6 Signs of a Rat or Mouse Infestation in Your Home

Signs of a Rat or Mouse Infestation in Your Home

The Spruce

Even after you've worked to eliminate the problem of a mouse or rat infestation, you'll want to know that they're completely gone. Rodents can be tricky, often only coming out at night. So here are six ways to tell whether there are still any mice or rats in your home.

Determining Rodent Infestation Size

Certain signs can indicate the size of a population. If rodents are seen at night but never during the day, the population has probably not become large and can be controlled with traps and bait. If you are seeing any rodents during the day, numerous fresh droppings, or new gnaw marks, it is likely that the population has become quite large and might require professional pest control services.

  • 01 of 06

    You See Rodent Droppings

    mouse droppings

    The Spruce / Adrienne Legault

    Fresh droppings are dark and moist. As rat and mouse droppings age, they dry out and become old and gray, and they easily crumble if moved. Droppings are most likely to be found near food packages, in drawers or cupboards, under sinks, in hidden areas, and along walls. You will find the highest number of droppings where the rodents are nesting or feeding, so inspect the area around the new-found droppings to determine whether there is still an active (or new) infestation.

  • 02 of 06

    You See Gnaw Marks

    gnaw marks in drywall

    The Spruce / Adrienne Legault

    In contrast to the droppings, new rodent gnaw marks are lighter in color and become darker as they age. You might see the gnawed holes on food packaging or on the walls. One way to determine age is to compare a gnaw mark you just noticed with those on a similar material that you know to be older. If the newly found marks are lighter in color, it could be an indication of a continuing infestation. The marks can also indicate whether you have rats or mice; larger gnaw marks will have been produced by the larger teeth of rats. If you had a mouse infestation but you are now seeing larger gnaw marks, you might now have rats.

  • 03 of 06

    There Is a Foul Odor

    cat smelling under stove

    The Spruce / Adrienne Legault

    Cats and dogs (or even a pet rat or mouse) might become active and excited in areas where rodents are present. This is a result of the odor of the rodents' urine and is most likely to occur when rodents have recently entered a structure. If you see your pet pawing at an area in which it had previously had no interest, get a flashlight and examine the area for rats or mice. If an infestation is large, you might also detect an ongoing stale ammonia smell coming from hidden areas, indicating an active infestation. This differs from the odor of a dead mouse that could be stuck in the wall or in a hidden area; that smell is an unforgettable sharp, pungent yet sour odor that permeates the area.

  • 04 of 06

    There Are Tracks and Runways

    sprinkling baby powder to identify rodent pathways

    The Spruce / Adrienne Legault

    If rodents are currently active in or around your home, their runways and tracks are likely to be distinctive, becoming fainter as time passes. Tracks or runways are most easily detected with a flashlight or blacklight held at an angle toward the suspected area. You might see smudge marks, footprints, urine stains, or droppings.

    If you suspect an area is being frequented by rodents, try placing a very thin layer of flour or baby powder there. If rodents are active, you are likely to see their trails in the powder.

    Continue to 5 of 6 below.
  • 05 of 06

    You Find Nests

    rodent nest

    The Spruce / Adrienne Legault

    Rodents will use materials such as shredded paper, fabric, or dried plant matter to make their nests. If these areas are found and have any of the other signs of current presence (fresh droppings, gnawing, odor, or tracks), it is likely that there is still an infestation in your home.

  • 06 of 06

    You Hear Scratching Noises

    mouse scurrying

    The Spruce / Adrienne Legault

    If things are going bump in the night, that could be an indication that mice or rats are still active in your home. You might hear them scurrying along beneath the floors, scampering around the cabinets, or burrowing behind walls and joists. You might even hear muffled squeaking. If you have a cat or other pet, watch to see whether they are paying attention to what might be going on behind a wall. Then, put your ear up to the wall to see whether you can hear something.

  • How do you tell the difference between a rat and mouse infestation?

    Rats have larger tooth marks and can gnaw through walls, flooring, insulation, wiring, and soft metals, such as lead and aluminum. Rat droppings are double the size of mouse droppings, usually measuring about 1/2 inch long and tapered at one end. Mouse droppings are about 1/4 inch long and thinner.

  • What attracts mice and rats to your house?

    Food, water, and shelter are the main attractions for mice and rats. Keep your house clean, and throw out the garbage, including food and pet waste, and any paper.

  • What scents repel mice and rats?

    These rodents have a strong sense of smell. They dislike the smell of garlic, onion, hot peppers or chili powder, cleaning ammonia, bleach, mothballs, white vinegar, used coffee grounds, peppermint oil, eucalyptus, predator scent (cats, raccoons), and citronella oil.

  • Where do mice and rats go during the day?

    Mice and rats are nocturnal. During the day, they sleep hidden in their nests, squirreled away with nesting materials made of shredded paper, cardboard, insulation, or pieces of fabric. They often hide in walls, under appliances, and at the base of cabinets.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Control of Mice. University of Kentucky Cooperative Extension Service.

  2. How Do I Manage Mice and Rats? New York State Integrated Pest Management.