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Topic: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

Well, since things are likely to be a little slow around here for the next couple of months, might as well throw out a topic for discussion:

I hear quite a bit from a variety of sources that an angry nonvenomous snake is "vibrating its tail to act like a rattlesnake."  What say you?  Fact or myth?  Are nonvenomous snakes true audio mimics of rattlesnakes or should people who claim this give a little more reasoned thought toward another explanation?

I have some thoughts, but will wait to hear from some others first.

Kory Roberts: Email | Facebook | Flickr | YouTube

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

It is a fact that other nonvenomous snakes vibrate their tail and it can sound like a rattlesnake if done so in dry leaves. But the true intention of the snake may not be to imitate the rattlesnake but just an act of aggresssion or nervousness. This act in itself has probably helped in the survival of the snake by detering possible predators and is possibly a trait that has been genetically inherieted due to its benifits of its possessssor.

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

Myth myth myth myth myth.  People are putting too much thought and human view into it.  This irks me big time.  Sure, they both shake tails when being defensive, it is a nervous twitch of sorts.  It just so happens that it also creates sound, and through lots of time rattlesnakes evolved something that exacerbates this noise.  Thus preventing trampling by hoof stock.

This irritates me almost as much as a hognose spreading out to look like a cobra.  This is so absurd.  A hognose doesn't know what a cobra is.  A cobra doesn't know what a hognose is.  In fact, who is to say that a cobra isn't imitating a hognose instead (if applying silly human thought to it).  It is neither.  Really, if you think about it, what does a hognose have to gain from looking like a venomous snakes to a species (human) that is going to be MORE likely to kill it if it is venomous?  They both have a strategy to look bigger than they are to avoid predation.  They share a common behavior/trait, but neither is a mimic of the other.

Really, the bigger more interesting can of worms is "Do kingsnakes really mimic coralsnakes?"

The Flying Spaghetti Monster is TRUTH

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

Isn't that what I just said?

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

sorta...
Bobby just said it better.   wink

Government is not the solution Government is the PROBLEM...Ronald Reagan

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

I don't think its necessarily that far-fetched.  I understand Bobby's point that the snake doesn't "realize" what it is doing, but that doesn't discount that tail-shaking may be an evolved mimicry behavior.  Hognose clearly are not mimicking cobras since they have not been sympatric with cobras for thousands (if not millions) of years.

I think the only way to test this would be to compare nonvenomous species that have evolved sympatrically with rattlesnakes to those that haven't.  The best way to do that would likely be to examine species outside of the Americas.  However, note that few, if any North American snakes that don't share similar microhabitats and/or size classes with rattlesnakes shake their tails- especially aquatic and subterranean colubrids.  Therefore, I don't think tail-shaking is simply an act of nervousness general to all snakes.

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

George Harper did some research on coral snakes and coral snake mimics...why would there be a mimic hundreds of miles away from a coral snakes range etc.  never read his paper, but I'd be curious on that as well.

Government is not the solution Government is the PROBLEM...Ronald Reagan

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

And I would also like to know:  Do Old World snakes vibrate their tails?  They are many miles away from rattlesnake.  What if a snake in an Asian, European, or Australian snake collection watched a rattlesnake in a nearby cage and tried to imitate, and then escaped, and then taught others to vibrate their tails.  And-and-and then....No, I don't wanna say anthing that might sound CRAZY.

"...be as wise as serpents..."  Matthew 10:16
"...I just thought that should be brung out"  ~Goober (on 'The Andy Griffith Show')

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

mfbullies, I meant no disrespect to you.  I started the reply before your post was posted.  I was saying "myth myth myth" to the idea, not to your post or your views.  I agree with you  smile

Van:  I don't think it is an act of nervousness in all snakes at all.  However, looking at the flip side of it, a lot of other closely related, typically high strung snakes to rattlesnakes shake their tails.  I've seen it in lots of Bothrops (yeah yeah, I know, another Bothrops rant, I can't help it, I love them), bushmasters, etc.  I highly doubt that a 9 ft Bushmaster shaking its tail is trying to mimic a pigmy rattlesnake that is shaking its tail.  I think they just have common nervous behavior that one exacerbated the sound of.  I'm not arguing that I'm right or you are wrong, I'm more curious in the discussion than anything.

Also of interest in defensive behavior:  Saw scaled vipers.  They have a very specific behavior that results in a noise that is more complex than a tail shake.

The Flying Spaghetti Monster is TRUTH

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

I've seen it in lots of Bothrops (yeah yeah, I know, another Bothrops rant, I can't help it, I love them), bushmasters, etc.  I highly doubt that a 9 ft Bushmaster shaking its tail is trying to mimic a pigmy rattlesnake that is shaking its tail.  I think they just have common nervous behavior that one exacerbated the sound of.  I'm not arguing that I'm right or you are wrong, I'm more curious in the discussion than anything.

I think a big Bothrops/Lachesis is bound to stir up leaf litter and make a decent amount of noise without a rattle.  I also wonder if tail-shaking may be an ancestral trait in north american pit vipers, since just about all of them seem to do it (not sure about Bothriechis?).  In North American colubrids, tail vibration seems to be most common in the Lampropeltine clade- kings, rats, pits, etc.  I'm not aware of many other north american colubrids that do it.  Racers, indigos, waters, hognose, etc. don't (though its been some time since I grabbed a racer/indigo so I might not remember correctly).

In response to David- that is kind of what I was leaning towards.  It doesn't seem that many snakes outside of north america are especially prone to tail vibration- someone please correct me if I'm wrong, as my brain is currently pretty fried.

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

I hate to split hairs here (okay, I admit, I really don't), but the tail shaking for me is hard to separate from the caudal luring of pitvipers.  Baby Trimeresurus and the related pitvipers shake their tails.... I wonder if the tail shaking in pitvipers could've given rise not only to the rattle of a rattlesnake, but also to the caudal luring behavior seen in so many pitvipers?????  I want to say that Bothiechis do "tail rattle", but to be honest I might be thinking to their caudal luring.  This nervousness is very present in Bothrops to the point that a lot of times you'll see them twitch their sides nervously right before they launch out like a spring.

I'm thinking back on what old world snakes do and do not shake their tails...  Most cobras "lash" their tails and whip them rather than "rattle" them.  I guess I need to go into my snake room and piss off some snakes.......

The Flying Spaghetti Monster is TRUTH

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

A couple of ...thoughts/questions:Pit vipers and hognose have stocky bodies, and don't crawl very fast.  Flight from predators is less of an option(than other snakes) so they need defensive devices(rattles, musking,etc)  Being slow might also mean they can't forage as much; any behavior that might bring in more prey (such as the tail twitching thing) would, uh...be helpful.
  Also, do/did non-American hoofed animals fear the rattle? (such as horses brought by European explorers.)

"...be as wise as serpents..."  Matthew 10:16
"...I just thought that should be brung out"  ~Goober (on 'The Andy Griffith Show')

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

prof.dave wrote:

A couple of ...thoughts/questions:Pit vipers and hognose have stocky bodies, and don't crawl very fast.  Flight from predators is less of an option(than other snakes) so they need defensive devices(rattles, musking,etc)  Being slow might also mean they can't forage as much; any behavior that might bring in more prey (such as the tail twitching thing) would, uh...be helpful.
  Also, do/did non-American hoofed animals fear the rattle? (such as horses brought by European explorers.)

I believe they do... most are very skittish.  It isn't so much that they fear the rattle b/c it is associated with a venomous snake, rather it is a "Oh %*#! I wasn't expecting that noise!"

The Flying Spaghetti Monster is TRUTH

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

On the topic of Old World snakes that do shake their tails when agitated, I recently traded off a very large female white lipped pit viper to our very own Courtney and she would shake her tail when she was ticked. She didn't do it when feeding, only apparently when she felt threatened. It didn't seem to be a caudal luring effort. I think it's more plausible to presume like it was said earlier, that various species of snakes shake their tails as a method of predator or other threat avoidance. That some refined the process to produce a very audible buzz is just sheer luck and coincidence on their part, much like the saw-scaled vipers Bobby mentioned - which have a completely different take on audible warning systems. Also cobras and other snakes (Pituophis too) that hiss. They of course can't hear it, but it doesn't make it any less effective.

I tend to side with Bobby though on removing the human equation (or at least our usual tendency to anthropomorphize) from how we try to describe the evolution of mimicry. There is obviously no conscious effort there to look or act like something else. Rather, the genes among the different species of snakes, despite the obvious phenotypic variation, are actually pretty similar to each other. Given similar environmental pressures, natural selection will tease out similar genotypic, and therefore phenotypic, results. Look at green tree pythons and emerald tree boas. Snakes that evolved in completely separate parts of the world (at least here recently), and that are found in two totally different groups. Yet, both species look very similar as adults, even share the same perching behavior, and their offspring are born a completely different color and go through an ontogenic color change to adulthood! Did these two sit down some millions of years ago and decide to take the same path to their modern forms? Of course not. Rather, the fact that they live in very similar habitats and face similar pressures resulted in similar genes being selected for while others were selected against, and therefore modern bodies and even behaviors similar to each other, despite the thousands of miles of ocean that separate them.

Chance Duncan
Atkins High School Biological Sciences
Central Director, Arkansas Science Teachers Association
479-477-0434

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

I too don't think that they are actually trying to mimic rattlesnakes. I'm on the boat that believes that they might have early snakes started it, which led to rattles on rattlesnakes and for other snakes to just keep doing it. Personally, I have witnessed Pituophis, Lampropeltis, Contia, and Thamnophis exhibit this behavior, all while in a seemingly nervous state.

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

Ok, I think we need to step back and clarify some things here.  IMO, the hypothetical tail-shake mimicry displayed by some colubrid and non-rattled pit vipers is a very specific behavior- a high-frequency vibration only exhibited by the snake when it is in 'fight or flight' mode in response to a threat.  While some forms of tail shaking have certainly evolved for other purposes (luring, for example), I don't think those are pertinent to this issue- though the question of whether the rattle originally evolved as a lure vs. a warning is certainly an interesting idea.

Rattlesnakes, other pitvipers, and some colubrids all vibrate their tails when under threat.  I can envisage three possible evolutionary scenarios for how these groups came to do this.  1) tail vibration is a neutral trait ancestral to colubrids and vipers, and has been subsequently lost in other taxa for other reasons.  2) tail vibration automatically serves as a deterrent to potential predators regardless of mimicry (i.e. aposematism, which is why milksnakes outside of coral snake ranges still look like corals, though George Harper's work has shown it doesn't work so well there).  3) tail vibration is primarily a viperid adaptation to warn predators/tramplers away from danger, has been accentuated by the rattle in rattlesnakes, and is now mimicked by other rattle-less species for the same purposes.

The biggest problem I see is that audibly announcing one's presence, as some snakes are bound to do, is useless unless they have something with which to back it up.  Snakes are incredibly fragile animals, and get eaten by just about everything larger than they are, if a predator gets the chance.  Flight and camouflage are far more effective means of avoiding predation, and tail vibration would only seem to work if the animal was stuck where it couldn't (or wouldn't) escape, and was already targeted by a predator.  If rattling evolved to warn quadrupeds away from trampling, again there has to be a reason to back it up, because what's it matter to a bison if it squishes a snake?  Therefore, I really doubt that defensive tail vibration is either an ancestral trait or a general aposematism.

Hissing could be a highly ancestral trait- some lizards, turtles, gators, and birds all do it.

Nonvenomous species (esp. egg-eaters) also stridulate, like saw-scale vipers.  Again, mimicry or aposematism?

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

edit-
by "mimicked .... for the same purposes" above, I don't mean consciously, but via natural selection

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

Van wrote:

If rattling evolved to warn quadrupeds away from trampling, again there has to be a reason to back it up, because what's it matter to a bison if it squishes a snake?

This I don't agree with.  My argument is that it isn't a "Hey, I'm going to attack you if you get closer" warning.  My thought is if you have a bunch of bison moving across a field, and the first few get close to a rattlesnake, they hear the buzz, they jump back and avoid that area, and being sheep (er, well, bison) the others are going to follow suit.  I of course haven't tested this (hey!  Dr. Pianka keeps bison!  I wonder if he'd let us borrow his... for science of course!) but from working other animals, I do know they seem to get skittish and jump back/avoid when they hear a sound from an unknown source.  I think the skittishness is a result of them being prey animals, not from them "learning" (and by learning I mean selection of traits for whatever reason, not learning within the individual) over time that rattles = envenomation.

The Flying Spaghetti Monster is TRUTH

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

Van wrote:

Flight and camouflage are far more effective means of avoiding predation, and tail vibration would only seem to work if the animal was stuck where it couldn't (or wouldn't) escape, and was already targeted by a predator.

But tail vibration could redirect a predator's attention, by sight and sound, from a more vulnerable area (head) to a less vulnerable area (tail).  So it wouldn't necessarily have to back it up as a threat display to convey evolutionary advantage.

I want to reread some of this thread when I have little more time, but I am curious as to what commonalities might occur for all nonvenomous snakes that tail vibrate vs. those that don't.

If Old World species vibrate their tails--and my understanding is that some do--then that pretty well sinks the "imitate a rattlesnake" hypothesis at the start.  But the topic is still interesting just from an evolutionary and behavioral standpoint.

Do small, fossorial snakes tail vibrate?  ...not sure I can think of any.

What about arboreal snakes?  ...what would the advantage/disadvantage be for tail vibration?  (realizing, of course, that some adaptations could be evolutionary "baggage".)

Do only snakes that live in habitats with "soundable substrates" (leaves in a forest or dry grasses of a prairie) tail vibrate?  Seems like some desert species also exhibit the behavior...and wouldn't really have anything of significance to brush the tail against.  Sand doesn't make much sound, so scales rubbing scales (saw-scaled viper) would offer more advantage perhaps?

Do more primitive snake species tail vibrate, or just Colubrids?   ...I have an inclination that this trait is probably very ancestral (more or less developed in all snakes), but could be swayed by argument.

Do any lizards exhibit tail vibration in a similar fashion?

Kory Roberts: Email | Facebook | Flickr | YouTube

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

So...get an American Bison and three wire enclosures that contain grass or whatever bisons prefer to graze on...in the first: a Fischer Price baby's rattler(operated by remote contol, unless somebody's baby...never mind).  In the second: a handshake buzzer.  In the the third: A 6' atrox (in a restraining tube so Dr. Pianka will volunteer his bison)   Also, are European bison extinct?  Just wondering. 
  I think I better get back to studyng for my finals.

"...be as wise as serpents..."  Matthew 10:16
"...I just thought that should be brung out"  ~Goober (on 'The Andy Griffith Show')

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

Flash display of aposomatic colors vs. damage redirection vs. other scenarios is explored by:

Greene, H.W. 1973. Defensive tail displays by snakes and amphisbaenians. Journal of Herpetology 7:143–161.

And frequency of tail damage can be used as an indication of primary function.  I know that we're not talking about this in particular here, but we are talking about tail use behavior so I think that some reading of other tail using behaviors might be useful.

For example, the question about small fossorial snakes and tail vibration, this function might not be measurable as it might be overshadowed by other tail use behavior (which has been explored in some fossorial snakes in AR here: McCallum, M.L., S.E. Trauth and R.G. Neal. 2006. Tail-coiling in Ringneck Snakes: Flash display or decoy? Herpetological Natural History 10(1):91-94. and available in PDF format here.

I know tail display is not what we are discussing here, but I'd argue that if a tail display behavior is being used by a species it is going to overshadow the use of a auditory warning.  I'd make the argument that visual tail displays are largely in small snakes, but mud snakes also do this, and they're large enough to fit in the category of a snake that could make audible rattling sound on leaves... But this further raises the question that maybe they tail display rather than tail rattle as rattling is not something that is likely in their microhabitat (which has been mentioned elsewhere).

I'm more or less brain storming, not saying this is right and that is wrong... Just presenting information that might be pertinent.  I, too, need to go back and reread and think about this when I can actually sit down and devote a little time to it.

The Flying Spaghetti Monster is TRUTH

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

This I don't agree with.  My argument is that it isn't a "Hey, I'm going to attack you if you get closer" warning.  My thought is if you have a bunch of bison moving across a field, and the first few get close to a rattlesnake, they hear the buzz, they jump back and avoid that area, and being sheep (er, well, bison) the others are going to follow suit.  I of course haven't tested this (hey!  Dr. Pianka keeps bison!  I wonder if he'd let us borrow his... for science of course!) but from working other animals, I do know they seem to get skittish and jump back/avoid when they hear a sound from an unknown source.  I think the skittishness is a result of them being prey animals, not from them "learning" (and by learning I mean selection of traits for whatever reason, not learning within the individual) over time that rattles = envenomation.

Good point, but you'd still have to figure out the reason why quadrupeds are skittish to sudden noises.

Do more primitive snake species tail vibrate, or just Colubrids?   ...I have an inclination that this trait is probably very ancestral (more or less developed in all snakes), but could be swayed by argument.

I've never seen any boa or python do it.  They do other types of tail displays (coiling especially), but they don't "rattle".

If Old World species vibrate their tails--and my understanding is that some do--then that pretty well sinks the "imitate a rattlesnake" hypothesis at the start.  But the topic is still interesting just from an evolutionary and behavioral standpoint.

Not necessarily.  Tail shaking may be an ancestral trait, but rattlesnakes have specialized it, and subsequent evolution of mimicry may have further refined it in sympatric nonvenomous species.  There are a lot of potential histories here, and not all of them are mutually exclusive, IMO.

Do any lizards exhibit tail vibration in a similar fashion?

I've seen skinks in australia do some wacky things with their tails.  I think its been hypothesized to direct predator attention to the tail, so they could drop the tail and escape (like you suggested earlier).  However, seems to me (anecdotally) that the snake species with the highest frequency of tail damage are not those that engage in heavy tail vibration.

I know tail display is not what we are discussing here, but I'd argue that if a tail display behavior is being used by a species it is going to overshadow the use of a auditory warning.

I dunno- the eyesight of those big quadrupeds isn't that good.  I don't know if they'd see a bullsnake or ratsnake shake their tails.

Lot of good stuff in this discussion.  Wish I had more time to think about it as well.

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

Van wrote:

Good point, but you'd still have to figure out the reason why quadrupeds are skittish to sudden noises.

I agree with this as well.  My current thoughts on it is that the quadrupeds that would be skittish to a rattlesnake rattle are wired that way b/c they are typically prey animals, and anything out of the ordinary will scare them.

The Flying Spaghetti Monster is TRUTH

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Re: Nonvenomous Snakes Shaking Tails to "Imitate" Rattlesnakes?

I would say that the tail vibration behaviour in New World snakes-pit vipers AND colubrids- would get the attention of potentally threatening animals and people, and could possibly increase the chances of them being left alone.  (I saw crows decapitate a copperhead once, and in many such cases the animal would probably not be detered by a barely audible vibration.)  As Van pointed out, snakes are fragile animals and anything that would slow down or distract a threatening animal might have slightly increased their chance of survival.
  As Van also pointed out, the bisons probably don't see that well.  (Maybe they use to think, "That really hurt like @*!!  Gotta remember to stay away from 'rattle grass!!") 
  No really new ideas here.  Just thinking outloud-sort of.

"...be as wise as serpents..."  Matthew 10:16
"...I just thought that should be brung out"  ~Goober (on 'The Andy Griffith Show')