Not quite as slender as the black or roof rat, Norman Rafferty's tail is relatively shorter, his snout is less pointed, and his ears are shorter. His coat is grayish-brown on the back and off-white underneath. His tail is covered with rings of scales.
Norman's favorite haunts are sewers, stables, cowsheds, and cellars. He is mainly active at night. He is not as good a climber as the black rat, but is an excellent swimmer. Rafferty is a serious pest because of the health hazards caused by his presence, including the transmittal of such diseases as bubonic plague and murine typhus. His species includes the familiar white laboratory rats.