The House Mouse is the most commonly encountered commensal rodent. They are not only a nuisance, damaging materials by gnawing, but they eat and contaminate stored food, making them an important health concern as well.
The House Mouse is thought to be of Central Asian origin, but they are now found worldwide. Adult Mice are usually between 2 1/2” and 3 1/2” long, not counting the tail. Mouse fur is smooth and usually a dusty gray color, with the exception of their light colored belly, but fur color can vary greatly from location to location. Mice have pointed muzzles, small eyes, large ears and little hair on their tail. Mouse droppings are between 1/8” and 1/4” long with pointed ends.
The House Mouse is a prolific breeder, they can begin reproducing at just 35 days old. The young are born blind and take about 3-4 weeks to be weaned. House Mice have an average of 6 young per litter, two thirds are usually female, and they can have up to 8 litters per year and each pregnancy lasts just under three weeks. Life expectancy for House Mice is less than 1 year, but they have been known to live up to 6 years.
Mice are colorblind and cannot see clearly beyond 6”, but they have exceptional senses of smell, taste and hearing, even sensing vibrations with their whiskers, all to make up for their very poor eyesight. Mice are excellent climbers, they can run up most roughened walls, can jump up to 12” high and can jump down from about 8 feet high without injury. Mice can swim, but generally prefer not to. They can survive and even thrive in cold storage facilities down to 14°F.
A single House Mouse requires about 1/10oz of food and about 1/20oz of water (usually obtained from their food) per day and will produce about 50 droppings per day. Over a 6-month period a pair of mice will eat about 4 pounds of food and produce about 18,000 droppings and 12oz urine. The most common way Mice transmit disease organisms is by contaminating food with their droppings and urine.
Mice are very social animals, so related males and females are compatible, but unrelated Mice are typically very aggressive toward one another. Territory size varies, but if food and shelter are plentiful, Mice may not travel more than 4-5 feet from their nests. New adults will explore far greater distances to find new nesting territory. Mice are inquisitive, they will explore anything new or changed on their daily territorial patrols, and will establish new travel routes if necessary. Mice are nibblers, eating only small amounts at any one time or place, often sampling new foods, but then returning to their favorites.
The key to Mouse control is exclusion, or “mouse-proofing” the home. This is often the most difficult portion because adult Mice need an opening only slightly larger than 1/4” in diameter to gain entry. Careful inspection of the exterior of the house is necessary, checking door thresholds and foundation vents, as well as any opening around pipes or wires, to to ensure all entry points are properly sealed. In addition to the exclusion, proper baiting is needed to eliminate the remaining Mice inside the house.