Facts

The house mouse is remarkably well-adapted for living year-round in homes, food establishments and other structures. Homeowners are especially likely to notice mice during winter, following their fall migration indoors in search of warmth, food and shelter. Once mice become established inside a home, they can be extremely difficult to control.

Mice originated in Asia and spread through Europe many centuries ago. In the 1500s, mice arrived on the ships of the explorers in what is now Florida and Latin America. They quickly spread to the northern shores of North America along with the English and French explorers, traders and colonists.

Although most people consider mice less objectionable than rats, mice are more common and cause significantly more damage. Mice are prolific breeders, producing six to ten litters continuously throughout the year. The greatest economic loss from mice is not due to how much they eat, but what must be thrown out because of damage or contamination. Food, clothing, furniture, books and many other household items are contaminated by their droppings and urine, or damaged by their gnawing. House mice gnaw through electrical wiring causing fires and failure of freezers, clothes dryers and other appliances. Mice also can transmit diseases, most notably salmonellosis (bacterial food poisoning) when food is contaminated with infected rodent feces. Other diseases include rickettsialpox, lymphocytic choriomenigitis, leptospirisis, ratbite fever, tularemia, Lyme disease and dermatitis caused by the bites of mites from the mice. Hantavirus (pulmonary syndrome) is another danger becoming more common.

Mice are nocturnal creatures and are rarely seen by the homeowner. The most obvious indicators of their presence are droppings (1/8 to 1.2 inches long, dark and pointed at both ends), sounds of them running, gnawing or squeaking, or damage to stored food or materials for nesting. Highly curious, mice explore their territory daily, paying special attention to new items or physical changes in their home range. Unlike rats, mice show no aversion to new objects.

Compared to rats, mice forage only short distances from their nest, usually not more than 10 to 25 feet. When food and shelter are adequate, their foraging range may be only a few feet. For this reason, traps and other control devices must be placed in areas where mouse activity is most apparent. Mice prefer to travel adjacent to walls and other edges- another critical point to remember when positioning control devices. Mice seem to prefer cereal grains and seeds in their feeding. They are sporadic in their feeding, particularly when there are many food sources available. In these situations, mice may make 20 to 30 visits to different food sites each night, taking as little as 0.15 gram of food at each site. Sites may vary from night to night, but certain sites where the mouse feels safe are nightly favorites. When food sources are limited, mice may visit the source 200 or more times per night, but only 20 milligrams may be taken during each visit. In all, the average mouse will consume only 3 to 4 grams or about 1/10th of an ounce, of food per night.

Signs

- Mice constantly leave droppings in the areas they frequent. Approximately 1/8 to 1/4 inch in length, fresh droppings are dark in color and soft in texture. As they age, droppings become hard and brittle.

- Mice travel the same runway time and time again, leaving a smudge mark - a buildup of dirt and oil from their fur - along walls, pipes and holes.

- Footprints and tail drags can sometimes be seen is dusty locations. Non-toxic tracking dust such as talc or flour has proven helpful in determining the presence and location of mice.

- Mice can chew through anything that is softer than their teeth, so gnaw marks are a sure sign of mice. On wood, the darker the wood, the older the gnaw marks are.

- If your dog or cat unexplainably gets excited, it is more than likely that mice are moving about.

- The sound of mice gnawing, squeaking, or running through the walls or ceiling is occasionally the only sign of their presence.

- Favorite nesting materials of shredded paper, insulation material and string are often found in attics and garages.