I have a 6 year old black sable female named Molly.  I also had a male.
Molly is anything but stressed.  Potsy died last year from a tumor in his
chest that could not be removed.
 
Are you sure it isn't you stressing them out?  I am not accusing you, I
just know ferrets can pick up on human feelings.  Some more sensitive
than others.  Is he your only ferret?  If not, does he get along with
the others?  Is he a Marshall or breeder ferret?
 
Jackie
[Posted in FML issue 4464]