The sand worms in Dune are gigantic creatures. Confirmed sizes reach up to 450 meters long. And in the wiki it says "Some people believe that worms from 700 to even 1000 meters existed in the southern pole regions, but this could not be confirmed"

In all cases the sand worms are huge. They are territorial and defend their territory against other worms, which makes sense. They also attack spice harvesters which also makes sense because those things are big and loud. Same with ornithopters or large things in general. It is conceivable that large things could be considered potential adversary or predators. Alright.

However humans or human sized creatures or noise also attract the worms? Which I'm not sure makes much sense. It's like a lion or rhino rushing to defend their territory from...a mouse or pigeon. What?

I understand they are a bit mysterious and I'm not saying it's done badly in the book or anything similar.

I'm talking about humans without shields, since they are driven mad by shields. Also they don't actually eat humans or metal contraptions. About their diet:

The main component of the sandworm's diet was sand, and other inorganic and dry components of the Arrakis crust. It is also believed they sifted the sand-plankton for nourishment.

I'm just asking: Is this behavior biologically probable/possible if they existed and followed laws of biology without any mysteries, would they still want to attack humans, human sized, and possibly smaller sized creatures? If it is possible then why?

  • $\begingroup$ Hunters We call these creatures in Dune "worms", but the species originated from large underground predators. Leto succeeded in taming one. Any sound or movement near the sandworm will set off their hunting instinct. $\endgroup$
    – Goodies
    Nov 21, 2021 at 12:03
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    $\begingroup$ Well, there is a size limit to what they'll go for. They notably don't waste their time on, say, the little hopping mice that we know exist in the desert (Paul ends up being named after them by the Fremen). Besides being much smaller and quieter, the mice have learned (by accident or natural selection) to walk in a non-rhythmic manner, so they don't draw the attention of the worms. $\endgroup$ Nov 22, 2021 at 14:32
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    $\begingroup$ Where do you get "they don't actually eat humans or metal contraptions"? The quote just says this is not the main component of their diet. Maybe they love eating humans and machines, it's just that those are rarely available? $\endgroup$
    – usul
    Nov 22, 2021 at 15:00
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    $\begingroup$ I'm just waiting for someone to explain how walking on sand, which already has a massive damping effect, could possibly transmit vibrations miles away in a strong enough manner to catch the attention of a beast a third a mile long. It'd be like squeezing a water dropper over the ocean to attract a blue whale miles away. $\endgroup$
    – Mordred
    Nov 22, 2021 at 21:23
  • $\begingroup$ They just want to kill humans beause they hate them. As soon as you assume some higher consciousness you don't need fancy biological reasoning and no mistery. Just a big evil sandworm. $\endgroup$ Nov 23, 2021 at 10:11

4 Answers 4


They don't want to attack, they want to investigate.

It's just that their preferred method of investigating is a bit destructive.

You see this all the time in reports of shark attacks. Usually the shark isn't actually attacking, as such, with the intent to eat or kill or even drive away the human. They're just curious. But a shark's eyesight isn't very good, and its senses in general are geared more towards telling it where things are than what they are. So to investigate things, sharks like to go up to them and feel them, get a sense of their shape and taste. Since they have no hands, the best way to do that is with their mouths.

Baby humans are the same way; they often stick things in their mouths because they're curious about them, and their other senses aren't as refined, so this is the best way to find out what something is.

Sandworms, well, they don't have hands or any manipulators at all (that I'm aware of). Their senses, other than their tremor-sense, are probably not that acute. I've always sort of assumed that they're blind; it's not like sight would be very useful underground, smell likewise.

So they aren't really driven by aggression, but rather curiosity at what these small moving things are. But in order to find out, they need to go up there and touch them - and to a human, the difference between a 500-meter, umpteen-hundred-ton sandworm getting close to you out of aggression or out of curiosity is pretty academic. You're likely to end up dead either way.

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    $\begingroup$ While interesting it's not supported by the evidence. First the very small triggering points makes no sense. It's like a shark investigating a gold fish thrown in the water. Second is that they 100% attack and "eat" things. From thopter to harvesters to humans. It's not like they get close, sniff around, then leave if there is no danger. They go in and swallow everything $\endgroup$
    – Seallussus
    Nov 21, 2021 at 3:34
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    $\begingroup$ "It's not like they get close, sniff around"... now look, if you're already around, you just can't refuse a piece of organic matter, not like Arrakis offers them plenty of protein. $\endgroup$ Nov 21, 2021 at 7:09
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    $\begingroup$ @Seallussus: If they're primarily filter feeders, they're not wasting any energy following the sounds. They're feeding all along the way no matter which way they go. $\endgroup$ Nov 22, 2021 at 2:50
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    $\begingroup$ The irregular gait of the fremen were suppose to mimic the natural sounds of the desert. its the regular footsteps of people that attract the sandworms. This does support the answer somewhat as the regularity of the sound is unusual and is what is being investigated $\endgroup$
    – Alex
    Nov 22, 2021 at 9:04
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    $\begingroup$ @Seallussus If you want an answer backed up by canonical evidence (either directly from the books, or reported by someone who's officially connected to the books in some way) then you might want to put a question on the SciFi StackExchange instead of WorldBuilding. $\endgroup$ Nov 22, 2021 at 15:16

We don't know much about the sandworm's diet (from https://dune.fandom.com/wiki/Sandworm):

The main component of the sandworm's diet was sand, and other inorganic and dry components of the Arrakis crust. It is also believed they sifted the sand-plankton for nourishment.

What we do know, however, is that they primarily feed on "inorganic components". There's also a hint there that they sift the sand-plankton. So what we have here is an organic creature which subsists largely on inorganic matter and a sparse diet of organic plankton. It is safe to assume that some organic matter is also necessary for their survival, which supports their also eating plankton and is also a good reason for them to jump at any chance of getting a meal, no matter how tiny. After all, if their primary source of organic matter is plankton, a human would be a feast!

It therefore makes a lot of sense for an enormous creature living in a desert, an area where organic matter will be very scarce, to jump at any chance of supplementing its diet with a more substantial meal. Since they would only get such chances relatively rarely in the barren desert environment, they have evolved to be very sensitive to any kind of movement, no matter how small, since that would mean organic matter to eat.

I would imagine the likeliest scenario would be that while they can metabolize sand and other inorganic matter to make the majority of the essential chemicals they need, there will be others that they can only obtain by eating living creatures. This is the case with many life forms, including humans: we can metabolize our food into most of the things we need for life, but we also have things like the essential amino acids that cannot be synthesized by our bodies and which we need to obtain from our diet.

We only need trace amounts of these chemicals in our diet, so it could very well be the same for the worms: they only need a tiny amount of whatever it is that organic matter provides them with, so even the tiniest morsel, such as a human, is worth the effort given that opportunities to consume organic matter and supplement their diet are few and far apart.

Unfortunately, although the above may be plausible in theory, the same Wiki page I quoted about the worm's diet, also claims that:

Water was fatal to a sandworm, even in small doses. Water that entered a sandworm's body would act as catalyst to accelerate its metabolism to the point that it became unstable and its vital biological functions failed.

This would mean that eating a human or any other Earth life form would kill the worm. This means that they also can't eat the spice harvesters since they contain humans and, therefore, water both from the human bodies themselves and the supplies they would presumably be carrying. Some sort of handwaivery will be required...

  • $\begingroup$ This is a good idea. Sadly, like you quoted, it might be a problem. However the harvester is not an issue. The worm probably does not know that it contains humans. It's not like worms have x-ray vision. Though I imagine that with time they will eventually evolve to maybe attack it without eating it, or find a way to handle that. Like evolution should be capable of handling that. $\endgroup$
    – Seallussus
    Nov 22, 2021 at 0:06
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    $\begingroup$ While humans are like 70% water, most of that water is no in pure H2O so maybe that's where the handwaving can start? $\endgroup$
    – Tom
    Nov 22, 2021 at 7:59
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    $\begingroup$ To a 300 meter long animal, "small" might have a different connotation than what you would consider described by that term. Also, Herbert was not a biologist and there's a lot that's hand-wavy in his worldbuilding, so it probably has the same reason as the idea of the Super Persistent Predator: the writer doesn't know (or care) about details such as that. $\endgroup$ Nov 22, 2021 at 16:22
  • $\begingroup$ One assumes that a several hundred meter worm has some tolerance for wet flesh even if it doesn't like it much. Logically a worm on the surface at night would accumulate some dew from the air, so they must have some low tolerances and a little water isn't entirely fatal. $\endgroup$
    – Ruadhan
    Nov 22, 2021 at 16:22
  • $\begingroup$ @Tom if H2O is toxic, then a solution where the solvent is H2O is also toxic, that won't be a problem. Or, well, I mean, it will be a problem to the worm :) $\endgroup$
    – terdon
    Nov 22, 2021 at 16:40

The worms think little things might be big things far away.

It can happen. If I hear a noise it can be hard to tell if it is something very loud and distant, or something quieter and nearby. I can walk towards the noise. If it is still not very loud and I find it, then it is quiet and near. If I keep going and it gets louder and louder, it is something loud farther away. No way to know except to head in the direction of the sound.

That said, there can be tells. Lower frequencies travel farther. If I hear a song with no high frequencies it is probably coming from a concert in the park, not my neighbor. But maybe the sandworms can't tell.

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    $\begingroup$ I think it's a good idea. But won't the expenditure of energy be unrealistic for creatures "adapted" to the desert? Even without desert. To merely investigate even the smallest actions on noises is to be forever on guard, forever spending energy chasing threats, real or imaginary. That does not seem to be inline with biology. Again it's like a wolf being attuned to hear butterflies then go investigate the noises they make. Not sure if spending so much energy makes sense. Unless everything around the warm evolved to be like that. However the wiki said they are the ones to evolve. $\endgroup$
    – Seallussus
    Nov 21, 2021 at 3:40
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    $\begingroup$ You are right about energy. I had to suspend by disbelief as regards energy budgets for the sandworms, in about 4 different ways. But the sandworms don't investigate everything - the Fremen can fake them out with their funky walk. They investigate rhythmic things like thumpers or aircraft . Maybe rhythm means more than amplitude as regards significance of signal? $\endgroup$
    – Willk
    Nov 21, 2021 at 3:48
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    $\begingroup$ Perhaps the worms would benefit from a lesson from Father Ted? $\endgroup$ Nov 22, 2021 at 10:17
  • $\begingroup$ Along this thought. The worms are noted to be highly territorial amongst themselves. Each Worm controls a territory of potentially hundreds of kilometers and vigorously drives off competitors. It stands to reason then that any large rhythmic noise in the desert is probably another worm and therefore merits an aggressive response. Mix that with the thought that a small rhythmic noise in the desert is presumably a big thing further away and you still get the same response from the worm. $\endgroup$
    – Ruadhan
    Nov 22, 2021 at 16:20

Evolutionary arms race. Big things on the surface learn to make smaller noises. Worms learn to detect smaller noises. This presumes there is an evolutionary advantage for the worms to detect and eat things like humans, which is defended in another answer.


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