Record the clue before interpreting it
Log exact start time, duration, wall or ceiling position and weather for several days before opening a cavity.
A useful record includes scale, shape, texture, placement and whether the material returns after a clean baseline is established. Avoid changing the scene merely to make identification easier.
What to note
- Day versus night
- Upper versus lower route
- Scratching, rolling, chirping or fluttering
- Repeated entry point
Do not open a cavity with unknown wiring, wildlife or contamination. Avoid sealing dependent young inside.
Read the full safety guideCommon candidates
These candidates are not ranked until location, scale, pattern, context and timing are added. Open a profile to see confirming and contradicting evidence.
House mouse
Mus musculus
Small smooth tapered droppings along edges, fine gnawing and shredded nesting material near food routes.
Norway rat
Rattus norvegicus
Large thick droppings, broad gnawing and lower-level routes near foundations, drains or burrows.
Roof rat
Rattus rattus
Slender rat-scale droppings and nighttime movement in attics, rafters or elevated routes.
Eastern gray squirrel
Sciurus carolinensis
Daytime bounding and rolling sounds near a larger roof opening, with leaves or bulky nesting material.
Big brown bat
Eptesicus fuscus
Crumbly droppings with shiny insect fragments below a high roost or entry, sometimes with fluttering at dusk.
House cricket
Acheta domesticus
Repeated nighttime chirping from a warm void, with a tan long-legged jumping insect nearby.
Comparisons that resolve common confusion
Side-by-side decision
Mouse vs. cockroach droppings
Size and surface are the fastest split: mouse droppings are distinct rice-like pieces; German-cockroach evidence is usually pepper-like spotting or tiny ridged material.
Open comparison
Side-by-side decision
Mouse vs. rat droppings
Overall length, thickness and associated damage matter more than color. Rat evidence is substantially larger and heavier.
Open comparison
Side-by-side decision
Norway rat vs. roof rat signs
Vertical location is the strongest household clue: Norway rats favor ground and lower levels; roof rats concentrate signs above.
Open comparison
Side-by-side decision
Bat guano vs. mouse droppings
Bat guano accumulates below a roost and crumbles into insect fragments; mouse droppings are denser and follow wall routes.
Open comparison
Side-by-side decision
Squirrel vs. rat attic sounds
Time of activity is the best first split: squirrels are mainly daytime; roof rats are mainly nighttime.
Open comparison
Side-by-side decision
House cricket vs. mouse sounds at night
A repeating tonal chirp points toward a cricket; irregular scratching, running or gnawing along an edge points toward a mouse route.
Open comparison