there isn't a wild German Giant. Before Australia got better at finding poachers, bearded dragons were smuggled out of Australia.(They don't allow any fauna out except under very rigid conditions) I think that this was stopped pretty firmly in the mid/late eighties (going by memory here and my memory is like swiss cheese!)
So you have these out of country customs officials who turned over a ton of dragons to reptile enthusiasts and zoos.(as well as the ones who weren't caught) The enthusiasts bred dragons in small local pockets with limited populations. The US bred a lot of Inland bearded dragons for color, which, while breeding very colorful dragons, has reduced their size. Lately, there has been an emphasis on reduced scales, so we see a lot of that now but they are the same breeds. There is a small scaled wild bearded dragon (I don't recall it's name) but I think it can only be found in Australia.
The German Giants were bred more for size than for color. You have a very natural brown/grey dragon who is very large. I'm not certain off the top of my head if they were also Inland bearded dragons or if they were from, say Western Bearded Dragons....I think they are Inlands but...like I said about the memory! Now, eventually we decided that the grass is always greener on the other side of the pond, so we've interbreed these isolated groups, the big and the colorful, to get the best of both worlds. The downside of that is trying to find one of those old German Giants who blood line hasn't been diluted for color. It's worth looking at YouTube for vids of wild bearded dragons. There are some really interesting clips.
If anyone sees any errors with this, please correct me. I'm dredging it out of the dark recesses that is my memory.
-Carrie
(PS on that link to the photo search is the BIGGEST RABBIT I've ever seen!)