Thought I'd weigh in on the subject...



To say that the rattlesnakes are "doing the mimicry" is certainly a big (and perhaps a bit misguided) evolutionary leap. The evolution of the rattle in Crotalids arises from a trait (as indicated in previous posts) that is rather commom in snakes (i.e. tail vibrating). What the rattle is, therefore, is a variation on this theme. In terms of adaptation, the evolution of the rattle may have made a defensive mechanism common to many snakes more efficient in detering predators. The trait is then passed on to their offspring. So by perhaps being able to produce a "louder" defensive sound in tail vibrating, the rattle itself provided a selective advantage.



So lets think of this subject in other terms. King cobras are renowned for their hissing, correct? Pituophis species also hiss...in fact have evolved an epiglottal keel. So is this a case of mimicry by bullsnakes? The answer is no. Hissing is a common and effective defensive behavior (and yes, behaviors are traits that can be passed on!). Pine, bull, and gophersnakes have taken this a step further and are really able to belt it out!



So, my thoughts are that traits like tail vibrating and hissing are common and effective defensive measures. As is the case with many traits (and at the heart of the theory of evolution), some species have (through various mechanisms...mutations, etc.) adapted more "extreme" examples of these traits, and have consequently passed it on because it was more effective in deterring predators.



Anyways...interesting topic, in my opinion!

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