

Learn More About Sea Turtles – Free Online Courses

Free

e-Turtle School – All About Sea Turtles

Everything you have ever wanted to know about sea turtles, from evolution to conservation. Suitable for all sea turtles lovers and those who want to learn more about these fascinating creatures.
Free

Sea Turtle Science & Conservation

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:

  • 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.

Learn More About Sea Turtles – Free Online Courses

Free

e-Turtle School – All About Sea Turtles

Everything you have ever wanted to know about sea turtles, from evolution to conservation. Suitable for all sea turtles lovers and those who want to learn more about these fascinating creatures.
Free

Sea Turtle Science & Conservation

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

  • 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.
  • Spotila JR 2004. Sea Turtles: A Complete Guide to Their Biology, Behaviour and Conservation. The John Hopkins University Press, Baltimore, USA.
  • Witzell WN 1983. Synopsis of biological data on the hawksbill turtle, Eretmochelys imbricata (Linnaeus, 1766). No. 137. Food & Agriculture Org.

We use cookies. For more info see our Cookie Policy

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.

Close