common mouse (Mouse muscle) is a small rodent that is found throughout the world, including some areas of Antarctica. It is quickly recognized for its pointed snout, large rounded ears, and a long, furry tail.

Common mouse
Common mouse

Species

The common mouse belongs to the Glires clade, that is, it is among the closest relatives to humans, as are lagomorphs, shrews, flying lemurs, and other primates.

Within the common mouse, there are three accepted subspecies but they are increasingly being treated as different species:

  • Southeast Asian common mouse (Mus musculus castaneus)
  • Western European Common Mouse (Mus musculus domesticus) - Including: The Fancy Mouse and the Laboratory Mouse (Western Europe, Southwest Asia, America, Africa and Oceania)
  • Eastern European Common Mouse (Mus musculus musculus)

Two more subspecies have recently been recognized:

  • Southwest Asian common mouse (Mus musculus bactrianus)
  • Common pygmy mouse (Mus musculus gentilulus)

Features

The common mouse has a length that varies between 7,5 - 10 cm (from the snout to the base of the tail) and a tail length between 5 - 10 m. The weight is about 40 - 45 g.

The adult mouse has 16 teeth that are used to hold and chew food. They are divided into an upper pair and a lower pair of incisors at the front of the mouth. They have between two and five cheek teeth that are used for gnawing, but when used, the front incisors stop moving. The front incisors are continuously growing and remain sharp and strong. To prevent them from getting too long, they should gnaw hard food.

In the wild it can be found in dark and light brown colors, but in laboratories they have been modified to obtain white, black and gray mice. It is covered by short hair, although the ears and tail have a lower density of hair.

The mouse's feet are small and flexible with nails on each of its toes, allowing it to climb. They have five toes on the hind legs and four on the front ones, which allows them to have more stability when they lean on their hind legs as they have a greater number of toes. The front legs are used to grab food and feed easily.

Like hamsters, they are able to run backwards to escape predators. In running, the stride is about 4,5 cm and is capable of jumping vertically up to 45 cm.

The vision of mice is similar to that of humans, but with differences. Humans are trichromates and have three cone cells, whereas mice are dichromatic and have two cone cells. However, it has a higher density of cones sensitive to ultraviolet rays. In 2007 it was shown that some mice genetically modified in laboratories to have a third cone, began to distinguish a range of colors very similar to that perceived by tetrachromatologists.

Smell depends on the number of pheromones used for social communication. Pheromones are produced by preputial glands in both genders. Urine and tear fluid also contain them in male mice. To detect them they use the vomeronsal organ, called Jacobson's organ, located in the lower part of the nose.

Mouse urine has a strong odor, especially in males. These odors can speed up or delay sexual maturation in young females and synchronize reproductive cycles in mature females, known as the Whitten effect. As against, the Bruce effect is capable of terminating pregnancy if they encounter the scents of an unknown male mouse.

The whiskers are used to detect the surface and the movements of the air. While they are blind, their sensitivity increases as a compensatory response.

Laboratory mouse
Laboratory mouse

Behavior

The common mouse are good jumpers, climbers, and swimmers. Normally they maintain contact with vertical surfaces, this preference is called thigmotactics.

When eating, fighting or orienting themselves they do so by leaning on their hind legs, a behavior called "tripod".

It is a nocturnal animal, therefore, it rejects bright light. They spend about 12 hours a day sleeping when they are in captivity. Nests are built near food sources in hidden places with soft materials.

The dominant male establishes a territory and lives in it with several females and young. Between males, territories are respected and they only enter if they are sure it is empty. In captivity, if two males are locked in a cage they will become aggressive, and it is possible that they will end up killing each other. To avoid this they must be raised together from birth.

Despite their similarity, the mouse exhibits a behavior called muricide, which consists of fleeing from rats, since they normally kill and eat them. Despite this, they are able to live together.

They are generally poor competitors, that is, they are unable to live far from human settlements. However, in parts of Australia they are capable of living with other rodents.

Social behavior

The common mouse does not have a fixed behavior, but its behavior varies according to the place where it lives, the availability of food and the space.

Their social behavior can be divided into two, classified according to the environmental context. In buildings and urban areas very close to human beings the behavior is called "commensal". Here the populations have abundant food, which brings high populations concentrated in the same area. When populations are very large due to excess food, there are fewer confrontations between males and females. Although they are not exceptions, since female couples and territories will always be defended.

Commensal mice are organized into small groups of one male and several females (usually related). The group reproduces cooperatively, with the females nursing in the community, increasing reproductive success. When there are no twinned females, non-twinned breeding groups are formed.

In open areas such as fields, common mice are known as noncommensal. These mice are limited by limited resources and have large territories. Aggression between members, both male and female, is much higher than in commensal mice. In commensal populations, encounters between males occur very frequently, but they tend to avoid aggressions because the risk of injury is greater.

Both types of male mice fiercely defend their territories from intruders. The territory is marked by urine, and in them the intruders show less aggression than the resident male.

When males become adults, they leave the birthplace in search of new territory, while the females stay there, and are opportunistic rather than seasonal breeders.

Habitat

The common mouse inhabits a wide variety of ecosystems. It can be found in and around buildings, as well as in open fields and on farmland.

Distribution

The common mouse is distributed throughout the world, with the exception of some areas of the poles.

Food

The common mouse is a herbivorous animal and eats all kinds of vegetables. They also feed on their own feces to absorb nutrients that are produced in their intestines by bacteria.

Like all rodents, mice do not vomit.

Predators

The mouse has small mammals, birds and reptiles as predators. However, it is usually easy prey. Therefore, it does not usually last more than a couple of months in the wild. When kept as a pet, it can live a few years.

Reproduction

The mouse has an estrous cycle lasting between four and six days, with a heat duration of less than one day. If several females huddle together in one place, they may not go into heat. If they are exposed to male urine, they will go into heat after 72 hours.

They tend to practice polygamy and polyandry to maximize survival success and enhance genes, which is why they often avoid monogamy. The female reaches sexual maturity faster than the males, at six weeks, while the males do so at eight weeks, but both genders can begin to copulate at five weeks.

When in heat, males court females by using ultrasonic calls emitted in a range between 30 - 110 kHz. The calls are very frequent while following the female and last until after mating. Males are induced to emit these calls by female pheromones. The calls are different between different individuals and are as complex as that of birds. Although females can also make calls, they do not do so during mating.

At the end of copulation, the female develops a plug that prevents re-copulation. The plug is not necessary for early pregnancy, as it occurs without the plug, and remains in place for about 24 hours.

They have a gestation period of less than a month and the female gives birth, an average of about six young, although most of the time it is usually longer. It can have several litters a year, so mouse populations can increase rapidly. However, they do not reproduce in the colder months.

Baby mice are born hairless, without ears, and with their eyes closed. The ears take to fully develop in four days and the hair begins to appear after six days and the eyes open after 13 days. At three weeks of age they are weaned.

State of conservation

The mouse is not in danger due to its high adaptability to all environments and high reproduction rates.

Relationship with humans

Some people keep the mouse as a pet, due to its small size and docility. It is also widely used in scientific research.

Sometimes they can become a big problem for humans, forming large pests that damage crops and spread diseases through their parasites and feces. Cats are believed to have been brought into homes to avoid these pests.

Popular culture

The mouse has been the cause of numerous plagues, which has led to various rituals and stories throughout the world. Ancient Egypt had a story called "The Mouse as Vizier."

Some South Slavs celebrated "Mouse Day" annually. In some countries the tradition of the «Tooth Fairy» is celebrated, based on a fictional mouse that offers sweets, money or other gifts, in exchange for children putting the milk tooth under their pillows.

The most famous mouse is probably Disney's Mickey Mouse. It was created on November 18, 1928 and is present in thousands of films, it even has merchandising and theme parks.

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