The peniform clitoris of the spotted hyena, reconsidered

(writing in progress)

Everyone knows that the spotted hyena (Crocuta crocuta, https://en.wikipedia.org/wiki/Spotted_hyena) is odd in having a peniform clitoris.

The usual interpretation is that this allows females to emulate masculinity in a society that is matriarchal to an unusual degree among mammals. Or, more particularly, that females have converged with males by having extremely modified genitalia. In various publications the view is taken that the spotted hyena shows ‘sexual monomorphism’ (https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1439-0310.1986.tb00570.x#:~:text=Abstract,clitoris%20closely%20resembling%20a%20penis and https://www.researchgate.net/publication/230213058_Sexual_Monomorphism_in_Spotted_Hyenas_Crocuta_crocuta) and that the peniform clitoris of the female ‘mimics’ the penis.

However, let us rethink the whole conceptual framework.

The conventional view - which I question in this Post - can be elaborated as follows:

  • The female genitalia are similar to those of the male, including a peniform clitoris which looks so similar to a penis that the sexes are hard to distinguish.
  • Clitoral greetings are particularly important for maintaining a strict hierarchy, in which females tend to dominate males.
  • The erect peniform clitoris is used in greetings between individuals, during which olfactory signals are exchanged.
  • The size and scent of the peniform clitoris provide an honest form of communication between individuals.
  • The need for females to dominate males in competition for food arises from the unique strategy of the spotted hyena in travelling for up to five days away from the den on foraging excursions, to generate and then bring back milk to the young.
  • 'Sexual mimicry' (https://dash.harvard.edu/bitstream/handle/1/41467428/113481%20muller.pdf;jsessionid=3AA952CD2804CE17C8AAD0C7CC130F3D?sequence=1 and https://sciencetrio.wordpress.com/2009/11/09/genital-mimicry-social-erections-and-spotted-hyenas/) in the spotted hyena is thus partly explained by the idea that successful breeding depends - more than in any other mammal - on full dominance of females over all males, and maintenance of the female hierarchy across a clan which can be extensively dispersed.

However, this account throws up several incongruities. 

Females display the peniform clitoris not to males (which have their own separate hierarchy) but to females. It is the subordinate, not the dominant, individual that tends to show an erection in greeting rituals. In juveniles of the spotted hyenas, the clitoris is larger (relative to body size) than in adults. Only in the spotted hyena does the clitoris double as a birth canal; this species actually gives birth through its clitoris. (An enlarged clitoris per se is not unique to the spotted hyena, occurring also in e.g. true moles (Talpidae, https://en.wikipedia.org/wiki/Talpidae) and the fossa (Cryptoprocta ferox, https://en.wikipedia.org/wiki/Fossa_(animal)). And in other ways as well, the peniform clitoris is not actually analogous to the penis.

These incongruities suggest that a central question about this species is not why the clitoris is so penis-like, but why the birth-canal has been relocated to pass through an organ as narrow as a penis. Please note that the clitoris could theoretically have been just as penis-like but separate from the vagina, with only the urethra running through the clitoris.

What I have not seen pointed out previously is that it has - in evolutionary terms - always been possible for the peniform clitoris of the spotted hyena to contain the urethra (and thus to be the route for micturition, just like the penis) without also serving as a birth-canal. After all, in most mammals the urethra and the vagina are separate in the first place. So the spotted hyena has chosen, evolutionarily, not only to fuse the the urethra with the clitoris, but also to fuse the vagina with the clitoris. These are two different changes, and the more puzzling one is the fusion of the birth canal with a penis-like tube because this makes birth so difficult. The risks are potentially lethal.
  
The penis is mainly an organ of masculine intromission, but the peniform clitoris is - I hypothesise - mainly an organ of demotion.

Please consider that, In the spotted hyena, there are two ‘bottlenecks’ of life-and-death importance in the groin of the female.

Firstly and most importantly, there is a metaphorical bottleneck of the milk supply to offspring. The whole life-history strategy of the species depends on milk flowing at a certain rate and timing for reproduction to succeed. Let us assume for now that a crucial aspect of the spotted hyena is how odd the lactational bottleneck is in breeding females.

The second bottleneck is that of the birth canal, which has been converted into the narrowest form conceivable. This more literal bottleneck means that both birth and growth have been so configured as bottlenecks.

These bottlenecks may ensure that  the most proficient individual females reproduce successfully with the resources acquired by the whole clan. Crucial here is that the milk supplied by the dominant females exceeds what it would be if the spotted hyena foraged as a solitary animal. The collective procures much of the food (by gregarious hunting and by gregariously overpowering the lion) but a few individuals channel much of this food through their bodies.

The security of the milk in the female's udder is of paramount importance. Production of milk over five days of exertion, by virtue of access to food in an extremely competitive species, is likely to be vital for survival of young. The peniform organ is an instrument whereby inferior/lower-ranking females reaffirm their place unequivocally. This increases the security of the milk because it largely removes the risk of a milk-bearing female being challenged and injured, or prevented from eating, by other females of the clan. This rationale also invokes larger predatory species; the spotted hyena needs to have unquestioned access to the kill but it also needs conspecific help in its contests with the lion (Panthera leo). This is why the collective of the clan is so important and it is crucial that all members know their place in it.
  
We can accept that the peniform clitoris is an honest organ in the spotted hyena, preventing any miscommunication or political pretences that could put the most valuable members of the clan, namely the dominant milk-bearing females, at risk. There is a premium on olfactory truthfulness in this species, revealing the true political alliances, because the complex alliances cannot be observed in real time, and must be observed virtually instead. The peniform clitoris hypothetically ensures that there is minimal deception given that a given individual of the spotted hyena is unable to see most of the interactions among other individuals in the way possible in e.g. baboons (Papio). Honesty is crucial because the spotted hyena has a ‘virtual’ clan rather than one in which political machinations can be observed in real time.
 
What, then, is the true main function of the peniform clitoris of the spotted hyena? My goal here is to label this ‘an organ of ....’ along the lines of calling the penis ‘an organ of sexual intromission’. I suggest that the answer is 'social demotion' (as opposed to promotion).
 
The reason why this is worth careful consideration is that no other animal seems to possess an organ of demotion, and demotion is something different from submission in the sense of surrender. Besides, submission already has a particular social meaning in Biology.
 
Submission needs no special organ because all the animal has to do is lower its head or its ears, put its tail between its legs, whimper, or lie with its belly exposed. Submission means ‘giving up’ in the context of a particular agonistic event. What happens in the spotted hyena is different: it is indeed submission in the sense that the individual submits to a process in which it is usually 'humiliated' (the process being the detailed olfactory examination of its peniform clitoris). However, submission describes this poorly because surrender takes only a moment whereas what really happens in the greeting ceremony of the spotted hyena is more like an interrogation.
 
'Sexual monomorphism’ is misleading in the spotted hyena because the peniform clitoris and the normal mammalian penis are functional opposites, in the following sense. The penis is always erected and displayed in a context of promotion, i.e. the male individual promotes himself socially and/or sexually. No male animal except the spotted hyena, as far as I know, erects its penis to ‘submit’ to any other individual, or to be 'humiliated'. The penis is mainly a sex organ but in its social use it is promotive, implying superiority where there is rivalry among males.
 
A crucial aspect of the spotted hyena, not reflected in the conventional view, is that the relationship has been inverted. The peniform organ is now erected demotively rather than promotively. Female in erection affirm their demotion, and this has perhaps extended partly to males, which may experience erection not merely in sexual excitement or self-assertion vs other males, but also as a way of affirming ‘I remain demoted’ to a courted female.
 
It is by this rationale that I suggest that we regard the peniform clitoris of the spotted hyena as ‘an organ of demotion’.
 
Come to think of it: does the spotted hyena erect its peniform organ while micturating?
 
Given that in both male and female of this species the peniform organ serves as a spout for urine, and given that in flaccid mode the peniform organ is little more than a bump on the surface of the body, it is easy to assume that the act of micturition – even if only for reasons of hygiene – would involve the partial erection of the peniform organ. And this may indeed be a reasonable assumption in the male.

However, we know that, in the case of female, there is no ceremonial micturition; urine is passed urine without ritual, often while lying down, soiling the fur of the flanks. This leads me to doubt that females bother to erect the clitoris, even partially. This, if true, would be important because it shows that the peniform clitoris hardly qualifies as a functional spout for urine. It is not really convergent with the penis in this function, if the female does not actually convert her flaccid clitoris into a spout while micturating.
  
The problem with the terms 'sexual mimicry' and 'sexual monomorphism':

Mimicry is essentially functional, i.e. the object concerned gets an advantage from resembling the object that it resembles. By mimicking a toxic butterfly, a harmless butterfly implies a functional similarity, in this case toxicity (which is untrue). This correct use of ‘mimicry’ surely does not apply to the spotted hyena. If it were a case of mimicry, then we would expect that the peniform clitoris would behave like a penis.

The only functional similarity is that the clitoris produces scent, much as the penis does - which is not enough evidence of overall mimicry. Besides, it seems tenuous to claim that the organ needs to resemble a penis physically to produce the scents in question. The vulva of the normal female mammal is perfectly capable of giving off scents. So even here the case for mimicry seems weak.

'Monomorphism' is too easily misinterpreted (the more insidiously for the fact that this is usually implicit rather than explicit) to mean that the genitalia of the female are like those of the male. I think the truer interpretation of the same facts is that what is most remarkable is how functionally different these female genitalia are from normal mammalian male genitalia.

If the peniform clitoris were really to resemble the penis functionally, the following would apply.
 
Firstly, the clitoris would be used for penetration. This is conceivable if one imagines that in the spotted hyena there might have been a matriarchal system in which a female ritual of dominance consisted of rape-like actions. It is interesting that there seems to be no recorded instance of female-on-female rape in the animal world, but if such a thing was possible it would surely be in a species with a peniform clitoris. Even anal rape is conceivable in the spotted hyena given that this species lacks a vagina in the conventional sense.
 
Because nothing of the sort occurs in the spotted hyena, the concept of mimicry does not seem apt. As far as I know, females do not even mount subordinate individuals ritually, as happens in e.g. certain ruminants.
 
Secondly, the clitoris would be used as a spout for urine, particularly in scent-marking (as seen in the domestic dog). As far as I know, there is no mimicry of the penis w.r.t. micturition, other than the fact that the urine exits from the peniform organ (I suspect usually in its most flaccid state).
 
Thirdly, the clitoris would be used in the body language of self-assertion or the display of confidence/libido. This is seen in primates including humans, signified by the slang word ‘cock’ and ‘cocky’. In fact there is nothing ‘cocky’ about erection of the peniform clitoris. Instead its erection being a particularly clear signal of self-demotion rather than self-promotion.
 
So, could it be that this puzzle, i.e. that the clitoris of females superficially resembles the penis of males while not mimicking it functionally, that is central in our understanding of the species as a whole?
  
And is the fact that the spotted hyena gives birth through its clitoris not, in a sense, proof of a lack of mimicry?

No sexual mimicry in the spotted hyena

The spotted hyena shows sexual mimicry with a clitoris as prominent as the penis (see above photographs). This is part of an extremely matriarchal social system in which females have a ‘cocky’ attitude and bully males.

Although the genitalia look identical between the sexes in the spotted hyena, the peniform clitoris cannot be said to mimic the penis because the main functions of the two organs are more disparate than in most mammals. Unlike the penis, the peniform clitoris does not function as a focus of sexual pleasure. Its erection signifies neither libido nor confidence. It is not used as an urinary spout in scent-marking, and micturition is unaccompanied by leg-cocking. It is not used assertively; females perform neither rape nor token mounting to enforce the hierarchy. And it is less conspicuous than the adjacent udder3 for much of the life of the female. Furthermore, for the female to mimic the male spotted hyena would be pointless because in this species the male is no stronger than the female in the first place.

Crocuta crocuta adult female:
http://scientopia.org/img-archive/scicurious/img_498.jpg

 
Crocuta crocuta adult female:
http://ak-hdl.buzzfed.com/static/2014-03/enhanced/webdr05/29/13/anigif_enhanced-10290-1396114410-13.gif

1 Crocuta crocuta adult female:
http://scientopia.org/img-archive/scicurious/img_498.jpg

2 Crocuta crocuta adult female:
http://ak-hdl.buzzfed.com/static/2014-03/enhanced/webdr05/29/13/anigif_enhanced-10290-1396114410-13.gif

3 which is likely to be equally important in emitting scents and imparting information on social status

(writing in progress)

Posted on Μάιος 27, 2022 0628 ΠΜ by milewski milewski

Σχόλια

The evolutionary pressure exerted on an adaptive function of the clitoris of the spotted hyena are unexplained. Why would juveniles require a large, penis-like clitoris, more than any other mammal?

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A fascinating read. Thank you.

Αναρτήθηκε από doug263 σχεδόν 2 χρόνια πριν

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