The most telling signs of a mouse infestation are small black droppings (mice produce 50–75 per night), scratching sounds in walls after dark, gnaw marks on food packaging, and a musky ammonia-like smell. If you've noticed any of these, you likely have more than one mouse.

Mouse Droppings

Mice produce lots of droppings, usually around 50–75 per night. These droppings are small, about the size and shape of a grain of rice — around 3–6 millimeters long, black or dark brown, and pointed at the ends. You'll often see them along walls, near food storage areas, under sinks, in cupboards, on countertops, and anywhere mice might travel. If you see fresh droppings (moist, dark), that means active infestation. Old droppings are dry and gray.

Gnaw Marks and Chewed Materials

Mice have teeth that never stop growing, so they constantly chew to keep them short. Look for gnaw marks on food packaging, boxes, wires, plastic, and even furniture or baseboards. New gnaw marks are lighter in color, meaning recent activity. Mice will get into bags of chips, cereal boxes, and other pantry items by chewing through packaging.

Scratching and Scurrying Noises

At night, when it's quiet, you may hear faint scratching, rustling, or scampering, especially coming from your walls, ceilings, or under floors. Mice are most active at night, so any odd noises may point to their presence.

Strange, Unpleasant Odor

A strong, musty, or ammonia-like smell can develop where mice are active. This odor comes from their urine, especially if mice are nesting in hidden areas. The smell is usually strongest in enclosed spaces like pantries, cupboards, and closets.

Mice Nests

Mice build nests from shredded paper, fabric, insulation, or plant material. These nests are usually hidden in quiet, sheltered places like behind appliances, inside walls, in storage boxes, or under furniture. Finding small piles of shredded material in odd spots is a sign that mice are nesting nearby.

Food Debris and Tracks

Mice leave crumbs and bits of food as they eat. You may see scattered dry food like rice, cracker pieces, or seeds in places mice frequent. You can sometimes spot tiny dirty footprints or tail marks in dusty areas, especially along their regular runways.

Grease Marks or Smudge Trails

As mice travel the same pathways along walls or baseboards, their fur leaves greasy, dark marks. These are called "rub marks" or "smudge marks." Look for dirt or oily streaks at about mouse height. This is another sign mice have been active in that area for some time.

Seeing Live or Dead Mice

Actually seeing a mouse — alive or dead — is clear evidence. Mice are shy and nocturnal, so if you spot one during the day, the infestation could be severe, with mice running out of room to hide.

Pet Behavior

If you have cats or dogs, watch their reactions. Pets often become excited or focused on specific areas, like staring at a wall, sniffing under appliances, or acting agitated at certain spots where mice might be hiding.

Unexplained Damage or Holes

Mice can gnaw holes in walls, baseboards, and floors to create entry points. Look for small, rough-edged holes — often about the size of a dime (1.5–2 centimeters) — particularly low on walls or behind furniture.

What to Do If You Notice These Signs

If you notice any of the above signs, it's very likely you have a mouse infestation. Act quickly: clean up food sources, seal openings, remove clutter, and set traps or call a pest control specialist if the problem seems big. Early action will prevent the problem from becoming much worse.

Found these signs in your NH home? Anchor Pest Services offers same-day inspections across Manchester, Nashua, Concord, and surrounding areas. Call (603) 785-0118 or contact us online.

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