THE HOUSE MOUSE

The house mouse is the most commonly encountered and economically important of the commensal rodents. They are not only a nuisance, but they damage and destroy materials by gnawing, and eat and contaminate stored food. They are also of human health importance as carriers of disease. The adult house mouse has a head and body length of about 2 ½ – 3 ½ inches with its tail being an additional 2 ¾ - 4 inches long. It weighs from ½ - 3/4 ounce. It has a smooth fur coat that is usually dusty gray above and light gray to cream colored on the belly.

The house mouse has a pointed muzzle, small eyes and prominent ears. Its feet are short and broad. The tail is uniformly dark and semi-naked. Droppings of the house mouse are about 1/8 – ¼ inch long, rod shaped and have pointed ends. They can be distinguished from cockroach droppings because they lack the ridges which are prominent in cockroach droppings.

The house mouse is a prolific breeder. It can reach sexual maturity in 35 days.

Pregnancy lasts about 19 days. The young are blind and naked, except for vibrissae (long whiskers). They are weaned in about 3-4 weeks. Life expectancy is normally less than 1 year. The size of an average litter is 6 young, with the potential for about 8 litters per year. A female can have a litter about every 40-50 days. More than 1 litter may be present in the nest at the same time. Each female will average 30-35 weaned per year.

Mice have excellent senses, except for sight. They are color blind and can see clearly for only about 6 inches. They are excellent climbers and can run up walls which have rough surfaces. They are able to swim, but seldom do. They are able to jump about 12 inches high and can jump down about 8 feet without injury. They can survive in temperatures as low as 14F. They can run horizontally along pipes, ropes and wires.

A house mouse needs about 1/10 ounce of dry food per day and about 1/20 ounce of water (which is normally taken from the food source). It will produce about 50 droppings per day. Over a six month period, one pair of mice will eat about 4 pounds of food, produce about 18,000 droppings and excrete about 12 ounces of urine. The most common way they transmit disease is by contaminating food with their droppings and urine.

Mice are very social. Related males and females are compatible, but unrelated males are typically aggressive. They maintain a territory with the boundaries marked by urine. Territory size varies, but is usually very small. If food and water are plentiful, they may never venture more than 4-5 feet from their nests. Seldom will they travel more than 15 feet away. Mice are very inquisitive. They are likely to explore new things very quickly.

The house mouse is a nibbler. It eats only a small amount of food at any one time or place. They will eat many kinds of food, but prefer seeds. They feed mainly at dusk and just before dawn, but will nibble frequently in between. They sample new foods, but will return to old sources unless the new food is preferred. Required moisture is obtained from their food, but they will take free water when available, with a preference for sweetened water over plain water.

The house mouse prefers a nesting site that is dark, where there is abundant nesting material nearby and where there is little chance of disturbance. Nesting materials include paper products, cotton, packing materials, insulation, fabrics, etc. They will nest in almost any concealed space, such as walls, cabinets, furniture or stored products. They require an opening of ¼ inch to gain entry and are nocturnal in habit.