There are several indicators determining whether your rats are gone. First, you will no longer hear their nocturnal activity — no more squeaking or loudly chewing on your household yummies. The second indicator requires some action on your side. Leave flour or cornstarch on the floor where you suspect rodent presence. If they are gone, they won’t leave their tail and paw traces on the powdered surface. You will no longer notice fresh rat grease marks or droppings if your filthy little enemies retreat.