Diane,
 
Go with a calm head, and remember, you are trying to help the fuzzies.
Loosing your temper only makes people close their ears.
 
That said, gather info on the proper housing of ferrets.  (if it's
something like "ferrets for dummies" that they probably have in the store
already it would be good).  Show the manager, in writing, how a ferret
should be kept.  Be polite and remain calm.  Let the manager know that
you are trying to help both the store and the ferrets.  No one would buy
something that obviously stinks and draws flies, right?  You could even
show him/her where the proper supplies are kept in the store.  Get his
or her name and make sure that he/she knows you plan to follow up on it.
Check back in a few hours, or the next day, to see if the ferrets are
properly housed.  If not, then its time to see the district manager or
contact Petco itself.  You can get a listing of district managers for
Petco, and the Petco contact info online.  I've dealt with them once
before and they were very helpful.  The manager had no idea he was doing
it wrong and was glad of my help.
 
I know it's really hard not to scream in these peoples faces and jump up
and down on their chests, but "you get allot more flies with sugar than
vinegar".
 
Best of luck.
Shelley
[Posted in FML issue 4307]