The ten most important differences between Alcelaphus cokii and Alcelaphus caama

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See https://www.inaturalist.org/journal/milewski/71135-structure-and-function-of-the-tail-show-that-the-red-hartebeest-alcelaphus-caama-is-a-different-species-from-coke-s-hartebeest-alcelaphus-cokii# and https://www.inaturalist.org/journal/milewski/71167-subtleties-of-adaptive-colouration-in-alcelaphus-cokii-and-alcelaphus-caama#.

On scrutiny, it is surprising that any naturalist, familiar with Alcelaphus cokii (https://www.deviantart.com/okavanga/art/Hartebeest-580725609) and Alcelaphus caama (https://www.alamy.com/stock-photo-the-family-alcelaphus-buselaphus-caama-the-red-hartebeest-is-a-species-119959450.html), continues to see these as belonging to a single species.

Contrary to the conventional view (https://upload.wikimedia.org/wikipedia/commons/4/49/Alcelaphus_recent.png), these are clearly different enough to be separate species, in the following ways.

ANATOMY

• The horns tend horizontal in cokii (https://www.worthpoint.com/worthopedia/cokes-hartebeest-skull-horns-antlers-292005708), vs vertical in caama (https://www.thetaxidermystore.com/african-red-hartebeest-shoulder-taxidermy-mount-for-sale-12553.html).
• The maximum length of the horns is much less in cokii than in caama

cokii male:
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=%22coke%27s+hartebeest%22&order=relevance&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=493604898 and https://stock.adobe.com/search?k=%22coke%27s+hartebeest%22&asset_id=87302482

cokii female:
https://www.inaturalist.org/observations/57486416

caama male:
https://www.inaturalist.org/observations/20885285 and https://www.shutterstock.com/image-photo/adult-red-hartebeest-southern-african-savanna-653300923

caama female:
https://www.shutterstock.com/image-photo/hartebeest-hron-head-detail-grass-namibia-1676326405

• The tail-tassel is restricted to the distal half of the tail in cokii (https://www.inaturalist.org/observations/129505166), vs covering most of the tail in caama (https://www.superstock.com/asset/red-hartebeest-alcephalus-buselaphus-selbornei-adult-male-walking-mountain-zebra/4421-19258).
• The tail-tassel is thin in cokii (https://www.inaturalist.org/observations/18343), vs thick in caama (https://www.shutterstock.com/image-photo/red-hartebeest-alcelaphus-buselaphus-south-africa-44646118 and https://stock.adobe.com/search?k=%22alcelaphus+buselaphus%22&asset_id=19811769).

BEHAVIOUR

• The tail tends to be tucked in cokii (https://www.alamy.com/stock-photo-hardebeest-masai-mara-kenya-57612867.html?imageid=D20F0B88-F5FF-4982-8842-7952AA7331CD&p=50837&pn=1&searchId=9d33360e0bbac7f37d31b4ef65ec260d&searchtype=0), vs held out in caama (https://www.shutterstock.com/image-photo/red-hartebeest-alcelaphus-buselaphus-running-kalahari-51110170), particularly while running (including stotting).

COLOURATION

• The incipient tail-tassel is, in newborns, not black in cokii (https://www.shutterstock.com/image-photo/red-hartebeest-antelope-alcelaphus-buselaphus-young-128772683), vs black in caama (https://www.shutterstock.com/image-photo/newborn-red-hartebeest-looking-over-his-510145570 and https://www.shutterstock.com/image-photo/new-born-baby-red-hartebeest-antelope-39136978).
• The flank is slightly brindled in cokii (https://www.shutterstock.com/image-photo/hartebeest-maasai-mara-kenya-1896708001 and https://www.inaturalist.org/observations/111309212 and https://alchetron.com/Hartebeest), vs not brindled in caama (https://www.inaturalist.org/observations/103899951).
• The crown, nape, temples, forehead, rostrum, shoulders, and haunches lack dark markings in cokii, vs possessing them in caama (https://www.inaturalist.org/observations/104028400 and https://www.inaturalist.org/observations/65998074 and https://www.shutterstock.com/image-photo/backside-view-red-hartebeest-sitting-field-536935192).
• The pale patch on the haunches is not clearly defined in cokii, vs clearly defined (dorsally and ventrally) in caama (https://www.alamy.com/red-hartebeest-alcelaphus-buselaphus-female-with-its-calv-stand-in-savanna-south-africa-mokala-national-park-image255403236.html?imageid=5B6DA9F2-41DC-4461-8884-57B681930DA8&p=851122&pn=1&searchId=5a9d18d908b9a4c9c188c881e40a80e9&searchtype=0).
• The posterior surfaces of all four legs are as pale as the buttocks in cokii (https://www.inaturalist.org/observations/28485278), vs not so in caama (https://www.shutterstock.com/image-photo/red-hartebeest-kgalagadi-transfrontier-national-park-60359125).

DISCUSSION

The naturalist's eye tends naturally to be drawn to the shapes of the horns.

However, it is only when one sees past the obvious differences between cokii and caama, in the orientation of the horns, that the true depth of the interspecific differences is noticed.

There is so little sexual dimorphism in Alcelaphus cokii that it is hard to find, among the thousands of photos on the Web, any view clearly comparing adult male and adult female within a single frame. The closest are:

• scroll in https://andriasconsulting.com/foto_mammals.html
• https://www.shutterstock.com/image-photo/couple-hartebeest-alcelaphus-buselaphus-warning-serengeti-158493701 and https://www.planetstillalive.com/africa/tanzania-ndutu/tanzania-ndutu-mammals/#prettyPhoto[gal]/9/).

However, Alcelaphus caama shows obvious sexual difference in the size of the horns (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=hartebeest&order=relevance&safe_search=1&limit=100&search_page=49&get_facets=0&search_type=pagination&asset_id=203749833).

The differences are even greater in the case of the tail.

In the case of the tail alone, the differences between cokii and caama in anatomy and display are such that they could belong to different genera, not just different species.

The far greater demonstrativeness of the tail, in caama than in cokii, extends to adaptive colouration at the scale of the whole figure:

• Alcelaphus caama (https://stock.adobe.com/uk/search?k=rooihartebees&asset_id=488497821) is specialised for conspicuousness at all distances (by virtue of its combination of a bleeze and a caudal flag), whereas
• Alcelaphus cokii is plain-coloured enough to retain a component of cryptic colouration (https://www.istockphoto.com/photo/cokes-hartebeest-gm921870084-253065765 and 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=hartebeest&order=relevance&safe_search=1&limit=100&search_page=61&search_type=pagination&get_facets=0&asset_id=180909474).

Posted on October 11, 2022 09:29 AM by milewski