On the topic for "insurance for ferrets", I would recommend against it.
 
Try this instead.  Put some extra money in the bank, specifically for
ferret emergencies.  I think $400-$500 per ferret would cover pretty much
anything that could possibly go wrong with a ferret that wouldn't be too
horrible to contemplate.  Besides, then the money works to your advantage
and not to an insurance companies'.  Chances are, you'll use a few hundred
dollars over the ferret's lifespan for real big medical emergencies.  Maybe
a vet can suggest a more accurate price..???
 
I.M.H.O...., Mark Hei
[Posted in FML issue 2334]