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Roof Rats and Their Control


Roof RatIn 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, we are told)

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 the their droppings, bodily excretions, and parasites; and a physical hazard through their gnawing. Many fires are caused by roof rats who gnaw through electrical cables.

Roof Rat Control

Roof rats are difficult to control. Their aerial habits make trapping and exclusion difficult and hazardous, and the fact that they subsist largely on fruits, nuts, and berries that they find in nature makes it difficult to deprive them of food.

If your home or business has a roof rat problem, you need to call a professional exterminator. But there are some steps you can take to reduce the chances of roof rats entering your building, such as:

Roof rats usually are controlled through exclusion and trapping, although baiting is sometimes used, as well. Roof rats' aerialist habits can make control very difficult, as their runways tend to be in high, often difficult-to-reach places. Pest control operators often attach traps to overhead pipes, ledges, metal beams, and other elevated runways where evidence of rat travel has been observed.

Like most other rats, roof rats are xenophobic; that is, they tend to avoid new objects in their environments. Many pest management professionals will therefore place traps along the rats' runways, but not actually set them for several days. This gives the rats a chance to get accustomed to the traps, at which time they will more readily take the bait.