Tell Me More About Mice

Problems

>When mice are present in large numbers, they can and will consume considerable quantities of stored seed and grains. However, this type of damage will still be much less than that caused by the contamination of food with urine and feces. By gnawing wood, paper, cloth, books, and insulation on wiring, mice may also cause considerable property damage. Direct observation will indicate damage, as gnawing leaves paired tooth marks about 1/8 inch wide. Nests may be found in hidden places, such as little-used drawers or cabinets, and are made from loose assemblies of paper, cloth, twine, and other material. Droppings are rod-shaped, about 1/4 to 1/3 inches long and one of the best indicators of mice.

>If it were only a matter of their eating their share of our food, then we could probably coexist with many millions of them and not feel any effect. But by contaminating so much more than they eat, and by serving as a source or vector for diseases that endanger humans, mice are clearly at odds with humanity. The key to managing our conflicts with them, of course, comes in better habitat management: of ours, to eliminate attraction, and of theirs, to make it less suitable.

Solutions

>Tolerance: Sometimes people don’t even know they have mice and live for years with a self-regulating population. Sometimes they will know the mice are there, but be indifferent or tolerant of their presence. And sometimes the discovery of a mouse will immediately be regarded as a crisis in which the animals have to be disposed of immediately. On occasion, native mice move into a building during the early fall or winter as a part of normal movement patterns. These animals can be humanely live-trapped and put back where they came from – the great outdoors. House mice would probably not do well in such evictions, but given the alternative, many homeowners are willing to try. With any mouse problem, it is important to recognize signs of mouse presence early, identify the source of food that attracts them, remove it and the mice, and after the mice are gone, keep others from gaining entry to the house.

>Live Trapping: For those who wish to live trap and remove mice from the house, there are a number of commercially available devices that let this be done easily. Most grocery or hardware stores carry one or more brands of these. Before going to any expense, however, the homeowner may want to rig an improvised live trap by using a bathroom wastebasket. The basket is baited with bread, sunflower seed, peanut butter, or another proven mouse attractant and taken to a place where mice are known to be present. Because mice like to move along a wall or other barrier pressing against their side, traps set along walls are usually more successful than those set in the open. Preferably left along a travel route, the basket is tilted on its side, usually with a “ladder” of bricks or books that the mouse must climb to get to the rim. From there it has to jump or slide down the side of the basket (which it will do) and then ends up being unable to climb back up the slippery surface. Set before going to bed, the trap should be checked early the next morning. If a mouse is caught, it can safely be transported outside. Afterward a dilute (1:30) solution of bleach cleans the basket thoroughly.

>Lethal Control: The killing of rodents is commonly regarded as a necessary step in the management of problems. Usually this killing must be repeated again and again as the rodent population cycles back. Unfortunately, lethal control usually occurs without following up with habitat management, sanitation, or exclusion to provide long-term, economically sensible and environmentally reasonable management practices. The simple rule is that lethal control can never be justified without an effort to apply other controls to prevent the recurrence of problems.

>Exclusion: Mice can enter buildings through openings no larger than the size of a dime and can easily climb interior walls, making exclusion sometimes very difficult. Nonetheless, this procedure is the best and only effective way to permanently deal with mouse problems. The key to excluding mice from buildings is to conduct very thorough examinations of possible points of entry around foundations: where utility pipes and wires pass into the house, where siding has deteriorated and holes occur, cracks in foundations or any other places where an entryway might be suspected. Powder (either baby powder or talc) that is sprinkled along the inside perimeters of walls and thresholds will show tracks where mice are active and can be instrumental in helping decide where exclusion efforts are needed. Many different tools can be used to exclude mice from buildings. Wire mesh or quick-drying cement can plug cracks around drainpipes and small openings where mice may gain access. Galvanized window screening can be balled and stuffed into larger openings that are then finished with caulking or cement. The expanding-foam insulation sold in many hardware stores is excellent for filling small- to medium-sized openings and has the advantage of being available in commercial kits for larger jobs.

>Habitat Modification: The removal of food sources through proper sanitary techniques is essential. Because mice eat so little, attention should be paid to both obvious and not-so-obvious sources of food. A small amount of spillage from birdseed stored in a garage or shed can be more than enough to sustain a mouse. Dry pet food left in the garage overnight or next to an appliance behind which there is access from the wall will attract mice. Appliances also offer security from which foraging trips into the kitchen can be made to pick up the tiny amounts of spilled food that makes a meal. Household food items that are accessible to mice should be stored in metal or plastic containers. Removing weeds and trimming a vegetation-free perimeter for at least 18 inches out from the foundation of the house or building to be protected can eliminate protective cover. This procedure allows better recognition of entry points as well. Pets should be fed indoors and uneaten food picked up where mice are known to be a problem.

>Ultrasonic Devices: There are such devices commercially marketed, however, there are no credible scientific studies to validate the effectiveness of any such device.

Physical Appearance

The house mouse is all too familiar to most Coloradoans. These unsavory immigrants are the only mice many people know, and they have given all mice a bad name. The house mouse is just about what you’d expect a mouse to be – small (2 to 3 inches), gray-brown, with an almost naked tail as long or longer than its body. It is, of course, one of a variety of animals called “mice” and is often confused with native species such as white-footed and deer mice. Native mice often cause problems that house mice get blamed for, although the techniques for ensuring that mice do not invade the house apply equally to all these animals.

Habitat

House mice live mostly around buildings, moving into weedy fields and burrow pits in the summer and into buildings (homes, barns, and sheds) in the winter. The entire area occupied by a mouse during its lifetime may be less than the size of an average room.

Feeding Habits

Mice feed on stored grain, carrion, and just about anything in the pantry that is not canned or bottled. They require only about 1/10 ounce of food each day and, unlike rats, can live without access to fresh water if the solid food they eat is somewhat moist.

Mating & Breeding

House mice breed year-round and can raise as many as eight litters annually. Reproductive life begins for females at one and a half to two months of age. With an average of four to seven young per litter, the reproductive potential of these animals is considerable. Under the right conditions, mouse populations can grow almost explosively. The life of a mouse is short-lived; one year is about the longest any wild mouse could expect to survive.

Predators

House cats, owls, weasels, and spotted skunks are good mousers and should be encouraged in the task.

Public Health

Mice, like their larger cousins the Norway and roof rats, can carry a wide variety of diseases transmissible to humans. Hantavirus is an important public health concern that is present in both wild and domestic mice. This disease has not emerged as a serious concern yet, except in the arid southwestern part of the country. Salmonellosis can be transmitted by mice and is an important concern in food storage and preparation areas. The native white-footed mouse is an important host to the tick that causes Lyme disease.

- Information provided by the Colorado Division of Wildlife

- Information also provided by The Humane Society of the United States

Humane Society of U.S.| CO. Dept.of Health & Environment
Animal Control Home | Colorado Div. of Wildlife
Urban Wildlife Rescue | Table Mountain Animal Shelter