Active hunters, especially sight hunters, are going to seem more intelligent. Ever try stalking a coachwhip in a field of uncut grass? They will occasionally periscope to pinpoint your location while every time increasing the gap. You basically have to bolt to catch them if you spot one on the prowl. Wouldn't call it intelligence so much as using the inherent tools they've got given their spot on their evolutionary chain. Does it take more smarts to visually chase something down as opposed to tracking a scent? What about sitting near a body of water and waiting for prey to come to you? When snakes start using tools I'll begin production on "my snake is an honor student" bumper stickers for you folks who need them.