Evict and Exile Mice from Your Home

return to Contents

Step one: inspect your home

Management strategies differ slightly for mice and rats. Thorough monitoring will help you identify the species and find their hiding places and entrances.

Signs of rodent activity:

Droppings and urine stains. The droppings of a house mouse have pointed ends and are about 1/8 - 1/4" long. (A Norway rat’s fecal pellets are about 1/2 – 3/4" long, with blunt ends). Urine stains on the woodwork and a musky odor may be noticeable.

Search cabinets, drawers, counters, corners, under sinks, and near food. Disinfect, then wipe up the droppings (see safety tips below). Check frequently for fresh droppings to determine when all the mice have been eliminated.

Gnaw marks and shavings. Mice gnaw frequently to help trim their constantly growing teeth. Look for tooth marks on baseboards, doors, window and door casings, packaged goods, cabinets, and around pipes, and for piles of wood chips or shavings.

Burrow holes. Entrance holes to their burrows are typically one inch in diameter. But mice fit through dime-sized spaces that are only 1/2" high! Look in baseboards, corners, walls, entryways, and foundations.

Runways, tracks, and "rub marks" (smudges). Mice have poor eyesight, so they tend to hug the walls during travel. They memorize routes between food and nest and rarely stray; this helps them run rapidly along a path, even in the dark. In time, a faint, dark "trail" of body oil and dirt may become visible on woodwork. In dirt or insulation, you may see a smooth, worn path. Shine a strong flashlight at a low angle across a dusty area to look for footprints.

Noise. You may hear scuttling, squeaking, or gnawing inside the walls, especially at night. Other animals make similar noises, so this is not a definitive sign of rodent infestation. House pets may be disturbed by sounds of rodent activity that you cannot hear.

Nesting and hiding places.

Inside: Mice nest in any undisturbed location, often in wall cavities, attics, garages, and basements. Their nests are made of shredded fibrous materials such as cloth or paper, and are approximately 5" in diameter. Deer mice and white-footed mice line their nests with fur, feathers, shredded cloth, or other fine material.

Droppings, seeds, and pet food will often be located near the nest.

If they can find a quiet spot in the kitchen, mice will often nest close to food. Check in and under cabinets, sinks, and appliances, behind and under refrigerators, stoves, and dishwashers, and wherever pipes or wires penetrate wall openings. Inspect stored clothes or bedding.

Outside: Thick vegetation (weeds, bushes, vines), debris (garbage, leaves), clutter (bricks, lawn furniture, discarded appliances), and piles of wood or rocks are favored by mice.

Know the beast

	Adult House Mouse: notice the smooth tail, small feet, pointed nose, large ears, and large eyes.
	Young Norway Rat: notice the scaly tail, large feet, blunt nose, small ears, and small eyes.

First, determine if you’ve got a mouse or Norway rat. They can be confused because a young rat may not be much larger than an adult mouse. In addition to the traits illustrated, mice have fine fur; rats have coarse fur.

The slender house mouse usually weighs less than an ounce. Its body is 2-3½" long; its tail, which is generally a bit longer than its body, adds another 3-4". (Norway rats are robust, weighing about a pound. Their bodies are 7-10" long; their tails are often a bit shorter than their bodies, measuring 6-8").

It’s hard to tell the species of mice apart by their signs; the easiest way to distinguish them is to capture one. A house mouse has grayish brown fur and a nearly naked tail. Both wild mice species (Peromyscus spp.) are two-toned, with grayish brown backs and white bellies; their feet and the undersides of their noticeably furry tails are also white.

Mice are primarily nocturnal, feeding mostly at dusk and dawn. They get all the water they need from their food but will drink water when it’s available. They’ll eat many foods, but prefer seeds and cereal grains. Mice tend to nibble on the edges of grain, leaving behind the core (rats often leave half-eaten pieces of grain).

If there’s ample food, their foraging range may be only a few feet, but on average, a mouse ranges 10-30 feet from its nest. Mice explore their territories daily, inspecting new objects, such as traps. Because they remain close to their nests, place traps in these ritualistic routes to increase the chance of capture.

Remarkably athletic, mice can jump about a foot high, climb up the sides of buildings, and, like a tightrope walker, cross cables and wires. They also swim. Consider these habits and abilities as you look for their pathways.

About This Site

These pages are maintained by the New York State IPM Program, part of Cornell Cooperative Extension. All material is protected by Section 107 of the 1976 copyright law. Copyright is held by Cornell University and the New York State IPM Program.