Mice and Rats

House Mice: A prolific breeder, the House Mouse is sexually mature at 2 months old, has a gestation period of only 3 weeks. The House Mouse is a nibbler, consuming small quantities of food at many feedings. They are known reservoirs of diseases such as rickettsial pox (mites), typhus (fleas), and filth problems with Salmonella, tapeworm, roundworm, and others parasites.



Identification: Adults remain small, less than 7 inches long from tip of nose to tip of tail. They have hairless, scaly tails that separate them from meadow or deer mice, and ears relatively bare of hairs. A young rat looks similar to the House Mouse, but the rat has feet and eyes that are disproportionately large in comparison with its head and body.



Control: The full complement of traps and baits are effective on mice. Exclusion should consider closing any openings as wide as ¼ inch, along with elimination of any harborage sites that are not needed, such as waste piles, packing boxes, wood piles, or heavy outside vegetation. Like the other domestic rodents they prefer to remain against vertical surfaces, in contact with their “guard hairs” on their body, and control measures should be placed against these pathways.


Brown or Norway Rats: It is primarily a ground dweller, although it can climb very well, and prefers to reside in burrows. It swims very well and often lives in sewers and other underground water systems. It is primarily a nocturnal animal, and will restrict its range of movement only to that which is needed to find food and water, perhaps only 20 or 30 feet from home. Norway Rats are omnivores and opportunistic feeders, feeding on any natural or human foods available. They are neophobic and may avoid new objects placed in their environment for some time. Damage from gnawing can be extensive, as they chew on pipes of plastic or metal, wires, wood, or furnishings and walls, and will commonly bite humans. They have the potential to spread disease, such as Leptospirosis and other infections.

Control: Habitat modification to eliminate harborage sites is effective, along with proper building maintenance to exclude their entry. Elimination of available interior and exterior food and water supplies is needed. The proper use of bait and traps can be highly effective. The shyness these rats exhibit toward new objects can affect the response to bait boxes and traps. Glue trays may not be highly effective due to the strength of this species, and its ability to pull free from the glue. Like the other domestic rodents they prefer to remain against vertical surfaces, in contact with their “guard hairs” on their body, and control measures should be placed against these pathways.


Black or Roof Rats: The Roof Rat is an “arboreal” animal, preferring to live above ground level in trees, although it has adapted well to upper areas of structures as well, living in attics and traveling by means of wires and cables attached to homes. It is nocturnal and secretive, staying out of view within the foliage provided in landscaped environments, and feeding heavily on the fruits, nuts, vegetables, or garden snails found there. Like the Norway Rat is also shy around new objects in its familiar environment, and may avoid control measures such as traps or bait stations. Peaks in breeding occur in the spring and the fall. Problems from Roof Rats include the potential for disease, such as plague, they are extremely destructive to stored food products in structures, crops in residential areas, and cause tremendous damage due to their gnawing on structural members, pipes, and electrical wires.

Control: Exclusion from structures is of high importance in preventing entry and damage from this rat. They can enter through any opening wider than one half inch, swim well, and can climb any rough surface, along wires and cables, and can jump vertically about 3 feet. Glue trays work very well for Roof Rats, along with snap traps placed in runways and bait stations using various formulations. Like the other domestic rodents they prefer to remain against vertical surfaces, in contact with their “guard hairs” on their body, and control measures should be placed against these pathways.