After almost 9 years experience with nearly 50 pet ferrets (we rescue and
keep them all!), I can tell you that ferrets generally like to eat soap.
Although you may not notice any obvious consequences, soap-eating cannot
possibly be good for them.  Ferrets also love the smell of soap, and Scooter
may be attracted to the scent left in the tub after your shower.  I would
recommend simply rinsing the soap residue out of the tub after showers, then
go ahead and let him play in there, licking all the water that he wants.
[Posted in FML issue 1688]