Rat

Rats are medium-sized animals.

They have very long tails. These tails help them stay balanced. The tail also helps them stay cool.

Rats are bigger than mice. There are 56 kinds of rats. Some rats live near people. Others live on far islands.

Some rats are kept as pets. Pet rats can be very friendly. You can even teach them tricks.

Scientists also study rats. They help us learn about health. This helps people all over the world.

Rats are very smart animals.

Rats are medium-sized rodents with long tails.

There are 56 known species of rats in the world. Most people know the black rat and the brown rat. These two come from Asia.

Rats are usually bigger than mice.

A rat's tail is very useful. It helps the rat stay cool. This is called thermoregulation. The tail also helps the rat stay balanced. It uses muscles to shift its weight. If a predator grabs a rat's tail, the rat can escape. It does this by losing the outer layer of skin. This is called degloving.

Some rats live near humans. These rats can carry germs. This can make people sick. In the past, rats helped spread the Black Death.

Many people keep rats as pets. Pet rats are often very friendly. You can teach them tricks. Scientists also study rats. They use rats to learn about medicine and the brain. Rats are very smart and can solve problems.

Rats are medium-sized rodents with long tails.

There are 56 known species of rats in the world. Most people know the black rat and the brown rat. These two come from Asia.

Rats are usually bigger than mice. A group of rats is called a mischief. Some rats live near humans and are called commensals. This means they live alongside us. While many rats live in the wild, some live on islands. These island rats can be endangered if they lose their homes.

A rat's tail is a very busy tool. It helps the rat stay cool through thermoregulation. This is a way to manage body heat. The tail is thin-skinned and has many blood vessels. These vessels help heat move from the body to the air. The tail also helps with proprioception. This is a sense that helps the rat know where its body is. By moving tail muscles, a rat can shift its center of mass. This helps them stay balanced in a three-dimensional world.

Some rats have a special way to escape danger. If a predator grabs a rat by the tail, the rat can use degloving. This is a defense where the outer layer of skin comes off. This helps the rat get away quickly. However, this can lead to infections because the blood vessels are exposed.

In the past, rats were part of a big sickness called the Black Death. This happened in European cities during the Middle Ages. Fleas that lived on black rats carried the germs that made people ill.

Rats grow up very quickly. They become sexually mature at only 6 weeks old. They reach social maturity around 5 to 6 months. In the wild, many rats only live for about one year. This is often because of predators.

Some rats are kept as pets. People have kept them since the late 19th century. Most pet rats are brown rats. Some even have special features, like the Dumbo rat with low, saucer-shaped ears.

Scientists also study rats to help humans.

In 1895, researchers at Clark University began studying rats to learn about diet. Rats are great for science because their hearts and blood vessels are similar to ours. This is called anatomical homology. They are also very smart. A 2007 study found that rats have metacognition. This is a mental ability to think about their own thoughts. This makes them excellent tools for learning about the brain and medicine.

Rats are medium-sized rodents characterized by their long tails. While the term "rat" is used broadly, most stereotypical rats belong to the genus *Rattus*. There are 56 known species of rats in the world. Other related genera include *Neotoma*, known as pack rats, and *Dipodomys*, known as kangaroo rats. In common language, the word "rat" usually describes a large muroid rodent, while "mouse" describes a smaller one. However, these names are not taxonomically specific.

Many rat species are opportunistic survivors. Some are considered commensals, meaning they live alongside and near humans. While these commensal species are a minority, they can cause significant food losses, particularly in developing countries. Other rats are island endemics, meaning they live only on specific islands. These species often face the threat of becoming endangered due to habitat loss or competition from the brown, black, or Polynesian rat.

Wild rats can carry various zoonotic pathogens, which are diseases that spread from animals to humans. Examples include *Leptospira*, *Toxoplasma gondii*, and *Campylobacter*. Historically, rats played a role in the Black Death during the Middle Ages. It is traditionally believed that the microorganism *Yersinia pestis* caused this epidemic. The disease was carried by the tropical rat flea, *Xenopsylla cheopis*, which preyed on black rats in European cities. In this process, the rats acted as transport hosts.

The tail of a rat is a complex organ with three primary functions. First, it assists with thermoregulation, which is the process of managing body heat. The tail is hairless and thin-skinned but highly vascularized, meaning it has many blood vessels. This structure allows for efficient countercurrent heat exchange with the environment. Second, the tail aids in proprioception, or the sense of body position. High densities of muscle and connective tissue allow the rat to use its tail to shift its center of mass and maintain balance.

Third, the tail serves as a defense mechanism through a process called degloving. This is a nocifensive response, meaning it is triggered by acute pain. If a predator grabs a rat by the tail, the outermost layer of the integument, or skin, can detach. This allows the rat to escape, though it carries risks. Because the tail is so vascular, losing this skin layer can expose interior elements to bacterial or viral infections.

In terms of life history, rats reach sexual maturity at just 6 weeks of age. They reach social maturity between 5 and 6 months. The average lifespan varies by species, but many wild rats live only about one year due to predation. Since the late 19th century, humans have kept domesticated rats as pets. Most pet rats are variants of the brown rat, *Rattus norvegicus*. Selective breeding has created many varieties, including the hairless rex and the popular Dumbo rat, which has low, saucer-shaped ears.

Rats are also vital subjects in scientific research. In 1895, Clark University began using domestic albino brown rats to study diet and physiology. Rats show remarkable anatomical homology to humans, particularly in their cardiovascular systems. For example, the rat's aortic arches branch in ways very similar to human arteries. This makes them valuable models for studying human heart conditions.

Beyond biology, rats are used in psychological and genetic studies. They are known for their high intelligence, ingenuity, and adaptability. A 2007 study even found that rats possess metacognition, which is the ability to think about their own mental processes. Because their genomes have been sequenced, researchers can use them as precise genetic tools. This work has contributed greatly to our understanding of genetics, diseases, and the effects of drugs.