In the United States, Roof rats (Rattus rattus) are found mainly along the southern Atlantic and Gulf coastal States, along the Pacific coast from California north to the Canadian border, and in Hawaii. Occasionally, they also are accidentally transported to non-native areas where they may or may not survive and become established.

(Roof rats are sometimes called tree rats in some parts of the United States, and our friends in the United Kingdom call them black rats.)

Biology of Roof Rats

Roof rats are more slender and agile than Norway rats and may be gray, brown, black, or of mixed colors. (The older distinctions that divided roof rats into several subspecies based largely on color are no longer used, as interbreeding has rendered those distinctions irrelevant.

In nature, roof rats are tree-dwellers (although they will occasionally nest on the ground under piles of debris, in stacks of firewood, in abandoned vehicles, and in other protected places). They are accomplished aerialists and are quite adept at running along utility lines, tree branches, and tree limbs. Like squirrels, roof rats can enter buildings through soffits, attic and roof vents, and other openings, often starting with a small opening and gnawing it to suit their liking.

Once in a building, they create a health hazard with their droppings, bodily excretions, and parasites; and a physical hazard through their gnawing. Many fires are caused by roof rats that gnaw through electrical cables.