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 many 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 and shells. Sea turtles often die accidentally when caught in fishing nets, known as bycatch. Habitat loss also endangers turtles, and many species are now 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 for different kinds of turtles. In North America, turtle can mean all turtles. In Britain, it usually means sea turtles, not freshwater terrapins or land tortoises. In Australia, people once called non-marine turtles tortoises, but now turtle is used for all of them.

The scientific name for turtles is Testudines, from the Latin word testudo meaning 'tortoise'. This name was created by a German scientist named August Batsch in 1788. Other older names 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 describes members of this group.

Anatomy and physiology

Turtles are reptiles with special shells that protect them. The shell has 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 their necks are flexible, though they only have eight neck bones, 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 eat different foods depending on where they live. Land turtles usually eat plants. 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 waiting for it or using special tricks.

Turtles can also make sounds to talk to each other, like during mating. 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 far 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 stay together as pairs when they mate. In land turtles, males are often bigger than females and may fight to mate. In water turtles, males might use their size or do special dances to get a female's attention. Females can choose to avoid mating by 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 then usually leaves. 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 go to safety. Turtles can live for many years, with some living over 100 years old.

Systematics and evolution

Scientists have studied how turtles got their special shells. At first, people thought the shells came from bones in the skin joining with ribs. But we now know that turtles' ancestors had shorter bodies and bigger ribs before they had full shells. Over many years, these changes made the hard shells turtles have now.

Turtles split into two big families based on how they put their heads into their shells. One family pulls their heads backward, and the other family pulls their heads to the side. These ways helped turtles live in many places around the world.

Distribution and habitat

Turtles live all over the world, in places such as land, water, and islands. Sea turtles prefer warm areas, but some 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 face many dangers, such as habitat destruction, being caught for food, and climate change. Some turtle species in Asia are in trouble because people have taken too many of them for food and medicine.

People have created special places called hatcheries to help protect turtles. However, turtles are still sometimes caught from the wild and sold, which is a problem. In some areas, turtles get caught accidentally in fishing nets meant for other animals. To help with this, some fishing boats now use special devices that let turtles escape from the nets.

Human uses

On space flights

Two tortoises flew on the Soviet Union's September 1968 Zond 5 circumlunar flight. They were 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. Ancient Greeks told tales of a tortoise that carried its home forever.

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.

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 to make jewelry, tools, and musical instruments for many years. Today, there are rules to protect turtles from being hunted for their shells.