Mice As Pest: Mouse Traps, House Mouse Control & Prevention

Facts on Mice
The house mouse (Mus musculus) is considered one of the most troublesome and economically damaging pests in the United States. Mice can be harmful pests, damaging and eating crops and spreading diseases through their parasites and feces. In the Western United States, breathing dust that has come in contact with mouse feces has been linked to the deadly hantavirus. House mice live and thrive under a variety of conditions in and around homes and farms. House mice consume food meant for humans or pets. They contaminate food-preparation surfaces with their feces, which can contain the bacterium that causes food poisoning (salmonellosis). They can gnaw on wood, which causes damage to home structures and property.

Warning: Graphic Visual: Mouse infestation on a farm in Australia in 1993. Livestock attacked.

Recognizing Mouse Infestations
Mouse droppings, fresh gnawing and tracks, wood shavings indicate areas where mice are active. Mouse nests, made from fine shredded paper or other fibrous material, are often found in sheltered locations. House mice have a characteristic musky odor that identifies their presence. Mice are occasionally seen during daylight hours. You may also hear a mouse rustling, especially with food or wrappers, while you are in an adjacent room in a quiet house.

House Mouse Facts
House mice are gray or brown rodents with relatively large ears and small eyes. An adult weighs about 1/2 ounce and is about 5 1/2 to 7 1/2 inches long, including the 3 to 4 inch tail.

Although house mice usually feed on cereal grains, they will eat many kinds of food. They eat often, nibbling bits of food here and there. Mice have keen senses of taste, hearing, smell and touch. However, they cannot see red light. Mice can open plastic or mylar type candy or energy bar wrappers. However, eating chocolate can be fatal to mice. Most mice are omnivores; they will eat meat, the dead bodies of other mice, and have been observed to self-cannibalize their tails during starvation. Grasshopper mice are an exception to the rule, being the only fully carnivorous mice. Mice eat grains, fruits, and seeds for a regular diet, which is the main reason they damage crops.  Mice are often portrayed to enjoy cheese and people sometimes use it as mousetrap bait, though mice actually do not like cheese due to its fatty texture. Instead, they like food that contains high sugar.

They are excellent climbers and can run up any rough vertical surface. They will run horizontally along wire cables or ropes and can jump up 13 inches from the floor onto a flat surface. They can slip through a crack that a pencil will fit into (sightly larger than 1/4 inch in diameter).

Warning graphic: Giant centipede eating a mouse.

In a single year, a female may have five to 10 litters of usually five or six young each. Young are born 19 to 21 days after mating, and they are mature in six to 10 weeks. The life span of a mouse is about nine to 12 months. In extreme lifespans they may live up to two years in the lab, but the average mouse in the wild lives only about 5 months, primarily due to heavy predation. Cats, wild dogs, foxes, birds of prey, snakes and even certain kinds of insects, such as giant centipedes have been known to prey heavily upon mice. A Giant Centipede can eviscerate a mouse in minutes while holding it down with its many legs. The original motivation for the domestication of cats is thought to have been for their predation of mice. Nevertheless, due to its remarkable adaptability to almost any environment, and its ability to live commensally with humans, the mouse is regarded to be the third most successful mammalian species living on Earth today, after humans and the rat.

Mice are social animals, preferring to live in groups. Mice build nests for protection and warmth, but species differ in their preferences. Most species will construct nests of grass, fibers, and shredded material. Mice do hibernate.

A single pair of mice can produce as much as 2000 offspring in ideal situations.

Prevention and Control
Effective mouse control involves sanitation (eliminating access to food), mouse proof construction (blocking entry from outside) and population reduction (using traps or poison). The first two are useful as preventive measures. When a mouse infestation already exists, some form of population reduction is almost always necessary.

Sanitation. Mice can survive in very small areas with limited amounts of food and shelter. Consequently, no matter how good the sanitation, most buildings in which food is stored, handled or used will support house mice if not mouse-proofed. Although good sanitation will seldom eliminate mice, poor sanitation is sure to attract them and will permit them to thrive in greater numbers. Good sanitation will also reduce food and shelter for existing mice and in turn make baits and traps more effective. Pay particular attention to eliminating places where mice can find shelter. If they have few places to rest, hide or build nests and rear young, they cannot survive in large numbers.

Mouse-Proof Construction. The most successful and permanent form of house mouse control is to “build them out” by eliminating all openings through which they can enter a structure. All places where food is stored, processed or used should be made mouse-proof. Dried grain and meat products should be stored in glass jars, metal canisters or other resealable airtight containers.

Seal any openings larger than 1/4 inch to exclude mice. Steel wool mixed with caulking compound makes a good plug. Patching material needs to be smooth on the surface to prevent mice from pulling out or chewing through the patching compound. Seal cracks and openings in building foundations and openings for water pipes, vents and utilities with metal or concrete. Doors, windows and screens should fit tightly. It may be necessary to cover the edges with metal to prevent gnawing. Plastic sheeting or screen, wood, rubber or other gnawable materials are unsuitable for plugging holes used by mice.

Glue traps: mouse stuck to two glue traps that were placed two aside near the opening at the baseboard between a dishwasher and a kitchen cabinet. The traps had been in place for about two months before the mouse became entrapped. Other glue traps picked up three other mice in one fall season. Bait, which is not necessary, is cereal in this photo.

Traps. Trapping is an effective control method. When only a few mice are present in a building, it is usually the preferred control metho
d. Trapping has several advantages: (1) it does not rely on inherently hazardous poisons, (2) it permits the user to make sure that the mouse has been killed and (3) it allows for disposal of the mouse carcasses, thereby avoiding dead mouse odors that may occur when poisoning is done within buildings. Mice that are poisoned can also defecate heavily and die in undesirable locations, even on furniture or other normally clean areas of a home.

The simple, inexpensive wood-based snap trap is effective and can be purchased in most hardware and grocery stores. Bait traps with peanut butter, chocolate candy, dried fruit or a small piece of bacon tied securely to the trigger. Set them so that the trigger is sensitive and will spring easily. Multiple-capture live traps, which can capture several mice once set, are also available in some hardware and feed stores. Set traps close to walls, behind objects, in dark corners and in places where evidence of mouse activity is seen. Place them so that mice will pass directly over the triggers as they follow the natural course of travel, usually close to a wall. Traps can be set on ledges or on top of pallets of stored materials if mice are active in such locations. Use enough traps to eliminate the rodents quickly. (Using too few traps is a common error by individuals attempting to control mice.) Mice seldom venture far from their shelter and food supply, so place traps no more than 10 feet apart in areas where mice are active. Leaving traps unset until the bait has been taken at least once (prebaiting) often increases the success of trapping. An alternative to traps are glue boards, which catch and hold mice attempting to cross them in much the same way flypaper catches flies. Place glue boards along walls where mice travel. Two or three glue boards placed side-by-side (or the larger glue boards used for rats) will be more effective than individual boards. Do not use them where children, pets or desirable wildlife can contact them. Glue boards can be placed inside tamper-resistant bait boxes in exposed locations. Glue boards lose their effectiveness in dusty areas unless covered and extremes of temperature also may affect the tackiness of the glue. Glue boards are sometimes used to catch a mouse that is wary of snap traps.

Poison Baits (Rodenticides). Rodenticides are poisons that kill rodents. They can be purchased in hardware stores, feed stores, discount stores, garden centers and other places where pesticides are sold. Do not buy unlabeled rodent baits from street vendors or other uncertain sources. Do not purchase baits that have an incomplete label or one that appears to be “homemade.”

“Building out” rodents and trapping are the most effective control methods. Rodent baits should be used only to supplement these methods. If there is a repeated need to use baits, it is likely that sanitation and mouse-proofing should be improved. Remember that rodent baits are poisons. Make sure they are registered with the U.S. Environmental Protection Agency and always follow the label instructions exactly. If baits are used indoors, be sure they are labeled specifically for interior use.

The active ingredients in baits are used at very low levels, so bait shyness does not occur when using properly formulated baits. Most of these baits cause death only after they are eaten for a number of days, although some types can cause death following a single feeding. Make sure that fresh bait is available continuously until mice stop feeding. Depending on the number of mice, this may require up to three weeks.

Bait Selection and Placement. Baits are available in several forms. Grain baits in a meal or pelleted form are available in small plastic, cellophane or paper packets. These sealed “place packs” keep bait fresh and make it easy to place the baits in burrows, walls or other locations. Mice gnaw into the packet to feed on the bait. Block style baits are also very effective for most situations. Proper placement of baits and the distance between placements is important. Place baits in several locations no farther than 10 feet apart and preferably closer. For effective control, baits or traps must be located where mice are living. Use of tamper-resistant bait stations provides a safeguard for people, pets and other animals. Place bait stations next to walls with the openings close to the wall or in other places where mice are active. When possible, secure the bait station to a fixed object to prevent it from being moved. Clearly label all bait stations “Caution—Mouse Bait” as a safety precaution.

Sound and Electronic Devices. Although mice are easily frightened by strange or unfamiliar noises, they quickly become accustomed to regularly repeated sounds and are often found living in grain mills or factories and other noisy locations. Ultrasonic sounds, those above the range of human hearing have very limited use in rodent control because they are directional and do not penetrate behind objects. Also, they lose their intensity quickly with distance. There is little evidence that sound of any type will drive established mice or rats from buildings because they rapidly become accustomed to the sound.

Control by Cats and Dogs. Although cats, dogs and other predators may kill mice, they do not give effective control in most circumstances. In fact, rodents may live in very close association with dogs and cats. Mice and rats may obtain much of their diet from the pet’s dish or from what pets spill.

Diseases Known to be Spread By Mice and Rats
Rickettsial pox a disease similar to chicken pox and is spread to people by mites that are usually found on mice.

Rat bite fever is spread to people when they are bitten by an infected mouse, rat, or other rodent.

Food poisoning (namely salmonellosis) is spread to people when food, food preparation surfaces or dishes are contaminated by saliva, urine or feces from a mouse.

Mice can spread parasites to people such as trichinosis and tapeworms.

Hantavirus is a respiratory disease that is carried by small rodents, especially deer mice. It is spread to people when they breathe in dust that contains the rodents infected saliva, urine or feces. Although uncommon, people can also get hantavirus if they are bitten by an infected mouse.

Plague is spread to people when they come in contact with fleas from infected rodents or when people are bitten by infected rodents. However, today plague is usually spread to people by rodents like prairie dogs and squirrel.