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 can hold their breath for several hours, depending on their level of activity.

If they are sleeping, they can remain underwater for 4-7 hours. In cold water during winter, when they are effectively hibernating, they can hold their breath for up to 10 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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Hawksbill turtle resting on the reef, Maldives
Adult hawksbill turtle, Maldives

The actual documentation of a sea turtle’s age in the wild is difficult. The lifespan of an olive ridley or hawksbill turtle in the wild is approximately 50 years; greens turtles can live up to 80 years; loggerheads up to 67 years; while estimates for the lifespan of a leatherback turtle range anywhere from 13 to 100+ years.

Green-turtle-hatchling-Claire-Maldives-rescue-centre-ORP
Green turtle hatchling – 5 cm long

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) !

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.

Juvenile hawksbill turtle swimming on reef Maldives
Juvenile hawksbill turtle, Maldives
© Chiara Fumagalli

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.

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

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.

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Video © Beth Faulkner, Manta Trust
Loggerhead turtle nest, Cap Verde
Loggerhead turtle nest, Cap Verde

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 turtles nests incubate for approximately 55 to 65 days.

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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Arribada in Mexico a synchronized, large scale nesting event by olive ridley turtles
Arribada in Mexico: a synchronized, large scale nesting event by olive ridley turtles © Susie Gibson

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: Sea Turtle Conservancy

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.

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Green turtle diving, Maldives
Green turtle diving, Maldives

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 m (500 feet) though Olive Ridleys have been recorded at 225 to 250 m (750 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”).

Turtle skeleton, Australian Museum
Turtle skeleton, Australian Museum

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.

Green turtle swimming in Maldives
Green turtle swimming in Maldives

Sea turtles are generally slow swimmers but can swim at bursts of speed of up to 35 km/h (22 mph)

Turtle trapped in burlap bag, Maldives

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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