How to tell if you have mice

What mouse droppings look like

Mouse droppings are small, about 3 to 6 mm, dark and rice-grain shaped with pointed ends. A mouse leaves between 40 and 100 a day, scattered rather than gathered in piles. You will find them in drawers and cupboards, along skirting boards, behind appliances and in the loft.

Fresh droppings are dark and slightly soft. Older ones turn dry and grey. If you find dozens in one drawer, the mice have been using it for some time. Wear gloves and wash your hands after clearing them, and note the date so you can see whether new droppings appear.

Other signs of mice

Look and listen for:

• scratching or scampering in walls, floors and the loft at night
• an ammonia-like smell, strongest in enclosed spaces
• gnawed cables, packaging and food containers
• small nests of shredded paper, fabric or insulation

Mice get through gaps of about 6 mm, so a mouse can enter a home through gaps that look too small for anything. Check around pipes, under doors and along air bricks. Mark each gap you find with a pencil or tape so you can fill it later, and note where droppings are thickest, because that is where the mice run.

Mouse or rat?

The size settles it. Rat droppings are about 9 to 14 mm and chunky, against 3 to 6 mm for mice. Rats also gnaw larger holes and leave greasy smear marks along their runs. Read how to identify rats if your droppings are bigger.

Heavy thumping in a loft is more likely to be rats or squirrels than mice, and squirrels are noisy by day. If you are unsure, our rat guide and a few nights of observation will settle it.

Other droppings that look similar

Cockroach droppings are coarse specks like ground pepper, not pointed grains. Bat droppings crumble to powder when you press them, whereas mouse droppings stay firm for a while. If the droppings are in a loft near the eaves, treat bats with care: they are protected, and you should not disturb them.

Bites alone do not identify a pest. If you cannot find droppings, gnawing or nests, set a camera or a trap and wait a few nights before you decide.

When mice are most active

Mice move indoors in autumn and winter as it turns cold, but a female has five to ten litters of four to twelve a year and breeds at about six weeks, so a home can have mice in any month, including summer. Once you have identified them, read about mouse control by a professional, the legal DIY methods, or what it costs.