In your case with the wolf, well lets just say thats a rare thing that happened because you didnt know wolf could die from Drake. If you see drake, kill drake. Ive had 2 star wolves out in the open and the dragons or drake hone in on one or 2 and they do get killed unless I take them out before wolves die, then I have to make sure they eat, their health wont go back up until they eat.
FWI, I keep 2 Wolves that are 2 stars in side my castle under cover, separated, one on each end of castle.