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Metabolism of the Crotalinae.
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by theemojohnm on October 28, 2008
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When we think of what snakes eat, it is obvious, and makes alot of sense that certain snakes venoms are "tuned" for the prey item they naturally target in the wild. This post brings into account many recent topics active both here, and the Venom-Center forums lately. There will always be exceptions, but if we think generally that most pitvipers (and true vipers for that matter, but specifically pitvipers) have a primarily hemotoxic venom, and most elapids have a primarily neurotoxic venom, consider this...
Alot of elapids tend to be much more active in daily activities, and digest food at more rapid rates than pitvipers. Alot of people agree that the hemotoxic venom of pitvipers probably acts in the nature it does for one main purpose, to help digest, or "break down" food before the animal has even reached the fallen prey item. While the neurotoxic venom of most elapids targets the nervous system for a rapid death. If we speculate that warm-blooded animals envenomated with hemotoxic pitviper venom are already "partially broken down", then if would explain why an elapid would need more heat (the annual climate of most elapids tends to be alot warmer than the pitvipers of the US climate), to help metabolize food. And, also would naturally leave elapids naturally more active, for the same reason.
We see this happen with alot of juvenile rattlesnakes in the US as well. While many younger specimens of particular species of American pitvipers seem to harbor neurotoxic components when young, when their diet consists of lizards and frogs. Eventually, warm-blooded prey items start to make up the majority of the diets of some species when the size of the animal increases. So too does the venom composition change seemingly.
It seems rather likely, that the hemotoxic venom of pitvipers (again, even alot of true vipers), is designed for warm-blooded prey, and living in certain climates. While elapids are naturally more active and tend to be found in hotter climates (just generally speaking).
This brings into consideration the "venomoid" topic, of which I hope this does not turn into a huge debate over. Most venomoid snakes I have personally seen were cobras. This is probably in part, due to their alluring nature among people, and a bigger "need" in some peoples eyes to "remove their natural weapons".
Furthermore, lets bring into consideration the topic of "overfeeding" snakes, which does seem to greatly shorten the lifespan of most snakes. It seems to me that venomoid elapids would "survive longer", than a venomoid pitviper, or other hemotoxic true viper. If we think in the view that snakes seem to have a pre-programmed food intake expectancy over the course of their lives (and at certain intervals), it seems to me that snakes with primarily hemotoxic venoms naturally have a slower metabolism, relying at least in part, on the hemotoxic venom to aid in breaking down food. Where as primarily neurotoxic elapids wouldn’t have as hard of a time, and probably live longer venomoid, because their venoms seem to be designed for a "quick kill" of different prey items. If given pre-killed food, elapids probably rely more on their daily activeness, and the use of heat (their natural climate), for the digestion of their food.
However, "venomoid" hemotoxic vipers and pitvipers are forced to use more resources to digest their food, which naturally, their hemotoxic venom SHOULD be helping with to a certain extent. Of course, this entire post is nothing more than my personal opinion, and a great speculation at that. This is just what I have observed, and what makes sense to me. When we think of many American rattlesnakes species basking in the same spot, not moving for hours, it makes sense that they have to rely more on the heat of the climate of the US, and a hemotoxoic venom to digest their meals. While elapids, using mostly neurotoxic venom naturally have higher metabolic rates, and are subsequently more active. (again with alot of elapids coming from much warmer climates than our US pitviper climate).
Of course, there are always exceptions, and my theory here doesn’t match in many cases. We find some pitvipers (and many true vipers) in some of the warmest parts of the world. Then again, so to do some of these vipers use neurotoxic components in their venoms.
I would like to know everyone’s feelings on this, as many of you probably have much more knowledge on this subject. On a side note, I AM AGAINST VENOMOIDS, but do not wish to have this turn into a huge debate on the "ethics" of such a procedure.
I hope this thread has the potential to turn into a good debate, as much of this is only speculation.
What are everyone’s feelings on this subject?
Take Care.
~John Mendrola (Pennsylvania Woodland Herpetological).
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RE: Metabolism of the Crotalinae.
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by yoyoing on October 29, 2008
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Add to your thoughts where the more neurotoxic rattlesnakes are found (warmer climates).
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RE: Metabolism of the Crotalinae.
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by Jahon on October 29, 2008
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Great observations! But I've noticed that when I feed my rattlesnakes pre-killed food they dont actually envenomate it, they just start eating it. So how would the health of a viper or pit viper feeding exclusively on pre-killed prey items be affected?
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RE: Metabolism of the Crotalinae.
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by theemojohnm on October 29, 2008
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The topic of wether pitvipers actually do envonomate pre-killed food was actually just brought up on another forum.
The truth is, you DO NO know for certain if that snake is injecting venom. There are a very small ammount of recorded observations that I know of however, that suggest that alot of snakes do not actually envenomate pre-killed food.
But, I assume when you "feed" your rattlers, the prey item obviously does eventually end up in the snakes mouth. We all know how instantaneous an envenomation can be. Perhaps the snake senses the prey is dead but does inject a small ammount to aid in digestion when the snake "walks" the prey item into its mouth using its fangs. Again, there is some evidence that suggests many captive snakes do not actually envonomate pre-killed food at all, but I'm not sure how credible these are. I honestly dont know if I can believe that. But, I am open to hard evidence on the subject. If anyone has any links to actual credible studies, please post!
Another thing to consider is that, unless the snake is "gently" presented the its food, in alot of instantaneous strikes, I find it hard to believe the snake actually realizes the prey is dead in alot of cases. Some particular speciemns just "smack" that mouse as soon as the cage door opens.
The point is the animal has the OPTION to envenomate, so if it does not feel as though the prey is alive, it can simply eat and rely on its natural metabolism to digest the prey. The opposite goes for if the snake thinks the prey is alive, it may use its venom to aid in digestion. Most snakes encounter live food in the wild, so pre-killed food in a captive setting doesnt do my theory justice.
Its just that venomoid snakes do not have this option. I guarantee that your rattlers do use venom some of the time, maybe not allways, but I find it hard to believe that NO venom winds up in the mouses body before swallowing. Venomoids can NEVER do this. So perhaps some snakes do this only when they need to, but hemotoxic venoms seem designed for a purpose, or why arent all snakes venoms the same?
A venomoid can NEVER do this, even if it has to.
Take Care.
~John Mendrola.
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RE: Metabolism of the Crotalinae.
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by Buzztail1 on October 29, 2008
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John,
Some additional considerations:
1. If the snakes in question are on a healthy feeding schedule with good heating/hide/hydration/etc, it will not matter whether they envenomate or not. They will eat when food is offered, digest and metabolize just fine.
2. In the wild, some snakes' food will escape even though it is envenomated. That won't happen with pre-killed in captivity.
Just some observations. I have seen a lot of speculation on the part that venom plays in the digestion process but no proof one way or another.
With all of the money being poured down the MtDNA drain right now to prove that "this yellow snake and that black snake are actually the same and are not subspecific at all", it seems that someone would be able to come up with a definitive study to prove whether venom is necessary/beneficial for the digestive process.
Just my own personal opinions,
Karl
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RE: Metabolism of the Crotalinae.
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by Cro on October 29, 2008
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It would be fairly easy to inject some sort of radioactive tag directly into a snakes venom gland.
Then offer the snake frozen / thawed mice to eat, without letting the snake strike the food item.
Then run a Geiger Counter over the snakes stomach area, or take an X Ray, and see if it registers.
If it does, the snake injected some venom as it used its fangs to walk the food item down. If it does not register, then the snake is not using venom in feeding.
Repeat the experiment with several feedings of the same snake, and with several different snakes.
Also, vary the temperatures between the trials, just in case the snake might use little or no venom at warmer temperatures, and might use some or more at lower ambiant temperatures.
Best Regards John Z
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RE: Metabolism of the Crotalinae.
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by theemojohnm on October 29, 2008
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Thanks for your input Karl!
I still seem to feel that at least SOME venom does enter the body of bitten prey item even perhaps while being swallowed. But, your longer venomous experience does hold more observed feedings than I have seen in my lifetime. I will take that into account!
Take Care.
~John Mendrola.
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RE: Metabolism of the Crotalinae.
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by theemojohnm on October 29, 2008
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John, I would love to hear your more of your thoughts on this topic.
Obviously, this theory is a VERY big speculation, but it seems to me to "fit" in alot of cases.
What do you think about the general statements I described above? Maybe this is one for Dr. Wolfgang Wuster, or Dr. Bryan Fry...
Take Care.
~John Mendrola.
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RE: Metabolism of the Crotalinae.
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by Cro on October 30, 2008
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John, running the idea by Wolfgang Wuster and Bryan Fry would likely produce some very interesting observations from both of them.
Best Regards John Z
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RE: Metabolism of the Crotalinae.
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by FSB on October 30, 2008
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"It would be fairly easy to inject some sort of radioactive tag directly into a snakes venom gland."
I always enjoy and admire Cro's ideas... it's one thing to come up with a hypothesis, but quite another to actually think of a way to test it.
I have seen many snakes, especially my young blacktail rattlesnakes, seize a pre-killed but warm rodent and obviously give a good squeeze of the ol' Duvernoy's glands. This is also commonly observed with Bitis ssp. of all sizes, and I'm sure they'd set John's Geiger counter to ticking.
As for snakes envenomating pre-killed prey while swallowing, or "walking" the prey into their mouths, I have not noticed any of my Crotalines employing their fangs when swallowing as Gaboons and Rhinos do.
However, one real consequence of long-term captives simply swallowing, and not striking, pre-killed prey involves not the venom, but the fangs, which do not get broken off as they normally would, leading to snakes that have a mouth full of replacement fangs in their old age.
Re. the higher metabolisms of the more "active" elapids... one must be careful with generalizations, as quite a few members of this family, including the kraits, death adders and coral snakes, are not particularly active, and are even lethargic. Type of prey is also a key factor in the type of venom. Neurotoxic qualities tend to be more prevalent amongst snakes which feed upon ectothermic prey, including the young of such Crotaline species as Crotalus oreganus ssp., which start out feeding on lizards and frogs with more of a neurotoxic content to their venom, which gradually becomes more hemotoxic in content as the maturing snake switches to mammalian prey.
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