Environmental Disease Control – Rodents
Habits and Characteristics
Rodents are characterized by teeth adapted for gnawing and for chewing. The Rodentia is by far the largest mammalian order; nearly half of all mammal species are rodents. They are worldwide in distribution and are found in almost every terrestrial and freshwater habitat, from the shores of the Arctic Ocean to the hottest deserts. They are variously adapted for running, jumping, climbing, burrowing, swimming, and gliding. Many of them have dexterous forepaws, which they use as hands while sitting on their haunches in a position characteristic of many rodents.
Types of Rodents
The approximately 4,000 rodent species are divided on the basis of their anatomy into three well-defined groups, or suborders, and more than 30 families. The Sciuromorpha, or squirrellike rodents, include the various species of squirrel, chipmunk, marmot, woodchuck (or ground hog), prairie dog, gopher (or pocket gopher), pocket mouse, kangaroo rat, and beaver. The Myomorpha, or mouselike rodents, include a great variety of mouse and rat species, as well as species of hamster, vole, muskrat, gerbil, and dormouse. This is the largest rodent group. The Hystricomorpha, or porcupinelike rodents, include the porcupine, nutria (or coypu), cavy (including the domestic guinea pig), mara, and chinchilla, as well as many species whose common names include the term rat (e.g., the roof rat).
Some Common Signs of Rodent Infestation
Probably mice and rats are the biggest “pests” of the rodent family. Do you think you have rodents infesting your home or workplace, but aren’t sure? Here are some common signs that you may have a rodent problem.
- You see rodent droppings. This is one of the most reliable signs that you have a rodent problem. You may find droppings in places where you store your food or your pet/animal food, such as in cupboards and drawers or in bins. Because mice like to run in places that offer them some protection from predators, you may find droppings in cupboards or under the sink, along walls, or on top of wall studs or beams. Mice will leave droppings near their nests as well (see below). Storage rooms, sheds, barns, or cabins loaded with boxes, bags, old furniture, and other objects make an ideal home for rodents, so you may find droppings there, even inside boxes and other containers. Workplaces can also make good rodent homes. Warehouses, restaurants, and the like are obvious places to look because food may be plentiful there. However, rodents can infest office buildings, too. Once again, look for droppings in protected places, such as closets, storage rooms, or inside boxes.
- You see signs of rodent nests. Rodents tend to build their nests from materials that are soft, fuzzy, or warm. Among common rodent nest materials are shredded paper, bunches of dry grass or small twigs, fabric, and furniture stuffing. Rodents will nest wherever safety from enemies can be found close enough to food and water, and they prefer places that are relatively quiet. Inside buildings, here are some places to look:
You find food boxes, containers, or food itself that appears to be nibbled. Look for droppings nearby. Rodents can chew through plastic, so plastic bags do not make safe food storage containers.
You find signs of rodent “feeding stations.” These are semi-hidden spots where rodents eat food they have collected. At these stations, rodents may leave larger-than-normal amounts of droppings/urine, plus remnants of a variety of foods (such as nut shells), bits of plastic or paper, and cockroach carcasses.
You find evidence of gnawing. To get to food, rodents will gnaw on almost anything that is softer than the enamel of their teeth. This includes such things as wood, paper board, cloth sacks, and materials even harder than these. Because rodents’ teeth grow continuously, they must gnaw to keep them short. That may help to explain why chair legs or similar surfaces show gnawed spots or tooth marks in rodent-infested places.
You notice an odd, stale smell. In closed-up rooms infested by rodents, you will commonly smell an unusual, musky odor.
You see a mouse in your home. However, this doesn’t happen very frequently! Why? Rodents are normally active at night, and generally avoid humans. If you have rodents, unless the infestation is large, you may never see one. Remember that not all types of rodents carry hantavirus. Neither common house mice nor common rats have been associated with hantavirus in humans, for example. Yet because it can be tough to tell just what kind of rodents you have, play it safe — clean up the infestation and rodent-proof your home or workplace.
- inside cabinets
- under or inside dressers
- in and among boxes
- behind and inside machinery and appliances (kitchen appliances such as stoves or refrigerator drip pans; water coolers; and electric motor cases or computer cases)
- inside upholstered furniture inside double walls or the space between floors and ceilings.
Rodent-proofing Your Home or Workplace
Ideally, the best way to control mice and rats is to make it impossible for them to find a way into structures, but with mice it can be difficult to exclude them completely, since even an adult mouse can squeeze into openings no larger than 3/8 inch. Mice also enter buildings by way of open windows and doors or can be carried in with merchandise, but nevertheless, it is good pest management to make your home or business as pest resistant as possible. Every possible route into your home should be considered when going about a pest proofing program.
Questions to ask are:
- Are there holes around the eaves and under roof overhangs that would allow rodent entry?
- Is that space under the back door large enough to allow mice to squeeze under?
- Are bushes and trees with low hanging branches touching or in close proximity to my home or business?
- Do I leave the doors propped open for any length of time, especially at night?
- Are there open drains leading into my home or business? Are the windows in my basement broken?
All these questions need to be answered, and if any can be answered with a yes, then steps should be taken to correct the problem.
Sometimes it is not possible to take care of every problem that comes up because of health, money or inclination; but there are many cases where rodent proofing can be accomplished with a minimum of effort. Rodent proofing is one of the cheaper and less painful ways to avoid and/or exclude pests.
Rodent removal and clean-up guidelines
- Set traps that will kill the mouse or rat. Use peanut butter as bait.
- Wear rubber gloves and spray the nest area or dead rodents with a household insecticide that kills fleas. Be sure to follow the label instructions and wait at least one hour for the insecticide to work.
- Nest, spray the nest or dead rodent until soaked with a household disinfectant solution, such as Lysol, mixed as recommended on the label. A solution of one part household bleach to nine parts water may be used, but is may damage rugs and fabrics and irritate skin. Let the area soak for 10 to 15 minutes. Spraying disinfectant will help to kill the virus and settle the dust.
- Remove the nest or rodent using a long handled shovel.
- Double bag the rodent or nest securely with plastic bags and dispose of them in the trash.
- Clean up the rodent area, or any area with sign so of droppings, by spraying it with the disinfectant. Let the area soak for 10 to 15 minutes. While still wearing gloves, wipe up the area with paper towels or rags. Double-bag all paper towels, rags and gloves used in the clean-up. Dispose of them in the trash.