The Australian Cattle Dog (ACD), or simply Cattle Dog, is a breed of herding dog originally developed in Australia for droving cattle over long distances across rough terrain. It is a medium-sized, short-coated dog that occurs in two main colour forms. It has either brown or black hair distributed fairly evenly through a white coat, which gives the appearance of a "red" or "blue" dog. That's why the breed is also called Blue Heeler or Red Heeler. Queensland Heeler is another name for the breed.