Subtle differences between the tsessebe (southern Africa) and the topi (East Africa)

@tonyrebelo @jeremygilmore @tandala @davidbygott @michalsloviak @oviscanadensis_connerties @paradoxornithidae @beartracker @jwidness @matthewinabinett @simontonge

The tsessebe (Damaliscus lunatus) of southern Africa and the topi (Damaliscus jimela) of East Africa are similar enough that they possibly constitute subspecies of a single species.

The aim of this Post is not to present any opinion on this taxonomic problem.

Instead, it is to show clearly the differences in conformation and colouration, which seem only partly to have been described in the literature.

It is only when the differences are fully appreciated that a verdict can be reached on the phylogenetic relationship.

Here, I assume that readers are familiar with the difference in the horns, which I will not mention again.

BODY CONFORMATION

Both the tsessebe and the topi have high withers, leading to an oft-repeated impression that the backs slope. In fact, the back, posterior to the withers-hump and including the sacrum, is actually level, at least in the topi. Only in the tsessebe does the back seem to slope. To the degree that this difference is real, it also gives an impression that the hindquarters are slightly more massive in the topi than in the tsessebe.

Tsessebe

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=522689966

https://www.alamy.com/stock-photo-topi-tsessebe-damaliscus-lunatus-moremi-wildlife-reserve-botswana-16929399.html?imageid=6C82058C-23C3-4427-AD16-6B0A29E18961&p=31903&pn=6&searchId=c7d97a4328b8ff32aa812bc4af94c292&searchtype=0

https://www.alamy.com/stock-photo-tsessebe-antelope-13946832.html?imageid=F3E5645E-D37B-49BD-9CC5-D2F6EB7D83CB&p=4877&pn=2&searchId=5a975ca1461ca04a69177e15a216926e&searchtype=0

https://www.alamy.com/stock-photo-stock-photo-of-a-tsessebe-damaliscus-lunatus-standing-near-a-termite-26652363.html?imageid=1F5F7F68-CB36-414F-BBB5-72B176ADFA29&p=42009&pn=1&searchId=303cfda7336cba6c5732f1db91b12f81&searchtype=0

https://www.alamy.com/stock-photo-portrait-of-a-tsessebe-damaliscus-lunatus-in-the-bush-the-photo-was-33096619.html?imageid=0AC6D7CF-C7D2-470F-BAF2-82961C3B7274&p=60598&pn=4&searchId=e495fe81b41c4ac2a2aa1b51980ecf14&searchtype=0

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=4&search_type=pagination&get_facets=0&asset_id=522690103

Please scroll to 9th photo in https://2summers.net/2017/08/04/three-incredible-moments-kruger/

Topi

https://www.dreamstime.com/topi-antelope-damaliscus-lunatus-kenya-s-masai-mara-reserve-topi-antelope-damaliscus-lunatus-image115564457

https://www.alamy.com/topi-and-calf-in-masai-mara-ethiopia-image425061474.html?imageid=D13A3A77-1F46-49F6-99BD-9F2EFA4118CF&p=1441596&pn=13&searchId=f322b5f6226f7eb79da5fe0b2e082c98&searchtype=0

https://www.alamy.com/stock-photo-common-tsessebe-damaliscus-lunatus-serengeti-national-park-tanzania-20925395.html?imageid=53B57C4E-B9F5-4D5F-8CA0-629E9719F6BD&p=53352&pn=1&searchId=303cfda7336cba6c5732f1db91b12f81&searchtype=0

https://www.dreamstime.com/topi-antelope-damaliscus-lunatus-kenya-s-masai-mara-reserve-topi-antelope-damaliscus-lunatus-image115564457

FACIAL CONFORMATION

In the tsessebe, the head tends to be held with the muzzle relatively level. In the topi, the head tends to be held with the muzzle relatively steep. This difference possibly results from the neck being held less erect, and the head less elevated, in the tsessebe than in the topi.

In the tsessebe, the rostrum (defined as in https://upload.wikimedia.org/wikipedia/commons/f/ff/Wolf_cranium_labelled.jpg) is slightly concave, in profile.

By contrast, in the topi, the shape is slightly convex.

(For illustrations, please see under facial colouration, below, plus a Comment.)

OVERALL COLOURATION

The colouration of the topi is more vivid than that of the tsessebe.

This includes small-scale patterns of questionable adaptive value, such as that on the posterior surfaces of the ear pinnae (https://www.alamy.com/mother-hartebeest-trying-to-protect-baby-from-male-in-mara-triangle-image243042736.html?imageid=D43BC0B8-93CC-4767-AE23-B7A2A5485EFF&p=296441&pn=12&searchId=53054e670b20d7bcea4fcf5dd77c86b3&searchtype=0).

Brindling is better-developed in the tsessebe than in the topi.

The tsessebe, in some illuminations, appears dark overall (https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=10&search_type=pagination&get_facets=0&asset_id=338204623). However, this is seldom true for the topi (https://stock.adobe.com/search?k=%22common+tsessebe%22&asset_id=443024629).

Tsessebe

https://www.alamy.com/side-profile-of-a-tsessebe-in-the-okavango-delta-botswana-image333968863.html?imageid=2CFC8504-786E-4553-A861-2D893B896D6D&p=1218170&pn=1&searchId=303cfda7336cba6c5732f1db91b12f81&searchtype=0

https://www.alamy.com/okavango-mammals-image359935672.html?imageid=17576026-5B7D-4E29-86E9-5D3F3BE4A18A&p=196286&pn=4&searchId=e495fe81b41c4ac2a2aa1b51980ecf14&searchtype=0

https://www.alamy.com/stock-photo-starring-tsessebe-in-the-okavango-delta-botswana-138669205.html?imageid=AB37E9B7-C477-49BE-A42A-271F639BED6E&p=298586&pn=5&searchId=d453d84f287dda1ba917b393c69ffbae&searchtype=0

https://www.alamy.com/stock-photo-tsessebe-antelope-in-southern-african-savanna-141670011.html?imageid=FEBF9BB4-4D9E-4EDA-9725-D8270C8ACB72&p=291902&pn=5&searchId=d453d84f287dda1ba917b393c69ffbae&searchtype=0

https://www.alamy.com/an-aerial-view-of-two-tsessebes-damaliscus-lunatus-and-their-calves-okavango-delta-botswana-image448136392.html

Topi

https://www.inaturalist.org/observations/152104042

https://www.inaturalist.org/observations/83911314

https://www.inaturalist.org/observations/16659049

https://upload.wikimedia.org/wikipedia/commons/5/51/Topi_%28Damaliscus_lunatus_jimela%29_female_with_calf.jpg

ISCHIOPYGAL FLAG

Both the tsessebe and the topi may qualify for ischiopygal flags.

However, this pattern is clearer in the topi than in the tsessebe. In particular, the pigmentation on the haunches can seem relatively intense in the topi.

Thus, in some views at least, a pale/dark contrast appears at the junction of the haunches and the ventral part of the buttocks of the topi (https://www.inaturalist.org/observations/100139762). In the tsessebe, this is so subdued that the relatively pigmented patch seems always to be obscured by a dull sheen (please scroll to the 13th photo in https://www.mammalwatching.com/2009/09/06/south-africa-2009-trip-report/).

Tsessebe

https://www.alamy.com/stock-image-four-topi-tsessebe-antelope-damaliscus-lunatus-portrait-duba-plains-168439251.html?imageid=9CA38C80-9BBF-4CE3-9730-F6E94E794331&p=190655&pn=2&searchId=5a975ca1461ca04a69177e15a216926e&searchtype=0

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=3&searchId=ba759c4393b858b38648b74f7e988098&searchtype=0

https://www.alamy.com/stock-photo-tsessebe-antelope-at-waterhole-38607359.html?imageid=D343034F-D54D-47C6-888A-6D4FBE52A4CA&p=4877&pn=3&searchId=ba759c4393b858b38648b74f7e988098&searchtype=0

https://www.alamy.com/tsessebe-damaliscus-lunatus-mokala-national-park-south-africa-image479269312.html?imageid=F257B06F-83B3-4599-9A37-417DA834AC86&p=1884070&pn=4&searchId=e495fe81b41c4ac2a2aa1b51980ecf14&searchtype=0

Topi

https://www.gettyimages.co.uk/detail/photo/topi-antelopes-at-wild-royalty-free-image/1312854978?phrase=topi%20antelope&adppopup=true

https://www.gettyimages.co.uk/detail/photo/topi-antelope-at-wild-royalty-free-image/1257975365?phrase=topi%20antelope&adppopup=true

https://www.alamy.com/stock-photo-topi-damaliscus-lunatus-also-known-as-tsessebe-in-kenyas-masai-mara-12361353.html?imageid=C2951267-B9D2-4840-9D92-BF41A795AAF8&p=3616&pn=16&searchId=e1dc7e88d3225c439fd56c16145d0d60&searchtype=0

https://www.alamy.com/a-topi-gazelle-in-the-kenyan-savanna-amidst-a-grassy-landscape-image363905270.html?imageid=C2E3F057-5252-48AC-902A-7A21637C6172&p=276975&pn=12&searchId=53054e670b20d7bcea4fcf5dd77c86b3&searchtype=0

https://www.alamy.com/topi-tsessebe-damaliscus-lunatus-masai-mara-national-reserve-kenya-image68345741.html?imageid=F21DED71-1ADC-4301-955B-9FF194C45A98&p=40816&pn=3&searchId=ba759c4393b858b38648b74f7e988098&searchtype=0

https://www.inaturalist.org/observations/142135123

https://www.inaturalist.org/observations/102025376

The following clearly show - particularly in the light of sheen effects - the difference in the ischial colouration between adults and infants in the topi (https://www.gettyimages.co.uk/detail/photo/topi-mother-and-her-baby-in-masai-mara-royalty-free-image/1353037453?phrase=topi%20antelope&adppopup=true and https://www.gettyimages.co.uk/detail/photo/topi-with-young-standing-on-savannah-mara-kenya-royalty-free-image/200329150-001?phrase=topi%20antelope&adppopup=true and https://www.gettyimages.co.uk/detail/photo/topi-mother-and-calf-royalty-free-image/528054745?phrase=topi%20antelope&adppopup=true and https://www.alamy.com/topi-calf-and-its-mom-in-the-african-savannah-image331705027.html?imageid=596D3A8F-067D-4EF8-B93B-4358480FE57C&p=868817&pn=10&searchId=97fb6d5702fce239879b42856b9ac22e&searchtype=0 and https://www.alamy.com/topi-calf-and-its-mom-in-the-african-savannah-image331704636.html?imageid=3BC9E218-FB7B-44D5-B00A-540A7C61D89D&p=868817&pn=10&searchId=97fb6d5702fce239879b42856b9ac22e&searchtype=0 and https://www.alamy.com/topi-calf-and-its-mom-in-the-african-savannah-image331704903.html?imageid=9DB0768D-3986-4D61-BF1E-0FA702A11BBC&p=868817&pn=10&searchId=97fb6d5702fce239879b42856b9ac22e&searchtype=0)

The ischial pattern is one of the first to appear as soon as the infantile colouration is outgrown (https://www.alamy.com/topi-damaliscus-lunatus-jimela-subspecies-of-the-common-tsessebe-walk-through-a-field-with-baby-in-maasai-mara-national-reserve-kenya-image242679906.html).

The following, of juveniles (about 3.5 months old) of the topi, show that the dark feature on the haunches is relatively precocial. In particular, please note that the dark on the posterior surface of the upper foreleg (see ULNAR FLAG below) has yet to appear
(https://www.gettyimages.co.uk/detail/photo/side-view-of-deer-standing-on-dirt-road-royalty-free-image/1286160642?phrase=topi%20antelope&adppopup=true and https://www.alamy.com/the-topi-antelope-in-the-kenyan-savanna-in-the-middle-of-the-grass-landscape-image364473932.html?imageid=C7A66959-DF0F-4C9E-8ECF-E60AD4AD01DC&p=276975&pn=15&searchId=a0557c0a3d4c017133cb83a5f01cb6a7&searchtype=0 and https://www.alamy.com/the-topi-antelope-in-the-kenyan-savanna-in-the-middle-of-the-grass-landscape-image364473918.html?imageid=2D020203-11A8-4127-A6E7-572F3FE37611&p=276975&pn=15&searchId=a0557c0a3d4c017133cb83a5f01cb6a7&searchtype=0 and https://www.alamy.com/the-topi-antelope-in-the-kenyan-savanna-in-the-middle-of-the-grass-landscape-image364473936.html?imageid=5F86B148-AE38-45F0-A465-E635CC877A40&p=276975&pn=15&searchId=a0557c0a3d4c017133cb83a5f01cb6a7&searchtype=0 and https://www.alamy.com/a-topi-antelope-in-the-grassland-of-kenyas-savannah-image362972537.html?imageid=7C84E977-09AE-435D-99A9-BAAA8B1D4AA7&p=276975&pn=10&searchId=97fb6d5702fce239879b42856b9ac22e&searchtype=0).

However, there is much individual variation (https://stock.adobe.com/search?k=%22common+tsessebe%22&asset_id=47040948).

The following, of the topi, show the variable conspicuousness of the ischial pattern, depending on sheen effects.

This applies to both the depigmented pelage of the buttocks (which is conspicuously pale only when 'lit up' by sheen) and the pigmented pelage of the haunches - which, in the topi, is conspicuously dark only when viewed from behind and when not 'greyed' by a dull sheen (https://www.gettyimages.co.uk/detail/photo/topi-herd-damaliscus-korrigum-on-savanna-tanzania-royalty-free-image/128139798?phrase=topi%20antelope&adppopup=true and https://www.alamy.com/topis-damaliscus-korrigum-waiting-to-cross-the-mara-river-in-the-masai-mara-national-reserve-in-kenya-image343978623.html?imageid=0C8529D2-1CC7-48DF-B5D5-6EEE015B9879&p=1249180&pn=15&searchId=a0557c0a3d4c017133cb83a5f01cb6a7&searchtype=0 and https://www.alamy.com/topis-damaliscus-korrigum-waiting-to-cross-the-mara-river-in-the-masai-mara-national-reserve-in-kenya-image343978653.html?imageid=7D1A7A88-8EB0-4CE0-BF84-2E2F778DC2B7&p=1249180&pn=15&searchId=a0557c0a3d4c017133cb83a5f01cb6a7&searchtype=0).

ULNAR FLAG

The topi may marginally qualify for an ulnar flag, whereas the tsessebe probably does not.

The pattern on the posterior surface of the upper foreleg (https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=191026767) is similar in the tsessebe and the topi.

It tends to be most visible in the same posteriolateral views that show off the ischial pattern. The ischial and ulnar patterns are thus parts of a single composite pattern, the basic function of which is advertisement of the figure.

In the tsessebe, the dark surface on the posterior of the upper foreleg is not as dark as in the topi. It is, thus, in the topi that - as in the case of the ischial feature - the ulnar pattern is the more conspicuous.

The following, of the tsessebe (https://www.gettyimages.co.uk/detail/photo/topi-botswana-southern-africa-royalty-free-image/75500957?phrase=topi%20antelope&adppopup=true) nicely shows the importance of sheen in the conspicuousness of the pale features of the ulnar and ischial patterns.

Tsessebe

https://www.shutterstock.com/it/image-photo/tsessebe-aka-sasseby-damaliscus-lunatus-once-2185328013

https://www.alamy.com/stock-photo-tsessebe-okavango-delta-botswana-southern-africa-12737786.html?imageid=39EAFB4D-8DBC-457E-BA61-A4756E31148C&p=10587&pn=5&searchId=d453d84f287dda1ba917b393c69ffbae&searchtype=0

https://www.alamy.com/stock-photo-tsessebe-antelope-21869245.html?imageid=A5C922FC-E4A5-445C-A470-274FB6BB5DA0&p=4877&pn=2&searchId=5a975ca1461ca04a69177e15a216926e&searchtype=0

https://www.alamy.com/stock-photo-rare-tsessebe-antelope-damaliscus-lunatus-in-natural-habitat-south-82963272.html?imageid=2039DF4A-B9C5-4482-9E76-83B4D41B1826&p=70019&pn=2&searchId=5a975ca1461ca04a69177e15a216926e&searchtype=0

Topi

https://www.alamy.com/the-topi-antelope-in-the-kenyan-savanna-in-the-middle-of-the-grass-landscape-image364473919.html?imageid=CC2F0CD7-82C7-49FD-A6E5-FA4C736C40A6&p=276975&pn=15&searchId=a0557c0a3d4c017133cb83a5f01cb6a7&searchtype=0

https://www.alamy.com/stock-photo-kenya-masai-mara-topi-damaliscus-lunatus-side-view-15328201.html?imageid=600969F7-278E-4FAA-AE27-A65385DDE5FA&p=50040&pn=15&searchId=a0557c0a3d4c017133cb83a5f01cb6a7&searchtype=0

https://www.alamy.com/stock-photo-female-topi-inspecting-and-touching-her-newborn-baby-masai-mara-kenya-12109476.html?imageid=BBC25A56-D020-4A8C-BDBD-6B93C2C6A1CC&p=6945&pn=16&searchId=e1dc7e88d3225c439fd56c16145d0d60&searchtype=0

https://www.alamy.com/stock-image-kenya-topi-damaliscus-korrigum-standing-on-termite-mound-168773190.html?imageid=4A93A0DB-DC87-4780-A5A1-93D04B9B231D&p=570783&pn=16&searchId=e1dc7e88d3225c439fd56c16145d0d60&searchtype=0

https://www.alamy.com/topi-damaliscus-korrigum-in-the-grasslands-of-the-serengeti-national-park-tanzania-image241315141.html?imageid=FF744C1E-A708-48E1-A789-0AF5D7520194&p=11478&pn=5&searchId=d453d84f287dda1ba917b393c69ffbae&searchtype=0

The following (https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=51313804) shows that the ulnar flag only forms when the juvenile colouration becomes adult.

FACIAL COLOURATION: ADULTS AND JUVENILES

Both the tsessebe and the topi have dark pelage on the rostrum, extending through the forehead to the crown. However, the topi has additional dark markings on the side of the face, which are virtually absent in the tsessebe.

The additional dark pelage in the topi is as follows:

These markings first appear in juveniles (https://www.gettyimages.co.uk/detail/photo/side-view-of-topi-antelopes-standing-on-dirt-mound-royalty-free-image/1297788674?phrase=topi%20antelope&adppopup=true and https://www.agefotostock.com/age/en/details-photo/topi-damaliscus-lunatus-adult-close-up-of-head-chewing-cud-masai-mara-kenya/FHR-11182-00108-676/1) and adolescents (https://www.vecteezy.com/photo/1407708-closeup-of-a-beautiful-topi-antelope).

Tsessebe

https://www.alamy.com/stock-photo-lone-tsessebe-in-the-okavango-delta-botswana-136680172.html?imageid=D07BAF8D-44DD-4C9A999E-769570FD4B87&p=71679&pn=1&searchId=303cfda7336cba6c5732f1db91b12f81&searchtype=0

https://www.alamy.com/stock-photo-tsessebe-antilope-portrait-50389566.html?imageid=73949FD0-F456-4DBB-A064-387599B6A974&p=4877&pn=2&searchId=5a975ca1461ca04a69177e15a216926e&searchtype=0

https://www.alamy.com/stock-photo-common-tsessebe-176099261.html?imageid=6F862364-D204-4C9B-92FA-8019AF2DF1D4&p=467750&pn=4&searchId=e495fe81b41c4ac2a2aa1b51980ecf14&searchtype=0

https://www.alamy.com/common-tsessebe-damaliscus-lunatus-detail-portrait-of-big-brown-african-mammal-in-nature-habitat-sassaby-in-green-vegetation-kruger-national-park-image417773091.html?imageid=1CC9A023-E654-41CA-93FE-A5D2E84E4C13&p=388741&pn=5&searchId=d453d84f287dda1ba917b393c69ffbae&searchtype=0

https://www.alamy.com/stock-photo-tsessebe-topi-side-view-portrait-21736398.html?imageid=F1BC7D47-5B7F-4326-A7C3-0B1C47DC3541&p=34420&pn=6&searchId=c7d97a4328b8ff32aa812bc4af94c292&searchtype=0

Topi

https://www.alamy.com/topi-damaliscus-korrigum-image69169872.html?imageid=D3B701B6-3130-4396-9172-8AE66998068D&p=205178&pn=11&searchId=16d88bd7c0a4b8132c0f6f44a66cb3e7&searchtype=0

https://www.alamy.com/side-view-of-a-topi-in-the-masai-mara-kenya-with-space-for-your-text-image260305122.html?imageid=1589AADE-1EB4-4EA2-B90D-4F42BCE8DDD0&p=365052&pn=13&searchId=f322b5f6226f7eb79da5fe0b2e082c98&searchtype=0

https://www.alamy.com/stock-photo-a-single-topi-close-view-of-head-and-shoulders-lewa-conservancy-kenya-129379783.html?imageid=2AACA7BC-5D0C-4AD8-8115-3A5088D3A833&p=212476&pn=10&searchId=97fb6d5702fce239879b42856b9ac22e&searchtype=0

https://www.alamy.com/stock-photo-topi-damaliscus-korrigum-single-adult-resting-and-lying-in-short-grass-83236789.html?imageid=4B66495E-ADBA-4906-816E-41E3308DBA59&p=88393&pn=10&searchId=97fb6d5702fce239879b42856b9ac22e&searchtype=0

https://www.alamy.com/stock-photo-eating-antelope-topi-in-national-park-masai-mara-in-kenya-27210278.html?imageid=17F44FEB-A7D2-49DC-B315-8F260F837C69&p=19389&pn=10&searchId=97fb6d5702fce239879b42856b9ac22e&searchtype=0

https://www.alamy.com/adult-topi-side-view-portrait-with-space-for-text-horizonal-banner-format-image260305114.html?imageid=DCC65082-6168-4B47-B003-642C99563B66&p=365052&pn=15&searchId=a0557c0a3d4c017133cb83a5f01cb6a7&searchtype=0

https://www.alamy.com/stock-photo-topi-maasai-mara-kenya-africa-15241756.html?imageid=CC302D65-C89E-422A-8EE6-6799F8D841B8&p=49976&pn=16&searchId=e1dc7e88d3225c439fd56c16145d0d60&searchtype=0

FACIAL COLOURATION: INFANTS

The tsessebe also seems to differ from the topi in the facial colouration of newborns. Only in the topi is the pelage surrounding the eyes noticeably pale (https://www.alamy.com/stock-photo-topi-calf-damaliscus-korrigum-in-the-masai-mara-kenya-east-africa-21432497.html?imageid=527538F9-280A-4192-97FB-0B67EB010374&p=46517&pn=1&searchId=7352300610b4ba83e1bb162a1696be8d&searchtype=0).

Tsessebe

https://www.alamy.com/topi-mother-and-calf-image387822145.html?imageid=F1714382-B66D-460A-88CC-D5778593679A&p=1732688&pn=1&searchId=7352300610b4ba83e1bb162a1696be8d&searchtype=0

https://upload.wikimedia.org/wikipedia/commons/f/ff/Young_Tsessebe_%28Damaliscus_lunatus_lunatus%29_%2811683857613%29.jpg

https://www.alamy.com/stock-photo-tsessebe-with-young-damaliscus-lunatus-okavango-delta-botswana-25902406.html?imageid=3EE4F44A-E996-4E63-8EC7-8FC7F4CA314A&p=74587&pn=2&searchId=5a975ca1461ca04a69177e15a216926e&searchtype=0

Topi

https://www.alamy.com/topi-calf-masai-mara-national-reserve-kenya-image338053309.html?imageid=AD25AD50-51A5-4011-83A8-A233E558AF07&p=190967&pn=14&searchId=beab1a5c4c9bf8c9c1893d2a62a8d03a&searchtype=0

https://www.alamy.com/stock-photo-two-young-topi-tsessebe-damaliscus-lunatus-masai-mara-kenya-16040606.html?imageid=2ACF3915-574F-4618-9407-71A1B227F1C3&p=50273&pn=16&searchId=e1dc7e88d3225c439fd56c16145d0d60&searchtype=0

https://www.alamy.com/stock-photo-topi-and-calf-damaliscus-korrigum-in-the-masai-mara-kenya-east-africa-21432509.html?imageid=C0552FB4-625A-48F4-9F91-035D1A440B6F&p=46517&pn=16&searchId=e1dc7e88d3225c439fd56c16145d0d60&searchtype=0

https://www.alamy.com/topi-damaliscus-korrigum-newborn-just-after-birth-masai-mara-game-reserve-kenya-october-image263002125.html?imageid=F0F6D1BB-EA2E-4187-BFEB-7BD41C3615C5&p=269351&pn=6&searchId=c7d97a4328b8ff32aa812bc4af94c292&searchtype=0

https://www.dreamstime.com/stock-photo-closeup-sideview-single-topi-calf-behind-mother-standing-grass-masai-mara-national-reserve-kenya-image82831099

https://www.alamy.com/stock-photo-korrigum-topi-damaliscus-korrigum-mother-grooming-calf-masai-mara-125538992.html?imageid=1CC4E83D-51B0-4EC9-AA51-CBCF286BC6DD&p=361129&pn=2&searchId=45a60d399aec05dabc5ff5a4d18c8bcb&searchtype=0

DISCUSSION

(Also please see https://www.inaturalist.org/journal/milewski/71651-sex-ratio-of-standing-on-termite-mounds-by-the-topi-damaliscus-jimela#.)

The tsessebe and the topi may have significant ecological differences.

For example, a lekking mode of courtship has been recorded only in the topi (https://psycnet.apa.org/record/1988-19261-001 and https://www.pnas.org/doi/10.1073/pnas.142125899 and https://www.sciencedirect.com/science/article/abs/pii/S0003347205809224).

This may be associated with a difference in habitat and behaviour, as follows.

For differences w.r.t. the use of mud, please see https://www.inaturalist.org/journal/milewski/80122-the-tsessebe-as-a-mudbuck#.

One way of interpreting these differences:
the topi is more adapted than the tsessebe to visibility and self-advertisement.

Also see https://www.inaturalist.org/journal/milewski/77839-the-optically-puzzling-haunch-patch-of-the-topi-damaliscus-jimela#

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#.

Posted on Απρίλιος 02, 2023 0538 ΜΜ by milewski milewski

Σχόλια

The pattern on the hindquarters of the topi clearly qualifies as a flag. However, giving it a name is complicated by the fact that in some photos the sheeny pale is restricted to the buttocks (which would make it an ischial flag), whereas in others the sheeny pale extends on to the rump (a surface better-described as pygal).

https://www.alamy.com/a-topi-antelope-in-the-grassland-of-kenyas-savannah-image362972214.html?imageid=6E126B08-6CFE-4544-A323-1C8F64365614&p=276975&pn=10&searchId=97fb6d5702fce239879b42856b9ac22e&searchtype=0

https://www.gettyimages.co.uk/detail/photo/topi-antelopes-at-wild-royalty-free-image/1312855116?phrase=topi%20antelope&adppopup=true

Αναρτήθηκε από milewski 12 μήνες πριν

The following, of an adolescent male individual of the topi (https://www.alamy.com/topi-antelope-in-masai-mara-kenya-image501324722.html?imageid=5E21A7D0-37CC-497D-9FE6-1FCBD2CF1897&p=1728330&pn=10&searchId=97fb6d5702fce239879b42856b9ac22e&searchtype=0), shows:
a) the maximum intensity of pigmentation in the dark markings, and
b) the maximum extent of the dark markings on the face.

Αναρτήθηκε από milewski 12 μήνες πριν

The following, of the topi, allows comparison of the ischial patterns of adult females and juveniles about 5 months old. The ischial flag is somewhat precocial, whereas the (ambivalent) ulnar flag is not:

https://www.alamy.com/stock-photo-female-topi-with-calf-herd-of-eland-in-background-masai-mara-national-12109554.html?imageid=6BCBECC6-D8A9-439B-9054-68FD645EE551&p=6945&pn=14&searchId=beab1a5c4c9bf8c9c1893d2a62a8d03a&searchtype=0

Αναρτήθηκε από milewski 12 μήνες πριν

SHEEN ON THE RUMP IN TSESSEBE AND TOPI

The tsessebe and the topi resemble wildebeests (other than Connochaetes gnou) in that, in some illuminations, the rump gleams like a car-bonnet.

This effect is less important in the tsessebe and the topi than in e.g. Connochaetes mearnsi, but it is worth noting, anyway.

The following shows sheen on the rump in the tsessebe:

https://www.alamy.com/stock-photo-african-plains-game-tsessebe-antelope-running-fast-away-from-predators-78677346.html?imageid=7BF01298-5807-4B1F-B8B1-D93DBC6F1F21&p=298851&pn=6&searchId=c7d97a4328b8ff32aa812bc4af94c292&searchtype=0

The following shows a similar effect in the topi. As it happens, this individual is unusual in that the dark-pigmented marking on the haunches is more extensive than usual, extending on to the ventral part of the buttocks:

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=7&search_type=pagination&get_facets=0&asset_id=477417575

Αναρτήθηκε από milewski 12 μήνες πριν
Αναρτήθηκε από milewski 12 μήνες πριν
Αναρτήθηκε από milewski 12 μήνες πριν
Αναρτήθηκε από milewski 12 μήνες πριν
Αναρτήθηκε από milewski 12 μήνες πριν

@tonyrebelo @jeremygilmore @tandala @davidbygott @michalsloviak @oviscanadensis_connerties @paradoxornithidae @beartracker @jwidness @matthewinabinett @simontonge

The following show four previously overlooked differences between the tsessebe and the topi, viz.
a) in normal attentive standing, the tsessebe holds its head so that the rostrum (https://upload.wikimedia.org/wikipedia/commons/f/ff/Wolf_cranium_labelled.jpg) is at an angle of about 45 degrees, whereas in the case of the topi the angle is more like 55 degrees,
b) the rostrum, near the rhinarium, tends to be concave in the tsessebe vs convex in the topi (this applies not only to males, but also to females, https://www.inaturalist.org/observations/147820587),
c) the dark markings on the face show certain differences, and
d) the tsessebe exceeds the topi in the development of brindling on the neck.

Tsessebe

https://www.shutterstock.com/it/image-photo/both-tsessebe-bulls-cows-grow-horns-2222325153

https://www.istockphoto.com/photo/tsessebe-in-profile-gm174275075-25958590

https://www.shutterstock.com/it/image-photo/both-tsessebe-bulls-cows-grow-horns-2222325143

https://www.gettyimages.co.uk/detail/photo/tsessebe-antelope-royalty-free-image/992971572?phrase=topi%20antelope&adppopup=true

https://www.shutterstock.com/it/image-photo/tsessebe-214944739

https://stock.adobe.com/search/images?k=tsessebe&asset_id=522689952

https://stock.adobe.com/search/images?k=tsessebe&asset_id=436079617

Topi

https://www.gettyimages.co.uk/detail/photo/topi-royalty-free-image/1153456319?phrase=topi%20antelope&adppopup=true

https://www.agefotostock.com/age/en/details-photo/side-view-of-a-topi-in-the-masai-mara-kenya-with-space-for-your-text/ESY-057209233/1

https://www.shutterstock.com/it/image-photo/topi-antelope-highly-social-fast-subspecies-1149365138

https://www.agefotostock.com/age/en/details-photo/topi-damaliscus-lunatus-male-masai-mara-kenya-africa/ALM-B41T46/1

https://www.agefotostock.com/age/en/details-photo/side-profile-portrait-of-an-adult-topi-in-the-masai-mara-kenya/ESY-057089269/1

https://www.vecteezy.com/photo/717891-topi-antelope

https://www.alamy.com/topi-damaliscus-korrigum-photographed-in-africa-tanzania-serengeti-image69398486.html

https://upload.wikimedia.org/wikipedia/commons/1/19/Head_of_topi_in_Kenya.jpg

https://www.gettyimages.co.uk/detail/photo/topi-antelope-at-wild-royalty-free-image/1257972997?phrase=topi%20antelope&adppopup=true

https://www.gettyimages.co.uk/detail/photo/topi-masai-mara-national-reserve-kenya-east-africa-royalty-free-image/97391933?phrase=topi%20antelope&adppopup=true

https://www.gettyimages.co.uk/detail/photo/topi-antelope-in-the-national-reserve-of-africa-royalty-free-image/1398002792?phrase=topi%20antelope&adppopup=true

https://stock.adobe.com/search/images?k=tsessebe&asset_id=467328987

https://stock.adobe.com/search?k=%22common+tsessebe%22&asset_id=401852785

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=130112462

Αναρτήθηκε από milewski 12 μήνες πριν
Αναρτήθηκε από milewski 12 μήνες πριν

The following of the topi shows that, in some illuminations, the pale anterior surfaces of the ear pinnae produce a conspicuous effect by contrast with the dark on the face:

https://www.freepik.com/premium-photo/topi-antelope-masai-mara-national-park-kenya_12972508.htm

Αναρτήθηκε από milewski 12 μήνες πριν

The following is one of the clearest illustrations, on the Web, of infants (less than two weeks old) of the tsessebe:

https://www.gettyimages.co.uk/detail/photo/tsessebee-fowl-royalty-free-image/155478573?phrase=topi%20antelope&adppopup=true

Αναρτήθηκε από milewski 12 μήνες πριν

The following shows the modest degree of sexual dimorphism in body size in the topi:

https://www.gettyimages.co.uk/detail/photo/topis-royalty-free-image/151635540?phrase=topi%20antelope&adppopup=true

Αναρτήθηκε από milewski 12 μήνες πριν
Αναρτήθηκε από milewski 12 μήνες πριν

The brindling on the neck in the tsessebe is well-shown in https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=9&search_type=pagination&get_facets=0&asset_id=145113746 and https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=367258139 and https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=522689920.

Αναρτήθηκε από milewski 12 μήνες πριν

The following summarises the status of the colouration on the posterior surface of the upper foreleg. There is a distinct pattern, but it is not consistently conspicuous, because a) the relatively pale part of the pattern is actually medium-tone, not particularly depigmented, b) the sheen effect does not necessarily highlight this relatively pale feature, and c) the most pigmented part of the pattern falls short of being blackish.

https://stock.adobe.com/search/images?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=%22common+tsessebe%22&order=relevance&safe_search=1&limit=100&search_page=9&search_type=pagination&get_facets=0&asset_id=185606980

Αναρτήθηκε από milewski 12 μήνες πριν

ADDITIONAL PHOTOS OF INFANTS OF THE TOPI:

https://www.alamy.com/stock-photo-a-newborn-topi-calf-on-the-masai-mara-in-kenya-53490596.html?imageid=585FCAAD-3393-43B8-ACB9-A8615A759231&p=81564&pn=1&searchId=7352300610b4ba83e1bb162a1696be8d&searchtype=0

https://www.dreamstime.com/stock-photo-closeup-sideview-topi-calf-standing-grass-head-raised-looking-toward-camera-masai-mara-national-reserve-kenya-image82930522

https://www.dreamstime.com/stock-photo-closeup-frontview-topi-calf-standing-grass-head-raised-looking-toward-camera-masai-mara-national-reserve-kenya-image82931487

https://www.dreamstime.com/stock-photo-closeup-sideview-single-topi-calf-standing-grass-masai-mara-national-reserve-kenya-image82830861

https://www.dreamstime.com/stock-photo-closeup-sideview-topi-calf-standing-grass-head-raised-looking-toward-camera-masai-mara-national-reserve-kenya-image82931407

https://www.dreamstime.com/royalty-free-stock-image-calf-topi-antelope-antelopes-resembles-hartebeest-differs-dark-purple-patchings-their-upper-legs-lack-sharply-image37754396

https://www.dreamstime.com/new-born-topi-antelope-masai-mara-kenya-topi-antelopes-resembles-hartebeest-image198401808

https://www.dreamstime.com/new-born-calf-topi-antelope-topi-antelopes-resembles-hartebeest-image198401855

https://www.alamy.com/stock-photo-topi-calf-damaliscus-lunatus-with-its-mother-feeding-in-the-background-43399325.html?imageid=051D78A1-BF7B-4482-A262-E78A69ADE08A&p=39374&pn=1&searchId=7352300610b4ba83e1bb162a1696be8d&searchtype=0

Αναρτήθηκε από milewski 12 μήνες πριν
Αναρτήθηκε από milewski 12 μήνες πριν

@paradoxornithidae

Here is a clear photo of the markings on the cheeks, lips, crown, and ear pinnae of Damaliscus jimela:

https://www.kimballstock.com/popuppreview.asp?db=a&image=AFW+35+JZ0002+01&itemw=4&itemf=0002&itemstep=1&itemx=4

Αναρτήθηκε από milewski 12 μήνες πριν

Thanks for documenting the many differences between topi and tsessebe. Whatever the genetics may say, based on my own field experience with both taxa, I struggle with the idea that they are conspecific. They seem like very different antelopes to me.

Αναρτήθηκε από simontonge 12 μήνες πριν

@simontonge

I agree, and I have the same problem with blesbok and bontebok, which likewise seem quite different enough to be different species.

However, in the spirit of Devil's Advocate:

a useful thought-experiment is to imagine the tsessebe with horns identical to those of the topi.

Would the other differences still remain beyond the plausibility of subspecific status?

Αναρτήθηκε από milewski 12 μήνες πριν

Ha! Maybe not, but, then, if Brown Bears were white would a Polar Bear be a thing? I agree with you about Bontebok and Blesbok, by the way.

Αναρτήθηκε από simontonge 12 μήνες πριν

For Readers curious about the true extent of the differences between the blesbok and the bontebok:

https://www.inaturalist.org/journal/milewski/76550-a-concise-photo-guide-to-the-differences-some-previously-overlooked-between-blesbok-and-bontebok#

Αναρτήθηκε από milewski 12 μήνες πριν

There are many portraits of the topi similar to this, on the Web. However, the following photo (https://www.gettyimages.ie/detail/photo/topi-royalty-free-image/1153456319?phrase=damaliscus%20korrigum&adppopup=true) is noteworthy in showing a particularly mature male specimen, as indicated by the worn horns and the maximally-developed rostrum. Please note that the dark marking on the cheek is absent, although that on the temple is present. This confirms that, in the topi, the expanded markings in the face are not a function of age, in the way they are in the blesbok. Also particularly clear in this photo is the pattern on the lips. I would not describe this as a buccal semet unless ultraviolet, invisible to the human eye, is involved (also see https://www.alamy.com/stock-photo-topi-damaliscus-korrigum-single-adult-resting-and-lying-in-short-grass-83236789.html).

Αναρτήθηκε από milewski 11 μήνες πριν

Please compare the following, which show subadult male individuals of the tsessebe and the topi, in similar situations as they cross a road.

https://stock.adobe.com/search/images?k=tsessebe&asset_id=303081685

https://www.flickr.com/photos/nileshkorgaokar/5082904179

One difference shown particularly clearly here is that, in the tsessebe, the head is relatively small (and indeed the smallest in the genus, proportionately and possibly absolutely).

Also evident are:
a) the ulnar pattern is far clearer in the topi than in the tsessebe,
b) the 'dark' haunch-patch is larger and more distinct in the topi than in the tsessebe,
c) the shape of the rostrum, in profile, is slightly concave in the tsessebe, vs slightly convex in the topi, and
d) the back (posterior to the withers) seems to slope slightly in the tsessebe, but seems level in the topi.

Αναρτήθηκε από milewski 11 μήνες πριν

The following footage of the topi (https://provideofactory.com/video/topi-antelope-grazing-and-walking and https://provideofactory.com/video/topi-antelope-grazing-in-masai-mara and https://provideofactory.com/video/topi-antelope-grazing-in-maasai-mara-national-reserve) shows an intriguing aspect of the ulnar flag (viz. the pattern on the posterior surface of the upper foreleg).

The skin at this anatomical position is repeatedly shuddered, presumably in reaction to the nuisance of insects.

What is odd is that the skin on the hindquarters is not likewise shuddered.

This hints at the possibility that there are, in the topi, two mechanisms of activation for the ulnar flag.

These are a) movements of the forelimbs (in this case walking), and b) shuddering of the skin (possibly performed even when the figure is stationary and insects are absent?).

Has similar shuddering been observed in the blesbok?

Αναρτήθηκε από milewski 11 μήνες πριν

Estes (1991), on page 142, pointed out the 'reverse countershading' of the 'Damaliscus lunatus', viz. 'darker below, lighter above'.

However, he did not point out that the tsessebe (lunatus lunatus) does not exhibit tbis pattern to the same degree as does the topi (jimela).

Αναρτήθηκε από milewski 11 μήνες πριν

Damaliscus lunatus lunatus, mislabelled:

https://www.shutterstock.com/it/image-photo/topi-overlooks-area-standing-on-hill-2142652987

This individual seems to show the maximum extent of the 'dark' haunch-patch in the tsessebe.

Αναρτήθηκε από milewski 11 μήνες πριν

The following nicely shows the darkness of the tsessebe, relative to a coexisting ruminant of medium overall tone, namely Aepyceros melampus:

https://www.inaturalist.org/observations/169670252

Αναρτήθηκε από milewski 9 μήνες πριν

The following (https://www.inaturalist.org/observations/170054576) illustrates important principles of adaptive colouration.

It shows Damaliscus jimela and Eudorcas thomsoni nasalis in the same frame and under the same illumination, albeit at different distances. Both species are adaptively conspicuous, as part of gregariousness in open environments.

In the case of the gazelle, the conspicuousness is achieved by bold contrast between dark and pale on the flank. This, in a sense, converts the whole figure into a 'living flag'.

In the case of the alcelaphin, the principle is different. Conspicuousness is achieved by precluding the countershading that is normal in plain-coloured mammals. The ventral parts of the figure, particularly the ventral surface of the torso and the upper parts of the legs, are dark-pigmented, and further darkened by shading. This underscoring serves to accentuate the ventral outline of the figure - as opposed to the accentuation of the flank in the gazelle.

Αναρτήθηκε από milewski 9 μήνες πριν

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