Christmas tree bark can leach tannic acid into the water.  Depending on how
fresh the tree is and how it was cut, this could be toxic to the ferret.  My
vet reports problems of anemia and heart arrhythmias.  Changing the water
frequently so it does not stand for more than 4 hours can alleviate this
problem.
 
I remove sap from ferret fur with Linatone or Ferretone or a light vegetable
oil.  (WD-40 works great for humans with sap, but the ferrets don't seem to
like it very much!)
 
Happy and safe holidays from Erika and the Magnificent 7!
[Posted in FML issue 1781]