(Mus musculus musculus)
This species has a total length from 154-175 mm, and the weight is 13-30 grams. The color of the back is yellow-brown to gray-brown, and the belly is paler to white. The ears are naked, and the tail is not sharply bicolored, nearly naked. This species is capable of breeding throughout the year, and several litters of 3-10 young are born per year. The nest is a loose structure of rags, papers and grass. This species is colonial, and displays social dominance. It is nocturnal. They will consume anything organic although they prefer grain. They can be known by their spindle shaped droppings. This species is exotic introduced. Predators include owls, hawks, fox, coyotes, weasels, raccoons and cats. They are often used as a laboratory animal. They are a greater health hazard than the Norway rat since they are able to gain access to humans and their food storage areas.
This species is widespread along roadways but reaches high densities near granaries and barns. In the winter they inhabit barns or other buildings and in the summer they build their nests closer to food sources in the fields.
This species will eat anything, and prefers cereal grains and vegetables.