Black tail, blonde tail and the tail inbetween.

In 1781 a naturalist named Pennant described for the first time the bleached tails of red squirrels in summer coat (Sciurus vulgaris leucourus). 

We now recognize some 17 sub-species of the red squirrel (Sciurus vulgaris).  These sub-species are very similar to look at. However it is possible to spot some variation in colour. The Underscar squirrels, in August, can be seen with very different tail colourings.