Snake mimicry is an interesting topic.



Often times when people see 2 species exhibit similar behavior they automatically jump to the conclusion that the "less dangerous" animal is mimicking the "more dangerous" animal. As others have mentioned many snakes of many taxa shake their tails. It is probably just by chance that rattlesnakes enhanced this behavior. The evolution of the rattle itself is still not greatly understood. However, I do believe it is just an "enhancement" of an already existing snake behavior. I think about the only genus that comes to mind that I can say that I've tried to observe "rattling" in that I haven't seen it would be Nerodia. While Nerodia musk, thrash their entire body, bite, and otherwise act pleasurably, I've neve seen one "rattle" its tail. Why? I dunno.



Another thought that comes to mind is often times people will see a north american hognose flatten out and they say that "it is hooding up to look like a cobra so that you think it is dangerous." This is very misleading. The 2 animals share a common behavior for defense. One of the animals just happens to be venomous. This behavior is also seen in other venomous ane nonvenomous species. The hognose is no more mimicking a cobra than the cobra is mimicking a hognose.



As to why a rattle hasn't evolved on other continents a better question is probably why did it evolve in the Americas. Random chance. I would venture that on average a lot of your African ground dwelling species have adapted warning methods to avoid being trampled. The large vipers of Africa are quite good at hissing and making their presence known. Perhaps they just took a different path to accomplish the same purpose that the rattle serves in the Americas, and happened to do so by random chance.



And to really open up a can of worms, look at coral snake mimicry and whether it is or not :D

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