The creature in question is this one from "The Man Trap". I almost got the sense that despite its ability to assume the shape (or mentally project the illusion) of humans it may not have been sentient although that is hard to understand since it spoke, etc.

Was it implied that it, being not truly intelligent, could not control itself? We know that the salt does not have to be directly from a human body since they were able to lure it with table salt (using the futuristic salt shakers that were apparently found at a local store).

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    It's a monster, not a misunderstood alien trying to make its way in the universe.
    – Valorum
    Commented Jan 14, 2021 at 22:14
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    Crater says: " It doesn't trick me. It needs love as much as it needs salt. When it killed Nancy, I almost destroyed it but, it isn't just a beast. It is intelligent and the last of its kind."
    – NKCampbell
    Commented Jan 14, 2021 at 22:26
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    Well, the Ryder character lived with it for years and they mentioned that it was the last of its kind, like the buffalo I think they said. So it was a member of a species, not an anomalous monster. I think there were ruins on the planet of structures this species had built.
    – releseabe
    Commented Jan 14, 2021 at 22:26
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    You may want to edit your edit to make it extra clear that it is a fan fiction alternate plot to make it more dramatic. As obviously the actual episode didn't have those elements. Further in the context of the Devil in the Dark or TNGs crystalline entity- starfleet can forgive an awful lot to move past a misunderstanding. Commented Jan 15, 2021 at 1:37
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    @lucasbachmann The edit is unneeded commentary more appropriate for a discussion forum but doesn't fit here on SFF, a question and answer site; I've removed it. releseabe you have a habit of editing to add discussion in replies to answers and I've commented on this before to you, please don't do it. If you want a place that offers discussion check out this meta post or find an alternative site for that. At the very least put it in the comments, not in edits to the question.
    – TheLethalCarrot
    Commented Jan 15, 2021 at 10:07

3 Answers 3


In universe, the explanation is necessarily a little convoluted:

Presumably, the Federation would want to preserve and study the sole survivor of an intelligent alien race; supplying it with salt would not be a problem. The initial reason this didn't happen is that Crater wanted to keep the true nature of the creature a secret, so he can continue living with it as the image of his dead wife, which would not be possible if it became a subject of Federation scientific interest/diplomatic relations. Crater's plan was just to get a good supply of salt from the Enterprise without attracting too much attention and then continue his isolated existence on the planet. It's not clear whether the creature is really on board with Crater's plan; it might be drawn to the idea of the rich hunting grounds on the Enterprise and the other planets to which the Enterprise might unknowingly transport it. When the creature starts killing crew on the planet, it might be out of simple hunger or it might be part of a plan to get to the Enterprise with an assumed identity.

On the Enterprise the creature, while intelligent, is unable to control its appetite. It never appears to be able to communicate "honestly", without assuming the role of the person it is impersonating. In the final confrontation where it is clear that feeding on Kirk would lead to its certain death, it still cannot refrain from feeding on him.

So the creature and the species it represents perishes when it might've been preserved, through a combination of Crater's grief-stricken selfishness, Kirk's righteous fury at the death of his crew, and the creature's inability to control its appetite. Note that the fatal flaw of an uncontrollable appetite is a staple of the vampire trope that the episode references.

See also the fate of the phosphorous-beast Coeurl in A. E. Van Vogt's Black Destroyer.


[Short version - the episode implies it was starving from long term rationing of the salt supply.]

When the salt vampire impulsively killed that blue shirt crew member it forced a pattern of deception that kept escalating until it was destroyed.

It was smart enough to not kill its last large meal, Professor Robert Crater, it clearly was living on table salt or brine. But as a predator it still instinctively chose to kill Darnell when it had the opportunity. They were extremely low on salt tablets so the salt vampire may have been eating a bare minimum for quite some time - such that it let its instinct to hunt take over when the Enterprise did a status check. Just how close it was to starvation is seen below. (Of course like most tumble weed TOS planets we have to also assume there's not much to hunt as it's a bit of a desert)

From transcript at Chakoteya, "The Man Trap":

CRATER: (opening storage box) Nancy and I started with twenty five pounds. This is what we have left. (a few tablets at the bottom of a jar) Now what is so mysterious about that?


As antlersoft implied in his answer, the Salt Vampire was obviously inspired by Coeurl in A.E. Van Vogt's "Black Destroyer" (1939).

And the odd thing about Coeurl is that there are two somewhat different versions of Coeurl.

A.E. Van Vogt wrote several stories about the harrowing adventures of the crew of the Space Beagle and eventually he rewrote all of them as part of a "fix up" novel, The Voyage of the Space Beagle (1950) with a new character as the protagonist.

Coeurl is different in the two versions. In one he has suction cups on the ends of his large tentacles, in the other his large tentacles divide into smaller, finger-like tentacles. In "Black Destroyer" Coeurl needs the chemical compound phosporus to survive, in The Voyage of the Space Beagle Coeurl needs the chemical element potassium to Survive.

As far as I remember from a recent rereading of "Black Destroyer" Coeurl was a member of the civilzed species which left the ruins on the planet. But as far as I remember from reading The Voyage of the Space Beagle long ago, there was speculation that the Coeurls might have been an artificial species created by the biological science of the natives of the planet, perhaps created as some sort of biological weapon. Coeurl was an intelligent being with some knowledge of technology in both versions.

So I have to wonder whether George Clayton Johnson, writer of "The Man Trap", and the production staff, were more inspired by "Black Destroyer" or by The Voyage of the Space Beagle, and whther they considered the Salt Vampire to be the same species as the natives who left the ruins or a member of another species, a species which might have exterminated the natives.

In the second case the Salt Vampire would not have to be as intelligent as the builders of the ruins, though it might be. I note that the Salt Vampire wears clothing of a sort in its true form.

I have woundered whether Salt Vampires were created as a biological weapon to seed on a planet and kill off the native intelligent life, and then die off from lack of salt before their creators colonized the planet. If Salt Vampires were seeded on several planets that might explain why Trelane had a Salt Vampire statue or mummy in his place. I have also wondered whether Klingons might have been created as cannon fodder by another species who they later turned upon.

There is a thread at the Trek BBS discussing why didn't they just give the Salt Vampire table salt:


  • interesting that it may have been an artificial bio weapon -- but if this is speculation not in story and is post-Alien, maybe that is where they got it from. and the trekbbs link does not work -- maybe they died from lack of salt?
    – releseabe
    Commented Jan 15, 2021 at 18:31
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    this is all speculation - unless there is any indication that the story was indeed inspired by those other works (if so, it wasn't referenced in the "These Are the Voyages" book
    – NKCampbell
    Commented Jan 15, 2021 at 21:33

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