Skip to main content
link to buildings & schools
->Home > publications > beasts

BEASTS BEGONE! Appendix A: Animal Identification

House Mouse house mouse eating crackers

Small (less than 1 oz.) slender grayish brown rodent with a largely hairless tail. Largely (but not exclusively) nocturnal. Frequent invader of basements, wall void, attics, crawl spaces, and human living spaces of buildings. Particularly common in urban areas.

Access Routes

Physical cover near the foundation can facilitate access; check firewood stacks, debris piles, and crawl spaces under decks or additions.

Entry Sites

Holes larger than 1/4 inch, usually in vicinity of foundation.


Squeaking. Scampering; gnawing.

Gnaw Marks and Food Remains

Gnaw marks on wood, plastic, etc.

Fecal Droppings: house mouse droppings

Dark, elongated, hard; about 1/8 to 1/4 inch long. Most frequent in areas of most mouse activity.




White to gray; 1/8 to 1/4 inch long.

Other Signs

Urinary "pillars" (small mounds of grease, urine, and dirt). Body rub marks around entry sites and along runways. Runways in insulation. Nests (generally loosely woven balls of shredded fibrous material). Urine stains (under UV light).

Tracks:    Front: 1/4 in.  Hind: 3/8 in

next page