The Norway rat, Rattus norvegicus, is not native to North America, but rather to the Old World. Much like the black rat, the Norway rat was accidentally introduced to many areas of the world when it escaped from ships at port. The Norway rat now occurs in many North American cities, where it is common near buildings, farms, and dumps. The Norway rat is a public health threat, as well as an agricultural menace.
The Norway rat will eat any food items available, including plant material, animal material, carrion, and garbage. The species is very prolific; mating occurs year-round, and females can produce up to twelve litters of two to fourteen young each year. Norway rats are primarily nocturnal. Unlike Utah's native woodrats, Norway rats have scaly (hairless) tails.