A source for
information on rats
Roof Rat Rattus rattus
Larger rodents that may grow to a body length of 10 to 12 inches. Seldom will a rat weigh more than one
Can vary from gray to brown to black.
Few people really like rats or mice, and no one wants them in their house. Rodents live everywhere
outside and could enter at any time, but fortunately, this does not occur often. Usually, most home
invasions occur in the fall, not because of cooler weather, but because the seeds and plants on which
rodents feed outside are gone. Rats and mice must then seek new food sources. Unfortunately, one of these
sources may be your home. Rats are excellent climbers and are capable of gaining entry through holes around
soffit vents and around cables entering the building, through holes in gable vent screens, and through
turbine and box vents on roofs. Many garage doors on homes allow enough space for rats to fit underneath,
Outside, rats live in fields, wooded areas, vacant lots, farms, and just about anywhere people have
buildings. Rats are seldom a problem in homes except in urban and rural areas. This is due in large part to their
size, since rats need a hole about the size of a quarter in order to gain entry into a building. Rats however, may
find harborage in many areas around the home - especially in stacked firewood, stones and bricks, and piles of
leaves or other debris.
Roof rats are more aerial than Norway rats in their habitat selection and often
will live in trees. Landscaped residential or industrial areas provide good nesting sites, as does vegetation of
riverbanks and streams. They will often move into sugarcane and citrus groves and have been found in palm trees.
Roof rats are sometimes found living in or around poultry or other farm buildings as well as in industrial sites
where food and shelter are available.
Roof rats are agile climbers, utilizing their long tails for balance, and frequently enter buildings from the roof
or utility lines, which they use to travel from area to area. They are sometimes found in garbage cans and sewer
systems, though these habitats are preferred more by Norway rats.
Medical and Economic Significance:
Roof rats pose both a health and safety hazard. It has been implicated in the transmission of a number of diseases
to humans, including murine typhus, leptospirosis, salmonellosis, rat-bite fever, and plague. It is also capable of
transmitting a number of diseases to domestic animals and is suspected in the transference of ectoparasites from
one place to another.
In addition to consuming and contaminating stored food and animal feed, roof rats will gnaw on wiring (which can
pose a fire hazard), and tear up insulation to use it for nesting material. They may also feed on the fruit and
vegetable portions of commercial and residential trees and garden plants.
Black or brown, seven to 10 inches long, with a long tail, large ears and eyes, and a pointed nose. Body is
smaller and sleeker than Norway rat. Fur is smooth.
Nests inside and under buildings, or in piles of rubbish or wood. Excellent climber that can often be found in
the upper parts of structures.
Omnivorous, but shows a preference for grains, fruits, nuts and vegetables.
Becomes sexually mature at four months, producing four to six litters per year that consist of four to eight
young each. Lives up to one year.
Roof rats are very sensitive to changes in their environment and have a strong tendency to avoid new objects in
their environment, so baiting or trapping on the ground or floor may have little effect. They may take several days
before they will approach a bait station or trap.
Proper sanitation is somewhat more effective in lessening Roof rat infestations. Secure garbage cans with heavy
lids and avoid letting it accumulate. Store bulk foods, bird seed and dry pet food in tight-fitting containers, and
remove standing water outside in pet food bowls, etc. Harvesting citrus and other fruit in a timely manner and
picking up fallen fruit promptly will also help reduce Roof rat populations.
Seal any openings larger than 1/4 inch to exclude both rats and mice. Openings where utility pipes enter buildings
should be sealed tightly with metal or concrete. Seal all vents and openings with concrete or heavy-duty metal
screening. Equip floor drains and sewer pipes with tight-fitting grates with openings less than 1/4 inch in
diameter. Doors, windows and screens should fit tightly; it may be necessary to cover edges with sheet metal to
Outside, mow, trim or remove ground cover plants that grow over one foot in height. Stack firewood, lumber, and
other materials at least one foot away from walls and fences. Prune the tops of palm trees and remove dead fronds.
Remove tree limbs that overhang roofs, and prune trees so that branches do not touch fences, overhead wires, or the
branches of adjacent trees.
The best way to avoid invasions of rats is to (1) provide as little harborage as possible that might attract
rodents, and (2) seal as many holes and cracks in the outside of the home as possible through which rats might
enter. The following recommendations should be followed to help prevent rats from seeking the food and shelter
provided by your home:
- Keep firewood stored as far from the home as possible and store it off the ground. During the winter, store
only enough wood next to the house to burn every couple of days.
- If possible, remove any piles of debris, stones, bricks, etc. If these are near the foundation of the home
they serve as harborages to attract rodents. Once there, it is any easy step for rodents to enter the building
- Seal any hole or crack larger than 1/4 of an inch. Large holes or cracks should be stuffed with steel wool
or wire mesh before sealing with caulk or foam, otherwise rodents could chew through to enter.
- Install a good, thick weatherstrip on the bottom of all doors to prevent rodents from entering. The garage
door may prove difficult to seal completely, so the door from the garage to the house must be sealed
- Remember, our service includes coverage of commensal rats and mice, and much of the service provided
during the colder months is to inspect for signs of rodents and to maintain preventive control measures.