House Mouse

## Description

The house mouse (Mus musculus ) is a small mammal of the order Rodentia, characteristically having a pointed snout, large rounded ears, and a long and almost hairless tail. It is one of the most abundant species of the genus Mus. Although a wild animal, the house mouse has benefited significantly from associating with human habitation to the point that truly wild populations are significantly less common than the semi-tame populations near human activity.

The house mouse has been domesticated as the pet or fancy mouse, and as the laboratory mouse, which is one of the most important model organisms in biology and medicine. The complete mouse reference genome was sequenced in 2002.

## Appearance

One of the most abundant and widespread mammals around the globe, the House mouse is found in almost any part of the world (except with Antarctica) due to human travel. This rodent has originated in Iran, Afghanistan, Pakistan, and northern India. Along with many other major animals, it is thought to have appeared around 500,000 years ago, in the Cambrian Period. Firstly, a mouse-like fossil was found in China. This turned out to be the earliest known ancestor of the House mouse and generally, all placental mammals, even humans. During the Early Cretaceous Period, about 125 million years ago, when birds began to emerge, there came to be an animal called 'Eomaia scansoria', who was a contemporary of dinosaurs. In course of time, the House mice have managed to occupy nearly all habitats with a constant source of food. They usually live 1 - 1.5 years in the wild and about 2 years in captivity, but can live up to 6 years.

## Distribution

Firstly appearing on the steppes of central Asia and, probably, the Mediterranean region, the House mouse has become commonly widespread worldwide, being introduced by humans. This rodent is a commensal, sharing its habitat with humans. In urban areas, this animal is commonly found in houses, shops, malls, warehouses, factories, coal mines, and, occasionally, cold stores. Meanwhile, those in rural areas occupy farm buildings, rubbish tips, piggeries, poultry houses, granaries, and open fields. They typically construct their nests in secluded places such as woodpiles, beneath floors, or behind rafters. Individuals in the wild prefer living in crevices in rocks or in burrows, usually located underground; they can also be found in coastal sand dunes, salt marshes, and scrubby areas.

## Behavior

The House mouse is generally a nocturnal animal, although it can be active diurnally during food shortages. Moving around, they rely on their speed and agility to remain unspotted and escape predators. The only purpose they travel is to get food. They usually forage within a small territory of around 30 feet in diameter, every time using the same paths. The House mice may be either solitary or social. Social units of this species consist of a single male as well as several females with their young. Each such group has its own territory, fiercely defending it against intruders. These rodents don't undergo hibernation and remain active throughout the year. The House mice are widely known for their agility. They are excellent swimmers and accomplished jumpers. In addition, they possess a perfect sense of balance. When communicating with conspecifics, the House mice primarily use scent along with well-developed senses of hearing and smell.

## Diet

House mice are omnivores. Individuals in the wild mainly feed upon seeds, fleshy roots, leaves, stems, and other vegetation material, supplementing this diet with insects such as beetle larvae, caterpillars, and cockroaches as well as meat, including occasional carrion. Those in urban areas often share a human diet. In addition, these rodents are known to use household materials such as glue or soap.

## Reproduction

House mice have a polygynous mating system, which means that one male mates with multiple females. About 30% of individuals in the wild exhibit a polyandrous mating system, where each female has multiple mates during the breeding season. Mating occurs year-round with a peak period, lasting from late spring to early autumn, especially in populations, inhabiting northern parts of their range. When conditions are favorable, females may yield as many as 5 - 10 litters per year, each one containing 3 - 12 young with an average of 5 - 6. Moreover, there have been known cases of females, producing up to 14 litters in a single year. The duration of pregnancy depends on whether the female is lactating or not. Usually, gestation period lasts 19 - 21 days in non-lactating females and longer - in lactating ones. Newborn babies of this species are blind and lack fur. They attain their coat at 10 days old, opening their eyes by 14 days of age. Weaning occurs at 3 weeks old, and the age of sexual maturity is 5 - 7 weeks old.

## Population

### Population threats

On one hand, House mice are killed in large numbers in scientific research. On the other hand, these animals are persecuted and killed around the globe due to being considered pests for a number of reasons: they consume stored grains; their burrows often damage root crops; these rodents move into homes, thus disturbing humans; and finally, these mice carry multiple diseases that are very dangerous to humans. As a result, millions of mice are killed annually.

### Population number

According to IUCN, the House mouse is common and widespread throughout its range but no overall population estimate is available. However, according to the People’s Trust for Endangered Species resource, Great Britain's population size is around 5,400,000 individuals. Overall, House mice’s numbers are stable today, and the animals are classified as Least Concern (LC) on the IUCN Red List.

### Ecological niche

The House mice play a very important role in the ecosystem of their habitat. Firstly, these animals are a key prey species for local predators. Secondly, consuming weed seeds and insects, they keep them under control, thus benefiting the local ecosystem.

## Domestication

The first written reference to mice kept as pets occurs in the Erya, the oldest extant Chinese dictionary, from a mention in an 1100 BC version. Human domestication led to numerous strains of "fancy" or hobby mice with a variety of colours and a docile temperament. Domestic varieties of the house mouse are bred as a food source for some carnivorous pet reptiles, birds, arthropods, and fish. The effects of domestication can be rapid, with captive-reared mice differing in boldness and activity patterns compared to wild-caught mice after 4–5 generations in recent research.

## Fun Facts for Kids

The House mice are otherwise known as 'dancing mice' because of genetic strain with inner ear defects, due to which these rodents can often be observed weaving, making circles, and wobbling while walking. This species is also called a 'singing mouse' as a reference to the pathological condition, making the animal continuously give out cricket-like vocalization, which sounds like a "song".

These small animals eat as often as 15 - 20 times per day.

Each individual produces 40 - 100 droppings in a single day.

All senses of the house mouse are well-developed, except for eyesight, which is very poor. Hence, this animal sees best in dim light conditions.

Each night, the house mouse takes as many as 20 - 30 foraging trips to various food sites, taking about 0.15 g of food each time.

Ears of this animal are capable of perceiving ultrasound up to 90kHz. Moreover, the house mice use ultrasound when communicating with conspecifics.