'Flehmen' is an exaggeration in elephants, while underplaying the reality of their vomeronasal dexterity

@paradoxornithidae @matthewinabinett @tonyrebelo @jeremygilmore @botswanabugs @ldacosta @maxallen @jwidness @ptexis @christiaan_viljoen @zarek @dejong

The vomeronasal organ (https://en.wikipedia.org/wiki/Vomeronasal_organ) performs chemical perception (https://link.springer.com/article/10.1007/BF00987849).

It is, by definition, located on the partition between the nasal cavity and the buccal cavity, allowing access from

above, via the nostrils (nares), or
below, via the mouth, or
both.

(The vomeronasal organ is discernible in the human foetus. However, it is regarded as relictual/vestigial, and probably functionless, in most adult individuals of Homo sapiens, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6050168/#:~:text=The%20vomeronasal%20organ%20(VNO)%20is,of%20the%20accessory%20olfactory%20system.)

In many mammals, vomeronasal perception is associated with flehmen (https://en.wikipedia.org/wiki/Flehmen_response and https://link.springer.com/chapter/10.1007/978-1-4757-9652-0_5).

In the literature, elephants (https://en.wikipedia.org/wiki/Elephant) are regarded as expressing flehmen (see references below).

This would be remarkable, because

their nose and mouth are jointly modified, to an extreme degree and extent among terrestrial mammals,
their sense of olfaction is so acute (https://www.pnas.org/doi/full/10.1073/pnas.1818284116 and https://genome.cshlp.org/site/press/Evolution_of_mammalian_olfaction.xhtml#:~:text=African%20elephants%20use%20their%20trunks,any%20animal%20characterized%20to%20date.) that vomeronasal perception might seem redundant,
the mobility of their proboscis allows chemical perception to be precisely directed towards any source of interest, such as female genitalia, and
soluble substances, including non-volatile ones, can be sucked up the proboscis to the threshold of the nasal cavity in the skull.

Actually, I see scant evidence that elephants express flehmen. This has been misrepresented in the literature.

However, the reality is even more remarkable.

This is that elephants use the vomeronasal organ in an uniquely direct and precise way, among mammals.

Crucial to realising that 'flehmen' is a misnomer in elephants is that this term refers to peculiar facial expressions, not events of sensory application as such.

This can perhaps best be explained by comparing elephants with mice.

Both rodents and proboscideans clearly possess a vomeronasal organ, even in adulthood.

In both cases,

the organ is embedded in a bony partition which is simultaneously the floor of the nose and the roof of the mouth, and
it is accepted that the organ is specialised for intermittent perception of substances of sociosexual significance, such as hormones/pheromones.

However, flehmen is unrecorded in rodents. There is no particular facial expression or posture associated with vomeronasal sensing. Instead, it seems that rodents merely inhale substances of interest via the nose, or lick them, or both.

If 'flehmen' or 'the flehmen response' were a sensory event, the literature would surely regard rodents as qualifying for flehmen. However, as far as I know, no author has made such a claim. Instead, the literature seems, at least tacitly, to acknowledge that flehmen is absent in rodents, in contrast to e.g. lagomorphs and hedgehogs.

The facial expression/posture of elephants, when applying the vomeronasal organ, has little in common with flehmen in ungulates, carnivores, lagomorphs, etc. Instead, it seems identical to that of simply placing a food-item, or drinking water, in the mouth.

So, how can flehmen be claimed in elephants?

The action of elephants in placing the proboscis in the mouth does not necessarily qualify as a facial expression in the first place, let alone flehmen. And it shares none of the diagnostic aspects of a flehmen expression, mentioned in the text of a previous Post (https://www.inaturalist.org/posts/87153-why-have-two-coexisting-bovids-the-sable-antelope-hippotragus-niger-and-lichtenstein-s-hartebeest-alcelaphus-lichtensteini-diverged-in-vomeronasal-flehmen-expression#).

It is perhaps unsurprising that elephants use the tip of the proboscis to place substances of interest directly at the vomeronasal location on the roof of the mouth.

However, what seems misleading - and incorrect - is that the term 'flehmen' has been stretched to include this action of the proboscis, on the basis of context.

Such conflation tends to deplete the term 'flehmen' of meaning, while at the same time obscuring something more worthy of recognition.

I refer to the following possibility:
Elephants may be the only mammals that - in partial emulation of snakes and lizards (https://www.sciencedirect.com/science/article/abs/pii/S000334720580380X and https://onlinelibrary.wiley.com/doi/abs/10.1002/jez.1402490206 and https://www.jstor.org/stable/1565343 and https://www.jstor.org/stable/4601387) - dexterously procure samples of interest and then place them directly at the vomeronasal location.

This is as opposed to the relatively awkward approach of merely inhaling by mouth, or taking urine into the mouth and then inhaling by mouth.

Furthermore:
Once we appreciate the approach taken by elephants, a new question arises, as follows.

Why is it that even those mammals with relatively long and 'dexterous' tongues have not been recorded sampling substances of sociosexual interest with the tongue-tip, and then placing the tongue-tip at the vomeronasal location?

This question applies particularly to