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. As with dogs from other working breeds, the Australian Cattle Dog is energetic and intelligent with an independent streak. It responds well to structured training, particularly if it is interesting and challenging. It was originally bred to herd by biting, and is known to nip running children. The most common health problems are deafness and progressive blindness (both hereditary conditions) and accidental injury; otherwise, it is a robust breed with a lifespan of 12 to 14 years. The mask consists of a black patch over one or both eyes (for the blue coat colour) or a red patch over one or both eyes (for the red coat colour). It remains, however, that Australian Cattle Dogs generally age well and appear to live on average almost a year longer than most dogs of other breeds in the same weight class.