Mice often leave evidence before you see one: droppings, gnaw marks, nighttime sounds, and nesting material. A combination of fresh clues is more useful than any single sign.
Look for droppings and gnaw marks in sheltered areas
Check behind appliances, inside lower cabinets and pantries, and along walls. Fresh droppings tend to look darker, and new gnaw marks expose lighter material.
Listen and watch at night
Scratching in walls or ceilings, movement along baseboards, and food packages chewed overnight strengthen the case. Not every nighttime noise is a mouse, so look for physical evidence too.
Do not aggressively sweep dry droppings
Avoid kicking contaminated dust into the air. Ventilate when appropriate, wear gloves, and follow local public-health guidance for dampening and removing rodent waste safely.
After confirming activity, look for entry points
Gaps around pipes, garage doors, vents, and exterior joints can provide entry. Sealing access and removing available food are part of control, not just setting traps.