September 25, 2022

One of the few records of stotting in hippotragin bovids


please scroll to 24th photo in for style-trotting, a form of stotting, in Oryx gazella

Posted on September 25, 2022 22:42 by milewski milewski | 1 comment | Leave a comment

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

...continued from


absent from all three spp.


Buttock flag

present only in Raphicerus campestris:

Pedal flag

present in some subspecies/individuals of Raphicerus sharpei (see

possibly also present in some individuals of R. campestris: and

Caudal flag

absent from all three spp.


Auricular semet

absent from all three spp.

Buccal semet

possibly present in all three spp., in human eyes clearest in Raphicerus campestris ( and and and and least clear in Raphicerus melanotis (see


The following is typical of the social setting in which the buccal semet hypothetically functions:

Pedal flags are poorly-developed in all spp. of Raphicerus, in contrast to certain coexisting species/subspecies such as Sylvicapra grimmia caffra (

The main feature of adaptively conspicuous colouration in Raphicerus is the buttock flag of R. campestris. 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, 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 change in the shape of the back, from

The following show the change in the conspicuousness of the white of the buttocks as the posture changes from unalarmed ( to mildly/initially alarmed (

The following suggests that, as long as the hindquarters remain hunched, the buttock flag can hardly be displayed: What is needed is at least the posture shown in:

Posted on September 25, 2022 22:15 by milewski milewski | 5 comments | Leave a comment

September 23, 2022

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

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...continued from

Grysboks (Raphicerus melanotis and and Raphicerus sharpei ( and and 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 (

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 ( and and and

Even more so, when one considers that any differentiation in hues (rufous ground-colour vs grey on the posterior surface of the ears, 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


Many species of mammals have grizzled/speckled pelage, in which each hair is graduated in colour from the base to the tip (

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.


The face of grysboks is not plain-coloured. One of the best illustrations of the pattern can be found by scrolling in

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:

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 ( 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 (

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 ( and

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 ( and and Please note, in the following view (, 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.


Countershading ( is better-developed in R. sharpei than in R. melanotis. This is unsurprising, based on similar latitudinal patterns in various other ruminants (

The paleness, in R. melanotis, of the inner surface of the hind leg, is puzzling. This is because this part of the anatomy

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

I tentatively suggest that this pale feature functions as a flag, during walking in the oblique illumination of morning and evening. This flag, I hypothesise, aids social monitoring by means of a low-profile signal.

A similar argument may apply to the even smaller pale feature at the anterior axil of the foreleg, which likewise transgresses countershading.


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

Posted on September 23, 2022 21:37 by milewski milewski | 19 comments | Leave a comment

September 20, 2022

Subtle diversification of buccal semets in tragelaphin antelopes, part 2

...continued from


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 ( 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.

Posted on September 20, 2022 21:35 by milewski milewski | 2 comments | Leave a comment

September 19, 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 (

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.


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 ( 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.

For additional illustrations see


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..


The buccal colouration ( 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 (,
  • 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.


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 ( and


The buccal colouration is similar to that in Tragelaphus sylvaticus.

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.


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 (


The buccal colouration ( 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.


The buccal colouration ( is intermediate between that of Tragelaphus and that of Nyala.


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 (

to be continued in

Posted on September 19, 2022 22:32 by milewski milewski | 27 comments | Leave a comment

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

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...continued from


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: and and

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

Rusa unicolor:

Taurotragus oryx:

Aepyceros melampus:

Ourebia montana quadriscopa: (compare this with

Ourebia montana cottoni/masakensis:


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.

Posted on September 19, 2022 05:52 by milewski milewski | 10 comments | Leave a comment

September 17, 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 (

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 (, also has adaptively inconspicuous colouration.

However, in T. scriptus the pattern, instead of being 'plain', is disruptive ( 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 ( and are consistent with the cryptic principle of 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 ( and and, 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:

Sylvicapra grimmia campbelliae (, 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

Posted on September 17, 2022 23:05 by milewski milewski | 20 comments | Leave a comment

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

Posted on September 17, 2022 05:48 by milewski milewski | 1 comment | Leave a comment

The three main types of oribi (Ourebia), at a glance

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(Also see and

Dear reader, who among you would assume that the following belong to a single species?

In explanation of this incongruity, I offer the following summary.

Species/subspecies of genus OUREBIA, on the basis of geographical radiation:

quadriscopa (plus dorcas, and possibly aequatoria)
sexually dimorphic in both body size and body shape
inconspicuous colouration, with small-scale flags (caudal and pedal)
tail dark brown on upper surface, pale on lower surface
buttocks pale brown, with whitish restricted to narrow bracketing of the tail
habitat wooded

montana (plus gallarum, cottoni, masakensis, and hastata)
sexually dimorphic in both body size and body shape
inconspicuous colouration, with small-scale flags (could and pedal)
tail medium brown on upper surface, pale on lower surface
buttocks pale brown, with whitish almost restricted to narrow bracketing of the tail and
habitat semi-wooded

ourebi (plus rutila)
sexually monomorphic in both body size and body shape
conspicuous colouration overall
tail black on both upper and lower surfaces
buttocks fully white
habitat treeless

Ear pinnae are larger in quadriscopa ( than in ourebi ( and scroll in

The northeastern type barely qualifies for a caudal flag, because there is so little dark/pale contrast on tail/rump/buttocks.

A pedal flag (conspicuously pale pasterns) is present in quadriscopa etc. ( and montana etc. ( and, but absent in ourebi etc.

On the basis of the above, I propose that there are two spp. of Ourebia, viz.

  • COMMON ORIBI (consisting of the northwestern and northeastern forms, with adaptively inconspicuous colouration), and
  • SOUTHERN ORIBI (consisting of the southwestern forms, with adaptively conspicuous colouration).
Posted on September 17, 2022 03:50 by milewski milewski | 8 comments | Leave a comment

September 15, 2022

Are there two species of oribi (Ourebia), instead of one?

Dear reader, can you spot the glaring error in the following picture of an oribi? (Scroll in

If your answer is not immediate, please see

The error is that the form of oribi (Ourebia) depicted for a national park in Free State province, South Africa, is completely the wrong form of oribi.

The real appearance of the oribi in Golden Gate National Park is this:

Anyone familiar with the real oribi of South Africa should be able to spot, at first glance, that a photo from elsewhere in Africa has been carelessly inserted.

A search in Google Images quickly reveals that the photo ( was actually taken in central Ethiopia (

(Another website for a conservation area, depicting the wrong oribi in several photos, is

But there is more to this question of identity than meets the eye.

According to the current, rather neglected, taxonomy, the correction would be merely one of subspecies.

However, is it perhaps time to rethink the number of species in this genus, in the first place?

The patterns on the hindquarters are so different that it seems that there may actually be different species involved.

Let us provisionally call these two postulated spp. the common oribi and the southern oribi.

The scientific names would be:

  • SOUTHERN ORIBI Ourebia ourebi (Zimmermann, 1783), vs
  • COMMON ORIBI Ourebia montana (Cretzschmar, 1826).

These two spp. differ mainly in that, in the former alone, the tail is black and the buttocks are extensively white. This means that, in the southern oribi, the hindquarters are conspicuous at a distance, whereas in the common oribi the hindquarters are not conspicuous at a distance.

This would seem to make adaptive sense.

The southern oribi, after all, tends to live in extensively treeless grasslands, where opportunities to hide are limited. By contrast, the common oribi tends to live in savannas, where not only is the grass relatively tall, but there is some cover of shrubs and saplings.

Another obvious difference is in the ground-colour, covering most of the body. This is dull fawn in the common oribi, but bright fawn in the southern oribi.

However, there is a biogeographically intriguing complication.

This is that a form resembling the southern oribi, rather than the common oribi, occurs over a large area in the western half of Zambia, extending widely into Angola and narrowly across the Caprivi Strip of Namibia, into northern Botswana.

The subspecies name of this Zambian form, which has been photographed mainly in Kafue ( and and Liuwa Plain national parks, is currently O. o. rutila.

This looks more similar to the southern oribi than to the form in Zimbabwe, Malawi, and Mozambique at similar tropical latitudes - which is currently called subspecies O. o. hastata.

So, if we were to recognise two spp. of oribi, then the adjective 'southern' might be subject to two caveats, viz.

  • the distribution extends as far north as Katanga and north-central Angola, which are nearly equatorial, and
  • this distribution is disjunct, the gap corresponding to eastern Botswana and western Zimbabwe (with the exception of Kazuma Pan National Park,, in the extreme northwest of Zimbabwe).

If true, what this would leave us with is a hitherto overlooked anomaly in the distribution of oribis in southern Africa.

This is that, when one crosses from the highlands of Limpopo province of South Africa ( to the southeastern part of Zimbabwe, one changes the species of oribi. Yet when one moves all the way from Gauteng province of South Africa, across the easternmost Kalahari, to northern Botswana, one does not change the species.

For some strange reason, it seems that the following may be true.

The common oribi - which occurs widely from West Africa to Ethiopia and then through East Africa to central Mozambique - has penetrated as far south as low-lying southeastern Zimbabwe (

Here, the common oribi may perhaps survive in the Save Conservancy (, but seems never to have been photographed.

And this new perspective also raises the question of the real identity of any populations remaining in southern Mozambique.

These have previously been assumed to belong to ssp. ourebi, which seems reasonable given the former occurrence of this species ( in the Lebombo mountains of northeastern Eswatini (

However, is it possible that the oribi occurring, or formerly occurring, in southern Mozambique, north and east of the Limpopo River (, is actually the common oribi, Ourebia montana hastata?

If so, this would mean that there are two species of oribi not only within the drainage of the Limpopo River, but also within the latitudes of Kruger National Park (

These would be

Posted on September 15, 2022 13:12 by milewski milewski | 27 comments | Leave a comment

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