Bert and I own that movie.
Although on our DVD box it says Le Pacte des Loups
(living in trilingual Belgium and all that)
I really love it, great story, great costumes, great effects, great acting.
I can't really say much about la bĂȘte as I've not done much research into the original legend, but my guess is that pretty much anything could have happened.
Big cat and extraordinary big wolf both sound plausible to me.