# Monitors venomous?



## malarkine (Jul 7, 2010)

Hello everyone.
I was watching a documentary last night called Venom Hunter with Donald Schultz. On it he mentioned that within the last 3 years it has been discovered that Monitors have venom.
It's strange because I was under the impression that Monitors have a bacterial saliva like a Komodo Dragon which can infect you if bitten.
I was just wondering what peoples views on this were? Are they venomous or not in other words?
I found an interesting statement online that I am not too sure about. What is everyone else's thoughts?
Here is the statement:

"You must have heard the nonsense being promulgated by Dr. B.G. Fry, who is a pharmacologist, not a zoologist. The last few years he has been using the popular media to publicize his claim that colubrid snakes are "venomous." Even though it is true that colubrid snakes have a Duvernoy's gland, the secretions of which can be toxic if they are injected into an animal. Nevertheless the Duvernoy's gland is not a venom gland. The colubrid snakes themselves also have no means of injecting these toxic substances, because they lack fangs. Dr. Kenneth Kardong has rightly pointed out that human saliva is toxic, and if injected subcutaneously, can cause clinical symptoms. Therefore if we use Dr. B.G. Fry's definition of "venom," the Komodo dragon and Nile monitor are indeed "venomous," but then so are human beings, even though both the Komodo Dragon and humans lack any means of delivering these toxic substances and even though we do not use saliva to subdue prey or in defense."

"No, the Komodo Dragon is not venomous, and neither are humans. Nile monitors are of course not venomous. The claim that they are "venomous" is based on a failure by Dr. B.G. Fry to understand the scientific definition of venom. Toxin and venom are very different terms in science, and one should be careful not to confuse or conflate them."
The source written underneath was;
http://www.wsu.edu/~kkardong/Web%20of%20KVK_06b/Publications/Evolution_venom_app82.pdf.

Thanks for reading and any input is appreciated.
Greg


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## DavidR (Mar 19, 2008)

I'm unsure who wrote the piece that you quoted, but the fact that they used a reference from 1982 suggests that they are not as familiar with the current state of play. In instances such as this it is important to look at the evidence presented and decide for yourself what you think. 
Bryan Fry has a number of papers concerning this topic, this one may be the best overview of the research as a whole; http://venomdoc.com/venomdoc/Scientific_publications_files/2009_Fry_Toxicofera_review.pdf
but the Komodo paper may be of more interest to you.
http://venomdoc.com/venomdoc/Scientific_publications_files/2009_Fry_Toxicofera_review.pdf

I agree that it must be considered whether venom is actually used in predation, but natural selection does not allow an animal to produce a complex mixture of toxins if they are not actively being used (just look at marbled sea snakes). It is also important to remember that a venom doesn't have to kill an intended prey animal, as long as it subdues it in some way it will still be advantageous as long as the final result is a meal for the predator (i.e. if a venom allows a snake to expend less energy whilst constricting or swallowing).

The evidence suggests that monitors (and a number of other lizards) are venomous and the degree to which venom is used in predation by the majority is still up for debate.

David.


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## maffy (Dec 24, 2008)

*More thoughts*

Malarkine, please check out False Water Cobra's.. these are colubrids and venomous without doubt.


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## malarkine (Jul 7, 2010)

maffy said:


> Malarkine, please check out False Water Cobra's.. these are colubrids and venomous without doubt.


Hi maffy. I am aware of this. That's why I am asking about Nile Monitors, as this quote states they are not but it also states no colubrids are. So I obviously can't trust the quote which is why I am asking people on here.
Greg


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## Daniel10 (Dec 31, 2009)

Boomslangs and twig snakes are both Colubrids afaik and are both venomous. Not sure about Monitors but I've heard Komodos have toxic bacteria in their saliva.


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## ian14 (Jan 2, 2008)

malarkine said:


> Hello everyone.
> I was watching a documentary last night called Venom Hunter with Donald Schultz. On it he mentioned that within the last 3 years it has been discovered that Monitors have venom.
> It's strange because I was under the impression that Monitors have a bacterial saliva like a Komodo Dragon which can infect you if bitten.
> I was just wondering what peoples views on this were? Are they venomous or not in other words?
> ...


I have highlighted a particular phrase in the quote you posted to highlight just how mis-informed the person who originally wrote this is. The Duvernoy's gland is a venom gland, it has long been proven that this gland produces venom. In addition, to say that colubrids have no fangs is absolute rubbish. There are numerous species with enalrged rear fangs, commonly located just below the eye, which are used to allow venom to run into the bite wound, thus envenomating the prey. Furthermore, venom has been extracted from these species. 
Venom glands have been identified in komodo's.


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## maffy (Dec 24, 2008)

*appreciated*

Appreciated Greg, and I can see your issue with this. Although personally I would expect Dr Fry's work to be very thorough.

Certainly as a scientific paper it is highly technical.

The question is, what is the definitive understanding of VENOM and also TOXIN? Got to admit, I don't know.

Dr Fry is certainly more qualified to speak on the matter than I am.


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## ShaneLuvsMonitors (Sep 27, 2008)

as far as i am aware v. grisues, v. varius and komodos all have venom in there saliva. : victory:


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## Oderus (Nov 24, 2009)

Snake venom is something I don't read much about but from what I understood from the quoted paper it seems to saying that in non opisthoglyphous colubrids (not the true rear fangs) the duvernoy's secretions maybe only toxic by chance were there is not a modified fang to deliver it, but toxic by chance and venom precursor might be the same thing depending on view?.


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## DavidR (Mar 19, 2008)

> Certainly as a scientific paper it is highly technical.
> 
> The question is, what is the definitive understanding of VENOM and also TOXIN? Got to admit, I don't know.


Thankfully, quality of a paper does not increase with complexity by default, although Bryan Frys work more than stands up to scrutiny in my humble opinion.
The difference between a venom and a toxin - a venom is composed of toxins, in the case of venomous snakes the venom is generally highly complex with a relatively large number of toxins although only a few may be responsible for the major symptoms observed in the envenomed patient. With regards to 'colubrids' and monitors (and other non helodermatid venomous lizards) you will see the term 'toxic saliva' bandied around. There is no clear distinction between a toxic saliva and a venom, it is produced by the same type of gland, the toxin families are the same etc, it just happens that some species have a more advanced venom delivery system. 

You can look at the same argument from a number of different viewpoints. You could ask; are monitors (+all iguanian lizards and aglyphous colubrids) venomous from a:

Phylogenetic perspective - yes.
Predatory perspective - would depend species by species and remains to be seen for the most part, but for Komodos it seems the answer is yes.
Human danger perspective - again depends species by species (for the aglyphous colubrids, no).
Toxinological - yes, if you have the analytical equipment and know how you can pull toxins from these animals, albeit in small quantities in most instances.
The argument about 'toxic bacteria' is flawed. The symptoms such as catastrophic drop in blood pressure within a short time period of the bite are not in line with bacteremia.



> the duvernoy's secretions maybe only toxic by chance


In this situation it is possible to show the same toxin is produced by an aglyphous radiated ratsnake and a cobra. There is no question of the venomous nature of a cobra.

David.


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## terciopelo_dave (Jun 1, 2007)

To expand upon what David said regarding the symptoms not being consistent with bacterial septicaemia, the differences are clear.
Septicaemia usually appears very rapidly after an apparently benign period. The organisms have to multiply before the toxic effects are noticable, causing a latent period where the subject appears healthy, before a rapid and catastrophic cascade of symptoms. This is usually not before 24+ hours have elapsed.
With envenomation the symptoms become evident quite early. In komodos, especially when biting larger prey items, the effect is rather insidious in nature and develops slowly, although as said, initial symptoms are present within a small time frame. 
The process is markedly different from bacterial sepsis.


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## bothrops (Jan 7, 2007)

Direct quote from Brian (from his facebook) when discussing this 'venomous lizards' paper...http://www.mcponline.org/content/early/2010/07/14/mcp.M110.001370.long



> The fact that such critters are 'venomous' is from a technical, evolutionary biology perspective. As fascinating as it is, and as useful of a pool of novel compounds with significant potential for drug design and development it may be, their venoms have absolutely zero human medical significance. Just as all spiders are venomous but only a handful are of human medical importance. Similarly, even the humble garter snake is technically venomous but from a practical point of view it is non-venomous. This goes to the heart of the matter. There is a huge difference between being venomous from a biology viewpoint and venomous from a medical/legislative viewpoint.


Cheers

Andy


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## malarkine (Jul 7, 2010)

Thanks for all your input guys. It seems it depends which way you look at it. Never the less it's a very interesting subject and I shall look forward to reading more of peoples views and opinions.
Thanks, Greg


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## blood and guts (May 30, 2007)

Remember the old cview days when frys work first came out, how he was flamed! the timing with the awb and rspca wanting to ban everything again and a certain aussy pain in the butt further stering things made for some entertainment and some dam good info between it all.

I spoke to fry via pm about it back then and recently via face book and it does show some very intresting evidence. Also wolfgangs talk at the fbh confrence on this opened a few eyes.

Looks like he had the last laugh dont it.


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## NightGecko (Jul 17, 2009)

The only monitors considered venomous are V. komodoensis, V. griseus and V. varius.

But as said above I don't think their venom, however real, classes them as truly venomous

The two truly venomous lizards are the gila monster and the beaded lizard : victory:


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## Alon93 (Jul 5, 2010)

I even read that green iguanas and beardies have venom glands :gasp:


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## terciopelo_dave (Jun 1, 2007)

NightGecko said:


> The only monitors considered venomous are V. komodoensis, V. griseus and V. varius.
> 
> But as said above I don't think their venom, however real, classes them as truly venomous
> 
> The two truly venomous lizards are the gila monster and the beaded lizard : victory:


I'd disagree regarding the Komodo. If you define "venomous" as using venom in the aquisition of prey, either by incapacitating or killing, then the footage recently shown on David Attenborough's "Life" series shows clearly that Komodos are venomous.
I'd agree that they are possibly the only example of a _truly _venomous monitor, in the traditional sense of the word, but until more research is conducted I keep an open mind. Never say never.


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