Reviewed by William "Willy" Vizcarrondo, NYS Certified Pesticide Applicator (C1825832). Updated September 23, 2026.
The house mouse is the small gray rodent that moves into Long Island homes every fall. It weighs about half an ounce, fits through a gap the width of a pencil, and breeds fast enough that two mice in October can be a colony by January.
| Size | 5 to 7 inches long including a 3 to 4 inch tail, about half an ounce |
|---|---|
| Color | Gray to light brown, lighter belly |
| Look-alikes | Deer mouse and white-footed mouse (two-toned, white belly, come in from wooded lots), juvenile rats (bigger feet and head) |
| Where you'll find it | Kitchens, behind appliances, basements, garages, attics, wall voids |
| Active on Long Island | Year round indoors; move inside October through December |
| Danger level | Contaminates food, chews wiring, spreads bacteria |
Mice move indoors on Long Island once nights drop into the 40s, usually the first half of October, and calls peak in November.
A house mouse is small, gray, with a tail about as long as its body and small feet. Droppings are about the size of a grain of rice, dark, with pointed ends, and you'll find them along walls, in cabinets, and under the sink.
Deer mice and white-footed mice, common on the North Shore and near wooded areas, are two-toned with a white belly and feet and tend to nest in attics and garages. Rats are much larger, with heavy feet and a thick tail.
Mice contaminate every surface they cross with urine and droppings, and they chew through wiring, insulation, and stored belongings. A female can have 5 to 10 litters a year of 5 or 6 pups each, and the young can breed at 5 to 6 weeks old, which is why a small problem in October is a serious one by winter (UC IPM).
Sometimes, if it's one or two mice and you find the entry point. Snap traps placed along walls, no more than about 10 feet apart, with a small dab of peanut butter on the trigger, work better than anything sold as a repellent.
What most homeowners miss is the sealing. Mice fit through a 1/4 inch gap, and plastic, foam, rubber, and wood all get chewed through. Gaps need steel wool with caulk or metal (CDC, UC IPM). If you're still catching mice after two weeks, or you hear them in the walls, the entry points haven't been found.
We inspect inside and out, trap the active runs, seal every entry point we find with steel mesh, and come back to check. Mouse treatment carries a 60-day written guarantee.
More on mouse extermination on Long Island.
Related answers
Usually more than one. Mice rarely travel more than 30 feet from the nest, so a mouse in the kitchen means a nest close by, and by the time one is out in daylight the population is large enough that they're competing for food.
October through December, as soon as overnight temperatures drop into the 40s. They stay through winter and many never leave.
No. A house gives them food, warmth, and shelter, and they breed year round indoors. The population grows until something stops it.
About 1/4 inch, the width of a pencil. Check where pipes, cables, and gas lines enter the house, the garage door seal, and gaps at the foundation.
Think you have house mice? Call (516) 509-6001 for a free written quote.