hmm, if you were down here, I'd say snakes, definitely. However, I have no idea what varmints y'all have up there.
No snakes here bigger than a garter snake.
The more I think about it, it is probably a mole tunnel, though really deep for them. ecurbh had visions of a big underground cavern or sinkhole starting, and I wondered if he had another buried barrel. ;~D