The Sheltie came from the Shetland Islands off Scotland. Unlike many miniature breeds that resemble their larger counterparts, this breed was not developed by selectively breeding the Rough Collie for smaller and smaller sizes. Rather, it is the result of the intermingling of possibly several breeds over the past several centuries.
Its exact origins are not known, but the most-often cited ancestors of the breed include the Border Collie (or its ancestors), the Yakki (also Yakkie or Yakkin) dog (a dog kept and bred by Greenland whalers, and the Icelandic sheepdog. During the 19th century, the appeal of small, fluffy dogs became clear, and there are mentions of cross-breedings with Pomeranians (which were larger then than they are today) and with the now-extinct (?) Prince Charles Spaniel or possibly a King Charles Spaniel. Some Shelties in the early 20th century had brindle coats, which could have come from a terrier or Corgi breed. Note: the "mentions" of cross-breedings with Pomeranians is largely seen as a myth by most Sheltie experts.
Shelties are known for their loyalty and obedience to their masters. They are friendly and affectionate, but reserved around strangers. Shetland Sheepdogs are wonderful learners.
Shelties have a double coat consisting of long guard hairs covering a fluffy insulative undercoat.
Several coat colors exist. There are three main acceptable show colors, sable (ranging from golden through mahogany), tricolor (black, white, and tan) and blue merle (grey, white, black, and tan). Bi-Blues (grey, black, and some white) and bi-blacks (white and black) are less common but still acceptable. The best-known color is the sable ("Lassie color"), although tricolor is also very common. Shelties can also come in red merle, color-headed white (mostly white with some color on the front half of the body), brindle and other colors. However, as these colors are faults in shows, they are quite rare.
In their size group, the breed dominates dog agility competitions.