Common mammalian pests. Most of the common mammalian pests are members of the rodent family. Probably the two most iconic pests are closely related: Mice and rats. Mice are found just about everywhere, and frequently invade homes, offices and garages. Rats are especially found in urban settings, and are larger, more destructive versions of mice. Both of them breed extremely rapidly, can survive on any of a wide variety of foods, and can squeeze into narrow passageways, holes and crevices. Another rodent often causing problems in human environments is the squirrel. Squirrels have a tendency to invade attics and other high reaches in homes and buildings. They are prone to chewing through wires and causing other damage. Bats are another mammal species that can potentially cause problems, though not with the frequency of mice, rats or squirrels.