Dewclaws are fifth toes on either front or rear legs. They emerge along the side of the lower leg and do not touch the ground when the dog is in a normal stance. Double rear dewclaws are required in some breeds. Sometimes a dog may have triple rear dewclaws. Multiple front dewclaws are abnormal. Rear dewclaws are abnormal for members of the dog family in general (wolves, foxes, etc.), but do occur in domestic dogs. Whether they are “normal’ or not depends on the breed. They are not normal in Aussies. All Aussies have front dewclaws. There are no statistics on rear dewclaws, but they don’t appear common. However, they obviously occur often enough – or at least did historically – for them to merit mention requiring removal in most breed standards.
Front dewclaws are allowed to be removed per most breed standards, but shouldn’t be for functional reasons and there are many Northern European countries where it isn’t allowed at all. Rear dewclaws, remnants of the first toe, are virtually always non-functional and should be removed in breeds where they aren’t required (including Aussies.) Rear dewclaws typically do not attach to the other bones in the rear legs. They are encased in flaps of skin that protrude from the leg and lack continuity with the remainder of the skeleton. In field conditions they may snag on things and tear.
In rare instances, dogs may have functional rear dewclaws. The Norwegian Lundehund breed has one or two functioning rear dewclaws. There are reports of functioning rear dewclaws with skeletal and muscular attachment to the leg in Aussies, though these are rare. They may be inherited and should be considered faulty but because they are integrated into the musculoskeletal structure of the rear leg they shouldn’t be removed without medical cause.
People remove front dewclaws for easier grooming or to make the front leg look smoother; some feel it presents an unnecessary risk of injury to dogs working in rough terrain. The breed standards allow it but there is compelling reason not to remove them. The front dewclaws are equivalent to our thumbs. Even though these toes don’t reach the ground when a dog is standing or trotting, they are functional, stabilizing the carpal (wrist) joint, especially when moving at speed or making sharp turns. They are used for self-grooming and to help steady objects a dog may hold between its forepaws when lying down. All but one wild dog species (the African Wild Dog or Painted Wolf) have front dewclaws, including all those most closely related to domestic dogs.
Removing front dewclaws can impact health: Physically active dogs which have had the front dewclaws removed are prone to developing arthritis at the carpal joint, sometimes sufficiently severe and early to end a performance event or working career.