Like Norway and black rats, the house mouse is an Old World species inadvertently brought to North America by European settlers. It inhabits Pennsylvania statewide, living in and near houses and on farms. Six to 8 inches long, it has a 3-inch, scaly, nearly hairless tail; its weight is ½ - 1 ounce. House mice come in various shades of gray. Omniverous, they eat everything from grain and seeds (their preferred foods) to paper, glue and household soap. Mus musculus is agile and quick, able to run at eight miles per hour. An adult female produces 5-8 litters annually, each with an average of 5–7 young. The species is active the year around.