That's the sure sign that a spriggan is behind them. Even so, I had a fox attack me once on a road near Riften, and it was just an ordinary fox. I've had two deer attack me at once in the wide open spaces west of Whiterun. I've never, ever heard of a spriggan speaking. I've freed a hagraven from a cage at her request, but that was part of a quest trigger. I did see a pair of spriggans in the snow fields west of Winterhold. That was astounding... not a tree in sight. BTW, have you noticed that a dead spriggan is dull in daylight, but glows in the dark?
I did not know that about the spriggan. Maybe I just haven't seen a dead one at night yet.

