The House Mouse is the most commonly encountered and economically important of the commensal rodents, the Norway and roof/black rats being the other two. House mice are not only a nuisance, damage and destroy materials by gnawing, eat and contaminate stored food, they are also of human health importance as disease carriers or vectors. It is thought to be of Central Asian origin, but is now of worldwide distribution and found throughout the United States.
The Norway, or Brown, Rat is the largest of the commensal rodents and lives both as a commensal in close association with man and in the feral state, chiefly where vegetation is tall and rank and affords adequate protection. They feed on a variety of items including both plant and animal materials. All sorts of garbage appear to be welcome, but their main stay is plant material. Grains of various sorts are highly prized. When established around poultry houses, they feed extensively on eggs and young chickens. They even have been known to kill lambs and young pigs!