An Unusual Fox Tail

Fox tails are usually bushy masses of white, black, gray, and orange fur.  Not this fox's tail though.  This one looks like it could belong to a rat.

I'm unsure as to what the cause of this odd looking tail is, but I have a few ideas in mind.

It could be malnutrition, mange, disease, hormone imbalances, or maybe it has pulled fur out of its tail to add warmth to a den (yes, some foxes do this in the same way that some birds pull out down and feathers for the same reason).

Here's a picture of a different fox in the same location with a bushier tail.  What a beauty!