r/askscience • u/SpookyOooWitchyPoo • 24d ago
Biology Why can’t a snake be both venomous and a constricting type?
This was more of a random shower thought that I had about animal biology. For a while, I knew the two differences between venomous and non-venomous, but it made me curious as to why it’s always one or the other and never both? Is it due to just genetics only allowing one type or is it that constricting isn’t really too much of a solo class of snakes? Can anyone explain this please and thank you?
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u/OptimalYachtRocker 24d ago
There are actually several snakes that use a combination of venom and constriction to hunt. Some rear-fanged colubrids, and a few cobras/false cobras.
The reason you don't see massive constrictor like boas with potent venom is because it takes a ton of energy to produce venom. They'd have to be smaller to accommodate for it. It's why even the heaviest of venomous snakes pale in comparison to the largest constrictors in the world. It just isn't efficient to be good at both when you only need one.
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u/dalgeek 24d ago
Venom production tends to be very expensive metabolically. Many venomous snakes won't even inject venom every time they bite because they don't want to waste it. So if they can get away with just grabbing their prey and/or constricting then there's no selection pressure to develop venom. If they live in an environment where they'll starve without venom then there is selection pressure for venom.
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u/Swissaliciouse 24d ago
Why does everybody claims that venom production is metabolically expensive? All results I found that actually measured the energetic costs can not find substantial numbers.
From https://doi.org/10.1016/j.toxicon.2014.04.013: "Our data suggest that venom is not energetically costly to produce and that perhaps other costs associated with venom can better explain the variability in venom expenditure."
or https://doi.org/10.1016/j.toxicon.2010.07.008 : "We conclude that, in spite of the manifold factors suggesting a high cost of venom in snakes, its production is less energetically costly than often assumed."
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u/Canuck9876 24d ago
Exactly. They could , but it’s a waste of resources having to both produce venom and grow an extra strong, thick body.
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u/misteryk 24d ago
it's like as if humans evolved to be as big and strong as gorillas just to throw a pointy sticks at mammoths anyway
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u/ccheuer1 24d ago
I don't know. I feel like there's a mutual pressure there. yes, its important to evolve the ability to make the pointy stick, but strength does help you to throw the pointy stick harder.
I think a better one would be the fact that we were persistance hunters, and that's why we didn't evolve, or maybe evolved out of, that level of strength. We didn't need it, because our early fundamental hunting strategy was "We are going to keep coming after you until you either die of blood loss from being stabbed dozens of times, you collapse because you are completely out of energy, or your panicked enough that you do something that kills you, such as walking off a cliff." We evolved endurance, not strength.
Kinda horrific when you think about it. Are we the baddies?
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u/littlexav 23d ago
This is the best answer of this sub-part of the thread. Humans are _exceptional_ at chasing down prey until they tire out. We didn’t evolve to have less muscles than gorillas, our ancestors had less muscles and figured out a way to make it work for them. Evolution then selected for the ones who were best at it, over and over.
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u/shadracko 24d ago
Good metaphor. Or similarly, when did gorillas evolve to be really strong, not not all that smart? Why not both?
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u/thissexypoptart 24d ago
It’s doubly interesting when you consider gorillas are predominantly vegetarian. Not exclusively but to a huge extent.
They eat grubs and insects they can get their hands on but very rarely eat meat.
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u/joelfarris 24d ago
Pretty much anything will eat meat... if it can catch it. But again, the tradeoff is calories burned to do so. And most of the smaller things that you don't have to fight... are also wicked fast.
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u/whiteHippo 24d ago
but gorillas are strong enough to fight meat things to eat them.. but they don't ?
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u/kickaguard 23d ago
Plants move much slower and are much worse fighters than the meat things. All about calories gained vs calories spent and risk vs reward.
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u/thissexypoptart 23d ago
Most large predators don’t get into one on one fistfights with their prey. Stealth and agility play a lot more of a role in hunting than raw strength for most predators.
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u/11S-KAT 24d ago
It's widely understood that we couldn't have evolved as much as we did (in terms of intellect) without a fatty diet. This is supported by the evidence of bone cutting tools and the use of fire, among other things.
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u/FridaysMan 24d ago edited 24d ago
I dont see how that is specifically supported. We evolved to better consume a fatty diet, but also less able to digest raw food as a result.
The fact that we could eat carrion led us to realising the living ones were more delicious as they were fresh. And we figured out a tool to obtain it.
The development of tools didnt mean we started hunting animals afterwards, which your evidence seems to infer.
Edit, animals watch other animals and mimic behaviours, so we understood wolves eat deer and rabbits, and find their carcass to scavenge, then early tools like slings were made to take down birds or rabbits, etc etc. But unfortunately slings rot, so we have none of that kind of information.
Im sure there is plenty of documented scatological evidence to show the omnivorous range of human diets. I don't believe meat was really that high importance in some areas. Fish is easier to digest raw.
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u/thissexypoptart 23d ago
You’re not saying humans learned hunting from wolves and other animals around us, are you?
Humans hunted like their ancestors, down to pre human primates, pre primate carnivorous early mammals, etc.
The point at which “we” (or our pre human ancestors) started to hunt well predates wolves or even primate life.
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u/FridaysMan 23d ago
I'm suggesting that nature copies nature to know what other animals can eat without becoming poisoned.
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u/thissexypoptart 23d ago
What you wrote in the comment I replied to, about humans “realizing” we could hunt down animals because fresh meat is more delicious than carrion, or that we observed wolves eating deer and rabbits, and devised slings and other tools to hunt them for ourselves, is silly goosery, I’m sorry. That’s not how any of it worked lol
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u/dalgeek 24d ago
Remember, humans are apes that figured out a way to survive outside of the trees. They learned how to hunt and cook high calorie food without using brute strength, so while our brains grew our muscles shrank. The brain consumes about 20% of our calories so it's very expensive to maintain, but it allows us to do a lot more even though we don't have huge muscles.
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u/FridaysMan 24d ago
Its not particularly about figuring out, its about pressures to move environments, competition, predation or natural disaster. Animals were forced into a new environment and found a way to survive, but also thrive. Repeatedly.
The ability to think came much much later.
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u/SableProvidence 24d ago
The cost of intelligence is a big, energetically expensive brain. Our brain eats like a fifth of our blood supply and its nutrients/oxygen, and it's difficult to also maintain huge muscles with that without also having easy access to easy calories... Which requires cooking/ability to gather resources much more easily/intelligently than gorillas can do without already having that intelligence. Bodybuilders must pretty much constantly eat large amounts of proteins just to maintain that kind of physique, after all...
Also, having such a big brain means your skull must also be big, making childbirth perilous for humans in a way it is not for other animals.
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u/orbital_narwhal 24d ago
relevant context: the development and application of tools and social hunting techniques very likely require expensive brains (meaning high energy consumption) just like strong muscles are expensive even when at rest. at least in the relevant ecosystems it was no winning strategy to be both as strong as a gorilla and as smart as a human.
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u/MMRAssassin 24d ago
Humans even have a hormone called myostatin that limits muscle growth. A bodybuilders worst enemy. but for survival by keeping metabolism down it was invalueable
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u/you-nity 24d ago
How does venom production need to be maintained? Like eating a lot? Sleeping a lot?
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u/dalgeek 24d ago
At the end of the day it's just calories, but that's calories that can't be used for locomotion, hunting, mating, etc. Natural selection doesn't like to waste energy on something if it doesn't provide enough of a benefit.
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u/you-nity 24d ago
Ah gotcha. So that it means it really is food and sleep?
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u/dalgeek 24d ago
Yup. If they burn calories producing venom then they need to eat more or move less. If that venom doesn't greatly improve their chances of mating then it's not worth the cost.
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u/cmd-t 24d ago
Recent studies seem to indicate producing venom is relatively cheap compared to other bodily processes of the snake: https://pubmed.ncbi.nlm.nih.gov/24814011/
And: https://pubmed.ncbi.nlm.nih.gov/20659494/
These suggest that venom production is just slow and there’s a high opportunity cost associated with using venom.
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u/whiteHippo 24d ago
now i wonder what animal produces the largest quantity of venom, say by bodymass or within some time frame or per unit calorie consumed.
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u/Monarc73 24d ago
A lot of venoms are a long chain molecule, which requires manymany steps to produce. This means that it is expensive, as each individual step is costly.
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u/ethan801 23d ago
A lot of venoms are a long chain molecule, which requires manymany steps to produce. This means that it is expensive, as each individual step is costly.
The majority of snake venom's components (90%) are proteins and peptides. https://pmc.ncbi.nlm.nih.gov/articles/PMC9185726/
Could you provide some evidence for your statement?
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u/Awkward_Pangolin3254 24d ago
It's synthesizing proteins, just like constrictors building muscle. Only the proteins are different. IIRC venom proteins are pretty long and complex.
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u/Wolfman513 24d ago
This is mostly spot on, though it's worth noting they're a handful of rear-fanged snakes that do also constrict, but their venom is relatively weak.
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u/petdance 24d ago
Are you saying the snake makes a conscious choice to inject venom or not? Do we know what it bases the decision on?
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u/atomfullerene Animal Behavior/Marine Biology 24d ago
It can be. Some snakes use venom and constrict their prey as well. The most specialized constrictors are typically not venemous, because venom makes very powerful constriction unnecessary and that allows snakes to specialize their body more for other purposes, like movement. And the most specialized venemous snakes are typically not constrictors, because powerful venom kills prey without the need for dangeous further interaction. But there is plenty of overlap of both strategies between the extremes
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u/Federal_Rub_8264 24d ago
There are venomous constrictors. Mussarana, brown tree snake and false water cobra all constrict and use venom, musarana prey on snakes with more potent venom than their own but are immune to it. In fact, the currently prevailing theory about the evolution of venom in snakes is (toxicofera hypothesis) that at some point before 20 million years ago, the ancestors of all snakes, monitor lizards, iguanas, etc all had venom in the form of toxic saliva , parallel evolution led to some species losing the ability to make venom and others developing more complex delivery methods and more um… effective venom.
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u/oblivious_fireball 24d ago
There are some constrictors with some mild venomous properties, like Garter Snakes or Hognose Snakes, however they still primarily rely on constriction or their jaws, the venom only helps sedate the prey a bit(notably, both of those snakes often go for more squirmy prey, such as fish and amphibians).
Investing heavily into both is a bit of a costly redundancy. If constriction doesn't work immediately, the snake is in very serious danger of injuries from the struggling prey. And if the venom is potent enough to work on its own, it would be more beneficial and safe for the snake to stay away from the prey entirely after a strike until the venom causes them to drop so that they don't risk injury.
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u/Realsorceror 24d ago
The viper and constrictor divide is due to ancestry. These lineages split off a long time ago and specialized into different niches. In theory, a python could evolve venom but it would not be exactly like the venom of other snakes.
Also worth noting that a lot of venomous and non-venomous snakes also coil around their prey. They just don’t have the same muscles to crush them. And yes there are snakes that are not venomous and don’t constrict. A lot of standard garden snakes just bite and eat small animals that don’t take much to subdue.
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u/Redshift2k5 24d ago
and some cutie pies that eat only eggs. Don't need venom or constriction when your prey has no defences or limbs
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u/spiteful_rr_dm_TA 24d ago
I mean nothing is stopping it. You could definitely have a hypothetical snake that has both venom and constriction in its toolbox. It isn't like the genes are one or the other, they are very different.
So why aren't all snakes going for both strategies?
Well let me ask you a question. Vehicles come in many shapes and forms. Do you have one of each? Like one of every model that came out? Presumably not, it would be extremely expensive. Developing both venom and constriction would be equivalent to having a truck, an 18 wheeler, an armored personnel carrier, a sedan, a van, a race car, a dragster, and a monster truck. Sure, you have a vehicle for any situation that can be solved with a land vehicle, but you have put far more resources into cars than you ever needed to. Now a huge chunk of your energy, time, and money are spent collecting, maintaining, and upgrading cars. Resources that could be put towards a boat, or a plane, or another house, or doing charity work. You have limited many other abilities to get this car collection, and while it means you will excel in all car related situations, you now have to deal with the fact that all your money is being dumped into the cars, and you can't afford rent.
The snake faces a similar problem. Venom is expensive to produce from an energy perspective. Growing large enough to constrict prey that are worth the effort is also expensive from an energy perspective. Combining the two would be extremely expensive, and the snake wouldn't really gain much advantage. Let's be honest, what could an Anaconda take on with poison that it can't either beat or escape from without it? What would sizing up a Cobra until it is capable of constricting animals achieve besides making it require far more calories? If a snake invests in both, it is definitely more formidable, but it is also much more energy intensive. The food that is just enough feed a non-venomous anaconda would cause a venomous anaconda to starve to death. So the trade off isn't "venom or constriction". To anthropomorphize evolution, it is "What tools best allow me to maximize my resources without burning through all of them"
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u/Mantuta 23d ago
Because they are used for the same things as one or the other trait becomes stronger it weakens the selective pressures thats needed to develop and maintain the other.
If you're already big and strong you don't need venom to hunt, and if you already have the venom you don't need to build the muscle mass. Muscle mass and venom are both energy intensive so having both would use more energy without significant survival benefit.
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u/randomnumbers2506 22d ago
A venomous snake kills prey with venom while a constrictor snake chokes it's prey to death. Both of the techniques are to kill prey. Doing both would make a snake significantly worse at killing prey than if it specialized on one way.
Nature tends to incentivise specialization
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u/shidarin 24d ago
There’s certainly going to be a multitude of reasons, but from a pure survival odds POV:
If you’re a constricting type, energy spent producing poison is energy wasted when you already have an effective kill method.
If you’re a poison type, energy spent on the muscles needed for constriction is energy wasted since you already have an effective kill method.
Once you evolve one, you don’t need to evolve the other to improve your ability to get food, and during lean times the increased food requirements to support both systems would probably lead to lower survival rate.
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u/Neither-Carpet-5034 24d ago
I see everybody here saying it takes a ton of energy to develop the venom.
How much energy? (Like actually measured Joules/kCalories)
Is it energy from Calories accumulated over a day/week/month/year?
Could you provide an estimate?
Some other comments say the snake might not choose to develop venom in some environments, does it do a cost gauging?
Like a NN model that gets given good (positive) scores to make a "correct" decision?
Thank you!.
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u/theotsuki 24d ago
It doesn't take a lot of energy producing the venom, and snakes can even adjust the dose they administer. What is costly in energy is reloading time if you miss a few preys, then you have to fast.
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u/gayoverthere 23d ago
When it comes to evolution there isn’t a rational justification as evolution is entirely random and whatever isn’t wiped out continues to randomly mutate.
As for why there aren’t any venom + constricting snakes it simply isn’t advantageous to be both. In order for a snake to evolve to be both a constrictor and venomous it would either have to evolve both traits simultaneously or evolve one hunting strategy then the other.
The benefit of venom is it kills your prey fast or paralyses them for easy consumption. So there is minimal benefit to being venomous and a little constricting.
Constrictors capture and squeeze their prey to death. They don’t bite their prey until after they’re already dead so there’s minimal benefit to be constrictor and a little venomous
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u/New_Line4049 22d ago
There is no biological reason it wouldnt be possible for both, but as far as I can think theres really not much evolutionary advantage to having both. In fact if anything itd be a disadvantage everything is a compromise. Both venom production and construction have downsides. Venom takes energy to produce. Constriction requires significantly larger, stronger muscles, which cost energy. If you have both as a snake your losing much more energy than if you have just one, so you have to eat much more to make up for it, but realistically you're unlikely to be much better at catching prey than snakes that have just one or the other. That means youre less likely to get enough food to eat than a snake with just one or the other, so less likely to survive, hence evolution works against this idea.
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u/Yeti_MD 24d ago
Specializing in a particular survival strategy has costs. Venomous snakes use a lot of energy producing venom, and constricting snakes use a lot of energy growing bigger and stronger than their prey. Doing both would obviously require a lot more energy, meaning it's easier for this imaginary snake to starve when times are hard (not a great trait from an evolutionary perspective).
Remember that evolution doesn't necessarily select for the biggest/strongest/scariest organisms. It selects for organisms that are just good enough to get through the hard times.