Shetland sheepdog, breed of small, agile working dog perfected in the Shetland Islands in the 19th cent. It stands from 13 to 16 in. (33.0-40.6 cm) high at the shoulder and weighs about 15 lb (7 kg). Its double coat consists of a very dense, furry underlayer and a long, straight, harsh outercoat. It is usually colored a combination of black, blue merle, and sable, with white and tan markings. Although of obscure origin, the sheltie is probably a descendant of small specimens of the Scottish collie and the King Charles spaniel. It was developed to tend the diminutive sheep of the Shetland Islands, whose rugged, stormy shores have produced other small-statured animals such as the Shetland pony. Today it is raised as a farm dog and family pet. See dog.