6 Signs of a Rat or Mouse Infestation in Your Home

Rodent Droppings

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.

Gnaw Marks

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.

Foul Odor

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.

Tracks and Runways

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.

Nests

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.

Scratching Noises

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.