Norwegian Water Rats

Despite its name, the Norwegian water rat, also known as the brown rat or sewer rat is more commonly called the Norway rat. This rat is not native to Norway. Rather, these rodents originated in Asia and were introduced via trade routes to Europe and finally to the Americas in the 1700s. Although initially native to forest and brushy habitats, Norway rats now live in close contact with humans. They may inhabit dumps, sewers, open fields, woodlands, basements or barns. Norway rats can enter human homes through an opening as small as 12 mm.

Norway rats are sometimes mistaken for another species called the roof rat. The roof rat is smaller and lighter than the Norway rat. The tail of the roof rat is longer than its body, while the tail of the Norway rat is shorter than its body.