Pest droppings are the most reliable indicator of what's living in your home. They're present even when the pest isn't visible, they accumulate in predictable locations, and their size, shape, and placement narrow identification to just a few species. This guide covers the most common dropping types homeowners encounter.
Size: 3–6mm long (rice grain size). Shape: Pointed at both ends, dark brown to black. Quantity: 50–75 droppings per day per mouse — you'll find many in concentrated areas. Location: Along walls, behind appliances, under sinks, in drawers, inside cabinets. Fresh vs old: Fresh droppings are dark, moist, and shiny. Old droppings are gray, dry, and crumbly. Our mouse vs rat droppings guide has detailed comparisons.
Size: 12–20mm (olive pit size — 3–4x larger than mouse droppings). Shape: Norway rat droppings are blunt and capsule-shaped. Roof rat droppings are thinner with pointed ends. Quantity: 20–50 per day per rat, concentrated along runways. Location: Norway rats: basement, ground level, near walls. Roof rats: attic, upper levels, near rooflines.
German cockroach: Tiny dark specks resembling coffee grounds or black pepper. Found concentrated in cabinet hinges, behind outlet covers, under sink, and behind appliances. In heavy infestations, droppings form dark smears or staining. Large cockroach (American, Oriental): Cylindrical, blunt-ended, about 2mm long with ridges. Found along baseboards in basements and near floor drains.
Size: Similar to mouse droppings but distinguished by texture — bat guano crumbles into a shiny powder when pressed (from insect exoskeletons). Mouse droppings are hard and compress without crumbling. Location: Concentrated below entry/exit points — often on attic floors, windowsills, or exterior walls beneath roofline gaps. If you find droppings that look like mouse droppings in the attic near a vent opening, they're almost certainly bat guano.
Not technically droppings — carpenter ant frass is excavated wood and body parts pushed out of galleries. It looks like fine sawdust mixed with insect body fragments, accumulating in small piles below the nest opening in wood. The presence of carpenter ant frass on a windowsill, baseboard, or shelf means a colony is actively excavating wood nearby.
Drywood termite fecal pellets are hexagonal, hard, and uniform — about 1mm long, resembling coarse sand or poppy seeds. They accumulate below "kick holes" where termites push frass out of the wood. The pellets are distinctive enough for conclusive identification. Subterranean termites incorporate their frass into mud tubes and don't leave visible pellet piles.
Bed bug droppings aren't pellets — they're liquid fecal spots that look like tiny dots of black ink on mattress seams, sheets, and headboards. They bleed into fabric like a marker dot. On hard surfaces, they appear as small dark spots. This is often the first evidence found before live bugs are seen.