The short answer
Block every gap bigger than a pencil with wire wool and filler, remove all accessible food, and use snap traps baited with chocolate spread rather than cheese.
- Find the gaps. A mouse gets through anything it can fit its skull into, which is about the width of a pencil. Check under kitchen units, around pipe entries, airbricks and where the floor meets the wall.
- Stuff wire wool into each gap and seal over it. Mice will chew through filler and expanding foam alone but not through steel wool.
- Remove the food. Everything in the cupboard into sealed containers, pet food picked up overnight, bird feeders moved away from the house.
- Set snap traps against the wall, at right angles, where you have seen droppings. Mice run along edges rather than across open floor.
- Bait with chocolate spread or peanut butter, which they cannot pick up and carry away.
What will ruin it
Poison kills the mouse somewhere you cannot reach, which means a smell for weeks, and it is a real risk to pets, children and any bird of prey that eats the carcass.
Why it works
Mice are neophobic about open spaces but not about new objects near a wall. Trap placement matters far more than the bait.
Household chemicals can be dangerous in combination. Never mix them, keep the room ventilated, and test anything on a hidden patch first. Full disclaimer.
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