Droppings: the Surest Sign
Mouse droppings are small, dark and about the size of a grain of rice, with pointed ends. They are not left in one heap. A mouse drops them as it goes, so you find them scattered along the line it travels.
Look along the back edge of kitchen cupboards, in the drawer under the oven, behind the fridge and washing machine, along skirting boards and in the airing cupboard. Fresh droppings are soft, dark and slightly shiny; old ones are dry, grey and crumble when touched. Finding fresh ones means mice are active now.
Do not sweep or vacuum dry droppings, as that lifts dust into the air. The right way to clear them is set out on our droppings and hygiene page.
Gnawing on Food, Wood and Wiring
Mice have to gnaw to keep their teeth in check, and they chew into anything that might hold food or nesting material. The common finds:
- Packaging. Small ragged holes in cereal boxes, bags of rice or pasta, bread bags and pet food sacks, often with a few spilled crumbs underneath.
- Wood and plastic. Fine tooth marks on the corners of kickboards, skirting and cupboard backs, or on plastic pipes and storage boxes.
- Cables. Stripped or nicked insulation behind appliances, under floors or in the loft. Treat this one seriously, because chewed wiring can start a fire.
Smell and Grease Marks
A settled group of mice produces a stale, musty smell with a sharp edge of ammonia from their urine. It is strongest in enclosed spaces such as under the sink, inside the boiler cupboard or under the stairs, and it tends to build slowly, so people living with it notice it less than a visitor does.
Mice run the same routes again and again, usually hugging a wall. Over time the natural grease and dirt on their fur leaves faint grey-brown smears along skirting, round pipe holes and at the edge of gaps they squeeze through. A smear at a gap is a strong clue that it is their way in or out.
Nests and Sightings
A mouse nest is a loose ball of shredded material: paper, cardboard, fabric, loft insulation, even tissue pulled from a bin. Nests are tucked somewhere warm and undisturbed, such as behind a kitchen unit, inside a sofa base, in a box in the loft or under the bath panel. Finding one, especially with young mice in it, means they are breeding in the house.
Seeing a mouse is the sign people remember, but it is often the last to arrive. Mice are mostly active at night and keep out of open rooms, so one crossing the kitchen floor in daylight usually means there are enough of them that they are being pushed into the open.
One sign is a clue; two or three together is an answer. Fresh droppings plus gnawed packaging in the same cupboard tells you far more than a single noise or one old dropping behind the cooker.
Noises, and Whether It Could Be Rats
Scratching and scurrying in the ceiling or walls at night is another common sign, and it has its own page: noises in the walls and ceilings. If what you are finding looks too big for a mouse, the mice or rats page helps you tell the two apart.