Why Is Wild Boar Skin Black?

I've been thinking about this question for a while and I still don't know the answer, I've tried goggling it but found no answer, the closest i found is wear they live on earth. here is the map i found from :http://upload.wikimedia.org/wikipedia/commons/a/a9/Sus_scrofa_range_map.jpg (all credit to them)
This map can answer my question a little because they live in some hot parts of the Mediterranean and India. A bit like humans there skin is naturally darker where more sunlight is and where its hot (I think Eskimos are dark because there aren't many clouds there?).
What confuses me about this question is that wild boars live in the forest where it is really dark, I can understand why they would have black bristles (camouflage/survival of the fittest) but what's the need for black skin?  Or am i completely wrong that there skins black and the ones I've seen have been black from dirt? Please can someone tell me the answer, thanks