Facts About Sea Turtles

Green Turtle, Maldives © Lisa Bauer

Sea turtles have been around for a really long time – since before the extinction of the dinosaurs 65 million years ago!  Sea turtles, also known as marine turtles, can be found in the waters of all the planet’s oceans, except in the Arctic.

There were once many species, but now we have only seven left: green, hawksbill, olive ridley, leatherback, loggerhead, kemp ridley and flatback. Sadly, six of the sea turtle species fall under IUCN’s category of being at risk of extinction. The seventh species, the flatback, is not listed due to lack of data and needs more research.

Below you will find answers to some of the most frequently asked questions we get about turtles.

Sea Turtles FAQ - The Answers to All Your Sea Turtle Questions

Sea turtles cannot breathe underwater, however they can hold their breath for long periods of time. Sea turtles can hold their breath for several hours depending on their level of activity. For instance, a resting turtle can remain underwater for 4-7 hours whereas a foraging individual may need to surface more frequently.

When turtles hold their breath, their heart rate slows significantly to conserve oxygen –  up to nine minutes may pass between heart beats! Despite this adaptation, a stressed turtle – such as one entangled in ghost net – will deplete oxygen stores rapidly and may drown within minutes if unable to reach the surface.

Hawksbill turtle resting on the reef, Maldives. A resting turtle can remain underwater for 4-7 hours, image
Hawksbill turtle resting on a reef, Maldives.
Marvin, hawksbill turtle, foraging in Maldives. A resting turtle can remain underwater for 4-7 hours whereas a foraging individual may need to surface more frequently, image
Hawksbill turtle foraging on coral, Maldives.

Reference

  • Long dive interval during hibernation: Hochscheid S, Bentivegna F & Hays GC 2005. First records of dive durations for a hibernating sea turtle. Biology Letters 1: 82-86.
  • Dive duration during activity: 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.

Yes, sea turtles can feel it when you touch their shell. Sea turtle shells consist of bones, which are covered by a layer of so-called scutes (plates). These scutes are made of keratin, the same material that human fingernails are made of. There are nerve endings enervating even the bones of the shell. These nerve endings are sensitive to pressure, for example from a touch on the back.

Drawing of green turtle shell showing 4 pairs of lateral scutes, graphic
Green turtle have 4 pairs of lateral scutes
A green turtle swimming in the blue ocean with four pairs of lateral scutes clearly visible on the shell, image
A green turtle with the lateral scutes clearly visible

References

  • Thomson JS 1932. The Anatomy of the Tortoise. Scientific Proceedings of the Royal Dublin Society.
  • Zangerl R 1969. The turtle shell. In: Gans C and Bellairs A (eds.): The Biology of Reptilia, Vol. 1: 311-319. Academic Press, New York.

No, sea turtles cannot retract their heads into their shells. Their bodies are well adapted to swimming with generally flatter shells as opposed to the high domed shells of tortoises. Sea turtles have the same muscles as other turtles, which allows them to pull back their heads, but there is simply not enough space in the shell to fully retract the head.

Green sea turtle on a reef in Kenya. Sea turtles have a flatter shell than tortoises and cannot retract their head into their shells.
Sea turtles have a flatter shell than tortoises and have no space to retract their head into their shell. Seen here a green sea turtle.
Tortoises have a domed shell that allows them to retract their head into their shell. Image of a Greek spur-thighed tortoise.
Tortoises have a domed shell that allows them to retract their head into their shell. Seen here a Greek spur-thighed tortoise.

References

Wyneken J 2001. The Anatomy of Sea Turtles: Part II. U.S. Department of Commerce NOAA Technical Memorandum NMFS-SEFSC-470, 53-112.Valente ALS, Cuenca R, Zamora M, Parga ML, Lavin S, Alegre F and Marco I 2007. Computed tomography of the vertebral column and coelomic structures in the normal loggerhead sea turtle (Caretta caretta). The Veterinary Journal 174: 362-370.

Sea turtles can survive in the wild with only three flippers as many sporadic sightings of turtles with such injuries show – they learn to adapt to a missing limb just like humans. If they are missing a front flipper, they learn to compensate by using their opposite back flipper when swimming, for example. We currently do not know if a missing limb is going to significantly influence the general life span of these turtles, as systematic studies are not easy to conduct.

One or two missing hindlimbs is going to have a great impact on female turtles, as they use these flippers to dig their nests. Unsuccessful digging can lead to abandoned nesting attempts.

Hawksbill turtle missing a front flipper swimming Baa Atoll Maldives
A Hawksbill turtle missing a front flipper, Baa Atoll, Maldives. © Chiara Fumagalli

References

  • Spotila JR & Tomillo PS (eds.) 2015. The Leatherback Turtle: Biology and Conservation. Johns Hopkins Press, Maryland, US.

Most barnacles do not hurt sea turtles, as they are only attached to the shell or skin on the outside. Others though burrow into the skin of the host and might cause discomfort and provide an open target area for following infections.

Excessive barnacle cover can be a sign of general bad health of a turtle. Usually sea turtles are debilitated first, and then become covered in an extensive amount of other organisms, such as barnacles and algae.

Luckily turtles are very resilient and can sometimes recover from such infestations.

Turtle with high barnacle cover on face Maldives
Hawksbill turtle Orimas with high barnacle cover ©Karin Nistler, Prodivers
Hawksbill turtle having recovered from high barnacle cover
Hawksbill turtle Orimas recovered from high barnacle cover ©Stephanie Köhnk

References

  • Monroe R & Limpus CJ 1979. Barnacles on turtles in Queensland waters with descriptions of three new species. Memoires of the Queensland Museum 19: 197-223.
  • Ross A & Frick MG 2007. From Hendrickson (1958) to Monroe & Limpus (1979) and Beyond: An Evaluation of the Turtle Barnacle Tubicinella cheloniae. Marine Turtle Newsletter 118: 2-5.

No. Once a nest has been laid, the female never returns to it. The eggs and hatchlings are left to fend for themselves and locate the water upon emerging.

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There are several theories as to how they locate this area, but none have yet been proven. The most common theories are:

  • They can detect both the angle and intensity of the earth’s magnetic field. Using these two characteristics, a sea turtle may be able to determine its latitude and longitude, enabling it to navigate virtually anywhere. Early experiments seem to show that sea turtles have the ability to detect magnetic fields. Whether they actually use this ability to navigate is the next idea being investigated.
  • It is believed that hatchlings imprint the unique qualities of their natal beach while still in the nest and/or during their trip from the nest to the sea. Beach characteristics used may include smell, low-frequency sound, magnetic fields, the characteristics of seasonal offshore currents and celestial cues.
  • Younger female turtles may follow older, experienced nesting turtles from their feeding grounds to the breeding site.

Reference

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 they measure 1.5 – 2m (4-6 ft) long and weigh 300 – 500 kg (660 to 1,100 lbs). The largest leatherback ever recorded was 3 m (9 ft) long and weighed 916 kg (2,019 lbs) !

Kemp’s Ridley: 55.6-66.0 cm carapace length, weight range of 25-54 kg for nesting females.

Reference:

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

Reference:

  • 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.

Leatherbacks:

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.

Reference:

  • 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.

There is no way to determine the exact age of a sea turtle from its physical appearance other than to establish if it is a juvenile or adult, depending on its size.

After it’s death, the age of a turtle can be determined by a technique called “skeletochronology”, whereby the humerus (arm bone) is examined. These bones reveal growth rings that allow the turtle’s age to be calculated, much like we can calculate the age of a tree.

Green-turtle-hatchling-Claire-Maldives-rescue-centre-ORP
Green turtle hatchling Claire – only 5 cm long
Euan, hawksbill turtle Maldives
Euan, a juvenile hawksbill turtle, 45 cm long
Hope-Olive-Ridley-baby-turtle-ORP-rescue-centre-Maldives
Baby Hope, a young juvenile olive ridley, 13 cm long
adult green turtle resting on the reef maldives
An adult green turtle

References

  • Snover ML 2002. Growth and ontogeny of sea turtles using skeletochronology: methods, validation and application to conservation. PhD Thesis, Duke University, USA.

Leatherbacks can dive to a depth of more than 1,000 meters (3,000 feet) in search of their prey, jellyfish. The hard-shelled species dive at shallower depths, typically up to 175 meters (500 feet) though olive ridleys have been recorded at over 200 meters (660 feet).

The leatherback is adapted to deep dives because it lacks a rigid breastbone. Its leathery shell also absorbs nitrogen, reducing problems arising from decompression during deep dives and resurfacing (i.e., “the bends”).

Green turtle diving, Maldives
Green turtle diving, Maldives
Aguadormi an identified Hawksbill sea turtle swimming in the blue Maldives
Hawksbill Turtle, Maldives

References

  • García-Párraga D, Crespo-Picazo JL, Bernaldo de Quirós Y, Cervera V, Martí-Bonmati L, Díaz-Delgado J, Arbelo M, Moore MJ, Jepson PD and Fernández A 2014. Decompression sickness (‘the bends’) in sea turtles. Diseases of aquatic organisms 111: 191-205.
  • 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.
  • McNahon CR, Bradshaw CJA and Hays GC 2007. Satellite tracking reveals unusual diving characteristics for a marine reptila, the olive ridley turtle Lepidochelys olivacea. Marine Ecology Progress Series 329: 239-252.

Just like other reptiles, sea turtles have lungs. They have a slightly different structure than mammalian lungs, but work just as well when it comes to exchanging gases (oxygen and carbondioxide). The lungs are located right under the carapace and the vertebral column.

Ventilation of the lungs (breathing) is achieved by movements of the muscles attached to the pelvic and shoulder girdles and to the plastron. You can sometimes see turtles ‘rocking‘ their shoulders when they are not underwater; this movement of the muscle masses around the shoulder also helps them breathe by changing the pressure inside the lungs.

Sea turtle coming up to breathe, image
Sea turtle coming up for air
Baby turtle Luna Luna coming up for air, image
Turtle patient, baby Luna, coming up for air

References

Wyneken J 2001. The Anatomy of Sea Turtles: Part II. U.S. Department of Commerce NOAA Technical Memorandum NMFS-SEFSC-470, 53-112.

The male climbs onto the female turtle’s back and holds on to her carapace with the long, sharp claws of his front flippers. The way he hooks on to the edge of the female’s shell often results in a scratched shell and bleeding wounds in the soft parts of her body. Copulation can take place on the surface or under water.

Both male and females’ reproductive organs are located at the base of their tails in their cloaca – a combined intestinal, urinary, and reproductive organ. Males have a very long tail while females have a short tail. The male’s penis is located in his cloaca. He reaches his tail underneath the posterior end of the female’s shell to inseminate her cloaca.

Read more about how sea turtles mate here.

 

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A pair of green sea turtles mating in Maldives. Video © Sasha Haslim

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

Climate change can impact sea turtles in various ways. Firstly, increasingly warm seas pose a threat to vital sea turtle habitats and food sources, such as coral reefs. Cooler ocean temperatures are associated with higher productivity, thus providing more food for many organisms – including sea turtles. Warmer oceans and less food available leads to decreased nesting activity and fewer sea turtles being born. These effects have been monitored in some populations, e.g. in the Western Pacific Ocean and Western Atlantic.

Secondly, sea level rise can be very detrimental for sea turtle nesting beaches and it can be increasingly difficult for turtles to find appropriate spaces to deposit their eggs. This will also lead to decreased nesting activity and fewer sea turtles being born.

In addition to that, the sex of a sea turtle is not determined purely genetically as it is in humans: the temperature during the development of the embryo will determine whether a male or a female turtle hatches. Higher temperatures result in females, lower in males. Increasing sand temperatures on nesting beaches can therefore shift the sex ratio of hatchlings to almost entirely female. As a result, turtles can have a problem reproducing in the future.

A juvenile hawksbill turtle looking for food at a bleached coral reef in Maldives. ©Kylie Merritt
Increased sand temperature on nesting beaches can shift the sex ratio of sea turtle hatchlings to almost entirely female. Green turtle hatchlings, Maldives, image
Increased sand temperature on nesting beaches can shift the sex ratio of sea turtle hatchlings to almost entirely female. ©Chiara Fumagalli

References

  • Abella Perez E, Marco A, Martins S and Hawkes L 2016. Is this what a climate change-resilient population of marine turtles looks like? Biological Conservation 193: 124-132.
  • Chaloupka M, Kamezaki N and Limpus C 2008. Is climate change affecting the population of the endangered Pacific loggerhead sea turtle? Journal of Experimental Marine Biology and Ecology 356: 136-143.
  • Fuentes MMPB, Limpus CJ and Hamann M 2011. Vulnerability of sea turtle nesting grounds to climate change. Global Change Biology 17: 140-153.Pike DA, Antworth RL and Stiner JC 2006. Earlier Nesting Contributes to Shorter Nesting Seasons for the Loggerhead Sea Turtle, Caretta caretta. Journal of Herpetology 40: 91-94.

In the Maldives, the turtles we observe on the reefs show extremely high site fidelity, meaning they do not, in general, move from reef to reef to find food but have a “home reef”.

Upon reaching maturity most species travel long distances every few years for a breeding migration (from their feeding grounds to their breeding sites and back). These migrations can be hundreds or thousands of kilometers and take several months.

The leatherback turtle can travel 16,000 km (10,000 miles) or more each year, crossing the entire Pacific Ocean in search of jellyfish, while loggerheads have been tracked traveling from Japan to Baja, a distance of 13,000 km (8,000 miles). The longest recorded green turtle migration was 3,979 km (2,472 miles) from Chagos to Somalia.

Sea turtles are generally slow swimmers traveling at a speed of 2.8 to 10 km/h (1.7 to 6.2 mp/h) with slight variation between the species.

The leatherback sea turtle has been recorded swimming as fast as 35 km/h (22 mph), according to the San Diego Zoo. This speed is usually just achieved during brief bursts, for example due to flight reactions.

References:

  • Eckert SA 2002. Swim speed and movement patterns of gravid leatherback sea turtles (Dermochelys coriacea) at St Croix, US Virgin Islands. Journal of Experimental Biology 205: 3689-3697.
  • Papi F, Luschi P, Croisio E and Hughes GR 1997. Satellite tracking experiments on the navigational ability and migratory behaviour of the loggerhead turtle Caretta caretta. Marine Biology 129: 215-220.

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.

It is difficult to predict the exact incubation time for turtle eggs. The hatching date depends on variables such as the temperature during incubation and the depth of the nest, for example.

In the Maldives, sea turtle nests incubate for approximately 49 to 62 days, whereas in colder regions around the world incubation can take up to 80 days.

Loggerhead turtle nest, Cap Verde, image
Loggerhead turtle nest, Cap Verde
Green turtle hatchlings in the Maldives emerge from their nest after between 49 and 62 days, image
Green turtle hatchlings in the Maldives emerge from their nest after between 49 and 62 days

References

  • Hudgins JA, Hudgins EJ, Ali K and Mancini A 2017. Citizen science surveys elucidate key foraging and nesting habitat for two endangered marine turtle species within the Republic of Maldives. Herpetology Notes 10: 463-471.
  • Matsuzawa Y, Sato K, Sakamoto W and Bjorndal KA 2002. Seasonal fluctuations in sand temperature: effects on the incubation period and mortality of loggerhead sea turtle (Caretta caretta) pre-emergent hatchlings in Minabe, Japan. Marine Biology 140: 639-646.

The number of eggs in a nest, called a clutch, varies by species. On average, sea turtles lay 110 eggs in a nest, averaging between 2 to 8 nests a season. The smallest clutches are laid by Flatback turtles, approximately 50 eggs per clutch. The largest clutches are laid by hawksbills, which may lay over 200 eggs in a nest.

Nesting Green Sea Turtle

While there is no particular season for green sea turtle nesting in the Maldives, on Six Senses Laamu and the surrounding islands it usually happens between March and August. This green sea turtle crawled on land early in the morning of the 26th of June and dug a nest to lay her eggs.When sea turtles come on land they are more vulnerable because they can only move very slowly and are not well adapted for life out of the water. It is critical to not disturb a sea turtle attempting to nest as she may otherwise abort and crawl back into the ocean. Once a turtle starts laying eggs however, she enters a trance-like state from which she can’t be disturbed. This gives us the opportunity to carefully approach her and collect data such as carapace size, number of eggs and ID-shots of the nesting turtle. Once finished, she thoroughly covers the egg chamber containing 70-125 eggs on average and crawls back down the beach into the ocean.What an amazing event to witness!#greenseaturtle #turtlenest #maldives #seaturtleconservationPacsafe Sea Turtle Conservancy SEE Turtles National Geographic OceanCare

Posted by Olive Ridley Project on Thursday, June 28, 2018
Video © Beth Faulkner, Manta Trust

It is very hard to say how many sea turtles are left. Sea turtles are not easy to count, so we use different methods to estimate population sizes.

How many sea turtles are left? One method of estimating turtle populations is to measure the annual number of nesting events in a population. Olive ridley arribada nesting event in Michoacan Mexico; image
An Olive Ridley arribada nesting event in progress in Michoacan, Mexico. © Susie Gibson

One such measure used is the annual number of nesting events in each population. Since turtles can lay more than one clutch per year, the number of nests does not directly translate to adult females in a population. Additionally, sea turtles do not reproduce every year. An average of 2-6 years (depending on the species) can pass between active reproduction for each female.

Scientists take several factors into account when they convert observed nesting activity into the estimated population size. These include remigration interval, proportion identified & resighted females, sex ratio etc. A recent publication evaluating this process recommends caution that our current overall estimates of population sizes might still be too optimistic.

Recent estimates show us that there are nearly 6.5 million sea turtles left in the wild with very different numbers for each species, e.g. population estimates for the critically endangered hawksbill turtle range from 83,000 to possibly only 57,000 individuals left worldwide. Kemp’s Ridley and Flatback turtles each with a very narrow distribution could have less than 10,000 individuals left for each species (medium estimates: 25,000 and 69,000 respectively).

In general it is best to evaluate conservation efforts by assessing trends. We can see that conservation measures are fruitful in certain areas, because the general numbers of observed turtle nests increased over the years, even though we do not have specific numbers for individual turtles in the area.

References

  • Casale P & Ceriani SA 2020. Sea turtle populations are overestimated worldwide from remigration intervals: correction for bias. Endangered Species Research 30: 141-151.
  • Mazaris AD, Schofield G, Gkazinou C, Almpanidou V & Hays GC 2017. Global sea turtle conservation successes. Science Advances 3.
  • Spotila JR 2004. Sea Turtles: A complete guide to their biology, behaviour, and conservation. John Hopkins University Press, Maryland, US.
  • Wallace BP 2020. How many sea turtles are there? SWOT Report XV: 41.

Barnacles are a highly specialized group of crustaceans. They have developed a sessile lifestyle as adults, attaching themselves to various substrates such as rocks, ships, whales or to sea turtles. Most commonly found barnacles on sea turtles belong to the genus Chelonibia, named after their host (Chelonia = turtle).

Initially, barnacles produce larvae. These early life stages are still mobile and facilitate further distribution. After the first six different so-called nauplius larvae, a seventh non-feeding larva develops: the cyprid. This is the stage which settles on a new substrate. The cyprid larvae has special attachment devices which allow it to hold onto the substrate, e.g. cup-shaped attachment organs on the antennae. Once settled, the barnacle develops into an adult and attaches in various ways: gripping the skin, cementing to the shell or boring into it.

Adult barnacles are filter feeders, thus benefit from a constant flow of water around them. As sessile creatures they can achieve that by a) settling in an area with pronounced water movement (e.g. close to shore) or b) settling on a moving substrate such as a sea turtle.

Even though barnacles are quite safely attached, barnacles actually are capable of moving as adults! They most likely achieve this through an extension of their cemented base as well as through muscle activity.

Most barnacles do not hurt sea turtles as they are only attached to the shell or skin on the outside. Others though burrow into the skin of the host and might cause discomfort and provide an open target area for following infections.

Excessive barnacle cover can be a sign of general bad health of a turtle. Usually sea turtles are debilitated first, and then become covered in an extensive amount of other organisms, such as barnacles and algae.

Luckily turtles are very resilient and can sometimes recover from such infestations.

Read more about Sea Turtle Hitchhikers – The Symbiotic Relationships of Sea Turtles here.

Green turtle with excessive barnacles, Oman, image
Green turtle with barnacles, Oman ©Zoe Cox
Sea turtle with a single barnacle, Maldives, image
Green turtle with a single barnacle, Maldives ©Stephanie Köhnk

References

  • Monroe R & Limpus CJ 1979. Barnacles on turtles in Queensland waters with descriptions of three new species. Memoires of the Queensland Museum 19: 197-223.
  • Moriarty JE, Sachs JA & Jones K 2008. Directional Locomotion in a Turtle Barnacle, Chelonibia testudinaria, on Green Turtles, Chelonia mydas. Marine Turtle Newsletter 119: 1-4.Zardus, JD & Hadfield MG 2004. Larval development and complemental males in Chelonibia testudinaria, a barnacle commensal with sea turtles. Journal of Crustacean Biology 24: 409-421.
  • Monroe R & Limpus CJ 1979. Barnacles on turtles in Queensland waters with descriptions of three new species. Memoires of the Queensland Museum 19: 197-223.Ross A & Frick MG 2007.
  • From Hendrickson (1958) to Monroe & Limpus (1979) and Beyond: An Evaluation of the Turtle Barnacle Tubicinella cheloniae. Marine Turtle Newsletter 118: 2-5.

Each sea turtle species feeds on a specific diet and all lack teeth. Loggerheads feed mainly on hard-shelled organisms such as lobsters, crustaceans, and fish. Green turtles are vegetarian and prefer sea grasses, while leatherbacks feed mostly on jellyfish. Hawksbills have a bird-like beak that is used to cut through soft coral, anemones and sea sponges. Olive ridleys are omnivorous, mostly eating jellyfish, snails, crabs, and shrimp but they will occasionally eat algae and seaweed as well.

Hungry hungry hawksbill

We can celebrate turtles every day of the week! Happy #TurtleThursday everyone. Did you know that hawksbill sea surtles get their name from the narrow, elongated head that tapers to a beak-like jaw?It allows them to forage in crevices in coral reefs where they feed mainly on sponges but also anemones, soft coral or jellyfish.Sometimes it seems like they get in too deep and even stuck searching for their favourite food!This juvenile hawksbill was filmed by Beth Faulkner during a research dive for the Manta Trust in Laamu Atoll. Neither divers nor a camera can distract this turtle when it's lunch time!#turtle #hawksbill #coralreef #underwater #maldives Pacsafe SEE Turtles Sea Turtle Conservancy National Geographic Six Senses Laamu Fourth Element OceanPositive

Posted by Olive Ridley Project on Thursday, July 5, 2018

Apart from the most obvious – swimming – sea turtles use their flippers for a variety of other things as well. During foraging, their flippers allow them to hold onto prey, swipe it aside to tear off bits or leverage against the substrate again to remove substantial parts of their food. Loggerhead and green  turtles have also been observed to use the forelimbs to remove sediment – so essentially to dig up their food.

Additionally, sea turtles use their flippers during mating & nesting. Male turtles hold onto the carapace of the female by hooking on with a large claw on each forelimb. Female turtles move up the beach, pulling with the forelimbs and pushing with the hindflippers. They use the hindlimbs to dig a nest, which is later closed & covered/hidden with the use of all four extremities.

A green turtle seen holding on to his female mating partner with his front flippers, image
A green turtle seen holding on to his female mating partner with his front flippers.© Nina Roth
A female olive ridley turtle digging a nest with her hind flippers, image
A female olive ridley turtle digging a nest with her hind flippers. © Susie Gibson

References

  • Fujii JA, McLeish D, Brooks AJ, Gaskell J & Van Houtan KS 2018. Limb-use by foraging marine turtles, an evolutionary perspective. PeerJ 6.
  • Spotila JR & Tomillo PS (eds.) 2015. The Leatherback Turtle: Biology and Conservation. Johns Hopkins Press, Maryland, US.


In the past 100 years, human demand for turtle meat, eggs, skin, and shells have reduced their populations. Destruction of feeding and nesting habitats and pollution of the world’s oceans are all taking a serious toll on the remaining sea turtle populations.

Many breeding populations have already disappeared, and some species are being threatened to extinction. The natural obstacles faced by young and adult sea turtles are staggering, but it is the increasing pressures from the presence of humans that are threatening their future survival.

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Sea turtles scratch their shells to clean them. This self-grooming behaviour helps them remove epibionts such as barnacles or algae. Excessive epibiont growth would otherwise impair the turtle’s movement and swimming ability.

Green turtle with excessive barnacles, Oman
Green turtle with barnacles, Oman ©Zoe Cox

References:

  • Frick MG and McFall G 2007. Self-Grooming by Loggerhead Turtles in Georgia, USA. Marine Turtle Newsletter 118: 15.
  • Schofield G, Katselidis KA, Dimopolous P, Pantis J and Hayes GC 2006. Behaviour analysis of the loggerhead turtles Caretta caretta from direct in-water observations. Endangered Species Research 2: 71-79.

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