Adaptive colouration in the tsessebe (Damaliscus lunatus 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://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=tsessebe&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=338204623

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/anti-sheen 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, particularly the uppermost, innermost buttocks.

Both thus possess flags, that of the tsessebe being the more nebulous.

However, the difference in the patterns means that the blesbok possesses a pygal flag (with an extension on to the ischial surface), whereas the tsessebe possesses an ischial flag (with an extension in to the pygal surface).

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.

Blesbok
https://www.dreamstime.com/royalty-free-stock-photo-blesbok-blesbuck-damaliscus-pygargus-phillipsi-antelope-endemic-to-south-africa-has-distinctive-white-face-forehead-which-inspired-image29787325 and https://www.agefotostock.com/age/en/details-photo/blesbok-damaliscus-dorcas-phillipsi-adult-standing-in-highveld-grassland-malolotja-n-p-swaziland/FHR-10014-00020-125 and https://www.dreamstime.com/beautiful-blesbok-antelope-white-face-standing-green-field-beautiful-blesbok-antelope-white-face-standing-image265943449 and https://stock.adobe.com/search/images?k=blesbok&asset_id=357665041 and https://stock.adobe.com/search/images?k=blesbok&asset_id=3548113 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&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=195859381 and https://www.alamy.com/blesbok-damaliscus-phillipsi-damaliscus-dorcas-phillipsi-damaliscus-pygargus-phillipsi-standing-in-savanna-south-africa-eastern-cape-mountain-zebra-national-park-image255390768.html?imageid=2191134B-223A-4F72-9776-0F9F1267384F&p=851122&pn=1&searchId=34a5985d254a7cecee5d7188055b6b4c&searchtype=0 and https://www.gettyimages.com.au/detail/photo/blesbok-royalty-free-image/1351086134?phrase=blesbok&adppopup=true and https://www.gettyimages.com.au/detail/photo/blesbok-royalty-free-image/595653647?phrase=blesbok&adppopup=true and https://www.shutterstock.com/it/image-photo/blesbok-blesbuck-damaliscus-pygargus-phillipsi-seen-1750679021

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.

Unlike the blesbok, the tsessebe adorns its horns and face with mud (https://stock.adobe.com/search/images?k=tsessebe&asset_id=221536847 and https://stock.adobe.com/search/images?k=tsessebe&asset_id=221541047 and https://www.istockphoto.com/photo/tsessebe-antelope-gm509859867-46033092?phrase=rare%20tsessebe%20antelope 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=tsessebe&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=342803399 and https://www.istockphoto.com/photo/portrait-of-a-tsessebe-antelope-mokala-national-park-south-africa-gm1411594832-461366583?phrase=rare%20tsessebe%20antelope and https://www.agefotostock.com/age/en/details-photo/portrait-of-a-rare-tsessebe-antelope-damaliscus-lunatus-south-africa/ZON-1791354 and https://www.inaturalist.org/observations/14220603 and https://www.flickr.com/photos/eboechat/51074690038 and https://www.istockphoto.com/photo/tsessebe-antelope-gm155307406-10065450?phrase=rare%20tsessebe%20antelope).

TAIL

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

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

1 month old
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

1.5 month old
https://es.123rf.com/photo_48516678_young-calf-of-a-rare-tsessebe-antelope-damaliscus-lunatus-in-natural-habitat-south-africa.html and https://www.inaturalist.org/observations/105625612
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

2.5 months old
https://upload.wikimedia.org/wikipedia/commons/7/7c/Young_Tsessebe_%28Damaliscus_lunatus_lunatus%29_%2811683592113%29.jpg and https://www.istockphoto.com/photo/tsessebe-antelope-calf-gm153774679-15462675?phrase=tsessebe%20antelope%20calf

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.inaturalist.org/observations/107836121 and https://st2.depositphotos.com/1003671/8344/i/950/depositphotos_83445528-stock-photo-tsessebe-antelope-portrait.jpg

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

5 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

8 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.

Evidence for some degree of adaptive conspicuousness, overall, in the tsessebe is the lack of countershading on the ventral surface of the torso in adults and juveniles. The effect - shared with all wildebeests - is that pigmentation and shading combine to produce dark emphasis of the ventral silhouette of the figure (https://www.alamy.com/stock-photo-tsessebe-damaliscus-lunatus-pilanesberg-game-reserve-south-africa-59766243.html?imageid=17060BC4-FD2A-422D-AD94-6F9B95E6AFA7&p=22059&pn=1&searchId=303cfda7336cba6c5732f1db91b12f81&searchtype=0 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=tsessebe&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=545632874 and https://www.inaturalist.org/observations/38771518).

However, the dark anti-sheen 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).

Furthermore, the tsessebe does not appear as dark as Connochaetes taurinus mattosi, when viewed in the same illumination (https://www.gettyimages.ie/detail/photo/moremi-royalty-free-image/162394086?phrase=damaliscus%20korrigum&adppopup=true).

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 tsessebe, the tail is inconspicuous compared with those of other alcelaphins. The tail-stalk is long but slender, and the tail-tassel is much smaller than in wildebeests (Connochaetes), and somewhat smaller than in hartebeests (Alcelaphus, 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=tsessebe&order=relevance&price%5B%24%5D=1&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=553535621) and the blesbok.

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/). Has this display 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.

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

Publicado el marzo 28, 2023 09:35 MAÑANA por milewski