I think those are just the random "finishing move" animations for werewolf form, same as you get for any weapon. They happen randomly when you get a killing blow.
Weird, because sometimes I get random killing blows when the enemy has full health, yet another of the exact same enemy takes like 6-7 sword/claw swipes to kill.
Oh well.
Edit: Another question. When is it optimal to go werewolf over regular self?
Last edited by Silverraptor; 2012-02-22 at 03:31 PM.