Skinwalkers

Skinwalkers are supernatural creatures that were encountered by the The Winchester Family and other Hunters. Little is known about Skinwalkers accept that they are similiar to black Dogs, wendigo (Creature), and Werewolves. Dean Winchester after reading John Winchester's journal references them as the cousins of werewolves. Much like their supernatural cousins they transform into animals. They can shift from human form into dog form whenever they want.

All skinwalkers originate from an Alpha.

Transformation
Skinwalkers transform back in forth from human form and dog form whenever they want. Unlike their cousins, the werewolves they have complete control of their actions when are transformed and do not depend on the lunar cycle to transform. They usually tranform into a dog to escape.

Enhanced Smelling
They can smell a scent far better than a human. Using this ability they could tell if they are being folled. They could use this ability in either form.

Accelerated Healing
They appear to be able to heal themselves faster than humans. A skinwalker was hit by a minivan, when he returned back to human form he appeared to have no physical harm. The same skinwalker was shot with a bullet. He healed from the wound extremely quickly.