There is a creature in Northern Europe called the ermine. Like the mink it is well known for its fur. The fur of the ermine is prized because it is pure white; a good quality ermine pelt is very valuable. The quality depends on the purity of colour with no flecks or shades of other colour and an undamaged pelt. If an ermine pelt is damaged it is not worth the same money. Ermine skins are used for high fashion fur stoles or wraps.
To catch the ermine, the hunters wait until the ermine leaves its burrow. Then they smear the inside edges of the burrow with black pitch and wait with dogs especially trained to not attack and damage the fur but to corral the animal in and not let it escape. When the ermine returns it will not go down its burrow. It smells the black pitch smeared at the entrance to its home and so will not go back down the burrow to safety. The Ermine would rather sacrifice its life than blemish its pure white coat.