DISTRIBUTION It is now found throughout the world, from the tropics to the Arctic and Antarctic.
DESCRIPTION House mice should not be confused with young rats. The mouse's head and feet are in proportion to its body. House mice are extremely prolific breeders.
At 35 days of age they mature and carry embryos for 18 - 21 days. If a female aborts, she can become pregnant again within 48 hours. The average litter size is about six. Variation in genetics, food supply and temperatures can affect these numbers. A female suckles her young for about four weeks. The female may become pregnant following parturition or while lactating. Therefore if all goes well, a female can have litters approximately every 40 - 50 days. Under optimum conditions (often found indoors) mice can breed through the year. Newborn mice are extremely small, pink and naked. After about three weeks they are fully covered with hair, make short trips from the nest and begin feeding on solid food. Mice usually live for 15 - 18 months.

DISTRIBUTION The Norway rat is the most common of rats and occurs practically everywhere. The roof rat is found commonly in sea ports and is also a house rat.
DESCRIPTION The males are capable of pairing at all times but the females are receptive only during heat periods which may extend to nine months. The number of young in a litter may vary from 6 to 22. The average number in pregnant females is 6 to 8. There may be from 3 to 12 litters in a single year with an average of 3 to 6 per annum. Newborn rats depend on their mother for food for about three weeks and then feed on solid food.
The life of rats in a population is about six months.
HABITS Rats and mice have rather poor vision and are colorblind, but the sense of smell, taste, hearing and touch are keenly developed. They usually become active half an hour after dusk, after the premises have become quiet. When unmolested, rats roam about seeking food during any part of the day or night.
One of the favorite nesting places for rats in buildings is the closed space under the building ground floor. All other closed spaces of buildings may be utilized by rats if they can gain access to them. Nests will often be found in piles of rubbish and merchandise if the latter is stored over a month without being moved. In residential areas they live outdoors in yards, garages, sheds and in sewers. They also dig the earth in the tunnels with their front feet and shove the loose soil back under their belly. They can also run, climb, jump and swim.
POTENTIAL HAZARDS Rodents similarly infest our structures, destroy and contaminate our food supply . They are responsible for damage in the home and warehouse. They gnaw upholstery, bolts of silk, papers, books and like items for nesting material. They also gnaw hard substances such as bone, aluminum, lead and similar materials. The tooth enamel has a hardness index of 5,5 times harder even than steel. And the jaws can exert pressures of 24,000 lbs./inc2. Rats can readily chew through plastic water pipes, irrigation systems and garbage cans. Accounts have been made of the rat's ability to start fires by carrying matches to their hiding places, as well as by causing short circuits through the gnawing of electrical wires.
Disease organisms may be transmitted either directly through the rodent's bite or carried from the rodent to a flea, tick or mite, which bites man and transfers the pathogen, or by contaminating food or water with their dung or urine (plague, murine typhus fever, leptospirosis - trichinosis - food poisoning)
PREVENTION Two principles must be kept in mind in the rat-proofing of buildings:
  • The exterior of those parts of the structure accessible to rats, including porches or other appurtenances, must be constructed of materials resistant to the gnawing of rats, and all openings must be either permanently closed or protected with doors, gratings or screens.
  • The interior of the building must provide no dead spaces, such as double walls, spaces between ceiling and floor, staircases, and boxed-in piping, or any places where a rat might find safe harborage, unless they are permanently sealed with impervious materials.
CONTROL A complete rodentification program must be applied for successful elimination. Recognition of runways, nests and burrows is very important. Useful tools such as anticoagulant rodenticide are available. Glue boards, snap traps and ultrasonic devices are available but less effective in heavy infestation.

Characteristic Norway Rat Roof Rat House Mouse
General appearance large , robust sleek ,graceful small,slender
Adult size Weight (gm) 7-18 oz/200 - 500g 5 - 9 oz/150 - 250g 0,4 - 1 oz/12 - 30g
Length ( nose to tip of tail )
Head and body ( mm )
7- 9,5 in/18-25 cm 6 - 8 in/16 - 20 cm 2 - 3,5 in/6 -9 cm
Tail ( mm ) 6 - 8 in/15 - 21 cm 7 - 10 in/19 - 25 cm 3 - 4 in/7 -10 cm
Snout blunt pointed pointed
Ears small,covered with short hair do not reach eyes.. large ,nearly naked can be pulled over eyes large,some hair
Eyes small large,prominent small
Tail dark above,pale beneath uniformly dark uniformly dark
Fur brown with scattered black ( agouti ) venter grey to yellow/white
agouti to gray to black venter white gray or black
Light brown
Light gray
Droppigs capsule shaped, 2cm / 3/4 - 1 in spindle shaped,
1 cm / 0,5 in
rod shaped,
3 6 mm / 0,5 in
Sight poor,color blind poor, color blind poor ,color blind
Smell, taste, touch, hearing excellent excellent excellent