Rat

Quick Take

• Rats' tails do something most people never suspect, and it has nothing to do with balance. See how tails work →
• A rat left alone doesn't just get bored. Something specific happens to it that changes how you see these animals entirely. Discover their social nature →
• Rats rank among the world's smartest animals, though the reason why might surprise you more than the ranking itself. Explore rat intelligence →
• A volcanic crater in Papua New Guinea hid something researchers weren't prepared to find. Meet the Bosavi woolly rat →

Rats are medium-sized rodents found almost everywhere in the world. Most species are nocturnal and live together in colonies rather than alone. They are omnivores, eating seeds, fruit, insects, eggs, and small animals. Females can have several litters a year, usually six to twelve pups each, and rats typically live one to three years. Like other rodents, a rat’s front teeth never stop growing, so it gnaws constantly to keep them worn down.

5 Incredible Rat Facts

• Rats make a chattering noise when they’re happy.
• A rat’s long tail helps it to regulate its body temperature.
• Rats are able to jump about 3 feet into the air.
• Rats are considered one of the world’s smartest animals.
• In 2009, a giant rat was discovered in Papua New Guinea. The rat — named the Bosavi woolly rat — lives in a volcano crater that had previously been lightly explored and, with its tail included, measures over 30 inches long. That makes it one of the largest rats in the world.

Evolution and Origin

Rats belong to the rodent family, which is one of the most diverse and widespread mammal groups in the world. The first rodents evolved during the Late Paleocene, at least 56 million years ago, with molecular evidence suggesting origins as far back as approximately 62 million years ago. The earliest known rodent fossils have been found in North America, but they quickly spread to other parts of the world.

The ancestors of modern rats were likely small, burrowing animals that lived in grasslands and forests. Over time, they evolved to adapt to a wide range of environments, from deserts to wetlands.

Rats are believed to have first evolved in Asia, and then spread to other parts of the world. The black rat, also known as the ship rat, is thought to have originated in tropical Asia and spread to Europe via the Near East and Egypt, with separate dispersal to other regions through Indian Ocean trade routes. The brown rat, also known as the Norway rat, is believed to have originated in northern China and spread to Europe and North America.

Classification and Scientific Name

True rats (genus Rattus) are medium-sized muroid rodents, belonging to the family Muridae (which contains mice, rats, and gerbils) and classified in the order Rodentia (rodents). Two of the most common species are:

• Brown Rat (Rattus norvegicus): Also called the Norway or sewer rat.
• Black Rat (Rattus rattus): Also called the roof or ship rat.

Appearance and Behavior

These animals can have black, brown, gray, or white fur. They have two big ears, dark eyes, and long whiskers. They have a mouthful of sharp teeth, including 4 incisors. Their teeth continue to grow throughout their life. They must chew on food and other items to keep the edges worn down.

One of their most notable features is a long, hairless tail. Generally, the animal’s tail is as long or longer than its body. The length of the tail is around 7 inches.

The animal uses its tail for more than one purpose. For one, it helps it to regulate its temperature. Its tail is hairless, so it’s able to release heat to keep a rat’s body cool. Alternatively, when the animal is cold, it can curl its tail around itself to stay warm.

Secondly, a rat’s tail helps it to maintain its balance. They climb up walls and trees and walk along narrow ledges. Its tail helps them to keep their weight balanced so they don’t fall. Rats also possess excellent swimming abilities.

These rodents weigh from 12 to 23 ounces and are 9 to 11 inches long. A rat weighing 16 ounces is about the same weight as a can of soup in your kitchen cabinet. In addition, a rat that’s 8 inches long is half the height of a bowling pin.

The largest rat in the world is the Northern Luzon Giant cloud rat (Phloeomys pallidum). This rodent grows to about 2 and a half feet long and weighs between 4 and 5 and a half pounds.

These animals can fit into very small places. Some scientists believe that if the animal can fit its head into a hole, it can get the rest of its body through. This is one of its defenses against predators. They also have very sharp teeth that they use to defend themselves against attack. In addition, their black, brown, or gray fur helps them to blend in with the dark underground environment.

These rodents are social creatures. In fact, if the animal is left alone for any span of time, it can become listless and depressed. Wild rats are shy and try to avoid being seen by humans or other animals. Pet rats can be very friendly and playful if raised around people.

A group of rats is called a mischief and can contain a dozen or more members.

Rat vs Mouse: What is the Difference?

Rats and mice both fall under the Muridae family, but there are several differences between these two rodents.

One of the main differences between them is size. Mice are smaller than rats. A mouse weighs about 0.4 to 1 ounce.

Another difference is that a mouse has hair on its tail while a rat’s tail is hairless.

The lifespan of a wild house mouse is usually less than a year, whereas a rat can live up to 3 years.

Habitat

These rodents live throughout the world. They live in India, Asia, North America, South America, Europe, and Australia. Humans have even introduced some rats to the continent of Antarctica. These animals live in warm to temperate climates. Simply put, wherever humans live, there are sure to be some rats nearby.

These animals are adaptable to a variety of habitats. Some live in trees while others live in nests, attics, and basements of homes. They live in drain pipes, in city sewers, and near rivers. Many of them live underground most of the time and come out of their hiding place to look for food.

A rat uses its whiskers to safely navigate its way through dark tunnels and narrow spaces. Their whiskers are doubly important because these rodents are nocturnal.

These rodents need to live in warm areas. So, when the cold weather arrives, they leave fields and wooded areas, moving into homes, buildings, sheds, and other structures.

Diet

What do rats eat?

They are omnivores, so they eat both plants and animals. They eat fruit, nuts, seeds, insects, small animals, and eggs. The specific diet of these animals depends a lot on the food available in their habitat.

A rodent that lives in the woods may eat mostly seeds, nuts, and fruits. Alternatively, a rat that lives in a city sewer is likely to eat meat, bread, and other items it finds in trash cans or on the street. A rodent that lives on the shore near a river is likely to eat bird eggs, baby turtles, fish, and other small animals.

The rodents that eat from garbage cans are at risk of ingesting items that make them sick. Expired or rotting food is two examples of items that would make a rat sick. However, they have an excellent sense of smell, so they’re good at avoiding spoiled food.

Predators and Threats

What eats rats?

Hawks, owls, and falcons are all predators of these animals. Domestic dogs and cats can also be threats to these rodents.

Black rats that build nests in the attics or basements of homes are at risk of being killed by an exterminator. But despite being thought of as a pest, the overall population of these animals remains stable.

As a note, the Northeastern Xanthurus species has a conservation status of Least Concern. These rodents live in Indonesia and are threatened by loss of habitat due to logging activity and farming.

These animals have a reputation for spreading disease to humans and other animals. They can indeed spread disease if they bite a human or another animal. Disease can also be spread when a human touches a dead rat or comes in contact with rat feces. Plus, fleas and ticks on these animals can contract a disease from them and spread it to animals and humans.

Some of the diseases these animals carry include:

• Salmonellosis: Contracted by ingesting the rodents’ feces
• Tularemia: Contracted through fleas or ticks that have been on a contaminated animal
• Plague: Contracted through a bite from a flea that has been on an infected animal

Notably, the plague and rats are historically connected. The Bubonic plague spread in the Middle Ages, killing millions of people in Europe. Fortunately, things have changed since then. This disease can be treated with modern antibiotics.

As with most rodents, these animals are vulnerable to respiratory infection and disease. One respiratory ailment of theirs is caused by bacteria called Mycoplasma.

Also, rodents that don’t chew enough food and other materials can suffer from overgrown teeth. Having teeth that are overgrown can interfere with a rat’s ability to get enough nourishment.

They can also develop tumors in their body.

Reproduction, Babies, and Lifespan

Generally, the breeding season of the black rat takes place in summer and fall, but these animals have been known to breed at any time throughout the year. Each pack, or mischief, has a dominant male that mates with several females. These rodents have multiple mating partners. The dominant male fiercely defends his pack during the breeding season.

A female makes a nest out of whatever material she can find. Leaves, shredded paper, insulation, cardboard, and grass are just some of the materials. She can make her nest almost anywhere. One animal may build a nest in a burrow in the woods while another chooses a corner of an attic.

A female can have as many as 5 litters of babies per year. Her gestation period runs from 21 to 29 days. She can have 8 to 12 babies in one litter.

The babies, or pups, are born without any hair, and their eyes are closed. They have tiny pink bodies that weigh less than an ounce. As mammals, females nurse their young. The male doesn’t provide any care for the pups.

A pup’s eyes open when it is 15 days old. They begin to eat solid food and grow their fur coat at 3 weeks old. Pups are independent by the time they are 4 weeks old.

These rodents are sexually mature at 3 to 5 months old. They have a lifespan of 2 to 3 years.

Population

According to the IUCN Red List of Threatened Species, the black rat has a widespread and abundant population. Its numbers are holding steady.

The black rat lives throughout the southeastern United States and down into Mexico. This animal is also found in Massachusetts up into British Columbia.

Rats in the Zoo

• Domestic rats are on display at the Seneca Zoo
• Visit the rat exhibit at the Smithsonian National Zoo