House mice (Mus musculus) are brown to black with a lighter, but not white, underbelly. They are smaller than rats (2 to 3.5 inch long body with 3 to 4 inch long tail) but similar in appearance. Young rats are sometimes mistaken for mice. House mice are seen both indoors and in agricultural areas.

House mice eat a variety of plant matter and are attracted by bird seed, pet food, cereals and grains, and garbage. They readily infest homes, grain silos, barns, and other occupied, man-made structures. They are dependent on humans for shelter and food and their survival rate in remote, wild habitats is low. Because they are very small, they are difficult to keep out of structures and may not be discovered right away. They are nocturnal but may be active during the day if disturbed.

House mice have 5-10 litters per year with an average of 5-6 offspring per litter. Young house mice are able to reproduce when about 5-7 weeks old. Their maximum lifespan is 2 years, but they typically live 12-18 months in the wild. House mice have been domesticated and are used in biological research and kept as pets.

House mice may contribute to the spread of rat-borne diseases but are a major cause of food spoilage and damage to homes. Gnawing damage on wiring is a major cause of house fires.

It is believed that house mice may have originated in the Mediterranean region of North Africa and the Middle East. They have since been spread throughout the world by humans.

Page last reviewed: December 28, 2023