How to know it is this one
Small — 7 to 10cm body — grey-brown above and paler underneath, with large ears relative to the head and a thin tail roughly as long as the body. A young rat is sometimes mistaken for a mouse, but a young rat has noticeably larger feet and a thicker tail for its size.
The droppings tell you
Mouse droppings are 3 to 6mm, dark and rice-grain shaped, and there are many of them — a single mouse produces dozens a day. Rat droppings are far larger and fewer. If you are finding scattered small dark grains along the back of a cupboard or under a sink, that is a mouse.
Where they get in
Through gaps of about 6mm — the width of a pencil. Around pipework under sinks, beneath doors where the sweep has worn, at the joint between a kitchen unit and the wall, through vents, and around air conditioning penetrations. In apartments they also move between units through shared service voids.
The other signs
- Gnawing on packaging, especially dry goods stored at floor level
- Shredded paper, fabric or insulation gathered into a nest in a quiet void
- A faint ammonia smell in an enclosed cupboard
- Faint scratching in a wall cavity at night
What works
Trapping plus proofing. Mice are curious and investigate new objects readily, which makes trapping effective where it is well-placed — along walls and runs rather than in open floor. But as with rats, an unproofed property simply keeps receiving new arrivals, so sealing the gaps is what ends the problem rather than managing it.
In homes with young children or pets we will generally recommend trapping over bait, and explain the trade-off rather than deciding for you.