Is the sable antelope the only ungulate - indeed mammal - that advertises its penis with black-and-white punctuation?

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In the sable antelope (Hippotragus niger, https://www.inaturalist.org/taxa/42334-Hippotragus-niger), the presence of the penis is visually unmistakable in adult males.

This is because the tip of the preputial sheath (https://en.wikipedia.org/wiki/Penile_sheath) is covered with blackish hairs. This is offset by the adjacent surface of the belly, which is broadly white in crisp contrast with the dark of the flanks.

https://www.dreamstime.com/sable-antelope-bull-fully-grown-sable-antelope-looking-around-bushveld-background-image193850098

https://www.dreamstime.com/sable-anthelope-bull-standing-proud-sable-antelope-bull-standing-proud-alerted-to-any-potential-predator-hippotragus-niger-image112607538

https://www.kurtsafari.com/kruger-national-park-news/kruger-national-park-animals-guide/sable-antelope/

https://www.alamy.com/two-giant-sable-antelope-with-sable-antelope-cow-south-africa-image625053.html?imageid=857E1C13-E861-4A0B-8B23-1C0C321BC978&p=5008&pn=1&searchId=ed7fa51f951391c0ccd4167341460322&searchtype=0

https://dewetswild.com/2018/05/31/sable-antelope/

https://www.silentvalleysafaris.co.za/product/50-sable-bull-for-sale/

https://www.shutterstock.com/image-photo/male-sable-antelope-hippotragus-niger-magnificent-178257524

https://www.shutterstock.com/image-photo/huge-sable-bull-posing-kruger-national-1007814493

https://www.shutterstock.com/image-photo/sable-antelope-hippotragus-niger-adult-male-1947597349

https://www.shutterstock.com/image-photo/male-sable-antelope-bull-walking-open-1154170702

https://www.shutterstock.com/image-photo/sable-antelope-bull-hippotragus-niger-western-507678175

The following shows that the colouration in question is apparent - like an exclamation mark under the belly - even at some distance: https://www.shutterstock.com/image-photo/big-male-sable-antelope-grazing-on-1344166796.

The preputial colouration seems congruent with the overall boldness, in dark/pale contrast, of the colouration of the whole figure. The pattern is part of the year-round masculine self-advertisement in the sable antelope.

This punctuation of the prepuce is the most reliable guide to the sex of the individual, in a species in which fully mature females can emulate males in all other aspects of colouration (https://www.inaturalist.org/posts/86973-bold-black-and-white-in-females-of-the-southern-sable-antelope-hippotragus-niger-niger-anti-predator-warning-or-maternal-emulation-of-masculinity).

The preputial pigmentation facilitates the differentiation of the sexes in extant spp. of Hippotragus. This is true despite the remarkable emulation of other male features in females of these and other hippotragin bovids (https://www.inaturalist.org/observations?place_id=any&taxon_id=846296&view=species).

The following shows how easily mature females of the southern sable antelope (Hippotragus niger niger) can be distinguished from males, despite a lack of sexual dimorphism in the rest of the colouration: https://www.shutterstock.com/image-photo/sable-antelope-black-white-shade-1244584366.

COMPARISON WITH OTHER RUMINANTS

At first consideration, it may seem unremarkable that a large mammal advertises its masculinity in this pointed way.

However, on closer examination it turns out that the sable antelope is likely to be unique in this respect.

It is true that the preputial sheath is also dark-tipped in the roan antelope (Hippotragus equinus, https://www.shutterstock.com/image-photo/roan-antelope-bull-grassland-2372364271 and https://www.kriekwildlife.com/roan%20breeding%20bulls.html and https://www.inaturalist.org/observations/156041605 and https://www.inaturalist.org/observations/5635964).

However, this is of limited conspicuousness (https://www.inaturalist.org/observations/5518338 and https://www.inaturalist.org/observations/169938257 and https://fictionrulezforever.fandom.com/wiki/Roan_Antelope?file=Roan_Antelope.jpg), partly because the function of the pale pelage on the belly is categorically different.

In the roan antelope, the ventral surface of the torso is countershaded, in keeping with an overall postcranial inconspicuousness of the figure in full profile.

By contrast, in the sable antelope the same surface accentuates the boldness of the colouration, to the degree of qualifying as a bleeze (https://www.inaturalist.org/posts/85930-sexual-and-ontogenetic-development-of-the-ischio-abdominal-bleeze-of-the-southern-sable-antelope-hippotragus-niger-niger).

The crucial difference, then, between the sable antelope and the roan antelope is that only in the former does the preputial contrast form part of a bleeze.

Furthermore, the sable antelope exceeds the roan antelope (and all other hippotragins) in sexual dimorphism. For example, can readers tell the sex of the following specimen of the roan antelope: https://www.inaturalist.org/observations/1242319?

In the remaining two genera and six spp. of hippotragins, there is only a trace of the pattern.

In the gemsbok (Oryx gazella), there is merely a hint of emphasis (https://es.123rf.com/photo_11688593_male-gemsbok-antelope-in-the-kgalagadi-transfrontier-park-southern-africa.html and https://www.dreamstime.com/male-gemsbok-antilope-isolated-white-background-male-gemsbok-antilope-isolated-white-background-image100998754).

Among alcelaphin bovids, the bontebok (Damaliscus pygargus pygargus) resembles the sable antelope in the darkness of the flanks and the crisp demarcation of a conspicuous white belly (https://www.gettyimages.co.nz/detail/photo/bontebok-side-view-royalty-free-image/200214468-001?adppopup=true). However, neither this nor any other alcelaphin shows any emphasis of the prepuce.

Among reduncin bovids, the most bodly-coloured forms are

• the white-eared kob (Kobus kob leucotis, https://naturerules1.fandom.com/wiki/White-eared_Kob?file=GambellaNP-681620180324.jpg), and

• the Nile lechwe (Kobus megaceros, https://www.sidebysidesafaris.com/en/news/hunting-the-nile-lechwe-with-side-by-side-safaris
  and https://www.ultimateungulate.com/Artiodactyla/Kobus_megaceros.html).

However, once again, in both cases, the prepuce is not accentuated, so that the presence of a penis is not advertised.

Among rupicaprin bovids, some views of chamois (Rupicapra spp.) show a narrow preputial tassel (https://www.alamy.com/stock-photo-chamois-rupicapra-rupicapra-france-europe-173961138.html and https://www.agefotostock.com/age/en/details-photo/chamois-alpine-chamois-rupicapra-rupicapra/PRE-RM01910100450 and https://upload.wikimedia.org/wikipedia/commons/f/fc/G%C3%A4mse_%28Rupicapra_rupicapra%29_auf_dem_Ornach_06.jpg and https://www.britannica.com/animal/Pyrenean-chamois and https://www.researchgate.net/figure/A-male-Apennine-chamois-in-winter-pelage-November-Photo-Credit-C-Bruno-dAmicis-from_fig7_309136935 and https://www.natureplprints.com/2014-highlights/chamois-rupicapra-rupicapra-running-ridge-15331521.html.

Furthermore, the northern chamois (Rupicapra rupicapra, https://www.inaturalist.org/taxa/42347-Rupicapra-rupicapra) tends to be conspicuously dark-and-pale in winter pelage (https://www.monaconatureencyclopedia.com/rupicapra-rupicapra/?lang=en)
and https://www.alamy.com/chamois-rupicapra-rupicapra-male-marking-its-territory-by-rubbing-its-scent-glands-located-behind-the-horns-against-twigs-alpes-italy-image239496694.html and https://www.inaturalist.org/observations/193500441).

However, the tassel in question

• has limited conspicuousness, partly because its tone does not necessarily differ from that of the belly (https://www.inaturalist.org/observations/188206299), and
• probably has an olfactory, rather than visual, function.

Bisons - which are bovin bovids - are another example of advertisement of the penis by means of a tassel (https://www.alamy.com/large-male-of-bison-in-the-forest-buffalo-walking-across-the-forest-travel-photo-no-people-selective-focus-image457375427.html?imageid=DAC2BE4E-5FB7-4D4F-A492-302A9ED02149&p=1366888&pn=2&searchId=b0c94f96bab8f3b522ef02240745aa32&searchtype=0 and https://upload.wikimedia.org/wikipedia/commons/5/59/European_bison_%28Bison_bonasus%29_male_Bia%C5%82owieza.jpg). Furthermore, this can be a conspicuous part of the dark ventral silhouette of the figure.

However, in Bison there is no dark/pale contrast in the ventral pelage, suggesting that the main mode of advertisement, as in Rupicapra, is olfactory.

In African buffaloes (Syncerus, https://www.alamy.com/african-buffalo-syncerus-caffer-adult-male-walking-mpumalanga-south-africa-image342300914.html and https://www.alamy.com/african-buffalo-syncerus-caffer-side-view-of-an-adult-male-standing-on-the-ground-mpumalanga-south-africa-image342300878.html), the tassel is sparse, but the preputial sheath is associated with a small abdominal dewlap.

When adult males of Syncerus micturate, this pendulous structure tends to twitch visibly. However, there is no dark/pale accentuation.

Turning now from the family Bovidae to the family Cervidae:

A preputial tassel occurs in some deer, e.g. the fallow deer (Dama dama, https://www.bigstockphoto.com/image-187248736/stock-photo-white-fallow-deer-stag-the-fallow-deer-is-a-ruminant-mammal-belonging-to-the-family-cervidae and https://www.poronuihunting.com/fallow-multicolored-camouflage-experts/ and https://www.wilddeer.net.au/2021/11/12/the-fallow-dama-dama-dama-dama-dama/). In the rutting season, this conspicuously twitched in masculine display (https://www.youtube.com/watch?v=oxHvwrwyuso).

However,

• the darkness of this tassel seems to be owing to staining by urine and/or secretions, rather than pigmentation (https://www.youtube.com/watch?v=O7FnXYQvY7c), and
• the function of the tassel seems to be mainly olfactory.

In the red deer (Cervus elaphus, https://www.youtube.com/watch?v=ZZPdZD06VjM and https://www.dreamstime.com/red-deer-stag-drinking-water-puddle-close-up-uk-image271706504 and https://www.dreamstime.com/stock-photo-red-deer-jackdaw-cervus-elaphus-mating-season-image63750877), the prepuce has similar position and twitching to that in the fallow deer. However, the tassel is too short to be conspicuous.

In the wapiti (Cervus canadensis, https://www.youtube.com/watch?v=Tu9261UCxgQ and https://www.youtube.com/watch?v=5qniKTWmtqg), the prepuce is located in a relatively anterior position, as in various bovids.

However, there is no preputial tassel, and any visual display is merely a matter of subtle twitching. The following (https://www.youtube.com/watch?v=VL0j3Fui1j0) shows this as the animal micturates on itself for olfactory advertisement.

COMPARISON WITH PRIMATES

Several spp. of primates have conspicuous colouration on the penis and/or prepuce (http://animal.memozee.com/view.php?tid=3&did=17669 and https://www.yayimages.com/28050806/closeup-of-a-mandrill-monkey-with-its-male-genitals-tropical-primate-from-cameroon-africa.html and https://www.alamy.com/stock-photo-rear-end-of-male-black-faced-vervet-monkey-showing-anus-red-penis-72589674.html and https://en.m.wikipedia.org/wiki/File:Vervet_Monkey_%28Chlorocebus_pygerythrus%29_%286011903243%29.jpg and https://depositphotos.com/photo/family-of-olive-baboons-during-grooming-140962280.html).

However, in primates,

• no species advertises its masculinity by means of dark/pale contrast on the genitals, let alone a white groin combined with a dark prepuce,
• the hues of the male genitalia occur not in the pelage but in the epidermis/dermis,
• the conspicuousness is not owing to pigmentation other than that of the blood, visible in the dilated capillaries (https://watermark.silverchair.com/blad089.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAA34wggN6BgkqhkiG9w0BBwagggNrMIIDZwIBADCCA2AGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMbAhChxoSmk6mdh_SAgEQgIIDMZJmPVmbYIYtpwr96khHZKWm6ioQG0pEjUXSU7nS9i_aeMOM0s1Y8Z_MoN2F4CmeLC9jX_IV3uzz7cj51qhk0-afjHAo5YGfK67RG-jgUFOhs9YPaIxL4mUuqB3X76qj1jlDJ72VQuj6TS1OL3tKynlmNM9gN6FzAS0-GJDy_iFqwnOuJKVtYSGSIeXcVakzHpMJ9y02HSffnwFD4f-SbmNFEy87lh3ouJt5hLH5CnkFEUsopblstwcSJ8glkixnShoX1bkZMYw6iErlphmEtqJWc4GxnN4LGQNk4L5tFhIb_clPQScijYZyYjN4LMlR6y0dw0pDwrfqK38difwokLratAac8q5bh3E1jshJTp6OwNy3DcSCqBlhkBprhodLXYiJlxbosvYedfuadokv4QjozKBq8cjEiV1aohR1KxqME8pXGKr1uuiawg5Ts_LkxjXqIA5JCTdTEIA3n4jW7y2YBLCbjHN64jsLbb0PhQuEUfJo1aUjygtLum9S-BXOxmxFqAeZIr2OcA8tG0l4qszxvrJmM46uNbLFE1YPj9xev6Wx2JHJQFUs1RG_BUaF1bhTq9cLS0c-MCbmBqJN_yvcxvKRotfVP4Bp5TCj2xavbvwJhckcIVrX-uYdmD-FkY-DURFN7VQBb2buFKVGhhqiPt3lnDV5RXyfpQu_yY4W45EUYZaWZuedk8tCDNPKsL1-slYeA4p8-dwrnkV99qsC_8yoELvDCq7cSpivic0wsvIMB0Om3X90LDkQ6sQEPlObFdK864R7kE026pw1ddAUPbW_SA_897KDVM68x9JQfYfES9a8bZKuMwh9OCqTsw6c5coTc-etG8AYdWy5c08zqf8-xBwjktO2vO7XzRuYXG3SWJjAb3vS2QXl0SSQqHXNbM_yhXK4I37SW4Nm8aQBgMmvHdBe4SWZHhOO6p9LLqfNCTeJOndc4d7WYJPhTPwEdMlOYXp9Pr5VmqFAWngatTexBCk6lZPH8A0iB5bltZNBc_W-qYhAVVTy44-fNdMKDJGsjekwN5D-k5rf9_DWvuCqALtoZ_UuEZeoGPJ5lKMJYEcbpmbE02RSIQzmPLc and https://www.science.org/content/article/whats-behind-blue-behind and https://biology.stackexchange.com/questions/89007/what-pigment-is-responsible-for-the-formation-of-blue-skin-color-in-some-animals), and
• phallic erection enhances the genital display, whereas in the sable antelope it detracts from the display because the merely flesh-coloured penis extends far beyond, and in erection tends to occlude, the prepuce.

OVERALL FINDING

A distinctly dark-pigmented but short-haired preputial tip seems to be unique to Hippotragus.

Even in this genus, it may have been absent in the recently-extinct bluebuck (Hippotragus leucophaeus, https://en.wikipedia.org/wiki/Bluebuck).

The most convergent species, in this respect, is the northern chamois. This rupicaprin also resembles the sable antelope in having

• sharp horns, designed for inflicting injury rather than as a form of adornment for ritual sparring,
• conspicuously dark colouration overall, albeit only in winter,
• conspicuously dark-and-pale markings on the face, reminiscent of aposematic colouration,
• minimal sexual dimorphism in horns and colouration,
• retention of adolescent males in the maternal group up to the age of 2-3 years, and
• a pugnacious demeanour relative to most other ruminants.

DISCUSSION

The distinctive genital advertisement of the sable antelope has been in plain view since European explorers first encountered the species.

However, nobody seems to have noticed that this feature is functionally unique to this species.

This may be because such an appreciation would depend on

• applying a converse approach to the prevailing reductionism in Zoology, and
• broadening the context, to encompass the bewildering diversity of other ungulates, and mammals in general.

It is only when one stands back far enough to combine detailed scrutiny with a panoramic view of hippotragins, bovids, ruminants, ungulates, and mammals that the extreme position of the sable antelope becomes fully apparent.

Publicado el 16 de diciembre de 2023 a las 04:03 AM por milewski