They do store fat differently, in a dog in good flesh, they'll have fat on their butt, behind the elbows and in the abdomen. If he was in generally good flesh without noticeable skinniness in the ribs, it may very well have been trauma. His head turned back like that makes me think he was hit by a car, not very likely out there, eh?
That mottling is normal pigmentation, like you saw on your dawgs.
Sue, see my post number 9 in this thread. I confirmed that he was shot.
He was hit by a load of fine shot in the neck and shoulder area, probably 4's, and then dumped.
There was no evidence that he was shot and then ran to the spot where I found him.