breed of herding dog developed in the 19th century to work with cattle in the demanding conditions of the Australian outback. It is called a heeler because it moves cattle by nipping at their feet; this trait was introduced to the breed from the dingo in its ancestry. An active, sturdy dog of medium size, it has prick ears, stands 17 to 20 inches (43 to 51 cm), and weighs 35 to 45 pounds (16 to 20 kg). Its short, dense double coat is either red speckle, with darker red markings on the head, or blue, often with speckling or mottling, and often with markings in blue, tan, or black on the head; in blue dogs tan also appears on the lower legs, chest and throat, and face. Pups are born white with facial markings and develop their basic coloration as they grow. The breed has been listed by the American Kennel Club since 1980. Although a tough, hardworking breed and a good watchdog, the Australian cattle dog is a faithful companion and is good with children. It excels at dog sports such as agility competition.