PEST CONTROL SACRAMENTO, ROSEVILLE, AND FOLSOM: RODENTS IN SACRAMENTO, ROSEVILLE, AND FOLSOM

There are three major rodents we deal with in Sacramento, Roseville, and Folsom: the Roof Rat, Norway Rat, and the House Mouse.

ROOF AND NORWAY RATS

Rats are some of the most troublesome and damaging rodents in the United States. They eat and contaminate food, damage structures and property, and transmit parasites and diseases to other animals and humans. Rats live and thrive in a wide variety of climates and conditions and are often found in and around homes and other buildings, on farms, and in gardens and open fields.

Roof Rat rodents in Sacramento, Roseville, and Folsom

 

 

 

 

 

 

 

Key characteristics
between Norway and roof rats.

Roof Rat rodents in Sacramento, Roseville, and Folsom

 

 

 

 

 

 

 

 

Key differences between a mouse
and young rat.

Table 1. Identifying Characteristics of Adult Rats.
Characteristic Roof rat Norway rat
general appearance sleek, agile large, robust
color of belly gray to white mostly gray
body weight 5 to 10 ounces 7 to 18 ounces
tail extends at least to snout, uniformly dark with fine scales shorter than body, dark above and pale below, scaly
head pointed muzzle blunt muzzle
ears long enough to reach eyes if folded over don’t reach eyes

IDENTIFICATION

People don’t often see rats, but signs of their presence are easy to detect. In California, the most troublesome rats are two introduced species, the roof rat and the Norway rat. It’s important to know which species of rat is present in order to choose effective control strategies.

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, R. rattus, 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. If you are unsure of the species, look for rats at night with a bright flashlight, or trap a few. The illustrations above show some of the key physical differences between the two species of rats, while Table 1 summarizes identifying characteristics.

While rats are much larger than the common house mouse or meadow vole, a young rat is occasionally confused with a mouse. In general, very young rats have large heads and feet in proportion to their bodies, whereas those of adult mice are proportionately much smaller. While both rats and mice gnaw on wood, rats leave much larger tooth marks than mice do.

How to Spot a Rat Infestation

Because rats are active throughout the year, periodically check for signs of their presence. Once rats have invaded your garden or landscaping, unless your house is truly rodent proof, it is only a matter of time before you find evidence of them indoors. Experience has shown it is less time consuming to control rodents before their numbers get too high, and fewer traps and less bait will be required if control is started early.

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 and roof rats don’t get along. The Norway rat is larger and the more dominant species; it will kill a roof rat in a fight. When the two species occupy the same building, Norway rats may dominate the basement and ground floors, with roof rats occupying the attic or second and third floors. Contrary to some conceptions, the two species can’t interbreed. Both species can share some of the same food resources but don’t feed side by side. Rats can grab food and carry it off to feed elsewhere.

Rats of either species, especially young rats, can squeeze beneath a door with only a 1/2-inch gap. If the door is made of wood, the rat might gnaw to enlarge the gap, but this might not be necessary.

Norway Rats

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

Like Norway rats, roof rats eat a wide variety of foods, but they prefer fruits, nuts, berries, slugs, and snails. Roof rats are especially fond of avocados and citrus, and they often eat fruit that is still on the tree. When feeding on a mature orange, they make a small hole through which they completely remove the contents of the fruit, leaving only the hollowed-out rind hanging on the tree. They’ll often eat the rind of a lemon, leaving the flesh of the sour fruit still hanging. Their favorite habitats are attics, trees, and overgrown shrubbery or vines. Residential or industrial areas with mature landscaping provide good habitat as does riparian vegetation of riverbanks and streams. Roof rats prefer to nest in locations off the ground and rarely dig burrows for living quarters if off-the-ground sites exist.

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.

DAMAGE

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 woodrats.

HOUSE MOUSE

The house mouse, Mus musculus, is one of the most troublesome and costly rodents in the United States. House mice thrive under a variety of conditions; they are found in and around homes and commercial structures as well as in open fields and on agricultural land. House mice consume and contaminate food meant for humans, pets, livestock, or other animals. In addition, they cause considerable damage to structures and property, and they can transmit pathogens that cause diseases such as salmonellosis, a form of food poisoning.

IDENTIFICATION

Adult house mouse.

House mice are small rodents with relatively large ears and small, black eyes. They weigh about 1/2 ounce and usually are light brownish to gray. An adult is about 5 to 7 inches long, including the 3- to 4-inch tail.

Droppings, fresh gnaw marks, and tracks indicate areas where mice are active. Mouse nests are made from finely shredded paper or other fibrous material, usually in sheltered locations. House mice have a characteristic musky odor that reveals their presence. Mice are active mostly at night, but they can be seen occasionally during daylight hours.

While the house mouse hasn’t been found to be a carrier of hantavirus, the deer mouse, Peromyscus maniculatus,, which sometimes invades cabins and outbuildings in California, harbors the Sin Nombre virus, which causes a rare but often fatal illness known as hantavirus pulmonary syndrome (HPS). The house mouse is distinguished from the deer mouse by its overall gray coat. The deer mouse has larger eyes and a white underside with a distinct line of demarcation between the dark coloration on top and the white underside. In addition, the tail on the house mouse has almost no fur on it, whereas the tail of the deer mouse is moderately to well furred and is light underneath and dark on top. Before attempting to clean up premises where deer mice have been present, contact your county health department or the California Department of Public Health, or see the Centers for Disease Control and Prevention Web site (www.cdc.gov/rodents/) for information about how to prevent hantavirus exposure.

BIOLOGY

Native to Central Asia, the house mouse arrived in North America on ships with settlers from Europe and other points of origin. A very adaptable animal, the house mouse often lives in close association with humans, along with Norway rats and roof rats; however, mice are more common and more difficult to control than rats.

Although house mice usually prefer to eat cereal grains, they are nibblers and will sample many different foods. Mice have keen senses of taste, hearing, smell, and touch. They also are excellent climbers and can run up any rough vertical surface. They will run horizontally along wire cables or ropes and can jump up to 12 inches from the floor onto a flat surface. Mice can squeeze through openings slightly larger than 1/4 inch across. House mice frequently enter homes in autumn, when outdoor temperatures at night become colder.

In a single year, a female may have 5 to 10 litters of about 5 or 6 young. Young are born 19 to 21 days after conception, and they reach reproductive maturity in 6 to 10 weeks. The life span of a mouse is usually 9 to 12 months.

North American Pest Management has been controlling rodents in the greater Sacramento, Roseville, and Folsom areas for over 35 years. We are experts in not only finding rodent entry points but sealing up the openings as well.

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