All of my baby corns do that tail rattle at feeding time and a couple do it everytime I open their tubs they are so darn cute trying to act tough lol. I used to catch wold eastern hognosed as a kid and the would tail rattle sometimes too. Also we have a native snake in Ohio I think its a type of racer that flattens out to make a hood mimicking a cobra. And there's a couple native corns that really resemble copper heads if you don't know the difference.