Norway rats, Rattus norvegicus, sometimes called brown or sewer rats, are stocky burrowing rodents that are larger than roof rats. Their burrows are found along building foundations, beneath rubbish or woodpiles, and in moist areas in and around gardens and fields. Nests can be lined with shredded paper, cloth, or other fibrous material. When Norway rats invade buildings, they usually remain in the basement or ground floor. Norway rats live throughout the 48 contiguous United States. While generally found at lower elevations, this species can occur wherever people live.
Roof rats, sometimes called black rats, are slightly smaller than Norway rats. Unlike Norway rats, their tails are longer than their heads and bodies combined. Roof rats are agile climbers and usually live and nest above ground in shrubs, trees, and dense vegetation such as ivy. In buildings, they are most often found in enclosed or elevated spaces such as attics, walls, false ceilings and cabinets. The roof rat has a more limited geographical range than the Norway rat, preferring ocean-influenced, warmer climates. In areas where the roof rat occurs, the Norway rat might also be present.
How to Spot a Rat Infestation
Inspect your yard and home thoroughly. If the answer to any of the following questions is yes, you may have a rat problem.
• Do you find rat droppings around dog or cat dishes or pet food storage containers?
• Do you hear noises coming from the attic just after dusk?
• Have you found remnants of rat nests when dismantling your firewood stack?
• Does your dog or cat bring home dead rat carcasses?
• Is there evidence rodents are feeding on fruit/nuts that are in or falling from the trees in your yard?
• Do you see burrows among plants or damaged vegetables when working in the garden?
• Do you see rats traveling along utility lines or on the tops of fences at dusk or soon after?
• Have you found rat nests behind boxes or in drawers in the garage?
• Are there smudge marks caused by the rats rubbing their fur against beams, rafters, pipes, and walls?
• Do you see burrows beneath your compost pile or beneath the garbage can?
• Are there rat or mouse droppings in your recycle bins?
• Have you ever had to remove a drowned rat from your swimming pool or hot tub?
• Do you see evidence of something digging under your garden tool shed or doghouse?
BIOLOGY AND LIFE CYCLE
Rats, like house mice, are active mostly at night. They have poor eyesight, but they make up for this with their keen senses of hearing, smell, taste, and touch. Rats constantly explore and learn, memorizing the locations of pathways, obstacles, food and water, shelter, and features of their environment. They quickly detect and tend to avoid new objects and novel foods. Thus, they often avoid traps and baits for several days or more following their initial placement. While both species exhibit this avoidance of new objects, this neophobia is usually more pronounced in roof rats than in Norway rats.
Both Norway and roof rats can gain entry to structures by gnawing, climbing, jumping, or swimming through sewers and entering through toilets or broken drains. While Norway rats are more powerful swimmers, roof rats are more agile and are better climbers.
Norway rats eat a wide variety of foods but mostly prefer cereal grains, meats, fish, nuts, and some fruits. When searching for food and water, Norway rats usually travel an area of about 100 to 150 feet in diameter; seldom do they travel any further than 300 feet from their burrows or nests. The average female Norway rat has 4 to 6 litters per year and can successfully wean 20 or more offspring annually.
Roof rats routinely travel up to 300 feet for food. They can live in the landscaping of one residence and feed at another. They often can be seen at night running along overhead utility lines or fence tops. They have an excellent sense of balance and use their long tails to steady themselves while traveling along overhead utility lines. They move faster than Norway rats and are very agile climbers, which enables them to quickly escape predators. They can live in trees or in attics and climb down to a food source. The average number of litters a female roof rat has per year depends on many factors, but generally it is 3 to 5 with 5 to 8 young in each litter.
Rats eat and contaminate foodstuffs and animal feed. They also damage containers and packaging materials in which foods and feed are stored. Both rat species cause problems by gnawing on electrical wires and wooden structures such as doors, ledges, corners, and wall material, and they tear up insulation in walls and ceilings for nesting.
Norway rats can undermine building foundations and slabs with their burrowing activities and can gnaw on all types of materials, including soft metals such as copper and lead, as well as plastic and wood. If roof rats are living in the attic of a residence, they can cause considerable damage with their gnawing and nest-building activities. They also damage garden crops and ornamental plantings.
Among the diseases rats can transmit to humans or livestock are murine typhus, leptospirosis, salmonellosis (food poisoning), and ratbite fever. Plague is a disease that both roof and Norway rats can carry, but in California it is more commonly associated with ground squirrels, chipmunks, and native wood-rats.
A successful rat control strategy typically includes three elements: sanitation measures; building construction and rodent proofing; and, if necessary, population control.
Sanitation is fundamental to rat control and must be continuous. If sanitation measures aren’t properly maintained, the benefits of other measures will be lost and rats will quickly return. Good housekeeping in and around buildings will reduce available shelter and food sources for Norway rats and, to some extent, roof rats. Neat, off-the-ground storage of pipes, lumber, firewood, crates, boxes, gardening equipment, and other household goods will help reduce the suitability of the area for rats and also will make their detection easier. Collect garbage, trash, and garden debris frequently, and ensure all garbage receptacles have tight-fitting covers. Where dogs are kept and fed outdoors, rats can become a problem if there is a ready supply of dog food. Feed your pet only the amount of food it will eat at a feeding, and store pet food in rodent-proof containers.
Treatments for rats can be a tricky process since these are very wary creatures. Arrest-A-Pest, Inc. has been solving this type of rodent problem since 1986. A rat infestation can grow into huge problem over a relatively short period of time. For the solution to your problem, Contact Arrest-A-Pest at firstname.lastname@example.org or call us at 1-800-338-PEST.