Any time a young ferret strains in the litter box and passes small amounts of dark, foul-smelling feces, consider foreign materials. Bits of rubber, latex toys and the like are very appealing to the young ferret.
If the material is small enough to avoid blockage, it will pass through. But on the way through, it scrapes the lining of the gut and causes hemorrhage and abnormal digestion in the areas that it travels through. The behavior of the ferret, the odor and the small, dark, loose nature of the stools is very characteristic.
If you suspect your ferret has ingested a foreign material, strain all of its poop to find the material. This means picking it up and washing it through a fine sieve in water, or just rolling it around in your fingers (yuck!) under a moderate stream of water so you can find any particulate matter in there.
Foreign material tends to take a while to pass, so don’t stop the first time you “strike gold.” You aren’t out of the woods, and there is inevitably more to come (and still a chance of blockage).
Dr. Bruce Williams is a recognized expert in the disease and pathology of the domestic ferret. He works at The Armed Forces Institute of Pathology in Washington, D.C.