Journal archives for April 2023

01 April, 2023

Photos of the tsessebe in iNaturalist, labelled for body mass and age since birth

Ruminants grow remarkably rapidly. This limits our ability to estimate the size and age of individuals from photographs.

The tsessebe (Damaliscus lunatus lunatus, https://www.inaturalist.org/observations?taxon_id=132770) is a useful example to begin with, because

Child et al. (1972) 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 (1979) states 'horns became externally visible at five weeks'.

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

BOTSWANA

According to Child et al. 1972 (page 366 in 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. Throughout this Post, I have ignored the sex of the individuals described.

November

The following shows newborns, of body mass about 10 kg. The withers of the infants are hardly as high as the maternal belly (shown even more clearly for the closely-related topi, Damaliscus jimela, in https://www.alamy.com/topi-damaliscus-lunatus-female-with-new-born-calf-massai-mara-kenya-image61099252.html?imageid=524FB694-797E-4AF9-969C-995F7380E022&p=191343&pn=3&searchId=aa055d5f893ca3a60402a79b4144734b&searchtype=0):
https://www.inaturalist.org/observations/100694354

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

The following shows an individual infant ostensibly only 1 month old, but with body mass already at least 20 kg:
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. Body mass is about 20 kg, having doubled since birth. The withers of the infants now reach at least the height of the maternal knee:
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

Late April

The following show juveniles about 6 months old:
https://www.inaturalist.org/observations/171576691

Late June-early July

https://www.inaturalist.org/observations/173664182
https://www.inaturalist.org/observations/125828092

Late July

The following show juveniles about 8 months old. The dark markings are far from fully-developed, particularly on the face. Body mass is probably <60kg, which is about half of maternal body mass. The withers of these juveniles have already reached the height of the maternal sacrum:
https://www.inaturalist.org/observations/143915475
https://www.inaturalist.org/observations/57781574
https://www.inaturalist.org/observations/38168446
https://www.inaturalist.org/observations/4131

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
https://www.inaturalist.org/observations/222799454
https://www.inaturalist.org/observations/222799453
https://www.inaturalist.org/observations/222799451

September

The following show juveniles about 10 months old. Body mass is probably <70 kg:
https://www.inaturalist.org/observations/189516047
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 show juveniles about 11 months old. Body mass is probably >70 kg:
https://www.inaturalist.org/observations/69009855
https://www.inaturalist.org/observations/192022183

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

August

21 months old:
https://www.inaturalist.org/observations/222799406

November

24 months old. Body mass is about 100 kg:
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 (https://en.wikipedia.org/wiki/Kruger_National_Park) and Zimbabwe, the tsessebe gives birth in October (Child et al. 1972).

Accordingly, the results are as follows.

October

Newborns:
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

January

3 months old
second photo in https://www.inaturalist.org/observations/184603378

February

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

The following is stated to be in February. However, this individual infant is certainly <2 months old, suggesting that either the date is incorrect or the population in Hwange National Park does not conform to the seasonality given by Child et al. (1972):
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 (https://en.wikipedia.org/wiki/Caprivi_Strip), the tsessebe gives birth in September (Child et al. 1972).

Accordingly, the results are as follows.

The following shows an infant individual about 1 month old. Either the stated date is incorrect, or the population no longer conforms to the seasonality given in Child et al. (1972):

https://www.inaturalist.org/observations/68999662

September

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

November

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

DISCUSSION

At about 6 months old, the horns reach the length of the ear pinnae, and the body reaches 50 kg.

The progression from 10 kg through 50 kg to 100 kg is summarised, approximately, by the following three photos:

10 kg
https://www.inaturalist.org/observations/9323974

50 kg
https://www.inaturalist.org/observations/57781574

100 kg
https://www.inaturalist.org/observations/2588518

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

These series show that the colouration of the tsessebe does not merely change continuously from infancy to maturity. Instead, there are three stages, within each of which body size covers a considerable range.

The infantile colouration, which is plain fawn with countershading, is unexplained by crypsis, because infants of the tsessebe do not hide even when newborn.

The juvenile colouration, in which the dark markings of adults have nominally appeared but lack intensity for more than a year, is also unexplained. Most precocial is the darkness on the anterior surface of the forelegs. The delay of the darkening on the face until adulthood suggests a social clue rather than a feature adaptive in the context of anti-predation.

Posted on 01 April, 2023 09:19 by milewski milewski | 8 comments | Leave a comment

02 April, 2023

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 02 April, 2023 17:38 by milewski milewski | 70 comments | Leave a comment

05 April, 2023

The three alcelaphin bovids of the Serengeti: a comparison of adaptive colouration, part 1

Dear Reader, please consider the subtle signalling in the following fortuitous comparisons:

https://www.alamy.com/stock-photo-cokes-hartebeest-alcelaphus-buselaphus-cokei-and-topi-damaliscus-lunatus-15876251.html

Scroll to 2nd photo in https://www.thenationalnews.com/lifestyle/travel/circle-of-life-our-guide-to-the-wildebeest-migration-in-kenya-and-tanzania-1.689183

https://www.offset.com/photos/africa-kenya-maasai-mara-national-reserve-young-lion-walking-away-1007049

https://www.agefotostock.com/age/en/details-photo/topi-left-watched-by-a-kongoni-coke-s-hartebeest-which-is-a-sub-species-of-the-red-hartebeest-serengeti-tanzania/RHA-1161-186

In the Serengeti ecosystem, there are three coexisting genera and species of alcelaphin bovids (https://inaturalist.nz/taxa/846320-Alcelaphini), viz.

Furthermore, all are of similar body mass, viz. about 100-200 kg.

This raises the question of the ecological diversification that allows their coexistence. How do the three species differ in their signalling, both socially and in communication with predators?

In this Post, I focus on the similarities and differences among these three, in adaptive colouration.

In particular, I recognise certain themes and patterns of conspicuous colouration, illustrating their incidence in C. mearnsi, D. jimela, and A. cokii.

What complicates this exercise is that alcelaphin bovids are extreme, among all the ruminants of the world, in their development of

SHEEN

Sheen - which produces a non-pigmentational pale effect according to illumination - is an important theme in all three species (https://www.inaturalist.org/observations/70079036).

However, its most important effects differ in anatomical location, as follows:

  • rump/back, i.e. dorsal emphasis, in C. mearnsi,
  • buttocks and rump in D. jimela, and
  • buttocks in A. cokii.

ANTI-SHEEN

A converse theme is anti-sheen, which produces a non-pigmentational dark effect according to illumination.

This is

LACK OF COUNTERSHADING ON TORSO

Related to anti-sheen is another theme, viz. the lack of countershading on the torso. The combination of pigmentation and shading means that the ventral silhouette is underscored, making the whole figure conspicuous.

This is nicely illustrated in https://www.inaturalist.org/observations/150562001. The inner surfaces of the upper legs are somewhat depigmented, as expected according to the principle of countershading. However, there is no such depigmentation on the normally shaded ventral surface of the thorax and abdomen.

(Incidentally, this photo also nicely shows that the beard of C. mearnsi is not consistently pale enough to be conspicuous.)

Of the three species of alcelaphins in the Serengeti, it is A. cokii that shows this theme least clearly. However, it does seem to apply even in this species (https://www.gettyimages.co.uk/detail/photo/male-hartebeest-standing-on-field-ololosokwan-royalty-free-image/1342077720?phrase=kongoni&adppopup=true and https://www.shutterstock.com/it/image-photo/red-hartebeest-walks-across-brown-grass-2220959159 and https://www.inaturalist.org/observations/34843838).

In the following illumination, A. cokii seems at first to show no conspicuous features of colouration (https://www.inaturalist.org/observations/31957048). However, please note that the lack of countershading on the torso does make the figure stand out from the background to some degree.

Supporting this interpretation is that infants of A. cokii possess countershading that is lost in adulthood (https://www.alamy.com/stock-photo-mother-and-baby-hartebeest-alcelaphus-buselaphus-cokes-race-standing-41586065.html?imageid=97FFCDA1-E76D-4DC9-A494-16FAF35E605A&p=39374&pn=1&searchId=6cb6d804e8c2d0cca41f0eed698c3a54&searchtype=0).

Along similar lines, the following show that, in D. jimela, infants differ from adults in possessing countershading (https://www.alamy.com/a-female-topi-damaliscus-lunatus-jimela-followed-by-her-calf-runs-through-dry-grass-serengeti-national-park-tanzania-image336476496.html?imageid=0C711FFD-C359-4129-95FF-76DD226BC931&p=39397&pn=1&searchId=70a63ba4e73d117d4dc267df2c6a9d78&searchtype=0 and https://www.alamy.com/newborn-korrigum-topi-damaliscus-lunatus-korrigum-playing-after-the-rains-masai-mara-game-reserve-kenya-december-image263058037.html?imageid=C4C0FAE6-5E56-4313-9E12-EE16A9882121&p=269351&pn=1&searchId=6cb6d804e8c2d0cca41f0eed698c3a54&searchtype=0).

The following shows that countershading in D. jimela persists to a juvenile stage when the adult markings on shoulders and haunches have already started to appear (https://www.inaturalist.org/observations/27634388).

BRINDLING

See https://www.dreamstime.com/wildebeest-wildebai-also-called-gnu-antelope-genus-connochaetes-hooved-ungulate-mammal-skin-image190267038 and https://www.dreamstime.com/wildebeest-wildebai-also-called-gnu-antelope-genus-connochaetes-hooved-ungulate-mammal-skin-image190267061.

As a theme, brindling is not categorically different from anti-sheen, together with which it is particularly well-developed in alcelaphin bovids.

Brindling is well-developed in C. mearnsi (https://upload.wikimedia.org/wikipedia/commons/f/fb/Blue_Wildebeest%2C_Ngorongoro.jpg), and poorly-developed but present in the other two species.

The following show the maximum brindling in

Having covered the themes, let us focus on the patterns.

PYGAL AND ISCHIAL FLAGS

All three species of alcelaphins in the Serengeti show conspicuous pale on the hindquarters.

In all of them, this is based mainly on sheen.

However, the species differ

  • in the anatomical location of the sheeniest surfaces, and
  • the contribution to pallor by depigmentation of the pelage.

The contribution to conspicuousness of the hindquarters by depigmentation is

The pale feature in the hindquarters is centred on the rump in C. mearnsi, and on the buttocks in D. jimela and A. cokii (https://www.agefotostock.com/age/en/details-photo/topi-left-watched-by-a-kongoni-coke-s-hartebeest-which-is-a-sub-species-of-the-red-hartebeest-serengeti-tanzania/RHA-1161-186 and https://www.inaturalist.org/observations/149771685).

'Pygal' refers to the rump, whereas 'ischial' refers to the buttocks.

The following show the pygal/ischial flags of the three species at their most conspicuous:

The following shows that, in C. mearnsi, the pygal flag arises from the combination of sheen on the rump and anti-sheen on the flanks and haunches (https://www.inaturalist.org/observations/151760045).

Such an effect is rarely seen in A. cokii, but the following does show contrast arising from sheen on the hindquarters vs antisheen on the back (https://www.inaturalist.org/observations/14374050 and https://stock.adobe.com/search?k=%22topi+antelope%22&asset_id=343177249).

The following shows that, even in A. cokii, sheen can occur on the dorsal surface of the rump (https://www.inaturalist.org/observations/35809197). However, this appears too infrequently to qualify as a pygal flag.

In the following views (https://www.agefotostock.com/age/en/details-photo/coke-s-hartebeest-kongoni-alcelaphus-buselaphus-cokii-three-adults-running-in-savanna-serengeti-national-park-tanzania/SSJ-179781 and https://www.inaturalist.org/observations/19944808), the ischial flag is clearly expressed in one of the individuals. This may perhaps be a matter of individual variation. However, I suspect that it is, instead, a matter of sheen.

The following show that the pygal and ischial flags are absent in infants:

In A. cokii, a previously overlooked difference between infants and adults is that the pelage on the uppermost, innermost buttocks is fully depigmented in the former (https://www.alamy.com/cokes-hartebeest-alcelaphus-bucephalus-cokii-mother-and-young-masai-mara-game-reserve-kenya-image262961718.html?imageid=AB2B3BD6-2B1C-4A59-B45C-A24DEEAA1D0E&p=269351&pn=1&searchId=6cb6d804e8c2d0cca41f0eed698c3a54&searchtype=0 and https://www.inaturalist.org/observations/142342276).

ULNAR FLAGS

Ulnar flags are

In D. jimela, the dark pelage on the upper foreleg tends to be darker than that on the upper hindleg, as well as that on the shoulders and haunches. The medium-tone pelage on the posterior surface of the upper foreleg may not be depigmented enough to provide the degree of dark/pale contrast for qualification as a flag. However, sufficient contrast may be achieved by means of sheen.

The following show the pattern most clearly (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 and 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).

Please see https://www.inaturalist.org/observations/35622892 and https://www.inaturalist.org/observations/32009259 and https://www.inaturalist.org/observations/36514600.

In these typical views, the dark on the ulnar surface is intense, that on the hindleg tends to be dissipated by sheen. However, at the same time, the other tone on the ulnar surface remains darker than the pale of the lowermost buttocks.

As a result, dark/pale contrast generally falls short of conspicuousness on both fore and hind surfaces, in different ways. It thus remains ambivalent whether D. jimela qualifies for an ulnar flag or not.

In A. cokii, there is no pattern on the posterior surface of the upper foreleg (https://www.shutterstock.com/it/image-photo/closeup-cokes-hartebeest-scientific-name-connochaetes-772737676 and https://www.shutterstock.com/it/image-photo/hartebeest-maasai-mara-kenya-1896708001).

However, this surface is depigmented enough that, when sheen applies, it can - together with the posterior surfaces of the legs generally - be whitish (https://www.agefotostock.com/age/en/details-photo/red-hartebeest-alcelaphus-buselaphus-serengeti-national-park-tanzania/C64-333509 and https://www.shutterstock.com/it/image-photo/hartebeest-family-nairobi-national-park-2260126749 and https://www.shutterstock.com/it/image-photo/young-hartebeest-leaves-mother-sunlit-savannah-1730346106).

This pallor in A. cokii is poorly explained by the principle of cryptic countershading. Instead, it seems to serve as a conspicuous feature, complementing and extending the ischial flag when viewed in posteriolateral perspective.

FACIAL FLAGS

Facial flags are at best nebulous in adults of the alcelaphin bovids of the Serengeti.

In adults of C. mearnsi, the beard is sometimes conspicuous, particularly when backlit (https://www.gettyimages.ae/detail/video/the-wildebeest-and-its-baby-walking-in-serengeti-stock-video-footage/1089966386?adppopup=true and https://www.gettyimages.ae/detail/video/the-wildebeest-and-its-baby-walking-in-serengeti-stock-video-footage/1089962972?adppopup=true).

However, this is inconsistent, with most photos showing the beard as inconspicuous (https://www.alamy.com/stock-photo-wildebeests-56489832.html?imageid=BE92527C-4766-4A07-AFEA-277226D22E9E&p=180380&pn=4&searchId=e495fe81b41c4ac2a2aa1b51980ecf14&searchtype=0 and https://www.dreamstime.com/isolated-wildebeest-walking-savannah-single-short-green-grass-maasai-mara-image207464059 and https://www.dreamstime.com/portrait-as-lone-female-wildebeest-side-walking-grasslands-maasai-mara-image207464226).

The following hunts at a facial flag in adults of C. mearnsi, in frontal view (https://www.shutterstock.com/it/image-photo/close-whitebearded-wildebeest-standing-facing-camera-1059264716).

In infants of C. mearnsi, the face is precocially dark, to a degree unknown in the genera Damaliscus and Alcelaphus.

Furthermore, this frontal darkness contrasts with the paleness of the cheek, to a degree not seen in adults of C. mearnsi (https://www.shutterstock.com/it/image-photo/adult-wildebeest-stands-beside-recently-born-1277282221 and https://www.kimballstock.com/preview.asp?db=a&image=AFW+03+MC0026+01 and https://www.alamy.com/side-profile-of-a-wildebeest-and-its-calf-running-in-a-field-ngorongoro-conservation-area-arusha-region-tanzania-image376769166.html?imageid=6A76B279-D007-4009-9AC4-A3AC8F486DC9&p=1132882&pn=1&searchId=7a9d75e9925e3ea8c217697d70b14364&searchtype=0 and https://www.alamy.com/blue-wildebeest-connochaetes-taurinus-mother-with-newborn-calf-running-at-the-southern-plains-during-the-migration-ngorongoro-conservation-area-t-image226468917.html?imageid=4C5F3612-7996-4AAE-B872-BFEFE733DB9C&p=157727&pn=1&searchId=7a9d75e9925e3ea8c217697d70b14364&searchtype=0 and https://www.alamy.com/newborn-calf-running-between-two-adult-wildebeest-lake-ndutu-tanzania-image246936718.html?imageid=FAB728C2-9CFF-4B0D-8019-7F4B934A0F60&p=184594&pn=1&searchId=7a9d75e9925e3ea8c217697d70b14364&searchtype=0 and https://www.alamy.com/stock-photo-blue-wildebeest-connochaetes-taurinus-mother-and-1-to-3-days-old-calf-125592011.html?imageid=5FC5A052-2DF2-4534-B1F8-7B839EC77DB8&p=361867&pn=1&searchId=7a9d75e9925e3ea8c217697d70b14364&searchtype=0).

Connochaetes mearnsi thus seem to qualify for a facial flag in the infantile colouration. This is extremely odd among ruminants, in which infants are usually inconspicuous.

In adults of D. jimela, the face is dark but lacks pale contrast, apart from the pale on the anterior of the ear pinnae.

In A. cokii, there is no facial flag. The darkest appearance of the front of the face falls well short of conspicuousness (https://www.inaturalist.org/observations/8655787 and https://www.inaturalist.org/observations/30264495).

To be continued in https://www.inaturalist.org/journal/milewski/77617-the-three-alcelaphin-bovids-of-the-serengeti-a-comparison-of-adaptive-colouration-part-2#...

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 05 April, 2023 19:47 by milewski milewski | 34 comments | Leave a comment

09 April, 2023

The three alcelaphin bovids of the Serengeti: a comparison of adaptive colouration, part 2

...continued from https://www.inaturalist.org/journal/milewski/77492-the-three-alcelaphin-bovids-of-the-serengeti-a-comparison-of-adaptive-colouration-part-1#

AURICULAR FLAGS

Anterior auricular flags refer to the anterior surface of the ear pinnae (usually viewed from in front of the figure), whereas posterior auricular flags refer to the posterior surface of the ear pinnae (usually viewed from behind the figure).

An alcelaphin elsewhere, namely Damaliscus pygargus phillipsi, possesses a posterior auricular flag.

However, the posterior surface of the ear pinnae is not conspicuous in any of the three species in the Serengeti.

In C. mearnsi, this surface is dark, except for its proximal ventral portion (https://www.google.com.au/search?q=Wildebeest+face+close-up&tbm=isch&sxsrf=APwXEdcOhGjX0ZFvTOQP1XppI2zteEjOfw:1680892266560&source=lnms&sa=X&ved=2ahUKEwj5qdDTs5j-AhWLplYBHUOiD6IQ_AUoAXoECAEQAw&biw=1013&bih=552&dpr=2.7#imgrc=Y_E3j3YCjT-uQM and https://focusedcollection.com/196865162/stock-photo-close-white-bearded-wildebeest-connochaetes.html). This is present already in infants (https://www.shutterstock.com/nb/image-photo/ngorongoro-crater-tanzania-africa-march-1-1961972416).
https://www.gettyimages.ie/detail/photo/lions-hunting-a-wildebeest-royalty-free-image/534975584?adppopup=true). This is precocial, being present already in jnfants (https://www.dreamstime.com/wildebeest-full-profile-another-background-wildebeest-full-profile-another-background-masai-image219783802).

In D. jimela, the surface in question has a dark tip, the extent of which is individually variable (https://www.youtube.com/watch?v=yW8XJcnl_eQ and https://www.dreamstime.com/two-topi-look-away-camera-masai-mara-two-topi-look-away-camera-showing-their-hind-quarters-oil-image219782970 and https://www.offset.com/photos/lion-panthera-leo-walking-close-to-topi-damaliscus-lunatus-masai-mara-1017957 and https://www.inaturalist.org/observations/144456049 and https://www.inaturalist.org/observations/128550886).

However, there is no dark/pale contrast or, as far as I know, sheen.

In A. cokii, the surface in question is plain fawn, similar to the ground-colour (https://www.inaturalist.org/observations/149133657).

Turning to the question of anterior auricular flags:

The anterior surface of the ear pinnae has whitish hairs in all three species, which is potentially conspicuous, depending on distance and illumination:

Connochaetes mearnsi (in which the ear pinna seems peculiarly narrow):

https://www.shutterstock.com/it/image-photo/wildebeest-closeup-white-background-2011280906 and https://www.shutterstock.com/it/image-photo/wild-wildebeest-east-africa-1170105076

Damaliscus jimela:

https://www.alamy.com/topi-portrait-damaliscus-lunatus-masai-mara-national-reserve-kenya-image333981016.html?imageid=5F01FDFD-6865-45F8-B5AB-18C665A44955&p=190655&pn=1&searchId=e4a80567726b2329ea71395d057e71cf&searchtype=0 and https://stock.adobe.com/search?k=%22topi+antelope%22&asset_id=64834158

Alcelaphus cokii:

https://www.superstock.com/asset/coke-hartebeest-head-portrait-alcelaphus-bucephalus-cokii-masai-mara-national/1566-1419938 and https://pbase.com/wimdegroot/image/103189097

In summary, the ear pinnae of the three species have definite colouration. However, the only species in which the ear pinnae are somewhat conspicuous is D. jimela, in which the whitish front-of-ear can, in certain illuminations and at certain distances, contrast with the dark of the face.

PEDAL FLAGS

Pedal flags are absent in adults of all three alcelaphin bovids of the Serengeti.

This is true notwithstanding the clear pattern in adults of D. jimela, in which the lower legs and carpals are differentiated from the upper legs (https://www.inaturalist.org/observations/148354403 and https://www.inaturalist.org/observations/139976038 and https://www.inaturalist.org/observations/139823541).

Damaliscus jimela lacks a pedal flag, because the lower legs

  • are not depigmented enough to be conspicuous in terms of pale vs dark (as opposed to hue), and
  • do not seem to be sheeny.

However, infants and juveniles of C. mearnsi have conspicuously pale lower legs, owing to a combination of depigmentation and sheen (https://www.alamy.com/stock-photo-wildebeest-with-a-new-born-calf-wildebeest-migration-serengeti-ecosystem-57497337.html?imageid=A9ED5718-341D-4433-BF05-DEF58289F8DC&p=50837&pn=1&searchId=63161ae63cf8885d338bf6e9703ed92e&searchtype=0 and https://www.pixoto.com/images-photography/animals/other/wildebeest-surviving-6657878905061376 and https://www.dreamstime.com/blue-wildebeest-newborn-calf-blue-wildebeest-connochaetes-taurinus-newborn-calf-ngorongoro-crater-national-park-tanzania-image161274444 and https://www.flickr.com/photos/147061930@N04/39727487574 and https://www.istockphoto.com/photo/baby-gnu-in-the-serengeti-national-park-gm463215041-32611182 and https://www.alamy.com/a-newborn-blue-wildebeest-brindled-gnu-connochaetes-taurinus-nursing-in-serengeti-national-park-tanzania-east-africa-africa-image374626149.html and https://www.dreamstime.com/blue-wildebeest-female-newborn-calf-blue-wildebeest-connochaetes-taurinus-female-newborn-calf-ngorongoro-crater-national-image161274456 and https://www.dreamstime.com/mother-baby-wildebeest-running-together-maasai-mara-savannah-image207464322 and https://www.dreamstime.com/mother-new-born-baby-wildebeest-walking-maasai-mara-savannah-mother-baby-wildebeest-walking-image208029498 and https://www.alamy.com/blue-wildebeest-connochaetes-taurinus-cow-and-days-old-calf-running-image62397886.html?imageid=9171F341-80CE-4163-9FE5-BD55FB97EAA4&p=94604&pn=1&searchId=7a9d75e9925e3ea8c217697d70b14364&searchtype=0).

CAUDAL FLAGS

All three alcelaphins in the Serengeti possess dark tail-tassels.

Furthermore, in A. cokii the tail-tassel is one of only two parts of the figure that are blackish (https://www.inaturalist.org/observations/27633264).

However, caudal flags are poorly-developed in all three species.

In C. mearnsi, the tail-tassel is large, and it is demonstrative in that it is swished during running, prancing and cavorting (https://www.alamy.com/stock-photo-wildebeest-migration-on-the-savannah-masai-mara-kenya-55910922.html?imageid=1AB44349-0B21-4A5A-967F-5A8EDD77A5F0&p=1163&pn=1&searchId=7a9d75e9925e3ea8c217697d70b14364&searchtype=0 and https://www.agefotostock.com/age/en/details-photo/wildebeest-brindled-gnu-connochaetes-taurinus-running-portrait-serengeti-national-park-tanzania/AAM-AAES111429 and https://www.superstock.com/asset/blue-wildebeest-connochaetus-taurinus-adult-running-serengeti-tanzania/4421-22277).w

The following show the relative sizes of the tail-tassels in A. cokii and C. mearnsi (https://www.inaturalist.org/observations/107450322 and https://www.inaturalist.org/observations/509208). The tail of C. mearnsi is perhaps the proportionately longest of any ruminant on Earth, reaching ground-level.

However, the tail of C. mearnsi

In D. jimela and A. cokii (https://www.shutterstock.com/it/image-photo/cokes-hartebeest-alcelaphus-buselaphus-cokii-kenyas-99398321), the tail-tassel is relatively small, and the tail is undemonstrative.

In D. jimela, the tail is held approximately horizontal by mature males in the courtship display (https://www.inaturalist.org/observations/143509509). Please also see comments in part 3.

In A. cokii, the tail is so slight that its blackish tassel

ABDOMINAL FLAGS

An alcelaphin elsewhere, namely Damaliscus pygargus phillipsi, possesses an abdominal flag.

A hint of this pattern can be seen in the following, of

However, all three species in the Serengeti lack abdominal flags.

BUCCAL SEMETS

A buccal semet may be present in adults of C. mearnsi, consisting of the contrast between the relatively dark mouth and the relatively pale beard (https://www.gettyimages.ie/detail/video/gnu-chews-its-cud-stock-video-footage/1173138747?adppopup=true).

This works because the beard extends right up to the mouth, offetting the movements of chewing.

A different buccal semet may possibly occur in juveniles.

The following further illustrate the colouration of the mouth in C. mearnsi (https://www.gettyimages.ie/detail/news-photo/dead-wildebeest-kenya-news-photo/143077326?adppopup=true and https://www.gettyimages.ie/detail/photo/crocodile-catching-blue-wildebeest-masai-mara-royalty-free-image/139813433?adppopup=true and https://www.gettyimages.ie/detail/photo/male-lion-portrait-feeding-on-wildebeest-carcass-royalty-free-image/1148455186?adppopup=true and https://www.alamy.com/stock-photo-lion-panthera-leo-hunting-lioness-biting-into-the-throat-of-a-gnu-15113558.html?imageid=BD1B5D91-66EC-4A96-BF1D-FE5A4C3300E0&p=53661&pn=4&searchId=66ec4ecdc5e720a4fd165f9002141568&searchtype=0).

A buccal semet is absent in D. jimela (https://www.inaturalist.org/observations/147820588 and https://www.inaturalist.org/observations/104585211 and https://www.inaturalist.org/observations/104818132).

However, A. cokii clearly possesses a buccal semet (https://www.shutterstock.com/it/image-photo/portrait-topi-this-subspecies-antelopes-found-1677593251 and https://www.shutterstock.com/it/image-photo/hartebeest-relaxing-grasslands-191758568 and https://www.dreamstime.com/stock-photo-cokes-hartebeest-masai-mara-kenya-aka-kongoni-standing-salt-lick-its-orange-eye-turned-to-camera-its-image83117372 and https://www.shutterstock.com/it/image-photo/cokes-hartebeest-serengeti-national-park-tanzania-1821801560 and https://depositphotos.com/3855301/stock-photo-closeup-portrait-of-hartebeest-antelope.html and https://www.dreamstime.com/coke-s-hartebeest-kongoni-antelope-native-to-kenya-tanzania-can-breed-lelwel-produce-hybrid-known-as-image243431831).

The following shows that, in A. cokii, the lower lips are the only part of the animal, other than the tail-tassel, with blackish pelage (https://www.shutterstock.com/it/image-photo/cokes-hartebeest-serengeti-national-park-tanzania-1821801560).

The following shows the typical situation in which the buccal semet is relevant (https://www.gettyimages.com.au/detail/news-photo/cokes-hartebeest-or-kongoni-bovidae-news-photo/492753751?adppopup=true).

The following footage, although belonging to a different species (Alcelaphus caama), shows the activation of its buccal semet (https://www.facebook.com/watch/?v=916918602674114 and https://www.youtube.com/watch?v=TcU2_qzOkqM.

ADDITIONAL PHOTOS OF ALCELAPHUS COKII (also see comment in part 3)

I have described the colouration of C. mearnsi and D. jimela, but not A. cokii, in previous Posts. The following photos further illustrate A. cokii.

https://www.alamy.com/topi-kenya-africa-image240730512.html?imageid=32B51789-67B4-4E73-B835-37608FE48038&p=788651&pn=1&searchId=2b231e9c97eacc75f20f7a32704237f7&searchtype=0https://es.123rf.com/photo_28728063_a-herd-of-coke-s-hartebeest-in-serengeti-.html

https://www.shutterstock.com/it/image-photo/young-hartebeest-approaches-mother-sunlit-savannah-1730346109

https://www.shutterstock.com/it/image-photo/closeup-cokes-hartebeest-scientific-name-connochaetes-1033695370

https://www.shutterstock.com/it/image-photo/closeup-cokes-hartebeest-scientific-name-connochaetes-773780392

https://www.agefotostock.com/age/en/details-photo/coke-hartebeest-alcelaphus-buselaphus-cokei-masai-mara-national-park-kenia/K77-229014

https://www.inaturalist.org/observations/121920320

https://www.inaturalist.org/observations/18343

https://www.inaturalist.org/observations/20041386

https://www.inaturalist.org/observations/135732653

https://www.inaturalist.org/observations/99045002

https://www.inaturalist.org/observations/18028393

https://www.inaturalist.org/observations/107943660

https://www.inaturalist.org/observations/7035195

DISCUSSION

The following shows that, in C. mearnsi, the darkness conferred by anti-sheen is conspicuous at distances ranging from 50 metres to half a kilometer (https://www.inaturalist.org/observations/151760045).

Alcelaphus cokii and D. jimela have some degree and extent of anti-sheen.

However, D. jimela - which is more intensely pigmented than A. cokii - does not emulate C. mearnsi in seeming dark at distance (https://stock.adobe.com/search?k=%22topi+antelope%22).

Part of the explanation for these differences is that C. mearnsi is migratory and extremely gregarious, whereas A. cokii is sedentary and only moderately gregarious.

The following compare the colouration of A. cokii with that of Eudorcas thomsoni nasalis - which possesses a lateral bleeze, making this gazelle unambivalently conspicuous.

The lateral pattern of E. t. nasalis qualifies as a bleeze, and not merely as a flag. This is because it

  • occupies a large proportion of the figure, and
  • is based on extremes of pigmentation/depigmentation, making it conspicuous under various illuminations.

The last photo in https://www.inaturalist.org/observations/50792870 shows that the lateral bleeze of E. t. nasalis is more conspicuous than any feature of A. cokii.

The moderate pigmentation of the rump, vs moderate depigmentation of the buttocks, in A. cokii cannot rival the boldness of the pattern in E. t. nasalis (https://www.inaturalist.org/observations/14423686).However, when the pale surfaces of A. cokii show sheen, its figure can rival that of E. t. nasalis in conspicuousness (https://www.inaturalist.org/observations/3597207).

All of the genera of alcelaphins represented in the Serengeti show great variation in colouration, depending on species/subspecies. In the case of Connochaetes, C. mearnsi is second only to Connochaetes gnou in overall conspicuousness, despite falling short of Connochaetes albojubatus in terms of a facial flag.

In the case of Damaliscus, D. jimela is not as conspicuous as Damaliscus pygargus, but more so than Damaliscus lunatus.

In the case of Alcelaphus, A. cokii is not as conspicuous as A. caama and Alcelaphus swaynei, but more so than Alcelaphus lelwel and Alcelaphus buselaphus.

To be continued in https://www.inaturalist.org/journal/milewski/77657-the-three-alcelaphin-bovids-of-the-serengeti-a-comparison-of-adaptive-colouration-part-3#...

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 09 April, 2023 11:42 by milewski milewski | 15 comments | Leave a comment

10 April, 2023

Pictures worth a thousand words, on the theme of adaptively conspicuous darkness in large mammals and birds

@matthewinabinett @zarek @paradoxornithidae @tonyrebelo @jeremygilmore @botswanabugs

The following photos inadvertently show various points about a certain theme in adaptive colouration, viz. conspicuous darkness in aid of society.

The FIRST PHOTO (https://www.gettyimages.ie/detail/photo/cheetah-is-checking-the-menu-royalty-free-image/576417193?adppopup=true) is in the open vegetation of the Serengeti ecosystem.

The species featured are the carnivore Acinonyx jubatus, the gazelle Eudorcas thomsoni nasalis, and the alcelaphin Connochaetes mearnsi.

both this gazelle and this alcelaphin have adaptively conspicuous colouration. In the case of E. t. nasalis, there is a bold pattern of banding on the torso; in the case of C. mearnsi, the whole figure is conspicuously dark, and seems to get darker with distance from the observer (https://www.gettyimages.ie/detail/photo/cheetah-hunting-wildebeest-in-masai-mara-royalty-free-image/136981303?adppopup=true).

The carnivore in this scene is, understandably, inconspicuous in its colouration (https://www.gettyimages.ie/detail/photo/young-african-cheetah-on-grass-royalty-free-image/1354142689?adppopup=true). However, it possesses several flags, which are relatively small-scale features that signal to other carnivores in certain circumstances and perspectives.

In this case, the flags in view are the auricular flag and the caudal flag of A. jubatus.

The SECOND photo (https://www.gettyimages.ie/detail/photo/lion-in-ngorongoro-crater-royalty-free-image/556269039?adppopup=true) extends the themes mentioned above.

The species featured are the carnivore Panthera leo, the bovin Syncerus caffer, the alcelaphin C. mearnsi, and the equid Equus quagga boehmi.

Syncerus caffer emulates C. mearnsi in having conspicuously dark colouration. Instead of hiding from predators, it is adapted for gregariousness.

Mature males of P. leo - the only gregarious species of felid on Earth - have partly abandoned the crypsis required for stalking prey. Instead, the mane is conspicuously dark, for social/sexual reasons.

What this means is that, in a way, here we have an example of evolutionary convergence between a carnivore and two of its main species of prey. All three species feature conspicuous darkness in adaptation to gregariousness.

The THIRD photo (https://www.gettyimages.ie/detail/photo/two-lionesses-stalking-wildebeest-hiding-in-long-royalty-free-image/200134408-001?adppopup=true) further elucidates the same themes.

The species featured are C. mearnsi and P. leo. (Incidentally, the lone tree in the distance is Balanites aegyptiaca, featuring a browse-line at about 6 m high, formed by mature males of Giraffa tippelskirchi tippelskirchi.)

Even females of P. leo feature conspicuous darkness in a limited way, by possessing an auricular flag similar to that of A. jubatus. This allows members of the group to keep track of each other in cooperative hunting.

The FOURTH photo (https://www.grida.no/resources/2523), still in the Serengeti ecosystem, extends the themes to the world's largest bird.

The species featured are C. mearnsi (in the distance), the gazelle Nanger granti granti, and Struthio camelus massaicus - which functions ecologically much like this gazelle (https://www.africabib.org/rec.php?RID=Q00023835 and https://www.projecttopics.com/journals/bibliography/is-the-diet-of-the-ostrich-similar-to-that-of-grants-gazelle/).

Nanger g. granti, like E. t. nasalis, is adaptively conspicuous by virtue of the dark/pale contrast of banding on the flanks (extended to the hindquarters).

In the case of S. c. massaicus, the group shown is of adolescents - the offspring of several parents. When at the infant and juvenile stages, S. camelus has inconspicuous colouration, comparable with that of A. jubatus. However, this turns to conspicuous darkness in adulthood, particularly in males

The FIFTH photo (https://www.dreamstime.com/beautiful-ostrich-hot-africa-nearby-antelopes-here-photo-see-large-near-image168526517) shifts the scene from the Serengeti ecosystem to Etosha National Park.

The species featured are Struthio camelus australis and the gazelle Antidorcas marsupialis hofmeyri.

In adults of S. camelus, the sexes are similar in body size (https://www.alamy.com/stock-photo-couple-of-ostriches-struthio-camelus-at-the-bontebok-national-park-38030262.html?imageid=690B1C13-38B8-499D-B4EF-C1D03840B264&p=60598&pn=4&searchId=dca6a568865628209af3d56514ac1f36&searchtype=0). However, males are so dark that they are conspicuous when viewed solitary in savanna or treeless vegetation.

As in P. leo, the benefits of masculine advertisement outweigh the benefits of hiding, for this bird.

The link to gregariousness is more subtle than in the case of the mammals shown above. This is because males of S. camelus show paternal care to an extent and degree unknown in ungulates: they help to lead and guard groups of infants and juveniles that often coalesce the offspring of other parental couples.

In the case of A. m. hofmeyri, the conspicuous pattern is basically similar to that in the gazelles shown above. As in N. g. granti, the flank-band is not black, but achieves dark/pale contrast by virtue of the white on the flanks and rump, which extends high enough to catch the sunlight.

Posted on 10 April, 2023 03:46 by milewski milewski | 2 comments | Leave a comment

The three alcelaphin bovids of the Serengeti: a comparison of adaptive colouration, part 3

@tonyrebelo @jeremygilmore @matthewinabinett @paradoxornithidae @jwidness @davidbygott @akilee @zarek @hoppy1951 @deanthompson

...continued from https://www.inaturalist.org/journal/milewski/77617-the-three-alcelaphin-bovids-of-the-serengeti-a-comparison-of-adaptive-colouration-part-2#

In my portrayal of the adaptive colouration of the alcelaphins of the Serengeti, I have pointed out the following:

all three species, in the order C. mearnsi > D. jimela > A. cokii, tend to be dark enough to stand out from the background - as opposed to blending in by means of cryptic colouration (https://en.wikipedia.org/wiki/Crypsis#).

My claim, that this darkness is enough to confer overall conspicuousness, may seem subjective.

Can we test this in some relatively objective way?

One approach is to study photos in which carnivores - which are accepted as having inconspicuous colouration - share the same illumination as their potential prey. Are the alcelaphins really more conspicuous than their predators?

Fortunately, the Web is fairly rich in such photos.

When viewing these images, please ignore the hues (https://www.yourdictionary.com/hueand https://www.color-wheel-artist.com/hue/), which may not be visible to ungulates and carnivores. Also, ignore the spotting in felids.

Instead, please assess only the overall tones, i.e. the 'shades of grey' involved (https://www.thoughtco.com/tone-definition-in-art-182471).

We would expect the carnivores to have the same tone as the background. And, according to my interpretation, we would expect the alcelaphins to be darker than the background, particularly at the ventral silhouette of the torso, which is not countershaded (https://en.wikipedia.org/wiki/Countershading).

CONNOCHAETES MEARNSI

In C. mearnsi, most of the figure, except for the rump and back, can look dark - the 'white' beard notwithstanding.

The following show that the overall tone of Acinonyx jubatus does indeed approximately match the background (https://www.gettyimages.ie/detail/photo/five-cheetahs-eating-freshly-killed-wildebeest-royalty-free-image/1156089749?adppopup=true and https://www.gettyimages.ie/detail/photo/cheetah-and-wildebeests-royalty-free-image/522055226?adppopup=true and https://www.gettyimages.ie/detail/photo/hunting-cheetah-walking-past-a-herd-of-alerted-royalty-free-image/521346806?adppopup=true and https://www.gettyimages.ie/detail/photo/five-cheetahs-eating-freshly-killed-wildebeest-royalty-free-image/1156082561?adppopup=true and https://www.gettyimages.ie/detail/photo/cheetah-checking-the-menu-royalty-free-image/577276343?adppopup=true and https://www.gettyimages.ie/detail/photo/cheetah-chasing-a-wildebeests-royalty-free-image/979884918?adppopup=true and https://www.masterfile.com/image/en/700-02659760/cheetah-in-field-with-wildebeest and https://www.masterfile.com/image/en/400-04359181/a-cheetah-acinonyx-jubatus-stalking-wildebeest-connochaetes-on).

By contrast, C. mearnsi stands out clearly from the same background in all these photos.

When the illumination is such that the figures are backlit, the shaded profile of A. jubatus looks somewhat darker than the background. However, C. mearnsi remains far darker - even if far away - than the carnivore (https://www.gettyimages.ie/detail/photo/cheetah-looking-for-hunting-family-photo-royalty-free-image/1356665838?adppopup=true and https://www.gettyimages.ie/detail/photo/hunting-cheetahs-at-wild-royalty-free-image/1283499651?adppopup=true and https://www.gettyimages.ie/detail/photo/cheetah-hunting-at-wild-royalty-free-image/1205819956?adppopup=true).

In the following (https://www.shutterstock.com/image-photo/wildebeest-chasing-cheetahs-away-when-they-1501749692), we see C. mearnsi together with A. jubatus, under identical illumination and at the same distance. (Although the carnivore is spotted, the aspect relevant here is its overall tone, relative to the background of grass.)

This, again, bears out the darkness of C. mearnsi.

A similar rationale applies to Panthera leo, as follows.

The following are complicated by the carnivore being far closer to the observer than is C. mearnsi (https://www.agefotostock.com/age/en/details-photo/lioness-hunting-wildebeest-in-the-masai-mara/M12-1240338 and https://www.gettyimages.ie/detail/photo/wildebeest-vary-of-the-lioness-who-may-hunt-in-royalty-free-image/1255573298?adppopup=true and https://www.gettyimages.ie/detail/photo/lioness-by-wildebeest-herd-royalty-free-image/200215662-001?adppopup=true and https://www.alamy.com/lioness-panthera-leo-and-antelopes-ngorongoro-conservation-area-tanzania-africa-image359929086.html?imageid=24BA2952-819B-469D-AC4E-044D73205FEA&p=1132882&pn=1&searchId=88d097a7526f5b145ff0d57d236c6e7b&searchtype=0 and https://www.alamy.com/stock-photo-masai-lion-panthera-leo-nubica-adult-female-sitting-in-grass-with-52966297.html?imageid=30242AF5-DD72-4349-B792-323BE93C5E41&p=11592&pn=3&searchId=2955e9e926053fed62c3a57c031745e6&searchtype=0 and https://www.gettyimages.com.au/detail/photo/lion-male-lion-walking-past-a-herd-of-wildebeest-royalty-free-image/1372532300?phrase=hartebeests&adppopup=true and https://www.alamy.com/stock-photo-lion-chasing-a-prey-ngorongoro-crater-tanzania-16743209.html?imageid=0A87FE46-015F-4575-AD18-8066EB8BD78A&p=58344&pn=1&searchId=c29bbb8b2d5e95260957618c6ccc9c51&searchtype=0 and https://www.agefotostock.com/age/en/details-photo/lionesses-hunts-wildebeest-in-the-masai-mara/M12-1276084/1).

However, once again the difference in tone and overall conspicuousness is obvious, between C. mearnsi and P. leo.

In the following, the complication of differing distances is eliminated, confirming the conspicuous darkness of C. mearnsi (https://www.gettyimages.ie/detail/photo/wildebeest-charging-at-hunting-lioness-masai-mara-royalty-free-image/952005364?adppopup=true and https://www.gettyimages.ie/detail/photo/lioness-chasing-wildebeest-royalty-free-image/200562141-001?adppopup=true and https://www.alamy.com/stock-photo-a-hunting-lioness-at-sunset-is-jumping-behind-her-preyserengetitanzania-16061512.html?imageid=88527EC6-A37C-44FE-9616-2BE49514F840&p=50837&pn=1&searchId=c29bbb8b2d5e95260957618c6ccc9c51&searchtype=0 and https://www.alamy.com/stock-photo-a-hunting-lioness-at-sunset-is-running-behind-her-preyserengetitanzania-16064294.html?imageid=35B8278A-59DE-4937-B213-A7B510669DCB&p=50837&pn=1&searchId=c29bbb8b2d5e95260957618c6ccc9c51&searchtype=0).

When the carnivore is darkened by shading, the difference between it and C. mearnsi is reduced (https://www.gettyimages.ie/detail/photo/lioness-hunting-eastern-white-bearded-wildebeest-royalty-free-image/103458218?adppopup=truehttps://www.gettyimages.ie/detail/photo/lioness-hunting-wildebeest-masai-mara-game-reserve-royalty-free-image/952005360?adppopup=true).

DAMALISCUS JIMELA

The darkness of the figure is more subtle in D. jimela than in C. mearnsi. It is concentrated on the face, ventral torso, and the legs just above the carpals and the hocks.

It is unusual for photos to show darkness over most of the figure (https://www.dreamstime.com/ugandan-topi-antelope-queen-elizabeth-national-park-ishasha-sector-uganda-np-image164668026 and https://www.inaturalist.org/observations/105829394). The upper half of the torso usually retains medium tone.

The following sets of photos follow the same order as explained above, except that I have mixed A. jubatus with P. leo.

Carnivore closer to observer than D. jimela:

https://www.alamy.com/female-cheetah-walking-past-topi-antelope-staring-at-her-as-she-goes-image154324074.html and https://www.bing.com/images/search?view=detailV2&ccid=C%2BQUv9TC&id=EFEB8BBEEDD02B7AFA3DCAAB877EE11C8D87F4BC&thid=OIP.C-QUv9TCI31ND8mU78ncbQHaEq&mediaurl=https%3A%2F%2Fcheetah-watch.com%2Fwp-content%2Fuploads%2F2017%2F10%2Fcheetah-topi-1.jpg&exph=378&expw=600&q=masterfile+cheetah+topi&simid=607988153515511434&form=IRPRST&ck=1E206C897F50FB691D13B8E83CE8D633&selectedindex=7&ajaxhist=0&ajaxserp=0&vt=0&sim=11 and https://es.123rf.com/photo_9171909_an-adult-cheetah-ushered-away-by-a-small-herd-of-topi-in-kenya-s-masai-mara-national-park.html and https://www.alamy.com/stock-photo-lion-panthera-leo-adult-male-hunting-topi-damaliscus-lunatus-herd-47781745.html?imageid=06F69E99-F40A-4A81-A883-0DD7A0810265&p=11592&pn=2&searchId=ab8d461b779d7157f5d6e83219cfd398&searchtype=0 and https://www.alamy.com/africa-kenya-maasai-mara-national-reserve-young-lion-walking-away-from-topi-antelopes-credit-as-bill-young-jaynes-gallery-danitadelimont-com-image441444224.html?imageid=897EC99B-F9A7-4672-B497-167F87E6292A&p=16459&pn=1&searchId=88d097a7526f5b145ff0d57d236c6e7b&searchtype=
https://www.dreamstime.com/stock-image-twelve-against-three-image18956221
https://www.dreamstime.com/stock-photo-hunter-becomes-hunted-image18956290
https://www.dreamstime.com/royalty-free-stock-photography-scat-cat-image18956217

Carnivore at same distance as D. jimela, or farther:

https://twitter.com/dhritimanimages/status/1201353418779975681 and https://www.alamy.com/stock-photo-kenya-masai-mara-a-female-cheetah-hunts-a-topi-in-the-short-grass-30746266.html and https://www.wild4photographicsafaris.com/blog/view/the-big-cats-of-the-masai-mara-february-2019/trip-reports and https://1x.com/photo/1504160/latest:all and https://www.dreamstime.com/cheetah-chasing-adult-topi-full-speed-masai-mara-kenya-male-green-plains-image187309793 and https://solent.photoshelter.com/image/I00003EgASShK_5w and scroll to 14th and 15th photos in http://marameru.org/3331-2/ and https://www.bing.com/images/search?view=detailV2&ccid=zLrPMSal&id=28E4BBB9EEB20289DA75E51CA0BAF9F5CF14EAA0&thid=OIP.zLrPMSalHttUWkSQ1BLUmQHaHa&mediaurl=https%3A%2F%2Fi.pinimg.com%2Foriginals%2Faa%2Fdc%2Fa6%2Faadca60818f07211adaacab660f3b13b.jpg&exph=1080&expw=1080&q=masterfile+cheetah+topi&simid=608023251964493221&form=IRPRST&ck=D81E7A2EF7923E0A4D1F7F8D950C7FA9&selectedindex=0&ajaxhist=0&ajaxserp=0&vt=0&sim=11 and https://www.alamy.com/thrilling-and-action-packed-images-of-two-young-cheetahs-chasing-a-topi-have-been-captured-in-masai-mara-kenya-images-captured-show-two-male-cheet-image503817454.html and https://www.bing.com/images/search?view=detailV2&ccid=Vjz5HJnX&id=B4F2D8A9C8375DECDBB6365B8F56A126F9C5FE4E&thid=OIP.Vjz5HJnXnVoq-VL5x8curwHaE8&mediaurl=https%3a%2f%2fblog.africadreamsafaris.com%2fwp-content%2fuploads%2f2010%2f08%2fcheetah_topi_battle_0004_04.jpg&exph=360&expw=540&q=masterfile+cheetah+topi&simid=608001781435034413&FORM=IRPRST&ck=64E6B8A9D05F920814035C5FAC00C263&selectedIndex=12&ajaxhist=0&ajaxserp=0 and https://www.bing.com/images/search?view=detailV2&ccid=JwSXtKxx&id=4DF1A88508E6E65314E50D0FC675DB7D3E41AE37&thid=OIP.JwSXtKxxqmc3zLzpt2TxMwAAAA&mediaurl=https%3A%2F%2Fth.bing.com%2Fth%2Fid%2FR.270497b4ac71aa6737ccbce9b764f133%3Frik%3DN65BPn3bdcYPDQ%26riu%3Dhttp%253a%252f%252fn450v.alamy.com%252f450v%252fdak0c3%252fcheetah-acinonyx-jubatus-running-past-a-topi-damaliscus-jimela-lunatus-dak0c3.jpg%26ehk%3DJ1Zlas7jfJ1ywuFsPCofeA8WqgqIIiJT3We1z%252fu%252feWA%253d%26risl%3D%26pid%3DImgRaw%26r%3D0&exph=320&expw=450&q=masterfile+cheetah+topi&simid=607989149943093715&form=IRPRST&ck=922E58C774838C60EDACFB8D3C4DEF0A&selectedindex=78&ajaxhist=0&ajaxserp=0&vt=0&sim=11

In the following direct illumination, the figure of D. jimela shows no conspicuous darkness (https://www.alamy.com/lioness-panthera-leo-hunting-and-topis-masai-mara-game-reserve-kenya-image262964121.html?imageid=B70CF3CB-EF33-4491-AC22-EE3F69A0D555&p=269351&pn=1&searchId=88d097a7526f5b145ff0d57d236c6e7b&searchtype=0). Few photos show this effect in C. mearnsi.

Overall, the above show enough darkness in D. jimela, located on the face and ventrally, to make the whole figure somewhat conspicuous at the relevant distances.

ALCELAPHUS COKII

There are few relevant photos on the Web.

However, such evidence as there is suggests that A. cokii, too, tends to be somewhat darker, overall, than A. jubatus - the pale buttocks and haunches notwithstanding.

https://www.dreamstime.com/close-up-two-cheetah-watching-hartebeest-antelope-close-up-two-cheetah-watching-hartebeest-antelope-serengeti-national-image176751187 and https://www.bing.com/images/search?view=detailV2&ccid=TN0wGtcW&id=F80062D770AFE80B037F2F156D5925DF19769918&thid=OIP.TN0wGtcW8ryh-hYvAu3HSgHaE8&mediaurl=https%3A%2F%2Fth.bing.com%2Fth%2Fid%2FR.4cdd301ad716f2bca1fa162f02edc74a%3Frik%3DGJl2Gd8lWW0VLw%26riu%3Dhttp%253a%252f%252fwww.shahrogersphotography.com%252fgallery%252fUpload%252fUpload4%252fMM08-2854.jpg%26ehk%3Dk%252fMWQ%252fWID%252bbFJejUDUwVuRgig12MYcUgwgnshWIpFeQ%253d%26risl%3D%26pid%3DImgRaw%26r%3D0&exph=427&expw=640&q=masterfile+cheetah+topi&simid=608005513759503637&form=IRPRST&ck=B71CC59F052E99ACFDE8650A426DA45A&selectedindex=152&ajaxhist=0&ajaxserp=0&vt=0&sim=11 and https://www.flickr.com/photos/wild_images/7091025929/ and https://www.gettyimages.com.au/detail/photo/cheetah-hunting-hartebeest-royalty-free-image/126279871?phrase=hartebeests&adppopup=true

The following photo nicely summarises the overall findings of this Post (https://www.alamy.com/stock-photo-lion-chasing-a-prey-ngorongoro-crater-tanzania-16741666.html?imageid=A63A1D62-49B1-4C78-9D81-1A9288554E78&p=58344&pn=1&searchId=c29bbb8b2d5e95260957618c6ccc9c51&searchtype=0).

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 10 April, 2023 06:35 by milewski milewski | 26 comments | Leave a comment

12 April, 2023

13 April, 2023

The topi of the Serengeti vs the blesbok of the Highveld: a comparison

The genus Damaliscus is represented in the Serengeti ecosystem of Tanzania and Kenya by the topi (Damaliscus jimela, https://www.inaturalist.org/observations?taxon_id=132769), and on the Highveld of South Africa by the blesbok (Damaliscus pygargus phillipsi, https://www.inaturalist.org/observations?taxon_id=129724).

Both forms are well-known, with thousands of photos on the Web. However, they have never been directly compared in the literature.

BODY SIZE AND SHAPE

The topi weighs about twice as much as the blesbok. The head is proportionately larger in the blesbok than in the topi.

HORNS

The horns of the topi are proportionately shorter than those of the blesbok. This is mainly because the former lacks the straight distal section of the latter (https://stock.adobe.com/search?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=blesbok&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=195859381)

https://www.alamy.com/stock-photo-blesbok-damaliscus-pygargus-phillipsi-grazing-at-mlilwane-wildlife-94425541.html?imageid=1DCCBA66-A144-4361-813B-D4E707694249&p=14406&pn=1&searchId=83e975b8ad7ac652d6ed41669818bca7&searchtype=0

Furthermore, only in the blesbok are the horns sexually dimorphic in colour, those of males being pale.

SEXUAL DIMORPHISM

Mature males are noticeably stockier than adult females in the blesbok. In the topi, the sexual difference is hardly noticeable.

https://stock.adobe.com/search?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=blesbok&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=916919

https://www.alamy.com/stock-photo-blesbok-damaliscus-dorcas-phililipsi-mountain-zebra-national-park-59197488.html?imageid=C70BA866-741D-49E7-9406-EF8C73152CCA&p=22059&pn=1&searchId=83e975b8ad7ac652d6ed41669818bca7&searchtype=0

COLOURATION ON THE HEAD: ADULTS

The rostrum of adults is blackish in the topi (https://www.inaturalist.org/observations/3677807), vs whitish in the blesbok.

https://www.freeimages.com/premium/topi-antelope-780234
https://www.mindenpictures.com/stock-photo-topi-damaliscus-lunatus--masai-mara-kenya-naturephotography-image00544100.html

https://www.istockphoto.com/photo/topi-antelope-in-the-savannah-gm590065986-101395729
https://www.istockphoto.com/photo/topi-antelope-gm501136375-43414418

This difference in tones applies also to the forehead. However, the marking on the forehead is broader in the topi than in the blesbok, with no constriction separating it from the marking on the rostrum (https://www.freepik.com/premium-photo/topi-antelope-masai-mara-national-park-kenya_12972508.htm and https://www.dreamstime.com/royalty-free-stock-image-topi-antelope-masai-mara-national-park-kenya-image39514446).

There is a facial bleeze in the blesbok, but the corresponding markings in the topi do not qualify as a bleeze. This is because whitish is more conspicuous than blackish.

This facial difference is so great that it makes the whole figure of adults of the blesbok conspicuous in the field (https://www.alamy.com/stock-photo-herd-of-blesbok-in-field-africa-87078020.html?imageid=86BEBDEB-C18F-4079-8D07-AFF1F8FF92C7&p=269694&pn=1&searchId=83e975b8ad7ac652d6ed41669818bca7&searchtype=0). In this sense, the blesbok is more committed/specialised, in terms of adaptive colouration, for conspicuousness to both predators and conspecifics.

A minor difference is that the whitish of the rostrum extends all the way to the rhinarium in the blesbok, whereas the corresponding blackish does not reach the rhinarium in the topi.

The posterior surface of the ear pinnae of adults tends to be conspicuous in the blesbok, but not in the topi. This is because the back-of-ear in the blesbok tends to be pale, owing partly to sheen.

Only in the topi does the distal section of the back-of-ear tend to be (inconspicuously) dark.

The presence of a posterior auricular flag in the blesbok means that the head of the blesbok is more conspicuous than that of the topi, whether viewed from the front, the side, or the rear.

The complex, subsidiary markings on the sides of the face are pale in the blesbok (https://zooinstitutes.com/animals/blesbok-berlin-zoological-garden-6020.html and https://www.istockphoto.com/photo/blesbok-gm469912880-62692804?phrase=pics%20of%20a%20blesbok), vs dark in the topi (https://www.inaturalist.org/observations/147820582 and https://www.inaturalist.org/observations/147820583).

Furthermore, these tend to appear already in juveniles in the topi (https://www.istockphoto.com/photo/closeup-of-a-beautiful-topi-antelope-gm480066601-36403576), vs only in full maturity in the blesbok.

Only in the blesbok do these subsidiary markings extend to the orbits (https://www.shutterstock.com/it/image-photo/antelope-wild-blesbok-blesbuck-lying-down-2223739221).

COLOURATION ON THE HEAD: JUVENILES

One of the greatest, and most surprising, differences is that only in the blesbok is there a distinct facial pattern of colouration in juveniles.

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

https://www.shutterstock.com/image-photo/young-blesbok-south-africa-2119574858

https://stock.adobe.com/search?k=blesbok&asset_id=545134999

https://stock.adobe.com/search?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=blesbok&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=53965073

https://stock.adobe.com/search?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=blesbok&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=200580481

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=83e975b8ad7ac652d6ed41669818bca7&searchtype=0

COLOURATION ON THE HEAD: INFANTS

In the blesbok, the whitish extends on to the cheeks (with a clear differentiation from the fawn of the rostrum, https://www.afripics.com/image/detail/a-blesbok-lamb-running) and on to the forehead. In the topi, whitish on the face is hardly noticeable (https://www.shutterstock.com/image-photo/four-adorable-baby-topi-antelope-lying-524553010).

https://www.shutterstock.com/image-photo/young-hartebees-rhino-lion-park-south-2240015263
https://stock.adobe.com/search?filters%5Bcontent_type%3Aphoto%5D=1&filters%5Bcontent_type%3Aillustration%5D=1&filters%5Bcontent_type%3Azip_vector%5D=1&filters%5Bcontent_type%3Avideo%5D=1&filters%5Bcontent_type%3Atemplate%5D=1&filters%5Bcontent_type%3A3d%5D=1&filters%5Bcontent_type%3Aaudio%5D=0&filters%5Binclude_stock_enterprise%5D=0&filters%5Bis_editorial%5D=0&filters%5Bfree_collection%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=blesbok&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=59763469
https://stock.adobe.com/search?k=blesbok&asset_id=544432933

https://www.belfasttelegraph.co.uk/entertainment/news/pictures-belfast-zoo-celebrates-birth-of-betty-bantu-the-blesbok/37149489.html

COLOURATION OF THE HINDQUARTERS

https://www.alamy.com/blesbok-damaliscus-phillipsi-damaliscus-dorcas-phillipsi-damaliscus-pygargus-phillipsi-group-in-savanna-south-africa-eastern-cape-mountain-zebra-national-park-image255390769.html?imageid=7333E975-7610-47E1-8C86-820F3594D64E&p=851122&pn=1&searchId=83e975b8ad7ac652d6ed41669818bca7&searchtype=0

TAIL

The tail-tassel is proportionately longer and laxer in the blesbok than in the topi. Furthermore, the distal part of the tassel tends to be pale only in the blesbok.

https://www.inaturalist.org/observations/32009259
https://www.inaturalist.org/observations/32620006

about 15 seconds in https://www.youtube.com/watch?v=VWM5FJCLLfs

COLOURATION OF THE TORSO

In the topi, the torso has uniform colouration (https://www.inaturalist.org/observations/15397878 and https://www.inaturalist.org/observations/141365278 and https://www.inaturalist.org/observations/110747003).

In the blesbok, it is differentiated into a dorsal section (including the withers), an intermediate section (on the flanks), and a ventral section (narrowest on the chest and broadest on the belly). These are, respectively, medium in tone, dark, and whitish (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 and https://es.123rf.com/photo_27663869_a-blesbok-antelope-damaliscus-pygargus-standing-in-grassland-south-africa.html).

COLOURATION OF THE LEGS

The main difference is that the legs of the blesbok have extensive depigmentation, whereas no part of the legs of the topi is paler than medium tone.

Furthermore, there are individually variable dark markings on the outer surfaces of the lower legs in the blesbok (https://zooinstitutes.com/animals/blesbok-zoo-plzen-19988.html and https://zooinstitutes.com/animals/blesbok-zoo-barcelona-6897.html). These are absent in the topi.

https://www.inaturalist.org/observations/149688457

GAITS

The topi trots occasionally, usually in a demonstrative way. I have seen this

  • by males during courtship, in conjunction with holding out the head and tail, and
  • by adults during defensive action against Acinonyx jubatus.

Trotting occurs occasionally in the blesbok (https://www.sciencephoto.com/media/1112128/view/blesbok-running-on-a-mountain-ridge), but it remains unknown whether the circumstances match those in the topi.

The following shows non-demonstrative trotting in the topi (https://www.inaturalist.org/observations/29316820 and https://www.inaturalist.org/observations/40344454 and https://www.inaturalist.org/observations/107687028).

POSTURES OF HEAD AND NECK

The blesbok frequently nods its head while walking, and holds the head down, with the horns forward, while standing or lying, facing the sun, in the heat of the day.

The topi only infrequently nods its head, and postures of the head in reaction to heat may occur (https://www.inaturalist.org/observations/103099619 and https://www.inaturalist.org/observations/79119693), but are hardly noticeable.

https://upload.wikimedia.org/wikipedia/commons/5/5d/Topi%2C_Maasai_Mara_%2846196374375%29.jpg

https://www.alamy.com/stock-photo-two-blesbok-damaliscus-pygargus-phillipsi-mountain-zebra-national-27089126.html?imageid=C6D7D661-8F8A-4F6B-80E2-7B00468FBCDF&p=40779&pn=1&searchId=83e975b8ad7ac652d6ed41669818bca7&searchtype=0

https://www.shutterstock.com/image-photo/baby-topi-antelope-standing-grass-serengeti-1296795187

https://pixels.com/featured/baby-topi-dorothy-nelder.html

https://www.istockphoto.com/photo/baby-topi-new-horn-is-coming-under-the-skin-gm503151635-44513508

https://www.agefotostock.com/age/en/details-photo/topi-damaliscus-lunatus-female-with-new-born-calf-massai-mara-kenya/K77-687571/1

https://www.agefotostock.com/age/en/details-photo/topis-damaliscus-korrigum-mother-and-baby-grazing-the-lush-grasslands-ishasha-sector-queen-elizabeth-national-park-uganda-africa/D88-3698849/1

https://www.agefotostock.com/age/en/details-photo/the-topi-antelope-in-the-kenyan-savanna-in-the-middle-of-the-grass-landscape/ESY-055382511/1

https://www.agefotostock.com/age/en/details-photo/topi-damaliscus-lunatus-jimela-adult-female-with-calf-standing-masai-mara-kenya/FHR-11182-00120-125/1

https://www.dreamstime.com/topi-calf-its-mom-maasai-mara-national-reserve-kenya-baby-topi-its-mom-african-savannah-image166656081

DISCUSSION

The colouration of the blesbok is more complex, and more individually variable, than that of the topi.

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 13 April, 2023 01:11 by milewski milewski | 17 comments | Leave a comment

14 April, 2023

The optically puzzling haunch-patch of the topi (Damaliscus jimela)

@botswanabugs @davidbygott @tonyrebelo @jeremygilmore @capracornelius @beartracker @tandala @minivet @matthewinabinett @simontonge

There is a feature of colouration in the topi (Damaliscus jimela) that is hard to explain in terms of either pigmentation or sheen.

I refer to the taken-for-granted 'dark' patch on each haunch of adults and juveniles.

(The haunch is the muscular surface located between buttock and flank, and between rump and upper hindleg.)

This haunch-patch of the topi

Although uniformly present, it

  • looks remarkably variable in tone, from pale to dark, and
  • does not seem to function efficiently, in terms of adaptive colouration.

In this Post, I describe the puzzle, and I offer an explanatory hypothesis.

The buttocks of the topi are relatively pale (https://www.inaturalist.org/observations/97049832). This is owing partly to depigmentation, and partly to sheen.

The ostensible function of the haunch-patch is to offset the buttocks (and rump), producing dark/pale contrast analogous to that seen in the closely-related bontebok (Damaliscus pygargus pygargus, https://www.alamy.com/stock-photo-bontebok-damaliscus-pygargus-pygarus-bontebok-national-park-south-59175893.html?imageid=190A38D1-F132-4034-A1D5-89F4685B1E7B&p=22059&pn=1&searchId=25869b8bb63848eab5bc67f94e53a679&searchtype=0).

There is no doubt that, in certain illuminations, the paleness on the buttocks of the topi is conspicuous.

Furthermore, this paleness can extend to the rump - which is not depigmented, but is sheeny in certain illuminations (https://www.inaturalist.org/observations/19669831
and https://www.inaturalist.org/observations/49694092).

A pale feature in the hindquarters is unsurprising. This is because whitish - in various patterns - occurs conspicuously on the buttocks and/or rump of many species of ungulates living gregariously in open environments (https://www.pestdetective.org.nz/image?Type=culprit&ID=142&Parent=170 and https://www.featheredphotography.com/blog/2019/10/31/an-impressive-desert-bighorn-ram/ and https://www.nps.gov/articles/pronghorn.htm and https://www.gettyimages.com.au/detail/photo/pronghorn-antelope-saskatchewan-full-length-of-deer-royalty-free-image/1370773707?phrase=blesbok&adppopup=true and https://www.wlfw.org/how-do-mule-deer-use-sagebrush/ and https://www.canadiannaturephotographer.com/january2014.html).

The problem is that, in the topi,

  • the nominally dark haunch-patch does not usually look dark enough to provide dark/pale contrast, and
  • it is unclear whether this failure is owing to insufficient pigmentation, or excessive sheen, or some other, unrecognised, optical phenomenon.

The following are typical views (https://www.inaturalist.org/observations/68110748 and https://www.inaturalist.org/observations/66387262 and https://www.inaturalist.org/observations/42292854).

These photos show that the haunch-patch is definite, but the pattern on the hindquarters does not achieve the boldness for which it seems to be designed. The haunch-patch, instead of actually looking dark, comes off as a mere shade of grey.

This 'greying' is only partly owing to depigmentation.

Sheen and gloss are types of reflection so effective that the haunch-patch can look pale when bright sunlight shines directly on to it (https://www.inaturalist.org/observations/98817844
and https://www.inaturalist.org/observations/8066259
and second photo in https://www.inaturalist.org/observations/32196975 and https://www.inaturalist.org/observations/35673621 and https://www.inaturalist.org/observations/19302393 and https://www.inaturalist.org/observations/19299734 and https://www.inaturalist.org/observations/144456049 and https://www.inaturalist.org/observations/139976038).

By the way, dear Reader, while perusing the illustrations in this Post, please continually compare the darkness of the haunch-patch with that of the upper foreleg, i.e. just above the carpal joint (https://afs.ca.uky.edu/livestock/beef/skeletal/carpal-bones).

What is consistent is that the dark on the foreleg remains far darker than that of the haunch-patch, in virtually all illuminations and perspectives (https://www.inaturalist.org/observations/32009259 and https://www.inaturalist.org/observations/145979173
and https://www.inaturalist.org/observations/30840859 and https://www.inaturalist.org/observations/27272205 and https://www.inaturalist.org/observations/32009255 and https://www.inaturalist.org/observations/41921165 and https://www.inaturalist.org/observations/76540065).

I do not know the reason for this difference, but it is probably some combination of intense pigmentation and minimal sheen on the upper foreleg.

Returning to my description of the main puzzle:

In some views, the pattern on the hindquarters is hardly noticeable (https://es.123rf.com/photo_107357682_topi-damaliscus-korrigum-single-mammal-on-grass-uganda-august-2018.html and https://www.inaturalist.org/observations/106521912 and https://www.inaturalist.org/observations/106859171), or would be hardly noticeable were it not for a reddish hue (https://www.inaturalist.org/observations/46680897) - which may not be perceptible in the visual system of ungulates and carnivores.

In many other views, the haunch-patch does look somewhat dark. However, in such cases the buttocks are usually not particularly 'lit up' by sheen - so that any dark/pale contrast remains limited (https://www.inaturalist.org/observations/29101210 and https://www.inaturalist.org/observations/8009791 and https://www.inaturalist.org/observations/154888670 and https://www.inaturalist.org/observations/62025952 and https://www.inaturalist.org/observations/56613349 and https://www.dreamstime.com/royalty-free-stock-photos-antelope-topis-damaliscus-korrigum-image22077428).

In posteriolateral views in which the buttocks and rump appear noticeably pale, the haunch-patch often fails to provide dark/pale contrast (https://www.inaturalist.org/observations/104585211 and https://www.inaturalist.org/observations/9883466).

In a few photos on the Web, it all seems to come together:
there is dark/pale contrast bold enough to make the whole figure conspicuous (https://www.inaturalist.org/observations/102025376 and https://www.inaturalist.org/observations/28289363 and https://www.inaturalist.org/observations/74563951 and https://www.gettyimages.ie/detail/photo/topi-herd-damaliscus-korrigum-on-savanna-tanzania-royalty-free-image/128139798?phrase=damaliscus%20korrigum&adppopup=true and https://www.naturepl.com/stock-photo-topi-damaliscus-korrigum-females-and-youngs-masai-mara-game-reserve-image01427626.html).

However, such views are hardly typical.

Summarising these findings in more technical terms:

In the topi (https://www.inaturalist.org/observations/35622892),

  • the ischial flag is conspicuous owing mainly owing to a pale surface, whereas the ulnar flag is conspicuous owing mainly to a dark surface, and
  • the paleness of the ischial (and pygal) surface in question is owing mainly to sheen, whereas the darkness of the ulnar surface in question is owing mainly to pigmentation.

I hypothesise that the puzzle of an indifferently greyish haunch-patch in the topi might be explained by ultraviolet, invisible to the human eye but visible to the eyes of ungulates and carnivores.

I predict that, when viewed through suitable optical equipment, the pelage of the topi will be found to have a distinct reflective pattern.

More particularly, I predict that the buttocks will prove to be reflective of ultraviolet, whereas the haunch-patch, absorbing these short wavelengths, will seem black in ultraviolet.

What this would mean, if I am right:

what our human eye sees as an indifferent pattern of 'shades of grey' - partly owing to mutually-cancelling sheen effects - is actually a vivid pattern in the eyes of the animals concerned...

perhaps even as vivid (https://www.inaturalist.org/observations/115550547 and https://www.dreamstime.com/stock-photo-bontebok-looking-stoned-medium-sized-generally-dark-brown-antelope-prominent-wide-white-blaze-its-face-image77511451) as the pattern on the hindquarters of the bontebok?

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 14 April, 2023 16:36 by milewski milewski | 15 comments | Leave a comment

18 April, 2023

How accurate was Dandelot's classical field-guide to damalisks?

@matthewinabinett @simontonge @ludwig_muller @tonyrebelo @jakob @michalsloviak @tandala @jeremygilmore

Please see top-left in https://ibs.bialowieza.pl/wp-content/uploads/2020/09/KERLEY.pdf, for the genus Damaliscus.

These are the depictions, painted in watercolour by Pierre Dandelot, in Dorst and Dandelot (1972, second edition, https://books.google.com.au/books/about/A_Field_Guide_to_the_Larger_Mammals_of_A.html?id=eKA_AAAAYAAJ&redir_esc=y and https://www.amazon.com/Field-Guide-Larger-Mammals-Africa/dp/B000RZLQGK and https://www.abebooks.com/book-search/author/DORST,-JEAN,-DANDELOT,-PIERRE and https://www.amazon.com/Field-Guide-Larger-Mammals-Africa/dp/B000RZLQGK and https://www.ebay.com/itm/154467953719and https://www.ebay.com/p/11086 and https://books.google.com.au/books/about/Larger_Mammals_of_Africa.html?id=LoVuPLfrY7UC&redir_esc=y).

After scrutinising thousands of photos of each of the species of Damaliscus on the Web, and Posting extensively in the last few weeks on this topic, I can point out the following.

DAMALISCUS HUNTERI Not applicable here because transferred to genus Beatragus.

DAMALISCUS KORRIGUM

Dandelot

  • missed the fact that the upper foreleg is consistently the darkest of the 'dark' features on the legs, haunches, and shoulders (this criticism applies also to D. lunatus and D. 'dorcas' phillipsi),
  • misportrayed the pattern of colouration in the area between eyes, forehead, and base of horns (including inconsistency between the profile and full-frontal views),
  • did not sufficiently portray the uniformity and relative darkness of the ventral part of the torso, and
  • depicted the hindquarters as too small relative to the head.

DAMALISCUS LUNATUS

(See comments above and below.)

DAMALISCUS DORCAS DORCAS (now Damaliscus pygargus pygargus)

Dandelot

  • exaggerated the size of the horns, which in reality are smaller than in phillipsi, and
  • showed the connection between the whitish on the rostrum and that on the forehead as too spindly.

DAMALISCUS DORCAS PHILLIPSI (now Damaliscus pygargus phillipsi)

Dandelot

  • missed the fact that the posterior surface of the ear usually looks paler in phillipsi than in 'dorcas',
  • overlooked that the distal part of the tail-tassel tends to be pale,
  • exaggerated the whitish feature on the ventral torso,
  • exaggerated the interruption of the whitish on the face, between rostrum and forehead, which is misleadingly described by Dorst in the accompanying verbal key as a 'dark band',
  • failed to show the relative paleness of the horns, and
  • misportrayed the white on the posterior surface of the upper foreleg as extending to the elbow (https://www.gettyimages.ca/detail/photo/walking-blesbok-antelope-royalty-free-image/92951936?adppopup=true), which is true for 'dorcas' but not for phillipsi.

By using different postures for D. korrigum and D. lunatus, Dandelot implied an obvious difference in body-conformation between the two forms, which is actually as misleading as it is helpful. In fact, the two forms are similar in body conformation except for the shape of the horns.

The converse applies to D. 'dorcas'. By choosing identical postures, Dandelot implied that the nominate form and phillipsi are more similar to each other than lunatus is to korrigum.

In reality, the converse is the case: the two forms of 'dorcas' differ in that the head is proportionately larger, and the hindquarters proportionately smaller, in phillipsi than in 'dorcas' (https://www.alamy.com/bontebok-damaliscus-pygargus-pygargus-adult-walking-de-hoop-south-africa-december-image263070028.html).

In the verbal key accompanying the illustrations, both korrigum and lunatus are described as 'purplish red'.

This 'right-brained' impression

  • is not literally correct, but
  • is food for thought about the roles of sheen and even ultraviolet, particularly at the subconscious level in the human observer.

However, more prosaically, what I find unsatisfactory is that Dandelot's illustrations are incongruent with Dorst's words: the painter's colours do not show red, let alone purple.

DISCUSSION

Dorst and Dandelot (1972) is a classic, because it pioneered a genre, and the illustrations are generally excellent.

However, in a way this book helped to mislead naturalists, by setting certain search-images for damalisks which are arguably more false than true.

More particularly, by portraying blesbok and bontebok as implicitly so similar as to be obviously conspecific, they helped to blind observers to the real differences, which are in fact great enough to warrant different species.

By the same token, by implicitly exaggerating the differences between the tsessebe and related forms, Dandelot inadvertently blinded us to the fact that the tsessebe is at least as similar to the 'korrigum' as the blesbok is to the bontebok.

Indeed, a point that remains underappreciated to this day is as follows:

Considering the vast distance between Senegal (in far-West Africa, https://en.wikipedia.org/wiki/Senegal) and South Africa, the similarity between korrigum and tsessebe is remarkable. The only ungulate that spans this range with more uniformity is Hippotragus equinus (please see illustrations in first comment below). Even in the particularly widespread species Sylvicapra grimmia, the subspecies are quite different in Senegal (https://www.facebook.com/Niokolo.Koba.Expedition/photos/niokolo-koba-camera-trap-gallerycommon-duiker-chocholatka-schov%C3%A1van%C3%A1-sylvicapra-/1675677672699819/) vs South Africa (https://www.inaturalist.org/observations/123113065).

For their part, the blesbok and the bontebok should be subject to a 'default assumption' of different species, considering that they were disjunct in distribution and different ecologically.

Another way of stating this, in part:

In the case of tsessebe and korrigum, the human observer has been misled by the horns, which tend to catch the eye disproportionately to their real biological/taxonomic significance. In the case of blesbok and bontebok, the human observer has been misled by the whitish facial bleeze, which is so bold, and so odd among ungulates, that it masks real differences.

Perhaps the best example is the horns of the bontebok. Dandelot depicts these as identical to those of the blesbok, in both his profile views and the full-frontal comparison. In fact, the horns differ as much as in the case of tsessebe and korrigum, albeit in size rather than in shape. Yet, has any Reader ever seen mention, in field guide-books, of the small size of the horns of the bontebok?

Also please see https://www.inaturalist.org/posts/54062-photos-cannot-fully-replace-paint-in-the-best-field-guide-books-for-the-larger-mammals# and https://www.inaturalist.org/journal/milewski/69637-even-pierre-dandelot-falsely-assumed-that-the-somali-wild-ass-is-a-wild-form-of-donkey#.

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 18 April, 2023 00:05 by milewski milewski | 13 comments | Leave a comment