Ferret droppings are black, thin and taper towards a twist at each end (they can be clumped or single).
Ferret droppings are 40–70mm long and 10mm wide, and look very similar to those of stoats and weasels, including the taper towards a twist at each end. They are hard and black when dry and are often left in conspicuous positions (e.g. on top of a rock) for territorial marking. Ferrets also make latrines (piles of droppings) at den entrances.
Drawing: by Sonia Frimmel