With black or very dark green tarry bowel movements promptly have your vet check for ulcers. There is an excellent article by Dr. Bruce Williams on ulcers in a past issue of "Ferrets" magazine, and also info in the resources (archives, etc.) listed in the critical refs in http://www.ferretcongress.org. If it is ulcers think Carafate as a first move and see my post today on meds for purchasing and safety tips. [Posted in FML issue 4605]