Mus musculus Linnaeus, 1758

House mouse

The small, curious rodent that lives inside our walls and pantries.

Order: Rodentia
Family: Muridae
Group: Rodents
Ontario status: Established, ubiquitous commensal

Why it matters

Contaminates food and surfaces with droppings and urine; gnaws wiring (fire risk); can carry Salmonella and leptospirosis.

Origin

Native to the steppes of Central Asia; spread worldwide with agriculture and shipping, now the most widespread wild mammal on Earth.

Behavior

Nocturnal; curious rather than fearful, unlike rats, it investigates new objects quickly. Home range just 3-10 m indoors; an excellent climber and gnawer.

Living conditions

Indoors wherever food meets shelter: wall voids, pantries, attics, basements, clutter. Needs only ~3 g of food per day and nests within a few metres of it.

Signs of presence

Rod-shaped droppings 3-6 mm with pointed ends, along walls and in cupboards
Gnaw marks on food packaging, wood, and wiring
Musky urine odor and rub marks in heavy infestations
Squeaks and scurrying in wall voids at night

Weaknesses

Curiosity defeats it, it investigates new objects fast, which is why monitoring works
Tiny home range: control the 10 m around the nest and you control the mouse
Must eat daily, removing the 3 g/day food base starves it out

Myths and facts

Myth Mice only enter dirty homes.
Reality Mice enter any home with a gap ≥6 mm and nearby food. Cleanliness reduces attraction, but a mouse fits through a hole the width of a pencil.

Research notes

Morphology

Body 70-100 mm, tail 70-100 mm (about equal to body), weight 12-30 g. Grey-brown above, paler below; large ears, pointed muzzle. Droppings 3-6 mm, rod-shaped, pointed ends, the key field diagnostic.

Diagnostics

Droppings shape and size; gnaw marks ~1-2 mm wide; tracks in dust. Separated from deer mouse by uniformly grey-brown fur (no white underparts) and unicolored tail.

Easily confused with

Deer mouse (Peromyscus maniculatus) Deer mouse has sharply contrasting white underparts and a distinctly bicolored tail; house mouse is uniformly grey-brown.
Juvenile Norway rat Young rats have blunter muzzles, thicker tails, and droppings ≥10 mm even as juveniles.

Life cycle

Adult: Lifespan ~12 months in the wild; up to 2-3 years in captivity
Egg: N/A, viviparous
Egg to adult: Gestation 19-21 days; birth to breeding maturity 5-8 weeks
Generations per year: 5-10+ indoors (year-round breeding)
Nymph or larva: Pups weaned at ~21 days; sexually mature at 5-8 weeks

Development

Viviparous; altricial young, born blind and hairless.

Reproduction

5-6 pups per litter × up to 8-10 litters/year indoors.

Distribution

Global: Cosmopolitan; most widespread wild mammal
Native range: Central Asian steppes
Ontario: Established, ubiquitous in and around structures province-wide

Ecology

Commensal obligate in temperate climates; polygynous family groups with male territoriality; thigmotactic, travels along walls and edges.

Resistance

Anticoagulant resistance documented via VKORC1 mutations in multiple global populations.

IPM implications

Curiosity plus a tiny home range means monitoring along wall edges within 3-10 m of signs gives fast answers. Exclusion at ≥6 mm gaps removes entry; sanitation removes the food base. Thigmotaxis dictates placement along perimeters, never mid-room.

Chemical ecology

Urine marking with major urinary proteins (MUPs); scent trails guide foraging; male territorial marking.

Genetics and DNA

The mammalian model organism, genome published 2002 (Mouse Genome Sequencing Consortium, Nature); the most genetically characterized mammal on Earth.

Taxonomy

Order Rodentia › family Muridae › genus Mus › M. musculus (Linnaeus, 1758). The laboratory mouse is the domesticated form of this species.

Open questions

VKORC1 resistance allele frequency in Ontario commensal populations is unmapped.

References

UC IPM, House Mouse (ipm.ucanr.edu)
Penn State Extension, House Mouse Biology and Management