Barbara, whatever the cause of your ferret's tendency to bite cords, I have
a suggestion for you that is different.  Since he has bitten through one and
you have many others around in accessible areas, you need to reduce the risk
of a 2nd lapse of training.  Get yourself a Ground Fault Circuit
Interrupter(s) for the circuit(s) involved.
 
There are 2 types.  One replaces the ordinary circuit breaker and protects
the whole circuit.  This requires an electrician to install, unless you
really know what you're doing, and becomes part of the house (I assume you
rent).  Or you can get the plug type that replaces a receptacle.  These can
be wired to protect that outlet only or the rest of the downstream circuit.
With luck everything is on one circuit and you can protect the whole thing
for about $15.  This takes a little knowledge to install but is not hard.
Be sure and test other downstream plugs after installed.
 
This device will kill the power within microseconds of a bite that causes
contact with wires.  No more singed ferret and it requires a manual reset so
you will know another incident has taken place.  Given the potential for
another bite and the many cords around, you might want this as a safety net
for your other measures.  Of course, feed him right and all your problems
will go away.  He's not bored or curious, he craves PVC.  In the wild he'd
be hunting naugas.
 
   ( )--(a)
   (@=@=) \     Till next time.......Rudy the ferlosopher
   O__)  \ \___
      \   \
      /\ * )  \
[Posted in FML issue 1484]