I have taken in fert that was kept in bathtub.  After isolating this new
ferret for 8 weeks as my vet insisted should be done with all newbies --
fert was pretty good with litter box.  You need to start off with small
cage for many ferts so they have room for food, water, bed and litter box
only.Observe and praise fert for pooping in box.
 
Keep small cage even after litter box training has worked.  These guys tend
to back slide.  Also, you need a sick cage on hand for the guys anyway.
 
Socks took many months before he stopped playing with litter and kicking
out pounds of it every day[I have 17 litter boxes, and he would run from
box to box gleefully flinging litter out] But he is the one who lived in
a bathtub.
 
Sometimes, cage may be too small for all ferts, or they are bored: or both.
Then I hear stories of ferts pooping outside of box in cage.  Also-the
litter needs to be cleaned twice a day, and whole thing dumped and
replenished every week or so.
 
If you have more than 3 ferts, you probably need more than one litter box.
I surely do.
 
Hope this helps,
Lisette
[Posted in FML issue 2681]