A question on venom-spitting and size

[someone_else]

The average spitting snake can spit its venom with at best 2.5 meters of range, if I scale up the spitting apparatus and venom glands (and/or the snake) to twice or three times, how increases the range?

I ask since scaling isn't a linear affair most of the times.

Wikipedia says that it isn't exacty a "spit" but a tiny spray of venom through modified fangs, and that the amount of the spitted material is pretty low (it can shoot venom for 30-40 times and still have enough left for a deadly bite).

[xthetenth]

Hmm, I'm not 100% sure. I think if material strength is no concern, the ability of the muscles to contract and the volume of the sac should determine the pressure. If the muscles could hypothetically compress the entire sac, then I think their ability to provide pressure should also scale roughly with volume, and their ability to provide pressure should be the main determinant of range. The fangs would be the main other determinant of velocity, and since the key bit is the size of the holes, and those scale with the square, so I think we're looking roughly with linear scaling with size, but I'd think compressing the sac would become more inefficient, and the tissues would be under more strain, so worse growth than linear or maybe linear with a cap on it seems rather likely. I'm guessing and don't have tons of practice in this kind of thing, but I think that's a decent estimate.

[Simon_Jester]

Yeah. The fact that there aren't any large animals with venom-spitting abilities is probably a tip-off that this kind of thing doesn't scale well.

In fact, it's not just spitting; venom in general doesn't scale well. Large wild animals are rarely poisonous, because poison is most useful as a defense strategy against predators who would otherwise be able to overpower you easily. If you're too small to outrun a predator (because you're tiny and they're a bird, or because you're small and they're a large land animal that has much longer legs than you), and you can't just scurry down a hole to avoid them, being poisonous is about the best defense you're going to get.

If you're an animal that can reliably beat up other animals by brute force, or at least threaten to maul them enough that they'd rather eat something less ferocious, you don't really need venom.

[TOSDOC]

Good answers--I'd like to add one more. Remember the effects of the venom itself. The main purpose of spitting venom is as a deterrent, to attempt to blind and/or keep away an attacker. It is harmless to the skin, and has to get into the eyes to be effective. Depending on the venomous animal, venom may cause tissue necrosis, paralysis and/or disseminated intravascular coagulation and vasculitis, but only if it is injected. (http://en.wikipedia.org/wiki/Spitting_cobra). If you scale up, does your hypothetical animal really need to be fire-hosing its prey down with a couple of hundred gallons of venom from 150 feet? They may be blind, but is that all the effect you wanted it to achieve?

Sounds like another SyFy movie to me.....

[Simon_Jester]

A large ambush predator might benefit from jumping out of cover and spraying down a large prey animal that way- blinding it with a few gallons of liquid from a considerable distance. That would leave the prey largely defenseless and unable to run away effectively.

EDIT: But since large ambush predators in real life tend to be perfectly capable of sneaking up to animals in the open and physically pouncing on them to kill them, being a giant venom-spitter might not help all that much.

[LadyTevar]

If you simply want a large poisonous animal, you can look at the Komodo dragon. Their mouths are so nasty with bacteria any bite they give will kill over time. They use that to hunt the wild goats on the island. If the goat survives the attack and escapes, it will still be poisoned from the bite. All the komodo has to do is track it down and wait for the goat to be too sick to run.

[Wing Commander MAD]

If you simply want a large poisonous animal, you can look at the Komodo dragon. Their mouths are so nasty with bacteria any bite they give will kill over time. They use that to hunt the wild goats on the island. If the goat survives the attack and escapes, it will still be poisoned from the bite. All the komodo has to do is track it down and wait for the goat to be too sick to run.

Actually, Tev they are venomous. I believe it was discovered in the last couple years. How exactly they missed that in all the time we've know about them and all speciments no doubt dissected , I've no clue. Maybe if we're lucky Alyerium will show up, this is after all right up his alley.

[madd0ct0r]

Is this related to space-marine being able to spit venom/acid?

I think the range won't scale up linearly, unless you're squirting a jet of liquid.

if it's a cloud, like an aerosol, then the volume of liquid would scale to the cube of the range.

[Alyrium Denryle]

Like anything else, it will depend on the venom delivery apparatus. A spitting cobra basically has a hypodermic needle with a forward facing aperture. So, it will depend on what gets scaled. If the compression ability does not change, but aperture size does, then I would expect that the pressure would be inversely proportionate to the cross sectional area of the aperture. The flow rate I imagine is proportionate to the square the compression muscle diameter, while inversely proportionate to the cube of the increase in gland diameter...

Of course range depends on exit velocity and thus one can consult Newton for that.

So V=(cD1^2/D2^3)/A where c is a coefficient of some sort, D1 is the diameter of the compression muscles, D2 is the diameter of the glands and A is the cross sectional area of the aperture.

In fact, it's not just spitting; venom in general doesn't scale well. Large wild animals are rarely poisonous, because poison is most useful as a defense strategy against predators who would otherwise be able to overpower you easily.

Venom generally evolves as an offense to help subdue and digest prey. It is used secondarily for defense. Large venomous animals were once relatively common. The entire genus Varanus apparently has some toxins, Komodo dragons, in addition to their saliva for example have a pretty powerful coctail of hemotoxins... and there were once 20 foot long Varanids. Some of the early synapsids (the proto-mammals that ruled the earth in the Permian) had a venom delivery systems in their teeth, and these things were the size of modern lions.

[Simon_Jester]

I sit corrected.

Then again, if large venomous animals were once relatively common... what changed?

[Alyrium Denryle]

I sit corrected.

Then again, if large venomous animals were once relatively common... what changed?

Well, the permian extinction happened... and in australia, placental mammals happened. proto-Aborigines were hunted by those giant monitors for a while.

[Andehtron]

Should this be in SLAM?

[Alyrium Denryle]

Should this be in SLAM?

I think it ought be, yes.