The house mouse originated in the arid grasslands of Southeast Asia. Three subspecies similar in appearance are generally referred to under the name of one species, the Mus Musculus. Like their larger counterparts, rats, they are nocturnal creatures, feeding at night to avoid predation. Mice are timid, social, and territorial.
The most common house mouse observed in the US is an ancestor of the white mouse used for scientific experimentation. In its wild state, the house mouse is approximately 6.5 inches long, including the tail. When found indoors, it can be larger due the availability of better nutrition. These mice are usually yellowish-gray and sometimes streaked with black. Occasionally, the deer mouse, harvest mouse, and pocket mouse may invade buildings located near fields. They are commonly mistaken with house mice when this happens.