A mouse is a small mammal. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse. Mice are also popular as pets. In some places, certain kinds of field mice are locally common. They are known to invade homes for food and shelter. Mice are typically distinguished from rats by their size. Generally, when a muroid rodent is discovered, its common name includes the term mouse if it is smaller, or rat if it is larger. The common terms rat and mouse are not taxonomically specific. Typical mice are classified in the genus Mus, but the term mouse is not confined to members of Mus and can also apply to species from other genera such as the deer mouse, Peromyscus. Domestic mice sold as pets often differ substantially in size from the common house mouse. This is attributable to breeding and different conditions in the wild.