Evidence and signs

Start from something you can see, hear, smell or measure: droppings, sounds, gnaw marks, nesting material, odours. Each guide ends with a decision, not a description.

Mouse droppings vs rat droppings

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House mouse droppings scattered along a baseboard on the edge of a carpet

Size is the fastest way to tell which animal you have, and it changes what you do next. Compare the two at actual size against a ruler calibrated to your screen, then work out whether this is a weekend job or a phone call.