...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
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:
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://pixels.com/featured/bontebok-mother-and-calf-peter-chadwickscience-photo-library.html
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:
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.inaturalist.org/observations/10843075
https://www.dreamstime.com/stock-images-bontebok-damaliscus-dorcas-image20906614
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.inaturalist.org/observations/155658021
https://pixels.com/featured/bontebok-tony-camachoscience-photo-library.html
https://www.inaturalist.org/observations/16478604
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.
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
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:
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#.
Comentarios
A particularly good illustration of mother and infant of Damaliscus pygargus pygargus is the second photo in https://www.inaturalist.org/observations/146457679.
The following show the pale feature on the temples, which appears just after infancy and persists into the adolescent stage:
https://www.dreamstime.com/bontebok-damaliscus-pygargus-image129038391
https://www.dreamstime.com/royalty-free-stock-photos-bonteboks-grazing-near-cape-town-bontebok-antelopes-field-desert-scrub-outside-image39309398
https://www.alamy.com/bontebok-national-park-swellendam-western-cape-south-africa-rsa-bontebok-image1235937.html?imageid=9B3C78A9-33EB-4422-9A0B-E1A38A75256D&p=4850&pn=8&searchId=e946195336c488fed5d2b226d587c54a&searchtype=0
https://www.alamy.com/stock-photo-blesbok-damaliscus-dorcas-grazing-mokuti-etosha-lodge-namibia-87936340.html?imageid=C5AC8129-9127-45AA-9BD5-82DB474949E7&p=104079&pn=12&searchId=613ad7e0bd93e5b62ff61eccb1b0294f&searchtype=0
Stotting in both mother and infant of bontebok:
https://www.fox43.com/article/news/nation-world/rare-african-bontebok-antelope-calf-debut-oregon-zoo/507-e071f9fd-cc2d-423e-9e6a-a066fce93502
https://www.gettyimages.com.au/detail/news-photo/bontebok-bovids-kagga-kamma-private-game-reserve-south-news-photo/182129897?phrase=bontebok&adppopup=true
Contains a worthwhile photo of juvenile bontebok:
https://www.africawild-forum.com/viewtopic.php?t=10116
https://www.mindenpictures.com/stock-photo-bontebok-damaliscus-pygargus-dorcas-ewe-with-one-day-old-calf-de-hoop-naturephotography-image90692735.html
Please note the forehead in the following photo of juvenile bontebok, just before adolescence:
https://www.gettyimages.co.uk/detail/photo/bontebok-west-coast-national-park-langebaan-western-royalty-free-image/996178920?adppopup=true
The following contains a worthwhile photo of juvenile bontebok:
https://www.facebook.com/kleinbuisfonteinranch/posts/a-closer-look-at-the-bontebokbontebokdamaliscus-pygargus-dorcasshoulder-height-9/731767046968926/
Shift
https://psnp.info/p4td_/?m=20220913#jp-carousel-15901
Adult females and infants of the bontebok:
https://www.shutterstock.com/it/image-photo/bontebok-antelope-damaliscus-pygargus-adults-calves-2075496853
Adult females and juveniles (4-5 months old) of the bontebok:
https://www.shutterstock.com/it/image-photo/family-group-bontebok-antelopes-damaliscus-pygargus-222934924
Adolescents of the bontebok:
https://www.shutterstock.com/it/image-photo/bontebok-kruger-park-1837292230
Adolescent, 1-2 years old, of the bontebok:
https://www.istockphoto.com/photo/bontebok-antelope-gm497410815-41785806?phrase=pics%20of%20a%20blesbok
The following, of the bontebok, show that juveniles, 1-1.5 years old, have nearly attained the adult colouration. However, the size of the facial bleeze remains limited because the rostrum of the face has yet to lengthen, proportionately:
https://www.shutterstock.com/it/image-photo/bonteboks-resting-de-hoop-nature-reserve-733416349https://www.shutterstock.com/it/image-photo/bontebok-smelling-each-other-mediumsized-generally-485672326
The following individual (https://www.inaturalist.org/observations/151809619) seems unusual in its development of the white in the face, particularly for its age.
The following (https://richardgrantphotography.com/bontebok-national-6th-october/), of an adolescent individual of the bontebok probably 1.5-2 years old, shows the following differences from adults:
a) the horns remain far shorter, and the rostrum of the face somewhat shorter, than in adults,
b) the tail-tassel remains somewhat shorter than in adults,
c) the dark pelage at the crook of the throat, on the chest, and on the upper forelegs and upper hindlegs, remains incomplete,
d) there remains a blackish outline to the pale features on the face, particularly on the forehead, and
e) the pale pelage on the temples has yet to disappear.
https://www.bigstockphoto.com/image-147922667/stock-photo-baby-bontebok-looking-right
The following is one of the clearest photos of infants of the bontebok. This individual is about two months old:
https://www.clarksvilleonline.com/2022/07/04/nashville-zoo-reports-bontebok-calf-makes-debut/
https://twitter.com/FossilRim/status/1198617489233588229/photo/4
https://twitter.com/FossilRim/status/1198617489233588229/photo/3
https://bilderreich.de/1325/fact-sheet-bontebok-damaliscus-pygargus.html
https://www.flickr.com/photos/berniedup/31441973447/in/photostream/
https://www.flickr.com/photos/berniedup/46485971264
https://upload.wikimedia.org/wikipedia/commons/b/b8/Bontebok_with_calf.jpg
https://www.shutterstock.com/it/image-photo/bontebok-calf-cape-point-nature-reserve-1970105050
https://www.shutterstock.com/it/image-photo/bontebok-grassland-looking-towards-camera-131615849
https://www.shutterstock.com/it/image-photo/bontebok-201475892
https://www.shutterstock.com/it/image-photo/family-group-bontebok-antelopes-damaliscus-pygargus-222934924
https://www.inaturalist.org/observations/124207904
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.gettyimages.com.au/detail/news-photo/bunte-bock-damaliscus-dorcas-standing-in-undergrowth-in-the-news-photo/481653583?phrase=blesbok&adppopup=true
The following series shows adult female and infant (less than 2 weeks old) clearly in the bontebok. The colouration on the rump and legs hints at hybridisation with the blesbok, but the history (https://timeline.sdzwa.org/bontebok/) seems to indicate purity of this population in San Diego Zoo. Also see https://zooinstitutes.com/animals/bontebok-3430/.
https://www.flickr.com/photos/helenehoffman/48319703872
https://www.flickr.com/photos/helenehoffman/48319703872/in/photostream/
https://www.flickr.com/photos/helenehoffman/48319000726/in/photostream/
https://www.flickr.com/photos/helenehoffman/48319584401/in/photostream/
https://www.flickr.com/photos/helenehoffman/48319703267/in/photostream/
https://www.flickr.com/photos/helenehoffman/48319701787/in/photostream/
https://www.flickr.com/photos/sdzooglobal/40329604870/in/photostream/
https://www.flickr.com/photos/sdzooglobal/42136359491/in/photostream/
https://www.flickr.com/photos/sdzooglobal/40329604780/in/photostream/
https://zooinstitutes.com/animals/bontebok-san-diego-zoo-25003.html
https://www.alamy.com/san-diego-california-usa-august-20-1013-san-diego-zoo-bontebok-antelope-with-horns-standing-and-look-right-image272256190.html
https://www.dvm360.com/view/oregon-zoo-welcomes-rare-african-bontebok-calf
https://www.upi.com/Odd_News/2023/04/10/bontebok-antelope-born-Oregon-Zoo/8971681155987/
https://www.natureworldnews.com/articles/56226/20230417/rare-antelope-bontebok-calf-born-oregon-zoo-population-reaches-2500.htm
https://www.inaturalist.org/observations/157165876
https://www.inaturalist.org/observations/157615400
https://www.inaturalist.org/observations/158580020
https://www.inaturalist.org/observations/159625944
The following of a juvenile individual (https://www.inaturalist.org/observations/170493639) is the clearest photo that I have found, in illustration of the delayed closure of the pale features on a) the temple, b) the posterior of the upper foreleg, and c) the ventral surface of the mandibles near the mouth.
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