Rare breed (dog) is any breed of dog that is small in number and is used to refer to both old established breeds such as the Stabyhoun and Glen of Imaal Terrier or newer creations. Since dogs have greater genetic variability than other domesticated animals the number of possible breeds is vast with new crosses constantly occurring, from these both selected and random crosses may come new breeds should offspring reliably breed true to type. New breeds from the wild such as the Carolina Dog are quite rare compared to attempts at breed creation from man as found in the American Hairless Terrier which sought to exploit a mutation.
Modern dog breeds have documented descent from known foundation stock, and new breeds are often derived from older, established modern breeds. New documentation of a long established dog type, sometimes with a variation on an older name, also creates a new modern breed. The newly documented breed is then referred to as a rare breed as long as the number of dogs of the breed remain small.
Breeds go through a recognition process by breed clubs, kennel clubs and other agencies, so that dogs can be guaranteed through written documentation to be a member of a specific breed. For example, the Canadian department of agriculture, Agriculture and Agri-Food Canada, has strict requirements for the registering of new breeds, which are referred to as "emerging breeds." In the past, this process was limited to each country's national governing body for dog breeds (two in the case of the United States), and gaining recognition for a new breed was a closely checked, long process. With the advent of the internet a vast number of minor registries has proliferated, allowing clubs, breeders, and internet entrepreneurs to create their own registries for their own purposes. As a result, the number of dogs being marketed as or referred to as registered members of a rare breed has increased.
note 1. ^ See the Biewer for an example of a new modern rare breed derived from an established modern breed, in this case, the Yorkshire Terrier.