Commensal (domestic) rodents live in close association with humans. These commensal rodents are nocturnal and tend to move indoors to warmer areas during late fall or early winter and return to the outdoors in late spring or early summer, or remain indoors if food and suitable harborage are available. Mice and rats are a problem when they find their way into your home. They like to be near humans so that they have a ready supply of food. This has earned them the term “commensal,” which means “to share one’s table.”


Removing rodents can sometimes be as easy as setting a mouse trap; but a larger infestation (especially with rats or larger rodents) can be larger issue. Rats, especially, are smart and can learn to avoid traps.

Rodents can carry up to thirty-five diseases that humans are susceptible to, which is another reason to eliminate them as soon as possible. Cleaning up after a rodent infestation also requires a great deal of caution. This is necessary because of the possibility of fleas or mosquitoes, which may transmit their own diseases to you, your children and pets. There is also risk involved if you inadvertently stir up the dust of their nests; it can be hazardous to breathe in the bacteria contained within.

Rodents can also do physical damage your home or business. They easily chew through some types of siding and other building materials. They are also known to chew on electrical lines, thereby increasing the possibility of fire. They damage other materials as well, creating holes and gnawing on numerous objects, especially food or food containers.

Removing rodents can be difficult. A professional pest management company will identify nesting areas and feeding grounds and know how to completely eliminate them. Proper cleanup is also performed, ensuring that you and your family are safe from allergies, illness and possible future infestation.

Commensal rodents generally have poor sense of vision, but they have acute sense of smell, touch, and taste. They tend to gnaw through any material that is softer than their enamel, and they are generally good climbers, jumpers, swimmers and burrowers. There are three species of domestic rodents:


Roof Rat

(Rattus rattus)

Alias: Black Rat/Tree Rat

Roof rat is slender and agile, and Its tail is longer than the head and body lengths combined. Its total length may reach 12 to 17 ¾ inches and can weigh up to about ¾ of a pound. Roof rat nests above ground and lives in ivy, wild blackberry vines, attics, garages, and wood piles. It will enter buildings if given the opportunity, and often use utility lines and fences as runways. It prefers to feed on fruits, nuts, ivy, and pet food commonly found in residential areas.

(Rattus norvegicus)

Alias: Sewer Rat/Wharf Rat

Norway rat is larger and more aggressive than the roof rat. It has smaller eyes and ears than the roof rat, and its tail is shorter than the combined head and body length. Its total length may reach 18 inches and may weighs up to about 1 lb. Norway rat lives and nests in underground burrow system and is generally found in agricultural areas, creeks, sewers and occasionally developed neighborhoods. It can also live in buildings, basement, creekbanks, waterfronts, under blackberry vines, under wood piles. It feeds on garbage, pet food, meat scraps, cereal grains, fruits and vegetables.

(Mus musculus)

House mouse is small, slender bodied, and the tail is longer than the length of its head and body. Its body size ranges from   2-1/2 to 3-4/5 inches long. Its body color is generally grayish brown with a gray or buff belly. House mice is agile climbers and can fit through openings as small as ¼ inches in diameter. It eats many types of food, but prefers seeds and grain. It normally travels an area averaging 10 to 30 ft. in diameters.


  • Damaged, partially eaten fruits and nuts, such as walnuts, oranges, and avocados.
  • Broken snail shells under bushes, on fences or near nesting sites.
  • Signs of gnawing on plastic wood or rubber materials.
  • Greasy rub marks caused by the rat’s oily fur coming in repeated contact with painted surfaces or wooden beams.
  • Rodent droppings are usually signs of significant rodent activity. The droppings are randomly scattered and will normally be found close to a rat runway, feeding location, or near shelter. Droppings can be found in forced air heaters, swimming pool heater covers, and water heater closets.
  • Sounds (gnawing, etc.) from attic, subfloor areas and wall spaces.
  • Visual Sightings on utility cables, tops of fences, or in trees.
  • Burrows in the ground, and adjacent to sewer lines are signs of Norway rat. activity.


  • Broken or missing foundation vent screens or attic vent screens.
  • Overlapping roof.
  • Open wooden meter boxes (in older homes).
  • Space between roof jack and vent pipe.
  • Under or on sides of garage door.
  • Brick chimneys which have settled away from house.
  • Crawl hole with poorly fitted lid.
  • Tile roof.
  • Broken or open building sewers which connect to the main sanitary sewer. (Norway rats).
  • Toilets. (Norway rats).



Roof rat survival depends upon the existence of 3 basic environmental factors: (1) Food, (2) Water, and (3) Harborage.

STEP 1: Eliminate Food and Water

  • Remove all potential sources of food from the premises, such as bird seed left out for birds. Routinely harvest ripe fruit and pick up all fruit that has fallen to the ground.
  • Store pet food in metal containers with tight sealing lids and do not leave uneaten pet food outdoors.
  • Avoid storing food in garages and storage sheds unless it is in rat-proof covered metal containers.
  • Control snails and clean up pet feces because they are favored food items.
  • Keep trash cans closed at all time with tightly fitted lids.
  • Repair leaking eliminate any other faucets, sprinklers, or other piping. Keep drain covers tightly fastened and  unnecessary standing water.

STEP 2: Destroy Rats

  • Rats should be snap trapped if they are inside a residence or building. Place traps near nesting areas or where rats are likely to hide. Do not place traps where children or pets will disturb or be harmed by them. Remember, snap traps are very DANGEROUS!
  • Poisoning with baits indoors is NOT recommended because a rat may die inside the structure and create an odor and fly problem. Poison baits may be used when following recommended guidelines.
  • Remove dead rats by placing animals in tightly sealed containers for proper disposal.
    Clean and disinfect the affected areas.

STEP 3: Eliminate Shelter & Harborage

  • Close all openings larger than ¼ inch to exclude rats and mice.
  • Repair or replace damaged vent screens.
  • Remove all trash and debris.|
  • Stack woodpiles, lumber and household items at least 18 inches above the ground, and 12 inches away from fences and walls.
  • Trim trees, bushes and vines at least 4 feet away from the roof.
  • Remove heavy vegetation away from buildings and fences.                                                 
  • Thin vegetation to allow daylight in and remove rat hiding places.

STEP 4: Maintain a Rat Free Property

  • After rats have been reduced, prevent re-infestation by keeping harborage and food sources to a minimum.


Building Maintenance

Roof rats can enter even small exterior opening of a home. Important steps a homeowner can take are inspecting and repairing:

  • Basement windows and ventilation ports.
  • Attic vents and louvers.
  • Gaps between roof and chimney.
  • Tile roofs along the eaves
  • Vent pipes and shafts.

All openings such as these should be screened with ¼ inch galvanized hardware cloth and inspected at least twice a year. Gaps around pipes and electrical conduit should be sealed and cracks around doors and windows should be sealed, and cracks around doors and windows should be weatherproofed. Tree limbs should be kept well away from the roof and walls of the house.

Rodentproof Your Building to Prevent Rodent Entry

  • Close all openings larger than ¼ inch to exclude rats and mice.
  • Repair or replace damaged vent screens.
  • Screen vents, holes and overlapping roof with 16 or 20 gauge ¼ inch hardware cloth.
  • Use sheet metal collars around pipe entrance on wooden walls.
  • Use cement fill around pipe in brick, stone or stucco walls.
  • Subfloor crawlspace entry hole must be sealed with a door or a lid that will excel finger size objects.
  • Removable lids should fit so that the lids must be lifted up to open.
  • Use sheet metal edging along door bottoms to prevent entry and gnawing by rats.
  • Repair broken or open building sewers to prevent sewer rats infesting property from broken or open sewers which connect to the main sanitary sewer where they may live.


Many plants species harbor roof rats. Whenever possible, these plants should be replaced with species which achieve the desirable effects of ground cover, but will not contribute to the rat population. Characteristics to look for in a desirable ground cover are:

  • Plants should be low growing, not more than 10 inches in height.
  • They should not be climbers.
  • Fruiting plants should not be used.
  • Plants should provide soil stabilization.
  • Plants should require a minimum amount of water once established.
  • Once established, plants should be properly maintained.