Rodent

Rodents are a large group of mammals with special teeth called incisors that grow continuously. They use these teeth to chew food and dig holes. Rodents make up about 40% of all mammal species, so they are one of the most common groups of animals on Earth. They live on every continent except Antarctica and have been brought to many islands by people.

Most rodents are small, with strong bodies, short legs, and long tails. You can find them in many places, such as forests, deserts, mountains, and even homes. Rodents live in many different ways, like climbing trees or digging underground homes. They often live together in groups and have ways to talk to each other.

Rodents are important to humans in many ways. Some people keep them as pets, and others use them for scientific studies. However, a few types, like the brown rat, black rat, and house mouse, are seen as pests because they can eat and spoil food and spread sickness. Well-known rodents include mice, rats, squirrels, prairie dogs, porcupines, beavers, guinea pigs, and hamsters.

Characteristics

Rodents have sharp, always-growing teeth called incisors. They need to chew on things to keep these teeth short and safe. These teeth have a hard outer layer and a softer inner layer, making a sharp edge like a chisel. Most rodents have between 12 and 28 teeth, with a space called a diastema between their front teeth and molars to help with eating.

Rodents have strong jaw muscles that help them gnaw and chew. They move in many ways, such as walking, running, climbing, hopping, and swimming. Some, like flying squirrels, can glide using special skin membranes. Rodents have great smell and hearing, and many have long, sensitive whiskers to explore their surroundings. Many also carry food in special cheek pouches back to their homes.

Distribution and habitat

Rodents live almost everywhere, on every continent except Antarctica. They were the first land mammals to live in Australia and New Guinea without help from humans. Today, rodents can be found in many places because humans have taken them to remote islands.

Rodents adapt well to different environments, from cold tundra under snow to hot deserts. Some live in trees, others underground, and some stay near water. They also thrive where people live, like farms and cities. Rodents help nature in many ways. For example, by digging tunnels, they spread fungi spores, which helps plants grow. In North America's Great Plains, prairie dogs improve soil by aerating it, and beavers create wetlands by building dams.

Behavior and life history

Most rodents eat only plants, like grasses and leaves. Others might also eat insects or small animals. For example, the field vole mainly eats plants but sometimes eats insect larvae. Some rodents, like the African pouched rat, carry food in their big cheek pouches and pick the best parts to eat later.

Rodents can live together or alone. Prairie dogs stay in large groups, but hamsters often live by themselves. Some rodents, like beavers, live with their families. Rodents talk to each other in different ways, using smells, sounds, and vibrations to share messages and warn about danger.

Many rodents stay together as pairs, while others find many mates. Mothers take care of their babies in different ways. Some baby rodents are born blind and without fur, while others can move around soon after birth. Rodents are smart animals with good memory and learning skills.

Evolutionary history

The earliest fossils showing the special teeth of rodents come from the Paleocene period, just after the dinosaurs went extinct. These fossils were found in Laurasia, an ancient land that included parts of North America, Europe, and Asia. Rodents and their close relatives, the lagomorphs like rabbits, spread around the world during the Cenozoic era.

Some very early rodents lived in North America, and beavers first appeared there in the late Eocene. Over millions of years, rodents traveled to many parts of the world, even reaching places like Africa and South America. By about 20 million years ago, many modern rodent families existed. Some ancient rodents were much larger than today’s species, like Josephoartigasia monesi.

Classification

Further information: List of rodents

Rodents are a large group of mammals known for their always-growing front teeth, called incisors. The name "Rodentia" comes from a Latin word meaning "to gnaw." They are related to animals like hares, rabbits, and pikas. Rodents have one set of upper front teeth, while lagomorphs have two.

Scientists have studied rodents for many years to sort them into groups. They look at physical traits to decide how to group them. Even with modern genetic studies, the grouping is still discussed. Today, there are many families of rodents, with over 2,000 different species known.

Conservation

Some rodents face threats that put them at risk. Over 168 species need special care because people often don’t see them as important.

Certain rodents have caused problems for birds on islands, like the black rat. Efforts to remove these rats from islands have helped bird numbers grow again. Climate change has also been a problem, especially for rodents living on small islands. The Bramble Cay melomys was the first mammal known to disappear because of human-caused climate change.

Interaction with humans

Humans have used rodents in many ways. Their fur has been used to make clothing. For example, Native people of North America used beaver pelts to make robes, and Europeans later valued this fur for making hats. Today, animals like coypu and chinchilla are also used for their fur.

Rodents are also a food source for many cultures. Guinea pigs have been eaten in South America for thousands of years, and in Peru, they are still an important source of protein. Other rodents like squirrels and porcupines are eaten in places such as the United States and by Native American groups like the Navajo and Paiute.

Rodents are also important in scientific research. Mice and rats are commonly used in laboratories because they are easy to care for and share many health conditions with humans. They help scientists study topics like genetics, diseases, and the immune system. Some rodents, like the Gambian pouched rat, have even been trained to detect diseases and dangers.

Many rodent species are kept as pets because they are friendly, intelligent, and easy to care for. Pets such as rats, mice, hamsters, gerbils, guinea pigs, and chinchillas are popular choices in homes around the world.

However, some rodents can also cause problems. They eat large amounts of stored food, which can cause losses for farmers. They can also spread diseases to humans. Because of this, many communities work to control rodent populations using safe methods.