A werewolf turns to beast form under the gaze of the full moon and the two days on either side when the moon is just off full. In this form they no longer remember there human selves, they would cut down there best friend if he crossed there path.

Those that can control there shifting are called skinwalkers, they maintain total control over there form while in beast form, this is also spread through biting. The shape there beast form takes will be based upon there personality and body type but it will always be some sort of canine.

Hope that helps.