5 Early Warning Signs of Mice—and What to Do Next

Why mice move indoors

Colder weather can drive rodents inside in search of warmth and shelter, said Dan DiClerico, director of the Good Housekeeping Institute’s Home Improvement & Outdoor Lab. He calls this seasonal movement the “fall invasion.” A single mouse may become a full infestation in a few months, making a quick response worthwhile. Mice are active at night, so seeing one during daylight is a reason to take a closer look, Heinsohn said.

Look for droppings and nests

DiClerico identifies mouse droppings as the strongest indication of mouse activity. A larger number in one area may point to a larger infestation. Droppings can be difficult to distinguish from those left by cockroaches or crickets, Heinsohn said. She noted that those insects’ droppings have square ends, rather than pointed ones.

Inspect warm, dark locations where mice may nest, including corners, radiator openings, wall voids and attics. Areas near water heaters, dryers, stoves and dishwashers are also worth checking.

Make the home less inviting

Reduce accessible food by wiping counters and sweeping floors daily, DiClerico advised. Heinsohn recommends putting pantry staples in hard-plastic or glass containers with tight-fitting lids. Mice can climb vines, shrubs and tree branches to reach a home, so Heinsohn recommends limiting plantings close to the house. Pea-sized gravel laid 3 inches deep and 3 feet out from the foundation can also make the area harder for mice to cross.