They almost always require a nonfood or separate source of water. As often as possible, they follow vertical surfaces which their vibrissae or long whiskers can contact. Runways along vertical surfaces will usually include dark nub marks on the vertical surfaces where their oily fur makes contact. Their runway will be free of debris, and outdoors, the grass will be worn away to the bare soil. The key to any rat control program is pest identification, sanitation, harborage elimination, and rat proofing the building.
Control is based on the behavioral habits of the Norway rat.
Rats defecate somewhat indiscriminately within their territories but mostly where they feed. Look for rub marks and clean runways. Place traps or bait stations along runways and against vertical surfaces.