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Roof Rats

Summary: Roof rats can be a persistent pest requiring a lot of detailed exclusion work to keep them out of structures. This article will provide some good tips on how to fight Roof rat invasions.

Roof rats (Rattus rattus Linnaeus) have made their way into and around houses since time began. Its name is derived from the way it prefers to enter properties via the roof area. In earlier times Roof rats arrived in the U.S. from Europe and Southeast Asia by ships, so it is also known as a Ship rat. Yet another name for the Roof rat is the Black rat because one of its sub-species is black, except for its gray belly.

Found in many parts of the United States, the Roof rat nests in high places, both outside and inside. However, as its population expands it may extend its nesting area to include locations closer to the ground like ground floor levels inside and outside of buildings and piles of various materials.

The Roof rat lives mostly in warmer climates of the United States in the Southeast, some Gulf States as well as the Pacific Coast states. It is even found as far west as Hawaii.

To identify a Roof rat, as opposed to its near relative, the Norway rat, look for a scaly, hairless tail that is longer than their 6-8 inch black. Body fur will be brown or gray with lighter gray, brown or white bellies. They weigh around 5 to 8 ounces, whereas the Norway rat is larger, tipping the scales at as much as 19 to 21 ounces.

Like the Norway rat, Roof rats have a spring and summer breeding season with litters 4 to 6 times per year bearing, on average, 4 to 6 pups and gestation periods of approximately 21 to 23 days. The average life span is around one year.

Roof rats may be heard moving around in the attic. It is possible to locate them by discovering their gnawing damages to utility wire insulation or plastic items inside the house. Of course, rodent droppings are also a giveaway. They are active mostly in the cooler fall and winter months.

Although the time old tale is that rats like to dine on cheese, the fact is that Roof rats eat whatever is available and convenient including vegetation, nuts and fruits in their natural outside environment. Once inside a home, such items as pet foods, cereal products and other food items can be found on its dining menu.

Like most rats, the Roof rat usually stays close to its nest when out hunting for food, usually within around 200 feet or so. Because its vision is one of its less developed senses, Roof rats travel closely along walls at night by using its whiskers, body guard hairs and nose to touch and smell its way around in its efforts to locate its preferred food.

So, how best are Roof rats prevented from entering in the first place, then controlled once in the house?

  • Prune and remove vines, trees and other vegetation that allow access to and from roofs and attics.
  • Place and maintain obstacle guards on utility lines and fences where lines attach to or run nearby your residence.
  • Repair cracks or other openings that make it possible for rats to get in.
  • Trap rodents with various types of traps.
  • Bait with rodenticide baits as specified by the label instructions and conditions of use.

Add to that a determined and persistent practice of locating, altering and eradicating rodent nesting to discourage them from living inside or nearby your house.

I do not recommend shooting or relying upon predators such as cats and owls. Nor do I recommend the use of glue boards, tracking powders or fumigants since roof rats seldom burrow. When all else fails, call in the pros.

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