The house mouse probably originated around northern India and stowed away in grain supplies as people migrated around the world. It is now a worldwide pest and, in most cities, it is the top rodent pest. In addition to being transported to new areas as stowaways, house mice are able to enter smaller structural openings than rats and require very little living space. They also require less water than rats because, if necessary, they are able to meet their body’s moisture requirement by producing metabolic water from food. Once indoors and a food resource is established, they can breed throughout the year.