Dewclaw

A dewclaw is a digit – vestigial in some animals – on the foot of many mammals, birds, and reptiles (including some extinct orders, like certain theropods).

It commonly grows higher on the leg than the rest of the foot, such that in digitigrade or unguligrade species, it does not make contact with the ground when the animal is standing.

[1] On dogs and cats, the dewclaws are on the inside of the front legs, similarly to a human's thumb, which shares evolutionary homology.

For certain dog breeds, a dewclaw is considered a necessity, e.g., a Beauceron for sheep herding and for navigating snowy terrain.

[1][8] The argument for removal states that dewclaws are a weak digit, barely attached to the leg, and thus they can rip partway off or easily catch on something and break, which can be painful and prone to infection.

Many dogs cannot resist licking the surgery site in the weeks following the procedure, so an Elizabethan collar or bitterant may be used to curtail this behavior, thus preventing infection.

[citation needed] Some pups are commonly sold by breeders "dew-clawed", that is with the dewclaws removed (as by a veterinarian) for perceived health and safety reasons.

Based on stop-action photographs, veterinarian M. Christine Zink of Johns Hopkins University believes that the entire front foot, including the dewclaws, contacts the ground while running.

If the dewclaw does suffer a traumatic injury, the problem can be dealt with at that time, including amputation if needed.