Turtle facts

Turtles are unique because they are the only vertebrates with a shell. While, all turtle species have a shell, but they don’t all look alike. Some are tough and spiky, some beautifully patterned, and some are softer, leathery and waxy. These ancient reptiles range from tiny, delicate, snappy species to massive, slow-moving ones. They live in oceans, rivers, deserts and more.

• Jonathan, a Seychelles giant tortoise, is 192 years old as of 2025. He was already over 40 years old when the telephone was invented.
• Turtles are older than dinosaurs, and their exact origin remains a mystery.¹ Scientists cannot decide on which animals they evolved from. Some think they’re related to dinosaurs and crocodiles, others think they’re closer to lizards and tuataras.
• While turtles are often associated with warm, tropical places, they can be found in environments around the world. Some species inhabit unexpected places like deserts and even the frigid waters of Alaska.²
• Leatherback turtles are the deepest-diving turtles. In 2024, scientists recorded a leather back diving to 1,344m, the new Guinness record holder for deepest turtle dive.
• Tortoises cannot swim, but in 2004, an Aldabra giant tortoise was found on a beach in Tanzania, over 450 miles from its home in Seychelles.³
• The temperature of turtle eggs as they develop affects the sex. Warm temperatures produce females, and cooler temperature produce males – also known as the “hot chicks, cool dudes” principle.

Turtles are ancient animals, and the story of their evolution is a little bit of a mystery. Scientists cannot agree on which animals they evolved from.

Research from 2014 involving DNA analysis of over 200 living reptiles suggests that turtles were a sister group to the archosaurs, the clade that contained dinosaurs and which modern birds and crocodiles evolved from.⁴ However, morphological theories suggest that turtles are either closely related to lizards and tuataras, or they’re related to another group of reptiles that no longer exists, called diapsids.⁵

Regardless, the oldest animal with a turtle shell dates to the Late Triassic, about 230 million years ago. Fossils from China unambiguously represent proto turtles. They had fully formed turtle shell bellies, but not entirely completed turtle shell backs.⁶

All living turtles today can be traced back to an ancestor that lived around the Middle Jurassic. As they evolved, ancient turtles simplified their shell, developed specialised ear that allowed hearing above and below water and reorganised their jaw muscles. Over time, turtles have continued to adapt to new environments. Today you can find them in forests, rivers, deserts and even the middle of the ocean.

The turtle group is divided into two main categories: Cryptodira and Pleurodira.⁷ These turtles are classified according to how they retract their necks back inside their shells. Because they have slightly different vertebrae arrangements, the Cryptodira tuck their necks straight back into themselves, so are informally called hidden-necked. The Pleurodira fold their necks sideways into the shell so are called side-necked.⁸

These two big categories then split into various genera, and 357 different species, of which seven are now extinct.⁹

Most turtles are semi-aquatic, which means that they live both on land and in the water. However, some turtles are more specialised. Tortoises only live on solid ground, and the seven species of “sea turtles” spend almost their entire lives in the ocean.

Although all turtles have a shared feature with their shells, the rest of their appearance can be surprisingly varied.¹⁰

The aptly named Roti Island snake-necked turtle has a long, slender, neck slithering out of its shell. The Southeast Asian narrow-headed softshell turtle has a leathery shell and a thumb-like head protruding straight from it. The southern river terrapin (a type of freshwater turtle) has a black, pointy, snouted face with jagged teeth.

Turtles are reptiles.¹¹ They are reptiles because they’re cold-blooded, they breathe with lungs and their bodies are covered in scales. They also lay hard-shelled eggs - unlike the gelatinous ones common in amphibians (frogs, salamanders).

The seven sea turtle species that live throughout the world’s oceans are also reptiles like their land-dwelling relatives. Even though they live underwater, they come up for air anywhere from every couple of minutes, to every couple of hours, depending on their activity.¹² Female sea turtles must return to land to lay their eggs in the sand, because they cannot lay them in water. 

Turtles are formally known as Testudines, a name derived from the Latin word testudo, meaning tortoise. They’re also referred to as Chelonia, from the Ancient Greek word for tortoise. The modern-day English word “turtle” emerged when English-speaking sailors encountered these animals while travelling. They picked up the French word tortue, which originated from the Latin phrase bestia tartarucha, meaning beast of the nether regions – as if they came from hell!¹³

Turtles are further divided into subcategories, such as sea turtles, tortoises, or terrapins. Tortoises mainly live on land, sea turtles spend their lives in the ocean, and terrapins tend to live mostly in freshwater rivers and ponds.

Turtles can be found all over the world, in the Mediterranean, in Asia, in Africa, in Australia, and all throughout the Americas. Each species is specialised to their specific location. Only about 20 species appear in more than one of these regions.¹⁴ Researchers who calculated turtle distribution in 2010 found that the region of Indo-Burma has the widest variety of species, with a total of 51 different types of turtle, while the Mesoamerican region follows with 31 different species.¹⁵

Within these regions, turtles live in a wide variety of environments.¹⁶ Some live in woodlands on sand ridges and others live in forests or moist rice paddies. Some live in ponds and bogs, others in lakes, rivers, deserts and out in the open ocean.

There are seven species of sea turtles, which swim in oceans all over the world.¹⁷ Their nests can be found on the beaches of more than 120 countries.¹⁸ At least four different types of turtle can be found in the frigid waters of Alaska.¹⁹

Tortoises are turtles that have evolved to live solely on land. There are around 65 species of tortoise depending on taxonomic revisions.²⁰

Tortoises differ from other turtles in a few ways. Their shells are larger and rounded, more shaped like domes. This shape helps protect them and shelter them out in the rugged wild, and it also regulates their body temperature in hot environments.

These species of turtles also have legs made for walking around, not swimming. In many species, their thick hind legs are referred to as columnar, or elephantine because they stand straight like an elephant’s.²¹ Having strong legs helps tortoises to hoist up their heavy shells. Instead of having webbed feet, tortoises have sharp claws to dig around in the dirt. 

Not all turtles swim. Land turtles, known as tortoises, like the huge Galapagos species, have strong legs made for walking, not splashing around. This doesn’t mean they’ll drown if they’re in the water – they might be able to float. For instance, in 2004, a hefty Aldabra giant tortoise from the Seychelles showed up on a beach in Tanzania over 450 miles away.²² It likely got washed out during a storm and floated all the way to safety.

Many species of turtles live in freshwater marshes, ponds, and rivers and they all swim. They have webbed feet to help them paddle and thrust themselves around the water.²³

Seven species have evolved to spend their whole life in the ocean and are the strongest swimmers of all turtles. They have specialised flipper-like limbs that move around in a efficient circular motion, like wings, so they can cruise at speeds of up to 9km/h.²⁴

Turtles swim slower than penguins or other marine mammals and birds because they have much lower metabolisms and are naturally wired to consume a lot less energy.²⁵ While they don’t swim quickly, they can cover great distances. Populations of green sea turtles have a migration distance of about 2,300km each year.²⁶

There are seven species of turtles known as sea turtles as they spend the majority of their time in the oceans of the world.²⁷ Among others, these include leatherback turtles (the largest of the sea turtles), the hawksbill turtle, known for its beautiful patterned-shell, and the green sea turtle.

Sea turtles differ from land tortoises in a variety of ways because their bodies have evolved to a life of swimming around.²⁸ Their heads and limbs are always outside of their shell, cannot be retracted inside for protection, and instead of having limbs with little claws, sea turtles have flattened, flipper-like legs. Sea turtles also have flattened shells close to their bodies, unlike the huge, domed shells of ancient tortoises.²⁹ This reduces drag, making them  more efficient and “hydrodynamic” swimmers.

Turtles living in the oceans also must cope with a lot of salt in their environment. To combat this, they’ve evolved salt-purifying glands near their eyes that help them get rid of the excess minerals.³⁰ Don’t worry, they’re not crying! Leatherback turtles have salt-purifying glands so big they’re twice the size of their brain.

Sea turtles are still reptiles. They don’t have gills, and most species cannot breathe underwater. However, they can hold their breath for a long time. When they’re active, sea turtles go up for air quite often, sometimes at intervals of 20 or 40 minutes.³¹ While they’re resting, though, they can hold their breath for between four and seven hours. To save oxygen while resting underwater, their heart rate slows down, as low as one beat every nine minutes.³²

While this adaptation is not present in sea turtles, some species can breathe underwater using cloacal respiration. This adaptation allows turtles to absorb oxygen from water using their cloaca – a multi-purpose opening on their backsides for excretion and reproduction. It is especially useful for freshwater turtles that spend long periods underwater, such as the white throated snapping turtle, which can get up to 70% of its oxygen from water.³³ While not as efficient as lung breathing, cloacal respiration helps these turtles conserve energy and remain submerged in low-oxygen environments.

Unlike their freshwater counterparts, sea turtles can swim vast distances and reach incredible depths. Most descend until almost 300 metres below the surface, while the leatherback turtle can dive up to a kilometre deep.³⁴ Leatherback turtles are adapted to life in the deep. They have a more flexible shell than other ocean-dwelling turtles, and they can compress their lungs while they go deep under.³⁵

Scientists once recorded a leatherback turtle much lower than they’d ever expected. The organisation Nature Conservancy tagged a turtle called ‘Uke Sasakolo’ in the Solomon Islands in December 2023. In March 2024, as they tracked it going all the way to New Zealand, they recorded her diving to a depth of more than 1,340 metres.³⁶ Researchers think these deep dives help leatherback turtles scout for food and estimate where their preferred food – which is  jellyfish — will be floating up to the surface during the night.³⁷

As turtles are the only animals with backbones to have shells, their structure is unique.³⁸ These shells are part of their skeleton. They’re not like hermit crabs – turtles cannot crawl out of their shells.

"The turtle shell is a unique innovation in the long history of life," says Jacques Gauthier, a vertebrate palaeontologist from Yale University.           During evolution, the ribs, vertebrae, and parts of the shoulder girdle fused with the hard-scaled skin and turned to bone. “The shell thus surrounds the turtle but is also an integral part of it.”

The top part of the shell is called the carapace and the bottom part is called the plastron.³⁹ The two elements are fused all around the turtle like a box made of 50 to 60 different bone fragments joined together.⁴⁰ The bones are covered in scales made of keratin – the same substance our hair and nails are made of – and they’re sensitive to pressure and touch.

Since turtles and tortoises are so slow they would never be able to run away from a predator, their hard shells likely evolved as a trade-off to provide extra protection.⁴¹

Not all turtles have hard shells, though. About 30 species of turtle have soft shells – they don’t have hard keratin scales but their shell is simply covered in thick, leathery skin.⁴² Among sea turtles, the leatherback turtle has a rubbery shell made of waxy skin and not keratin.⁴³

Depending on where they live, turtles eat a wide variety of things.

Tortoises are mostly herbivorous. The gopher tortoise of the sand hills of west-central Florida eats foliage from a variety of native plants, although records show they sometimes munch away at insects and charcoal.⁴⁴ Amazonian tortoises in Brazil love fruits in the wet season and flowers in the dry season, but they also occasionally snack on foliage, stems, fungi, soil, sand, pebbles, and animal matter.⁴⁵ Sometimes tortoises will also eat bones — a practice called osteophagy – to supplement their diet with calcium.⁴⁶

Freshwater turtles are considered omnivores: they eat invertebrates, small vertebrates, and aquatic vegetation.⁴⁷ That’s everything from worms, snails, larvae, small frogs, small snakes, and small fish.

Sea turtles are omnivores too – but they have their preferences.⁴⁸ While they eat everything as babies, when they mature and become adults, their diets become more specific. For example, adult green sea turtles are mainly vegetarian. They eat algae, seaweed, and seagrass, and this is why they develop a bright green colour. Leatherback turtles are carnivores: they eat heaps of squid and jellyfish. Hawksbill turtles eat sponges, with a side of squid, shrimp, and algae. Loggerheads eat a whole array of sea creatures, even tough barnacles and sand dollars. 

Turtles are the only reptiles with no teeth.⁴⁹ Instead of teeth, they have beak-like mouths and powerful jaws that have adapted to different types of diets. Carnivorous turtles have a sharp, pointed beak that allows them to pierce and shred their meaty snacks.⁵⁰ Herbivorous turtles have flat beaks with serrations along the edges for smashing fibre-rich plants and fruits. Omnivorous turtles have a mix of both, with sea turtles having extra hard mouths to make sure they can crush prey even with increased underwater pressure.⁵¹ Some sea turtles catch their prey with a remarkable method: they open their jaws wide and explosively suck water in, vacuuming the food into their mouth.

Turtles vary widely in size.⁵²

The speckled dwarf tortoise of South Africa reaches about 10 centimetres in size during adulthood.⁵³ Giant Galapagos tortoises can measure up to 1.3 metres and weigh more than 400 kilograms.

Sea turtles range from the size of a volleyball to the size of a double mattress. Kemp's ridley sea turtle is the smallest sea turtle species and it grows to about half a metre in length.⁵⁴ By comparison, Leatherback turtles can weigh up to 900 kilograms and grow to be almost two metres.⁵⁵ In the late Cretaceous (100 mya – 66mya), there was a giant sea turtle called Archelon that measured almost four metres in length.⁵⁶

Turtles are some of the longest-lived animals on the planet. But this varies greatly between turtles, sea turtles, and tortoises.

Most turtles live between 15 and 50 years.⁵⁷ Sea turtles are estimated to live between 50 and 100 years.⁵⁸ Some species of turtles are known to have something called slow, or negligible senescence, meaning that they avoid the increasing risk of death from the gradual deterioration of aging. Research published in Science in 2022 suggested that out of 52 species of turtles studied, about 75 percent of them exhibited slow and negligible senescence and 80% aged rates were lower than modern humans.⁵⁹

The giant Galapagos tortoises are good examples of this because they live on an island with no natural predators, meaning their chances of growing old are higher than animals who are at risk of being eaten. Scientists aren’t sure how long these tortoises can live for, and they have been looking for an answer hidden within their unique genetic makeup.⁶⁰

As of 2025, Jonathan the Seychelles giant tortoise is 192 and lives on the island of Saint Helena. He arrived on the island in 1882.      Napoleon Bonaparte was still alive when Jonathan was born. The tortoise was older than 40 when the telephone was invented.

Turtles are known as the slow pokes of the natural world – just think about the fable of the hare and the tortoise.      

The fastest tortoise ever recorded is called Bertie, and in 2014 it won the Guinness World Record by running at a whopping 0.28 metres per second – which is about 1 kilometre per hour.⁶¹ “The morning of the attempt was pretty nerve-racking. We didn’t know what sort of mood Bertie would be in,” said Janine Calzini, Bertie’s owner, in an article about the tortoise’s extraordinary feat.⁶²

Many turtle species live in warm, tropical areas of the world so they are active all year round. But for turtles that live in temperate or even cold regions of the world, staying active throughout the frigid winter months is too risky and energy consuming. Instead, they go into the reptile equivalent of hibernation: brumation.

Hibernation is a term reserved for mammals because they are warm-blooded, and slowing down their metabolism involves activating adaptations that send animals into a state of deep sleep.⁶³ Cold-blooded reptiles undertake brumation which is more akin to torpor or suspended animation – they still wake up from time to time to top up on food and water.

Baby painted turtles living in marshes from Nebraska to Illinois hatch when winter starts.⁶⁴ Instead of going out, they baby turtles overwinter in the den where they were born. As they rest there, they become fully frozen and immobile, sometimes for six months. A special anti-freeze-like substance in their bodies allows them to sustain sub-zero temperatures. When spring comes, they defrost and become active again.⁶⁵

When scientists tracked overwintering northern map turtles  in North America, they found that a  group of turtles spent five months under ice in frozen ponds, where temperatures never reached above 1.4°C.⁶⁶

A 2024 study tracking some Australian eastern long-necked turtles throughout the winter period found that they survived 15 days inside a pond that was totally frozen over – the first observation of brumation for an Australian turtle under ice.⁶⁷

Different turtle species reach sexual maturity at different times: some take just a couple years,  while others take as  many as 20  to 40 before they’re able to reproduce.⁶⁸ Once they are old enough, turtles must find a partner to mate with.

Mating looks different in different species. Some rituals are aggressive, with males competing before biting and clawing at their potential partner. Others are a bit more romantic. They caress, bob, sway, and even vibrate their heads.⁶⁹ Some species make impassioned sounds, and other show interest by squirting each other with water. Not all turtles are so adventurous. Sometimes, courting behaviour is imperceptible, where turtles simply walk up to each other before initiating intercourse.⁷⁰

After mating and fertilizing their eggs, female turtles go looking for a suitable place to lay. For terrestrial turtles, this usually involves digging a nest in the soil. But for sea turtles, this involves swimming hundreds of kilometres out of the ocean and finding a safe spot somewhere on a beach or sand bar. 

The two species of ridley sea turtles nest in large groups called arribada, where several hundred turtles all surface from the water and find a spot to lay their eggs together over several hours.⁷¹ Scientists are still trying to figure out how turtles know how to do this –theorising that they follow offshore winds or lunar cycles.

Once they’ve found the perfect spot to lay eggs, most turtle mothers dig holes with their back legs to make a den for their clutch. Some turtles only lay one or two eggs – like the pancake turtle – while others can lay hundreds in one go, like the hawksbill turtle.⁷² Mothers do not incubate or take care of their eggs. The embryos are all on their own until they hatch. For most turtles, eggs take about 45 to 75 days to hatch.⁷³

The temperature during this incubation time determines whether the clutch will have mainly females, or mainly males. This is known as temperature-dependent sex determination, or the “hot chicks, cool dudes” principle among turtle conservation workers.⁷⁴ The warmer the nest the more females hatch, the colder the nest the more males hatch, but it is a continuos sliding-scale process, not a binary.

Despite having witnessed the dinosaurs rise and fall, turtles today face an extinction event of their own. The greatest risks to turtles are climate change, destruction of their habitat, consumption of their meat, collection for the pet trade or traditional medicine use, and the introduction of invasive species that predate on them in their habitats.⁷⁵

As of the current IUCN 2021 Red List, 183 turtle species – more than half of recognised modern species of turtles – are officially regarded as threatened or vulnerable.⁷⁶ And several of these are critically endangered, like the Yangtze giant softshell turtle from China and Vietnam, the ploughshare tortoise from Madagascar, the Yunnan box turtle from China, the geometric tortoise from South Africa, and the Dahl’s toad-headed turtle from Colombia.⁷⁷This makes turtles one of the groups with the highest extinction risk of any sizable vertebrate group, according to experts from the IUCN.⁷⁸

One of the most well-known losses was the Pinta Island tortoise (Chelonoidis abingdonii) from the Galapagos.  The last known individual, a male named Lonesome George, died on June 24th 2012 marking the end of his species.

Featured image © Giorgia Doglioni| Unsplash

Fun fact image © Randall Ruiz- | Unsplash

Interview:

An interview with Jacques Gauthier, a vertebrate palaeontologist from Yale University, was conducted over email in March 2025.

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