Adaptive radiation of auricular flags in hippotragin bovids: Hippotragus, Oryx, and Addax, part 3

...continued from https://www.inaturalist.org/journal/milewski/88221-adaptive-radiation-of-auricular-flags-in-hippotragin-bovids-hippotragus-oryx-and-addax-part-2#

POSTERIOR AURICULAR FLAGS

Dear Readers, in order to refresh your search-image for posterior auricular flags, I offer the following of a reduncin bovid, Kobus defassa harnieri (https://www.gettyimages.com.au/detail/photo/hairy-neck-kob-herd-royalty-free-image/184939425?phrase=kob+antilope&adppopup=true).

The above photo nicely illustrates how a given species/subspecies can have ear pinnae with conspicuois colouration, at moderate distances from the observer, on both the front- and back-of-ear.

Returning now to apply this search-image to hippotragins:

In most hippotragins, the back-of-ear has unremarkable colouration, as shown by the following:

Hippotragus equinus adult females:
https://www.inaturalist.org/observations/191149446
https://es.123rf.com/photo_9273659_hippotragus-equinus.html
https://www.inaturalist.org/observations/195737269

Oryx dammah:
https://www.istockphoto.com/video/sable-oryxes-in-slow-motion-120fps-gm1362867958-434635226?searchscope=image%2Cfilm

Oryx leucoryx:
https://www.dreamstime.com/stock-photo-scimitar-oryx-antelopes-image10430630
https://www.dreamstime.com/stock-photography-scimitar-oryx-antelopes-family-image10430552

Oryx beisa:
https://www.youtube.com/watch?v=p5tXGZ7U-HM
https://www.shutterstock.com/image-photo/gemsbok-antelope-oryx-gazella-south-africa-183257147
https://www.istockphoto.com/photo/orix-in-samburu-national-reserve-kenya-gm1369589632-439320905?phrase=east+african+oryx%2C+beisa%2C+gemsbok%2C+samburu+national+park&searchscope=image%2Cfilm

Addax nasomaculatus in summer pelage:
https://www.naturefootage.com/video-clips/OFE150113_0231/addax-walking-in-a-desert
https://stock.adobe.com/images/an-addax-feeding-on-grass/260667554?prev_url=detail
https://stock.adobe.com/images/addax-addax-nasomaculatus-also-known-as-the-white-antelope-and-the-screwhorn-antelope-is-an-antelope-of-the-genus-addax-that-lives-in-the-sahara-desert/293706258?prev_url=detail
https://stock.adobe.com/images/addax-addax-nasomaculatus-also-known-as-the-white-antelope-and-the-screwhorn-antelope-is-an-antelope-of-the-genus-addax-that-lives-in-the-sahara-desert/318671381?prev_url=detail
https://www.gettyimages.ca/detail/photo/addax-also-known-as-the-white-antelope-royalty-free-image/885411774
https://www.gettyimages.com.au/detail/photo/pair-of-beasts-royalty-free-image/504838051?phrase=addax+antelope&adppopup=true
https://www.bigstockphoto.com/image-294614248/stock-photo-an-addax-feeding-on-grass-with-its-spiraling-horns-visible
https://www.pond5.com/stock-footage/item/105952310-addax-addax-nasomaculatus-stops-scratch-its-head-desert
https://stock.adobe.com/images/an-addax-feeding-on-grass/260667554?prev_url=detail

However, there are several exceptions, by

• species,
• sex, and
• season.

Furthermore, posterior auricular flags in hippotragins result from

• pigmentation/depigmentation, and/or
• sheen effects, reflecting the structure of the hairs on the back-of-ear.

Species possibly qualifying for a posterior auricular flag (which may include the base of the ear pinna) are

• Hippotragus equinus (mature males only),
• O. gazella (dependent on sheen), and
• A. nasomaculatus (in winter pelage, https://www.alamy.com/stock-photo-addax-84795583.html?imageid=A5D34401-C402-4644-838F-77B266D728AF&p=260094&pn=1&searchId=c3d6008a7704aa64aaba4a9d4842fef9&searchtype=0).

An additional species, unlikely to qualify, but showing a suggestive pattern, is

• Hippotragus niger.

HIPPOTRAGUS EQUINUS

The following show that the back-of-ear may possibly be pale enough, in adult males, to qualify for a posterior auricular flag (https://www.inaturalist.org/observations/69214021 and https://www.inaturalist.org/observations/182511604 and https://www.inaturalist.org/observations/165908434 and https://www.inaturalist.org/observations/17443996 and https://www.alamy.com/roan-antelope-hippotragus-equinus-standing-looking-diretly-into-camera-with-a-natural-bushveld-background-in-hwange-national-park-zimbabwe-image371221253.html?imageid=5E6D5ED8-5552-465C-B098-85A32A6844FA&p=364701&pn=3&searchId=bf54820912fa8b8654b0587c83cd4188&searchtype=0).

I have yet to see this pallor in adult or adolescent females (https://www.alamy.com/rare-sighting-of-a-rare-roan-antelope-standing-on-the-dry-arid-african-savannah-in-hwange-national-park-zimbabwe-image371223261.html?imageid=E8F6BF1A-EE83-4E69-ABF8-65A692C43D35&p=364701&pn=3&searchId=bf54820912fa8b8654b0587c83cd4188&searchtype=0 and https://www.alamy.com/stock-photo-tempestuous-roan-antelope-hippotragus-equinus-84710337.html?imageid=016E7C89-478E-437A-906F-758CA1AB4AB6&p=172933&pn=3&searchId=d47afca96099067b240be3e499db1072&searchtype=0 and https://www.inaturalist.org/observations/6588744 and https://www.inaturalist.org/observations/179363171 and https://www.inaturalist.org/observations/154758553 and https://www.inaturalist.org/observations/4756887).

Photos show evidence of sexual dimorphism in a (sheeny?) pallor on the back-of-ear in H. equinus, as follows:

• present in mature male:
  https://www.inaturalist.org/observations/199638 and scroll to eighth photo in https://africawild-forum.com/viewtopic.php?t=406

• absent in adolescent male:
  https://www.shutterstock.com/image-photo/mating-strategies-male-antelopes-pair-savannah-1053425927 and https://www.shutterstock.com/image-photo/mating-strategies-male-antelopes-pair-savannah-1053425924

• absent in adult female:
  scroll to second photo in https://africawild-forum.com/viewtopic.php?t=10482&start=10 and scroll to fifth photo in https://africawild-forum.com/viewtopic.php?t=406&start=110).

This masculine auricular pallor is unusual among ungulates, and deserves further investigation. In particular:

• the pallor seems to result from a combination of depigmentation and sheen, and
• the dark apical tuft seen in juvenile males (https://huttsatwork.wordpress.com/2013/11/16/ruma-national-park/img_4602-young-roan-antelope/), which would accentuate the display by offsetting the pallor, tends to be lost in maturity (https://www.shutterstock.com/image-photo/roan-antelope-lying-bush-southern-african-643041958).

For further information, please see comment below titled 'various views of the back-of-ear in the roan antelope'.

HIPPOTRAGUS NIGER

A case could possibly be made for a posterior auricular flag in adult males (https://www.shutterstock.com/image-photo/pair-sable-antelopes-hippotragus-niger-south-185656784) and mature females (https://es.123rf.com/photo_204261477_sable-antelope-stands-on-sand-in-profile.html and second and third photos in https://www.inaturalist.org/observations/194567195).

However, the back-of-ear is not consistently pale enough for this to be clear (https://www.gettyimages.ae/detail/photo/sable-antilope-chobe-national-park-royalty-free-image/1271310163?phrase=sable+antelope&adppopup=true and https://www.shutterstock.com/video/clip-1013518391-sable-antelope-walking-riverfront-chobe-national-park).

Differentiation of the back-of-ear by hue in H. niger does not qualify in the terms of this study, which heeds only darkness vs paleness (https://es.123rf.com/photo_15732580_grandes-hombres-ant%C3%ADlope-sable-hippotragus-niger-sud%C3%A1frica.html and https://www.natureinstock.com/search/preview/sable-antelope-hippotragus-niger-portrait-limpopo-south-africa/0_00116199.html and https://www.agefotostock.com/age/en/details-photo/male-sable-antelope-portrait-hippotragus-niger-captive-beauval-zoo-parc-france/T06-3368767 and https://es.123rf.com/photo_9730457_hippotragus-niger-hippotragus-niger-es-un-gran-ant%C3%ADlope-africano-estrechamente-relacionadas-con.html and https://www.alamy.com/sable-antelope-hippotragus-niger-adult-male-kalahari-desert-south-african-republic-image184127336.html?imageid=39635505-078F-4355-8BF5-898C8C9DE793&p=391651&pn=7&searchId=48c5019063f87c658c767ebd85f25bc9&searchtype=0).

However, my disqualification of H. niger may warrant re-evaluation.

The clearest evidence I have found for a posterior auricular flag in H. niger is the following of a fully mature female individual, in which even the crown has turned dark: https://www.alamy.com/sable-antelope-hippotragus-niger-adult-male-kalahari-desert-south-african-republic-image184127339.html?imageid=4D5343FA-9439-4D83-8CE4-4997FD1515DF&p=391651&pn=7&searchId=48c5019063f87c658c767ebd85f25bc9&searchtype=0.

The following - remarkably fortuitously - shows the anterior surface of the ear pinna in the same individual in the same illumination, for direct comparison: https://www.alamy.com/sable-antelope-hippotragus-niger-adult-male-kalahari-desert-south-african-republic-image184127338.html?imageid=2EA1DD23-A066-4E18-A976-A5A7011A1054&p=391651&pn=7&searchId=48c5019063f87c658c767ebd85f25bc9&searchtype=0.

ORYX GAZELLA

Oryx gazella seems to qualify for a posterior auricular flag. However, this is so subtle that I scrolled through hundreds of photos before noticing it.

The pigmentation on the posterior surface of the ear pinna is similar to the ground-colour.

There is dark apical emphasis (https://www.istockphoto.com/photo/gemsbok-walking-in-the-kalahari-desert-botswana-gm480075562-68799463), as on the front-of-ear. However, this is usually insufficient to make the back-of-ear conspicuous:
https://www.inaturalist.org/observations/10840211
https://www.inaturalist.org/observations/10792750
https://www.inaturalist.org/observations/29043954
https://www.inaturalist.org/observations/35157986
https://www.inaturalist.org/observations/36177238
https://www.inaturalist.org/observations/74540339
https://www.inaturalist.org/observations/19972268
https://www.inaturalist.org/observations/32556734
https://www.inaturalist.org/observations/29043954
https://www.inaturalist.org/observations/21993556
https://www.inaturalist.org/observations/10840560
https://www.inaturalist.org/observations/15036251
https://www.inaturalist.org/observations/13052201
https://www.inaturalist.org/observations/11888325
https://www.inaturalist.org/observations/65936637
https://www.inaturalist.org/observations/112718149
https://www.inaturalist.org/observations/133100160
https://www.inaturalist.org/observations/143658144
https://www.shutterstock.com/image-photo/gemsbok-walking-on-dusty-soil-last-149255897

What I noticed after persistent investigation is that the back-of-ear sometimes appears conspicuously pale, accentuated by its apical darkness:
https://www.inaturalist.org/observations/80773623
https://magazine.wildlife.state.nm.us/photographing-oryx-in-new-mexico/
scroll in https://chivicafricansafaris.com/campfire-stories/jims-gemsbok/
https://www.inaturalist.org/observations/59674731
https://www.inaturalist.org/observations/32913305
https://www.inaturalist.org/observations/25620722
https://www.istockphoto.com/photo/oryx-dammah-with-red-dune-gm186867241-16442751?phrase=scimitar+oryx&searchscope=image%2Cfilm
https://www.istockphoto.com/photo/starring-gemsbok-from-behind-in-kalagadi-gm802451480-130083779
https://www.inaturalist.org/observations/71967328
https://www.inaturalist.org/observations/52790492

This is owing to sheen, rather than depigmentation.

Furthermore, the sheen-effect is more consistent when the posterior surface of the ear pinna is viewed from the front:
https://fossilrim.org/blog/what-goes-into-antelope-breeding-decisions/
https://www.alamy.com/gemsbok-oryx-gazella-adult-male-feeding-on-grass-kgalagadi-transfrontier-park-northern-cape-south-africa-africa-image352248036.html?imageid=8B650B38-EFD8-460C-BDAD-A0BF4D44198D&p=642197&pn=1&searchId=a5bfc98cba12eb15dd1be0367313fd95&searchtype=0
https://www.agefotostock.com/age/en/details-photo/gemsbok-oryx-gazella-females-have-been-fighting-kalahari-desert-kgalagadi-transfrontier-park-south-africa/C43-2951576
https://www.inaturalist.org/observations/87448368
https://www.inaturalist.org/observations/33538725
https://www.inaturalist.org/observations/70149713
https://www.inaturalist.org/observations/15281070
https://www.inaturalist.org/observations/9294514
https://www.inaturalist.org/observations/20175855

The posterior auricular flag tends to be most noticeable when the animal faces the viewer, close-up, with the ear pinnae rotated. This suggests an emotional signal, probably in antagonistic interactions.

I hypothesise that, by human analogy, this facial expression communicates a message similar to that of a disapproving frown or an angry furrowing of the eyebrows (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7266324/#:~:text=Some%20of%20the%20emotions%20are,closer%20together)%20%5B4%5D.).

A similar functional explanation may possibly apply to H. equinus, with the difference that it applies only in mature males in the latter species.

ADDAX NASOMACULATUS

Addax nasomaculatus fails to qualify for either an anterior (see part 2) or a posterior auricular flag, in summer pelage.

However, it qualifies for a posterior auricular flag (https://www.shutterstock.com/video/clip-1099227021-baby-antelope-strolling-around-sand-search-food and https://stock.adobe.com/images/addax-2/79418652?prev_url=detail and https://www.bigstockphoto.com/image-84333236/stock-photo-addax-3), in winter pelage.

The whole posterior surface of the ear pinna in A. nasomaculatus is conspicuous in winter pelage, because it is whitish in contrast with the ground-colour on neck, nape, and crown (https://stock.adobe.com/video/addax-in-the-zoo-park/553348188?prev_url=detail).

Also see:
https://www.inaturalist.org/posts/55639-auricular-semets-in-alces-and-odocoileus-but-not-other-odocoileine-deer#
https://www.inaturalist.org/journal/milewski/55532-previously-overlooked-facial-expressions-in-the-wapiti-cervus-canadensis#
https://www.inaturalist.org/posts/75905-unlike-the-blesbok-the-bontebok-damaliscus-pygargus-pygargus-lacks-an-auricular-flag#
https://www.inaturalist.org/posts/60644-auricular-flags-in-ungulates#
https://www.inaturalist.org/posts/80254-the-anterior-auricular-flag-of-the-greater-kudu-strepsiceros#
https://www.inaturalist.org/journal/milewski/63961-auricular-flags-in-lepus#
https://www.inaturalist.org/posts/64011-interspecific-variation-in-flags-as-features-of-adaptive-colouration-in-hares-part-2-other-species-of-semi-arid-north-america#
https://www.inaturalist.org/posts/64060-interspecific-variation-in-flags-as-features-of-adaptive-colouration-in-hares-part-5-overall-discussion#
https://www.inaturalist.org/posts/77649-pictures-worth-a-thousand-words#

Posted on January 5, 2024 04:11 PM by milewski