We were walking my cat yesterday, and as we rounded the corner I saw what looked like an old piece of black rubber hose. It took me a second to realize that it was a pretty large snake. It was frozen, and fortunately my cat didn’t recognize it since snakes are a favorite play toy of his. (I think he thinks they are living shoelaces.)
I live in southern Missouri and rattlesnakes aren’t very common here, but they do exist. I wasn’t terribly concerned though, because it was jet black and I don’t think rattlesnakes are that color. But when it slithered away, there was no question that it was rattling it’s tail.
In addition to beowulff’s cite, I’ll add that many, many non-venomous snakes will rattle their tails. Especially juveniles. In addition to racers, I’ve seen young copperheads, common kingsnakes, and gopher snakes do the same.
I’d say it is extremely likely that rattlesnakes evolved to enhance an already pre-existing behavior.
I can’t tell from this cite if the black racer is usually in my neighborhood. If it was a black racer, it was a large one. I’d say it was about five feet long. It looked more like the rat snake, but that website doesn’t say anything about rattling. It was a pretty convincing rattle considering I didn’t see any evidence of an actual rattle on the tail.
I have seen some very long black racers. That is not out of their size range.
Oh, and the black racer pictured on that website is not a typical example. they’re usually jet black. That one looks grayish (oddly). Here’s a more typical example.
