milewski's Journal

Age-determination of the tsessebe, plus labelling by body mass, using photos in iNaturalist

What, exactly, does a given species of ruminant look like at a given age? Can we estimate the body mass of infants and juveniles in photographs, based on objective criteria?

The tsessebe (Damaliscus lunatus lunatus, https://www.inaturalist.org/observations?taxon_id=132770) provides an unusual opportunity, because

its growth and reproduction show a definite relationship to the calendar, and
the subspecies is well-covered by photos in iNaturalist.

Child et al. (1972, https://www.degruyter.com/document/doi/10.1515/mamm.1972.36.3.342/html) found the following mean body masses for the tsessebe:

Mature males 140 kg

Mature females 127 kg

Adult males 3 years old 135 kg

Adult females 3 years old 115 kg

Adolescent males 2 years old 105-110 kg

Adolescent females 2 years old 95 kg

Juvenile males 1 year old 82 kg

Juvenile females 1 year old 68 kg

Juvenile males 6 months old 55 kg

Juvenile females 6 months old 45 kg

Newborns 10-11 kg

What this amounts to is a progression of body mass of 10 kg-50 kg-75 kg-100 kg-125 kg-130 kg, at the ages of 0 years-0.5 years-1 year-2 years-3 years-6 years.

Huntley (https://journals.co.za/doi/pdf/10.10520/AJA03794369_3447) states 'horns became externally visible at five weeks'.

Based on the above information, I have annotated photos of the tsessebe in iNaturalist.

BOTSWANA

According to Child et al. (1972, https://www.degruyter.com/document/doi/10.1515/mamm.1972.36.3.342/html), the tsessebe in northern Botswana breeds extremely seasonally, giving birth in November.

The results are as follows, beginning with the birth-month of November, and categorising observations by subsequent months.

November

The following show infants < 1 month old, with body mass <15 kg:
https://www.inaturalist.org/observations/100694354
https://www.inaturalist.org/observations/66701641
https://www.inaturalist.org/observations/122347068

Late December/early January

The following show infants about 1.5 month old, when the horn-tips have just appeared, and body mass is little more than 20 kg:
https://www.inaturalist.org/observations/146520990
https://www.inaturalist.org/observations/146636730
https://www.inaturalist.org/observations/146528727

February

According to the stated date, the following shows an infant individual about 3 month old. This seems questionable in view of the small size of the horns. However, this individual was possibly born at the end of the birth-season, say in early December, in which case the age might be 2-2.5 months:
https://www.inaturalist.org/observations/147820164

March

The following show juveniles about 4.5 months old, when the horns are easily visible and the ground-colour of the juvenile figure is still noticeably paler than that of adults. Body mass is probably about 40 kg, which is a quarter of maternal body mass:
https://www.inaturalist.org/observations/37787394
https://www.inaturalist.org/observations/10004638

July

The following show juveniles about 8 months old, when the dark markings are not yet fully-developed, particularly on the face. Body mass is probably <60kg, which is about half of maternal body mass:
https://www.inaturalist.org/observations/143915475
https://www.inaturalist.org/observations/57781574
https://www.inaturalist.org/observations/38168446
https://www.inaturalist.org/observations/4131
https://www.inaturalist.org/observations/125828092

August

The following show juveniles about 9 months old:
https://www.inaturalist.org/observations/138887828
https://www.inaturalist.org/observations/41206964
https://www.inaturalist.org/observations/41206958

September

The following show juveniles about 10 months old. Body mass is probably <70 kg:
https://www.inaturalist.org/observations/11383030
https://www.inaturalist.org/observations/33810120
https://www.inaturalist.org/observations/33769054
https://www.inaturalist.org/observations/138261267

October

The following shows juveniles about 11 months old. Body mas is probably >70 kg:
https://www.inaturalist.org/observations/69009855

November

The following shows a juvenile individual about 12 months old. Body mass is about 75 kg:
https://www.inaturalist.org/observations/17087

Late December/early January

The following shows a juvenile individual about 13.5 months old. Body mass is probably <80 kg. The dark markings, particularly on the face, remain incomplete, and seem not to have changed over the previous 6 months:
https://www.inaturalist.org/observations/10639034

March

16 months old
https://www.inaturalist.org/observations/21793037

16.5 months old
https://www.inaturalist.org/observations/10006014

May

18 months old
https://www.inaturalist.org/observations/61938247

June

19 months old
https://www.inaturalist.org/observations/139307973
https://www.inaturalist.org/observations/139301317

November

24 months old
https://www.inaturalist.org/observations/2588518

December

25 months old
https://www.inaturalist.org/observations/15469

KRUGER NATIONAL PARK AND ZIMBABWE

In Kruger National Park (South Africa) and Zimbabwe, the tsessebe gives birth in October.

October

Newborn
https://www.inaturalist.org/observations/32595531
https://www.inaturalist.org/observations/9323974

December

1.5 months old
https://www.inaturalist.org/observations/107290193

2 months old
https://www.inaturalist.org/observations/36703962

February

4 months old
https://www.inaturalist.org/observations/87448750
https://www.inaturalist.org/observations/38602291

March

5 months old
https://www.inaturalist.org/observations/151731918
https://www.inaturalist.org/observations/144870681

April

6 months old
https://www.inaturalist.org/observations/75355938
https://www.inaturalist.org/observations/12119329

June

8 months old
https://www.inaturalist.org/observations/13368268

July

9 months old
https://www.inaturalist.org/observations/99261092
https://www.inaturalist.org/observations/20887477

August

10 months old
https://www.inaturalist.org/observations/107534355

September

11 months old
https://www.inaturalist.org/observations/99518233

October

1 year old
https://www.inaturalist.org/observations/143044598
https://www.inaturalist.org/observations/44272021

November

13 months old
https://www.inaturalist.org/observations/37087281
https://www.inaturalist.org/observations/7733155

December

13.5 months old
https://www.inaturalist.org/observations/107290193

January

15 months old
https://www.inaturalist.org/observations/9412515

February

16 months old
https://www.inaturalist.org/observations/105321502
https://www.inaturalist.org/observations/35886830
https://www.inaturalist.org/observations/34375710

September

23 months old
https://www.inaturalist.org/observations/16954883

November

25 months old
https://www.inaturalist.org/observations/7733155

CAPRIVI STRIP

In the Caprivi Strip of Namibia, the tsessebe gives birth in September.

December

3.5 months old
https://www.inaturalist.org/observations/6899966November

September

1 year old
https://www.inaturalist.org/observations/138408064

November

14 months old
https://www.inaturalist.org/observations/36316646

DISCUSSION

The following photo-pair nicely show the difference between 11 months old and 23 months old:
https://www.inaturalist.org/observations/99518233
https://www.inaturalist.org/observations/16954883

Posted on April 01, 2023 09:19 AM by

milewski | 1 comment | Leave a comment

A concise photo-comparison of adaptive colouration between the tsessebe and the blesbok

@michalsloviak @tonyrebelo @jeremygilmore @ludwig_muller @paradoxornithidae @tandala @oviscanadensis_connerties @simontonge @jwidness

Please see https://www.inaturalist.org/journal/milewski/77112-adaptive-colouration-in-the-tsessebe-damaliscus-lunatus-using-the-related-blesbok-for-reference# and https://www.inaturalist.org/journal/milewski/75748-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi-part-1-adults#

In this summary, I refer to adults only, of the tsessebe (Damaliscus lunatus lunatus, https://www.alamy.com/topi-tsessebi-korrigum-tsessebe-damaliscus-lunatus-in-savanna-south-africa-mokala-national-park-image255402674.html?imageid=7A297C06-C0DB-4C75-83AE-3037C9C12D4E&p=851122&pn=1&searchId=303cfda7336cba6c5732f1db91b12f81&searchtype=0) and the blesbok (Damaliscus pygargus phillipsi, https://www.shutterstock.com/it/image-photo/blesbok-blesbuck-damaliscus-dorcas-phillipsi-497011045).

FACIAL BLEEZE ABSENT IN TSESSEBE BUT PRESENT IN BLESBOK

In the tsessebe, the rostrum is blackish, whereas in the blesbok the rostrum is whitish. Although these tones are both extreme, the effect is far less conspicuous in the tsessebe than in the blesbok, partly because of a lack of dark/pale contrast on the face of the tsessebe.

Tsessebe
https://stock.adobe.com/search/images?k=tsessebe&asset_id=175846122
https://stock.adobe.com/search/images?k=tsessebe&asset_id=145113726
https://stock.adobe.com/search/images?k=tsessebe&asset_id=22528301

Blesbok
https://dewetswild.com/tag/blesbok/#jp-carousel-40689
https://dewetswild.com/2016/06/23/blesbok/
https://www.freeart.com/artwork/art-print/blesbok-antelope_fa13514984.html

PYGAL FLAG PRESENT IN BOTH TSESSEBE AND BLESBOK

In both the tsessebe and the blesbok, the pelage on the upper, inner buttocks is pale, and that of the buttocks and base of tail, more broadly, is sheeny. Dependent on illumination, this can gleam conspicuously when the figure moves, even at a distance.

Blesbok
https://www.flickr.com/photos/gerdavs/30537405800
https://unsplash.com/photos/6QUPjrFJ_cU
https://www.gettyimages.com.au/detail/photo/blesbok-royalty-free-image/1351086134?phrase=blesbok&adppopup=true
https://stock.adobe.com/search/images?k=blesbok&asset_id=357665041

ULNAR FLAG ABSENT IN TSESSEBE BUT PRESENT IN BLESBOK

In both the tsessebe and the blesbok, the pelage on the upper foreleg tends to be dark, with a pale patch on its posterior surface. This potentially complements the pygal flag, in posteriolateral view.

However, only in the blesbok is this conspicuous enough to qualify as a flag.

Tsessebe
https://www.flickr.com/photos/42964440@N08/52226882444
Scroll in https://mattanu.com/wp-content/uploads/2017/11/Kriek-Wildlife-Group-Journal-Kriek-Wildlife-Group-Journal.pdf

ABDOMINAL FLAG ABSENT IN TSESSEBE BUT PRESENT IN BLESBOK

In both the tsessebe and the blesbok, the pelage immediately anterior to the knee tends to be pale. However, in the tsessebe this is not conspicuous enough to qualify as a flag, whereas in the blesbok the pelage in question is whitish, and conspicuous in/at certain illuminations and perspectives.

Tsessebe
https://www.flickr.com/photos/berniedup/50213649897

Blesbok
https://dewetswild.com/2016/06/23/blesbok/#jp-carousel-10761

PEDAL FLAG ABSENT IN TSESSEBE BUT PRESENT IN BLESBOK

In both the tsessebe and the blesbok, the pelage on the lower legs tends to be pale relative to that on the upper legs. This is potentially conspicuous when the animal walks.

However, only in the blesbok is this conspicuousness realised, because the inner surface of the lower foreleg in particular is whitish.

Blesbok
https://www.alamy.com/blesbok-damaliscus-pygargus-phillipsi-adult-walking-in-open-grassland-mountain-zebra-national-park-eastern-cape-south-africa-africa-image229684222.html

AURICULAR FLAG ABSENT IN TSESSEBE BUT PRESENT IN BLESBOK

In both the tsessebe and the blesbok, the posterior surface of the ear pinna has medium tone in terms of its pigmentation. However, in the blesbok the sparse, short pelage on this surface is so sheeny that the back-of-ear appears conspicuously pale according to illumination and perspective. This effect is never seen in the tsessebe.

Blesbok
https://www.dreamstime.com/stock-photo-blesbuck-late-afternoon-field-blesbok-antelope-endemic-to-south-africa-has-distinctive-white-image77761759
https://dewetswild.com/tag/blesbok/#jp-carousel-10763

CAUDAL FLAG ABSENT IN BOTH TSESSEBE AND BLESBOK

The tails of the tsessebe and the blesbok are surprisingly different in structure, considering that they belong to the same genus. The tail of the tsessebe is less conspicuous than that of the blesbok, because the dark tail-tassel is thin. However, neither the tsessebe nor the blesbok possesses a caudal flag, at least in the context of anti-predator displays. This is mainly because the tails are not raised or wagged in alarm or while fleeing.

Tsessebe
https://stock.adobe.com/search/images?k=tsessebe&asset_id=7408032
https://stock.adobe.com/search/images?k=tsessebe&asset_id=153266289
https://stock.adobe.com/search/images?k=tsessebe&asset_id=433137353

Blesbok
https://www.shutterstock.com/it/image-photo/adult-male-blesbok-damaliscus-pygargus-phillipsibrown-365902583
https://www.natureinstock.com/search/preview/blesbok-damaliscus-dorcas-phillipsi-running-rietvlei-nature-reserve/0_10092533.html
https://dewetswild.com/tag/blesbok/#jp-carousel-10774

Posted on March 30, 2023 06:34 PM by

milewski | 14 comments | Leave a comment

Adaptive colouration in the tsessebe (Damaliscus lunatus), using the related blesbok for reference

The tsessebe (Damaliscus lunatus lunatus, https://www.inaturalist.org/observations?page=5&place_id=any&taxon_id=132770) has inconspicuous colouration (https://www.inaturalist.org/observations/37263205 and https://www.inaturalist.org/observations/9839665).

This is true also for the colouration of infants, which differs from that of adults (https://www.inaturalist.org/observations/71462883 and https://www.inaturalist.org/observations/37125342 and https://www.inaturalist.org/observations/146636730).

However, in some illuminations, adults can be conspicuously dark:

https://www.inaturalist.org/observations/92012376

https://www.inaturalist.org/observations/39831997

https://www.inaturalist.org/observations/18538387

https://www.inaturalist.org/observations/11164916

https://www.inaturalist.org/observations/70079188

https://www.inaturalist.org/observations/68374123

https://www.inaturalist.org/observations/133577345

https://www.inaturalist.org/observations/122347068).

And in others, parts of the hindquarters can gleam conspicuously pale:

https://www.inaturalist.org/observations/38883371

https://www.inaturalist.org/observations/64096933

https://www.inaturalist.org/observations/41206964

https://www.inaturalist.org/observations/129408411

https://www.inaturalist.org/observations/25107320

This variation seems to be partly owing to sheen/antisheen effects (https://www.inaturalist.org/observations/3758158).

In this Post, my approach is to compare D. lunatus lunatus with its congener, the blesbok (Damaliscus pygargus phillipsi). This has the advantage of setting search-images for various features of colouration.

My reference for ageing criteria is https://journals.co.za/doi/pdf/10.10520/AJA03794369_3447 and https://journals.co.za/doi/10.10520/AJA03794369_3447.

POSTERIOLATERAL VIEW

Both the blesbok and the tsessebe have sheeny, pale pelage on the hindquarters, centred on the uppermost, innermost buttocks.

Both thus qualify for pygal flags, that of the tsessebe being the more nebulous.

The blesbok and the tsessebe share a definite dark/pale pattern on the posterior surface of the upper foreleg. In the case of the blesbok, this consists of medium-dark tone vs white, whereas in the tsessebe it consists of dark vs medium-pale tone.

Although the patterns are homologous, that of the blesbok qualifies as an ulnar flag, whereas that of the tsessebe does not. The maximum conspicuousness' in the case of the tsessebe is shown in https://www.inaturalist.org/observations/150756739. However, this is not typical.

What this means is that the tsessebe possesses what is a residual/incipient version of the ulnar flag of the blesbok.

Tsessebe
http://elelur.com/data_images/mammals/tsessebe/tsessebe-05.jpg and https://www.inaturalist.org/observations/144361837 and https://www.inaturalist.org/observations/118506712 and https://depositphotos.com/3781313/stock-photo-tsessebe-antelope.html and https://www.inaturalist.org/observations/98036633 and https://www.inaturalist.org/observations/128580048 and https://www.inaturalist.org/observations/147820212 and https://www.inaturalist.org/observations/98259096 and https://www.inaturalist.org/observations/35030694 and https://dewetswild.com/2016/08/19/tsessebe/#jp-carousel-11105

LATERAL VIEW, STANDING

The blesbok possesses an abdominal flag, consisting of whitish pelage on the lower, posterior flanks adjacent to the knee. By contrast, the tsessebe lacks this feature.

Blesbok
https://es.123rf.com/photo_27663869_a-blesbok-antelope-damaliscus-pygargus-standing-in-grassland-south-africa.html and https://www.shutterstock.com/it/image-photo/blesbok-antelope-damaliscus-pygargus-standing-grassland-188464454

Tsessebe
https://www.inaturalist.org/observations/10837294 and https://www.alamy.com/stock-photo-common-tsessebe-or-sassaby-damaliscus-lunatus-adult-tswalu-game-reserve-82278402.html?imageid=18F300CB-EFDC-4FF0-8CB0-32FDCE7C6FE5&p=183822&pn=1&searchId=5192abfe2eb2ff377a78ed28e4e410a7&searchtype=0 and https://www.inaturalist.org/observations/115444682 and https://static3.depositphotos.com/1003671/199/i/950/depositphotos_1994858-stock-photo-tsessebe-antelope.jpg and https://www.istockphoto.com/photo/side-profile-of-a-tsessebe-in-the-okavango-gm671171024-122820291?phrase=rare%20tsessebe%20antelope

LATERAL VIEW, WALKING

The blesbok possesses a pedal flag, consisting of whitish on the lower legs, particularly the inner surface of the lower foreleg. By contrast, the tsessebe lacks this feature, because the lower legs, although clear in their pattern, are not pale enough to be conspicuous even when in motion.

Blesbok
https://www.gettyimages.com.au/detail/photo/walking-blesbok-antelope-royalty-free-image/92951936?phrase=blesbok&adppopup=true and https://www.istockphoto.com/photo/blesbock-gm952958116-260157634?phrase=damaliscus%20pygargus and https://www.alamy.com/stock-photo-blesbok-or-blesbuck-damaliscus-pygarus-phillipsi-taken-in-malolotja-26006805.html?imageid=293E67B1-C1FE-49F5-9696-23117B99C0E3&p=71234&pn=1&searchId=6d99a604ddf21778a01ac0ac2dd5d43c&searchtype=0

Tsessebe
https://www.istockphoto.com/photo/tssessebe-antelope-walking-gm153781884-14706397?phrase=rare%20tsessebe%20antelope and https://depositphotos.com/2710639/stock-photo-tsessebe-antelope.html and https://www.alamy.com/stock-photo-tsessebe-damaliscus-lunatus-adult-tswalu-game-reserve-kalahari-northern-133686151.html?imageid=D10C4D7D-3D82-459D-AA8C-46C48BDAF4ED&p=370234&pn=1&searchId=638830104d5bcdd149a7a39518b32940&searchtype=0 and https://www.flickr.com/photos/42964440@N08/11613575174 and https://www.flickr.com/photos/42964440@N08/52018313557 and
https://www.alamy.com/stock-photo-common-tsessebe-or-sassaby-damaliscus-lunatus-adult-tswalu-game-reserve-82278396.html?imageid=92CF3892-7E2D-4676-9038-F5289D651E9F&p=183822&pn=1&searchId=5192abfe2eb2ff377a78ed28e4e410a7&searchtype=0
and https://www.alamy.com/common-tsessebe-in-kruger-national-park-south-africa-specie-damaliscus-lunatus-lunatus-family-of-bovidae-image223005272.html?imageid=C3A65609-19F1-4000-AA7D-9D1DCEFE0327&p=272677&pn=1&searchId=5192abfe2eb2ff377a78ed28e4e410a7&searchtype=0 and https://www.inaturalist.org/observations/146520629 and https://www.inaturalist.org/observations/3739293

LATERAL VIEW, GRAZING

Blesbok
https://www.istockphoto.com/photo/blesbok-gm469912880-62692804?phrase=damaliscus%20pygargus and https://www.istockphoto.com/photo/blesbok-antelopes-gm530930427-54934768?phrase=damaliscus%20pygargus and https://www.istockphoto.com/photo/blesbok-gm469912846-62692942?phrase=damaliscus%20pygargus and https://www.istockphoto.com/photo/blesbok-gm469912934-62692998?phrase=damaliscus%20pygargus and https://www.istockphoto.com/photo/blesbok-gm469912860-62692906?phrase=damaliscus%20pygargus

Tsessebe
https://www.inaturalist.org/observations/107836119 and https://www.inaturalist.org/observations/135798052 and https://www.inaturalist.org/observations/130471373

HEAD

In adults of the tsessebe, both the rostrum and the centre of the forehead have consistently dark pelage.

The pattern follows that of the pale rostrum and forehead of the blesbok, apart from the facts that the dark in the tsessebe does not reach the rhinarium, and is not constricted just above eye-level.

The major difference is that the dark on the face of the tsessebe does not qualify as either a facial bleeze or a facial flag. This is because of

a lack of dark/pale contrast,
the glossiness of the pigmented pelage, which diminishes the darkness in bright sunlight, and
the much smaller size of the head and rostrum, relative to the body, in the tsessebe than in the blesbok.

In both the blesbok and the tsessebe, the anterior surface of the ear pinnae has whitish hairs, which can be somewhat conspicuous at certain distances and in certain illuminations (https://www.istockphoto.com/photo/tsessebe-stood-in-savannah-gm514687285-47692892?phrase=rare%20tsessebe%20antelope).

However, a major difference is that the blesbok has sheeny pale on the posterior surface of the ear pinnae, constituting an auricular flag. In the tsessebe, this auricular flag is categorically absent, because the pelage on the back-of-ear is not pale in any illumination.

Blesbok
https://es.123rf.com/photo_24809221_blesbok-antelope-with-white-face-and-brown-fur.html and https://www.dreamstime.com/stock-image-blesbok-antelope-image11998831

Tsessebe
https://upload.wikimedia.org/wikipedia/commons/4/4f/Tsessebe_%28Damaliscus_lunatus_lunatus%29_close-up_%2811684009833%29.jpg and https://www.inaturalist.org/observations/144145418 and https://www.dreamstime.com/tsessebe-damaliscus-lunatus-antelope-closeup-eating-grass-kruger-national-park-south-africa-image223199288 and https://www.inaturalist.org/observations/10004626 and https://www.inaturalist.org/observations/27402360 and https://stock.adobe.com/search?k=%22common+tsessebe%22&asset_id=563936100

In some individuals of the tsessebe, there is a faint dark streak on the temple and posterior to the eye (First photo in https://www.inaturalist.org/observations/50551594). This is homologous with the pale streak seen in juveniles and adolescents of the blesbok (https://www.alamy.com/stock-photo-bontebok-damaliscus-pygargus-pygargus-juvenile-close-up-of-head-bontebok-52963924.html). However, in the tsessebe its adaptive significance is questionable.

TAIL

The tail is surprisingly different in structure in the blesbok vs the tsessebe. In the former, the tail-tassel is relatively large and bushy, whereas in the latter the tail-tassel is relatively small and two-dimensional (laterally flattened). This difference is visible already in infants, when the dark tone has yet to develop.

However, w.r.t. adaptive colouration, there is little difference between the blesbok and the tsessebe. This is because in neither case is the tail displayed in an antipredator context, or during stotting. There is an argument for a caudal flag in a social/sexual context in the case of the blesbok, but even this is questionable in the tsessebe.

Blesbok
https://willdlife.fandom.com/wiki/Blesbuck?file=Blesbok.jpg

Tsessebe
https://stock.adobe.com/search?k=%22common+tsessebe%22&asset_id=284355340

INFANTS

In both the blesbok and the tsessebe, infants differ from adults in colouration, being fawn with countershading, with the dark tail-tassel merely incipient. (Please note that the tail-tassels have different shapes, already at birth.)

However, three differences are that:

infants of the blesbok are slightly paler than those of the tsessebe, and the cheeks (https://cites.org/eng/node/7488) and inner surfaces of the lower forelegs of the former are actually whitish,
the tsessebe lacks the crisp border between pale on the cheeks and medium tone on the rostrum, and
the pale patch on the posterior surface of the upper foreleg is so poorly-developed in the tsessebe that it is hardly noticeable.

Blesbok
https://www.zooborns.com/zooborns/2018/08/meet-betty-bantu-belfasts-blesbok-calf.html and https://www.shutterstock.com/it/image-photo/blesbok-blesbuck-calf-stays-close-members-1671765892 and https://www.shutterstock.com/it/image-photo/blesbok-mother-small-calf-leaning-against-91405400 and scroll in https://www.marwell.org.uk/animal/blesbok/

Tsessebe

1 week old
https://www.istockphoto.com/photo/tsessebe-calf-gm484277658-71087461?phrase=tsessebe%20antelope%20calf and https://www.inaturalist.org/observations/68999662 and https://www.alamy.com/stock-photo-calf-of-common-tsessebe-damaliscus-lunatus-ssp-lunatus-170825820.html?imageid=9E00EA1C-46E3-4037-978E-ECD8766D366B&p=178601&pn=1&searchId=5192abfe2eb2ff377a78ed28e4e410a7&searchtype=0 and https://www.istockphoto.com/photo/tsessebe-cow-with-calf-gm475327908-65199031?phrase=tsessebe%20antelope%20calf

1 month old
https://upload.wikimedia.org/wikipedia/commons/7/7c/Young_Tsessebe_%28Damaliscus_lunatus_lunatus%29_%2811683592113%29.jpg and https://es.123rf.com/photo_48516678_young-calf-of-a-rare-tsessebe-antelope-damaliscus-lunatus-in-natural-habitat-south-africa.html and https://www.istockphoto.com/photo/tsessebe-antelope-calf-gm497099840-78935531?phrase=tsessebe%20antelope%20calf and https://www.istockphoto.com/photo/tsessebe-antelope-calf-gm495085272-77807447?phrase=tsessebe%20antelope%20calf

2 months old
https://www.inaturalist.org/observations/105625612

JUVENILES

In the blesbok, the facial colouration goes through a complex juvenile pattern which is transitional but not intermediate between the infantile and adult patterns.

In the tsessebe, this complexity is absent, and the patterns are simple and intermediate.

Blesbok
https://dewetswild.com/tag/blesbok/#jp-carousel-27210
https://dewetswild.com/tag/blesbok/#jp-carousel-26027
https://dewetswild.com/tag/blesbok/#jp-carousel-36067
https://dewetswild.com/tag/blesbok/#jp-carousel-10773
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.alamy.com/blesbok-damaliscus-pygargus-phillipsi-young-walking-in-open-grassland-alert-mountain-zebra-national-park-eastern-cape-south-africa-africa-image229930083.html
Also please see https://www.inaturalist.org/journal/milewski/75995-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi-part-2-infants-juveniles-and-adolescents#

Tsessebe

3 months old
https://www.istockphoto.com/photo/tsessebe-antelope-calf-gm153774679-15462675?phrase=tsessebe%20antelope%20calf and https://www.inaturalist.org/observations/107836121

4 months old
https://st2.depositphotos.com/1003671/8344/i/950/depositphotos_83445528-stock-photo-tsessebe-antelope-portrait.jpg

5 months old
https://www.robertharding.com/preview/764-6170/topi-tsessebe-damaliscus-lunatus-calf-kruger-national-park/

6 months old
https://stock.adobe.com/search?k=%22common+tsessebe%22&asset_id=262135765 and https://www.shutterstock.com/it/image-photo/leierantilope-oder-halbmondantilope-common-tsessebe-damaliscus-1462604654

9 months old
https://www.alamy.com/stock-photo-common-tsessebe-or-sassaby-damaliscus-lunatus-adult-pair-tswalu-game-82278408.html?imageid=F77DAB1C-4325-495E-A284-3180E5E1DD99&p=183822&pn=1&searchId=5192abfe2eb2ff377a78ed28e4e410a7&searchtype=0 and https://www.inaturalist.org/observations/57781574

DISCUSSION

The tsessebe, although congeneric with the blesbok and lacking a mane, a beard, and a long tail-tassel, resembles wildebeests rather than the blesbok, in adaptive colouration.

The tsessebe, like the blesbok, has pelage showing sheen/antisheen effects. These effects are more important in the case of the tsessebe, which lacks any whitish pelage other than at a small-scale on the front-of-ear.

Undermining my interpretation is the following view, in which the dark antisheen effect in Connochaetes gnou is not seen in the tsessebe (https://www.dreamstime.com/stock-photo-tsessebe-black-wildebeest-antelope-southern-african-savanna-image92924850 and https://www.dreamstime.com/stock-photo-black-wildebeest-tsessebe-antelope-southern-african-savanna-image92740554).

The adornment of the face with mud by the tsessebe is consistent with the small size of the horns, and the lack of a conspicuous pattern of colouration on the face.

In the closely related species, Damaliscus jimela, the tail is raised during proud-trotting, in masculine display (https://www.flickr.com/photos/90785747@N02/25779599611/). However, this display has not been recorded in the tsessebe.

Infants of the tsessebe and the blesbok have a generic similarity. However, the difference is that the facial bleeze, ulnar flag, and pedal flag - features lacking in the tsessebe - are already incipient at birth in the blesbok.

Posted on March 28, 2023 09:35 AM by

milewski | 49 comments | Leave a comment

Three patterns of colouration in one species: the ontogenetic 'triplexity' of the blesbok/bontebok (Damaliscus pygargus)

@errol-d

At first glance, the most remarkable aspect of the colouration of the blesbok/bontebok (Damaliscus pygargus) is the whitish rostrum, which constitutes a facial bleeze.

The bold, pale feature on the face of this species is extreme among all of the ungulates. This is because

in the blesbok, it is the most conspicuous feature on the whole figure (https://www.inaturalist.org/observations/130975314), and
in the bontebok, the white on the face is only one of several large-scale, conspicuously pale features, but it is exceptionally stark and crisply-defined (https://www.warwicktarboton.co.za/other%20crea%20pgs/332BntBk.html).

However, on closer scrutiny, what may be more remarkable is that D. pygargus features three different patterns of colouration within each individual - following each other from birth to adulthood.

Another way of putting this is that infants, juveniles, and adults of D. pygargus have such different colouration that they are like three different species in one.

The main aim of this Post is to illustrate this 'triplex' colouration by means of a few, carefully selected photos.

CRYPTIC COLOURATION

Within D. pygargus, something approaching a classic example of cryptic colouration occurs: plain fawn with countershading.

This occurs from birth to three months old, after which it changes abruptly. Thus, the 'infantile' colouration lasts until weaning begins.

The cryptic 'infantile' pattern makes little sense adaptively, because there is no rationale for inconspicuousness in this species, even in infants.

Blesbok infants https://www.robertharding.com/preview/741-3687/blesbok-damaliscus-dorcas-kariega-game-reserve-south-africa/ and https://www.zooborns.com/zooborns/2018/08/meet-betty-bantu-belfasts-blesbok-calf.html

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

DARK FACE CONTRASTING WITH PALE CHEEKS

For the next three months, when the freshly-weaned juveniles weigh about half as much as their mothers, the pattern on the face differs from those of both infants and adults. This facial pattern is

more complex than in either infants or adults, and
not intermediate between that of infants and that of adults (https://twitter.com/VelizarSim/status/1457031473689677833 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=blesbok&order=relevance&price%5B%24%5D=1&safe_search=1&search_page=2&get_facets=0&search_type=pagination&asset_id=200580481).

Supporting the interpretation that this constitutes a frontal display is the fact that the upper forelegs darken, precocially, at this stage.

The frontally conspicuous juvenile makes little sense adaptively, because there is no rationale for adults and accompanying juveniles achieving frontal conspicuousness' in different ways.

Blesbok juveniles 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 and 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

Bontebok juveniles 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

CONSPICUOUSLY PALE FACE

Gradually and with individual variation, the rostrum turns from dark to pale, and the cheeks turn from pale to dark. The pale tends to creep upwards from the nose towards the eyes.

The conspicuous colouration of adults of D. pygargus makes sense, in principle. This is because gregarious, cursorial ungulates of open environments have nowhere to hide from predators, and have much to gain from social cohesion. However...

Bontebok adult 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=1&searchId=b907bfe35d3c66fdb917f996c60ff601&searchtype=0

DISCUSSION

The 'triplexity' of colouration in D. pygargus remains to be explained, in adaptive terms.

Also remaining unexplained, in D. pygargus, are why

this species exceeds other members of the same genus in conspicuous colouration,
the face is the location of particular conspicuousness,
in adults, the bontebok greatly exceeds the blesbok in the conspicuousness of the colouration, and
in infants and juveniles, the blesbok somewhat exceeds the bontebok in the conspicuousness of the colouration.

Also see:
https://www.inaturalist.org/journal/milewski/76599-the-mystery-of-the-adaptive-value-of-cryptic-colouration-for-the-first-three-months-of-life-in-the-bontebok#
https://www.inaturalist.org/journal/milewski/76550-a-concise-photo-guide-to-the-differences-some-previously-overlooked-between-blesbok-and-bontebok#
https://www.inaturalist.org/journal/milewski/75748-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi-part-1-adults#
https://www.inaturalist.org/journal/milewski/75995-adaptive-colouration-in-the-blesbok-damaliscus-pygargus-phillipsi-part-2-infants-juveniles-and-adolescents#
https://www.inaturalist.org/journal/milewski/76311-adaptive-colouration-in-the-bontebok-damaliscus-pygargus-pygargus-part-1-adults#
https://www.inaturalist.org/journal/milewski/76336-adaptive-colouration-in-the-bontebok-damaliscus-pygargus-pygargus-part-2-infants-juveniles-and-adolescents#

Posted on March 22, 2023 10:52 PM by

milewski | 11 comments | Leave a comment

Stotting in Damaliscus pygargus

https://theworldlink.com/news/local/2-month-old-bontebok-debuts-at-zoo/article_961cedbc-bb8a-11ec-b170-673e9365c94b.html and https://www.oregonzoo.org/node/7361/media and https://www.facebook.com/watch/?v=1029640830966480 and last few seconds of https://www.pond5.com/stock-footage/item/65434541-springbok-impala-wildebeest-and-blesbok

Posted on March 19, 2023 12:45 AM by

milewski | 20 comments | Leave a comment

Mysteries of the adaptive value of colouration in the bontebok, particularly 'infantile' crypsis and the divulgence of pregnancy

@tonyrebelo @jeremygilmore

I have recently described the colouration of the bontebok (https://www.inaturalist.org/journal/milewski/76311-adaptive-colouration-in-the-bontebok-damaliscus-pygargus-pygargus-part-1-adults# and https://www.inaturalist.org/journal/milewski/76336-adaptive-colouration-in-the-bontebok-damaliscus-pygargus-pygargus-part-2-infants-juveniles-and-adolescents#).

However, my use of the term 'infant' is, in a way, misleading.

This is because the 'infantile' colouration in Damaliscus pygargus actually persists over a trebling of body mass after birth.

The back of neonates only reaches the height of the maternal udder:

https://www.thetablemountainfund.org.za/species-in-focus-the-bontebok/

After three months of growth, the back of 'infants' (really juveniles that have retained infantile colouration as the tips of the horns appear) reaches the height of the maternal anus:

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

This means that the latter are really 'juveniles dressed as infants'.

An important point about adaptive colouration in the bontebok thus emerges:

The ostensibly cryptic 'infantile' colouration, which is countershaded plain fawn (https://en.wikipedia.org/wiki/Crypsis#:~:text=Many%20animals%20have%20evolved%20so,animal%20itself%20(disruptive%20coloration), cannot actually function cryptically.

This is because

infants do not hide even in the first few weeks of life, and
their accompaniment of the group means that the cryptic potential of their colouration is subverted by the conspicuousness of the adults near them.

Among ruminants, the bontebok is extreme in the dichotomy between the infantile and adult patterns of colouration. These patterns are so different that the only elements in common are:

whitish on the ventral surface of the thorax, and on the inner surfaces of the upper hindlegs,
whitish on the ulnar surface, on the posterior of the upper foreleg,
whitish on the anterior surfaces of the ear pinnae,
a small white triangle just above the rhinarium,
a demarcation in tone on the side of the rostrum, and
darkness at the tip of the tail (the tassel being merely incipient at birth).

These elements are functionally trivial, and cannot outweigh the categorical difference in pattern.

The infantile colouration of the bontebok resembles that of adults of a thoroughly inconspicuous ruminant, the bohor reedbuck (https://www.inaturalist.org/taxa/42304-Redunca-redunca).

Were it the case that infants hide for several weeks, and that the infantile colouration is lost at several weeks old, then the infantile colouration of the bontebok could be interpreted as adaptive. However, such is not the case.

So, how has the evolutionary process resulted in the infantile colouration of the bontebok?

This adds to at least two other unsolved questions about the colouration of the bontebok, viz.

how is it adaptive for the bontebok to be so much more conspicuous than other species of Damaliscus - including the blesbok, which ostensibly belongs to the same species?
how is it adaptive for the white ventral panel to be configured in such a way that it reveals heavy pregnancy to potential predators, thus accentuating a vulnerability?

The following show how conspicuous pregnancy is in the bontebok, owing to the distension of the pale ventral panel:

https://www.inaturalist.org/observations/97905171

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=b907bfe35d3c66fdb917f996c60ff601&searchtype=0

https://www.bbc.com/news/science-environment-52881831

https://www.dreamstime.com/stock-photo-bontebok-wide-open-field-medium-sized-generally-dark-brown-antelope-prominent-white-blaze-image77512544

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

https://depositphotos.com/598312898/stock-photo-bontebok-damaliscus-pygargus-bushmans-kloof.html

https://www.mediastorehouse.com/ardea-wildlife-pets-environment/animals/mammals-bovidae-bontebok/bonteboks-fynbos-13230782.html

https://www.inaturalist.org/observations/68890585

scroll to 12th photo in https://puppy1952.wordpress.com/category/the-overberg/

https://www.flickr.com/photos/christiansanchez/15277125719

Posted on March 17, 2023 11:20 PM by

milewski | 17 comments | Leave a comment

A concise photo-guide to the differences (some previously overlooked) between blesbok and bontebok

@geichhorn @michalsloviak @tonyrebelo @jeremygilmore @tandala @colin25 @paradoxornithidae @simontonge @henrydelange @jwidness @chewitt1 @douglasriverside @matthewinabinett @bobby23 @bluehillescape

I have recently scrutinised all of the thousands of photos, on the Web, of Damaliscus pygargus (https://www.inaturalist.org/taxa/42275-Damaliscus-pygargus).

The following are my findings, w.r.t. the differences in appearance between the two subspecies.

In all cases, I show the blesbok (Damaliscus pygargus philipsi) first, and the bontebok (Damaliscus pygargus pygargus) second.

Please note that sexual dimorphism is greater in the blesbok than in the bontebok.

MALE BODY FORM STOUTER IN BLESBOK

Blesbok https://es.123rf.com/photo_27663869_a-blesbok-antelope-damaliscus-pygargus-standing-in-grassland-south-africa.html
Bontebok https://www.krugerpark.co.za/africa_bontebok.html

HORNS LONGER IN BLESBOK

Female:

Blesbok https://www.dreamstime.com/royalty-free-stock-photos-blesbok-antelope-image3045098
Blesbok https://www.agefotostock.com/age/en/details-photo/blessbock-damaliscus-pygargus-phillipsi-suedafrika-afrika-gruppe-blesbok-damaliscus-pygargus-phillipsi-south-africa-group/ZON-2448458/1
Bontebok 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=e1c83791dbb28b2649d55bb669e0fbda&searchtype=0

Male:

Blesbok https://www.agefotostock.com/age/en/details-photo/blesbok-damaliscus-pygargus-phillipsi-adult-in-open-grassland-feeding-on-dry-grass-mountain-zebra-national-park-eastern-cape-south-africa-africa/ZI6-3207749/1
Bontebok https://www.alamy.com/bontebok-damaliscus-pygargus-damaliscus-dorcas-damaliscus-dorcas-dorcas-on-grassland-south-africa-bredasdorp-de-hoop-nature-reserve-image255390786.html

MALE HORNS PALER IN BLESBOK

Blesbok https://www.agefotostock.com/age/en/details-photo/blesbok-damaliscus-pygargus-phillipsi-mountain-zebra-national-park-south-africa-africa/RHA-764-3210/1
Bontebok https://www.gettyimages.com.au/detail/photo/bontebok-damaliscus-dorcas-at-bontebok-national-royalty-free-image/523049311?phrase=bontebok&adppopup=true

TAIL:
PALE STALK LONGER IN BONTEBOK
TASSEL PALER AND LONGER IN BLESBOK

Blesbok https://www.alamy.com/blesbok-damaliscus-pygargus-phillipsi-an-antelope-endemic-to-south-africa-and-swaziland-grazing-in-grassland-image344938371.html
Blesbok https://www.gettyimages.no/detail/photo/blesbok-antelopes-in-heat-royalty-free-image/547464562?adppopup=true
Bontebok https://www.dreamstime.com/stock-image-bontebok-antelope-image14126791

BACK-OF-EAR SHEENIER IN BLESBOK

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

LOWER LEGS CLEARER IN BONTEBOK

Blesbok https://upload.wikimedia.org/wikipedia/commons/3/3a/Damaliscus_pygargus_phillipsi.jpg
Bontebok https://www.alamy.com/stock-photo-bontebok-antelope-17066360.html?imageid=AFA96455-2E25-41C8-91B0-1B7B94A1EA3C&p=4877&pn=1&searchId=abde0ec3b06a08943ffb523ff66f0db0&searchtype=0

RUMP CLEARER IN BONTEBOK

Blesbok https://www.istockphoto.com/photo/beautiful-blesbok-antelope-with-a-white-face-standing-in-the-green-field-gm1455330187-490697231?phrase=pics%20of%20a%20blesbok
Bontebok https://www.inaturalist.org/observations/57714646

PALE FACE MORE EXPANSIVE IN BLESBOK

TORSO:
VENTRAL PALE MORE EXTENSIVE IN BONTEBOK
BACK MORE CONTRASTING WITH FLANKS IN BONTEBOK

Blesbok https://www.agefotostock.com/age/en/details-photo/bontebok-blesbok-damaliscus-dorcas-stands-in-african-savanna-south-africa-eastern-cape-mountain-zebra-national-park/BWI-BS420963
Bontebok https://www.gettyimages.com.au/detail/photo/bontebok-damaliscus-dorcas-endemic-species-of-royalty-free-image/139810109?phrase=bontebok&adppopup=true

BACK-OF-FORELEG MORE DISTINCT IN BLESBOK

INFANTS PALER IN BLESBOK

INFANTILE FACIAL MARKINGS CLEARER IN BONTEBOK

Blesbok https://www.shutterstock.com/it/image-photo/blesbuck-newborn-baby-89983321
Blesbok https://stock.adobe.com/search/images?k=blesbok&asset_id=544432933
Bontebok https://www.shutterstock.com/it/image-photo/bontebok-calf-national-park-swellendam-western-2090432353
Bontebok https://www.inaturalist.org/observations/137997739
Bontebok https://upload.wikimedia.org/wikipedia/commons/e/e4/Bontebok_%28Damaliscus_pygargus_pygargus%29_young_..._%2832834333045%29.jpg
Bontebok https://www.flickr.com/photos/berniedup/50179826247

JUVENILE FACE DARKER IN BLESBOK

Blesbok https://www.agefotostock.com/age/en/details-photo/juvenile-blesbok-damaliscus-pygargus-phillipsi-mountain-zebra-national-park-south-africa-africa/RHA-764-4222/1
Blesbok https://www.agefotostock.com/age/en/details-photo/juvenile-blesbok-damaliscus-pygargus-phillipsi-mountain-zebra-national-park-south-africa-africa/RHA-764-4226/1
Bontebok https://www.gettyimages.com.au/detail/photo/bontebok-damaliscus-dorcas-at-bontebok-national-royalty-free-image/523049313?phrase=bontebok&adppopup=true

PALE SPOT ON FOREHEAD APPEARS AT >1 YEAR IN BLESBOK, VS 4 MONTHS IN BONTEBOK

Blesbok https://www.inaturalist.org/observations/21633759
Blesbok https://www.istockphoto.com/photo/young-blesbok-gm947259792-258650817
Blesbok 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
Bontebok https://es.123rf.com/photo_10162424_bontebok-damaliscus-dorcas-at-bontebok-national-park-in-south-africa.html
Bontebok https://www.shutterstock.com/it/image-photo/bontebok-antelope-calf-national-park-south-124597081
Bontebok https://www.shutterstock.com/it/image-photo/bontebok-antelope-female-calf-national-park-124597063

DISCUSSION

I have not featured the usual distinction, viz. that of a separation between the pale rostrum and the pale patch on the forehead (https://www.dreamstime.com/stock-image-blesbok-buck-head-image29082851).

This is because it has been overrated, given the individual variation and a tendency for coalescence with age in the blesbok.

Of the distinctions I have featured above, a few are well-known, but most have been previously underplayed - or completely overlooked.

Features which seem never to have been previously mentioned in the literature are those involving

the ears, tail-tassel, and expansion of pale on the face, and
the facial colouration of infants and juveniles.

Regarding the ears and tail-tassel, the previous oversight is understandable, because a particular search-image is needed. However, regarding expansion of pale on the face, the previous oversight is surprising. This is because dozens of photos of the blesbok on the Web, particularly from zoological gardens, show the phenomenon clearly.

The distinctions between the blesbok and the bontebok at the infantile and juvenile stages deserve further scrutiny, beyond the limited photographic evidence.

This is partly because ontogenetic differences - as well as those of sexual dimorphism - are likely to be particularly revealing, taxonomically.

Given this comprehensive list of phenological clues, it remains possible that the blesbok and the bontebok are different species, not merely subspecies.

Posted on March 16, 2023 06:12 PM by

milewski | 37 comments | Leave a comment

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

@tonyrebelo @jeremygilmore @ludwig_muller @botswanabugs @oviscanadensis_connerties @tandala @capracornelius @michalsloviak @henrydelange @ray_turnbull @bit @matthewinabinett @fdoucet @felix_riegel @jaunnemarelize @dbeadle @paradoxornithidae @geichhorn @alexiadievart @coyotehog2 @lswift @stanvrem @cheekychew @jandutoit @bobby23 @jwidness @gigilaidler @simontonge @markheystek @bluehillescape

...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

a trace of the ulnar pattern (see the posterior surface of the upper foreleg in https://www.alamy.com/stock-photo-young-bontebok-damaliscus-pygargus-dorcas-in-postberg-west-coast-national-26607506.html?imageid=A6BE5E5E-5F5F-4685-894F-CFAC80895E31&p=18540&pn=3&searchId=6d8a7f95c3b92935b5e8c1d5d07d00ff&searchtype=0),
an incipient dark tip to the tail, and
a subtle, but consistent and crisply-defined, pattern on the head.

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 rostrum and forehead are fawn-coloured, with a crisp demarcation on the side of the rostrum (https://www.shutterstock.com/it/image-photo/bontebok-calf-national-park-swellendam-western-2090432353),
the orbits are white, extending towards the corner of the mouth (https://www.inaturalist.org/observations/137997739),
the upper lips are fawn-coloured, but there is a small triangle of whitish pelage just above the rhinarium (https://en.wikipedia.org/wiki/Rhinarium),
the cheeks are a pale tone of fawn, grading to whitish medially (https://upload.wikimedia.org/wikipedia/commons/e/e4/Bontebok_%28Damaliscus_pygargus_pygargus%29_young_..._%2832834333045%29.jpg),
the ventral surface of the mandibles are white, extending to the area between the gape of the mouth and the cheeks (https://www.flickr.com/photos/berniedup/50179826247),
the base of the ear is whitish, and
the posterior surface of the ear pinnae is simply fawn-coloured, like most of the animal (https://www.inaturalist.org/observations/83966791).

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 probably about 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://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

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 pygal 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 pygal 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#.

Posted on March 15, 2023 03:39 AM by

milewski | 20 comments | Leave a comment

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

Posted on March 14, 2023 04:15 PM by

milewski | 0 comments | Leave a comment

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

the extreme colouration of this species, in combining a bold facial pattern with plain colouration over the rest of the figure (https://www.inaturalist.org/observations/142404442), and
the extremely large size of the ear pinnae at birth (https://es.123rf.com/photo_27725391_roan-antelope-hippotragus-equinus-calf.html).

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.

Posted on March 13, 2023 09:23 PM by

milewski | 28 comments | Leave a comment