Breed of working dog developed in Great Britain, probably by the 18th century. The rough-coated variety was originally used to guard and herd sheep; the smooth-coated variety was used to drive livestock to market. Both varieties are lithe dogs with a tapering head, almond-shaped eyes, and erect ears that tip forward at the ends. They stand 22–26 in. (56–66 cm) tall, weigh 50–75 lb (23–34 kg), and may be variously coloured. See alsoborder collie.