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
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://stock.adobe.com/au/search?k=%22southern+giraffe%22&asset_id=308357181
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.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/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://photos.com/featured/male-giraffe-in-etosha-peter-vruggink.html
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://www.inaturalist.org/observations/58641471
https://www.inaturalist.org/observations/49832745
https://www.inaturalist.org/observations/117556686
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 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).
Comments
https://www.dailymail.co.uk/news/article-5914319/Female-hunter-killed-black-giraffe-says-conservation-effort.html
https://parody.fandom.com/wiki/Angolan_Giraffe?file=800px-Giraffa_camelopardalis_angolensis_%2528courting%2529.jpg
https://pixels.com/featured/1-south-african-giraffe-mating-in-chobe-botswana-safari-artush-foto.html?product=acrylic-print
https://www.africahunting.com/threads/dark-giraffe-with-white-head.16420/
https://abc30.com/giraffes-giraffe-study-elephants-university-of-bristol/10932350/
The following shows that fully mature males of Giraffa giraffa retain the pedal flag despite their overall darkening:
https://www.gettyimages.com.au/detail/photo/southern-giraffe-royalty-free-image/1397720944?phrase=southern%20giraffe&adppopup=true
The same is true for mature males of Giraffa tippelskirchi:
https://www.gettyimages.com.au/detail/photo/beautiful-single-giraffe-looking-royalty-free-image/1043212696?phrase=southern%20giraffe&adppopup=true
The following shows that females and juveniles of Giraffa giraffa, at least in the case of some individuals, are so pale that their camouflage is compromised:
https://www.gettyimages.com.au/detail/photo/portrait-of-wild-giraffes-standing-on-field-during-royalty-free-image/1410337761?phrase=southern%20giraffe&adppopup=true
shift
https://www.gettyimages.com.au/detail/photo/close-up-of-southern-giraffe-staring-towards-camera-royalty-free-image/1331906984?phrase=southern%20giraffe&adppopup=true
https://www.youtube.com/watch?v=aVfrGOV3yk8
Close scrutiny of
https://www.shutterstock.com/image-photo/running-giraffe-flat-desolate-stone-desert-1566410026 shows that this individual is defecating. The extremely small fecal pellets - from which water has been thoroughly reabsorbed in the terminal section of the colon - help to explain the tolerance to aridity in giraffes.
https://www.krugerpark.co.za/africa_red_hartebeest.html
https://www.bidpro.co.za/AuctionDetails/47
https://www.facebook.com/528664557465996/posts/world-record-red-hartebeest-this-bulls-name-is-duke-and-his-rowland-ward-is-30-1/755634071435709/
https://dewetswild.com/tag/rooihartbees/
Giraffa tippelskirchi:
https://kingdomstv.com/the-white-and-black-giraffes-the-worlds-rarest-animals/
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&search_page=2&get_facets=0&search_type=pagination&asset_id=524630847
Photo of dark male individual of Giraffa giraffa:
https://www.news24.com/drum/News/Local/ten-cheap-holiday-destinations-in-south-africa-20201211
The following shows that some female individuals have the full expression of darkness on the legs:
https://www.alamy.com/red-hartebeest-suckling-calf-alcelaphus-caama-sub-saharan-africa-image181664514.html?imageid=DA6512A4-9F6B-420D-AD36-CCE88F2E2E75&p=738474&pn=1&searchId=ab9f6fc71ef9b71573c8729d982d6fac&searchtype=0
Two other ruminants that show subtle darkening (particularly on the neck) in masculine maturity are Kobus kob thomasi and Aepyceros melampus.
https://www.inaturalist.org/posts/89498-gaits-and-anti-predator-displays-compared-between-deer-odocoileus-in-north-america-and-impalas-aepyceros-in-africa#activity_comment_ce0ebf14-ff6e-459d-8c9f-675655d585b1
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