The red hartebeest (Alcelaphus caama) shows subtle convergence with a coexisting giraffe (Giraffa giraffa) in darkening for masculine conspicuousness

I have been intimately familiar with Alcelaphus caama for 55 years (please 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#).

However, it is only recently that I have examined a trend to masculine darkening in this species.

This darkening seems similar - albeit less pronounced - to that seen in a giraffe widely coexisting with A. caama, namely Giraffa giraffa.

In this Post, I explore this comparison by means of photos.

GIRAFFA GIRAFFA

Please see https://select.timeslive.co.za/news/2019-10-03-tall-dark-and-lonesome-is-the-secret-to-necking-a-giraffe/

https://www.pond5.com/stock-footage/item/11342963-giraffe-pre-mating-courtship

https://www.shutterstock.com/image-photo/long-distance-view-african-giraffe-during-1833390157

https://upload.wikimedia.org/wikipedia/commons/c/c2/Giraffa_camelopardalis_angolensis_%28mating%29.jpg

https://stock.adobe.com/au/search?k=%22southern+giraffe%22&asset_id=308357181

https://www.istockphoto.com/photo/south-african-giraffe-mating-in-chobe-botswana-safari-gm1173187622-325756164?phrase=mating%20giraffes

https://www.agefotostock.com/age/en/details-photo/south-african-giraffes-giraffa-camelopardalis-giraffa-male-trying-to-smell-female-s-scent-at-waterhole-etosha-national-park-namibia/IBR-4222032

https://www.zoonar.de/photo/sehr-dunkle-giraffe-etoshanationalpark-namibia-very-dark-giraffe-etosha-national-park-namibia_17156553.html

https://www.shutterstock.com/image-photo/dark-walking-giraffe-etosha-national-park-1176916033

https://www.shutterstock.com/image-photo/picture-southern-giraffe-madikwe-game-reserve-614938241

https://www.agefotostock.com/age/en/details-photo/giraffes-giraffa-camelopardalis-adults-young-and-baby-standing-in-dry-grass-etosha-national-park-namibia-africa/WE134102

https://www.shutterstock.com/image-photo/very-dark-tall-giraffe-about-eat-85321780

https://www.shutterstock.com/image-photo/giraffe-watching-over-trees-1431872963

https://parody.fandom.com/wiki/Angolan_Giraffe?file=Angolan_Giraffe_Bull_and_Cow.jpg

https://www.istockphoto.com/photo/south-african-giraffe-mating-in-chobe-botswana-safari-gm1173187682-325756221?phrase=mating%20giraffes

https://www.istockphoto.com/photo/african-giraffe-in-a-south-african-wildlife-reserve-gm1280265018-378620591?phrase=mating%20giraffes
https://www.istockphoto.com/photo/african-giraffe-in-a-south-african-wildlife-reserve-gm1280264967-378620582?phrase=mating%20giraffes
https://www.istockphoto.com/photo/african-giraffe-in-a-south-african-wildlife-reserve-gm1280264981-378620588?phrase=mating%20giraffes

https://www.istockphoto.com/photo/giraffe-mother-and-child-in-etosha-national-park-namibia-gm1147047408-309271822

https://www.agefotostock.com/age/en/details-photo/giraffe-giraffa-camelopardalis-before-mating-south-africa-kruger-np-jul-05/BWI-BLWS024527

https://photos.com/featured/male-giraffe-in-etosha-peter-vruggink.html

https://www.gettyimages.com.au/detail/photo/giraffe-mother-child-royalty-free-image/807870680?phrase=southern%2Bgiraffe

https://www.gettyimages.com.au/detail/photo/southern-giraffe-walking-under-a-cloud-filled-royalty-free-image/521367386?phrase=southern%20giraffe&adppopup=true

ALCELAPHUS CAAMA

The following shows the normal colouration in mature females, in an individual with fully-developed dark markings: https://matlabas.co.za/red-hartebeest/.

The following show female individuals with extremely dark ground-colour: https://www.inaturalist.org/observations/97655537 and First photo in https://www.inaturalist.org/observations/53598380.

The following all show mature males. As in G. giraffa, darkening is seen to a variable degree:

https://upload.wikimedia.org/wikipedia/commons/5/5b/2011-Red-Hartebeest.jpg

https://www.inaturalist.org/observations/103899951

https://www.inaturalist.org/observations/105161555

https://www.inaturalist.org/observations/65883690

https://www.inaturalist.org/observations/116565592

https://www.inaturalist.org/observations/4927264

https://africawild-forum.com/viewtopic.php?t=2674

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=41&search_type=pagination&get_facets=0&asset_id=159368245

https://www.inaturalist.org/observations/58641471

https://www.inaturalist.org/observations/49832745

https://www.inaturalist.org/observations/117556686

https://stock.adobe.com/au/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=%22red+hartebeest%22&order=relevance&safe_search=1&limit=100&search_page=12&search_type=pagination&get_facets=0&asset_id=257383819

https://stock.adobe.com/au/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=%22red+hartebeest%22&order=relevance&safe_search=1&limit=100&search_page=12&search_type=pagination&get_facets=0&asset_id=218606493

https://www.inaturalist.org/observations/116591986

https://www.inaturalist.org/observations/97188632

The following is the darkest specimen I have seen: https://www.inaturalist.org/observations/7583932.

The following specimen, probably about 15 years old with worn horns (one having a broken tip), suggests that males lose their masculine darkness when past their prime: https://www.inaturalist.org/observations/66735467.

DISCUSSION

The convergences between Giraffa giraffa and Alcelaphus caama are subtle, but intriguing.

These two species fall into different categories of adaptive colouration, the former being camouflaged (by virtue of its spots/blotches), and the latter being self-advertising (by virtue of the bleeze on its hindquarters).

Furthermore, G. giraffa is, in full maturity, far more sexually dimorphic in body size than A. caama. In G. giraffa, the ratio of body masses reaches male 1400 kg/female 800 kg, whereas in A. caama it reaches only male 150 kg/female 120 kg.

However, their categorical differences have not precluded certain trends of commonality.

For example,

• in some individuals of females and juveniles, G. giraffa does show a conspicuous pattern vaguely resembling a bleeze on the hindquarters (https://www.gettyimages.com.au/detail/photo/giraffes-in-the-wild-angola-royalty-free-image/1217020338?phrase=southern%20giraffe&adppopup=true and https://www.gettyimages.com.au/detail/photo/african-wildlife-giraffes-burchells-zebras-and-royalty-free-image/1265090301?phrase=southern%20giraffe&adppopup=true and https://www.gettyimages.com.au/detail/photo/full-length-view-of-a-herd-of-giraffe-walking-in-royalty-free-image/1431427867?phrase=southern%20giraffe&adppopup=true and https://stock.adobe.com/au/search?k=%22southern+giraffe%22&asset_id=526719028),
• both species activate a black caudal flag when running (https://www.shutterstock.com/image-photo/running-giraffe-flat-desolate-stone-desert-1566410026 and https://www.alamy.com/stock-photo-red-hartebeest-alcelaphus-buselaphus-running-kgalagadi-transfrontier-29337315.html), and
• in both species, mature males tend to be darker than mature females, this darkness being associated with prime condition and competitive status, rather than age per se.

In the case of G. giraffa, masculine darkening does not seem to compromise camouflage except in extreme cases (extremely darkness in males also being associated with odour so strong that it militates against inconspicuousness).

In the case of A. caama, masculine darkening remains congruent with the species' strategy of gregarious conspicuousness. This is partly because mature males - although not matching the extreme darkening seen in some individuals of G. giraffa (https://stock.adobe.com/au/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=%22southern+giraffe%22&order=relevance&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=512577608 and https://www.alamy.com/stock-photo-a-very-dark-male-southern-giraffe-aka-south-african-giraffe-aka-two-176427950.html and https://stock.adobe.com/au/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=%22southern+giraffe%22&order=relevance&safe_search=1&limit=100&search_page=6&search_type=pagination&get_facets=0&asset_id=506937655 and https://d.facebook.com/528664557465996/photos/a.1181729868826125/1593633254302449/?type=3&source=48) - tend to stand out from the environment by virtue of their darkness alone (https://www.inaturalist.org/observations/133638439).

The convergence between the two species may be partly explained by the fact that G. giraffa is adapted partly to environments so sparsely vegetated that camouflage can be largely redundant (https://www.gettyimages.com.au/detail/photo/desert-giraffe-in-the-hoanib-river-royalty-free-image/839018730?phrase=southern%20giraffe&adppopup=true).

Posted on October 16, 2022 10:30 PM by milewski