Santa Cruz field station, Depto Loreto, Peru. January 11, 2011.
I was told that Liana Snakes are apparently a rare find in the area of Peru where we visit, but it seems like at least one shows up on every trip. It could be they are not a common snake, but it may be that they are not often seen, given their coloration. Or both. At any rate, a difficult snake to pose and photograph.
My Flickr album for this species is here.