6. What do sea turtle eggs look like?
They are the size and shape of ping-pong balls with a soft shell. Usually eggs are spherical in shape, although occasionally, they are mis-shaped (elongated or adjoined with calcium strands). Some sea turtles lay small infertile eggs, which only contain albumin (egg white). The Leatherback turtle lays some of these small eggs in every clutch, whereas the other species of sea turtle lay these eggs infrequently.

7. What determines the sex of a sea turtle?
The temperature of the nest determines a hatchlings sex. This is called ‘temperature -dependent sex determination’ (TSD). Warmer temperatures produce mostly females, and cooler temperatures produce a majority of males. There is a pivotal temperature that produces an equal ratio of males and females. The temperature determining sex ratio differs between species and nest locations.

8. Do mother turtles attend to their nests?
No, once a nest has been completed, the female never returns to it. The eggs and resulting hatchlings are left to fend for themselves and locate the water upon emerging.

9. Why do hatchlings emerge together?
As hatchlings are so small, and the egg chambers from which they emerge are deep (between 30cm to 1m+ depth, depending on species), it would be impossible for a single hatchling to escape from the chamber alone. As hatchlings break free from their eggs inside the egg chamber, they stimulate other hatchlings to emerge from their eggs simultaneously. Once most hatchlings have emerged from their shells, they climb on top of the discarded eggshells. Hatchlings higher up the egg chamber scratch down sand from above and around them. The hatchlings make use of this sand and the discarded eggshells, like an elevator and ascend the egg chamber. Hatchlings beneath push those above out of the egg chamber. They emerge en masse or in small groups. Emerging together increases the chance of survival as many hatchlings can overwhelm would-be predators. A single hatchling would be an easy meal.

10. Which species nest in the Mediterranean?
Three species are found in this region: Loggerheads, Greens and Leatherbacks, but only Loggerhead and Green turtles nest here. The Leatherback is an occasional visitor to the waters of the Mediterranean, but does not nest there.

11. How do hatchlings and adults locate the ocean?
Sea turtles are ‘phototactic’, meaning that they are attracted to light, and so head towards the brightest light, which in nature is the moonlight reflecting on the sea, or the white surf line. They orientate themselves towards the seaward (bright) horizon. Turtles avoid shadows, including vegetation at the back of the beach, places where danger could lie.

12. What do sea turtles eat and do they have teeth?
Each species feeds on a diet specific to that species. For example, Loggerheads feed mainly on hard-shelled organisms such as lobsters, crustaceans, and fish, Green turtles prefer sea grasses and Leatherbacks feed exclusively on jellyfish. Plastic bags are often mistaken by turtles for jellyfish and are eaten. Plastic may accumulate inside a turtles gut and make the turtle feel full, when in fact it is hungry, this may result in starvation. Plastic may also lead to suffocation. Although Green sea turtles jaws are serrated, all sea turtles jaws lack teeth. The Leatherbacks jaw has 2 prominent “cusps” on the upper jawbone, distinguishing it from the other turtles.

13. How deep can sea turtles dive?
Leatherbacks can dive to a depth of more than 1000m in search of their prey, jellyfish. The smaller species are unable to dive to such great depths. The Leatherback is adapted to deep dives because of its unique morphology. Unlike other sea turtles, the Leatherback lacks a rigid breastbone/ lower chest, allowing the chest to collapse during deep dives. There is a large amount of oil in the skin and the Leathery shell absorbs Nitrogen, reducing problems arising from decompression during deep dives and resurfacing.

14. How long can a sea turtle hold its breath? And why do they drown?
As sea turtles are air breathing reptiles, they need to surface to breathe. Sea turtles can hold their breath for several hours, depending upon the level of activity. A resting/sleeping turtle can remain underwater for over 4-7 hours. Recent research has shown that some turtles can even hibernate in the sea for several months! However, a stressed turtle, for instance entangled in fishing gear, quickly uses up oxygen stored within its body and may drown within minutes through panic.

15. How big was the largest sea turtle ever recorded?
The largest species of sea turtle was the Archelon, which measured 7m in length and lived in Prehistoric times. Today, the largest living species is the Leatherback. There are 2 sub-species, the Pacific Leatherback and the Atlantic Leatherback. The Atlantic Leatherback is slightly larger than the Pacific population. Leatherbacks measure an average of just less than 2m in carapace (shell) length. The largest Leatherback ever recorded was a male found stranded (washed ashore) on the Welsh coast in 1987. He measured almost 3m (291cm) from tip to tail and weighed 970 kilos.

16. What are the main threats to Mediterranean sea turtles?
Anthropogenic (human caused) threats are numerous and include degradation and/or loss of nesting habitat, sand compaction through driving vehicles on nesting beaches, sand raking and/or removal, marine pollution and disease, incidental catch by fisheries (specifically shrimp trawlers and long lines), boat strike by speeding boats, tourism development, etc. Currently, the biggest threat to sea turtles is fishing activity, with incidental catches of thousands of turtles each year.

17. Which species is most common in the Mediterranean?
The Loggerhead is the most common species. The largest nesting assemblage is on the Greek Island of Zakynthos, on a private nesting beach of less than 600 metres. This beach is the most densely nested Loggerhead beach in the World, with almost 200 emergences recorded every night during peak nesting season!

18. How are sea turtles tracked in the ocean and how long can they be tracked for?
Researchers track sea turtles through a process called “satellite telemetry”. A transmitter (small computer) is attached to the turtle’s carapace (on hard shelled species) or is worn as a ‘backpack’ (fastened around) a Leatherback. The transmitter emits signals of information to an orbiting satellite when the turtle surfaces to breathe or bask. The information in the signals is de-coded prior to being forwarded to receiving stations on Earth, and then it is sent to the researchers computer as a dataset. This data provides information on the turtle’s location, number of dives during the last day, length of the most recent dive, water temperature, etc. Data received over a period allows for tracking a turtles movement patterns and swimming speed. Usually, satellite transmitters are attached to gravid (egg bearing) females that come ashore to nest. Tracking has provided important information on migration routes between breeding and foraging (feeding) habitats. Length of tracking depends upon how long the device remains on the turtle (they may be knocked off or fall off) and on battery life. Tracking usually continues for 6-10 months, although cases have been reported exceeding 2 years.

19. How and why are sea turtles identified?
Both external and internal markers (tags) are used to enable the identification of a specific individual. External tags are made from metal (monel or inconel) or plastic. Internal tags are called “Passive Integrated Transponder tags” or “PIT tags”. These are microchips consisting of metal and glass. Both external and internal tags display a unique series of letters and numbers, a bar code, eg, ZA214. External tags are clipped onto the turtles’ flipper(s), and are clearly visible to the eye. On the back of flipper tags is the address of the organisation applying the tags. Tags found can be returned with details of date and location when found together with information on the turtle, e.g., whether it was nesting, dead, etc. PIT tags are more expensive and only visible through the use of expensive scanning equipment, which when held over a PIT tag, displays the tag code. Only one PIT tag is needed for each animal and is injected into the turtles shoulder muscle. They are more secure than external tags as they cannot fall off and get lost. By using tags information can be collected on where the turtle was tagged, the number of nests constructed in a season, growth rates, fecundity, etc.

20. What is a Remora?
A remora is a pelagic (open ocean) fish found in warmer areas. Remoras attach themselves to sea turtles and other marine animals through a suction disc located on the top of their head. As they lack a swim bladder, attaching themselves to larger marine animals enables them to travel through the oceans. They are not parasites. They remove parasitic organisms and pose no threat to their host. For this reason, they are referred to as a type of “cleaner” fish.

21. Do sea turtles ever lay eggs underwater?
Sea turtles lay eggs (oviposit) on sandy beaches. Their eggs breathe air through their membranes and so cannot survive if they are continuously covered with water. Nesting turtles sometimes abandon nesting if they are disturbed and are scared back to sea, but they usually try to nest again elsewhere later that night or within 1-2 days of the failed attempt. Turtles disturbed during several nesting attempts may abort their eggs in the sea if they can’t carry them any longer. Once a clutch of eggs is ripe, they must be deposited, to allow for development of another clutch. Captive turtles have been known to drop eggs into the water.

22. Do sea turtles court before mating?
Most sea turtle studies have focused on land when the females nest, for ease of observation. Little research has been conducted in the sea, so there is limited knowledge on their behaviour in the water. It is known that sea turtle “courtship” usually occurs offshore the nesting beach. Males approach any female turtle, and occasionally logs, and scuba divers who resemble the females! Several males compete for the same female. She mates with them during the breeding season, and has the ability to retain their sperm from one season to the next. She uses the sperm of several males to fertilise her clutches, increasing the gene pool. Further studies are needed on courtship behaviour.

23. What are the white organisms attached to sea turtles and their tags?
The white organisms may be a type of barnacle (a crustacean, which at the adult stage attaches itself to a solid surface). They are often found attached both to the hard and soft parts of a sea turtle and/ or their flipper tags. Biologists are researching into whether barnacles negatively affect sea turtles. Their presence can make tag reading difficult, or impossible.

24. How do scientists determine how a turtle died?
Cause of death can be determined by conducting a ‘necropsy’. This is a turtle’s autopsy. By removing the outer shell of the turtle, the inner organs can be studied in detail. Although external trauma may be obvious through direct observation, e.g., shell breakage, limb amputation, bite marks, etc., necropsies allow observation of otherwise unseen, internal trauma, e.g., disease, refuse presence (plastic), etc.

25. What is the importance of sea turtles? Why try to conserve them?
Sea turtles are one of the longest living groups of animals to have ever existed, having far outlived the Dinosaurs. They have existed for approximately 200m years, and survived perfectly well until human activities placed them under increasing pressure. They act as environmental indicators. When populations are healthy (disease is uncommon), it reflects on the health of their marine habitat. They feed on a variety of organisms, e.g., Hawksbills eat sponges and corals, providing space for reef colonisation by other organisms, increasing species diversity. They feed other organisms, e.g., insects, crabs, fish, etc. which prey upon them at various life stages. Nutrients turtles produce through digestion feed other organisms. They provide a habitat for an array of animals including cleaner fish, and various barnacle species, some of which are exclusive to sea turtles. Sea turtles are an intricate part of their ecosystem. If they are wiped out, many organisms dependant upon them will also be affected.
Sea turtles make substantial nutrient and energy contributions to beaches, promoting plant growth, stabilising beach and dune systems. Green sea turtles graze seagrass beds, increasing the productivity of those areas. Leatherback turtles are major jellyfish predators, providing natural ecological control of jellyfish populations. If the decline in sea turtle populations is allowed to continue, it could have severe consequences on many marine and terrestrial plant and animal species that depend on sea turtles for their survival.
Furthermore, sea turtles are a flagship species, which means they are a species chosen to represent an environmental cause conserving the marine ecosystem and wildlife. Chosen for their charismatic nature, distinctiveness and vulnerable status, sea turtles engender public support and thus assist leverage of the entire ecosystem and associated species.

26. What are arribadas? What are names and locations of some beaches where arribadas occur?
"Arribada" means 'arrival' in Spanish. It describes a mass-nesting event of the ridley sea turtles. Such an event occurs when large numbers of turtles have gathered off shore to form a "flotilla". Then they emerge from the sea en masse and nest synchronously over the course of 3 - 7 days.

There used to be arribadas with 40, 000 + turtles on one beach on one day in Mexico in the early 1960's. Sadly today, although they do still occur, numbers have decreased dramatically, mainly through poaching, to only a few thousand nesting females. In other areas numbers have dwindled to the point where arribadas no longer occur on beaches that used to experience them.

Today, arribadas occur in places such as Ostional, Costa Rica, Rancho Nuevo, Mexico and Devi, India.

27. What species interact with loggerhead sea turtles?
Although sea turtles are solitary animals, Loggerheads have been known to visit cleaning stations where omnivorous fish feed on the micro-organisms found on turtles soft and hard body surfaces. Fish also feed on resting turtles.

28. What is the diet of sea turtles in the Mediterranean?
Loggerhead turtles generally feed on both plants and animals but they are mainly carnivorous. Their diet contains various species of algae, including Sargassum weed, which as hatchlings they also utilize as a 'float'. After emerging from their nests, leaving the beach, and moving into the open sea, they drift into deeper water which carries them into the Sargassum weed. This weed provides them with cover from would be predators and collects floating objects including zoo and phytoplankton which they feed on.

Loggerheads jaws are adapted to eating hard objects, such as crabs, barnacles, Lobster, bivalves, whelks, conchs and sea urchins. They can easily crush the hard shells of these animals. They also feed on sponges, jellyfish, shrimp, fish and fish eggs, as well as on a variety of plants, so they are classed as generalists.

Unfortunately, loggerheads also eat waste products such as plastic and rope, which they mistake as food items.

29. Which animals prey on eggs and hatchlings on nesting beaches?
The animals that prey on hatchlings in the Mediterranean depend on the location but include seagulls, crabs (particularly Ghost crabs), red foxes and fish. In addition to these natural predators, stray dogs also pose a threat.

Eggs are predated on by red foxes, rats, raccoons, dogs, and insects, including various species of fly larvae (maggots). Birds and crabs become predators following exposure of the eggs by the mammals mentioned above.

30. Do hatchlings bond with each other?
Sea turtles are solitary animals. Although they hatch together in large numbers, and make use of each other to ascend the nest, they enter the sea alone. They do not leave a beach in a group, but are transported by the waves to wherever the current flows. Sometimes they may be found together floating in a 'sargassum', or some other 'raft', however they remain solitary. Sea turtles may congregate at feeding grounds or developmental habitats, but solely for the purpose of feeding on the food sources present. When turtles are held in captivity as hatchlings, they do not appear to 'bond' with each other. When larger turtles are held in one tank they can be aggressive towards one another and will bite.

31. Is there a relationship between body size and clutch size?

Flatback turtles (endemic to Australia) produce small clutches, much smaller than those of other turtle species. This is likely due to their shell shape being flatter and therefore narrower than other sea turtle species. Soft shelled Leatherbacks produce relatively small clutches compared to the smaller hard-shelled sea turtles, they are the largest of all sea turtles. Clutch size has been found to have a positive relationship with shell size in Green turtles and in some populations of Loggerheads. With Olive ridleys there is a positive relationship between clutch size and shell size. This relationship makes sense because the larger the body size, the more space there is for eggs to develop internally. Sea turtles basically become egg producing machines during the breeding season, and have several clutches developing at a given time. However, body to clutch size relationships vary, even within a nesting season a turtle may lay clutches of varying size.

32. Can sea turtles be kept as pets?
All species of sea turtle are classified on the IUCN Red List as threatened or endangered. As such, it is illegal to handle them or to keep one as a pet. Specific permits (under CITES-Convention of International Trade in Endangered Species) are required to handle a sea turtle or its products and to house them legally (usually in Aquariums or Rescue Centres, which should provide adequate facilities to properly care for them). It would be very difficult for a member of the public lacking training and required facilities to correctly care for a sea turtle. Anyone discovered by the authorities to be keeping a sea turtle as a pet or in inappropriate conditions is liable for prosecution.

33. Can sea turtles survive in fresh water??
When in captivity, sea turtles should be maintained in water with a salinity level falling within a range of that of normal, natural, incoming seawater. Short periods of holding sea turtles in fresh water can be tolerated and are useful when prescribed by a veterinarian, e.g., to remove parasites and fouling epibiota such as barnacles. However, prolonged periods in fresh water should not be encouraged. Sea turtles are meant for life in the sea, so they do best in an environment with a similar salinity.

34. Are there any diseases in sea turtles that are transferable to humans and vice versa?
Numerous bacterial infections have been identified from sea turtles. One type of bacteria that is transferable between turtle and humans is Salmonella, present in all turtles (land, fresh water and sea turtle species). It is advisable when handling a sea turtle to wear latex gloves or if not available, to thoroughly wash hands both before handling the turtle to rid of any bacteria on our hands, and after handling to rid of any bacteria on the turtle. Sea turtles are highly sensitive creatures that are well adapted to their sea environment, but are easily stressed when they come into contact with man made pollutants, such as agricultural pesticide runoff. Currently, one of the biggest threats to Green turtles in particular is a disease called "Fibropapillomatosis" or "FP" for short, although it has more recently been observed in other species of sea turtle. This is directly linked with areas of high levels of human activity and high levels of pollution.

35. How can sea turtles be aged?
Patterns of growth rates in sea turtles have been difficult to assess, mainly because of a lack of methods available to age them. Techniques have been developed more recently that estimate age from the number of growth layers of bones. The humerus, one of the forelimb bones, gives the best indicator of age as they retain the greatest number of growth layers. There are limitations using growth layers for aging. In mature turtles, early growth layers are re-adsorbed, growth rates may not be constant and they are not necessarily annual. Growth studies have been conducted where a fluorescent chemical has been injected into adult sea turtles. When these turtles are located years later, the humerus has been examined beneath a microscope during biopsy, and growth layers are clear and countable. Unfortunately, this technique has not been used on young turtles, so unless the turtles age is known for definite, these techniques will only ever provide estimates. Techniques for using bones to determine age are complicated, but are described in detail in articles included in the Bibliography. Currently there is no accurate technique available for aging sea turtles only methods for estimation are described in literature.

36. How are sea turtle nesting beaches and migration routes discovered?
Discovering potential sea turtle nesting beaches has been a component of MEDASSET's work in the Mediterranean for over 25 years now in countries such as Libya, Lebanon, Syria and Egypt. Sea turtles select their specific nesting site through a complex procedure involving a multitude of factors, including many natural ones (e.g. geomorphology, beach inclination, moisture content, sea and sand temperature, sand compactness). The process of finding nesting beaches involves scientific assessments of beaches, investigating the many natural factors and assessing whether human impact could be a deterrent (presence of boats, lights, noise, pollution, development etc.). Speaking with the local community and fisherman can provide insight into whether nesting occurs now or whether it has in the past.

Sea turtle's migration routes can be found using satellite tracking from an electronic transmitter fitted on the turtle's carapace. To see some sea turtle migration routes please visit: http://www.seaturtle.org/tracking/

Beyneto, S. and Delcroix, E. (2005).
Underwater Oviposition by a Hawksbill Turtle in Guadeloupe,
French West Indies. Marine Turtle Newsletter 107:14.
http://www.seaturtle.org/mtn/archives/mtn107/mtn107p14.shtml

Bjorndal, K.A. (1995). Biology and Conservation of Sea Turtles (Revised Edition). Smithsonian Institution Press, Washington, USA.
Caribbean Conservation Corporation and Sea Turtle Survival League. (2003). How Tracking Sea Turtles by Satellite Works.
http://www.cccturtle.org/satintro.htm

Eckert, K.L, Bjorndal, K.A., Abreu-Grobois, F.A. and Donnelly, M. (Editors). (1999). Research and Management Techniques for the Conservation of Sea Turtles. IUCN / SSC Marine Turtle Specialist Group Publication No. 4.

Fleming, E.H. (2001). Swimming Against the Tide: Recent Surveys of Exploitation, Trade, and Management of Marine Turtles in the Northern Caribbean. TRAFFIC North America, USA.

Hays, G., Houghton, J.D.R., Crafton I., King, R.S, Lloyd, C. & Lovell, P. (2004). First records of oceanic dive profiles for leatherback turtles, Dermochelys coriacea, indicate behavioural plasticity associated with long-distance migration. Animal Behaviour, 67, 733 – 743.
Available on line at: http://www.turtle.ie/publications/Hays_Anim_Beh_2004.pdf

Kremezi-Margaritouli, A. (1995). Caretta: The Loggerhead Sea Turtle in Greece. Erevnites, Greece.

Leao, M. (2002). "Remora remora" (On-line), Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Remora_remora.html

Morgan, P.J. (1990). The Leatherback Turtle. National Museum of Wales, Cardiff.

Ripple, J. (1996). Sea Turtles. Colin Baxter Photography Ltd., Scotland.

The Nova Scotia Leatherback Turtle Working Group (NSLTWG). (2005). http://www.seaturtle.ca/research.htm

Further Publications

Gulko, D. and Eckert, K. (2004). Sea Turtles: An Ecological Guide. Mutual Publishing, Hawaii. 122pp. Also available from WIDECAST:
widecast@ix.netcom

Lutz, P.L. and Musick, J.A. (1997). The Biology of Sea Turtles. CRC Press, Boca Raton, Florida. 432pp.

Further Information

If the information you are looking for is not present on this FAQ page or on the Euroturtle website, please email your question to the following address: medasset@medasset.gr