Two of my critters will also make the hissing sound.  I forget who did it
first, but they've been doing it for several months now.  Luna will hiss at
mommy when I scold her, usually if I scruff her when I'm doing it. :)  She's
scolding me back.  Clover hisses a lot, usually when he's playing.  We have
a furry toy that hangs down from an elastic string, and he loves to play
with it, trying to hide it under the couch.  It always gets away from him
and snaps back, and he'll run, grab it, hiss at it (to scold it for running
away?), and try to hide it again.  He's also hissed at the new baby a few
times, if he's trying to eat and the baby's biting.  So I think it's just a
normal fuzzy noise.  I personally think it's kind of funny, especially when
Clover hisses at his toys.  I also saw him wag his tail once, and I was
hysterical, as I've never seen a fuzzy do that.  Just thought I'd add my .02
worth.
 
Kristi and the Mustelid Mob of Mayhem
        Mayonnaise, Clover, Luna, and new baby Loki
 
ferrets are like potato chips...you can't have just one!
[Posted in FML issue 2285]