Rats can transmit a lot of different diseases and their nesting and feeding habits can compromise the structure in which they have taken up residency. They are also a secretive animal which can make it difficult to identify if there is an infestation problem. It is necessary to call in a professional to aid in the diagnosis of a problem.
A professional will be able to handle the problem effectively. A homeowner could set traps, but rats are smart and are wary of unfamiliar things that are introduced into their environment. A professional will also know the different signs to look for if there is an infestation.
Rats will leave behind obvious and not so obvious signs if they have moved in. The most obvious sign is the sighting of a live or dead animal. If seen in the open, this can be a sign that a full infestation has already occurred because their secretive nature will push them into the open because space is limited. They also leave behind grease, dirt, and droppings along their established routes. These routes are loyally used by rats and will show signs of their presence. They also gnaw incessantly, and there will be evidence of their gnawing around the home or structure.