Although (as far as I've seen, I haven't done in-depth research) the original/older version(s) of the succubus legend just have them as demons who seduce you, more modern interpretations seem to make them reliant on sex to survive.

Is it biologically possible for an organism to need sex to survive? And I don't just mean going mad without it/other mental health issues, I mean actually biochemically needing it for some reason.

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    $\begingroup$ Pon farr is a well-known example, that I don't generally see criticized as unrealistic. $\endgroup$ – Gary Walker Aug 19 '17 at 15:02

Female ferrets

If you don't spay them early then female ferrets must mate every time they come into heat or they die.

Unless they are going to be used for breeding purposes, female ferrets will go into extended heat and a female that will not mate, without medical intervention, can die of aplastic anemia. It is possible to use a vasectomised male to take a female out of heat.

So yes, entirely possible for an organism to have a biological need to mate, though unusual. (I'm not aware of another example.)

  • $\begingroup$ How/why did this behaviour develop? Is it just to control when ferrets breed? $\endgroup$ – C. R. Yasuo Aug 20 '17 at 14:25
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    $\begingroup$ @Calllack, you'd have to consider why it would be a reproductive advantage, possibly low wild population density meaning that the fertile period would be missed if it wasn't extended. Females remaining in heat longer would have a higher chance of reproducing. $\endgroup$ – Separatrix Aug 23 '17 at 12:48

Many animals have a pre-ovulation phase, commonly called "heat", marked by profound metabolic changes.

In some animals copulation triggers actual ovulation (it has been proposed, I don't know with what confidence, that human female orgasm is a "leftover" of such mechanism, now dismantled in our species).

Some mammals will remain in this altered state (i.e.: in "heat") indefinitely if no sex is allowed.

"Heat" condition is already somewhat stressful for the female (sometimes very stressful); all you have to do is to make it actually dangerous for health and fatal if prolonged. Something like impairing digestion or something along the lines, so that death is a sure outcome, but different individuals can withstand it differently.


While no such organism exist I could imagine one. There are species where the male takes over all food gathering during the reproductive period. Lets take that to an extreme: Ejaculate is actually pretty good food, albeit in far too small a quantity to be worthwhile. Suppose a species developed a way to absorb the energy. The males that produce the most have the advantage because the absorption ability is limited, some sperm survive. More absorption, more production, the cycle continues until the female lives on sex.

  • $\begingroup$ Actually I was thinking of this at first but it seemed ridiculous that something could get nutrition from that. $\endgroup$ – C. R. Yasuo Aug 21 '17 at 17:06
  • $\begingroup$ @Calllack I don't think it would be that hard. The vagina can already absorb some things (consider Nuvaring contraception--basically a month's worth of BC pills in a time release dispenser that's worn in the vagina.) Once there's a sliver of functionality evolution is good at making it bigger. $\endgroup$ – Loren Pechtel Aug 22 '17 at 1:40
  • $\begingroup$ @Loren_Pechtel So the ejaculate would just evolve to contain all the necessary nutrients/minerals for survival? Huh. $\endgroup$ – C. R. Yasuo Aug 22 '17 at 9:05
  • $\begingroup$ @Calllack Exactly. $\endgroup$ – Loren Pechtel Aug 22 '17 at 18:43

The only thing I can think of is survival sex, the prostitution of one's self in order to obtain cash or food etc which is common in almost every nation on Earth amongst impoverished peoples. Thus a non human creature could also sell itself sexually to other beings presumably of the same species in order to obtain food and/or other vital resources in exchange.

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    $\begingroup$ I think that, while your answer is tecnically correct, it is out of the scope of Callack question. Every animal we know dies if it cannot eat or breathe. Trading sex for food would, at least, require sentience and an adequate social structure. $\endgroup$ – Liquid - Reinstate Monica Aug 20 '17 at 12:16
  • $\begingroup$ If it is technically correct then it cannot logically be out of scope. $\endgroup$ – Simon Bainbridge Aug 20 '17 at 12:25
  • $\begingroup$ The question is asking about an organism being biologically dependent on sex, not economically dependent. That makes this answer off-topic. $\endgroup$ – Philipp Aug 20 '17 at 12:53
  • $\begingroup$ I can see where you're coming from, Simon, but the others are right in that this isn't what I was looking for. $\endgroup$ – C. R. Yasuo Aug 20 '17 at 14:04

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