Rats vs Mice

What are the differences?


If you have seen an actual rodent in your home, or found evidence of one, such as droppings, the first step in getting rid of it is to determine if it is a rat or a mouse. Although they may have descended from the same ancestors living millions of years ago, rats and mice are not the same species of mammal. Both rats and mice have front teeth that are used for gnawing, and they chew with their cheek teeth. They will gnaw or chew on anything they have access to, including cables and wires in your home. There are many differences between rats and mice.

Norway Rats and Roof Rats

The most commonly found rats in houses are Norway rats, also called brown rats, and there are also Roof rats, which are sometimes referred to as black rats. Norway rats originally lived in forest regions with temperate climates, but they have adapted to life in populated cities; in the United States, they primarily live in the northern states. Roof rats originate from the tropical regions of Asia, but have since spread throughout the world. In the United States, Roof rats are typically found in the warmer, southern states.

Norway Rats

Appearance, Senses, and Habitat

Although they are commonly referred to by the name “brown rats,” Norway rats can also be grey in color, and their under parts are a lighter shade. Males weigh an average of 16 ounces, and females average 12 ounces; however, some adult Norway rats can weigh up to 32 ounces. They have large bodies that grow as long as 10 inches, and their tails can be as long as 6 inches. Norway rats have coarse, shaggy fur, and they have scales on their tails and ears. They have small ears and eyes and slanted snouts. They are also called sewer rats, street rats, and Hanover rats. 

In addition to being colorblind, Norway rats have very poor vision. They make up for their lack of sight with their highly acute sense of hearing, and they can also sense ultrasound. They also have an acute sense of smell, which helps them to seek out food sources. 

Norway rats live on every continent except Antarctica. They can be found wherever humans live, especially in highly populated cities where they have plenty of access to shelter, food, and a water source. Although they typically burrow underground and venture into buildings at night looking for food, they will take up residence inside a building, especially if they have access to water. In a home, they will colonize in crawl spaces, basements, sewers, and attics. They can cause considerable damage with their gnawing, chewing and burrowing.


Norway rats are omnivores, so they will eat both plants and animals. They prefer grains, cereals, and nuts, but they will eat meat or any other food they encounter. They can catch fish and smaller rodents, and they will eat dead animals as well. Norway rats must drink water, as they can’t get proper hydration solely through food, so they will always colonize close to a water source. In cities, they often colonize in underground sewers systems.


Norway rats mature at the age of two months, and they can breed year round in suitable conditions. The female will have between eight and twelve babies at one time, and she can have as many as eight litters per year, but the average is about five. Females are very maternal when lactating, but they will tend to smaller litters better than to larger ones. Most Norway rats live an average of one year.


Norway rats live in hierarchical colonies, where one rat is the most dominant, and there are several levels of dominance below him. If there is a lack of food in their habitat, the rats at the bottom of the hierarchy will be allowed to starve to death while the rats at higher levels of dominance feed. They will also fight over living space if their colony becomes overpopulated; the weaker, less dominant rats are killed to allow more room for the others. 

Norway rats sleep together and groom each other. They also play fight with each other, rolling, tumbling, and nipping at each other much like cats and dogs do. Norway rats are also great swimmers. They are nocturnal and will stay in their burrows during the day unless they must come out for food. Their burrows are often long and multi-tunneled, and they may make multiple entrances into it. They sleep and store their food in their burrows, and will hide in them if they are startled by a noise or an intruder comes near.

Roof Rats

Appearance, Senses, and Habitat

Roof rats have black or light brown bodies and a lighter colored underside. Their fur is coarse. They have smaller, narrower bodies than Norway rats, and they grow to an average of ten inches long with a tail almost as long as their body. They weigh between six and twelve ounces. Roof rats have pointed snouts, big, rounded ears, and big eyes. Other names for Roof rats include ship rat, house rat, and Old English rat. 

Like Norway rats, Roof rats are colorblind and can only sense differences in shades of objects. They have an acute sense of smell, which they use to locate food and to distinguish among other members of their colonies, particularly those of the opposite sex. They also use their sense of smell to locate their travel routes. They have highly sensitive whiskers that they use to help guide them through narrow areas and along walls. They also have very good balance, and they are capable of climbing along narrow wires and similar objects, using their long tails to help keep them balanced. 

Roof rats live in agricultural environments as well as populated areas. They are rarely found in sewers and similar settings, as they prefer higher nests. They will often colonize a building or home on its upper levels. Roof rats can access upper levels of buildings via trees and utility lines. In addition to attics, they will colonize inside of walls and in false ceilings. Although they will burrow underground if needed, they prefer to build round nests of leaves, sticks, and any other material they can shred.


As with Norway rats, Roof rats are omnivores. However, most find a diet of plants and vegetation sufficient. They often get into pet food and livestock feed, but they tend to prefer nuts and fruits. They will eat insects and birds as well. They are foragers, and they rarely deplete a food source. Instead, they will eat a little and store a little, especially if the food can’t be eaten quickly, and they will then move on to a different food source. They have a diet with higher water content than Norway rats, and therefore don’t necessarily need access to water all the time. 


Roof rats mature at about three months of age, at which point they are capable of reproduction. The gestation period of a female is about three weeks. She will have between five and eight babies per litter, and may have up to six litters per year. The babies are hairless at birth, but grow hair within a week. The young will nurse for about five weeks, at which point they can begin foraging for and eating regular foods. Although spring and fall are the most typical times for breeding, if circumstances are suitable, Roof rats can reproduce year round.


There is a hierarchy among Roof rats similar to that of Norway rats. The more dominant rats have better living areas and access to more food than those who are lower in the hierarchy. The less dominant rats will also be kicked out of the colony if a lack of space becomes an issue. Because of this hierarchy, there may be several nests in a given home or building. In addition, Roof rats are much harder to control and remove from buildings if an infestation occurs because of their tendency to get inside of walls to nest. 

Roof rats aren’t good swimmers like Norway rats, but they are excellent climbers, and they are much faster than Norway rats. They are nocturnal, and they will do most of their foraging and nest building at night. If they can access indoor shelter to build a nest in, they will choose the shelter over making a burrow underground. 

House Mice

Appearance, Senses, and Habitat

A house mouse is the most likely mouse to make a home inside of a building. They are typically between three and four inches long, with a tail between two and four inches long. They are various colors, including white, grey, and brown. Darker colored house mice will have lighter underbellies. Their fur is short, and they have only a small amount of hair on their ears and tails. They have shorter hind feet than other species of mice, and they can jump as high as 18 inches.

House mice cannot sense color, as with rats. They have an extraordinary sense of hearing however, and can hear in the ultrasound range. They have an acute sense of smell, and rely heavily on pheromones to sense the other mice in their colony. They can sense the pheromones present in urine, which can cause changes in reproductive cycles. They use their whiskers to help them travel at night through small spaces. 

Although house mice will live in fields or other outdoor habitats, they seek shelter indoors when possible, particularly when the weather turns colder. House mice make their homes in buildings near their food sources, usually building their nest within 20 feet of their food supply. They shred paper, cloth, and similar materials to form their nests. Females tend to stick close to their nests with the young while the males retrieve food. 


House mice are omnivores, but they usually eat plants rather than animals. They prefer grains, but like most rodents, they will eat whatever food source they can find. Because they are so small, they can access cupboards and pantries and get into food supplies stored there. Even though they may eat very little, they contaminate everything that they come in contact with, and leave droppings as well. They will sometimes eat their own droppings as a source of nutrition. 


A pregnant female house mouse has a gestation period of about three weeks. She will give birth to an average of five to eight babies; however, litters as large as 14 are possible. The babies are born without hair, which will start growing when they are three days old. Males mature at eight weeks and females at six, but they are capable of reproducing as early as five weeks of age. A female can have up to ten litters per year, though six is the average. If indoors, house mice will reproduce year round. Outdoors, they do not reproduce when the weather is cold. House mice can live up to two years indoors. 


House mice are excellent jumpers, swimmers, and climbers. When they are eating, they will stand on their hind legs. They also stand on their hind legs when they are aggressive, such as when they come in contact with another mouse or a predator. They usually run with their tails straight up to help them stay balanced, but if frightened their tails will be down when they run. They are nocturnal, so they do most of their food foraging and nest building at night and away from light sources.

A male house mouse will typically live with several females. Males are very territorial and usually don’t cohabitate with other males. If house mice have found entrance into your home, it is likely that there will be more than one nest of mice. Less dominant males will avoid the territory of a dominant male most of the time. Males can be quite aggressive with each other and with predators. Females are much more docile and usually remain close to the nest with their young.

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