Rats are responsible for the transmission of many diseases. Their feeding habits are destructive, and their nesting behaviors can compromise the structure of infested buildings. However, rats are secretive and not seen by humans when populations are low. Therefore, an infestation may prove difficult to confirm.
The most obvious sign of a rat infestation is the presence of dead or living rats. Rats prefer to hide, given enough space, so if rats are observed in plain sight, it is likely that a full-blown infestation already exists. When space becomes limited due to increased population, rats are forced out into the open. Rat droppings may be present, indicating a healthy, feeding rat population. Rats also tend to leave dirt or grease marks along walls and floorboards.
If these obvious signs are not present, examine the surroundings for rat runs. These tracks are left in grass and low vegetation and act as foraging paths for rodents. Rats tend to follow the same paths after they have been established. Norway rats dwell in burrows found in grassy embankments, beneath the roots of trees and at the edges of paving and drain covers. Roof rat nests may also be found inside in lofts, attics, beneath floorboards and in other dark, infrequently visited locations.
Rats gnaw incessantly on materials such as plastic and wood. The presence of damaged materials and large holes in floorboards and walls are sure signs of infestation. Rat teeth marks are large and rough in appearance.
In the event of an infestation, it is best to consult a pest control professional. Although various traps are available, they address only individual specimens and will not prove effective in the face of an infestation. Additionally, rats tend to be wary of unknown objects in their established foraging paths, rendering many traps initially ineffective.