I don't know your home situation, but will tell you a few things about our
ferrets.  Once in awhile when two ferrets play rough together, one will
shiver.
 
This could be from fear, being scared or who knows what.  When I separate
two playing rough IMO, one will start to shiver.  This is known because I
spend time watching the ferrets play.  May be one is afraid or scared of
another.  Just try to keep an eye on when the ferret starts to shiver and
see what is going on in the environment.
 
Debbie
[Posted in FML issue 3044]