I missed the original post from the person asking about sign language,
but here's my personal experience:
 
My mate used to have a rabbit, while I had/have the ferrets (the rabbit,
thankfully is long gone, I do still have my mate, tho, haha).
 
Our old upstairs neighbor was deaf.  I learned very little ASL from him,
but I did once ask him just this very thing.  He showed me that 'bunny or
'rabbit' is the left arm held like in a sling, and with the two fingers
of the right hand upraised (like a peace sign) and curved, and 'hop' it
up your arm...
 
 ..while 'ferret' was with the left arm held the same way, but the entire
right hand held above the arm with the fingers slightly cupped (almost a
'c' shape) facing more down towards the arm, and more 'undulate' it up
the arm, more like a slinky ferret bouncing motion.  Does that make
sense?
 
That's my best description of it!  :-X
 
daoine o', aka the ferret queen
Razzle, Monty-boo, and Jezebel
~still missing Dweezil, my one small star~
[Posted in FML issue 4800]