The head and body of the house mouse measure 7 to 10 centimetres, and its tail another 5 to 10 centimetres. It weighs between 10 and 35 grams and has a life expectancy of about three years. It has a pointed muzzle, small eyes, big ears, and greyish-brown fur that is lighter below.
The house mouse lives close to humans in houses, barns and other buildings, and as a result of human activity has spread to all continents with the exception of Antarctica.
The house mouse is omnivorous, eating seeds, the green parts of grass and plants, and human food waste. One female may give birth five times a year to between three and eight young each time, and mice can give birth at six weeks of age. Mice are mainly nocturnal. They can pass through holes just three centimetres in diameter and are good at climbing and jumping. They live in big family groups. Signs of their presence include damage to paper and cables, a distinct smell and solid droppings about 6 millimetres long. Mice sleep in well-hidden nests.