Pest Control – Rats – Mice
Mice
Mice are the most common rodent found in our area in houses and commercial buildings. The main species is the common house mouse, but field mice occasionally come inside in winter.
Mice are usually first noticed in the kitchen, where you may find their droppings. They tend to nibble and damage several different types of packaged foods. Mice are great climbers, and will often follow water and drain pipes as well as electrical conduit and wiring. They will use almost anything they can gnaw to build their nest such as paper, labels from jars and canned goods, fabrics, etc. Nests have been found in the bottom of boots and shoes. Sometimes, mice are suspected because of noises in the walls.
Once mice have become established, several methods are available to eliminate them. It is always helpful to eliminate clutter and to close up entry holes. Mice can come in through surprisingly small holes but these can effectively be sealed. However, especially in older structures, new entry holes can appear so a yearly inspection is a good idea. Mice often get in through poorly fitted garage doors and other such spaces. They often travel along pipe conduits and these conduits can be sealed so that there is no room for the mouse to pass.
Although it is possible to eliminate mice without a professional, it is a good idea to work with a professional who knows mouse habits and can both correct immediate problems and point out preventative measures unique to your situation. In addition, there are several methods to eliminate mice including various traps and bait stations. Each has advantages and disadvantages, and your pest control professional can work with you to choose a method that is the best fit for your situation.
Rats
Biology and Life cycle – Rats, like house mice, are mostly active 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 about their environment, memorizing the locations of pathways, obstacles, food and water, shelter, and other elements in their domain. They quickly detect and tend to avoid new objects placed in a familiar environment. Thus, objects such as traps and baits often are avoided for several days or more following their initial placement. While both species exhibit this avoidance of new objects, it is usually more pronounced in roof rats than in Norway rats.
Both Norway and roof rats may gain entry to structures by gnawing, climbing, jumping, or swimming through sewers and entering through the toilet or broken drains. While Norway rats are more powerful swimmers, roof rats are more agile and are better climbers.
Norway and roof rats do not 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 will dominate the basement and ground floors, with roof rats occupying the attic or second and third floors. Contrary to some conceptions, the two species cannot interbreed. Both species may share some of the same food resources but do not feed side-by-side. Rats may 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 may gnaw to enlarge the gap, but this may 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 four to six litters per year and may successfully wean 20 or more offspring annually.
Roof Rats. Like Norway rats, roof rats eat a wide variety of foods, but their food preferences are primarily fruits, nuts, berries, slugs, and snails. Roof rats are especially fond of avocados and citrus and 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. The rind of a lemon is often eaten, 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 may live in the landscaping of one residence and feed at another. They can often be seen at night running along overhead utility lines or fence tops. They have an excellent sense of balance and use their long tails for balance 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 may 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 is three to five with from five to eight young in each litter.
DAMAGE CAUSED BY RATS
Rats consume and contaminate foodstuffs and animal feed. They also damage containers and packaging materials in which foods and feed are stored. Both species of rats cause problems by gnawing on electrical wires and wooden structures (doors, ledges, in corners, and in wall material) and tearing up insulation in walls and ceilings for nesting.
Norway rats may undermine building foundations and slabs with their burrowing activities. They may also 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 may transmit to humans or livestock are murine typhus, leptospirosis, trichinosis, salmonellosis (food poisoning), and ratbite fever. Plague is a disease that can be carried by both roof and Norway rats, but it is more commonly associated with ground squirrels, chipmunks, and native wood rats.