§ 01
Droppings
This is the most reliable way to tell. House mouse droppings are small, dark and about 3–6 mm long with pointed ends, a bit like grains of rice, and are often scattered widely in cupboards and along skirting boards. Brown rat droppings are about 1–2 cm long, thicker and usually found in groups.
§ 02
Noise and movement
Mice make light, quick scratching and pattering sounds, often in kitchen walls, under floors or behind kitchen units. Rats are heavier and the noise tends to be louder, with thumping, gnawing and dragging sounds, usually in lofts, under floors or around the outside of the property.
§ 03
Where you find them
Mice usually live inside the building, close to a food source, and will nest behind appliances, under kitchen plinths and in wall cavities. Rats more often live outside or in drains and come in to feed or shelter, so signs around sheds, decking, compost bins and drain covers point towards rats.
§ 04
Size of the gap they use
A mouse can get through a gap about the width of a pencil (around 6 mm). A rat needs a gap roughly the width of a thumb. Check around pipes under the sink, behind the cooker, where cables come through walls and around the boiler.
§ 05
Why it matters
Mice and rats behave differently, so bait stations, traps and proofing need to go in different places. Rats in particular are often linked to a drainage fault that needs finding. Getting the identification right first saves time and stops the problem returning.
