Pest rodent · Mus musculus · Last updated 14 August 2026
Mice
The house mouse (Mus musculus) squeezes through a 6 mm opening. 1 female produces up to 10 litters of 5 to 8 pups per year — an infestation can take hold in a few weeks.
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Mice contaminate food and surfaces with their droppings (up to 80 pellets a day) and urine. They gnaw electrical cables and packaging. As a carrier of salmonellosis, the mouse is especially problematic in food storage spaces and homes.
Identify
Signs of infestation
- Rice-grain-sized droppings, 3 to 6 mm, in drawers, behind appliances and in cupboards
- Gnawed cables, cardboard and food packaging with small tooth marks
- Nests of paper fibres, insulation or fabric in confined spaces (cupboard corner, behind the fridge)
- Slightly musky urine smell in areas used at night
Where it's found
The house mouse (Mus musculus) lives inside partition walls, false ceilings, and the gap between insulation and wall. It enters through 6 mm cracks — the width of a ballpoint pen. More agile and discreet than the rat, it can go undetected for several weeks.
Impact
Associated risks
Food contamination
The mouse urinates continuously (up to 80 drops per hour) as it moves. Every surface it crosses is potentially contaminated with Salmonella or Listeria, with no visible trace.
Fire risk
The mouse gnaws electrical wiring to wear down its incisors. Exposed cables in partition walls or the attic are an under-diagnosed cause of house fires.
Rapid multiplication
A female produces 5 to 10 litters a year of 4 to 8 pups. An untreated infestation can reach 200 individuals within 3 months in a favourable environment.
Compare
Mouse or rat: how to tell them apart?
| Criterion | Mouse (Mus musculus) | Rat (Rattus norvegicus) |
|---|---|---|
| Droppings size | 3 to 6 mm, spindle-shaped | 10 to 20 mm, pointed ends |
| Entry opening | 6 mm, the width of a pencil | 2 cm minimum |
| Reproduction | Up to 10 litters of 5 to 8 pups per year | 5 litters of 6 to 12 pups per year |
| Main damage | Food contamination: up to 80 urine drops per hour | Structural: cables, pipes, load-bearing elements |
| Detection | Discreet, can go undetected for several weeks | Heavy scratching noises, persistent ammonia smell |
Good practice
Prevention
- 01Seal every crack of 6 mm or more with compressed steel wool then sealant (expanding foam alone is gnawed through in a few hours)
- 02Store dry goods (cereals, grains, chocolate) in rigid airtight containers, never in their original packaging
- 03Remove potential nesting material: stacked cardboard, rags, accessible insulation
- 04Inspect the base of walls and cable runs every 6 months, especially after renovation work
Frequently asked questions
What you're asking
What's the difference between a rat and a mouse infestation?
Mouse droppings are small (3 to 6 mm, spindle-shaped) versus 10 to 20 mm for rats. Mice leave fine paw prints and gnaw small-diameter holes (6 mm). Rats are heavier and cause more significant structural damage.
Can a mouse get in through a tiny crack?
Yes. A mouse fits through any opening of 6 mm or more — the thickness of a pencil. Sealing entry points is an integral part of our protocol and essential to prevent recurrence.
My traps aren't working. Why?
Standard traps don't treat the colony — they catch individuals, not the 20 to 80 mice that can occupy a building. A professional treatment targets the entire population and secures the entry points.
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mice problem?
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