When I was about 12, our family dog — Louie — ended up somehow catching his dewclaw in a metal piece of his collar and tearing the nail. Poor pup had to wear a cast while it healed, which wasn’t fun for anyone.

At the time, I ignored the the fact that I had no idea what purpose a dewclaw served, but now I find myself wondering what this mysterious nubbin is all about.

Turns out that the dewclaw is a perfectly normal vestigial digit found on the “ankles” and “wrists” of many mammals (such as dogs and cats), reptiles and birds. While dewclaws are considered vestigial, they are not useless — many animals use them to help grip bones or toys, for example.

This extra digit (not to be confused with animals who are polydactyl) appears higher up on the limb than normal toes and usually won’t make contact with the ground when an animal walks. For companion animals, this means that owners need to be careful about keeping dewclaws trimmed so that they don’t catch on anything or end up growing back in to the pad of the foot. (In retrospect, surely a too-long dewclaw contributed to Louie’s accident).

Most dewclaws are attached and don’t need any kind of special attention other than regular trimming. Occasionally they are only be partially attached, however, and in some cases vets will recommend surgical removal of the dewclaw to prevent painful tearing or infection.

(Image: SuperStupid)