Hello,
I'm new to these forums, but I do recognize some posters from other forums.
The question of why some southern coastal plain species in the Barrens but not others is extremely interesting to me, but I think what's missing from this conversation is the historical element - by that I mean that present species distributions have a lot to do with climate and landscape changes of the past several hundred thousand (or million) years. Glaciers have chopped up species ranges, species have retreated south or into small patches of former ranges, and have then expanded back out into new landscapes, etc. Maybe there were southern copperheads in the Barrens before the last ice age, and they just didn't make it through like the pine snakes, etc.
For more wacky species range maps, think of the smooth green snake out West, the Blandings turtle, or our little bog turtle.
Here's an interesting page about bog turtles:
http://www.tortoisereserve.org/Research/Lee_Herman_Body2.html
I can't vouch for its conclusions, but it does give a good sense of the historical forces at play in determining species distributions that look kind of funny.
As for my opinion on the matter, there are no copperheads in the Barrens. They hang out on the surface and seem to be pretty easily discovered wherever they occur naturally, unlike the scarlets. People find them in their backyards, you find them under surface debris, and I've found them crawling around at dusk (Georgia) or basking in plain view in the afternoon (SE Ohio).
Cheers,
Billy
Phillyherping.blogspot.com