Bear with me :) The aliens in my story are gastropod-like entities and I would really like them to communicate through the mucus they excrete. What could such communication look like?

Preliminary research into snails, slugs and their friends has turned up no leads, but I'm thinking of a few possibilities:

  • Changing up the chemical make-up of the mucus (perhaps affecting color, temperature, viscosity), carrying meaning
  • Drawing visual patterns
  • Sending vibrations through the mucus layers
  • 4
    $\begingroup$ If you're going to communicate by changing chemical make-up of mucus, you are forgetting about the obvious example: chemicals signals (i.e. smells/pheremones) . That is what ants do. $\endgroup$
    – DKNguyen
    Sep 28, 2020 at 2:12
  • 1
    $\begingroup$ Since you didn't use reality-check... they excrete complex organic molecules that encode information when they want to 'say something'. Others can read these messages. Carbosilicate amorphs can communicate this way. $\endgroup$
    – Matthew
    Sep 28, 2020 at 2:25
  • $\begingroup$ I agree. Insects leave all kinds of chemical trails. Do slugs too? $\endgroup$
    – Joe Smith
    Sep 28, 2020 at 3:49
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    $\begingroup$ maybe through taste? $\endgroup$
    – Li Jun
    Sep 28, 2020 at 8:44
  • $\begingroup$ Re, "communicate by excreting..." There is no communication until you have both a means of sending a signal and, a means of receiving it. How do your alien's friends receive the message? Does he fling gobs of it at them? Do they walk along a trail of it, and taste variations in its chemical makeup with their bare feet? Do they view the slime from a distance, and understand the many-layered messages that are encoded by its squidgy geometric form? $\endgroup$ Sep 28, 2020 at 18:25

5 Answers 5


Slow Down, You Move Too Fast...

We're talking intelligent snail-like beings, so what if they have no audible communication at all? Their civilization values art and visual esthetics. Slime is laid down on paper (originally digested plant matter left to dry, but now made) and since snails are related to octupi, why not ink? The snails are masters of chemistry, and they control the drying process so various acidities and inks stay separate. A statement naturally takes time to dry, acids etch the substrate, and the effects on the paper would include complex watermarks and three-dimensional wrinkling. So that much like calligraphy, slime art-writing is as much about beauty (to a snail) as it is about communication.

Communication by visual manipulation of one's foot and eye stalks, as well as chemical signals, can be used to communicate rapid information. As technology has evolved, snails could stand on pads, sending signals through their foot, laying slime on an electronic detector that rapidly interprets signals. Still, the old, slow ways are best, and such crude communication is considered tactless. After all, who can show the true skill of their artistry through a chemoreceptive PAD? Honestly, the youth nowadays in such a hurry, with their electronic doodads...

  • $\begingroup$ "ascetics" - did you mean "esthetics"? $\endgroup$
    – void_ptr
    Sep 30, 2020 at 5:37

Yes, but it would be such a limiting form of communication nearly any alternative they could improvise – banging sticks on the ground or against their shells, for example – would be more robust.

The downsides of slime

  • Body language would be necessary to signal that one is about to 'transmit' and the intended receiver should be prepared to 'receive'. An intended recipient who isn't present or isn't looking the right direction would be oblivious to this.

  • You can't communicate to more than one receiver at a time, and they must be immediately present and willing to receive. These snails can't shout. An intended recipient who doesn't want to receive the message can simply refuse to track the slime message, and the sender can't override this without physical violence.

  • Receiving a message is labourious: depending on information density you may have to follow in the slime track of the sender, unable to scan ahead.

  • Assuming a linear method of encoding, there can be no interjection, no proper dialogue: A sends in full, B receives, B replies in full, A receives. Literally snail mail.

The upsides of slime

  • The message can endure until the slime degrades or is mechanically disrupted enough to obscure the contents. Bad for privacy, but good for leaving messages to a receiver who isn't yet present.

Improving on the familiar gastropod

Rather than leaving trails in the dirt as our snails and slugs do, your xenoslugs have evolved their organs to fire info-dense packets of slime at each other, with great accuracy over several metres. Much of their exposed tissue is porous and receptive to this, skin composed of tastebud "ears".

As a medium, the complexities of the language could be well outside our capacity to understand. Think polysynthetic, but in multiple dimensions: scent, colour, viscosity, density, chemical reactions, etc. The tiniest squirt could take thousands of words to translate.

This still wouldn't be as good as vocalization in many respects, but orders of magnitude better than slime trails.


I think slime is not an efficient way of communicating, because it will slow down the communication rate, no matter what route you choose.

  • chemical substances: they will need to diffuse in the slime layer of the emitter and then in that of the receiver, plus the time for the molecules to diffuse via the medium, be it air or water. There is a reason why pheromones are sprayed.
  • optical signals: whatever substance you inject into the slime, it will have again to diffuse to become visible, and then whenever you want to change message you will have to dispose of the previous content. If you compare it with the mesmerizing capabilities of an octopus skin, you see this approach will also be not competitive.
  • sound signals: here too, slime seems more of a sound damper than a sound transmitter. And it would require the emitter and the receiver to be in physical contact. Else sound emission directly in the medium would be more efficient.

Probably the only way might be to use the slime as an optically active layer, and change its thickness to alter the diffraction patterns of light. The same way a drop of gasoline on water lets you see a rainbow, by changing the thickness of the slime the creature could modify the diffraction behavior and thus communicate by using it. However this would be strongly directional, which can be an advantage or a disadvantage.

  • $\begingroup$ im not sure i follow slime being a sound damper? generally sound travels better through denser mediums so it should be better than air, there might be problems with it if its just a thin film however $\endgroup$
    – jk.
    Sep 28, 2020 at 9:25
  • $\begingroup$ @jk. sound doesn't travel "better", it travels faster. Refraction while changing medium causes signal quality to decay and depending how it's done can cause a lot of energy loss (hence dampening). $\endgroup$ Sep 28, 2020 at 12:32

They can make piece of thick, nearly solid mucus that they can hold with two appendices. Then they vibrate the mucus. It will work exactly like a guitar string. Think of spiderman making a short piece of web. This produces sound, much like our vocal cords, and they can talk this way.

This approximates human voice very well, i.e.: females and infants would be smaller than adult males, so their "cords" would be shorter and/or thinner thus having a higher pitch. Or you can make the females larger to reverse this and give the species a more alien feel.

They could also stick the mucus to surfaces to make a permanent voice instrument somewhere.

A slug could also make multiple cords to make chords. Or a group of slugs could make a chorus.


To expand on Li Jun's point and a previous answer to a similar question they can transfer fluids with chemical messages close range with body contact. It doesn't have to be French kissing but a form of communication that needs bodily contact or spitting at close range, something like the system Bonobo's have with every greeting being based on touch leading to sexual encounters to affirm a result but it doesn't need to be sexual in their minds. How this translates to a language that can span distances or be passed along in generations without physical touch I dont know but as a personal form of communication this method could work.


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