House Mouse



What are House Mice?

The house mouse is the most commonly encountered and economically important of the commensal rodents. House mice are of Central Asian origin, but they are distributed worldwide and can be found throughout the United States. House mice are not only a nuisance, but they can pose significant health and property threats.  


House mice breed rapidly and can adapt quickly to changing conditions. In fact, a female house mouse can give birth to a half dozen babies every three weeks and can produce up to 35 young per year.


Pest Stats

Color

Dusty gray with a cream belly

Legs

4

Shape

Round

Size

2 1/2 - 3 3/4" long

Antennae

No

Region

Found throughout U.S.


What Do House Mice Look Like?

House mice are typically dusty gray with cream-colored bellies. Fur color varies from light brown to dark gray depending on the mouse’s location. House mice have four legs and a round shaped body. Their muzzles are pointed, and their ears are large with some hair. House mice range from 2.5 to 3.75 inches long. Their tails are usually 2.75 to 4 inches long.


What Do House Mice Eat?

In nature, mice prefer to eat cereal and seeds, but they will also eat insects, nuts and fruits. Inside structures, mice will consume almost any human food, but prefer grain based products. 


Signs of an Infestation

There are a handful of ways to tell if house mice have made your home their own, including the following telltale signs of an infestation:


1. Gnaw marks: Gnaw marks may be either rough or smooth. 

2. Droppings: House mouse droppings may be either soft and moist or dried and hard. The droppings measure about 1/8-1/4 inch long. They are rod shaped and pointed on the ends. 

3. Tracks: House mice leave 4-toed prints with their front feet and 5-toed prints with their hind feet. 

4. Rub marks: House mice often leave oily rub marks on walls along which they travel. 

5. Burrows: House mice burrow using nesting materials such as insulation. 

6. Runways: House mice usually use the same pathways. Active runways are sometimes visible, with rub marks, droppings, and footprints along them. 

7. Odor: The odor of house mouse urine may become distinct if there is a large number of house mice in a particular area. House mice use their strong-smelling urine to communicate with one another. 

8. Damaged goods: Mice prefer seeds or cereals but will readily eat insects trapped on glue boards. 

9. Actual rodent: If you see a mouse scurrying across the kitchen floor, there is likely a family of mice hiding out of sight.

House Mouse

House Mouse

Roof Rat

What are Roof Rats?

The roof rat is the smaller of the two commensal rats, as the Norway rat is larger in size. Roof rats are also referred to as black rats or ship rats. The roof rat gets its name from its tendency to find shelter in the upper parts of buildings. Once inside, roof rats not only damage materials by gnawing through them, but they also contaminate stored food and serve as vectors of dangerous diseases.


Roof rats are thought to be of Southeast Asian origin, but they are now found worldwide, especially in the tropical regions. Roof rats are common in coastal states, seaports and the southern third of the country.


Pest Stats

Color

Brown with black intermixed; Gray, white or black underside

Legs

4

Shape

Long and thin with scaly tail; large ears and eyes

Size

16" total (6-8" body plus 6-8" tail)

Antennae

No

Region

Coastal states and the southern third of the U.S.


What Do Roof Rats Look Like?

Roof rats are long and thin rodents that have large eyes and ears, a pointed nose and a scaly tail. Roof rats have soft and smooth fur that is typically brown with intermixed spots of black. Their undersides are often white, gray or black.


Adult roof rats measure 6-8” (16-20 cm) when combining their head and body length. Their tails are notably longer than their heads and bodies, measuring 7-10” (19-25 cm). This means that roof rats can measure more than 40 cm long. They usually weigh 5-9 ounces (150-250 g), but can grow up to 12 ounces (340 g).


Signs of an Infestation

There are many key indicators of a roof rat infestation in the home. First and foremost, seeing an actual rodent, dead or alive, is a telltale sign of a potential roof rat problem. Another common sign of a roof rat infestation is the presence of droppings around the home. Fresh roof rat droppings are soft and moist, whereas old droppings are hard and dried. The droppings usually measure about ½” (12-13 mm) and have pointed ends. Droppings from Norway rats are larger – measuring about ¾” (18-20 mm) with blunt ends. The discovery of gnaw marks, damaged goods, nests or greasy rub marks also indicates roof rat activity. Other common signs of an infestation are noises in the attic or house walls and damaged electrical wires.

Roof Rat

Roof Rat

Norway Rat

What Are Norway Rats?

The Norway rat commonly referred to as the street or sewer rat, is believed to be of Asian origin, arriving in the U.S. on ships from other countries in the 1700s. Today, Norway rats are found throughout the world. Norway rats have fairly poor vision and are colorblind. Despite this, their other senses, including hearing, smell, touch and taste are keen. Although not extremely agile, they are capable of running, climbing, jumping and swimming. Norway rats are known to cause damage to properties and structures through their gnawing. Read more to learn about Norway rats, including Norway rat control. 


Pest Stats

Color

Brown with scattered black hairs; gray to white underside

Legs

4

Shape

Long, heavily bodied; blunt muzzle

Size

7-9 ½ inches long

Antennae

No

Region

Found throughout U.S.


What Do Norway Rats Look Like? 

Norway rats have bristly brown fur, with black hairs dispersed throughout their coat. Their underside tends to be lighter, with gray to off-white coloring and even yellow tones. Norway rats have small eyes and ears, and their tails are shorter than the length of their head and body coupled together.  


Signs of a Norway Rat Infestation 

There are several telltale signs that a home has a Norway rat infestation. Gnaw marks throughout the house are one clue of the presence of Norway rats. New bite marks or holes tend to be rough, whereas older ones are smooth from wear and are also often greasy. Spotting droppings, which are capsule-shaped, is another key indicator of a Norway rat problem. Norway rats’ droppings have blunt ends, while those of roof rats have pointed ends. Other signs include footprints, greasy and dark rub marks from oily fur against pathways, burrows, runways with stacked food, and damaged or rummaged-through food products.

Norway Rat

Norway Rat