Archivos de diario de marzo 2023

01 de marzo de 2023

A previously overlooked difference between the blesbok and the bontebok: pale vs dark tail-tassel

@michalsloviak @geichhorn @colin25 @tandala @dewald2 @simontonge @tonyrebelo @jeremygilmore

The blesbok (Damaliscus pygargus phillipsi) differs from the bontebok (Damaliscus pygargus pygargus) in having a pale distal section to the tail-tassel (https://www.alamy.com/blesbok-damaliscus-pygargus-phillipsi-an-antelope-endemic-to-south-africa-and-swaziland-grazing-in-grassland-image344938371.html).

This difference has not, as far as I know, been noticed by any naturalist or zoologist.

The tail-tassel of both subspecies of Damaliscus pygargus, when intact, reaches to below the hock.

In the bontebok, the whole tail-tassel is always dark (https://www.dreamstime.com/stock-image-bontebok-antelope-image14126791 and https://www.dreamstime.com/royalty-free-stock-photo-bontebok-antelope-image4517985 and https://www.dreamstime.com/royalty-free-stock-image-bontebok-antelope-image20532746 and https://stock.adobe.com/search?k=damaliscus&asset_id=22456309).

However, in the blesbok, the distal part of the tail-tassel tends to be pale:

https://www.gettyimages.no/detail/photo/blesbok-antelopes-in-heat-royalty-free-image/547464562?adppopup=true

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=6&search_type=pagination&get_facets=0&asset_id=173071849

https://stock.adobe.com/search/images?k=blesbok&asset_id=362706450

https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=367831616

https://www.istockphoto.com/photo/blesbok-antelopes-gm540404998-96485023?phrase=pics%20of%20a%20blesbok

https://www.istockphoto.com/photo/blesbok-male-gm542722138-97225053?phrase=pics%20of%20a%20blesbok

https://www.inaturalist.org/observations/85602201

https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=367831595

https://www.inaturalist.org/observations/40397227

https://www.inaturalist.org/observations/42150508

https://www.inaturalist.org/observations/42016467

https://www.dreamstime.com/blesbok-bontebok-damaliscus-pygargus-phillipsi-image196849627

https://www.dreamstime.com/blesbok-bontebok-damaliscus-pygargus-phillipsi-image196849628

Second photo in https://www.inaturalist.org/observations/10850618

https://dewetswild.com/2016/06/23/blesbok/#jp-carousel-52479

https://www.inaturalist.org/observations/19454092

https://www.inaturalist.org/observations/17275768

https://www.inaturalist.org/observations/16062788

https://www.inaturalist.org/observations/132538840

https://www.inaturalist.org/observations/104362803

https://www.inaturalist.org/observations/98375710

https://www.dreamstime.com/stock-photo-blesbok-bull-antelope-standing-veld-image85276090

https://upload.wikimedia.org/wikipedia/commons/3/3a/Damaliscus_pygargus_phillipsi.jpg

https://www.wikiwand.com/en/Dung_midden#Media/File:Blesbok_(Damaliscus_pygargus_phillipsi)_(32413640451).jpg

For an index to my many Posts about the genus Damaliscus, please see https://www.inaturalist.org/journal/milewski/78238-an-index-to-my-posts-on-genus-damaliscus#.

Publicado el marzo 1, 2023 01:40 MAÑANA por milewski milewski | 13 comentarios | Deja un comentario

Previously overlooked expansions of the 'bles' in the blesbok (Damaliscus pygargus phillipsi), signifying full maturity, beyond adulthood

Many photos of the blesbok (Damaliscus pygargus phillipsi) show individuals in which

This spreading of the facial bleeze - which I have not seen mentioned in the literature - may possibly be a sign of age (exceeding ten years). This is indicated by the fact that many of the photos concerned are of captive specimens.

The ultimate result is seen in https://www.inaturalist.org/observations/70027286.

Most of the photos below refer to females, but males also show this pattern (e.g. https://www.inaturalist.org/observations/141372682 and https://www.inaturalist.org/observations/32952125 and https://www.flickr.com/photos/holtphoto/11667853505/in/photolist-iM3Nm2-6TeDse-29Yu8yw-GQHdeu-QzVdjX-e6MgFY-2gjCi6T-H9VkFH-5oDPzj-ASgX6y-H7BJzh-pi4vHm-eYXy2U-5f8mw4-bFbjtX-YaJrFP-pHAQwC-24MnFrZ-71RcCB-csqwjA-3yg1Bw-4GLgxP-6UtPYS-5QZpnc-6DNMdK-37BsTy-dM3YJg-2nbqYFY-275Jw9t-C55EVf-apLdKb-rDKi6z-qtrvU-2nidniQ-o3mr2c-2jjUxYq-2hsDGV3-2hsGrgp-2iGfCyR-HfX4Cz-qtwsg8-ApjDMc-2jfZf6T-zEj283-qpGt6C-bt1qDP-dcWPMW-nQmxok-qFeiSy-2bW3UGB).

We now know of at least three aspects of the colouration of the blesbok that show particular depigmentation, compared to the bontebok (Damaliscus pygargus pygargus), viz.

The pattern on the cheeks, described here, occurs also in the bontebok (https://www.inaturalist.org/observations/27251980). However, it is faint and uncommon in that subspecies.

https://www.dreamstime.com/herd-blesbuck-antelope-standing-dried-out-long-grass-field-landscape-south-african-bushveld-blesbok-antelopes-rocky-dull-image182816487

https://www.dreamstime.com/blesbok-antelope-damaliscus-pygargus-standing-grass-blesbok-antelope-damaliscus-pygargus-standing-grass-pilsen-czech-image181373022

https://www.dreamstime.com/blesbok-lying-grass-blesbok-image265633507

https://www.flickr.com/photos/holtphoto/11667853505/in/photolist-iM3Nm2-6TeDse-29Yu8yw-GQHdeu-QzVdjX-e6MgFY-2gjCi6T-H9VkFH-5oDPzj-ASgX6y-H7BJzh-pi4vHm-eYXy2U-5f8mw4-bFbjtX-YaJrFP-pHAQwC-24MnFrZ-71RcCB-csqwjA-3yg1Bw-4GLgxP-6UtPYS-5QZpnc-6DNMdK-37BsTy-dM3YJg-2nbqYFY-275Jw9t-C55EVf-apLdKb-rDKi6z-qtrvU-2nidniQ-o3mr2c-2jjUxYq-2hsDGV3-2hsGrgp-2iGfCyR-HfX4Cz-qtwsg8-ApjDMc-2jfZf6T-zEj283-qpGt6C-bt1qDP-dcWPMW-nQmxok-qFeiSy-2bW3UGB

https://www.inaturalist.org/observations/128960710

https://www.gettyimages.pt/detail/foto/lonely-african-blesbok-antelope-imagem-royalty-free/93047550?adppopup=true

https://www.inaturalist.org/observations/77675104

https://www.shutterstock.com/it/image-photo/antelope-wild-blesbok-blesbuck-lying-down-2223739221

https://www.superstock.com/asset/blesbok-damaliscus-pygargus-phillipsi-standing-mlilwane-wildlife-sanctuary-swaziland-africa/1566-12911195

https://www.istockphoto.com/photo/blesbuck-in-mlilwane-wildlife-sanctuary-swaziland-gm1182434638-332026999?phrase=blesbok%20male

https://www.shutterstock.com/it/image-photo/blesbok-antelope-damaliscus-pygargus-standing-grass-1329980801

https://www.euro-t-guide.com/See_Photo/Denmark/JUT-M_Grenaa/Ree_Park_Ebeltoft-2008-14.jpg

https://depositphotos.com/635653818/stock-photo-blesbok-blesbuck-damaliscus-pygargus-phillipsi.html

https://www.shutterstock.com/it/image-photo/blesbok-latin-name-damaliskus-dorcas-phillipsi-360070883

https://www.shutterstock.com/it/image-photo/group-blesbuck-mlilwane-wildlife-sanctuary-scenery-1536515885

https://www.shutterstock.com/it/image-photo/blesbok-latin-name-damaliskus-dorcas-phillipsi-290826794

https://www.shutterstock.com/it/image-photo/blesbuck-grazing-on-green-grass-1275827710

https://dewetswild.com/2016/06/23/blesbok/#jp-carousel-52456

https://www.istockphoto.com/photo/blesbuck-in-mlilwane-wildlife-sanctuary-swaziland-gm1182437686-332029264?phrase=blesbok%20male

https://www.inaturalist.org/observations/35368437

https://www.inaturalist.org/observations/124183870

https://www.dreamstime.com/stock-image-blesbok-close-up-antelope-eating-image30613991 and https://www.dreamstime.com/stock-images-blesbok-close-up-antelope-image30613954

Please note the extremely long horns, indicating advanced age, in the central figure in https://www.inaturalist.org/observations/34887688

Also see https://www.inaturalist.org/journal/milewski/75748-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi# and https://www.inaturalist.org/posts/78685-the-overlooked-complexity-of-facial-markings-in-genus-damaliscus#.

For an index to my many Posts about the genus Damaliscus, please see https://www.inaturalist.org/journal/milewski/78238-an-index-to-my-posts-on-genus-damaliscus#.

Publicado el marzo 1, 2023 09:23 TARDE por milewski milewski | 15 comentarios | Deja un comentario

02 de marzo de 2023

Unlike the blesbok, the bontebok (Damaliscus pygargus pygargus) lacks an auricular flag

@jwidness @michalsloviak @tonyrebelo @simontonge @jeremygilmore @oviscanadensis_connerties @tandala @colin25 @beartracker @grinnin @botswanabugs @gigilaidler @christiaan_viljoen

Dear Reader, what do you notice about the ears in the following photos?

Blesbok
https://www.inaturalist.org/observations/70348639

Bontebok
https://www.inaturalist.org/observations/115957749

The adaptive colouration of the two subspecies of Damaliscus pygargus is intriguing.

The bontebok (Damaliscus pygargus pygargus) and the blesbok (Damaliscus pygargus phillipsi) are, in most respects, more and less vivid versions of each other.

Therefore, it would have surprised nobody if a conspicuous feature of colouration in the blesbok were even more conspicuous in the bontebok.

Yet, in the case of the auricular flag, the opposite is the case.

In both subspecies, the posterior surface of the ear pinnae is greyish, apparently owing to the dark skin being sparsely covered with short, pale pelage (https://www.dreamstime.com/royalty-free-stock-images-african-bontebok-antelope-image6502609).

Because this pelage has a sheeny quality, the ear pinnae can appear conspicuously pale in certain illuminations.

And this sheeny pallor, although a small feature relative to the size of the whole animal, can serve as a social signal by virtue of the mobility of the ear pinnae.

The following footage of the blesbok is illustrative:

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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=16&search_type=pagination&get_facets=0&asset_id=554758522

https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=8&search_type=pagination&get_facets=0&asset_id=542644196

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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=16&search_type=pagination&get_facets=0&asset_id=555590119

What is particularly intriguing:

Contrary to expectations, it is the generally duller subspecies, namely the blesbok, that qualifies as possessing an auricular flag, whereas the more vivid subspecies, namely the bontebok, does not.

The failure of the bontebok to qualify for an auricular flag is owing to the following factors:

BLESBOK (see https://www.inaturalist.org/journal/milewski/75748-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi#)

The following show the auricular flag in the blesbok:

https://stock.adobe.com/search?k=damaliscus&asset_id=528793101

https://www.dreamstime.com/stock-photo-blesbuck-late-afternoon-field-blesbok-antelope-endemic-to-south-africa-has-distinctive-white-image77761759

https://www.gettyimages.pt/detail/foto/portrait-of-a-blesbok-eating-grass-imagem-royalty-free/71104635?adppopup=true

https://www.robertharding.com/preview/764-6027/blesbok-damaliscus-pygargus-phillipsi-male-chasing-mountain-zebra/

https://www.gettyimages.pt/detail/fotografia-de-not%C3%ADcias/blesbok-in-the-bioparc-valencia-november-07th-fotografia-de-not%C3%ADcias/1440188664?adppopup=true

Third photo in https://www.inaturalist.org/observations/141372682

Second photo in https://www.inaturalist.org/observations/41711968

https://www.inaturalist.org/observations/146961908

https://www.inaturalist.org/observations/107178201

Scroll to second photo in http://cameratrap.mywild.co.za/2012/02/more-herbivores-at-suikerbosrand.html

https://stock.adobe.com/search?k=damaliscus&asset_id=574779666

https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=441942924

https://stock.adobe.com/search?k=damaliscus&asset_id=32501730

https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=447452844

https://upload.wikimedia.org/wikipedia/commons/2/22/Damalicus_pygargus_phillipsi_Dvur_zoo_2.jpg

https://www.inaturalist.org/observations/32226381

https://www.stockfreeimages.com/388844/Blesbok.html

https://upload.wikimedia.org/wikipedia/commons/1/13/Barcelona-Zoo-Damalisco_de_frente_blanca_%28Damaliscus_dorcas_phillipsi%29_%28I%29.jpg

https://www.gettyimages.pt/detail/foto/blesboks-running-imagem-royalty-free/90498079?adppopup=true

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&search_page=2&get_facets=0&search_type=pagination&asset_id=544432988

Third photo in https://www.inaturalist.org/observations/10869372

https://www.inaturalist.org/observations/10805336

https://www.gettyimages.pt/detail/foto/blesbok-antelopes-in-swaziland-imagem-royalty-free/92951908?adppopup=true

https://www.euro-t-guide.com/See_Photo/Denmark/JUT-M_Grenaa/Ree_Park_Ebeltoft-2008-14.jpg

https://depositphotos.com/635653818/stock-photo-blesbok-blesbuck-damaliscus-pygargus-phillipsi.html

https://www.inaturalist.org/observations/56204460

https://de.wikipedia.org/wiki/Buntbock#/media/Datei:Damaliscus_pygargus_-_R%C3%A9serve_africaine_de_Sigean_02.jpg

Scroll to seventh photo in https://www.dailymaverick.co.za/article/2022-12-07-mountain-zebra-national-park-back-from-the-brink/

https://www.inaturalist.org/observations/147672580

https://www.mindenpictures.com/stock-photo-blesbok-damaliscus-dorcas-phillipsi-adult-female-with-calf-malolotja-naturephotography-image80144737.html

https://www.inaturalist.org/observations/108296682

https://www.istockphoto.com/photo/african-blesbok-antelope-gm541305272-96817503

https://www.istockphoto.com/photo/two-beautiful-blesboks-gm1388891630-446375145?phrase=blesbok%20male

https://www.shutterstock.com/it/image-photo/blesbok-blesbuck-damaliscus-dorcas-phillipsi-497011039

https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=8&search_type=pagination&get_facets=0&asset_id=252055834

https://stock.adobe.com/search/images?k=blesbock&asset_id=32186683

BONTEBOK

The following show that, in the bontebok, there is a hint of the same pattern.

https://upload.wikimedia.org/wikipedia/commons/f/f8/Bontebok_PA020073.JPG

https://www.inaturalist.org/observations/84604329

https://www.gettyimages.pt/detail/foto/oryx-imagem-royalty-free/974402214?adppopup=true

https://www.shutterstock.com/it/image-photo/endangered-bontebok-antelope-damaliscus-pygargus-dorcas-572224153

Scroll to sixth photo in https://www.melozhori.co.za/fun-facts-about-bontebok/

Second photo inhttps://www.inaturalist.org/observations/63340921

https://stock.adobe.com/search?k=damaliscus&asset_id=437876858

https://www.inaturalist.org/observations/99715628

Third photo in https://www.inaturalist.org/observations/104349170

https://www.inaturalist.org/observations/71049460

https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=221437252

https://fototravel.net/licencias/damaliscus-dorcas-dorcas-sudafrica/

https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=7&search_type=pagination&get_facets=0&asset_id=271748452

https://www.inaturalist.org/observations/114683864

Scroll to third photo in https://www.goodthingsguy.com/environment/the-bontebok-brought-back-from-the-edge-of-extinction/

https://www.inaturalist.org/observations/128976508

https://www.inaturalist.org/observations/115214084

https://depositphotos.com/240206084/stock-photo-bontebok-antelope-southern-african-savanna.html

https://www.inaturalist.org/observations/136011434

https://www.inaturalist.org/observations/115175564

Scroll to second photo in https://www.monaconatureencyclopedia.com/damaliscus-dorcas/?lang=en

https://www.inaturalist.org/observations/97174996

https://www.inaturalist.org/observations/59053711

https://www.inaturalist.org/observations/75893694

https://www.inaturalist.org/observations/115550547

https://www.inaturalist.org/observations/39079379

https://www.inaturalist.org/observations/22321093

https://www.inaturalist.org/observations/27817980

https://www.inaturalist.org/observations/34601885

https://www.inaturalist.org/observations/31418950

https://www.inaturalist.org/observations/63459199

https://www.inaturalist.org/observations/24374180

https://www.inaturalist.org/observations/23198842

https://www.inaturalist.org/observations/10796733

https://www.inaturalist.org/observations/11166243

https://www.inaturalist.org/observations/45157961

https://www.inaturalist.org/observations/80650367

https://www.inaturalist.org/observations/61544194

https://www.inaturalist.org/observations/70047849

https://www.inaturalist.org/observations/69368070

https://www.inaturalist.org/observations/99626194

The following of the bontebok nearly qualify as showing an auricular flag:

https://stock.adobe.com/search/images?k=blesbock&asset_id=432947109.

https://www.inaturalist.org/observations/148322103

DISCUSSION

The comparison can be summarised by means of the following photo-pair.

Blesbok
https://www.inaturalist.org/observations/32226381

Bontebok
https://www.inaturalist.org/observations/30830045

Were it the case that the bontebok was the sole form of Damaliscus pygargus, probably nobody would have noticed the colouration of its ear pinnae, at all.

However, the noticeable 'flashing' of the ears in the blesbok has set up a search-image. According to the standard set by the blesbok, the bontebok falls short.

There are thousands of photos of the bontebok on the Web, but few come close to showing the clarity and consistency of the auricular flag seen in this view of the blesbok: https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbock&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=142342741.

The following pair of photos of the blesbok shows the full difference produced by angle of illumination, via the sheeny quality of the pelage on the posterior surface of the ear pinna:

https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=8&search_type=pagination&get_facets=0&asset_id=362066099 versus https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=8&search_type=pagination&get_facets=0&asset_id=256689589

The following shows the difference, within a single specimen (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=damaliscus&order=relevance&safe_search=1&search_page=9&get_facets=0&search_type=pagination&asset_id=10848983).

A possible explanation for the lack of an auricular flag in the bontebok is that the behaviours of the two subspecies differ.

The blesbok habitually head-nods (https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbock&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=415281887 and https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbock&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=415281850 and https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbock&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=7&search_type=pagination&get_facets=0&asset_id=415281880).

It does this to an extent and with a frequency that I have not noticed in the bontebok.

Head-nodding, as well as standing in the midday sun with the head lowered and the ears drooping, would tend to display the auricular flag (https://depositphotos.com/154297952/stock-video-blesbok-antelopes-in-grassland.html and https://www.dreamstime.com/stock-photo-cattle-bontebok-antelopes-south-africa-safari-tala-game-reserve-image45175407 and https://stock.adobe.com/search/images?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=damaliscus&order=relevance&safe_search=1&limit=100&search_page=8&search_type=pagination&get_facets=0&asset_id=566483214).

For an index to my many Posts about the genus Damaliscus, please see https://www.inaturalist.org/journal/milewski/78238-an-index-to-my-posts-on-genus-damaliscus#.

Publicado el marzo 2, 2023 06:18 TARDE por milewski milewski | 44 comentarios | Deja un comentario

03 de marzo de 2023

Do blesbok and bontebok differ enough in sexual dimorphism to be different species?

@paradoxornithidae @simontonge @matthewinabinett @katebraunsd @jwidness

I have been closely familiar with Damaliscus pygargus for many decades.

More than half a century ago, I was already sketching both subspecies with as much precision as possible, based on the limited photographic material available at the time.

Furthermore, I have collected what is perhaps the largest dossier of hard-copy photos of the blesbok (https://dewetswild.com/2016/06/23/blesbok/) and the bontebok (https://dewetswild.com/2018/02/02/bontebok/) in the world, clipped from brochures, books, and every other pre-electronic source available.

So, it should be hard to surprise me with any aspect of the appearance of the blesbok and the bontebok.

However, it was only in the last week, when I took the trouble to scrutinise every one of the thousands of relevant photos on the Web, that several surprisingly large differences dawned on me.

In recent Posts, I have covered the

Now, in this Post, I would like to point out a surprising difference in sexual dimorphism between blesbok and bontebok - which, together with the other differences, seems to indicate that these are full species, not merely subspecies.

SEXUAL DIMORPHISM IN BODY MASSES

The blesbok is said to be about 8 kg heavier than the bontebok (https://animaldiversity.org/accounts/Damaliscus_pygargus/). However, this is misleading.

What seems more accurate is that the blesbok and the bontebok are like-size in the case of the more important sex in physiological/metabolic/ecological terms, namely females. It is the fully mature males that seem to differ, owing to the development of extra brawn (particularly on the neck) in males of the blesbok.

The facts of body mass are as follows.

The body mass of the blesbok is given in https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7479364/. The mean was 58 kg, for a sample of eight adult female individuals in good condition.

Huntley (1971, https://www.sasas.co.za/journals/carcass-composition-of-mature-male-blesbok-and-kudu/) reports the mean body mass of mature males of the blesbok as 73.4 kg (sample size was 22 individuals). This varied from 68 kg at the height of the dry season (October, sample size = 5) to 78 kg in the green season (January, sample size = 6).

As reported by Jordaan (https://scholar.sun.ac.za/handle/10019.1/107823), on page 51:
According to Hoffman et al. (2008, https://www.sciencedirect.com/science/article/abs/pii/S0889157508000094), mean body mass for the blesbok was 67.4 kg, for a large sample (65 individuals) of females and males combined.

Smit (2004, Master of Consumer Science thesis, University of Stellenbosch) reports in her Summary that the mean body mass of the blesbok is 60.2 kg for adult females and 67.4 kg for adult males (sample size was collectively 73 individuals).

On page 9 of the same thesis, she states that "The mean live weight for blesbok males is 62.7 to 95.3 kg, and for females is 59.5 to 86.3 kg," I assume that she really means the ranges of individual masses, not the averages.

Other, less helpful references on body masses include the following:

Turning now to the bontebok:

Jordaan (2020, Table 3.1 on page 47) provides definite data for the body mass of adult males of the bontebok. The sample size was 20 individuals, and the mean was 65.8 kg.

The mean body mass of adult males of the bontebok is informally said to be 61 kg (https://www.blueplanetbiomes.org/bontebok.php).

I doubt the following, which seem exaggerated:

SEXUAL DIMORPHISM IN THE SIZE OF THE HEAD

The head, including the horns, is noticeably larger in mature males of the blesbok than in

  • mature males of the bontebok, or
  • adult females of either blesbok or bontebok.

Van Zyl and Ferreira (2004) state that the mean mass of the head in adult females of the blesbok is about 3.5 kg. This is 6% of body mass.

Jordaan (2020, Table 3.1 on page 47) states that the mean mass of the head in adult males of the bontebok is 4.8 kg. This is 7% of body mass.

I have yet to see corresponding data for fully mature males of the blesbok. However, I suspect that the values exceed 7 kg and 8.5%.

Please compare the proportional sizes of the head in the following figures, standardised by posture:

Blesbok adult male:

https://www.flickr.com/photos/natureshots123/4525625905/in/photolist-7TV1UR-V4E7DZ-2hSfrAk-PKmG8V-YYkeDg-8cdsKb-2KtjvS-8xnKrN-pxJ6q-KxWtKy-7TYfPu-4DP9n2-MU1Bub-daY6w9-UdwFcv-2kYpdWN-7PgBip-dt8gki-2iPJUN6-2jsBqyX-2jg3cmm-84ziXU-oGhA1T-z8RMkU-AFikPb-5DUcDf-5DPWaM-at6mq5-iM3Nm2-6TeDse-29Yu8yw-GQHdeu-QzVdjX-e6MgFY-2gjCi6T-H9VkFH-5oDPzj-ASgX6y-H7BJzh-pi4vHm-eYXy2U-5f8mw4-bFbjtX-YaJrFP-pHAQwC-24MnFrZ-71RcCB-csqwjA-3yg1Bw-4GLgxP

Bontebok adult male:

https://www.inaturalist.org/observations/71049461

Bontebok adult female:

https://www.inaturalist.org/observations/78211094

https://www.inaturalist.org/observations/76594512

DISCUSSION

Adult females, the most important category biologically, seem to be like-size in the bontebok and the blesbok.

In the case of mature males, the available data imply that the bontebok is indeed (as claimed in https://animaldiversity.org/accounts/Damaliscus_pygargus/) smaller-bodied than the blesbok - the mean values being about 66 kg and 75 kg respectively. In full maturity, males of the blesbok have been known to surpass 95 kg.

Based on the above information, I suggest that

  • in both the blesbok and the bontebok, mean body mass of adult females is about 60 kg,
  • in the blesbok, mean body mass of mature males is about 75 kg, whereas
  • in the bontebok, mean body mass of mature males is only about 66 kg.

What seems to have been overlooked by previous authors is that males grow stouter (particularly head and neck) with full maturity in the blesbok than in the bontebok.

In other words, I suggest that it is not so much that the bontebok is smaller than the blesbok; it is more that the former is less sexually dimorphic than the latter.

To get an idea of the scale of the differences involved, we can compare adult male blesbok with adult female bontebok, as follows.

https://upload.wikimedia.org/wikipedia/commons/8/84/Blesbok%2C_Damaliscus_pygargus_phillipsi%2C_at_Krugersdorp_Game_Reserve%2C_Gauteng%2C_South_Africa_%2826872993194%29.jpg

https://www.inaturalist.org/observations/51830740

Dear reader, to appreciate this maximum contrast, please toggle back-and-forth between https://upload.wikimedia.org/wikipedia/commons/8/84/Blesbok%2C_Damaliscus_pygargus_phillipsi%2C_at_Krugersdorp_Game_Reserve%2C_Gauteng%2C_South_Africa_%2826872993194%29.jpg and https://www.inaturalist.org/observations/51830740.

In particular, please note the relative size of the head in each case.

Now, please note the stoutness/stockiness, and proportionately large head, of the following mature male specimen of the blesbok. Has any reader ever seen such proportions in the bontebok?

https://www.shutterstock.com/it/image-photo/bontebok-antelope-looking-food-on-plateau-2156944039

https://www.shutterstock.com/it/image-photo/bontebok-antelope-looking-food-on-plateau-2156181097

The following is fairly typical of mature males of the bontebok. The body-proportions resemble those of females of the blesbok, and the horns are also noticeably smaller than in the blesbok:

https://www.shutterstock.com/it/image-photo/bontebok-antelope-national-park-south-africa-124597060

Overall:

The facts remain somewhat elusive. However, my impression is that the blesbok and the bontebok are about as biologically different from each other as are the tsessebe (Damaliscus lunatus/superstes) and the topi (Damaliscus korrigum/topi/jimela/tiang, https://en.wikipedia.org/wiki/Damaliscus_lunatus).

If these realisations stand up to scrutiny, perhaps we should classify the blesbok and the bontebok as separate (albeit interfertile) species, viz. Damaliscus phillipsi and Damaliscus pygargus?

ADDITIONAL PHOTO-COMPARISONS, STANDARDISED BY POSTURE AND PERSPECTIVE

Blesbok adult male
https://www.alamy.com/stock-photo-bontebok-ram-portrait-south-africa-11776145.html?imageid=AF7DC680-2009-4423-A70C-A4488AE280B8&p=34420&pn=1&searchId=798d07205e132c3bcbdbb01855d0a786&searchtype=0

Blesbok adult male
https://www.istockphoto.com/photo/blesbok-antelope-gm497409595-41786378?phrase=pics%20of%20a%20blesbok

Blesbok adult male
https://es.123rf.com/photo_27663869_a-blesbok-antelope-damaliscus-pygargus-standing-in-grassland-south-africa.html

Blesbok adult male
https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbock&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=9&search_type=pagination&get_facets=0&asset_id=165284154

Bontebok adult male
https://www.istockphoto.com/photo/bontebok-antelope-gm145835178-5566402?phrase=pics%20of%20a%20blesbokhttps://www.istockphoto.com/photo/blesbok-antelope-gm523614266-92004719?phrase=pics%20of%20a%20blesbok

Bontebok adult male
https://stock.adobe.com/search/images?k=blesbock&asset_id=103184585

Blesbok adult female
http://www.safaribound.co.za/wp-content/uploads/2015/12/Blesbok.jpg

Blesbok adult female
https://www.flickr.com/photos/keith_burton/52595849483/in/photolist-VQ5V7G-21YXkXk-a2fBQc-C9AkZj-2hknz3d-2o8HtD6-aktLVQ-do2Jrp-kDZnDZ-akqZ3V-akqYN8-6XJngW-aktKRb-2g82zPy-2EwKKK-9ZMSZy-2hRmQoU-GSofrF-2jawJah-Hg63fU-bpxo9b-akqXjc-kDZnJt-8UcSMq-Sgocj4-2hdX4hz-2hRvAAH-2nqxXKA-2k7THja-2nFTwAK-NtcqZw-2mKwoFx-K9H7kw-2nYaeMv-2jbEesL-2jbJeMK-NwubQy-FGdmr3-CMZ9sW-2mVjjPf-ThNHJU-21La8WY-8xnKqU-eMntC3-KA9iEt-2kYpdSu-bsgrmu-2jxYMd5-b3zx7T-2hQhV25

Blesbok adult female
https://www.istockphoto.com/photo/blesbok-damaliscus-pygargus-phillipsi-gm487763834-73141255?phrase=pics%20of%20a%20blesbok

Bontebok adult female
https://www.istockphoto.com/photo/bontebok-gm151545556-10145249?phrase=pics%20of%20a%20blesbok

Bontebok adult female
https://www.istockphoto.com/photo/bontebok-antelope-gm182930579-14039835?phrase=pics%20of%20a%20blesbok

For an index to my many Posts about the genus Damaliscus, please see https://www.inaturalist.org/journal/milewski/78238-an-index-to-my-posts-on-genus-damaliscus#.

Publicado el marzo 3, 2023 09:32 MAÑANA por milewski milewski | 15 comentarios | Deja un comentario

A photo-comparison of bleezes and flags in the blesbok versus the bontebok

(writing in progress)

The following photo-pair shows the two subspecies in posteriolateral view.

Both have a facial bleeze, that of the blesbok being proportionately larger owing to the difference in the relative sizes of the head.

The bontebok has an extremely well-developed pedal flag, whereas this individual of the blesbok, viewed in this perspective, lacks a pedal flag.

The pygal flag of the blesbok is replaced by a pygal bleeze in the bontebok.

In the blesbok, the abdominal and ulnar flags are separate, but in the bontebok there is a white ventral panel that subsumes both the abdominal and the ulnar pattern.

Blesbok
https://www.flickr.com/photos/dorneyphoto/49990958018/in/photolist-2jawJah-Hg63fU-bpxo9b-akqXjc-kDZnJt-8UcSMq-Sgocj4-2hdX4hz-2hRvAAH-2nqxXKA-2k7THja-2nFTwAK-NtcqZw-2mKwoFx-K9H7kw-2nYaeMv-2jbEesL-2jbJeMK-NwubQy-FGdmr3-CMZ9sW-2mVjjPf-ThNHJU-21La8WY-8xnKqU-eMntC3-KA9iEt-2kYpdSu-bsgrmu-2jxYMd5-b3zx7T-2hQhV25-jyHrKJ-2k5VFg7-5sqULW-2fkJEYZ-2kPChVk-21DVXBL-dRVYii-2kvQbEc-yRBxjS-EjKxsR-7cWLgq-21oyHh4-oD1wzM-eijdtU-2gmKAXS-7y3c7F-frYRFL-MdmiNW

Bontebok
https://www.inaturalist.org/observations/130669553

POSTERIOLATERAL VIEW

Blesbok
https://www.inaturalist.org/observations/5141221 and https://www.inaturalist.org/observations/10924282

Blesbok
https://www.inaturalist.org/observations/31573500

Blesbok
https://www.inaturalist.org/observations/85742476

Blesbok
https://www.inaturalist.org/observations/7916986

Blesbok
https://www.inaturalist.org/observations/71536880

Adult male bontebok
https://www.inaturalist.org/observations/115575412

https://www.inaturalist.org/observations/110874507

(writing in progress)

For an index to my many Posts about the genus Damaliscus, please see https://www.inaturalist.org/journal/milewski/78238-an-index-to-my-posts-on-genus-damaliscus#.

Publicado el marzo 3, 2023 12:47 TARDE por milewski milewski | 7 comentarios | Deja un comentario

04 de marzo de 2023

Adaptive colouration in the blesbok (Damaliscus pygargus phillipsi), part 2: infants, juveniles, and adolescents

...continued from https://www.inaturalist.org/journal/milewski/75748-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi-part-1-adults#

The blesbok has uniform pale colouration at birth, which differs categorically from that of adults.

In juveniles of Damaliscus pygargus, the facial colouration is the inverse of that of adulthood, with the facial bleeze beginning dark, and the adjacent cheeks beginning pale (https://www.dreamstime.com/stock-photo-blesbuck-late-afternoon-field-blesbok-antelope-endemic-to-south-africa-has-distinctive-white-image77761757 and https://www.dreamstime.com/stock-photo-blesbuck-late-afternoon-field-blesbok-antelope-endemic-to-south-africa-has-distinctive-white-image77761766).

INFANTS (birth to three months old, including first appearance of horns)

The colouration of infants of the blesbok is categorically different from that of adults.

The ground-colour (including the posterior surfaces of the ear pinnae) is pale, with countershading. The countershading includes the ventral surface of the neck.

The tail-tassel is merely incipient.

The only distinct pattern is seen on the face, where the ground-colour of the rostrum and upper lips is crisply separated from whitish cheeks. Whitish extends on to the orbits except for the anterior side of the orbits (https://www.zoobrno.cz/en/our-animals/animals-kept/mammals/2019-01-17-damaliscus-pygargus-phillipsi and https://www.zooborns.com/zooborns/2016/07/how-to-feed-a-baby-blesbok.html and https://www.zooborns.com/.a/6a010535647bf3970b016764fa98c6970b-popup).

This is, in a sense, the opposite pattern from that in adults (https://www.gettyimages.no/detail/news-photo/newborn-blesbok-calf-born-on-12-july-2013-rests-in-the-news-photo/1041931828?adppopup=true).

There is also

https://www.shutterstock.com/it/image-photo/blesbuck-newborn-baby-89983321

https://www.shutterstock.com/it/image-photo/blesbok-blesbuck-calf-stays-close-members-1671765892

https://www.shutterstock.com/it/image-photo/blesbok-mother-small-calf-leaning-against-91405400

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=49622738

https://www.gettyimages.no/detail/photo/blesboks-royalty-free-image/74077088?adppopup=true

https://www.gettyimages.com.au/detail/photo/blesboks-royalty-free-image/74077088?phrase=blesbok&adppopup=true

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=410239969

https://www.gettyimages.no/detail/photo/female-blesbok-with-a-cream-coloured-calf-at-day-royalty-free-image/1073695294?adppopup=true

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=410240019

https://www.inaturalist.org/observations/10039715

https://www.inaturalist.org/observations/87530537

https://www.inaturalist.org/observations/41711968

https://unsplash.com/photos/ODftot2S_8g

https://www.robertharding.com/preview/741-3687/blesbok-damaliscus-dorcas-kariega-game-reserve-south-africa/

The maximum body size reached by offspring within the infantile colouration is shown in https://www.alamy.com/stock-photo-female-blesbok-damaliscus-pygargus-phillipsi-with-young-african-animal-52703461.html and the second photo in https://www.inaturalist.org/observations/151282742. At this stage the weight of infant/juvenile is about one quarter of maternal weight.

JUVENILES

3-6 months old:

The rostrum, and to lesser degree the upper foreleg, abruptly turn dark (https://www.alamy.com/stock-photo-juvenile-south-african-blesbok-or-blesbuck-antelope-damaliscus-pygargus-87544610.html).

This produces a temporary 'inverse' version of the facial bleeze.

The following, of adult female and juvenile (?4.5 months old) of the blesbok, is one of the clearest illustrations of the conspicuous facial pattern suddenly adopted by juveniles, after three months of infantile colouration. This conspicuous pattern is the inverse of the adult pattern, in that the rostrum is dark while the cheeks are pale:
https://pixabay.com/photos/africa-animals-blesbok-herd-2643568/

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=4&search_type=pagination&get_facets=0&asset_id=545134999

https://www.alamy.com/blesbok-damaliscus-pygargus-phillipsi-lamb-leaping-mountain-zebra-image65490846.html?imageid=143E1B78-F9A0-4910-9888-57EADFEA42CE&p=94604&pn=1&searchId=187c1df722ae1d0911e278a028824aaf&searchtype=0

https://www.alamy.com/juvenile-blesbok-damaliscus-pygargus-phillipsi-mountain-zebra-national-image65490812.html?imageid=E925F6B0-7DB8-4381-90A4-A1DB36C2A783&p=94604&pn=1&searchId=34a5985d254a7cecee5d7188055b6b4c&searchtype=0

https://www.alamy.com/blesbok-damaliscus-pygargus-phillipsi-ewe-and-lamb-mountain-zebra-image65490822.html?imageid=5FF38309-94A5-4D21-AAEA-4777C2D4463D&p=94604&pn=1&searchId=34a5985d254a7cecee5d7188055b6b4c&searchtype=0

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=4&search_type=pagination&get_facets=0&asset_id=545134999https://www.mediastorehouse.com/ardea-wildlife-pets-environment/asw-4602-1300433.html

https://www.mediastorehouse.co.uk/worldinprint/blesbok-damaliscus-pygargus-phillipsi-ewe-lamb-9643399.html

https://www.istockphoto.com/photo/very-cute-blesbok-antelope-juvenile-baby-laying-at-its-mothers-feet-on-the-ground-gm1367508274-437740167?phrase=pics%20of%20a%20blesbok

https://www.alamy.com/juvenile-blesbok-damaliscus-pygargus-phillipsi-mountain-zebra-national-image65490807.html?imageid=B8EA5253-B43F-41C0-8B90-B1BD0FE8E257&p=94604&pn=1&searchId=34a5985d254a7cecee5d7188055b6b4c&searchtype=0https://www.gettyimages.no/detail/photo/blesbok-antelope-royalty-free-image/95006564?adppopup=true

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=221414983

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=200580481

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=0&filters%5Bcontent_type%3Atemplate%5D=0&filters%5Bcontent_type%3A3d%5D=0&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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=9&search_type=pagination&get_facets=0&asset_id=56932934

https://www.agefotostock.com/age/en/details-photo/juvenile-blesbok-damaliscus-pygargus-phillipsi-mountain-zebra-national-park-south-africa-africa/RHA-764-4222/1

https://www.agefotostock.com/age/en/details-photo/juvenile-blesbok-damaliscus-pygargus-phillipsi-mountain-zebra-national-park-south-africa-africa/RHA-764-4226/1

About eight months old (see https://journals.co.za/doi/pdf/10.10520/EJC116862 ):

Whitish hairs appear on the rostrum, creeping upwards from the nose. Countershading disappears from the neck.

https://upload.wikimedia.org/wikipedia/commons/2/23/Blesbok_sa_2003.jpg

https://www.inaturalist.org/observations/122366216

https://stock.adobe.com/images/three-alert-blesbok-standing-on-dry-winter-grassland-landscape/168842499?as_campaign=ftmigration2&as_channel=dpcft&as_campclass=brand&as_source=ft_web&as_camptype=acquisition&as_audience=users&as_content=closure_asset-detail-page

https://www.shutterstock.com/it/image-photo/blesbuck-143669233

https://www.istockphoto.com/photo/spring-joy-gm157229462-22242556?phrase=pics%20of%20a%20blesbok

https://www.alamy.com/blesbok-damaliscus-pygargus-phillipsi-young-walking-in-open-grassland-alert-mountain-zebra-national-park-eastern-cape-south-africa-africa-image229930038.html

https://www.agefotostock.com/age/en/details-photo/blesbok-damaliscus-pygargus-phillipsi-young-walking-in-open-grassland-alert-mountain-zebra-national-park-eastern-cape-south-africa-africa/ZI6-3207756

https://www.istockphoto.com/photo/female-and-male-blesbok-gm462033577-32318952?phrase=pics%20of%20a%20blesbokhttps://www.dreamstime.com/blesbok-antelope-blesbok-standing-southern-african-savanna-image107648592

https://www.dreamstime.com/stock-images-young-blesbok-side-walking-past-image32075944

https://www.agefotostock.com/age/en/details-photo/blesbok-damaliscus-dorcas-phillipsi-calf-walking-in-highveld-grassland-malolotja-n-p-swaziland/FHR-10014-00021-125

8-12 months old:

At about one year old, pale appears on the forehead (individually variable). The rostrum (now pale) and tail-tassel (dark since birth) remain proportionately shorter than in adults.

https://www.dreamstime.com/group-four-blesbok-antelope-stand-green-grass-field-one-them-grazing-others-looking-camera-trees-wildness-image182263733

https://www.inaturalist.org/observations/11088490

ADOLESCENTS (1-2 years old, see https://journals.co.za/doi/pdf/10.10520/EJC116862)

Among the last features to form fully is the whitish patch on the forehead.

https://www.inaturalist.org/observations/66790174

https://www.dreamstime.com/blesbok-antelope-blesbok-southern-african-savanna-image107648073

https://www.dreamstime.com/stock-photo-blesbok-antelope-natural-habitat-damaliscus-pygargus-south-africa-image91058354

https://www.gettyimages.com.au/detail/photo/blesbok-antelope-royalty-free-image/497309877?phrase=blesbok&adppopup=true

https://www.agefotostock.com/age/en/details-photo/two-blesbok-damaliscus-pygargus-phillipsi-mountain-zebra-national-park-south-africa-africa/RHA-764-989/1

ADULTS (>2 years old, see https://journals.co.za/doi/pdf/10.10520/EJC116862)

https://www.shutterstock.com/it/image-photo/blesbok-blesbuck-damaliscus-dorcas-phillipsi-497011045

https://www.robertharding.com/preview/743-343/blesbok-damaliscus-dorcas-phillipsi-mountain-zebra-national-park/

Fully mature adults:

See https://www.inaturalist.org/journal/milewski/75871-a-previously-overlooked-aspect-of-the-bles-of-the-blesbok-signifying-full-maturity-within-adulthood#

DIFFERENCES FROM THE BONTEBOK

I have noticed then following tentative differences, which depend on further photographic evidence for verification:

Perhaps the most significant finding:

Juveniles, 3-6 months old, have more conspicuous facial colouration in the blesbok than in the bontebok. This is the inverse of the relationship between these two taxa in adulthood, at the scale of the whole figure.

This unexpected difference hints that the blesbok and the bontebok are actually different species, not merely subspecies of the same species.

Also see https://www.inaturalist.org/journal/milewski/76336-adaptive-colouration-in-the-bontebok-damaliscus-pygargus-pygargus-part-2-infants-juveniles-and-adolescents#.

For an index to my many Posts about the genus Damaliscus, please see https://www.inaturalist.org/journal/milewski/78238-an-index-to-my-posts-on-genus-damaliscus#.

Publicado el marzo 4, 2023 12:11 MAÑANA por milewski milewski | 19 comentarios | Deja un comentario

11 de marzo de 2023

Adaptive colouration in the bontebok (Damaliscus pygargus pygargus), part 1: adults

Also see https://www.inaturalist.org/journal/milewski/75748-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi-part-1-adults#

The bontebok (Damaliscus pygargus pygargus) is one of the most vividly-coloured wild ungulates on Earth.

However, its colouration has not previously been described coherently, relative to a conceptual framework based on adaptation. Furthermore, previous descriptions have been limited by the lack of suitable terms.

A reminder of the difference between a bleeze and a flag:

A bleeze is a large-scale feature of colouration, so bold that it makes the whole figure conspicuous even at a distance, and even when the animal is stationary.

A flag is a relatively small, or normally hidden, feature of colouration, which becomes conspicuous with motion.

The bontebok can be described as 'pied' (https://dictionary.cambridge.org/dictionary/english/pied). However, this is unsatisfactory, because

  • it does not elucidate the functional organisation of the markings, and
  • it does not distinguish between an adaptive design and that seen in pied individuals and breeds of domestic mammals (https://en.wikipedia.org/wiki/Piebald).

Various wild ungulates possess bleezes. However, what makes the bontebok unusual is that

In this account, I ignore the hues on the pelage of the bontebok, and consider only the tones (white, shades of grey, and black). This is because ungulates and their carnivoran predators do not perceive hues in the same ways as humans do.

OVERALL VIEWS

https://www.shutterstock.com/it/image-photo/walking-field-bontebok-mediumsized-generally-dark-484356043

https://www.inaturalist.org/observations/11251852

https://www.dreamstime.com/bontebok-damaliscus-pygargus-image129038646

https://www.alamy.com/stock-photo-bontebok-damaliscus-pygargus-pygarus-de-hoop-nature-reserve-western-59178463.html?imageid=04F0A152-6CA3-4A65-9067-0364F1A5F09E&p=22059&pn=4&searchId=dca6a568865628209af3d56514ac1f36&searchtype=0

https://www.alamy.com/stock-photo-a-portrait-of-a-bontebok-antelope-in-south-africa-47742290.html?imageid=53CB260B-D3BB-4DD7-B43C-33C570D2CC36&p=158473&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0

https://www.alamy.com/bontebok-damaliscus-pygargus-in-game-park-in-south-africa-looking-over-its-shoulder-image245661564.html

https://www.dreamstime.com/bontebok-damaliscus-pygargus-image129038241

https://www.inaturalist.org/observations/51830740

FACIAL BLEEZE

The conspicuously pale patch on the rostrum of adults of Damaliscus pygargus (https://www.inaturalist.org/taxa/42275-Damaliscus-pygargus) constitutes what is probably the clearest example of a facial bleeze, in any mammal.

In the bontebok, this patch is pure white, contrasting with the dark ground-colour of the face and neck.

https://www.alamy.com/stock-photo-bontebok-blesbok-damaliscus-dorcas-standing-south-africa-47895393.html?imageid=A30EE114-7C91-437B-A4EE-F0E2062F42F1&p=33610&pn=6&searchId=ab384b9287a9a62b3e65ec702d7129d5&searchtype=0

https://www.alamy.com/stock-photo-bontebok-damaliscus-dorcas-at-bontebok-national-park-in-south-africa-38098213.html?imageid=2F8F0D32-30E5-4683-816A-5422AC0E0766&p=60598&pn=2&searchId=595b2aef109e6e3945fa2d85a0f44eb0&searchtype=0

https://www.alamy.com/stock-photo-bontebok-antelope-121112217.html?imageid=C030CB48-025D-450C-9009-14F6598A42A7&p=353301&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0

https://www.gettyimages.com.au/detail/photo/bontebok-damaliscus-dorcas-at-bontebok-national-royalty-free-image/523049311?phrase=bontebok&adppopup=true

https://www.alamy.com/stock-photo-a-pair-of-bontebok-antelopes-damaliscus-pygargus-dorcas-south-africa-85437994.html?imageid=8C3973B1-D533-4CA3-B604-463AAB155B2F&p=70019&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0

There is minimal variation in the facial bleeze, between the sexes, and among individuals. However, a few individuals show slight expansion at the base of the horns (https://www.alamy.com/stock-photo-blesbok-or-bontebok-damaliscus-dorcas-dorcas-syn-damaliscus-pygargus-78567725.html?imageid=967A4632-A630-4F22-84B5-7F50172963C0&p=183822&pn=2&searchId=dff47d9894fdcd82529cde91c8758091&searchtype=0).

Comparison with blesbok (https://www.inaturalist.org/journal/milewski/75748-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi-part-1-adults#):

The pale rostral patch on the face seems proportionately slightly smaller in the bontebok than in the blesbok, owing to what I perceive to be a difference in the size of the head.

Furthermore, in the bontebok the pale on the face tends not to expand with age, as it does in the blesbok (https://www.shutterstock.com/it/image-photo/blesbok-antelope-damaliscus-pygargus-standing-grass-1329980789 and https://www.inaturalist.org/journal/milewski/75871-a-previously-overlooked-expansion-of-the-bles-in-the-blesbok-signifying-full-maturity-beyond-adulthood#).

However, the facial bleeze is as well-developed in the bontebok as in the blesbok, because it seems exempt from the glandular staining seen in males of the blesbok (https://www.alamy.com/a-blesbok-antelope-damaliscus-pygargus-south-africa-image66899227.html?imageid=AA000BC4-7506-4457-96A0-B91FB81FCF46&p=70019&pn=1&searchId=a83f931787d9571cb0a25aca9f82d745&searchtype=0 and https://www.alamy.com/stock-photo-portrait-of-a-blesbok-antelope-damaliscus-pygargus-south-africa-59076858.html?imageid=9FB1F37F-B684-4FE4-A0A4-9A9AC4C55B63&p=70019&pn=1&searchId=a83f931787d9571cb0a25aca9f82d745&searchtype=0).

LATERAL BLEEZE

The lateral bleeze of the bontebok is, proportionately, one of the largest bleezes seen in any ungulate. It extends from the withers and the back to the ventral edge of the thorax and the belly. It also Includes the posterior surface of the upper foreleg, and the anterior surface of the hindleg just below the knee (https://www.inaturalist.org/observations/3985830 and https://www.inaturalist.org/observations/38720040).

The pattern is one of horizontal banding on a broad design, in which the upper and lower panels are pale, with the flanks forming a dark median panel.

However, an important qualification is that the upper panel appears pale partly owing to sheen. Its conspicuousness thus depends on illumination.

https://www.dreamstime.com/stock-photo-bontebok-field-looking-perfect-medium-sized-generally-dark-brown-antelope-prominent-wide-white-image77512668

https://www.agefotostock.com/age/en/details-photo/bontebok-damaliscus-dorcas-dorcas-de-hoop-reserve-south-africa-africa/RHA-743-243/1

https://www.agefotostock.com/age/en/details-photo/bontebok-damaliscus-dorcas-dorcas-bovidae-antelope-mammal-animal-cape-of-good-hope-national-park-south-africa-africa/H44-10978980/1

https://www.alamy.com/stock-photo-bontebok-damaliscus-pygargus-pygarus-at-the-base-of-the-langeberg-59175692.html?imageid=FE1F6904-9478-4A53-8A24-5E8D481C7E90&p=22059&pn=3&searchId=6d8a7f95c3b92935b5e8c1d5d07d00ff&searchtype=0

https://www.alamy.com/bontebok-in-the-bontebok-national-park-swellendam-western-cape-south-africa-image342638387.html?imageid=5C55BBE5-4514-4B34-AEDA-ACC05175FD68&p=22337&pn=3&searchId=6d8a7f95c3b92935b5e8c1d5d07d00ff&searchtype=0

https://www.inaturalist.org/observations/113481398

https://www.inaturalist.org/observations/115575412

https://www.inaturalist.org/observations/80586175

https://www.alamy.com/stock-photo-bontebok-antelope-114770771.html?imageid=0A5EB348-1301-4DC3-B4AD-F99E5785ACEA&p=353301&pn=4&searchId=29c543d132619cf1217ce0a23a3945c6&searchtype=0

https://www.gettyimages.com.au/detail/photo/bonteboks-grazing-royalty-free-image/541049632?phrase=blesbok&adppopup=true

The design of the lateral bleeze of the bontebok is such that in bright sunlight at midday, when the ventral white is inconspicuous owing to shading, the dorsal sheen is 'switched on' owing to sheen (https://www.inaturalist.org/observations/27337501 and https://www.inaturalist.org/observations/27289820).

Comparison with blesbok:

A categorical difference is that, unlike the bontebok, the blesbok lacks a lateral bleeze.

The pelage of the flanks is not necessarily any paler in the blesbok than in the bontebok. However, the differences are that, in the blesbok,

  • the dorsal sheen is poorly-developed,
  • the pale ventral pelage is restricted, and reduced to a combination of countershading and an abdominal flag, and
  • the white anterior edge of the hindleg, just below the knee, is narrower than in the bontebok.

Furthermore,

  • the abdominal flag of the blesbok (https://www.inaturalist.org/observations/130975314) does not occur in the bontebok, having been subsumed within a broader white, ventral panel, and
  • the ulnar flag of the blesbok does not occur in the bontebok, the dark/pale contrast on the posterior surface of the upper foreleg - although just as clear - functioning as an anterior extension of the ventral white of the thorax (and thus being better-regarded as part of the lateral bleeze) in the bontebok.

ISCHIOPYGAL BLEEZE

The ischiopygal bleeze of the bontebok is about as large as the facial bleeze, but located at the opposite pole of the figure (https://www.alamy.com/stock-photo-a-pair-of-bontebok-antelopes-damaliscus-pygargus-dorcas-south-africa-85437994.html?imageid=8C3973B1-D533-4CA3-B604-463AAB155B2F&p=70019&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0 and https://www.dreamstime.com/stock-photo-bontebok-antelopes-pair-damaliscus-pygargus-dorcas-south-africa-image56821286).

The pale posterior feature of the bontebok

  • extends from the rump to the tail-stalk and the buttocks,
  • is largely white, and
  • contrasts with the dark pelage around it.

https://www.inaturalist.org/observations/80650367

https://www.inaturalist.org/observations/57714646

https://www.alamy.com/stock-photo-a-bontebok-damaliscus-pygargus-in-the-bontebok-national-park-near-173731691.html?imageid=75A1E59F-9E57-44B2-8852-46B50B30641E&p=77702&pn=6&searchId=d7a105eea18d32dc6155ddf3de390174&searchtype=0

https://www.inaturalist.org/observations/53977868

Comparison with blesbok:

The ischiopygal flag of the blesbok bears the same relationship to the ischiopygal bleeze of the bontebok as the abdominal flag of the blesbok (https://www.alamy.com/blesbok-in-savannah-south-africa-image151809725.html?imageid=3B900166-AC81-4937-96B6-1CA462655F62&p=703420&pn=10&searchId=26e0b007d6f642f3bb26a9cc6900a5cf&searchtype=0) bears to the white ventral panel of the lateral bleeze of the bontebok.

Furthermore, the ischiopygal flag of the blesbok depends mainly on sheen effects, whereas the ischiopygal bleeze of the bontebok depends mainly on the depigmentation of the pelage.

PEDAL FLAG

The lower legs of adults of the bontebok are largely white, making them conspicuous in locomotion.

https://www.inaturalist.org/observations/127885416

https://www.dreamstime.com/stock-photo-bontebok-antelope-running-velt-image65832109

https://www.alamy.com/bontebok-are-the-colourful-bok-of-south-africa-image228097057.html?imageid=7AAA4F55-17D1-423B-BF91-57470077439F&p=641396&pn=1&searchId=25869b8bb63848eab5bc67f94e53a679&searchtype=0

https://www.alamy.com/stock-photo-bontebok-antelope-17066360.html?imageid=AFA96455-2E25-41C8-91B0-1B7B94A1EA3C&p=4877&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0

https://www.alamy.com/stock-photo-bontebok-antelope-17066531.html?imageid=87C5DBB8-BEBE-41B5-A483-7EF7427CDD10&p=4877&pn=3&searchId=8e369419b3a055a70321251ed7501637&searchtype=0

Comparison with blesbok:

Both the bontebok and the blesbok possess a pedal flag. However, this feature is better-developed in the bontebok, in which

  • the white pelage is more extensive, particularly on the outer surfaces of the lower legs, and
  • there is less individual variation.

LACK OF AURICULAR FLAG

In the bontebok, there is a considerable sheen on the short, sparse pelage on the posterior surface of the ear pinnae. In some.views this produces a noticeably pale aspect to the back-of-ear.

However, after perusing hundreds of photos, I have not found this effect to be strong or consistent enough to qualify as an auricular flag. It is better-regarded as an incipient/residual version of the pattern in the blesbok (see below).

https://www.agefotostock.com/age/en/details-photo/bontebok-antelope/ESY-001254401/1

https://www.alamy.com/bontebok-antelope-damaliscus-pygargus-dorcas-south-africa-image156518411.html?imageid=FCBE4CA1-DBF7-4706-9D07-20EC04F83E25&p=476215&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0

https://www.inaturalist.org/observations/84604329#data_quality_assessment

https://www.alamy.com/stock-photo-bontebok-antelope-bontebok-national-park-swellendam-overberg-western-139221333.html?imageid=C6DAAADA-77BC-4140-AC0F-6ACCCDFABC9D&p=10587&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0

https://www.alamy.com/stock-photo-at-the-peaceful-and-quiet-bontebok-south-african-park-two-antelopes-32166159.html?imageid=143BD930-B2D0-433C-A84D-753F5F9CE194&p=94763&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0

https://www.inaturalist.org/observations/115550547

https://www.alamy.com/bontebok-walking-image647406.html?imageid=FF50FFAE-284D-4D2A-B72E-56FEB151968F&p=4877&pn=4&searchId=29c543d132619cf1217ce0a23a3945c6&searchtype=0

Comparison with blesbok:

The ear pinnae seem identical in size and pigmentation in the bontebok and the blesbok.

However, perusal of hundreds of photos shows that the sheeny quality of the posterior surface is better-developed in the blesbok (https://www.agefotostock.com/age/en/details-photo/blesboks-damaliscus-pygargus-phillipsi-two-adults-standing-in-open-grassland-alert-mountain-zebra-national-park-eastern-cape-south-africa-africa/ZI6-3207754/1 and https://www.agefotostock.com/age/en/details-photo/bontebok-south-africa/FHR-88889-04144-075/1) than in the bontebok.

This, together with the distraction presented by the relatively well-developed sheen on the withers and back, disqualifies the bontebok, in my view, for an auricular flag (https://www.inaturalist.org/journal/milewski/75905-unlike-the-blesbok-the-bontebok-damaliscus-pygargus-pygargus-lacks-an-auricular-flag#).

The lack of an auricular flag in the bontebok is significant evolutionarily. This is because all of the postcranial pale features are better-developed in the bontebok than in the blesbok.

LACK OF CAUDAL FLAG

Please see https://www.inaturalist.org/journal/milewski/79845-in-the-adaptive-colouration-of-genus-damaliscus-is-there-a-caudal-flag#.

DISCUSSION

The colouration of adults of the bontebok is configured in such a way that the figure is conspicuous, regardless of whether

to be continued in https://www.inaturalist.org/journal/milewski/76336-adaptive-colouration-in-the-bontebok-damaliscus-pygargus-pygargus-part-2-infants-juveniles-and-adolescents#...

For an index to my many Posts about the genus Damaliscus, please see https://www.inaturalist.org/journal/milewski/78238-an-index-to-my-posts-on-genus-damaliscus#.

Publicado el marzo 11, 2023 01:51 MAÑANA por milewski milewski | 20 comentarios | Deja un comentario

13 de marzo de 2023

Which ruminant is born with the most conspicuous facial pattern of colouration? part 1: hippotragin and alcelaphin bovids

@tandala @simontonge @paradoxornithidae @tonyrebelo @jeremygilmore @oviscanadensis_connerties @davidbygott @dejong @michalsloviak @christiaan_viljoen @capracornelius @gigilaidler @maxallen

Various ruminants have bold facial markings in both sexes, helping to make the animals adaptively conspicuous.

An example is https://www.sa-venues.com/wildlife/wildlife_roan_antelope.php.

However, in most ruminants, infants hide for a period (https://www.jstor.org/stable/3061529). This makes it adaptive for the colouration to be inconspicuous at birth.

In this Post, I examine four species of bovids with boldly-marked faces, and I illustrate the colouration in infancy, relative to that in adulthood.

These are

  • two hippotragins, in which infants hide, and
  • two alcelaphins, in which infants accompany their mothers continually right from the start.

ORYX GAZELLA (https://www.inaturalist.org/taxa/42308-Oryx-gazella)

In this species of hippotragin bovid, adults possess a facial bleeze.

At birth, the facial pattern is not plain. However, it is so nebulous that it is certainly inconspicuous (https://upload.wikimedia.org/wikipedia/commons/0/05/Oryx_gazella_3_-_Gemsbok_cub.JPG).

As infants grow, the facial pattern, like the horns, develops precocially.

https://www.mindenpictures.com/stock-photo-gemsbok-oryx-gazella-female-with-two-calves-namibrand-reserve-namib-naturephotography-image90799302.html

https://www.zoochat.com/community/media/gemsbok-calf-whipsnade-04-jul-2014.262375/

https://www.alamy.com/gemsbok-oryx-gazella-calf-image4734981.html

https://www.alamy.com/gemsbok-oryx-gazella-calf-image4734984.html

HIPPOTRAGUS EQUINUS (https://www.inaturalist.org/taxa/42332-Hippotragus-equinus)

This hippotragin bovid probably qualifies for a facial bleeze in adults (https://www.inaturalist.org/observations/138018015).

The relationship of infants to adults is similar to that in Oryx gazella.

However, the pattern is so precocial that an argument can be made for at least a facial flag in infants. If so, H. equinus may exemplify the presence at birth of a facial flag, in ruminants.

https://www.agefotostock.com/age/en/details-photo/roan-antelope-hippotragus-equinus-calf-standing-in-dry-woodland-fatalah-reserve-senegal-january/FHR-10028-00039-849

https://es.123rf.com/photo_27725369_roan-antelope-hippotragus-equinus-calf.html

https://www.zoochat.com/community/media/roan-antelope-calf.55666/

https://www.zoochat.com/community/media/roan-antelope-calf.145764/

https://www.inaturalist.org/observations/33354786

DAMALISCUS PYGARGUS (https://www.inaturalist.org/taxa/42275-Damaliscus-pygargus)

This species of alcelaphin bovid certainly qualifies for a facial bleeze in adults.

As in the hippotragins shown above, infants are born with a trace of the facial pattern of adults. However, the relative placement of dark/pale is puzzlingly inverted (see https://www.inaturalist.org/journal/milewski/76336-adaptive-colouration-in-the-bontebok-damaliscus-pygargus-pygargus-part-2-infants-juveniles-and-adolescents# and https://www.inaturalist.org/journal/milewski/75995-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi-part-2-infants-juveniles-and-adolescents#).

https://www.zooborns.com/zooborns/2012/04/meet-blossom-the-blesbok-calf-born-at-belfast-zoo.html

https://www.dreamstime.com/stock-photos-blesbok-antelope-calf-standing-protectively-next-to-s-baby-image36296983

CONNOCHAETES ALBOJUBATUS (https://www.inaturalist.org/observations?taxon_id=525438)

Unlike the three species shown above, the facial colouration of Connochaetes albojubatus is ambivalent in its boldness. However, I include it here because it is the form of wildebeest with the most conspicuous facial colouration.

In the case of wildebeests, the patterns tend to be obfuscated by

  • the confusing complex of species/subspecies, in which various aspects/features of colouration vary in emphasis rather than presence/absence,
  • sheen/antisheen and other effects of illumination, and
  • individual variation.

However, in adults of C. albojubatus, the cheeks tend to be clearer and paler than in other forms of wildebeest, and equally sheeny. This means that C. albojubatus is the wildebeest most likely to qualify for a facial flag.

What is noteworthy is that the facial pattern is also more preocial in C. albojubatus (https://inaturalist.ca/observations/110949669) than in other wildebeests, with the possible exception of another form with a pale beard, viz. Connochaetes mearnsi.

Adults:

The facial pattern in adults of C. albojubatus is, owing to individual variation and the effects of illumination, not consistent enough to qualify for a bleeze. Its maximum expression is seen in https://www.dreamstime.com/stock-photo-young-male-antelope-wildebeest-standing-marshy-lowland-sunn-sunny-afternoon-image89889139.

This pattern - which does qualify as a facial flag - consists of

  • a consistently black rostrum,
  • a pale beard, located close enough to the dark muzzle to provide pale/dark contrast, and
  • cheeks that are usually pale, sheeny, and free of brindling.

https://www.alamy.com/single-wildebeest-in-amboseli-national-park-image362840009.html

https://www.alamy.com/eastern-white-bearded-wildebeest-connochaetes-taurinus-albojubatus-also-brindled-gnu-antelope-in-eastern-and-southern-africa-belongs-to-bovidae-wi-image446124408.html

https://www.alamy.com/stock-photo-eastern-white-bearded-wildebeest-connochaetes-taurinus-albojubatus-57729409.html

https://www.dreamstime.com/blue-wildebeest-wander-grasslands-tsavo-east-park-kenay-image208617369

https://www.alamy.com/blue-wildebeest-connochaetes-taurinus-males-fighting-amboseli-n-p-image443376.html

https://www.dreamstime.com/wildebeest-gnu-portrait-standing-savannah-africa-image155054207

https://inaturalist.ca/observations/5784993

https://www.alamy.com/single-blue-wildebeest-white-bearded-wildebeest-or-brindled-gnu-connochaetes-taurinus-running-across-grassland-of-the-african-savannah-kenya-image240812175.html

https://www.dreamstime.com/wildebeest-gnu-portrait-standing-savannah-africa-image155054207

https://inaturalist.ca/observations/102105372

https://www.dreamstime.com/stock-photos-three-wildebeest-run-image16846173

https://www.dreamstime.com/stock-photo-wildebeest-blue-gnu-connochaetes-taurinus-amboseli-kenya-image67014218

https://www.dreamstime.com/closeup-wildebeest-browsing-closeup-wildebeest-scientific-name-connochaetes-taurinus-nyumbu-swaheli-image-taken-image108980595

https://www.dreamstime.com/royalty-free-stock-photos-wildebeest-connochaetes-taurinus-single-mammal-ground-tanzania-image35926688

https://www.dreamstime.com/royalty-free-stock-photos-wildebeest-image7626258

https://www.alamy.com/eastern-white-bearded-wildebeest-connochaetes-taurinus-albojubatus-also-brindled-gnu-antelope-in-eastern-and-southern-africa-belongs-to-bovidae-wi-image446125271.html

https://zooinstitutes.com/animals/eastern-white-bearded-wildebeest-almaty-zoo-26267.html

https://inaturalist.ca/observations/19542826

Infants:

There are too few photos available to assess individual variation. However, the black rostrum tends to be fully expressed at birth.

The cheeks of infants are not as obviously pale as in most adults, and the pale beard (although precocial) is inconspicuous at birth.

However, a previously overlooked aspect is that, unlike adults, the blackish of the face extends ventral to the eyes (https://www.agefotostock.com/age/en/details-photo/wildebeest-calf-in-plains-amboseli-national-park-kenya/AAM-AAES71424). The facial insignia are thus, in a limited sense, better-developed in infants than in adults, making wildebeests unusual among ruminants.

It is noteworthy that Damaliscus pygargus, another alcelaphin, also has a distinction between infants and adults in the colouration of the orbits. The difference is that, in infants of D. pygargus, the orbits are noticeably pale, not noticeably dark (https://www.zooborns.com/zooborns/antelope/).

https://www.dreamstime.com/stock-photo-newborn-wildebeest-amboseli-park-kenya-mother-baby-image76472324

https://www.flickr.com/photos/sdzooglobal/9270596187

Scroll in https://movementoflife.si.edu/species/wildebeest/

https://www.gettyimages.co.uk/detail/news-photo/boston-ma-a-baby-wildebeest-born-in-the-past-week-on-news-photo/1371566822?adppopup=true

https://www.gettyimages.co.uk/detail/news-photo/boston-ma-a-baby-wildebeest-born-in-the-past-week-on-news-photo/1371566810?adppopup=true

https://www.dreamstime.com/stock-photo-newborn-wildebeest-amboseli-park-kenya-mother-baby-rest-herd-background-image76472453

Scroll in https://www.zoonewengland.org/franklin-park-zoo/our-animals/mammals/hoofed/white-bearded-wildebeest/

https://inaturalist.ca/observations/106811995

https://www.jhpostcards.com/products/white-bearded-wildebeest-riga-zoo-animals-1980-latvia-ussr-unused

Juveniles:

The facial pattern in juveniles of C. albojubatus is as conspicuous as that in adults (https://www.dreamstime.com/stock-photo-big-wildebeest-migration-african-safari-amboseli-national-park-kenia-image84361100).

As growth proceeds, the pelage below the eye loses its black pigmentation (https://inaturalist.ca/observations/6812082).

https://www.alamy.com/stock-photo-part-of-a-herd-of-blue-wildebeest-connochaetes-taurinus-grazing-126164867.html

https://www.alamy.com/herd-of-common-wildebeests-walking-in-dry-grassland-on-summer-day-in-amboseli-national-park-kenya-image502860670.html

https://www.alamy.com/blue-wildebeest-connochaetes-taurinus-amboseli-national-park-kenya-image62676645.html

https://www.alamy.com/eastern-white-bearded-wildebeest-connochaetes-taurinus-albojubatus-also-brindled-gnu-antelope-in-eastern-and-southern-africa-belongs-to-bovidae-wi-image446124965.html

https://www.alamy.com/eastern-white-bearded-wildebeest-connochaetes-taurinus-albojubatus-also-brindled-gnu-antelope-in-eastern-and-southern-africa-belongs-to-bovidae-wi-image446125038.html

https://www.alamy.com/wildebeest-in-the-national-park-tsavo-east-tsavo-west-and-amboseli-in-kenya-image483241293.html?imageid=FE32865D-C28D-4A48-A37B-54D64A5294CF&p=774865&pn=1&searchId=1ded7a829c6fd29f9a553cf0e1e2072e&searchtype=0

DISCUSSION

I know of no ruminant that is born with a facial bleeze.

A facial flag at birth seems plausible in Hippotragus equinus. This would be consistent with

Since infants of H. equinus hide initially, it is unknown how the precociality of the facial pattern is adaptive. Even in adults, the adaptive value of bold facial colouration in hippotragins remains poorly understood.

What is more complex, and even more intriguing, is the ontogeny of the facial pattern in certain alcelaphins.

The facial pattern in infants of wildebeests ranges from inconspicuous in Connochaetes gnou (https://www.zooborns.com/zooborns/wildebeest/ and https://www.irishnews.com/magazine/daily/2019/08/27/news/rare-baby-wildebeest-born-at-newquay-zoo-1696156/ and scroll to fifth photo in https://africafreak.com/black-wildebeest) to conspicuous in C. albojubatus.

The remaining forms are intermediate, with Connochaetes mearnsi and Connochaetes taurinus mattosi (https://www.dreamstime.com/stock-photo-blue-wildebeest-side-view-mosi-oa-tunya-nation-park-zambia-africa-image61435936) apparently exceeding Connochaetes taurinus taurinus, C. t. cooksoni, and C. t. johnstoni.

For infants of wildebeests to have conspicuous colouration seems consistent with extreme adaptation for gregariousness in open environments, and extreme precociality at birth.

However, it remains unexplained why wildebeests vary in this respect.

It remains possible that C. mearnsi (see first comment below) exceeds C. albojubatus in the consistent boldness of the facial pattern in infants. This depends on further photographic evidence.

Given that, in adults, the facial pattern in C. mearnsi is less conspicuous than that in C. albojubatus, this might make C. mearnsi unique among ruminants, in having a facial pattern more conspicuous at birth than in adulthood.

In this context, I remind readers that infants of wildebeests also possess a pedal flag (https://www.dreamstime.com/stock-photo-blue-wildebeest-connochaetes-taurinus-young-calf-playing-rain-kruger-national-park-south-africa-image60301989), absent in adults.

Publicado el marzo 13, 2023 09:23 TARDE por milewski milewski | 28 comentarios | Deja un comentario

14 de marzo de 2023

Which ruminant is born with the most conspicuous facial pattern of colouration? part 2: Rupicapra

https://www.shutterstock.com/image-photo/chamois-baby-animal-photo-408681031

https://www.alamy.com/stock-photo-isard-pyrenean-chamois-rupicapra-rupicapra-pyrenaica-juvenile-photographed-19124206.html?imageid=7E02B991-C239-4502-A4D9-88B5CA40678B&p=13619&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/a-cute-baby-chamois-watchs-whats-going-on-in-his-back-image234753084.html?imageid=9A56DFE1-F566-4576-BA6D-C919479A0DD1&p=688490&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/stock-photo-alpine-chamois-rupicapra-rupicapra-rupicapra-wildlife-animal-124419805.html?imageid=3453966A-22F5-4EBC-9C7E-AA657C08CBAF&p=227690&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/chamois-rupicapra-rupicapra-mother-and-young-standing-in-snow-alpes-italy-image239496480.html?imageid=D7347C62-D046-4FA2-A3FD-395EB8847140&p=295065&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/stock-photo-baby-chamois-walking-alone-on-the-mountain-132918192.html?imageid=EB12E758-EC11-4CD2-909D-C913F609E187&p=315952&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/chamois-gaemse-rupicapra-rupicapra-cute-fawn-young-baby-animal-standing-in-a-flowering-alpine-meadow-watching-for-its-parents-europe-image333942704.html?imageid=C4944BA3-64EB-454E-9DEA-6EDE8475CC2A&p=268352&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/stock-photo-chamois-rupicapra-rupicapra-fawn-running-down-a-grassy-acclivity-alps-47870222.html?imageid=D33203BF-CA3B-4DC1-9170-2890325D08DB&p=57875&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/stock-photo-baby-chamois-in-the-mercantour-national-park-france-alpes-maritimes-21392636.html?imageid=753BE8D7-B252-4972-9069-8D36A0048171&p=17887&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/close-up-of-baby-chamois-on-land-image265013737.html?imageid=43821891-4931-4C65-920D-4503C6BBAAD0&p=857264&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/stock-photo-chamois-rupicapra-rupicapra-fawn-standing-amongst-pine-switzerland-47936822.html?imageid=92C97D23-DCC2-48DD-88D3-1A4FF3976531&p=34210&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/chamois-fawn-image485028099.html?imageid=3305DD28-607D-4C77-B855-A5E8C2D7E268&p=1950458&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/stock-photo-baby-chamois-in-nature-126686414.html?imageid=5AAF8083-2FB8-47FB-877B-764DAB2A92BE&p=163514&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/young-chamois-rupicapra-rupicapra-portrait-alps-france-image425594295.html?imageid=9844F3FF-32A3-4AD2-9097-E852636FA568&p=1286366&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/stock-photo-isard-pyrenean-chamois-rupicapra-rupicapra-pyrenaica-mother-and-baby-19124207.html?imageid=8F91496C-1BA6-400F-91F9-41F25A60927C&p=13619&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/chamois-chamois-goat-with-fawn-standing-in-rocky-terrain-tyrol-austria-image414951530.html?imageid=F04A7870-2BA3-49FC-9117-BFAD9A7E1C00&p=839594&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/stock-photo-chamois-rupicapra-rupicapra-female-with-young-grimsel-bern-switzerland-26563634.html?imageid=6C37AAF3-FA4E-4F5C-B4C1-665BC4CA41AF&p=62076&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/chamois-or-goat-fawn-standing-in-rocky-terrain-tyrol-austria-image414951536.html?imageid=8B3D8F38-955F-458F-A16E-1E14F5CA5A60&p=839594&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

https://www.alamy.com/two-one-year-old-chamois-in-autumn-in-karwendel-mountains-image469119866.html?imageid=D909EE9B-2BC6-422E-A4C1-8C39710E84DA&p=469663&pn=1&searchId=d5e403e46e3e5a7163d99f3864dad793&searchtype=0

Publicado el marzo 14, 2023 04:15 TARDE por milewski milewski | 0 comentarios | Deja un comentario

15 de marzo de 2023

Adaptive colouration in the bontebok (Damaliscus pygargus pygargus), part 2: infants, juveniles, and adolescents

...continued from https://www.inaturalist.org/journal/milewski/76311-adaptive-colouration-in-the-bontebok-damaliscus-pygargus-pygargus-part-1-adults#

The bontebok is well-known for its extreme colouration. However, what is not generally appreciated is how complex the facial colouration is, as it develops from birth to adulthood.

This complexity has never, as far as I know, been described, let alone explained.

At birth, the colouration of the bontebok is fairly plain (https://www.alamy.com/bontebok-damaliscus-pygargus-dorcas-three-ewes-with-their-calves-dehoop-nature-reserve-western-cape-south-africa-september-image262940011.html?imageid=37BEF09A-E8CD-4363-BA0C-D7A889A5A0DE&p=215617&pn=4&searchId=dca6a568865628209af3d56514ac1f36&searchtype=0).

This is puzzling, given that infants do not hide in this species, instead accompanying their mothers from the start.

However, the puzzle of plain colouration in infancy is eclipsed by a greater puzzle as the animal grows into the juvenile stage.

This is because the facial pattern goes through a series of changes that seem superfluous to the relatively simple conversion of the fawn-coloured rostrum of infants to the white rostrum of adults.

It is almost as if Nature has used the juvenile face of the bontebok as a canvas, on which to paint - merely for their own sake - a series of organised designs, before erasing them (https://www.shutterstock.com/it/image-photo/bontebok-antelope-calf-national-park-south-124626181 and https://www.shutterstock.com/it/image-photo/young-bontebok-waiting-cross-road-national-1012848241 and https://pixels.com/featured/bontebok-tony-camachoscience-photo-library.html).

INFANTS

At birth, the bontebok is fawn-coloured with countershading, plus

The pattern on the head may seem negligible at first glance. However, on closer examination it poses a fundamental evolutionary puzzle.

I describe this pattern as follows:

The facial pattern of infants of the bontebok is inconspicuous, because

  • the pale feature on and near the orbits is small-scale, and
  • there is no dark pelage, anywhere on the head.

However, what is remarkable is that this pattern is not merely a nebulous or incipient version of the adult colouration, as is the case in hippotragin bovids (https://www.inaturalist.org/journal/milewski/76424-which-ruminant-is-born-with-the-most-conspicuous-facial-pattern-of-colouration-part-1-hippotragin-and-alcelaphin-bovids#).

Instead, the pattern is different from that in adults. It is as if infants and adults are different species.

To be precise, the only parts of the head of infants that already show adult colouration are:

  • a small whitish triangle just above the rhinarium, and
  • the whitish hairs on the anterior surface of the ear pinnae.

The following show infants close-up:

https://www.inaturalist.org/observations/63400386

https://www.inaturalist.org/observations/115686906

https://www.inaturalist.org/observations/99722303

The following show infants with their mothers:

https://www.dreamstime.com/royalty-free-stock-image-mother-calf-blesbok-antelope-image21744916

https://www.dreamstime.com/stock-photo-bontebok-calf-mother-her-foraging-fynbos-southern-africa-image92719587

https://pixels.com/featured/bontebok-mother-and-calf-peter-chadwickscience-photo-library.html

https://www.dreamstime.com/young-bontebok-adult-fynbos-fawn-coloured-young-bontebok-fynbos-veld-adult-near-cape-point-western-cape-image268185782

https://www.alamy.com/bontebok-damaliscus-pygragus-dorcas-ewe-with-one-day-old-calf-dehoop-nature-reserve-western-cape-south-africa-september-image262940010.html

https://www.alamy.com/stock-photo-bontebok-with-calf-damaliscus-pygargus-pygarus-de-hoop-nature-reserve-59178437.html?imageid=03857B0D-5BE3-4A6C-B22B-16A28380CD06&p=22059&pn=5&searchId=a4908a5258dd3ea4c025bcd202432b49&searchtype=0

https://www.alamy.com/bontebok-damaliscus-pygargus-pygargus-adult-and-calf-sitting-de-hoop-south-africa-december-image263070029.html?imageid=88C59DAE-1AFE-4E31-9DD7-E9102086EA36&p=215536&pn=1&searchId=25869b8bb63848eab5bc67f94e53a679&searchtype=0.

The infantile pattern of colouration persists to the age of three months. At this stage the horn-tips have appeared, and the body mass exceeds a quarter of maternal body mass:

https://www.dreamstime.com/stock-photo-bontebok-calf-mother-her-foraging-fynbos-southern-africa-image92743101

https://www.alamy.com/bontebok-with-young-image1218482.html?imageid=B2DF1491-9EBB-4DA5-8DC2-552475BDDC6F&p=4877&pn=4&searchId=29c543d132619cf1217ce0a23a3945c6&searchtype=0

https://www.alamy.com/bontebok-with-two-youngsters-image1218481.html?imageid=9C191390-7AA0-43F4-9B4F-5038BD5BE66A&p=4877&pn=5&searchId=78e3c36a9917c21e07efdd82f4c4fbc0&searchtype=0

The following series of photos, of an individual infant (1-2 months old), is one of the clearest expositions on the Web of the infantile colouration of the bontebok. The infantile colouration of the bontebok is not as pale as that of the blesbok, but more clearly shows countershading.

Damaliscus pygargus pygargus:

https://www.shutterstock.com/it/image-photo/baby-bontebok-antelope-calf-looks-curiously-744728989

https://www.shutterstock.com/it/image-photo/cute-baby-bontebok-antelope-calf-looks-744728965

https://www.shutterstock.com/it/image-photo/baby-bontebok-antelope-calf-stays-close-744728971

https://www.shutterstock.com/it/image-photo/cute-baby-bontebok-antelope-calf-scratches-744728980

https://www.shutterstock.com/it/image-photo/cute-baby-bontebok-antelope-calf-scratches-744728986

https://www.shutterstock.com/it/image-photo/baby-bontebok-antelope-calf-looks-see-744728992

https://www.shutterstock.com/it/image-photo/two-cute-baby-bontebok-antelope-calves-744728956

JUVENILES

The following series provides one of the clearest illustrations of juvenile colouration in the bontebok:
https://www.shutterstock.com/it/image-photo/bontebok-damaliscus-pygargus-pygarus-south-africa-560325085 and https://www.shutterstock.com/it/image-photo/bontebok-damaliscus-pygargus-pygarus-south-africa-560325091 and https://www.shutterstock.com/it/image-photo/bontebok-damaliscus-pygargus-pygarus-south-africa-560325112.

At the juvenile stage, the colouration on the neck, body, and legs changes directly towards that of the adult.

However, the colouration of the head goes through convoluted changes.

The first change on the head is a darkening of the rostrum (https://www.alamy.com/m2-304d-yearling-bontebok-head-image6516263.html?imageid=6FB7B5E5-32AD-4555-AD1C-BE8C66B0C857&p=1787&pn=6&searchId=d7a105eea18d32dc6155ddf3de390174&searchtype=0).

The following (https://www.shutterstock.com/it/image-photo/bontebok-antelope-calf-national-park-south-124597081 and https://www.shutterstock.com/it/image-photo/bontebok-antelope-calf-earlymorning-light-125978060 and https://www.shutterstock.com/it/image-photo/bontebok-antelope-calf-de-hoop-nature-126157526 and https://www.shutterstock.com/it/image-photo/bontebok-antelope-mother-calf-national-park-124597057 and https://www.dreamstime.com/bontebok-damaliscus-pygargus-jonge-young-image129038812) show that there is a brief stage at which the darkest part of the juvenile figure (apart from the developing tail-tassel) is a particular panel on the front of the face.

This is closely followed by a darkening of the orbits, and the appearance of a complex, pale streak from the cheek, through the temple, to the crown (third photo in https://www.inaturalist.org/observations/121214288 and https://www.shutterstock.com/it/image-photo/bontebok-damaliscus-pygargus-pygarus-south-africa-560325085 and https://animals.sandiegozoo.org/animals/bontebok).

The following shows the dark/pale differentiation on the cheek (https://www.shutterstock.com/it/image-photo/bontebok-antelope-calf-national-park-south-124626181).

The following shows the maximum extent of pale on and near the temples (https://www.shutterstock.com/it/image-photo/baby-bontebok-looking-right-mediumsized-generally-485672296).

The pale on the temples is among the last signs of the juvenile colouration to disappear (https://www.inaturalist.org/observations/137506000).

The whitish ventral surface of the mandibles remains in the juvenile stage (https://www.shutterstock.com/it/image-photo/young-playful-antelope-1327148681). The following shows the discrete pattern that arises at 0.5-1 year old, only to vanish in adulthood (https://www.dreamstime.com/wild-african-animals-bontebok-one-rarest-antelope-world-beautiful-grassland-etosha-national-park-namibia-image183764936).

The following show juveniles nearly 6 months old:

https://www.gettyimages.com.au/detail/photo/bontebok-damaliscus-dorcas-at-bontebok-national-royalty-free-image/523049313?phrase=bontebok&adppopup=true

https://www.inaturalist.org/observations/10843075

https://www.dreamstime.com/stock-images-bontebok-damaliscus-dorcas-image20906614

https://www.alamy.com/stock-photo-herd-of-bontebok-antelope-with-calf-23274728.html?imageid=B8F63BA8-FA72-44CE-80AC-2EF5979BF4BB&p=71732&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0

https://www.inaturalist.org/observations/104575032

The following show juveniles about one year old, when the dark on the rostrum is being gradually replaced by the white hairs of adulthood:

https://www.alamy.com/bontebok-damaliscus-pygargus-pygargus-bontebok-national-park-swellendam-western-cape-south-africa-calf-walking-in-fynbos-image365041507.html?imageid=53762990-B5AF-4A57-AC9A-3B48F49AF21B&p=824482&pn=1&searchId=e1c83791dbb28b2649d55bb669e0fbda&searchtype=0

https://www.inaturalist.org/observations/155658021

https://pixels.com/featured/bontebok-tony-camachoscience-photo-library.html

https://www.inaturalist.org/observations/16478604

https://www.alamy.com/a-vertical-shot-of-bontebok-standing-on-grassland-in-a-park-image499977486.html?imageid=A3EA59CE-7513-4A04-94CC-492D2B267CD8&p=829514&pn=9&searchId=357b330dca08dc7955106e41cd143444&searchtype=0

https://www.alamy.com/extreme-close-up-of-the-head-and-neck-of-a-wild-beautiful-bontebok-antelope-looking-at-the-camera-in-the-wilderness-of-south-africa-shot-on-safari-image435705572.html?imageid=382F9E4B-C34E-4EDB-BCCA-399C10C04B3A&p=576257&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0

https://www.shutterstock.com/it/image-photo/pair-bontebok-grazing-national-park-south-1454575475

https://www.inaturalist.org/observations/137506000

The following (https://www.inaturalist.org/observations/52622577 and https://www.alamy.com/stock-photo-i-see-you-bontebok-the-bontebok-is-a-medium-sized-generally-dark-brown-119828808.html?imageid=262BD3B2-8140-4150-8B1D-BB20F2C8C369&p=260684&pn=4&searchId=29c543d132619cf1217ce0a23a3945c6&searchtype=0 and https://www.dreamstime.com/young-bontebok-grazing-young-bontebok-grazing-cape-point-national-park-cape-town-south-africa-image245392763 and https://www.dreamstime.com/stock-photo-baby-bontebok-medium-sized-generally-dark-brown-antelope-prominent-wide-white-blaze-its-face-image77372211) show particularly clearly the tardiness of the posterior surface of the upper foreleg, above the carpal, in turning dark.

Throughout the juvenile stage, the ventral surface of the neck retains the countershading that will eventually be lost in adulthood (https://www.inaturalist.org/observations/131702545).

The following, of juveniles more than one year old (https://www.alamy.com/bontebok-female-with-young-de-hoop-nature-reserve-western-cape-south-africa-africa-damaliscus-dorcas-dorcas-image228117439.html?imageid=373F25EB-E0E9-443A-8DD5-4194A60EEA24&p=205512&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0 and https://www.alamy.com/bontebok-female-and-juvenile-de-hoop-national-park-western-cape-south-africa-damaliscus-dorcas-dorcas-image414952533.html?imageid=304942E1-F18D-4D68-AE40-F31399C02086&p=1420153&pn=4&searchId=29c543d132619cf1217ce0a23a3945c6&searchtype=0), show several aspects particularly clearly, viz.

  • the horns are about three-quarters of full length and the body mass is about 60% of maternal body mass,
  • the dark pelage on the figure remains paler than that of adult females,
  • the face remains proportionately shorter than in adults, limiting the prominence of the whitish (which is not yet fully white) on the face, and
  • the dark pelage on the legs remains incomplete.

When the horns reach three-quarters of their full length (https://www.shutterstock.com/it/image-photo/yes-cute-bontebok-mediumsized-generally-dark-484356040 and https://www.shutterstock.com/it/image-photo/baby-bontebok-497894932), the few juvenile features remaining include

  • a trace of countershading on the ventral surface of the neck,
  • incompleteness of the dark above the carpal, and
  • a pale streak on the temple.

ADOLESCENTS

One of the last features to form completely is the dark pelage on the posterior surface of the upper foreleg, just below the white patch on the ulna (https://www.dreamstime.com/stock-photo-bontebok-perfect-pose-medium-sized-generally-dark-brown-antelope-prominent-wide-white-blaze-its-image77512322 and https://www.inaturalist.org/observations/146638259).

As the rostrum rapidly lengthens and the facial colouration approaches completeness, a dark periphery to the pale features on the forehead and rostrum can intensify and linger (https://www.istockphoto.com/photo/bontebok-antelope-gm136712138-18853032?phrase=pics%20of%20a%20blesbok and https://www.alamy.com/stock-photo-portrait-of-an-endangered-bontebok-antelope-damaliscus-pygargus-dorcas-22757989.html?imageid=D0FE2C16-1433-4C7A-9D18-B2AC8938DBEE&p=70019&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0).

The colouration becomes complete before the horns have attained their full length (https://www.dreamstime.com/stock-image-bontebok-antelope-handsome-large-eyes-grass-mouth-image34760281). However, a trace can remain of the last juvenile feature to disappear, namely the pale vertical streak on the temples, even when the horns seem full-length.

DISCUSSION

The complexity of the changes in facial colouration can be contrasted with the simplicity of the changes on the hindquarters (https://www.alamy.com/bontebok-damaliscus-dorcas-adult-and-juvenile-in-a-flower-meadow-south-image8795878.html?imageid=BEFC3720-6ABE-438B-9767-B86189806239&p=33533&pn=11&searchId=909e0db787de943a5f89073993791964&searchtype=0 and https://www.inaturalist.org/observations/47971842).

Unlike the facial bleeze, the ischiopygal bleeze of the bontebok starts to appear at the end of infancy (https://www.inaturalist.org/observations/10980014), and then simply and directly continues to completion within a mere three months.

The ischiopygal bleeze is complete at about six months old (https://www.shutterstock.com/it/image-photo/young-bontebok-grazing-1349950382), when the face is still unrecognisably different from that of adults.

Almost every aspect of the ontogenetic development of colouration in the bontebok is puzzling, from the viewpoint of adaptation and evolution.

The main questions arising from this examination are as follows:

  • how is it adaptive for infants to have cryptic colouration, given that they do not hide (this is particularly puzzling because the plain colouration persists despite the body mass being trebled from birth to three months old)?
  • why does the facial pattern go through such complex, temporary changes from three months to one year old? and
  • how has such disparity arisen between the pygal bleeze and the facial bleeze, with the former developing early and directly, vs the latter being delayed until adolescence, and emerging from an unrecognisably different, transitional pattern?

Also see https://www.inaturalist.org/journal/milewski/75995-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi-part-2-infants-juveniles-and-adolescents#.

For an index to my many Posts about the genus Damaliscus, please see https://www.inaturalist.org/journal/milewski/78238-an-index-to-my-posts-on-genus-damaliscus#.

Publicado el marzo 15, 2023 03:39 MAÑANA por milewski milewski | 32 comentarios | Deja un comentario