Identifying a Mouse or Rat Problem in Your House

How to Tell if You Have Mice or Rats

You know or suspect there are rodents in the house, but how can you tell if you’re dealing with mice or rats? Even though they share common signs, use their unique indicators to find out what kind of rodents are present. This is also important so you know the right bait or trap to use to get rid of them.
 
Appearance. Rats are larger than mice and will have coarse red, brown, grey, or black fur (depending on the variety) and a long, scaly, fur-less tail. A mature rat can range from 11-19 inches long (including its tail) and weigh ½ to 1 pound. 
 
Mice have large ears and tiny black eyes. They have fine fur that can be black, grey, or brown and a 3-4 inch long, hairless tail. Mature mice grow to about 6-7 inches long (including its tail) and weigh ½ to 1oz.
 
Droppings. Rodent droppings are a sure sign that rats or mice are present, and will indicate the type of rodent, the size of the infestation, and where they are most active.

• Mouse droppings are small, less than ¼ inch, and pointed on both ends.

• Rat droppings are ½ inch or larger. 

• Norway Rat droppings are blunt at both ends, while Roof Rat droppings have pointed ends.

New droppings are shiny and putty-like in texture, while old ones are hard and crumbly. Varying feces sizes indicate that juveniles and adults are present, and lots of droppings may be an indication of a large infestation. The location of the droppings indicates active areas where you should place bait or traps.
 
Urine Odor. Rodent urine has a strong musky odor. With large infestations, you can easily smell it.
 
Gnawed Holes. Gnawed mouse holes are small, clear-cut, and about the size of a dime. Gnawed rat holes are large, about the size of a quarter, with rough torn edges.
 
Rub and Gnaw Marks. Oily rub marks are left in places where rodents travel along walls. If rub marks smear, you know they are fresh. Gnaw marks on wood around the house also are a sign. Tooth marks about ⅛ inch long are typical of rats and small scratch marks are a sign of mice.
 
Runways. Common rodent pathways are generally along interior walls, building foundations, ledges, pipes, electrical wires, conduits, tree branches and fence rails.
 
Nests. Mice will shred paper, string, and other pliable materials to build their nests indoors. Norway rats nest outdoors in burrows deep in the ground. Roof rats typically nest above ground in attics, trees, or dense vegetation.
 
Noises. Rodents are nocturnal. At night they often create scratching sounds as they run inside walls and along floors.
 
Pet Behavior. Pets tend to act unusual when they hear or smell rodents in the house. They may appear extremely alert, bark, or begin to paw at spaces beneath refrigerators, stoves, or low-clearance pieces of furniture.
 
For more information, read Telltale Signs of a Rodent Infestation.