Field plate · Mus musculus
House mouse
The year-round tenant of Erie walls: small, grey-brown, and inside at the first hard frost — if it ever left.
Plate 4 of 28. Drawn in profile to the identification marks named below; the scale rule is a drawing convention — sizes are given in the text.
Identification marks
About 7–10 cm of body plus a tail nearly as long, grey-brown above and paler below, with large ears and a pointed muzzle. Droppings are small rods, 3–6 mm, pointed at the ends.
Look-alikes it is confused with
Deer mice (clean white belly, large eyes, two-tone tail — more typical at the rural edge and in sheds), young rats (far larger feet and head, blunt droppings), and voles (outdoors, short tails, rarely in walls).
Where it hides in a house
Wall voids, behind the stove and refrigerator, in basement ceilings, stored boxes, and any quiet corner within a few meters of food. In Erie's pre-war housing, pipe chases and balloon framing give mice a highway between floors.
Health & property risk, stated plainly
Real. Mice gnaw wiring and insulation, spoil stored food with urine and droppings, and can carry leptospirosis and other contamination into kitchens. Treat droppings in enclosed spaces as a cleaning hazard: ventilate, wet down, and do not dry-sweep. The infection most specifically tied to house mice is LCMV (lymphocytic choriomeningitis virus), carried in urine and droppings — one more reason for the wet-clean rule, and for keeping food sealed. The hantavirus concern in Pennsylvania attaches to deer mice in sheds, cabins, and outbuildings, not to house mice; the same clean-up rules cover both, which is why the desk gives one protocol rather than two.
What actually works
Exclusion is the control: seal every gap of 6 mm or more with copper mesh and sealant, fit door sweeps, and screen vents. Snap traps along walls where droppings appear, baited and checked daily. Remove bird seed, pet food, and cardboard harborage in the basement.
What doesn't
Poison alone inside the walls — mice die where you cannot reach them, bait does not close the hole the next mouse uses, and poisoned mice are a genuine risk to pets and wildlife. Ultrasonic plug-ins have no reliable effect.
When to call a licensed pro
Call a pro when you hear activity in several rooms, when droppings appear after two weeks of trapping, when the entry points are in a roofline or chimney chase, or when the building is a rental or food premises.