Mouse

Quick Take

• Mice are famous for loving cheese, but the reality of what they actually want is completely different. See what mice really eat →
• A single female mouse can produce a number of offspring in one year that would genuinely shock most people. Explore their breeding rate →
• Mice have been living alongside humans far longer than anyone assumed, a fact whose underlying reason completely changes how we think of them as pests. Trace their history with humans →
• These tiny animals can do things physically that most people would never expect from a creature that fits in your palm. Discover their physical abilities →

The mouse is a small animal in the order Rodentia, with the most well-known species being the common house mouse.

These mammals all have small bodies, rounded ears, a pointed snout, a long tail, and a high breeding rate. While the field mouse is well-known for invading homes for food and shelter, the house mouse is the most common rodent household pet in the U.S.

The domesticated house mouse is called a fancy mouse and is one of the most popular rodent pets. Whether this animal is considered a pest or a pet depends on its lifestyle and treatment. As mammals, mice are also commonly used in experiments to test new products and medicines.

5 Incredible Mouse Facts

• These animals are gymnasts and escape artists.
• They have big appetites, eating around 20 times a day.
• They can carry at least 35 diseases, including Hantavirus and Salmonella.
• They cannot be potty-trained as pets.
• Females are ready to give birth at 2 months of age and can have up to a dozen babies per litter, with as many as 15 litters per year, yielding more than 150 offspring in one year alone.

Classification and Scientific Name

The mouse is a mammal in the animal kingdom. As a member of the order Rodentia, it is a rodent. All muroid rodents smaller than rats are called mice. True mice and rats are in the family Muridae or the superfamily Muroidea (muroid rodents), which contains more than 1,300 species and includes gerbils, hamsters, and voles. Old World mice and rats are in the subfamily Murinae, also called murines, of which there are 519 species.

Typical mice are in the genus Mus, while many species of field mice are in the genus Apodemuss. Mus contains 38 species, with Mus musculus being the type species. The scientific name of the common house mouse is Mus musculus, and the scientific name of the fancy mouse is Mus musculus domesticus.

The difference in the scientific name indicates that the fancy mouse is a domesticated version of the house mouse, bred over many generations to be docile and suitable for exhibition. There are 13 subspecies of Mus musculus.

Evolution and Origins

Where there are humans, there are mice. The two species have long been intertwined. Aristotle is credited as “the first researcher to use animals systematically for research purposes.” That was 2,400 years ago. Mice have been critical to human understanding of diseases, genetics, and our own physiology.

Their origins, however, are suspected to go back much further in time. According to National Geographic, “Conventional wisdom has said that mice and people began living together when humans learned to farm,” but research from Proceedings of the National Academy of Sciences suggests that “Mus musculus domesticus first cozied up to humans around 15,000 years ago.”

Mouse vs. Rat

Although mice and rats are both rodents, there are some important differences between the two, especially when choosing one as a pet. The most important difference is their size. In the wild, rats can reach up to 500 grams (17 1 ⁄ 2 oz) in weight and are always larger than mice. Hence, rats need a significant amount of cage space.

They are also needier than their smaller relatives, demanding human attention and affection. On the other hand, rats can be potty-trained to avoid leaving droppings everywhere when outside the cage.

There are also differences in appearance between the two. Unlike rats, mice have tails and ears the same color as their coat, which can come in a huge range of colors. All coat colors and types for the fancy mouse have the same genetics.

When it comes to rats, though, there is a variation. The common pet rat is the fancy rat, which is a standard top-eared Norway rat. The dumbo rat is the same species but with a genetic mutation on chromosome 14 caused by a recessive gene, dmbo,, leading to the “dumbo” name. This mutation results in some physical differences as well as a more docile temperament.

There are also differences when comparing the two as pests. Mice invade the home and cause damage to the structure, whereas rats tend to invade farmhouses, the spaces under houses, rubbish dumps, and sewer systems. Both carry diseases as well as parasitic insects that transmit disease, and both can bite people when cornered or near their territory, causing infection.

Rats are smarter, tougher to get rid of, and more damaging to the home, whereas some mice can be handled by the homeowners themselves using mouse traps or poison. Rats can eat mice because of their sheer size advantage.

Appearance

Any rodent called a mouse has a small body, rounded ears, a pointed snout, a long tail, a uniform coat color, and a high breeding rate. Adults weigh about 1 ounce (28 grams) and are about 2.5 to 3.5 inches (6 to 8cm) long, excluding the tail. Males are larger than females. The field mouse is slightly larger than the house mouse and has a few other physical differences.

Pet mice can come in several different possible coat colors and coat types: Agouti, self, tan, pointed, patchwork, and marked are general coat colors divided into specific tickings, while hairless, rex/frizzy, satin, longhair, and shorthair are possible coat types. The common standard for the fancy mouse is a white color with a short hair coat.

Behavior

Mice and other rodents invade an estimated 21 million homes in the United States each winter. They usually enter homes between October and February in search of food, water, and shelter. They store food near the nests, with food caches usually being within 10 feet of them. Very territorial creatures, they tend to stay within 30 feet of their nests.

Being naturally flexible, they can get into homes through a crack or hole as small as 1/4-inch. They can climb 13 inches up smooth, vertical walls and jump as high as a foot, even while running. Also, they can run 12 feet per second and swim as far as 1/2 mile.

These animals are nocturnal creatures, becoming active at night and constantly searching for new food sources. Being social creatures, they groom themselves and each other. They chase each other for fun or to show dominance during a fight. When happy, they wag their tails. Ears up mean curiosity, while ears down and back mean a defensive posture, especially when combined with stiff body language.

They may stand up to get a closer look or sniff something. They wiggle their whiskers for tactile navigation, which compensates for their poor eyesight. They grind their teeth or chew on wood and other materials to keep their incisors in check. Finally, they enjoy creating nests to sleep in and are natural burrowers.

Habitat

The most common species around are the house and the field mouse (also called the deer or wood mouse), both named by their primary habitat, although both can live in and around houses and fields. House mice are native to India, and field mice are native to Europe and northwestern Africa. Another main difference is that field mice are often found in rural areas, whereas house mice take up residence in the buildings of suburbs and cities.

Diet

These animals have voracious appetites, eating 15 to 20 times a day. Their diets in nature are omnivorous but largely herbivorous, consisting of fruits, grains, seeds, corn, oats, roots, leaves, grass, plants, and even tree bark.

They have also adapted to human food scraps and pet food, which often include meat. In captivity, they do well on the full nutrition provided by commercial pellets in combination with a variety of vegetables. Contrary to popular belief, they do not seek out cheese but will only eat it as a last resort.

Mothers will eat their young during times of famine. Also, some species eat insects. Field mice (also called deer and wood mice) eat beetles, caterpillars, grasshoppers, and leafhoppers.

Predators and Threats

To avoid predation, these animals keep their activity confined to nighttime and seek covered shelters. They have several larger mammals as predators, including foxes, snakes, lizards, frogs, weasels, skunks, hawks, owls, tarantulas, dogs, and cats. Humans are consumers of them as well, having eaten them since prehistoric times. These animals are considered a delicacy in eastern Zambia and northern Malawi as well as in China, where babies are often eaten alive.

Reproduction, Babies, and Lifespan

Females are ready to give birth at 2 months of age and can become pregnant 24 hours after giving birth. They can have up to a dozen babies every 3 weeks, and as many as 15 litters or 150 babies in one year alone.

When in heat, females dart, jump, and vibrate their ears as displays to communicate their willingness to mate. They also emit pheromones, to which males respond by emitting an ultrasonic mating call. Males often have a harem of females in their territorial range.

A baby mouse is called a pup and is born deaf and blind. The average litter size is 5 to 8, but it can be as many as 10 to 12 pups, with an average of 30 to 35 babies a year. Gestation is 19 to 21 days, with up to a week longer if the mother is still nursing another litter.

These animals become sexually mature 35 days after birth. Mothers will sometimes eat their babies during famine or in captivity, believed to result from stress, illness, overcrowding, or an inability to forage outside the nest. The lifespan of mice is 1 to 2 years in the wild. In captivity, they can live for 3 to 4 years.

Population

According to the IUCN Red List, the house mouse is of Least Concern. Their population is stable due to their high breeding rate, the variety in their diet, and their ability to adapt to other habitats.

On the other hand, beach mice are under threat. The Perdido Key beach mouse, in particular, is threatened by habitat loss, introduced predators, and a population decline due to Hurricane Ivan in 2004.

In the Zoo

There are two species you can see at zoos: You can see the cactus mouse at the Lincoln Park Zoo, the Perdido Key beach mouse at the Smithsonian’s National Zoo, and the Brevard Zoo.