Hierophis viridiflavus feigning death when handled

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Re: Hierophis viridiflavus feigning death when handled

Postby Guillaume Gomard » Thu Jan 11, 2018 3:15 pm

Berislav Horvatic wrote:Lay flat and motionless and irresponsive... "Feigning death" is something quite different from that...


I agree with this statement, that´s why some author make the distinction between tonic immobility (what you observed with your V.berus) and a more complex death feigning strategy which involves for instance body flipping, tongue hanging, defecation, etc.

Ilian Velikov wrote: I only know about the N. natrix and N. tessellata doing this (any others?)


In my short note I cite papers reporting on death feigning for most of "our" colubrids (but this behaviour is indeed more common in the 2 species you mention). If you look beyond Europe, then hognose snakes are also well-known examples regarding death feigning.

Ilian Velikov wrote:Also from all the N.natrix I've cought (which are a lot) only one individual did feign death


This proves you are a gentle man, Ilian ;) I personally experienced more death feigning N.natrix over the last years. In their article (DOI: 10.1037/0735-7036.121.2.123), Gregory and Isaac report a pretty high number for N.natrix: "Death feigning was seen in 66% of wild-caught snakes". Also, I think you will be interested in their conclusion: " so far as we can ascertain, death feigning in grass snakes has been observed only in response to humans (...) What is required to complete this story for grass snakes and most other species is convincing demonstration of successful death feigning in response to natural predators in the field and consequent fitness benefits compared with non-death-feigners.".

This study is already from 2007, I have no idea if this last point was investigated since then...
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Re: Hierophis viridiflavus feigning death when handled

Postby Ilian Velikov » Thu Jan 11, 2018 3:38 pm

Michal Szkudlarek wrote:The possibility of being killed is lower if you feign death because predators prefer eating animals which are evidentially alive.

That's why most death feigners do it before they get caught. If snakes do it after they get caught they were very evidently alive and "died" after the predator got them, which is the predator's aim to start with. So, what's the point?

Guillaume Gomard wrote:This proves you are a gentle man, Ilian

Thank you Guillaume, I do try to be as gentle as possible with any animal I handle.

Guillaume Gomard wrote:I personally experienced more death feigning N.natrix over the last years. In their article (DOI: 10.1037/0735-7036.121.2.123), Gregory and Isaac report a pretty high number for N.natrix: "Death feigning was seen in 66% of wild-caught snakes".

Could the frequency of this behavior vary geographically? The one of "my" N.natrix that did it was in the UK, while none of the many I've caught in Bulgaria did it. I assume most of this research was also done in Western Europe. I still have to see how the Iberian ones react to my handling.

Guillaume Gomard wrote:" so far as we can ascertain, death feigning in grass snakes has been observed only in response to humans (...) What is required to complete this story for grass snakes and most other species is convincing demonstration of successful death feigning in response to natural predators in the field and consequent fitness benefits compared with non-death-feigners.".

Yes, this is very interesting indeed and backs up my pessimism about this behavior being a successful defense mechanism, or defensive mechanism at all. The fact that it was only observed with humans suggests that it might be triggered by something else (prolonged excessive stress, exhaustion..? ). Humans are the only predator that would "play" with the snakes, molesting them for a long time. With any other predator the snake is more or less killed immediately or in a matter of seconds, so there would be no time or point to "play dead".
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Re: Hierophis viridiflavus feigning death when handled

Postby Ruggero Morimando » Thu Jan 11, 2018 6:14 pm

Ilian, you write: "The fact that it was only observed with humans suggests that it might be triggered by something else (prolonged excessive stress, exhaustion..? )."

Memory is very labile in humans, but during my years of University in Pavia (first 1980 years till early 1990s) Natrix natrix was an extremely common snake around the town. Now it's no longer so, but during those years I've captured really many specimens of Natrix natrix.
It was rare to find a Natrix which NOT displayed death simulation. And in many, maybe in most cases, the simulation began as soon as the snakes were taken in the hand. Not after long handling...
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Re: Hierophis viridiflavus feigning death when handled

Postby Berislav Horvatic » Thu Jan 11, 2018 6:20 pm

Ruggero Morimando wrote:It was rare to find a Natrix which NOT displayed death simulation. And in many, maybe in most cases, the simulation began as soon as the snakes were taken in the hand. Not after long handling...

Those bloody empirical data, they could devastate any nice theory/hypothesis... What a shame...
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Re: Hierophis viridiflavus feigning death when handled

Postby Clive Brignull » Thu Jan 11, 2018 7:37 pm

Instinctive killing (or for the apparent enjoyment) is seen in cats,dogs,fox's,killer whales etc. Many a domestic cat has been seen prolonging the death of its prey only to walk away without consuming it's victim once it ceases to amuse. I presume if they have already had their fill then there is no need to eat. Regarding snakes feigning death, has this strategy been observed in the wild and if so what was the outcome?
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Re: Hierophis viridiflavus feigning death when handled

Postby Ilian Velikov » Thu Jan 11, 2018 11:27 pm

Berislav Horvatic wrote:Ruggero Morimando wrote:
It was rare to find a Natrix which NOT displayed death simulation. And in many, maybe in most cases, the simulation began as soon as the snakes were taken in the hand. Not after long handling...

Those bloody empirical data, they could devastate any nice theory/hypothesis... What a shame...


I said "suggests" and "might" meaning I don't know if this is the case or not. It was just a thought. Obviously it has been documented many times but this doesn't answer anything. What interests me in this is that your individuals did it almost immediately after being caught while my single one tried to escape first. It would be interesting to hear about other people's experiences.

Berislav, the lack of this behavior in the many Natrix I've cought is also empirical data ;)

Ruggero, what are your thoughts on the other questions then? Why was it observed with humans only? Do you really think it's an effective defense strategy and how and against which predators?

Clive Brignull wrote:Regarding snakes feigning death, has this strategy been observed in the wild and if so what was the outcome?

Apparently, as already mentioned, it was ONLY observed in wild snakes and never in captive ones (at least with Natrix) and only when "attacked" by humans (no other predators).
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Re: Hierophis viridiflavus feigning death when handled

Postby Ruggero Morimando » Fri Jan 12, 2018 5:34 am

Ilian wrote: "Ruggero, what are your thoughts on the other questions then? Why was it observed with humans only? Do you really think it's an effective defense strategy and how and against which predators?"

I'll try to answer, or at least to write what I can think.
First problem: where was it written that death simulation is displayed only with humans?
Saying something like that should mean that a Natrix is able to distinguish during a rush flight a human from a dog, or from a cat or a fox and react differently with different "big" predators and I think it's not the case.
This death simulating behaviour, I think, is observed mainly with humans simply because we observers/herpers are humans, and it's rather difficult to observe in nature a predation/interaction of other species (birds, foxes...) with a Natrix or a snake in general. But I'm pretty sure that, if someone of us has cats in a Natrix habitat, it would not be very difficult to observe death simulations of the Natrix elicited also by "contacts" with cats...
An empirical test could be trying to capture some wild Natrix masked as foxes or eagles... :lol:
But we must also consider that humans are big predators who (normally, at least we herpers) immediately take up in their hands the harmless snake: probably, if a big Natrix is attacked by a baby fox (just an example) the snake will notice that the potential predator is rather small (and, important difference, the predator is NOT ABLE to capture or lift up the prey as we normally do...), and maybe/very probably, in those frequent cases, other strategies could be initially adopted... a bite for example, or some hisses...
Hence the erroneous conclusions that death displays are adopted only with humans... ;)

Second question. Why only in wild snakes?
Because captive ones are already used to be taken in the hands or at least used to the presence of the keeper.

Third question. Is death simulation useful? Or, at least, could it be useful on some occasions?
I think yes. Because death simulation is "almost always" (as far as I've experienced) accompanied by foul smelling cloacal secretions. Death simulation + smell of rotting animal do not make an appealing meal for most predators. And: what other chanches could a Natrix have to save its life if it's already in the "hands" of a cat or a prey bird?
I think the transformation of a living animal in a dead and rotting (!) one is actually not a bad idea of the Natrix evolution... :D
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Re: Hierophis viridiflavus feigning death when handled

Postby Ilian Velikov » Fri Jan 12, 2018 10:03 am

Ruggero Morimando wrote:where was it written that death simulation is displayed only with humans?


Guillaume Gomard wrote:Gregory and Isaac report a pretty high number for N.natrix: "Death feigning was seen in 66% of wild-caught snakes". Also, I think you will be interested in their conclusion: " so far as we can ascertain, death feigning in grass snakes has been observed only in response to humans.


Ruggero Morimando wrote:Hence the erroneous conclusions that death displays are adopted only with humans...

No, nobody made that conclusion. I was following what Guillaume posted from Gregory and Isaac. Of course, it doesn't mean they don't do it with other predators. Maybe we just haven't seen it for the reasons you already mentioned.

Ruggero Morimando wrote:I think yes. Because death simulation is "almost always" (as far as I've experienced) accompanied by foul smelling cloacal secretions. Death simulation + smell of rotting animal do not make an appealing meal for most predators. And: what other chanches could a Natrix have to save its life if it's already in the "hands" of a cat or a prey bird?

OK, it makes sense to some extend but I'm still not completely convinced. Another question that I asked but seems went unnoticed was wether this behavior varies geographically. I think it is possible that Natrix distinguish between the type of predator and adopt different strategies. In Bulgaria (and maybe the Balkans) N.natrix is highly associated with water, in fact it is almost as aquatic as tessellata, so the most frequent predators there would be herons, storks and otters. Playing dead against these would get you nothing, and in fact you would be dead before you can starts pretending to be :) I think in this part of its distribution it would be very rare for Natrix to be prayed upon foxes. So maybe snakes there do it more rarely if at all. On the other hand in UK (where I caught the death feigner) N.natrix is pretty much almost completely terrestrial and anyone that has been there knows that there are more foxes than flies ;) So playing dead there might actually have an effect. Obviously there's a big part of Natrix distribution between Bulgaria and UK and I don't know what's the proportion of death feigners there.

Another question that comes to mind is about that foul-smelling "secretion". In all cases when I've had it on my hands it looks simply as excrement. Forgive me if I sound lame but I've never kept any snakes and I don't know how their excrement smell, so could this be just how Natrix poo smell and not a special secretion? And could it be that they release it every time they play dead just because they relax all their muscles?

And to finish I'll just re-post the quote that Guillaume posted:

Guillaume Gomard wrote:What is required to complete this story for grass snakes and most other species is convincing demonstration of successful death feigning in response to natural predators in the field and consequent fitness benefits compared with non-death-feigners.
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Re: Hierophis viridiflavus feigning death when handled

Postby Guillaume Gomard » Fri Jan 12, 2018 12:56 pm

Ruggero Morimando wrote:Third question. Is death simulation useful? Or, at least, could it be useful on some occasions?


Let me quote again a paper by Gregory (http://www.bioone.org/doi/pdf/10.1670/15-103), where such a situation is described:

"Death-feigning, discussed above, is an example of a last-ditch attempt, perhaps a desperate one, to avoid death. Predators that relax their grip when a prey is apparently dead may momentarily look away, allowing the prey to escape. Alternatively, predators that cache their prey may mistakenly cache a death-feigning prey, which could escape when left alone. Clearly, however, this strategy will not work against a predator that kills and consumes its prey immediately."
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Re: Hierophis viridiflavus feigning death when handled

Postby Ilian Velikov » Fri Jan 12, 2018 2:10 pm

Guillaume Gomard wrote:"Death-feigning, discussed above, is an example of a last-ditch attempt, perhaps a desperate one, to avoid death. Predators that relax their grip when a prey is apparently dead may momentarily look away, allowing the prey to escape. Alternatively, predators that cache their prey may mistakenly cache a death-feigning prey, which could escape when left alone. Clearly, however, this strategy will not work against a predator that kills and consumes its prey immediately."


This pretty much sums it up very nicely! It is possible then that the frequency at which Natrix display this behavior depends on the species of predators they co-exist with, which might explain the difference me and Ruggero had with snakes feigning death.

Just to add another thing about the foul-smelling secretion - Although I've only encountered death feigning once I've had the nasty smell on my hands almost every time I caught a Natrix, i.e. they secret (or simply soil themselves out of fear like most snakes) even without feigning death, so I don't think the smell is related to this behavior or that it evolved particularly to enhance the dead/rotting effect. The fact that other species such as pythons and apparently whip snakes feign death but don't have a foul smell also weighs in favor of this.
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