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Thoughts on Zombie eating habits
Bar Harbor
alexx_kay
What with one thing and another, I've been exposed to a bunch of zombie stories lately. Many of these, especially the classic Romero model and the more recent Walking Dead version, deliberately eschew any explanation of why there are zombies or how, in a technical sense, they function. I understand their artistic reasons for doing so, but there's a part of my brain that can't resist trying to find explanations anyways.

[I discount 'explanations' such as "magic" or "Satan", as being both out of character with the stories I'm thinking of, and also as merely moving the fundamental questions back one layer.]

The biggest question, to my mind, concerns basic laws of physics: where do zombies *get* the energy that powers their shambling? Some of these stories are set many months after the zombie apocalypse, yet we see no significant diminution in the ranks of the undead. Whatever keeps them moving seems to be pretty sustainable.

Most animals power themselves primarily by eating. The eating habits of zombies, however, do not seem sufficient for this, at a cursory overview. Zombies eat, apparently exclusively, the flesh of living human beings. But after the first hours of the outbreak, the zombies so far outnumber the living that this is clearly not sustainable as a primary energy source.

One aspect that seems odder the more I think about it is that zombies are *never* portrayed as eating other zombies. Even when a zombie has been 'killed' with a headshot, other nearby zombies show no interest in eating its flesh. Why not? It's probably got similar nutritional value to that of living humans. But they never seem even remotely interested.

Perhaps the flesh is not actually the point. What does a living human have, that a zombie doesn't (and thus, presumably wishes to consume in some fashion)? Two things come to mind: sentience... and *pain*.

Perhaps these zombies are actually being animated by extra-dimensional Lovecraftian entities along the lines of those portrayed in Charles Stross's "Laundry" stories. They don't want to eat your flesh, per se, they just want to *hurt* you. They are not, themselves, what we would recognize as sentient, but they are capable of 'driving' a brain that isn't occupied by a living mind. They don't 'know' enough to use guns or knives, but they can activate the host-brain's instinctual attack mechanisms, which feature biting as a significant component. The pain of a sentient mind is what they feed on.

Is this enough to explain the ongoing zombie hordes, and all their energy expenditure? Not entirely, but I think one more guess will bring us a lot closer. If the zombies are being animated from outside, then they aren't necessarily animated *all the time*. Which actually fits the portrayed stories surprisingly well. Often, a group of survivors will arrive in a new location, and it seems entirely zombie-free. Perhaps during early explorations one or two zombies may suddenly lurch out of dark corners and attack, but there don't seem to be any zombies actively shambling about. As the survivors stay in one place, however, active zombies *do* begin to appear; at first a few, but in ever-increasing numbers, until the survivors are overwhelmed or flee. Perhaps this is because the place was full of corpses all along -- but they weren't being animated. Perhaps there was a tiny energy investment in preventing decay, but that could plausibly be quite small. It's only after the introduction of potential 'food', that the zombies begin to be re-animated. Hence, we don't have to explain how millions of zombies can be active for months or years, we just have to explain how any given zombie (out of a potential pool of millions) can be active for a few days or weeks. Heck, maybe they're just burning stored cellular energy from when they were alive, and there *isn't* any new energy input into the system.

Aside from newly-turned zombies, of course. Which, in this model don't need to have any pre-mortem exposure to any sort of infecting vector. Indeed, the mythology of the zombie bite carrying zombie-ism may be a simple mistake. Being bitten by a *living* human is actually one of the most dangerous things that can happen to you, in terms of infection and disease. It seems likely that the bite of a zombie isn't going to be *safer*. So, if you get bit, there's a good chance that you'll die from it, but not directly from zombie-ism per se. Not that that's any consolation.

[As ever, my ideas are freely offered to the universe; feel free to use them if you like.]

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Are zombies cod-blooded? That would greatly reduce the energy requirements.

Presuming that's a typo (fish for blood would do strange things indeed!), it seems a reasonable possibility.

The one zombie story I can think of that features zombies in a significantly cold climate (the film Dead Snow) has zombies with a clearly magic-spell-based origin, and thus not the sort I am mainly discussing here.

Itty-bitty tiny fish...

Do zombies breath? I supposed they must in order to moan "braaaaiinnnnzzzz," but I'm thinking cellular function is minimal.

The zombies of which I am writing do not say "braaaaiinnnnzzzz", or anything else. There is occasional moaning and growling, but nothing coherent.

OOO! OOO!

hoppity hoppity hoppity hoppity hoppity

Read NIGHT ON MISPEC MOOR by Larry Niven.

Beautiful explanation and rendering.

Perhaps these zombies are actually being animated by extra-dimensional Lovecraftian entities along the lines of those portrayed in Charles Stross's "Laundry" stories. They don't want to eat your flesh, per se, they just want to *hurt* you. They are not, themselves, what we would recognize as sentient, but they are capable of 'driving' a brain that isn't occupied by a living mind. They don't 'know' enough to use guns or knives, but they can activate the host-brain's instinctual attack mechanisms, which feature biting as a significant component. The pain of a sentient mind is what they feed on.

That still doesn't work, as described. Your extra-dimentional horror is driving the brain. The brain dives somatic nerves, which fire and cause muscles to move...

But that muscular movement still needs chemical energy! That your horror gets fed off the fear and pain is nice, but you've not yet shown how that gets fed back into the zombie to keep it shuffling around.



Edited at 2013-03-31 07:42 pm (UTC)

Hence my suspicion, late in the post "... maybe they're just burning stored cellular energy from when they were alive, and there *isn't* any new energy input into the system."

Or maybe there is some mechanism by which these creatures can pump useful quantities of energy across the dimensional barrier. But I don't have any good ideas what such a mechanism might be.

Humans don't have huge amounts of energy stored up, which is why most folks kick the bucket after a month without food. So, your zombie is going to shuffle around for maybe that long, and then fall over.

And, using what energy is stored in your body, you still need to breathe - your normal metabolic processes require oxygen in copious amounts. That means it still requires your blood to pump. And you need to drink water to expel some of the resulting metabolic wastes in urine, or you'll be dead in a matter of three or four days. It has to breathe, has a beating heart, and has to drink water? Doesn't sound much like a zombie any more.

And, "pump useful quantities of energy across the dimensional barrier," sure sounds like, "magic," to me. YMMV.

"So, your zombie is going to shuffle around for maybe that long, and then fall over."

Hence my (I think) significant insight that most zombies *aren't* shuffling around, most of the time.

I don't have any problem with zombies that breathe and pump blood (while active). They traditionally do moan, which (lightly) implies breath. When punctured, liquid blood comes out, though they don't seem to ever have bleeding wounds (super-fast clotting?). Metabolic waste buildup may be a valid counter; I don't have enough information. In what ways does it (in the living) interfere with functionality enough to cause death? Are those still relevant once undeath has already occurred? I expect they would be in the long term, but I'm already speculating an un-lifespan limited to about a month.

"And, "pump useful quantities of energy across the dimensional barrier," sure sounds like, "magic," to me. YMMV."

Yeah, that's why that argument didn't make it into the main post :-)

Hence my (I think) significant insight that most zombies *aren't* shuffling around, most of the time.

So they're ambush predators, like crocodiles.


Hence my (I think) significant insight that most zombies *aren't* shuffling around, most of the time.

I don't have any problem with zombies that breathe and pump blood (while active).


Well, the nervous tissue in the brain needs a constant supply of energy and O2 to keep operational. You can slow it down some, but you can't stop it entirely. And, as a mammal, the body temperature needs to be kept up as well, or the system as a whole will fail. Same goes for the immune system that hold back rot - though for the common zombie that's not working too well, so we can give a pass on it.

You can posit that the horror is somehow such an expert in human physiology that it can manage to slow down bodily processes like an expert in meditation and body control, I guess.

But then we hit the point where this fails to match the literature. Zombies are *untiring*, inexorable. But if you're using the body's original metabolic processes, that zombie will not be untiring. While it may not feel pain, or need to sleep, it will still have limits in how much effort it can put out per unit time.

I daresay that, given their lack of analytic/tactical ability this implies the easiest way to deal with such a zombie would be to find a way to trick or drive them to exhaustion, and then pick them off when they're collapsed and twitching on the ground from lactic acid buildup. Imagine something like a greyhound track - make the zombies follow bait until they simply can't walk any more.

We are converging on agreement, I think :-)

The texts I am concerned with *imply* that zombies are untiring, but they don't actually *show* it at length. It *is* shown in detail that they don't feel pain, and I expect that also applies to the pain of lactic acid buildup.

"it will still have limits in how much effort it can put out per unit time." Yes, but those limits are pretty high. Humans are capable of extraordinary feats of strength given sufficient motivation -- though such feats often cause lasting damage in the performer. Given that the parasite doesn't care about damage to any particular host-corpse, the appearance of inexorable strength is unsurprising.

The greyhound track idea is interesting, but only "easy" from the PoV of people who have safety and time to plan, plus lots of behavioral data to analyze. Most survivors don't live long enough to come to these sorts of conclusions.

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