In the United States, tails are sometimes docked on working stock. The tail is not docked in Australia, and serves a useful purpose in increasing agility and the ability to turn quickly. The Australian Cattle Dog is a breed distinct from the Australian Stumpy Tail Cattle Dog, a square-bodied dog born with a naturally 'bobbed' tail. The Stumpy Tail resembles the Australian Cattle Dog, but has a taller, leaner conformation. Descendants of these dogs still exist, but are useful only over short distances and for yard work with domesticated cattle. Thomas Hall addressed the problem by importing several of the dogs used by drovers in Northumberland, his parents' home county. At that time dogs were generally described by their job, regardless of whether they constituted a breed as it is currently understood. In the manner of the time, the Hall family historian, A. J. Howard, gave these blue mottled dogs a name: Northumberland Blue Merle Drovers Dog.