# House Mouse — Facts, Threats & Conservation

*Mus musculus*

> A house mouse (Mus musculus) is a small grey-brown rodent in the family Muridae, typically 7.5–10 cm long with a long tail and large ears. Native to Asia, it now lives worldwide alongside humans, breeds prolifically, and is the ancestor of pet and laboratory mice.

**IUCN status:** Least Concern (IUCN)  ·  **WARN range:** Worldwide (alongside humans), Europe, Asia, Africa, Americas

## Quick facts
| Fact | Value |
| --- | --- |
| Common name | House mouse |
| Scientific name | Mus musculus |
| Family | Muridae (rodents) |
| Body length | 7.5–10 cm (plus a 5–10 cm tail) |
| Weight | 11–30 g |
| Diet | Omnivorous; mainly seeds and grains |
| Lifespan | Under 1 year wild; 2–3 years protected |
| Distribution | Worldwide, alongside humans |
| Activity | Mainly nocturnal |
| IUCN status | Least Concern |

## Scientific classification
- **Kingdom:** Animalia
- **Phylum:** Chordata
- **Class:** Mammalia
- **Order:** Rodentia
- **Family:** Muridae
- **Genus:** Mus
- **Species:** Mus musculus

## Conservation status
- **Status:** Least Concern (IUCN Red List). The house mouse is one of the most abundant and widespread mammals in the world, occurring on every inhabited continent in close association with humans. Its population is enormous and stable, and it faces no conservation threats; where it is managed at all, it is usually treated as a pest rather than a species at risk.
- **Population:** Not quantified, but among the most numerous mammals on Earth — many hundreds of millions to billions worldwide.
- **Trend:** Stable
- **Assessed:** 2016
- **CITES:** Not listed under CITES.
- As a commensal species that thrives wherever humans live, the house mouse benefits from, rather than suffers from, human activity, and requires no conservation intervention.

## Key facts: House Mouse
- The house mouse is one of the most abundant and widespread mammals on Earth, found wherever humans live.
- It is small and light — usually 7.5–10 cm in body length and just 11–30 g in weight, with a tail roughly as long as its body.
- Mice breed prolifically: females mature at around six weeks and can raise several litters a year.
- Most wild mice live less than a year because of heavy predation, though protected mice can reach two to three years.
- Mus musculus is the wild ancestor of both pet and laboratory mice, making it one of science's most important animals.
- The IUCN classifies the house mouse as Least Concern, with a huge and stable global population; it is not CITES-listed.

## What does a house mouse look like?
A house mouse is a small, slender rodent built for squeezing through tight spaces. The body measures roughly 7.5–10 cm from nose to the base of the tail, with a near-hairless tail of similar length, 5–10 cm. Adults typically weigh between 11 and 30 grams — lighter than a £1 coin. The fur is usually grey-brown above and paler beneath, though colour varies. The most distinctive features are the large, rounded, sparsely furred ears and the prominent dark eyes, which give the mouse keen senses in low light. Long whiskers help it feel its way along walls and through burrows in the dark. The front paws have four clawed digits and the hind paws five, well suited to climbing, gnawing and grooming. Mice see relatively poorly but have an acute sense of smell and hearing, including ultrasonic frequencies humans cannot detect, which they use to communicate. Their continuously growing incisors — a hallmark of all rodents — must be worn down by constant gnawing, which is why mice readily chew through packaging, wood and soft materials.

## Where do house mice live and what do they eat?
House mice are commensal animals, meaning they live in close association with people. Although the species originated in Asia, it travelled with human trade and settlement to become established on every inhabited continent. Mice colonise houses, barns, granaries, shops and warehouses, but also live independently in fields, hedgerows and grassland, especially in warmer months. They are adaptable nest-builders, shredding paper, fabric and plant material to make snug nests in wall cavities, under floors or in burrows. Mice are largely nocturnal and stay close to shelter, typically foraging within a small home range. They are omnivorous but feed mainly on plant matter — seeds, grains, roots and stems — supplemented by insects and almost any human food they encounter. A mouse needs very little water and can obtain much of its moisture from food, which helps it survive in dry stored-grain environments. This close relationship with people brings the species into frequent conflict with humans over stored food and property, but it is also the reason the house mouse has become so extraordinarily successful and widespread.

## How do house mice breed and how long do they live?
The house mouse is famous for its rapid reproduction. Females reach sexual maturity at around six weeks of age and males at about eight weeks. After a short gestation of roughly 19–21 days, a female gives birth to a litter of 3–14 young, with six to eight being typical. The pups are born blind, hairless and helpless, but develop quickly and are weaned within about three weeks. A single female can produce 5 to 10 litters in a year under good conditions, so populations can grow explosively when food and shelter are plentiful. This high reproductive rate is balanced by heavy losses: in the wild, most mice live less than a year because of intense predation by owls, hawks, foxes, cats, snakes and many other animals, making the house mouse a key link in many food chains. In protected conditions, such as a home cage or laboratory, mice commonly live two to three years. The species' fast life cycle, small size and ease of care are exactly why it became the foundation of the pet mouse and the laboratory mouse.

## Are house mice the same as pet and lab mice?
Yes — pet mice ('fancy mice') and laboratory mice are domesticated strains of the wild house mouse, Mus musculus. Over many generations, selective breeding has produced an enormous variety of coat colours, patterns and temperaments in fancy mice, and highly standardised, genetically defined strains in laboratory animals. The laboratory mouse is one of the most important model organisms in biology and medicine: its short life cycle, small size and close genetic similarity to humans have made it central to research on genetics, immunology, cancer and countless diseases. It is worth distinguishing the house mouse from other small rodents people often confuse it with. Mice are generally smaller and more slender than rats, with proportionally larger ears and thinner tails. They differ too from voles, which have blunter snouts, smaller ears and shorter tails, and from shrews, which are not rodents at all but insect-eaters with long pointed noses. Understanding these differences helps people identify the animals sharing their environment — and appreciate that the unassuming house mouse underpins both a popular pet and a cornerstone of modern science.

## Mouse vs rat: how to tell them apart
| Feature | House mouse | Rat |
| --- | --- | --- |
| Body size | Small, 7.5–10 cm | Larger, 15–25 cm |
| Weight | 11–30 g | Often 200–500 g |
| Ears | Large relative to head | Smaller relative to head |
| Tail | Thin, hair-like, body-length | Thick, scaly, shorter than body |
| Droppings | Small, rice-grain sized | Larger, capsule-shaped |
| Family | Muridae | Muridae |

## What WARN does
WARN does not run field conservation projects for the house mouse — it is an abundant, Least Concern species that needs no rescue effort, and this guide is part of WARN's free educational work to help people understand the animals around them. The same forces that shape mouse populations, especially habitat change and the loss of natural predators, also affect the wild species WARN does help protect, which is why understanding common animals matters for conservation as a whole.

If this free guide helped you, a small gift helps WARN keep producing clear, science-based animal education and care for the wildlife that genuinely needs our help.

## Frequently asked questions: House Mouse
### What is the difference between a mouse and a rat?
Mice and rats are both rodents in the family Muridae, but mice are much smaller. A house mouse weighs only 11–30 g with a slender body, large ears and a thin, hair-like tail, while rats are far heavier and bulkier with proportionally smaller ears and thicker tails. Mice also tend to produce smaller droppings. Both can live alongside humans, but they are distinct species.

### How long do house mice live?
In the wild, most house mice live less than a year because of intense predation by owls, foxes, cats, snakes and other predators, as well as harsh weather and food shortages. In protected conditions, such as a home, pet cage or laboratory, where they are safe from predators, house mice commonly live two to three years. Their fast life cycle is balanced by these high natural losses.

### How fast do mice breed?
Very fast. Female house mice can reproduce from around six weeks of age, and after a gestation of just 19–21 days they give birth to litters of 3–14 young, typically six to eight. A single female can raise 5 to 10 litters in a year under good conditions. This high reproductive rate allows mouse numbers to grow rapidly when food and shelter are plentiful.

### What do house mice eat?
House mice are omnivorous but feed mainly on plant matter such as seeds, grains, roots and stems. They will also eat insects and almost any human food they can reach, which is why they are drawn to kitchens, granaries and food stores. Mice need very little water and can get much of their moisture from food, helping them survive in dry environments like stored grain.

### Are pet mice and laboratory mice the same as house mice?
Yes. Both pet 'fancy' mice and laboratory mice are domesticated strains of the wild house mouse, Mus musculus. Generations of selective breeding have produced many coat colours in fancy mice and genetically standardised strains for research. The laboratory mouse is one of the most important model organisms in biology and medicine, used to study genetics, cancer, immunology and many human diseases.

### Are house mice endangered?
No. The house mouse is one of the most abundant and widespread mammals on Earth, found on every inhabited continent wherever humans live. The IUCN Red List classifies it as Least Concern, with a very large and stable global population, and it is not listed under CITES. Far from being threatened, the species is so successful that it is often considered a pest where it shares human food and homes.

## Sources
- [Wikipedia — House mouse](https://en.wikipedia.org/wiki/House_mouse)
- [IUCN Red List — Mus musculus](https://www.iucnredlist.org/species/13972/115117618)
- [Encyclopaedia Britannica — Mouse](https://www.britannica.com/animal/mouse-rodent)
- [Animal Diversity Web — Mus musculus](https://animaldiversity.org/accounts/Mus_musculus/)
- [Wikipedia — Laboratory mouse](https://en.wikipedia.org/wiki/Laboratory_mouse)
- [CITES — Checklist of species](https://checklist.cites.org/)

---
Full guide: https://worldanimalrescuenetwork.org/wildlife-guides/mouse