House Mouse
Mus musculus
Anatomy
Identification
Distinguishing Features
- Large ears relative to head size
- Pointed snout
- Tail equal to or longer than body length
- Uniform grey-brown tail (unlike the bi-colored tail of the Deer Mouse)
- Small droppings (3-6mm) with pointed ends
- Distinctive musty odour (acetamide) detectable in enclosed spaces
Biology
Lifecycle
Sexual maturity at 6 weeks. Gestation 19-21 days. 5-10 litters/year with 5-6 young each.
Diet
Omnivorous but prefer grains and seeds. 'Nibblers' by nature—visit 20-30 food sites per night, consuming only 0.1g per visit. This explains why baits sometimes fail when competing food sources are present. Need only 3ml water daily—can survive on food moisture alone.
Nesting
Build nests in micro-environments near heat sources—behind refrigerators, inside oven insulation, near water heaters. Nests are constructed from 'soft' human materials: shredded fiberglass insulation, yarn, paper, or fabric, formed into a ball about 10-15cm in diameter. Always within 3-10m of a food source.
Signs of Infestation
Droppings
Small dark pellets (3-6mm), pointed at ends. 50-80 per mouse per day.
Gnaw marks
Small tooth marks on food packaging, wood, wires, plastic.
Rub marks
Dark greasy smears along walls and baseboards from body oils.
Scratching sounds
Nocturnal activity in walls, ceilings, under floors.
Where They Nest
- Kitchen cabinets and pantries
- Behind appliances
- Wall voids near heat sources
- Cluttered storage areas
- Garage and utility rooms
Distribution in Canada
Found in all provinces wherever humans live. Primarily indoor pest.
Active Season
Active year-round indoors. Peak indoor movement occurs during first frost (September-October in most of Canada) as mice seek thermal refuge. This 'fall pressure' is the most common time for new infestations.
House Types at Risk
This pest is commonly found in these home types
Bungalow / Ranch
High RiskGrade-level entry points around entire perimeter. Attached garages provide sheltered access.
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Crawlspace Foundation
High RiskCrawlspace provides protected harborage. Multiple entry points through foundation vents.
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Bi-Level
Moderate RiskLower level partially below grade creates entry opportunities. Utility areas attract nesting.
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Townhouse
Moderate RiskShared walls allow mice to travel between units. Difficult to control without coordinated effort.
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Condo / Apartment
Moderate RiskUtility chases and shared walls create pathways. Building-wide populations common.
View house details →Prevention
- Seal gaps larger than 6mm with steel wool and caulk
- Store food in glass or metal containers
- Eliminate clutter that provides nesting material
- Keep exterior doors closed; install door sweeps
- Remove outdoor food sources (bird seed, pet food)
Professional Treatment
Integrated approach using tamper-resistant bait stations, snap traps, and exclusion. Follow-up visits essential—mice reproduce rapidly.
Get Rodent Control ServiceFrequently Asked Questions
What does a House Mouse eat?
Omnivorous but prefer grains and seeds. 'Nibblers' by nature—visit 20-30 food sites per night, consuming only 0.1g per visit. This explains why baits sometimes fail when competing food sources are present. Need only 3ml water daily—can survive on food moisture alone.
Where does a House Mouse nest?
Build nests in micro-environments near heat sources—behind refrigerators, inside oven insulation, near water heaters. Nests are constructed from 'soft' human materials: shredded fiberglass insulation, yarn, paper, or fabric, formed into a ball about 10-15cm in diameter. Always within 3-10m of a food source.
When is a House Mouse most active?
Active year-round indoors. Peak indoor movement occurs during first frost (September-October in most of Canada) as mice seek thermal refuge. This 'fall pressure' is the most common time for new infestations.
What are the signs of a House Mouse infestation?
Droppings: Small dark pellets (3-6mm), pointed at ends. 50-80 per mouse per day. Gnaw marks: Small tooth marks on food packaging, wood, wires, plastic. Rub marks: Dark greasy smears along walls and baseboards from body oils. Scratching sounds: Nocturnal activity in walls, ceilings, under floors.
How can I prevent a House Mouse infestation?
Seal gaps larger than 6mm with steel wool and caulk. Store food in glass or metal containers. Eliminate clutter that provides nesting material. Keep exterior doors closed; install door sweeps. Remove outdoor food sources (bird seed, pet food).
How is a House Mouse treated?
Integrated approach using tamper-resistant bait stations, snap traps, and exclusion. Follow-up visits essential—mice reproduce rapidly.
Scientific Classification
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Mammalia
- Order
- Rodentia
- Family
- Muridae
- Genus
- Mus
