The winter fur of the European polecat is brownish black or blackish brown, the intensity of which is determined by the colour of the long guard hairs.
On the back and flanks, the dark tone is brightened by bright whitish-yellowish, sometimes yellowish-greyish underfur which shows through.
The lightly coloured underfur is not equally visible on different parts of the body.
On the back and hindquarters, the underfur is almost completely covered by the dark guard hairs.
On the flanks, though, the lightening is well defined, and contrasts sharply with the general tone of the back.
The throat, lower neck, chest and abdomen are black or blackish brown.
The limbs are pure black or black with brown tints, while the tail is black or blackish brown, completely lacking light underfur.
The area around and between the eyes is black-brown, with a longitudinal stripe of similar colour along the top of the nose.
The ears are dark brown and edged with white.
The summer fur is short, sparse and coarse.
It is greyer, duller and lacking in the lustre of the winter fur.
The underfur is more weakly developed in the summer fur, and has a brownish-grey or rusty-grey colour.
The polecat is a good swimmer, but its fur is not as well insulated against cold water as the American mink's; while a mink will take 118 minutes to cool in a water temperature of 8 °C, the polecat cools down much faster at 26–28 minutes.

Polecats were found in two major phenotypes a typic one and a dark fur one with no black mask.
Colour mutations include albinos and erythrists.
In typical erythristic individuals, the underfur is usually bright reddish.
The guard hairs on the trunk are bright reddish or reddish brown.
Black guard hairs are absent on the lower body and head.
In some rare cases, the guard hairs are so light, they are almost indistinguishable from the pale-yellow underfur.
In these cases, the whole animal is a very light golden-yellow colour.
The winter fur of the European polecat is brownish black or blackish brown, the intensity of which is determined by the colour of the long guard hairs. On the back and flanks, the dark tone is brightened by bright whitish-yellowish, sometimes yellowish-greyish underfur which shows through. The lightly coloured underfur is not equally visible on different parts of the body. On the back and hindquarters, the underfur is almost completely covered by the dark guard hairs. On the flanks, though, the lightening is well defined, and contrasts sharply with the general tone of the back. The throat, lower neck, chest and abdomen are black or blackish brown. The limbs are pure black or black with brown tints, while the tail is black or blackish brown, completely lacking light underfur. The area around and between the eyes is black-brown, with a longitudinal stripe of similar colour along the top of the nose. The ears are dark brown and edged with white. The summer fur is short, sparse and coarse. It is greyer, duller and lacking in the lustre of the winter fur. The underfur is more weakly developed in the summer fur, and has a brownish-grey or rusty-grey colour. The polecat is a good swimmer, but its fur is not as well insulated against cold water as the American mink's; while a mink will take 118 minutes to cool in a water temperature of 8 °C, the polecat cools down much faster at 26–28 minutes.
Polecats were found in two major phenotypes a typic one and a dark fur one with no black mask. Colour mutations include albinos and erythrists. In typical erythristic individuals, the underfur is usually bright reddish. The guard hairs on the trunk are bright reddish or reddish brown. Black guard hairs are absent on the lower body and head. In some rare cases, the guard hairs are so light, they are almost indistinguishable from the pale-yellow underfur. In these cases, the whole animal is a very light golden-yellow colour.
European polecat