I have had varying experiences with my ferrets and Kong chew toys.  I had
a ferret who dearly loved Kong chew toys, and carried them around and hid
them in his favorite spots.  Close daily inspections showed no wearing or
chewing of the rubber.
 
Then I had the opportunity to foster a couple of ferrets.  Since they came
with few toys of their own, and one seemed to chew everything in site, I
left a Kong toy in their cage overnight.  The next day I noticed the top
rubber piece had been chewed off.  The Kong toy came out of the cage and
away from this ferret.  I did try another Kong as the other one was older,
but this ferret could get his teeth into the tiny top hole, and keep
chewing until it ripped.  Guess Kong needs to make a super Kong for this
ferret!
 
It was the top portion that seemed to slightly extend out that was always
being chewed and broken off, so be vary wary of this part.  As with all
toys, keep an eye on ferret and toy.
 
Masked Ferret owner in CA
[Posted in FML issue 3214]