Some are pure gray some pure black, or any combination of the above. They explore their territory of 1-300 feet daily. They have neophobia, or new object fear, which makes them cautious, and any new object in their territory will take them several days before they will accept it. They like mice are color blind, and see poorly. Their sense of smell and touch however are acute.
Rats often live in basements or any dark area, or burrow under ground often under front stoops.
They are nocturnal feeders. Young Norway rats are capable of mating at three months. After giving birth, the female goes back into heat in twenty four hours. Adults live approximately one year. To keep rodents out of a structure, exclusion is always the first and most important step.