Hippotragin bovids in posteriolateral view: an interspecies comparison of adaptive colouration, part 2

...continued from https://www.inaturalist.org/journal/milewski/85734-hippotragin-bovids-in-posteriolateral-view-an-interspecies-comparison-of-adaptive-colouration-part-1#

FOCUSSING ON THE TAIL

In terms of colouration (more particularly, dark/pale contrasts), the part of the tail that confers conspicuousness is

• the tassel in Oryx,
• the stalk in Hippotragus, and
• neither in Addax.

Furthermore, the various species can be categorised as follows, w.r.t. how conspicuous the tail is, in posteriolateral view.

TAIL CONSPICUOUS

• O. gazella (https://www.icanvas.com/canvas-print/oryx-waving-tail-ii-mog94#1PC6-40x26&gid=1&pid=main-image and https://www.icanvas.com/canvas-print/oryx-waving-tail-i-mog93#1PC6-40x26&gid=1&pid=main-image and https://www.dreamstime.com/stock-photo-back-oryx-antilope-behind-africa-namibia-image59687734)
• O. beisa (https://park-764.business.site/ and https://www.inaturalist.org/observations/170649465 and https://www.inaturalist.org/observations/186550321 and https://www.inaturalist.org/observations/185427721 and https://www.inaturalist.org/observations/173418603 and https://www.inaturalist.org/observations/151116526 and https://www.mindenpictures.com/stock-photo-beisa-gemsbok-oryx-gazella-beisa-pair-mpala-research-centre-kenya-naturephotography-image00451580.html)
• H. equinus (https://www.inaturalist.org/observations/66772812 and https://www.inaturalist.org/observations/184561948 and https://www.inaturalist.org/observations/179362449 and https://www.inaturalist.org/observations/36915943 and https://www.inaturalist.org/observations/9355801 and https://www.inaturalist.org/observations/10838158)
• H. niger (https://www.inaturalist.org/observations/606129 and https://www.inaturalist.org/observations/10735658 and https://www.inaturalist.org/observations/75355903 and https://www.inaturalist.org/observations/187595353 and https://www.inaturalist.org/observations/180600325 and https://www.inaturalist.org/observations/178889754 and https://www.inaturalist.org/observations/106267194 and https://www.inaturalist.org/observations/64797073 and https://www.inaturalist.org/observations/57000035 and https://www.inaturalist.org/observations/38611134)

TAIL AMBIVALENT BETWEEN CONSPICUOUS AND INCONSPICUOUS

• O. callotis (https://www.wildlifeofkenya.com/categories/ongulates/oryx-fringe-eared/ and https://www.inaturalist.org/photos/11501181 and https://www.wildlifeofkenya.com/categories/ongulates/oryx-fringe-eared/ and http://www.africaimagelibrary.com/-/galleries/east-africa/kenya/-/medias/ac43d6ae-8fb8-11e1-869a-bbfd1cb35c89-fringed-eared-oryx-oryx-gazella-cullotis-tsavo-east-national and https://www.dreamstime.com/beisa-oryx-gazella-large-antelope-african-savannas-tsavo-national-park-kenya-image112282496)
• O. leucoryx (https://www.inaturalist.org/observations/44228979 and https://www.inaturalist.org/observations/107400400 and https://www.shutterstock.com/image-photo/arabian-oryx-red-sands-desert-conservation-2090606014 and https://www.shutterstock.com/image-photo/endangered-arabian-oryxes-oryx-leucoryx-dubai-432758584 and https://www.inaturalist.org/observations/150909788 and https://www.inaturalist.org/observations/148095412 and https://www.inaturalist.org/observations/148095441)

TAIL INCONSPICUOUS

• O. dammah (https://www.texasmonthly.com/articles/the-end-of-hunting-for-exotic-endangered-antelopes/ and https://www.inaturalist.org/observations/147236685 and https://www.inaturalist.org/observations/152207080 and https://www.inaturalist.org/observations/64778626 and https://www.inaturalist.org/observations/40577816)
• A. nasomaculatus (https://www.gettyimages.co.nz/detail/photo/addax-royalty-free-image/541054728?adppopup=true and https://www.gettyimages.co.nz/detail/photo/pair-of-beasts-royalty-free-image/504838051?adppopup=true and https://www.superstock.com/asset/addax-addax-nasomaculatus-captive-specimen-addax-also-known-white-antelope/1990-12893722 and https://timbavatiwildlifepark.com/animal/addax/)

DISCUSSION

A surprising finding in this comparison is how heterogeneous the colouration is among the various species.

Indeed, there is so much variation in the posteriolateral patterns that

• there is no element of colouration that is shared by all hippotragins; even the most consistent element, viz. pale buttocks, is absent from one species (O. callotis, https://www.alamy.com/stock-photo-fringed-eared-oryx-oryx-gazella-cullotis-tsavo-east-national-park-53906728.html?imageid=B9E093DC-D166-44B4-B67C-FCDE29AE3909&p=22059&pn=1&searchId=4f0dd42eb1a3853d476f41d97adf47e2&searchtype=0 and https://www.alamy.com/herd-of-fringe-eared-oryx-oryx-beisa-callotis-a-large-dry-country-antelope-of-all-sizes-and-ages-in-scrubland-galana-conservancy-kenya-africa-image243259008.html?imageid=39FE63B4-B80E-4080-B66C-F5DECB6FBA79&p=38682&pn=1&searchId=4f0dd42eb1a3853d476f41d97adf47e2&searchtype=0),
• O. gazella and O. beisa resemble Hippotragus as much as members of their own genus, and
• O. leucoryx (https://stock.adobe.com/search?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22oryx+leucoryx%22&order=relevance&safe_search=1&limit=100&search_page=4&search_type=pagination&get_facets=0&asset_id=558824319 and https://www.alamy.com/stock-photo-arabian-oryx-oryx-leucoryx-with-a-calf-oman-73930716.html) resembles A. nasomaculatus (summer coat, https://www.naturepl.com/stock-photo-nature-image01602204.html and https://www.iucn.org/content/saharan-addax-antelope-faces-imminent-extinction-0) more than any member of its own genus.

It has been proposed, in the past, that O. gazella, O. beisa, and O. callotis all belong to a single, geographically disjunct species. Even today, many regard beisa and callotis as conspecific. However, this study of adaptive colouration has revealed categorical differences, suggesting three distinct species.

Only two of the hippotragin species emerge as possessing unambivalent bleezes in posteriolateral view.

These are

• O. gazella, in which the bleeze is so complex (combining rump, tail, buttocks, haunches, and abdomen/lower flanks) that it is difficult to name, and
• H. niger, in which the bleeze is complex in a different way, viz. according to sex and age.

In addition, an argument can be made for a bleeze in A. nasomaculatus in winter coat.

There is one recently extinct species, namely Hippotragus leucophaeus (https://www.nature.com/articles/s41598-020-80142-2).

This seems to have been the plainest-coloured of hippotragins (https://www.pinterest.com.au/pin/afterlife-the-mounted-skin-at-naturalis-leiden-the-netherlands--28288303894067651/ and https://maker-scratchpad-youtube.fandom.com/wiki/Bluebuck?file=Bluebuck.jpg and https://www.alamy.com/bloubok-hippotragus-leucophaeus-with-scale-in-rhineland-size-hippotragus-leucophaeus-bluebuck-draughtsman-robert-jacob-gordon-oct-1777-mar-1786-paper-pen-brush-h-660-mm-w-480-mm-h-260-mm-w-422-mm-h-224-mm-w-421-mm-image472065082.html?imageid=CE54FA6B-7419-4641-BBF7-8FC971D77511&p=1834549&pn=1&searchId=3de7156d478f2302cce398840ed9728d&searchtype=0 and https://www.museumfuernaturkunde.berlin/en/press/press-releases/blue-and-lonesome-rarity-blue-antelopes-museum-collections and https://upload.wikimedia.org/wikipedia/commons/6/66/Bluebuck_by_Allamand%2C_1778.jpg and https://eol.org/media/28755258 and scroll to second photo in https://sportsafield.com/2020/out-of-the-mists-of-time/ and https://www.tumblr.com/thylacine-dreams/167273378400/taxidermy-specimens-of-the-extinct-bluebuck and https://forschungsinfrastruktur.bmbwf.gv.at/en/fi/1-zoologie-mammals_4547).

However, a skin preserved in Paris (https://bioone.org/journals/zoosystema/volume-42/issue-5/zoosystema2020v42a5/The-Paris-Bloubok-Hippotragus-leucophaeus-Pallas-1766-Bovidae-and-its/10.5252/zoosystema2020v42a5.short) suggests that, as in H. equinus,

• the buttocks were whitish, and
• the base, stalk, and small tassel of the tail were dark.

Furthermore, mature males are recorded as having been whitish overall (https://animals.fandom.com/wiki/Bluebuck).

Therefore, it is plausible that H. leucophaeus was somewhat conspicuous in posteriolateral view, and that - partly and in its own way - it emulated H. niger (sexual dimorphism) and O. leucoryx (overall pallor) in its adaptive colouration.

Posted on October 16, 2023 11:04 PM by milewski