User blog comment:Godechaud/Questions raised with the start of Season 3/@comment-12377174-20130723055534/@comment-8038513-20130723214441

that wasn't full alpha form. Gerard said she was able to shift into an actual wolf and that it was a rare ability. meaning Derek's sister Laura from season 1 probably inherited the ability from their mom.

my guess is that there is no full alpha form, and that peter was only able to shift into "The Alpha" because his mind was so traumatized and was more of a animals mind than a mans.