One of my chubbier girl ferrets got stuck one day and panicked.  It shut
off her breath and by the time I got her she was barely breathing.  She
would have died if I hadn't been right there.  We now have a rule that
they can only play in the tunnel when one of us is observing.  The rest
of the time it is put in a separate room with the door closed.
 
Laurel
[Posted in FML issue 4261]