Most mouse problems start quietly.
You might not see a mouse at all. Instead, you notice small droppings, a strong urine smell, damage to food packets, scratching at night, or signs of nesting in warm hidden spots. BPCA lists mouse droppings, ammonia-like odour, smear marks, nests, damage to stored food, and gnaw marks as the main tell-tale signs. It also says house mice often nest in roof spaces, under floors, wall cavities, sheds, basements, and storage boxes.
Common signs of mice in the house include:
BPCA’s mouse guidance and BPCA-hosted 2026 rodent advice both point to these same early indicators, including droppings, scratching noises, shredded nesting material, and stronger odour near active mouse activity.
Mouse droppings are usually smaller than rat droppings.
BPCA says mouse droppings are often black and about the size and shape of a grain of rice, and that each mouse can leave around 80 droppings per day. It also notes common places to find them include under the kitchen sink, around boilers, and in roof spaces.
That is why repeated tiny droppings in cupboards or along hidden edges are often one of the first real signs.
People sometimes notice mice by smell before anything else.
BPCA says a strong ammonia smell is a common sign because mice urinate frequently. BPCA-hosted 2026 guidance also says the stronger the ammonia-like odour, the closer you are likely to be to active rodent activity.
So if one cupboard, void, or corner suddenly smells wrong, that is worth paying attention to.
Mice like somewhere warm, sheltered, and close to food.
BPCA says indoor nests may be found in lofts, under floorboards, airing cupboards, wall cavities, basements, and storage areas, and that mice build nests from materials like cloth, wool, and paper.
If you find shredded paper, insulation, or soft materials bundled into a tucked-away space, that is not a detail to ignore.
Mice are nocturnal, so sound is often part of the picture.
BPCA says mice are nocturnal and can often be heard running about at night as they search for food.
The sound is usually lighter and quicker than people imagine, which is one reason it gets dismissed at first.
Mice do not stay neatly in one area.
BPCA lists damage to stored food in cupboards and pantries, along with gnaw marks on wood, carpets, paper, pipe cables, and furniture, as common signs of mouse activity.
So if food packaging is being nibbled or soft materials are being torn up, the problem may be more established than it first looks.
This is one reason mice catch people out.
BPCA says mice can squeeze through cracks as small as 5 mm when searching for food and shelter.
That means a property does not need a dramatic hole in the wall to have a mouse problem. Very small access points can be enough.
If you are seeing small droppings, smelling ammonia, hearing movement at night, or finding chewed packaging and nesting material, the pattern is usually more important than any one sign on its own.
Mice are a year-round issue and BPCA notes they do not hibernate, with colder weather often driving more movement indoors.
If the signs keep showing up, Pest Gone can help you work out whether you are dealing with active mouse activity and what the next sensible step should be.
