28 de septiembre de 2022

A working approach to subspecies distinctions in the steenbok, Raphicerus campestris

@alanhorstmann @tonyrebelo @jakob @jeremygilmore @ludwig_muller @jwidness @colin25 @geichhorn @henrydelange @koosretief @michalsloviak @alexdreyer @chewitt1 @oviscanadensis_connerties @capracornelius @tandala

The subspecies of the steenbok (Raphicerus campestris, https://www.inaturalist.org/taxa/42375-Raphicerus-campestris) were revised by Groves and Grubb (2011, Ungulate Taxonomy). However, please see https://www.zoochat.com/community/threads/ungulate-taxonomy-revisited-the-evidence-for-the-splits-of-g-g.467230/page-3.

The treatment of Groves and Grubb largely follows that of Roberts A (1951, The Mammals of South Africa).

Until now, iNaturalist has avoided the problem of subspecies, by simply distinguishing the widely disjunct East African form, neumanni, from the nominate form of southern Africa.

The current approach, in iNaturalist, does not do justice to the subspecific distinctions in R. campestris. This is because

  • the East African form does not look particularly distinctive, despite its geographical disjunction,
  • the southwesternmost form, of Western Cape, is obviously distinctive despite grading continuously with other forms to the north and to the east, and
  • the form penetrating the edges of the Namib desert is so ecologically extreme that it should be assumed to belong to an arid-adapted subspecies, unless proven otherwise.

Therefore, what seems most plausible is some compromise between the current 'lumped' approach, of only two subspecies, and the old, 'split' approach in which seven subspecies are recognised, viz.

  • campestris (southwestern parts of South Africa)
  • fulvorubescens (Eastern Cape and adjacent areas)
  • natalensis (eastern parts of South Africa, as far north as Gauteng and the high-lying parts of Mpumalanga)
  • zuluensis (Zululand and the low-lying parts of Mpumalanga)
  • capricornis (Limpopo province through Zinbabwe to the Zambezi valley)
  • steinhardti (Namibia, southern Angola, northwestern South Africa, and presumably southern Angola)
  • neumanni (Kenya and Tanzania).

On the basis of photographic evidence, the main, obvious distinction is between the dark form of the southwesternmost part of South Africa, and the rest of the species-distribution. There seems no doubt that the nominate form, i.e. subspecies campestris, deserves recognition. This is true notwithstanding the uncertainty of its northern and eastern limits, where it intergrades with adjacent forms.

It also remains fair to assume that the disjunct form of East Africa, namely neumanni, is a valid subspecies. This is notwithstanding the surprising fact that, based on photos, it looks hardly different from the form in eastern South Africa.

This brings us to the arid-adapted, western form, the main distinctive feature of which, based on photos, is the extreme enlargement of the ear pinnae, at least in some individuals.

On one hand, it is possible that the western populations are merely an ecotype, as opposed to a subspecies. This is because the colouration is similar to eastern forms, apart from the usual tendency to pallor, that is so familiar in animals living in semi-deserts.

On the other hand, we should bear in mind that the western populations are globally unique, in ecological terms.

There is no ungulate, worldwide, of body mass less than 15 kg, that penetrates the edge of desert, other than R. campestris (https://www.inaturalist.org/observations/11048622).

A remarkable fact is that R. campestris lives both at the edge of the barren Namib, in Namibia, and under a mesic, equatorial climate in west-central Kenya.

So, it seems reasonable to recognise the subspecies steinhardti, the type location of which (https://en.wikipedia.org/wiki/Fransfontein) is in northwestern Namibia.

This leaves us with the mesic regions of southern Africa, from Eastern Cape through Free State and Kwazulu-Natal to Mozambique, Mpumalanga and Limpopo, and northwards through southeastern and western Zimbabwe to northeastern Botswana and southern Zambia.

According to Roberts (1951), subspecies capricornis, of western Zimbabwe, is distinctive in nearly lacking the dark, V-shaped marking on the crown, that is normal in other subspecies (https://www.inaturalist.org/observations/136478014).

In support of a subspecific distinction, it is obvious from photos that the ears are, at least in some individuals, extremely small in Kruger National Park, in Limpopo province of South Africa.

However, it is easy to show that the dark, V-shaped marking on the crown does remain, at least faintly, even in

This seems to contradict Roberts (1951).

Given the doubtful distinctions among the various eastern populations, perhaps we should choose whichever name takes chronological priority.

The choices are

  • fulvorubescens 1822, 'Caffraria', Eastern Cape
  • natalensis 1907, Drakensberg, Natal
  • zuluensis 1946, Umfolozi, now in northern Kwazulu-Natal
  • capricornis 1906, Klein Letaba, now in Kruger National Park.

There seems good reason to assume that the populations in Eastern Cape represent intergradation with the nominate subspecies.

Therefore, it resolves to a choice among the other three, and capricornis takes priority.

On this basis, I suggest that we provisionally recognise Raphicerus campestris capricornis (Thomas & Schwann, 1906).

In summary, I propose that we adopt the following subspecific names in iNaturalist:

  • campestris (Western Cape and adjacent parts of Northern Cape and Eastern Cape)
  • capricornis (northern Kwazulu-Natal, Mpumalanga, Limpopo, Gauteng, Mozambique, Zimbabwe, Zambia, easternmost Botswana, northeasternmost parts of both Namibia and Botswana)
  • steinhardti (Namibia, Angola, most of Botswana, most of Northern Cape)
  • neumanni (Kenya, Tanzania).

In all other regions, just identify to species-level, owing to the likelihood of intergradation. This includes the whole of Free State and North West (https://en.wikipedia.org/wiki/North_West_(South_African_province)), the eastern half of Eastern Cape, and eastern Botswana adjacent to Zimbabwe.

I leave readers with a few, carefully selected photos, illustrating the range of variation in the appearance of R. campestris.

The following shows how dark the nominate subspecies can be (https://www.inaturalist.org/observations/11241069). There is considerable individual variation in R. campestris, but no individual of any other subspecies is anywhere near as dark as this.

The following show the extreme variation in the size of the ear pinnae within R. campestris (https://www.shutterstock.com/image-photo/sharpes-grysbok-standing-shade-1917779507 vs http://www.rupavadodaria.com/my-first-veganniversary/).

The following show how different the conspicuousness of the ear pinnae can be in R. campestris, depending on direction of illumination and whether the pale hair-curtains are open or closed (https://www.shutterstock.com/image-photo/steenbok-spotted-namibian-desert-710362444 vs https://stock.adobe.com/search?k=steenbok&asset_id=83926648).

Ingresado el 28 de septiembre de 2022 por milewski milewski | 1 comentario | Deja un comentario

27 de septiembre de 2022

A new feature of adaptive colouration in ungulates: the tibial flag

@capracornelius @tandala @oviscanadensis_connerties @jeremygilmore @paradoxornithidae @beartracker @jacqueline_llerena @henrydelange @tonyrebelo @koosretief @justinhawthorne @ludwig_muller @happyasacupcake @marcelo_aranda @enricotosto96 @diegoalmendras @michaelweymann @jakob @jwidness @grinnin @karoopixie @davidbygott @dejong @gigilaidler @jason_van_den_berg @michalsloviak

Please see https://www.inaturalist.org/journal/milewski/70293-the-bambis-part-9-bleezes-flags-and-semets-in-the-bovid-genus-raphicerus#.

INTRODUCTION

Dear reader, here is a glimpse deep into the secret world of intraspecific communication in two
species of bambis.

Members of the antilopin genus Raphicerus are not gregarious. However, they tend to be monogamous.

Furthermore, adult females consort with their offspring, at least until weaning.

Therefore, there is frequent contact among individuals in the 'societies' of Raphicerus, despite the impression that these animals are 'solitary'.

Because bambis are small-bodied enough to hide for most of the time, their intraspecific communications tend to be secretive.

One way to monitor each other's whereabouts, as they forage in the mornings and evenings, is to 'flash' parts of the body that are small and low enough not to be noticed by scanning predators, but pale/bright enough to be conspicuous at fairly close range, at least when moved.

And this brings us to something that zoologists and naturalists may have overlooked.

It seems possible that grysboks (Raphicerus melanotis and Raphicerus sharpei) mediate such social monitoring, at least in part, by means of a certain part of the body that nobody has paid attention to: the inner surface of the hindleg, just above the hock (https://en.wikipedia.org/wiki/Hock_(anatomy)).

The pelage of the inner surface of the upper hindleg is oddly pale in these species.

Raphicerus melanotis:

http://cameratrap.mywild.co.za/p/cape-grysbok.html

https://www.inaturalist.org/observations/9522907

https://www.inaturalist.org/observations/26439871

https://www.inaturalist.org/observations/102342423

Raphicerus sharpei:

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=steenbok&order=relevance&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=478595701

https://stock.adobe.com/search?k=grysbok&asset_id=466446249

By comparison, this same surface is not anomalously pale in the third member of the same genus, namely Raphicerus campestris.

The following show subspecies campestris of R. campestris, which coexists with R. melanotis but prefers more open vegetation (also see comment below for many more illustrations):

https://www.inaturalist.org/observations/107377965

https://www.inaturalist.org/observations/106332311

https://www.inaturalist.org/observations/50746594

https://www.inaturalist.org/observations/129193891

https://www.inaturalist.org/observations/122610678

https://www.alamy.com/stock-photo-steenbok-raphicerus-campestris-walking-in-shrubbery-south-africa-western-76154029.html?imageid=D54D52A6-FFDA-4FBE-9283-9390D08886ED&p=1142662&pn=1&searchId=b33750fe1700c0af1e7d56e14ee9b7da&searchtype=0https://es.123rf.com/photo_171698571_alert-steenbok-carnero-capturado-temprano-en-la-ma%C3%B1ana-en-el-parque-nacional-karoo-cabo-occidental.html?vti=n84f9ofebt93ncyyzk-1-81

The following shows that, in some individuals of R. campestris campestris, there is white on the inner, upper surface of the hindleg, but this does not extend to the vicinity of the hock: https://www.inaturalist.org/observations/60722940.

COINING A NEW TERM: 'TIBIAL FLAG

In the context of adaptive colouration, a flag is defined as a relatively small-scale pattern that becomes conspicuous, at the scale of the whole figure, when activated by movement.

A typical location for flags, in ungulates, is the hindquarters, particularly the tail. And the functions of caudal flags include social and sexual signalling, and the announcement of anti-predator alarm to conspecifics, or the potential predators, or both.

What has been previously overlooked is that, in certain secretive species of ruminants with small tails, the location of flags on the posterior of the figure may have been shifted from the tail to another, more subtle and intriguing, location, namely the hind leg above the hock.

By far the most obvious candidate for a tibial flag is Alces alces (https://www.inaturalist.org/taxa/522193-Alces-alces).

In this large-bodied cervid, the tibial flag covers both the inner and the outer surfaces of the hindleg above the hock. It is individually and seasonally variable, and also depends on illumination.

ILLUSTRATIONS OF TIBIAL FLAG IN ALCES ALCES

https://www.inaturalist.org/observations/135414451

https://www.inaturalist.org/observations/115470987

https://www.inaturalist.org/observations/125843310

https://www.inaturalist.org/observations/121343112

https://www.inaturalist.org/observations/120257251

https://www.inaturalist.org/observations/129646111

https://www.inaturalist.org/observations/119626107

https://www.inaturalist.org/observations/119092478

https://www.inaturalist.org/observations/116521066

https://www.inaturalist.org/observations/134851345

https://www.inaturalist.org/observations/116789745

https://www.inaturalist.org/observations/135324468

https://www.alamy.com/stock-photo-moose-from-behind-142718462.html

https://www.inaturalist.org/observations/131879614

https://www.inaturalist.org/observations/126552983

https://www.inaturalist.org/observations/125993345

Why A. alces is unusual, in possessing a tibial flag, is worthy of further investigation.

However, for now let us return to our bambis, in which any tibial flag is far more subtle.

THINKING LATERALLY IN THE CASE OF RAPHICERUS

In Raphicerus, certain species/subspecies have more countershading (https://en.wikipedia.org/wiki/Countershading) than others.

This countershading is by definition located on the ventral parts of the figure, and the inner surfaces of the upper limbs.

However, on closer examination, there is a significant anomaly.

Countershading - which, by definition, works best when a bright sun is high in the sky- is best-developed in tropical and subtropical subspecies of Raphicerus campestris. It is least-developed in Raphicerus melanotis, which is restricted to the temperate zone

On this basis, one would expect the inner surface of the upper hind leg to be pale in R. campestris, vs not pale in R. melanotis.

However, in reality it is the opposite that is true. Raphicerus melanotis has a pale inner surface on the upper hindleg, whereas R. campestris tends not to have this.

Please scroll to the 11th photo in https://www.africawild-forum.com/viewtopic.php?t=527&start=20 for a particularly clear view of the tibial flag in Raphicerus sharpei.

The tibial flag in R. melanotis and R. sharpei is presumably activated when the animal walks, and should be particularly visible in the oblique light of evenings and early mornings - when much of the foraging takes place.

The paleness, in R. melanotis, of the inner surface of the hind leg, is puzzling if interpreted simply from the viewpoint of countershaing in aid of crypsis. This is because this part of the anatomy

  • is paler than the ventral surface of the torso, despite the fact that it
  • is not normally visible enough, in the standing figure, to need disguising.

I therefore tentatively suggest that this pale feature functions as a flag, during walking/asymmetrical standing in suitable illumination.

This tibial flag, I hypothesise, aids social monitoring by means of a signal low-profile enough to remain congruous with the furtive habits and overall inconspicuousness of the species concerned.

A similar rationale may possibly apply to an even smaller area of anomalously pale pelage in R. sharpei, which likewise transgresses countershading. This is located on the front surface where the foreleg joins the torso.

The anterior feature can perhaps be called an 'anterior axillary flag'.

https://es.123rf.com/photo_110620408_sharpe-grysbok-in-kruger-national-park-south-africa-specie-raphicerus-sharpei-family-of-bovidae.html

https://www.alamy.com/stock-image-sharpes-grysbok-raphicerus-sharpei-male-adult-south-africa-mpumalanga-161763316.html?imageid=6332CFDE-0830-42B2-8ED6-8113A09A06AE&p=546796&pn=1&searchId=bb39c60edd2f811fc9c03d99a5112e0b&searchtype=0

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=steenbok&order=relevance&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=478595701)

Ingresado el 27 de septiembre de 2022 por milewski milewski | 13 comentarios | Deja un comentario

25 de septiembre de 2022

One of the few records of stotting in hippotragin bovids

@beartracker

Estes (1991), on page 116 of The Behavior Guide to African Mammals, states the following under the heading 'Postures and Locomotion' for the tribe Hippotragini (https://en.wikipedia.org/wiki/Grazing_antelope) of the family Bovidae:

"The trot is not a regular gait in this tribe but may appear as a transition between walk and gallop, and a STYLE-TROT is performed in situations of excitement or alarm. Oryxes have a particularly beautiful flowing trot with a suspension stage during which all feet are off the ground and the head is turned synchronously from side to side (Kingdon 1982). Trotting scimitar-horned oryxes hold their chins raised with horns back (Hugh 1980)."

What this means is that, in hippotragins, stotting (https://en.wikipedia.org/wiki/Stotting) takes the form of style-trotting.

In my experience, photos or videos capturing this form of anti-predator display are rare, even in the case of infants and juveniles in play.

Therefore, finding the following depiction today, I am posting it immediately, before it vanishes from the Web.

Please scroll to 24th photo in http://teamwindchase.com/Africa-2019-11.htm for style-trotting, a form of stotting, in Oryx gazella.

The following (https://www.youtube.com/watch?v=QL_OzqtuNxo) briefly shows trotting by an individual infant of Oryx dammah.

Ingresado el 25 de septiembre de 2022 por milewski milewski | 1 comentario | Deja un comentario

The bambis, part 9: bleezes, flags, and semets in the bovid genus Raphicerus

...continued from https://www.inaturalist.org/journal/milewski/70250-the-bambis-part-8-adaptive-colouration-in-grysboks-raphicerus-melanotis-and-raphicerus-sharpei#

Also see https://www.inaturalist.org/journal/milewski/70368-a-new-feature-of-adaptive-colouration-in-ungulates-the-tibial-flag#

Dear reader, please toggle between the two photos in https://www.inaturalist.org/observations/59156961. What do you notice, and what do you think the display means?

Now examine the following, which nicely shows the anti-predator context in which this display is deployed.

Are these individuals displaying their white buttocks to each other (as per the textbooks) or to the potential predator (in this case, the photographer, Tony Rebelo)?

The following is my interpretation of all of the various conspicuous features of colouration in the three spp. of Raphicerus (https://www.inaturalist.org/observations?place_id=any&taxon_id=42373&view=species).

BLEEZES (patterns of dark/pale colouration so conspicuous that they are obvious even when the figure is stationary, and even at a distance):

These are absent from all three spp. of Raphicerus (in contrast to e.g. Ourebia ourebi ourebi, https://www.inaturalist.org/journal/milewski/69937-adaptive-colouration-in-the-oribi-southern-forms-are-more-conspicuous-than-northern-forms#).

FLAGS (patterns of dark/pale colouration of moderate size, which become conspicuous only when activated by movement, of either a body part or the whole figure):

Auricular flags:

These are absent from all three spp. of Raphicerus (in contrast to e.g. Oreotragus saltatrixoides, https://www.inaturalist.org/journal/milewski/57595-the-bambis-part-4-a-new-species-of-klipspringer-in-southern-africa#).

Buttock flags:

A buttock flag is present in Raphicerus campestris, but absent from the other two spp.

The following show the buttock flag not activated:

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=526322906

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=516776123

https://stock.adobe.com/ro/search?k=steenbok&asset_id=96029539

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=6&search_type=pagination&get_facets=0&asset_id=234422799

https://www.gettyimages.in/detail/photo/escaping-little-antelope-royalty-free-image/590583929?adppopup=true

scroll to 6th photo in http://visitcradock.co.za/mountain-zebra-national-park-cradock/#lightbox/5/

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&search_page=2&get_facets=0&search_type=pagination&asset_id=441156073

https://stock.adobe.com/ro/search?k=steenbok&asset_id=51231777

https://stock.adobe.com/ro/search?k=steenbok&asset_id=103481637

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=121268962

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=7&search_type=pagination&get_facets=0&asset_id=75206813

https://www.shutterstock.com/image-photo/close-photo-small-buck-called-steenbok-2008884197

https://www.shutterstock.com/image-photo/steenbok-standing-alert-kruger-national-park-1953181489

https://stock.adobe.com/ro/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_collectn%5D=0&filters%5Bcontent_type%3Aimage%5D=1&k=steenbok&order=relevance&safe_search=1&limit=100&search_page=6&search_type=pagination&get_facets=0&asset_id=426829025

The following show the buttock flag activated, while the figure is stationary in mild/initial alarm:

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=6&search_type=pagination&get_facets=0&asset_id=180230559

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=7&search_type=pagination&get_facets=0&asset_id=180230715

https://stock.adobe.com/ro/search?k=steenbok&asset_id=7826589

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&search_page=2&get_facets=0&search_type=pagination&asset_id=441230341

https://stock.adobe.com/ro/search?k=steenbok&asset_id=404356409

https://southafrica.co.za/how-to-identify-steenbok.html

https://stock.adobe.com/ro/search?k=steenbok&asset_id=526997849

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&search_page=2&get_facets=0&search_type=pagination&asset_id=322753486

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=6&search_type=pagination&get_facets=0&asset_id=186548226

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=7&search_type=pagination&get_facets=0&asset_id=239510784

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=8&search_type=pagination&get_facets=0&asset_id=240700963

https://www.shutterstock.com/image-photo/cute-steenbok-on-alert-front-tree-1890922669

https://www.shutterstock.com/image-photo/steenbok-aphicerus-campestris-smallest-antelope-southern-1214048647

https://www.shutterstock.com/image-photo/steenbok-bush-south-africa-1302941758

https://www.inaturalist.org/observations/85907385)

The following show the buttock flag activated, while fleeing:

https://www.inaturalist.org/observations/115766655

https://www.inaturalist.org/observations/13490802

https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=4&search_type=pagination&get_facets=0&asset_id=466446514

https://www.cimicorp.com/DI/Collection29/slides/Africa_20081101_103818_926_2X.html

https://www.shutterstock.com/image-photo/steenbuck-raphicerus-campestris-running-over-dirt-1126962635

https://www.inaturalist.org/observations/111775121

https://www.inaturalist.org/observations/71315273)

https://www.inaturalist.org/observations/73647662

Tibial flags:

Please see https://www.inaturalist.org/journal/milewski/70368-a-new-feature-of-adaptive-colouration-in-ungulates-the-tibial-flag#.

Pedal flags:

A pedal flag is present in some subspecies/individuals of Raphicerus sharpei (see https://www.inaturalist.org/journal/milewski/70250-the-bambis-part-8-adaptive-colouration-in-grysboks-raphicerus-melanotis-and-raphicerus-sharpei#)

It is possibly also present in some individuals of R. campestris: https://www.shutterstock.com/image-photo/sreenbok-antelope-kruger-national-park-south-47160058 and https://www.shutterstock.com/image-photo/steenbuck-622472594

Caudal flags:

These are absent from all three spp., the tails of which are small and plain-coloured.

SEMETS (patterns of relatively dark/relatively pale colouration of small size, conspicuous only at close range, and only when activated by movement of the body part concerned)

Auricular semets (see e.g. https://www.inaturalist.org/journal/milewski/55694-ten-best-illustrations-of-auricular-semets-in-deer#):

These are absent from all three spp.

Buccal semets:

A buccal semet is possibly present in all three spp., consisting of

  • the darkness of the rhinarium, the rostrum adjacent to the rhinarium, and the bare edge of the lower lip, vs
  • the paleness of the pelage of the lips and, to various extents, the sides of the mandibles.

This buccal semet is, in human eyes, clearest in Raphicerus campestris:

https://www.shutterstock.com/image-photo/steenbok-aka-steinbuck-steinbok-male-140509621

https://www.alamy.com/steenbok-raphicerus-campestris-young-male-portrait-south-africa-mpumalanga-kruger-national-park-image345028232.html?imageid=7C5917E7-A9ED-4B1B-B500-0DB8D4366C4B&p=853442&pn=1&searchId=18a1c61216ed6fd2c4b1d370fb8cd884&searchtype=0

https://www.alamy.com/steenbok-raphicerus-campestris-male-portrait-south-africa-mpumalanga-kruger-national-park-image345028364.html?imageid=DFDD0021-A370-4B2C-9C81-EB338FDB72D7&p=853442&pn=1&searchId=18a1c61216ed6fd2c4b1d370fb8cd884&searchtype=0

https://www.shutterstock.com/image-photo/steenbok-aka-steinbuck-steinbok-female-140509576 and https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=396572018

https://www.shutterstock.com/image-photo/steenbok-raphicerus-campestris-relaxed-resting-lying-785515177

https://www.inaturalist.org/observations/90699392

It is least clear in Raphicerus melanotis:

see https://www.inaturalist.org/journal/milewski/70250-the-bambis-part-8-adaptive-colouration-in-grysboks-raphicerus-melanotis-and-raphicerus-sharpei#.

DISCUSSION

The following is typical of the social setting in which the buccal semet hypothetically functions: https://www.shutterstock.com/image-photo/steenbok-raphicerus-campestris-relaxed-resting-lying-785515171.

Pedal flags are poorly-developed in all spp. of Raphicerus, in contrast to certain coexisting species/subspecies such as Sylvicapra grimmia caffra (https://stock.adobe.com/ro/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=steenbok&order=relevance&safe_search=1&limit=100&search_page=5&search_type=pagination&get_facets=0&asset_id=362016670).

The main feature of adaptively conspicuous colouration in Raphicerus is the buttock flag of R. campestris (https://www.inaturalist.org/observations/126223294).

However, even this feature is subtle, in keeping with the emphasis on hiding from predators, wherever possible, in these diminutive ruminants.

This buttock flag is phylogenetically related to bleezes on the buttocks of gazelles (e.g. Nanger granti, https://upload.wikimedia.org/wikipedia/commons/c/cb/Nanger_granti.jpg). In both Gazella and R. campestris, the pelage on the buttocks can be flared by piloerection, to enhance conspicuousness.

However, the buttock flag of R. campestris differs in at least three ways from those of gazelles, viz.

The following show the shift in the shape of the back, from

The following show the boosting in the conspicuousness of the white of the buttocks as the posture changes from unalarmed (https://www.shutterstock.com/image-photo/steenbok-aka-steinbuck-steinbok-male-140509591) to mildly/initially alarmed (https://www.inaturalist.org/observations/132963728 and https://www.shutterstock.com/image-photo/steenbok-standing-frozen-scared-13160773 and https://www.inaturalist.org/observations/118911269).

The following suggests that, as long as the hindquarters remain hunched, the buttock flag can hardly be displayed: https://www.shutterstock.com/image-photo/small-antelope-called-steenbok-enjoying-spring-42206143. What is needed is at least the posture shown in: https://www.shutterstock.com/image-photo/steenbok-raphicerus-campestris-kalahari-injury-on-80500765.

Ingresado el 25 de septiembre de 2022 por milewski milewski | 22 comentarios | Deja un comentario

23 de septiembre de 2022

The bambis, part 8: adaptive colouration in grysboks, Raphicerus melanotis and Raphicerus sharpei

@capracornelius @tandala @oviscanadensis_connerties @jeremygilmore @paradoxornithidae @beartracker @jacqueline_llerena @henrydelange @tonyrebelo @koosretief @justinhawthorne @ludwig_muller @happyasacupcake @marcelo_aranda @enricotosto96 @diegoalmendras @michaelweymann @fionahellmann

...continued from https://www.inaturalist.org/journal/milewski/58139-the-bambis-part-7-why-do-certain-genera-show-tropical-hues#

Grysboks (Raphicerus melanotis https://es.123rf.com/photo_39925015_a-rare-cape-grysbok-antelope-raphicerus-melanotis-south-africa.html and https://www.inaturalist.org/observations/72612861) and Raphicerus sharpei (https://www.shutterstock.com/image-photo/sharpes-grysbok-antelope-794728726 and https://www.alamy.com/stock-photo-sharpes-grysbok-31791328.html?imageid=8258088A-BE1C-47D2-B568-B4E03D47F25D&p=34420&pn=1&searchId=bb39c60edd2f811fc9c03d99a5112e0b&searchtype=0 and https://www.shutterstock.com/image-photo/sharpes-grysbok-hiding-thick-green-undergrowth-2178590039) occur in the southern and southeastern parts of Africa.

Among all the ungulates of the world, these are among the best examples of thoroughly inconspicuous colouration, of a cryptic type (https://en.wikipedia.org/wiki/Crypsis).

Grysboks are nocturnal and non-gregarious, and depend on shrubby vegetation for cover.

This means that the colouration is so plain and featureless that the figures blend extremely well into the environment (https://www.inaturalist.org/observations/11178739 and https://www.inaturalist.org/observations/48569125 and https://commons.wikimedia.org/wiki/File:Sharpe%27s_Grysbok.jpg and https://www.shutterstock.com/image-photo/sharps-grysbok-kruger-1083039092).

Even more so, when one considers that any differentiation in hues (rufous ground-colour vs grey on the posterior surface of the ears, https://www.inaturalist.org/observations/68999756) are probably invisible in the eyes of the relevant animals (i.e. grysboks themselves, and the Carnivora that are their main predators).

On one hand, this seems to make grysboks the simplest - and least interesting - of ungulates for further investigation, in terms of adaptive colouration.

However, I take a more curious approach.

What the simplicity of the colouration of grysboks means is that we have an opportunity to clarify any small-scale features that do not conform to the overall plainness.

These anomalous features (*asterisk indicates individual variation) are

BODY

Many species of mammals have grizzled/speckled pelage, in which each hair is graduated in colour from the base to the tip (https://en.wikipedia.org/wiki/Fur#/media/File:Down_Awn_and_guard_hairs_of_cat_2012_11_13_9203r.JPG).

However, in grysboks the form of grizzing is, as far as I know, unique among ruminants. This is because each hair is homogeneous in colour, but a minor percentage of the hairs are whitish.

Countershading (https://en.wikipedia.org/wiki/Countershading) is better-developed in R. sharpei than in R. melanotis. This is unsurprising, based on similar latitudinal patterns in various other ruminants (https://www.inaturalist.org/journal/milewski/53696-a-succinct-photo-guide-to-subspecies-of-the-bush-duiker#).

FACE, HEAD and EARS

The face of grysboks is not plain-coloured. One of the best illustrations of the pattern can be found by scrolling in https://www.edwardselfephotosafaris.com/newsp27.html.

All ruminants with a bare rhinarium have the nose dark-pigmented. However, the following of Cephalophus shows that the colouration of the face can otherwise be plain in small-bodied ruminants: https://www.dreamstime.com/stock-photo-duiker-close-up-detail-small-west-african-antelope-image75691614.

My interpretation is as follows:

The various markings on the face have dual functions at different scales.

When viewed from some distance, they amount collectively to a form of disruptive colouration, 'camouflaging' the head by disrupting its shape.

However, the same markings can also function, at close range, for social communication, e.g. aiding individual recognition.

Grysboks differ from their congener, Raphicerus campestris, in that the whitish pelage adjacent to the eye (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=steenbok&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=333179556) has been eclipsed.

I suspect that this has occurred not by means of any darkening of the hairs, but rather by a thinning of the pelage, exposing the blackish skin (https://www.redbubble.com/people/mags/works/7400304-the-tiny-shy-scarce-sharpe-s-grysbok-raphicerus-sharpei-kruger-national-park).

The ear pinna is large in all spp. of Raphicerus, probably for thermoregulation as much as hearing.

However, it is puzzling that the hair-curtains, which open and close ostensibly in reaction to temperature, are not a brownish colour, which would make the front-of-ear inconspicuously plain.

Instead, the hair-curtains are pale enough to be conspicuous at distances potentially relevant to scanning predators (https://www.inaturalist.org/observations/21208569 and https://www.inaturalist.org/observations/7026104).

This puzzle deserves further thought, as does the individually variable paleness on the front of the neck.

The following show the pale hair-curtains on front-of-ear

The paleness of the lower lip and chin is poorly explained by countershading.

I interpret the colouration around the mouth in both spp. to be a buccal semet (https://www.inaturalist.org/observations/11263147 and https://www.alamy.com/sharpes-grysbok-raphicerus-sharpei-south-africa-mpumalanga-kruger-national-park-image255383147.html?imageid=B2DB3495-B84D-45B8-93F0-CADC61B7296C&p=853443&pn=1&searchId=bb39c60edd2f811fc9c03d99a5112e0b&searchtype=0 and https://www.alamy.com/stock-photo-portrait-of-sharpes-grysbok-raphicerus-sharpei-in-the-bush-the-photo-33096574.html?imageid=097746CA-48F5-40A6-8578-BFE7EBA82631&p=60598&pn=1&searchId=bb39c60edd2f811fc9c03d99a5112e0b&searchtype=0). Please note, in the following view (https://www.inaturalist.org/observations/13582069), that the lower lip and adjacent pelage is the only part of the figure that is whitish.

This small-scale pattern may possibly be more conspicuous in ultraviolet than in the range of wavelengths visible in human eyes.

FEET

The following is possibly the most unexpected of my findings in this Post.

Raphicerus sharpei, in at least some individuals, has anomalously pale feet, which possibly function as a pedal flag. I have, as yet, no explanation for why there is no such feature in either R. melanotis or R. campestris.

However, R. sharpei also happens to differ from R. melanotis in

So, what emerges is that one of the main differences between the two spp. of grysboks is in the feet, including their anatomy, colouration, and action in producing an audial and possibly visual signal in an anti-predator context.

to be continued in https://www.inaturalist.org/journal/milewski/70293-the-bambis-part-9-bleezes-flags-and-semets-in-the-bovid-genus-raphicerus#...

Ingresado el 23 de septiembre de 2022 por milewski milewski | 18 comentarios | Deja un comentario

20 de septiembre de 2022

Subtle diversification of buccal semets in tragelaphin antelopes, part 2

...continued from https://www.inaturalist.org/journal/milewski/70123-buccal-semets-in-tragelaphins-from-elands-to-bushbucks-part-1#

DISCUSSION

It is possible that there is an ultraviolet component, hardly visible in human eyes, in the semets of tragelaphins. However, I limit the following discussion to the patterns visible to us in the photos presented.

The buccal semet of males of Strepsiceros strepsiceros is among the most conspicuous in this study (https://www.inaturalist.org/observations/67301987). This suggests an ability, in this species, for male individuals to monitor each other when lying under the scattered woody plants in its semi-arid habitat.

It is tempting to assume that the small-scale patterns on the heads of tragelaphins represent a kind of ancestral pattern, shared in common among genera.

However, this study dispels this notion. In fact, each genus and species (except for the two spp. of bushbuck) has its own pattern, suggesting some sort of adaptive radiation.

Ingresado el 20 de septiembre de 2022 por milewski milewski | 2 comentarios | Deja un comentario

19 de septiembre de 2022

Subtle diversification of buccal semets in tragelaphin antelopes, part 1

A buccal semet is a pattern of colouration, around the mouth, that makes the motion of chewing more conspicuous than it would be without such colouration.

Buccal semets occur typically in cud-chewing ungulates (ruminants), which do most of their chewing while resting in small groups.

These patterns are likely to be biologically significant, for at least two reasons.

Firstly, they exemplify a subtle and previously overlooked form of adaptive colouration.

The hypothetical function is to facilitate social communication in the context of anti-predator vigilance. The displaying of the semet, by means of the action of chewing, would be inadvertently reassuring to group-members, as they ruminate drowsily, in sight of each other.

Secondly, buccal semets may reveal phylogenetic relationships. They potentially inform our taxonomic classification of the clades involved.

In this series of Posts, I document for the first time the colouration around the mouth in the various genera and species of tragelaphins (https://en.wikipedia.org/wiki/Tragelaphini).

The following compilation of photos illustrates the relevant patterns in all five genera of tragelaphins.

The anatomical structures on which to focus are

  • chin and lower lip (which has a bare edge),
  • upper lip (the bare edge of which is hardly visible),
  • gape (corner of the mouth, where the mouth abuts the cheek),
  • mandible, i.e. the lower jaw, posterior to the mouth, and
  • any beard/dewlap on the ventral surface of the mandibles.

Please observe the darkness/paleness of these structures, relative to each other, the rhinarium, and the cheek.

Please note the species-specific patterns, their individual variation, and any differences among sexes and adults/juveniles.

TAUROTRAGUS ORYX

The buccal colouration is more individually variable in its degree of development than in any other tragelaphin, owing to a pallid (depigmented) tendency.

However, the basic pattern (https://www.alamy.com/stock-photo-eland-taurotragus-oryx-de-hoop-nature-reserve-western-cape-south-africa-48782311.html?imageid=FD24B2C5-426E-4D92-A6CD-DE795DC987CC&p=165079&pn=1&searchId=794c737373580976e28d0483d22ce443&searchtype=0) is one of consistently whitish chin and lips. Some individuals, of both sexes, have dark emphasis immediately posterior to the whitish, at about the longitude of the gape.

https://stock.adobe.com/search?k=%22giant+eland%22&asset_id=338886526

https://www.alamy.com/common-eland-taurotragus-oryx-image432757293.html?imageid=6229F140-EA07-4A0C-A074-3CB65A3B8FE1&p=1427920&pn=1&searchId=794c737373580976e28d0483d22ce443&searchtype=0

https://www.alamy.com/stock-photo-eland-antelope-fighting-86624002.html?imageid=1C0C6FEE-A691-4512-B0D9-DC6CFBAC6174&p=1388030&pn=1&searchId=794c737373580976e28d0483d22ce443&searchtype=0

https://www.dreamstime.com/portrait-view-eland-tragelaphus-oryx-resting-lush-green-field-largest-african-antelopes-have-flap-image227721377

https://www.dreamstime.com/eland-antelope-taurotragus-oryx-eland-antelope-ist-crossing-namibian-kalahari-image223419329

https://www.dreamstime.com/eland-antelope-lying-grass-its-head-up-ndutu-tanzania-image198684795

https://www.dreamstime.com/eland-antelope-portrait-portrait-large-male-eland-antelope-tragelaphus-oryx-south-africa-image101845662

https://www.dreamstime.com/stock-photo-giant-eland-african-safari-traveling-around-mauritius-image97675463

https://www.dreamstime.com/common-eland-taurotragus-oryx-largest-african-antelope-species-common-eland-taurotragus-oryx-largest-image188527850

https://www.alamy.com/detail-shot-of-common-eland-taurotragus-oryx-on-a-grassy-ground-savannah-and-plains-antelope-found-in-east-and-southern-africa-image435112444.html?imageid=312E8A71-69A7-46DA-A5D1-3EA768725EA0&p=1397101&pn=1&searchId=794c737373580976e28d0483d22ce443&searchtype=0

https://www.alamy.com/close-up-portrait-of-common-eland-taurotragus-oryx-with-head-turned-facing-right-kenya-image369435143.html?imageid=AF9F0FCF-36AE-4654-B67A-D0DCF9C4EF97&p=1424712&pn=1&searchId=794c737373580976e28d0483d22ce443&searchtype=0

https://www.alamy.com/close-up-view-of-large-male-eland-detail-with-face-turned-to-viewer-image60176386.html?imageid=0606281F-623D-442D-BC19-A29F94659E07&p=163101&pn=1&searchId=794c737373580976e28d0483d22ce443&searchtype=0

https://www.shutterstock.com/image-photo/southern-eland-antelope-side-view-portrait-1147821335

For additional illustrations see https://www.inaturalist.org/journal/milewski/70101-adaptive-colouration-of-northwestern-oribi-ourebia-montana-quadriscopa-part-2-buccal-semet#.

TAUROTRAGUS DERBIANUS

The buccal colouration is similar to, but better-defined than, that in Taurotragus oryx.

In addition, there is a dewlap, bearded in adolescents, that arises on the mandible. The dewlap, with or without any beard, provides a dark feature that would further accentuate the chewing movement of the mandible. Too few photos are available..

https://www.zoochat.com/community/media/eastern-giant-eland.395398/

https://www.shutterstock.com/image-photo/giant-eland-bandia-reserve-senegal-591079121

https://www.sciencephoto.com/media/1250603/view/eastern-giant-eland-turns-to-look-at-camera

https://www.dreamstime.com/close-up-photo-giant-eland-known-as-lord-derby-bandia-reserve-senegal-wildilfe-animal-also-africa-largest-species-image147763322

https://www.dreamstime.com/stock-image-giant-eland-image19760921

https://www.shutterstock.com/image-photo/giant-eland-savannah-antelope-located-africa-2031556622

https://www.dreamstime.com/stock-photo-giant-eland-zoo-florida-open-forest-savannah-antelope-photographed-miami-south-image54366408

TAUROTRAGUS EURYCERUS

The buccal colouration (https://www.dreamstime.com/mountain-bongo-sunshine-close-up-detail-african-antelope-posing-sun-image156500735) differs from those of all other tragelaphins, including congeners, as follows:

  • the whitish on the lips is restricted in area, but contrasts in both sexes with extremely dark adjacent pelage,
  • the bare edge of the lower lip is not dark (https://commons.wikimedia.org/wiki/File:Eastern_Bongo_Antelope_(4629428689).jpg),
  • the pale spot on the mandibular part of the cheek is extremely large, and
  • there is a dark beard, but it is so short, and located so far to the posterior, that it seems irrelevant to the buccal semet.

https://www.dreamstime.com/male-bongo-taurotragus-euryceros-male-bongo-taurotragus-euryceros-image194416886

https://www.dreamstime.com/stock-photo-bongo-antelope-bongo-tragelaphus-eurycerus-great-natural-environment-zoo-bor%C3%A5s-sweden-autumn-image82715544

https://www.dreamstime.com/beautiful-animal-big-eastern-bongo-antelope-extremely-rare-beautiful-animal-big-eastern-bongo-antelope-extremely-rare-animal-image101894871

https://www.dreamstime.com/mountain-bongo-antelope-tragelaphus-eurycerus-mountain-bongo-antelope-tragelaphus-eurycerus-eats-hay-under-shelter-image118182099

https://www.dreamstime.com/funny-closeup-face-eastern-mountain-bongo-critically-endangered-animal-specie-kenya-africa-spiral-horned-antelope-image148858133

https://www.dreamstime.com/royalty-free-stock-photography-tragelaphus-eurycerus-image14384997

https://www.dreamstime.com/closeup-portrait-eastern-mountain-bongo-grazing-grass-pasture-critically-endangered-animal-specie-africa-image149425845

https://www.dreamstime.com/royalty-free-stock-images-mountain-bongo-adult-grass-image33653269

https://www.dreamstime.com/face-eastern-mountain-bongo-closeup-critically-endangered-animal-specie-africa-image164858906

https://www.dreamstime.com/funny-closeup-face-eastern-mountain-bongo-critically-endangered-animal-specie-kenya-africa-spiral-horned-antelope-image148858133

https://www.dreamstime.com/close-up-detail-african-bongo-antelope-posing-sun-mountain-bongo-sunshine-image156500744

https://www.shutterstock.com/image-photo/portrait-lovely-bongo-1064503535

https://www.dreamstime.com/stock-image-bongo-antelope-tragelaphus-eurycerus-eurycerus-image36705331

https://www.dreamstime.com/stock-photo-bongo-tragelaphus-eurycerus-looking-food-ground-its-habitat-image52519124

https://www.dreamstime.com/bongo-tragelaphus-eurycerus-isaaci-eats-grass-sunny-spring-morning-image116605471

TRAGELAPHUS SYLVATICUS

The buccal colouration is such that he dark of the bare edge of the lips contrasts with the whitish of the pelage of the lips (https://www.gettyimages.com.au/detail/photo/male-bushbuck-royalty-free-image/594968558?adppopup=true and https://www.gettyimages.com.au/detail/photo/male-bushbuck-royalty-free-image/594968566?adppopup=true).

https://www.alamy.com/cape-bushbuck-in-kruger-national-park-south-africa-specie-tragelaphus-sylvaticus-family-of-bovidae-image185899438.html?imageid=702E8F49-45BC-4157-9914-850AF50686E6&p=272677&pn=2&searchId=5de8c54a310e51d49337c39c810170c1&searchtype=0

https://www.istockphoto.com/photo/bushbuck-gm495244662-77889519?phrase=bushbuck%20ewe

https://www.istockphoto.com/photo/bushbuck-ewe-tragelaphus-scriptus-grazing-gm1167980883-322316576?phrase=bushbuck%20ewe

https://www.alamy.com/stock-photo-male-bushbuck-83259353.html?imageid=9922FBE1-B4A8-4B7E-991C-228BB7405323&p=257778&pn=1&searchId=684f53868b913c7fa10a38c21f0564c5&searchtype=0

https://www.alamy.com/bushbuck-tragelaphus-scriptus-image66202156.html?imageid=1F4F5B3D-432B-4DD3-8496-D54B61F52803&p=178601&pn=1&searchId=684f53868b913c7fa10a38c21f0564c5&searchtype=0

https://www.alamy.com/buschbock-bushbuck-tregelaphus-scriptus-image261522989.html?imageid=01641FCD-B7C9-4E75-B3DB-4631D4381739&p=816330&pn=2&searchId=dfb1bd0a68ec8c57b7af6bc9aab357d3&searchtype=0

https://www.alamy.com/buschbock-bushbuck-tregelaphus-scriptus-image261522701.html?imageid=12BA0F46-8A62-4A16-9DE3-7A6798CD95E2&p=816330&pn=2&searchId=dfb1bd0a68ec8c57b7af6bc9aab357d3&searchtype=0

https://www.istockphoto.com/photo/cape-bushbuck-ewe-gm1391459767-448067029?phrase=bushbuck%20ewe

https://www.istockphoto.com/photo/bushbuck-gm495244310-77889157?phrase=bushbuck%20ewe

https://www.istockphoto.com/photo/bushbuck-cute-face-gm1133070757-300622617?phrase=young%20gazelle%20in%20profile

https://www.alamy.com/buschbock-bushbuck-tregelaphus-scriptus-image261524426.html?imageid=EA3A7655-CD51-4F97-BE2B-DDC269FCC195&p=816330&pn=1&searchId=684f53868b913c7fa10a38c21f0564c5&searchtype=0

https://www.alamy.com/menelik-bushbuck-tragelaphus-scriptus-meneliki-male-dinsho-ethiopia-image226042705.html?imageid=2A59DDAF-024B-43E4-A8F1-C904DD2E8B1B&p=703625&pn=1&searchId=c4807554bb1a466cf282cc8091f3a683&searchtype=0

https://www.alamy.com/stock-photo-bushbuck-young-male-33140583.html?imageid=9E28420C-BA40-4139-A291-FD5CB0CB5D17&p=95996&pn=3&searchId=860819a898d0b3e353b6310d1e861c73&searchtype=0

TRAGELAPHUS SCRIPTUS

The buccal colouration is similar to that in Tragelaphus sylvaticus.

https://www.alamy.com/stock-photo-bushbuck-harnessed-antelope-tragelaphus-scriptus-female-drinking-water-76072639.html?imageid=C3EF99E8-D978-40CC-9202-4D52169D823F&p=1142566&pn=1&searchId=684f53868b913c7fa10a38c21f0564c5&searchtype=0

https://www.alamy.com/close-up-of-a-male-bushbuck-tragelaphus-scriptus-in-the-jao-concession-okavango-delta-in-botswana-image343826781.html?imageid=E73EE6E9-8815-460E-980A-D87DDA0A8793&p=1249180&pn=1&searchId=684f53868b913c7fa10a38c21f0564c5&searchtype=0

https://www.alamy.com/intimidation-display-of-a-male-bushbuck-tragelaphus-scriptus-murchison-falls-national-park-uganda-image239726789.html?imageid=ABACDEAA-306A-44E7-A805-A958488CE07B&p=22059&pn=1&searchId=c4807554bb1a466cf282cc8091f3a683&searchtype=0

TRAGELAPHUS SPEKII and other spp. of sitatungas

The buccal colouration is similar to those of Tragelaphus sylvaticus and T. scriptus, but with the whitish of the pelage of the lower lip extended to the gape.

https://www.dreamstime.com/tomasz-podlak-bongo-antelope-feeds-wading-water-green-around-bongo-antelope-feeds-standing-water-image168756536

https://www.alamy.com/sitatunga-tragelaphus-spekii-image343527894.html?imageid=5C6870E0-0468-4470-A2FC-3BD3E452D1C1&p=75204&pn=3&searchId=6dca88fa24861c56fa081462157b3c1b&searchtype=0

https://www.alamy.com/female-sitatunga-antelope-or-marshbuck-tragelaphus-spekii-close-up-of-head-and-neck-image476395871.html?imageid=C26369BF-2D48-4B0F-8DAA-278550E0C4D9&p=1294449&pn=1&searchId=ba26f4280c10396a8388f35893a2dfaf&searchtype=0

https://www.alamy.com/female-sitatunga-antelope-or-marshbuck-tragelaphus-spekii-close-up-of-head-and-neck-image476395859.html?imageid=8595F948-D4CD-4343-BC46-F6C8E748BAEB&p=1294449&pn=1&searchId=ba26f4280c10396a8388f35893a2dfaf&searchtype=0

https://www.alamy.com/sitatunga-tragelaphus-spekei-image9661815.html?imageid=F3EDB784-40BC-4ACC-9DF2-3FA548B9EDBF&p=12859&pn=3&searchId=6dca88fa24861c56fa081462157b3c1b&searchtype=0

https://www.alamy.com/stock-photo-young-male-sitatunga-with-its-horns-just-emerging-uganda-east-africa-14694959.html?imageid=D2987602-78E4-42BD-AE42-CC7293D0396E&p=6945&pn=3&searchId=6dca88fa24861c56fa081462157b3c1b&searchtype=0

https://www.alamy.com/stock-photo-lesser-kudu-tragelaphus-imberbis-australis-laying-in-the-tall-grass-136679065.html?imageid=4505A744-48D2-4B6B-A57B-9EA8D10C4860&p=560173&pn=1&searchId=2d93f5fd0d262fe07ddf0d59810429c5&searchtype=0

https://www.alamy.com/stock-photo-sitatunga-young-147682858.html?imageid=B3D1B135-8388-494C-8865-C2DEDBCA3B54&p=456819&pn=1&searchId=ba26f4280c10396a8388f35893a2dfaf&searchtype=0

TRAGELAPHUS BUXTONI

The buccal colouration is similar to that in Tragelaphus spekii, with the addition that a dark/pale contrast develops on the pelage on the mandible, posterior to the gape, in adult males (https://www.alamy.com/ethiopia-bale-mountains-nationalpark-image342319127.html?imageid=92F707E0-6CCE-4C9F-9CF3-5E128CF7E060&p=851074&pn=3&searchId=82573a013a7114e7f4bd50c4986bd933&searchtype=0).

https://www.alamy.com/female-moutain-nyala-grazing-in-the-gaysay-grasslands-in-bale-mountains-national-park-image445236001.html?imageid=6C3BCA90-353C-44DF-8563-8693ABAB1ABC&p=887039&pn=3&searchId=82573a013a7114e7f4bd50c4986bd933&searchtype=0

https://www.alamy.com/female-mountain-nyala-tragelaphus-buxtoni-dinsho-forest-ethiopia-image178928393.html?imageid=57D13A0F-C4E6-43B8-9B66-3FDD4D74BB06&p=82922&pn=1&searchId=e54f3a90a919d4e7d869a7b57284f676&searchtype=0

https://www.dreamstime.com/close-up-male-female-mountain-nyala-lying-grass-ethiopia-image195489300

https://www.dreamstime.com/close-up-mountain-nyala-grassland-tragelaphus-buxtoni-ethiopia-image157991561

https://www.dreamstime.com/portrait-male-mountain-nyala-very-close-portrait-male-mountain-nyala-tragelaphus-buxtoni-dinsho-wetland-ethiopia-image145414555

https://www.alamy.com/female-mountain-nyala-bale-mountains-ethiopia-image220293157.html?imageid=5ECDB1C8-A644-490F-B891-9584C15AF626&p=135160&pn=1&searchId=e54f3a90a919d4e7d869a7b57284f676&searchtype=0

https://www.alamy.com/mountain-nyala-tragelaphus-buxtoni-female-dinsho-ethiopia-image226042677.html?imageid=ECD418E1-03B0-44CC-BA77-E16ACAA09FCF&p=703625&pn=1&searchId=e54f3a90a919d4e7d869a7b57284f676&searchtype=0

https://www.alamy.com/stock-photo-mountain-nyala-tragelaphus-buxtoni-bale-mountains-national-park-ethiopia-25983714.html?imageid=3E6BD96C-0294-422D-8A87-84D4328F9BC4&p=22059&pn=5&searchId=c6f23c57f8a8d0cf6e1d5b20b37e8218&searchtype=0

https://www.alamy.com/stock-photo-mountain-nyala-tragelaphus-buxtoni-bale-mountains-national-park-ethiopia-25983724.html?imageid=062F3D80-06CE-4FB4-A178-973342687E48&p=22059&pn=5&searchId=c6f23c57f8a8d0cf6e1d5b20b37e8218&searchtype=0

NYALA ANGASII

The buccal colouration (https://www.dreamstime.com/stock-images-young-bongo-image14097454) differs from that in Tragelaphus in four ways, viz.

  • on the upper lip, the whitish is confined to the anterior,
  • on the mandible, the whitish ends abruptly at about the longitude of the gape,
  • in adult males, the darkening of the face produces dark/pale contrast, and
  • unlike the pattern in T. sylvaticus and T. scriptus, the whitish on the lower lip extends to the gape.

https://www.alamy.com/lowland-nyala-tragelaphus-angasii-portrait-of-a-cute-famale-image211551732.html?imageid=2EC07AC3-F6D0-4E7C-A49B-F340FF49E83B&p=566373&pn=2&searchId=68074e3bde3b43152797f3554a4680f1&searchtype=0

https://www.alamy.com/stock-photo-nyala-tragelaphus-angasii-male-and-female-kapama-game-reserve-greater-48783217.html?imageid=F34FDE70-2E1C-4EB3-83C9-9524FE89127E&p=165079&pn=1&searchId=50e9f97d6347cb5e9d7b8ec238aca628&searchtype=0

https://www.dreamstime.com/royalty-free-stock-photo-african-antelope-image3633005

https://www.dreamstime.com/nyala-tragelaphus-angasii-male-portrait-kruger-national-park-south-africa-nyala-male-portrait-side-view-image239785421

https://www.dreamstime.com/nyala-lowland-portrait-nyala-lowland-portrait-zoo-park-image157688338

https://www.dreamstime.com/close-up-face-nayala-enjoy-eating-image152442625

https://www.dreamstime.com/nyala-antelope-portrait-south-africa-male-tragelaphus-angasii-mkuze-game-reserve-image256117400

https://www.dreamstime.com/royalty-free-stock-photo-nyala-antelope-portrait-male-tragelaphus-angasii-mkuze-game-reserve-south-africa-image37072955

https://www.dreamstime.com/stock-images-lone-nyala-image17067424

https://www.alamy.com/stock-photo-female-nyala-tragelaphus-angasii-92733610.html?imageid=035BC57A-961D-4EFC-BF33-D40142A9298C&p=282662&pn=1&searchId=50e9f97d6347cb5e9d7b8ec238aca628&searchtype=0

https://www.alamy.com/portrait-of-male-nyala-antelope-tragelaphus-angasii-mkuze-game-reserve-image66114553.html?imageid=40F7B2BC-B175-4C51-8363-F75CC8FF8430&p=70019&pn=1&searchId=50e9f97d6347cb5e9d7b8ec238aca628&searchtype=0

https://www.alamy.com/stock-photo-nyala-tragelaphus-angasi-sabi-sands-greater-kruger-national-park-south-25947606.html?imageid=09620EDA-87A2-4A86-A9DB-DE11B75C6610&p=74587&pn=1&searchId=50e9f97d6347cb5e9d7b8ec238aca628&searchtype=0

AMMELAPHUS IMBERBIS

The buccal colouration (https://www.alamy.com/lesser-kudu-tragelaphus-imberbis-small-antelope-image246475725.html?imageid=9BB55FE8-4BFC-49D6-AB7E-9E6548F6E1A3&p=84573&pn=1&searchId=2d93f5fd0d262fe07ddf0d59810429c5&searchtype=0) is intermediate between that of Tragelaphus and that of Nyala.

https://www.alamy.com/lesser-kudu-ammelaphus-imberbis-in-the-blooming-grass-lions-bluff-tsavo-national-park-kenya-image211254047.html?imageid=8EB93E74-52FA-46AE-AB92-FD770A83CC78&p=78230&pn=1&searchId=2d93f5fd0d262fe07ddf0d59810429c5&searchtype=0

https://www.inaturalist.org/observations/104569341

https://www.alamy.com/lesser-kudu-tragelaphus-imberbis-buck-tsavo-east-national-park-kenya-image209010297.html?imageid=312575D2-8C0F-45CE-8A47-D003055F569B&p=362016&pn=1&searchId=2d93f5fd0d262fe07ddf0d59810429c5&searchtype=0

https://www.alamy.com/stock-photo-lesser-kudu-tragelaphus-imberbis-122867683.html?imageid=D23553F3-C7DF-40D8-90A5-E8B3297F3808&p=354315&pn=1&searchId=2d93f5fd0d262fe07ddf0d59810429c5&searchtype=0

https://www.alamy.com/stock-photo-lesser-kudu-53073929.html?imageid=6711D4B8-A2A1-4AE7-ABF8-EC7524E6F3C4&p=176492&pn=1&searchId=2d93f5fd0d262fe07ddf0d59810429c5&searchtype=0

https://www.dreamstime.com/stock-photo-antelope-bongo-%C3%A2%E2%82%AC-largest-forest-beauty-nobility-grandeur-all-antelopes-africa-holds-first-place-as-image69341634

https://www.istockphoto.com/photo/an-angry-look-gm804218292-130411841

https://www.alamy.com/two-lesser-kudu-ammelaphus-imberbis-fight-each-other-lions-bluff-tsavo-national-park-kenya-image211254048.html?imageid=2F32722B-323B-4C0F-AC95-537223A17C27&p=78230&pn=1&searchId=2d93f5fd0d262fe07ddf0d59810429c5&searchtype=0

https://www.alamy.com/lesser-kudu-tragelaphus-imberbis-bucks-fighting-tsavo-east-national-park-kenya-image209010335.html?imageid=DF824358-E99A-41FB-B3FF-0B1CA61378F5&p=362016&pn=2&searchId=3b6a685767fbfca02df2e8e623771814&searchtype=0

https://www.alamy.com/a-lesser-kudu-in-captivity-standing-against-the-wall-to-stand-in-the-shade-image441773979.html?imageid=E2BFD3F1-7A6B-478A-B285-030C835DE0F6&p=156542&pn=1&searchId=2d93f5fd0d262fe07ddf0d59810429c5&searchtype=0

https://www.alamy.com/stock-photo-lesser-kudu-93428595.html?imageid=CA059F5B-00E7-40FB-A30F-52D295086B3C&p=291391&pn=1&searchId=2d93f5fd0d262fe07ddf0d59810429c5&searchtype=0

STREPSICEROS STREPSICEROS

The buccal colouration differs from that in Tragelaphus spekii in two ways, viz.

  • in males (including adolescents) of southern sspp., there is a short beard on the mandible, with its own dark/pale contrast, which would accentuate the movements of the mandible during chewing, and
  • the pale spot on the lower cheek/mandible is extremely variable in location, size, and distinctness.

The northeastern ssp. lacks any beard on the mandible (https://www.inaturalist.org/observations/40305320).

https://www.dreamstime.com/royalty-free-stock-photography-active-kudu-image1624537

https://www.alamy.com/stock-photo-greater-kudu-83380346.html?imageid=3F77ADE7-76CD-4BE8-AEC8-B863E7ADDDF5&p=258021&pn=1&searchId=a6e48eaa723d601f0ec36501ba7e4667&searchtype=0

https://www.rgbstock.com/photo/nF5Dlxo/Kudu+Female

https://www.dreamstime.com/close-up-kudu-bull-close-up-proud-kudu-bull-shamwari-game-reserve-eastern-cape-province-south-africa-image163484296

https://www.dreamstime.com/male-kudu-close-up-male-kudu-chobe-national-park-botswana-image157981022

https://www.dreamstime.com/amazing-close-up-huge-male-kudu-moving-sandy-banks-african-river-image256119835

https://www.pxfuel.com/en/free-photo-oeyrd

https://www.rgbstock.com/photo/okYb3oU/KUDU+Female++3

https://www.dreamstime.com/stock-image-kudu-bull-image20061331

https://www.inaturalist.org/observations/24986453

https://www.inaturalist.org/observations/98153597

https://www.alamy.com/stock-photo-a-mature-male-kudu-tragelaphus-strepsiceros-in-the-late-afternoon-29969095.html?imageid=C064B590-F27A-431E-87AE-216F302914EB&p=16440&pn=1&searchId=a6e48eaa723d601f0ec36501ba7e4667&searchtype=0

https://www.alamy.com/stock-photo-greater-kudu-83285005.html?imageid=C215FACE-D71D-4F8E-A5AB-6E2E2EAF2E7E&p=87116&pn=1&searchId=a6e48eaa723d601f0ec36501ba7e4667&searchtype=0

https://www.dreamstime.com/stock-photo-kudu-profile-male-greater-african-savannah-image46183091

https://www.inaturalist.org/observations/11253557

https://www.dreamstime.com/tan-pale-stripes-long-curved-horns-antelope-portrait-profile-male-greater-kudu-wildlife-portrait-male-image236629973

https://www.inaturalist.org/observations/95198649

https://www.dreamstime.com/stock-photos-kudu-antelope-female-image11335073

https://www.dreamstime.com/stock-images-kudu-antelope-female-image22113564

https://www.dreamstime.com/stock-images-kudu-antelope-portrait-image10432874

https://www.dreamstime.com/royalty-free-stock-photography-kudu-antelope-male-image7622007

https://www.dreamstime.com/royalty-free-stock-image-kudu-antelope-image13028506

to be continued in https://www.inaturalist.org/journal/milewski/70156-subtle-diversification-of-buccal-semets-in-tragelaphin-antelopes-part-2#...

Ingresado el 19 de septiembre de 2022 por milewski milewski | 27 comentarios | Deja un comentario

Adaptive colouration of northwestern oribi (Ourebia montana quadriscopa), part 2: buccal semet

@beartracker @oviscanadensis_connerties @tandala @tonyrebelo @ludwig_muller @jeremygilmore @paradoxornithidae @capracornelius @chewitt97 @biohexx1 @jwidness @saber_animal @jamesjarrett00 @aguilita @matthewinabinett @graysquirrel

...continued from https://www.inaturalist.org/journal/milewski/70081-adaptive-colouration-of-northwestern-oribi-ourebia-montana-quadriscopa-part-1#

BUCCAL SEMET

Buccal semets are any markings that serve to accentuate the chewing movements of the Jaws, particularly in ruminants.

Like flags, semets are activated by motion. However, semets tend to be smaller-scale than flags, and are so subtle that they have been overlooked by naturalists and zoologists until now.

Various ruminants possess a subtle pattern of dark/pale contrast at the junction of the 'chin' and the rest of the lower jaw. I hypothesise that this aids social monitoring within the species, particularly during rumination.

When bovids or cervids rest in small groups, vigilance depends on hearing as much as eyesight.

Cud-chewing would tend to interfere with hearing, because of the 'white noise' of grinding by the teeth.

When any individual detects cause for suspicion, it stops chewing, in order to listen up. This is potentially signalled to other members of the group by the interruption of the motion of the lower jaw.

Any distinctive pattern on the lower jaw, although conspicuous only at close range, can potentially aid this collective vigilance by emphasising the chewing movements, and thus also their sudden cessation.

The following illustrate typical situations in which a buccal semet would function, in Ourebia:
https://www.inaturalist.org/observations/17121843 and https://www.inaturalist.org/observations/39848905 and https://www.inaturalist.org/observations/39220728.

To acquire a search-image for a buccal semet in Ourebia montana, let us first examine one species of cervid, and two other spp. of bovids.

Also see https://www.inaturalist.org/journal/milewski/55532-previously-overlooked-facial-expressions-in-the-wapiti#.

Rusa unicolor:

https://twitter.com/D_Supriya/status/1270262947986767872

https://stock.adobe.com/search?k=%22rusa+unicolor%22&asset_id=170943770

https://es.123rf.com/photo_21215015_closeup-face-of-deer-muntiacus-feai-side-profile-in-the-jungle-environment.html

Taurotragus oryx:

https://stock.adobe.com/au/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=male+eland&order=relevance&safe_search=1&limit=100&search_page=7&search_type=pagination&get_facets=0&asset_id=196960936

https://stock.adobe.com/au/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=male+eland&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=300232095

https://stock.adobe.com/au/search?as_audience=srp&as_campaign=Freepik&get_facets=1&order=relevance&safe_search=1&search_page=0&as_content=api&k=male+eland&as_camptype=test-density-b&tduid=86f6bb255d68643c6d65a89810a8b212&as_channel=affiliate&as_campclass=redirect&as_source=arvato&asset_id=464125923

https://stock.adobe.com/au/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=male+eland&order=relevance&safe_search=1&limit=100&search_page=2&get_facets=0&search_type=pagination&asset_id=384537149

https://stock.adobe.com/au/search?as_audience=srp&as_campaign=Freepik&get_facets=1&order=relevance&safe_search=1&search_page=0&as_content=api&k=male+eland&as_camptype=test-density-b&tduid=86f6bb255d68643c6d65a89810a8b212&as_channel=affiliate&as_campclass=redirect&as_source=arvato&asset_id=294140010

https://www.freepik.com/premium-photo/large-male-eland-antelope_5818988.htm#query=male%20eland&position=40&from_view=keyword

https://www.freepik.com/premium-photo/large-male-eland-antelope_5818980.htm#query=male%20eland&position=38&from_view=keyword

https://stock.adobe.com/au/search?as_audience=srp&as_campaign=Freepik&get_facets=1&order=relevance&safe_search=1&search_page=0&as_content=api&k=male+eland&as_camptype=test-density-b&tduid=86f6bb255d68643c6d65a89810a8b212&as_channel=affiliate&as_campclass=redirect&as_source=arvato&asset_id=294139960

https://stock.adobe.com/au/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=male+eland&order=relevance&safe_search=1&limit=100&search_page=3&search_type=pagination&get_facets=0&asset_id=46484692

https://stock.adobe.com/au/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=male+eland&order=relevance&safe_search=1&limit=100&search_page=4&search_type=pagination&get_facets=0&asset_id=402656831

https://www.dreamstime.com/large-male-eland-antelope-large-male-eland-antelope-tragelaphus-oryx-natural-habitat-image160358444

https://www.dreamstime.com/large-male-eland-antelope-large-male-eland-antelope-tragelaphus-oryx-natural-habitat-image160358548

https://www.dreamstime.com/eland-antelope-solitario-comiendo-taurotragus-oryx-one-largest-antelopes-animals-very-difficult-to-approach-image161904009

Aepyceros melampus:

https://www.dreamstime.com/close-up-profile-portrait-impala-horns-grazing-field-image254412051

https://www.dreamstime.com/stock-photo-impala-ram-profile-image19333840

https://www.dreamstime.com/stock-photo-side-profile-male-black-faced-impala-etosha-national-park-namibia-image90694760

https://www.dreamstime.com/stock-images-male-impala-antelope-fighting-tarangire-national-park-image37475334

https://www.dreamstime.com/impala-aepyceros-melampus-males-fighting-masai-mara-park-kenya-image196305617

https://www.dreamstime.com/impala-aepyceros-melampus-males-fighting-masai-mara-park-kenya-image198642974

https://www.dreamstime.com/royalty-free-stock-images-portrait-impala-image3779909

https://www.dreamstime.com/impala-antelope-close-up-portrait-female-head-moremi-game-reserve-botswana-image157882201

Ourebia montana quadriscopa:

https://www.inaturalist.org/observations/8490559

https://www.inaturalist.org/observations/67005610 (compare this with https://stock.adobe.com/search?k=%22rusa+unicolor%22&asset_id=170943770)

Ourebia montana cottoni/masakensis:

https://www.inaturalist.org/observations/104527551

https://www.inaturalist.org/observations/100799069

Discussion:

There is a pattern, in Ourebia montana, that is shared with ruminants as diverse as Rusa, Taurotragus, and Aepyceros.

However, in O. montana the pattern is so faint, to the human eye, that nobody would have noticed it, but for a search image,

I suspect that there is an ultraviolet component to the pattern in Ourebia, which the human eye can hardly detect.

Ingresado el 19 de septiembre de 2022 por milewski milewski | 10 comentarios | Deja un comentario

17 de septiembre de 2022

Adaptive colouration of northwestern oribi (Ourebia montana quadriscopa), part 1

The northwestern oribi (Ourebia montana quadriscopa, according to my recent revision of this genus) has adaptively inconspicuous colouration.

The pattern is 'plain', i.e. cryptic (https://en.wikipedia.org/wiki/Crypsis).

In this way, the northwestern oribi conforms with several other ruminants with which it coexists in the savannas of West Africa, viz.

Another coexisting ruminant, namely Tragelaphus scriptus (https://www.mindenpictures.com/stock-photo/southern-bushbuck-(tragelaphus-scriptus-sylvaticus)-immature-male-standing/search/detailmodal-0_80126209.html), also has adaptively inconspicuous colouration.

However, in T. scriptus the pattern, instead of being 'plain', is disruptive (https://en.wikipedia.org/wiki/Disruptive_coloration). This is because its intricate markings break up the outline of the figure, against a background of plant stems and dappled shade.

Despite the overall plainness of Ourebia montana quadriscopa, the details of its colouration are noteworthy.

The pale ventral surfaces on the body and inner surfaces of the upper limbs (https://www.inaturalist.org/observations/66999215 and https://www.inaturalist.org/observations/16025242) are consistent with the cryptic principle of countershading (https://en.wikipedia.org/wiki/Countershading).

Minor aspects of the colouration of O. m. quadriscopa, which may have some conspicuous function, are as follows:

Please note that an individually variable dark spot on the crown of females, which is present in northeastern sspp. of Ourebia montana (https://www.imago-images.com/st/0067825819? and https://www.alamy.com/oribi-ourebia-ourebi-small-antelope-from-african-bushes-and-savannahs-murchison-falls-uganda-image448339248.html and https://www.inaturalist.org/observations/98122948), seems generally absent in O. m. quadriscopa.

Of the above, most can be explained as minor features of disruptive colouration, subsidiary to the main pattern of crypsis.

The main feature that, although small-scale, is unambiguously conspicuous in function, is a pedal flag.

This is because

  • it cannot confer any advantage in terms of hiding the stationary figure,
  • it can aid intraspecific monitoring without increasing the risk of being noticed by scanning predators, owing to the different distances involved.

The pasterns are pale enough to accentuate the action of walking. I suspect that this paleness is more conspicuous in ultraviolet, and that, to the relevant eyes (i.e. those of the oribi itself), the flag is visible by night. In addition, I suspect that this pedal flag is more conspicuous in ultraviolet than in the spectrum visible to the human eye.

The following show this subtle pedal flag in Ourebia ourebi quadriscopa:

https://www.inaturalist.org/observations/8490596
https://www.inaturalist.org/observations/49107232
https://www.inaturalist.org/observations/8490605
https://www.inaturalist.org/observations/16099463
https://www.inaturalist.org/observations/29326368
https://www.inaturalist.org/observations/91161569
https://www.inaturalist.org/observations/91165825
https://www.inaturalist.org/observations/67044396
https://www.inaturalist.org/observations/67044375
https://www.inaturalist.org/observations/67005624
https://www.inaturalist.org/observations/6441964
https://www.inaturalist.org/observations/67005621
https://www.inaturalist.org/observations/8490600
https://www.inaturalist.org/observations/8490596

Sylvicapra grimmia campbelliae (https://www.inaturalist.org/observations/91165836), which widely coexists with O. m. quadriscopus, is analogous in several ways, as follows:

Firstly, S. g. campbelliae likewise possesses a pedal flag. However, a difference is that in the cephalophin it is the fetlocks that are pale, with the pasterns dark instead.

Secondly, S. g. campbelliae likewise possesses a caudal flag of modest size and conspicuousness.

However, the caudal flags of the two forms differ in both configuration and function. That of O. m. quadriscopus is activated when fleeing from predators, whereas that of S. g. campbelliae is not. In the latter only, the tail is wagged routinely during walking.

to be continued in https://www.inaturalist.org/posts/70101-adaptive-colouration-of-northwestern-oribi-ourebia-montana-quadriscopa-part-2#...

Ingresado el 17 de septiembre de 2022 por milewski milewski | 20 comentarios | Deja un comentario

Why do pale cheek-spots in tragelaphin bovids contain vibrissal tufts?

Ingresado el 17 de septiembre de 2022 por milewski milewski | 1 comentario | Deja un comentario