Turtle

Turtles (order Testudines) are reptiles known for their special shell that forms from their ribs. This shell protects them and is made of bone, with a domed top called the carapace and a flatter bottom called the plastron. There are 360 living species of turtles, including land-dwelling tortoises and freshwater terrapins, found on most continents and in oceans as sea turtles.

Like other amniotes such as birds and mammals, turtles breathe air and lay eggs on land, even though many live in water. They are ectotherms, meaning their body temperature changes with the environment. Turtles usually eat both plants and animals and may move short distances for food or nesting.

Turtles have inspired stories and myths around the world, and some are popular pets. However, many turtle species face serious threats. People have hunted turtles for food, medicine, and their shells. Sea turtles often die accidentally when caught in fishing nets, known as bycatch. Habitat loss also endangers turtles, and many species are now extinct or at risk of disappearing.

Naming and etymology

The word turtle comes from the French word tortue or tortre, meaning 'turtle' or 'tortoise'. It is a common name used for different kinds of turtles without needing to know scientific details. In North America, turtle can refer to all turtles, while in Britain, it usually means sea turtles, not freshwater terrapins or land tortoises. In Australia, where there are no true tortoises, people used to call non-marine turtles tortoises, but now turtle is used for all of them.

The scientific name for turtles is Testudines, which comes from the Latin word testudo meaning 'tortoise'. This name was created by a German scientist named August Batsch in 1788. Other older names for the group include Chelonii and Chelonia, based on the Ancient Greek word χελώνη (chelone), also meaning 'tortoise'. Testudines is the official name because it was used first. The word chelonian is a formal term for members of this group.

Anatomy and physiology

Turtles are reptiles known for their special shells, which protect them and help shield them from the elements. The shell consists of two main parts: the domed back shell called the carapace and the flatter belly shell called the plastron. These parts are made from bones fused with the turtle's spine and ribs.

Turtles have unique heads and necks. Their skulls are solid and rigid, and their necks are very flexible, though they only have eight neck bones, just like mammals. Some turtles, like sea turtles, have short necks, while others, like snake-necked turtles, have very long necks. Turtles move slowly on land but can swim quickly in water. Their limbs adapt to their lifestyles; for example, sea turtles have flippers for swimming, while tortoises have legs suited for walking on land.

Behavior

Turtles have different diets depending on where they live. Land turtles usually eat plants, while water turtles often eat small animals like worms or fish. Some turtles, like the African helmeted turtle, even eat birds and other turtles! They catch their food in different ways, such as ambushing it or using special tricks like luring fish with a worm-like appendage.

Turtles can also make sounds to communicate, like bellowing during mating or making chirps and clicks. They can learn new tasks and remember them for a long time. When danger comes, turtles often hide inside their shells or run away. Some even play dead to scare off predators. Sea turtles travel very long distances to lay their eggs on specific beaches, returning to the same spots each year. Scientists think they may use Earth’s magnetic field to find their way home.

Reproduction and life cycle

Turtles do not form lasting pairs or social groups when they mate. In land turtles, males are usually larger than females and fight for the chance to mate. In water turtles, males may use their size to mate, or they perform special dances to win a female's attention. Female turtles have ways to avoid mating if they do not want to, such as swimming away or using their bodies to block the male.

Turtles lay their eggs on land, sometimes traveling far to find the right spot. The mother digs a hole, lays her eggs, and usually leaves right after. The sex of baby turtles depends on the temperature where the eggs are laid. Baby turtles hatch from their shells using a special tooth on their beaks and then make their way to safety. Turtles can live for many years, with some living over 100 years old.

Systematics and evolution

Scientists have long studied how turtles developed their unique shells. Early ideas suggested that bony plates in the skin fused with ribs. However, newer discoveries show that early turtle ancestors had shortened torsos and expanded ribs before developing full shells. Over millions of years, these changes led to the hard shells turtles have today.

Turtles evolved into two main groups based on how they pull their heads into their shells. One group pulls their heads backward, while the other pulls their heads to the side. These differences helped turtles survive in various habitats around the world.

Distribution and habitat

Turtles live all over the world, in many different places such as land, water, and islands. Sea turtles prefer warm areas, but some can live in colder parts of the Atlantic and Pacific oceans. Most side-necked turtles live in freshwater in the Southern Hemisphere, while hidden-necked turtles can be found on land, in freshwater, and in the ocean.

Turtles in cold places have trouble having babies because they need to stay asleep for long periods during winter. In North America, turtles are mostly found below the southern edge of Canada. Some turtles can live very high up, like the Terrapene ornata in New Mexico, which can be found up to 2,000 metres above sea level. The leatherback sea turtle can dive deeper than 1,200 metres. Some land turtles can handle very cold or very hot temperatures, but they are most active between 26–34 °C.

Conservation

Turtles are at risk because of many dangers, including habitat destruction, being caught for food, and changes in the weather called climate change. Many turtle species in Asia are in big trouble because people have been taking too many of them for food and medicine for a long time.

People sometimes set up special places called hatcheries to help turtles stay safe. Even so, many turtles are still caught from the wild and sold, which is a big problem. In some places, turtles are accidentally caught in fishing nets meant for other animals. To help prevent this, some fishing boats now use special devices that let turtles escape from the nets.

Human uses

On space flights

Two tortoises were on the Soviet Union's September 1968 Zond 5 circumlunar flight, making them the first living things to travel near the Moon. Turtles also flew on later missions in 1968 and 1969.

In culture

Main article: Cultural depictions of turtles

Further information: World Turtle

Turtles have been important in cultures around the world for thousands of years. In many stories, turtles are seen as wise and patient. For example, in Hindu stories, a giant turtle named Kurma helps hold up the world. In Native American traditions, turtles are part of creation stories, like how the Earth was formed on Turtle's back. Ancient Greeks told tales of a tortoise that carried its home forever because it refused to go to a wedding.

As pets

Some small turtles and tortoises make popular pets. In the 1950s, many people in the United States kept pets like the red-eared sliders. However, keeping turtles as pets can be tricky, and sometimes they get sick or have health problems.

As food and other uses

In some parts of the world, people eat turtle meat, and turtle eggs are traded for their supposed health benefits. Turtle shells have been used for making jewelry, tools, and even musical instruments for many years. Today, there are rules to protect turtles from being hunted for their shells.