Journal archives for March 2023

March 01, 2023

A previously overlooked difference between the blesbok and the bontebok: pale vs dark tail-tassel

@michalsloviak @geichhorn @colin25 @tandala @dewald2 @simontonge @tonyrebelo @jeremygilmore

The blesbok (Damaliscus pygargus phillipsi) differs from the bontebok (Damaliscus pygargus pygargus) in having a pale distal section to the tail-tassel (

This difference has not, as far as I know, been noticed by any naturalist or zoologist.

The tail-tassel of both subspecies of Damaliscus pygargus, when intact, reaches to below the hock.

In the bontebok, the whole tail-tassel is always dark ( and and and

However, in the blesbok, the distal part of the tail-tassel tends to be pale:

Second photo in

For an index to my many Posts about the genus Damaliscus, please see

Posted on March 01, 2023 01:40 AM by milewski milewski | 13 comments | Leave a comment

Previously overlooked expansions of the 'bles' in the blesbok (Damaliscus pygargus phillipsi), signifying full maturity, beyond adulthood

Many photos of the blesbok (Damaliscus pygargus phillipsi) show individuals in which

This spreading of the facial bleeze - which I have not seen mentioned in the literature - may possibly be a sign of age (exceeding ten years). This is indicated by the fact that many of the photos concerned are of captive specimens.

The ultimate result is seen in

Most of the photos below refer to females, but males also show this pattern (e.g. and and

We now know of at least three aspects of the colouration of the blesbok that show particular depigmentation, compared to the bontebok (Damaliscus pygargus pygargus), viz.

The pattern on the cheeks, described here, occurs also in the bontebok ( However, it is faint and uncommon in that subspecies. and

Please note the extremely long horns, indicating advanced age, in the central figure in

Also see and

For an index to my many Posts about the genus Damaliscus, please see

Posted on March 01, 2023 09:23 PM by milewski milewski | 15 comments | Leave a comment

March 02, 2023

Unlike the blesbok, the bontebok (Damaliscus pygargus pygargus) lacks an auricular flag

@jwidness @michalsloviak @tonyrebelo @simontonge @jeremygilmore @oviscanadensis_connerties @tandala @colin25 @beartracker @grinnin @botswanabugs @gigilaidler @christiaan_viljoen

Dear Reader, what do you notice about the ears in the following photos?



The adaptive colouration of the two subspecies of Damaliscus pygargus is intriguing.

The bontebok (Damaliscus pygargus pygargus) and the blesbok (Damaliscus pygargus phillipsi) are, in most respects, more and less vivid versions of each other.

Therefore, it would have surprised nobody if a conspicuous feature of colouration in the blesbok were even more conspicuous in the bontebok.

Yet, in the case of the auricular flag, the opposite is the case.

In both subspecies, the posterior surface of the ear pinnae is greyish, apparently owing to the dark skin being sparsely covered with short, pale pelage (

Because this pelage has a sheeny quality, the ear pinnae can appear conspicuously pale in certain illuminations.

And this sheeny pallor, although a small feature relative to the size of the whole animal, can serve as a social signal by virtue of the mobility of the ear pinnae.

The following footage of the blesbok is illustrative:

What is particularly intriguing:

Contrary to expectations, it is the generally duller subspecies, namely the blesbok, that qualifies as possessing an auricular flag, whereas the more vivid subspecies, namely the bontebok, does not.

The failure of the bontebok to qualify for an auricular flag is owing to the following factors:


The following show the auricular flag in the blesbok:

Third photo in

Second photo in

Scroll to second photo in

Third photo in

Scroll to seventh photo in


The following show that, in the bontebok, there is a hint of the same pattern.

Scroll to sixth photo in

Second photo in

Third photo in

Scroll to third photo in

Scroll to second photo in

The following of the bontebok nearly qualify as showing an auricular flag:


The comparison can be summarised by means of the following photo-pair.



Were it the case that the bontebok was the sole form of Damaliscus pygargus, probably nobody would have noticed the colouration of its ear pinnae, at all.

However, the noticeable 'flashing' of the ears in the blesbok has set up a search-image. According to the standard set by the blesbok, the bontebok falls short.

There are thousands of photos of the bontebok on the Web, but few come close to showing the clarity and consistency of the auricular flag seen in this view of the blesbok:

The following pair of photos of the blesbok shows the full difference produced by angle of illumination, via the sheeny quality of the pelage on the posterior surface of the ear pinna: versus

The following shows the difference, within a single specimen (

A possible explanation for the lack of an auricular flag in the bontebok is that the behaviours of the two subspecies differ.

The blesbok habitually head-nods ( and and

It does this to an extent and with a frequency that I have not noticed in the bontebok.

Head-nodding, as well as standing in the midday sun with the head lowered and the ears drooping, would tend to display the auricular flag ( and and

For an index to my many Posts about the genus Damaliscus, please see

Posted on March 02, 2023 06:18 PM by milewski milewski | 45 comments | Leave a comment

March 03, 2023

Do blesbok and bontebok differ enough in sexual dimorphism to be different species?

@paradoxornithidae @simontonge @matthewinabinett @katebraunsd @jwidness

I have been closely familiar with Damaliscus pygargus for many decades.

More than half a century ago, I was already sketching both subspecies with as much precision as possible, based on the limited photographic material available at the time.

Furthermore, I have collected what is perhaps the largest dossier of hard-copy photos of the blesbok ( and the bontebok ( in the world, clipped from brochures, books, and every other pre-electronic source available.

So, it should be hard to surprise me with any aspect of the appearance of the blesbok and the bontebok.

However, it was only in the last week, when I took the trouble to scrutinise every one of the thousands of relevant photos on the Web, that several surprisingly large differences dawned on me.

In recent Posts, I have covered the

Now, in this Post, I would like to point out a surprising difference in sexual dimorphism between blesbok and bontebok - which, together with the other differences, seems to indicate that these are full species, not merely subspecies.


The blesbok is said to be about 8 kg heavier than the bontebok ( However, this is misleading.

What seems more accurate is that the blesbok and the bontebok are like-size in the case of the more important sex in physiological/metabolic/ecological terms, namely females. It is the fully mature males that seem to differ, owing to the development of extra brawn (particularly on the neck) in males of the blesbok.

The facts of body mass are as follows.

The body mass of the blesbok is given in The mean was 58 kg, for a sample of eight adult female individuals in good condition.

Huntley (1971, reports the mean body mass of mature males of the blesbok as 73.4 kg (sample size was 22 individuals). This varied from 68 kg at the height of the dry season (October, sample size = 5) to 78 kg in the green season (January, sample size = 6).

As reported by Jordaan (, on page 51:
According to Hoffman et al. (2008,, mean body mass for the blesbok was 67.4 kg, for a large sample (65 individuals) of females and males combined.

Smit (2004, Master of Consumer Science thesis, University of Stellenbosch) reports in her Summary that the mean body mass of the blesbok is 60.2 kg for adult females and 67.4 kg for adult males (sample size was collectively 73 individuals).

On page 9 of the same thesis, she states that "The mean live weight for blesbok males is 62.7 to 95.3 kg, and for females is 59.5 to 86.3 kg," I assume that she really means the ranges of individual masses, not the averages.

Other, less helpful references on body masses include the following:

Turning now to the bontebok:

Jordaan (2020, Table 3.1 on page 47) provides definite data for the body mass of adult males of the bontebok. The sample size was 20 individuals, and the mean was 65.8 kg.

The mean body mass of adult males of the bontebok is informally said to be 61 kg (

I doubt the following, which seem exaggerated:


The head, including the horns, is noticeably larger in mature males of the blesbok than in

  • mature males of the bontebok, or
  • adult females of either blesbok or bontebok.

Van Zyl and Ferreira (2004) state that the mean mass of the head in adult females of the blesbok is about 3.5 kg. This is 6% of body mass.

Jordaan (2020, Table 3.1 on page 47) states that the mean mass of the head in adult males of the bontebok is 4.8 kg. This is 7% of body mass.

I have yet to see corresponding data for fully mature males of the blesbok. However, I suspect that the values exceed 7 kg and 8.5%.

Please compare the proportional sizes of the head in the following figures, standardised by posture:

Blesbok adult male:

Bontebok adult male:

Bontebok adult female:


Adult females, the most important category biologically, seem to be like-size in the bontebok and the blesbok.

In the case of mature males, the available data imply that the bontebok is indeed (as claimed in smaller-bodied than the blesbok - the mean values being about 66 kg and 75 kg respectively. In full maturity, males of the blesbok have been known to surpass 95 kg.

Based on the above information, I suggest that

  • in both the blesbok and the bontebok, mean body mass of adult females is about 60 kg,
  • in the blesbok, mean body mass of mature males is about 75 kg, whereas
  • in the bontebok, mean body mass of mature males is only about 66 kg.

What seems to have been overlooked by previous authors is that males grow stouter (particularly head and neck) with full maturity in the blesbok than in the bontebok.

In other words, I suggest that it is not so much that the bontebok is smaller than the blesbok; it is more that the former is less sexually dimorphic than the latter.

To get an idea of the scale of the differences involved, we can compare adult male blesbok with adult female bontebok, as follows.

Dear reader, to appreciate this maximum contrast, please toggle back-and-forth between and

In particular, please note the relative size of the head in each case.

Now, please note the stoutness/stockiness, and proportionately large head, of the following mature male specimen of the blesbok. Has any reader ever seen such proportions in the bontebok?

The following is fairly typical of mature males of the bontebok. The body-proportions resemble those of females of the blesbok, and the horns are also noticeably smaller than in the blesbok:


The facts remain somewhat elusive. However, my impression is that the blesbok and the bontebok are about as biologically different from each other as are the tsessebe (Damaliscus lunatus/superstes) and the topi (Damaliscus korrigum/topi/jimela/tiang,

If these realisations stand up to scrutiny, perhaps we should classify the blesbok and the bontebok as separate (albeit interfertile) species, viz. Damaliscus phillipsi and Damaliscus pygargus?


Blesbok adult male

Blesbok adult male

Blesbok adult male

Blesbok adult male

Bontebok adult male

Bontebok adult male

Blesbok adult female

Blesbok adult female

Blesbok adult female

Bontebok adult female

Bontebok adult female

For an index to my many Posts about the genus Damaliscus, please see

Posted on March 03, 2023 09:32 AM by milewski milewski | 15 comments | Leave a comment

A photo-comparison of bleezes and flags in the blesbok versus the bontebok

(writing in progress)

The following photo-pair shows the two subspecies in posteriolateral view.

Both have a facial bleeze, that of the blesbok being proportionately larger owing to the difference in the relative sizes of the head.

The bontebok has an extremely well-developed pedal flag, whereas this individual of the blesbok, viewed in this perspective, lacks a pedal flag.

The pygal flag of the blesbok is replaced by a pygal bleeze in the bontebok.

In the blesbok, the abdominal and ulnar flags are separate, but in the bontebok there is a white ventral panel that subsumes both the abdominal and the ulnar pattern.




Blesbok and





Adult male bontebok

(writing in progress)

For an index to my many Posts about the genus Damaliscus, please see

Posted on March 03, 2023 12:47 PM by milewski milewski | 7 comments | Leave a comment

March 04, 2023

Adaptive colouration in the blesbok (Damaliscus pygargus phillipsi), part 2: infants, juveniles, and adolescents

...continued from

The blesbok has uniform pale colouration at birth, which differs categorically from that of adults.

In juveniles of Damaliscus pygargus, the facial colouration is the inverse of that of adulthood, with the facial bleeze beginning dark, and the adjacent cheeks beginning pale ( and

INFANTS (birth to three months old, including first appearance of horns)

The colouration of infants of the blesbok is categorically different from that of adults.

The ground-colour (including the posterior surfaces of the ear pinnae) is pale, with countershading. The countershading includes the ventral surface of the neck.

The tail-tassel is merely incipient.

The only distinct pattern is seen on the face, where the ground-colour of the rostrum and upper lips is crisply separated from whitish cheeks. Whitish extends on to the orbits except for the anterior side of the orbits ( and and

This is, in a sense, the opposite pattern from that in adults (

There is also

The maximum body size reached by offspring within the infantile colouration is shown in and the second photo in At this stage the weight of infant/juvenile is about one quarter of maternal weight.


3-6 months old:

The rostrum, and to lesser degree the upper foreleg, abruptly turn dark (

This produces a temporary 'inverse' version of the facial bleeze.

The following, of adult female and juvenile (?4.5 months old) of the blesbok, is one of the clearest illustrations of the conspicuous facial pattern suddenly adopted by juveniles, after three months of infantile colouration. This conspicuous pattern is the inverse of the adult pattern, in that the rostrum is dark while the cheeks are pale:

About eight months old (see ):

Whitish hairs appear on the rostrum, creeping upwards from the nose. Countershading disappears from the neck.

8-12 months old:

At about one year old, pale appears on the forehead (individually variable). The rostrum (now pale) and tail-tassel (dark since birth) remain proportionately shorter than in adults.

ADOLESCENTS (1-2 years old, see

Among the last features to form fully is the whitish patch on the forehead.

ADULTS (>2 years old, see

Fully mature adults:



I have noticed then following tentative differences, which depend on further photographic evidence for verification:

Perhaps the most significant finding:

Juveniles, 3-6 months old, have more conspicuous facial colouration in the blesbok than in the bontebok. This is the inverse of the relationship between these two taxa in adulthood, at the scale of the whole figure.

This unexpected difference hints that the blesbok and the bontebok are actually different species, not merely subspecies of the same species.

Also see

For an index to my many Posts about the genus Damaliscus, please see

Posted on March 04, 2023 12:11 AM by milewski milewski | 22 comments | Leave a comment

March 11, 2023

Adaptive colouration in the bontebok (Damaliscus pygargus pygargus), part 1: adults

Also see

The bontebok (Damaliscus pygargus pygargus) is one of the most vividly-coloured wild ungulates on Earth.

However, its colouration has not previously been described coherently, relative to a conceptual framework based on adaptation. Furthermore, previous descriptions have been limited by the lack of suitable terms.

A reminder of the difference between a bleeze and a flag:

A bleeze is a large-scale feature of colouration, so bold that it makes the whole figure conspicuous even at a distance, and even when the animal is stationary.

A flag is a relatively small, or normally hidden, feature of colouration, which becomes conspicuous with motion.

The bontebok can be described as 'pied' ( However, this is unsatisfactory, because

  • it does not elucidate the functional organisation of the markings, and
  • it does not distinguish between an adaptive design and that seen in pied individuals and breeds of domestic mammals (

Various wild ungulates possess bleezes. However, what makes the bontebok unusual is that

In this account, I ignore the hues on the pelage of the bontebok, and consider only the tones (white, shades of grey, and black). This is because ungulates and their carnivoran predators do not perceive hues in the same ways as humans do.



The conspicuously pale patch on the rostrum of adults of Damaliscus pygargus ( constitutes what is probably the clearest example of a facial bleeze, in any mammal.

In the bontebok, this patch is pure white, contrasting with the dark ground-colour of the face and neck.

There is minimal variation in the facial bleeze, between the sexes, and among individuals. However, a few individuals show slight expansion at the base of the horns (

Comparison with blesbok (

The pale rostral patch on the face seems proportionately slightly smaller in the bontebok than in the blesbok, owing to what I perceive to be a difference in the size of the head.

Furthermore, in the bontebok the pale on the face tends not to expand with age, as it does in the blesbok ( and

However, the facial bleeze is as well-developed in the bontebok as in the blesbok, because it seems exempt from the glandular staining seen in males of the blesbok ( and


The lateral bleeze of the bontebok is, proportionately, one of the largest bleezes seen in any ungulate. It extends from the withers and the back to the ventral edge of the thorax and the belly. It also Includes the posterior surface of the upper foreleg, and the anterior surface of the hindleg just below the knee ( and

The pattern is one of horizontal banding on a broad design, in which the upper and lower panels are pale, with the flanks forming a dark median panel.

However, an important qualification is that the upper panel appears pale partly owing to sheen. Its conspicuousness thus depends on illumination.

The design of the lateral bleeze of the bontebok is such that in bright sunlight at midday, when the ventral white is inconspicuous owing to shading, the dorsal sheen is 'switched on' owing to sheen ( and

Comparison with blesbok:

A categorical difference is that, unlike the bontebok, the blesbok lacks a lateral bleeze.

The pelage of the flanks is not necessarily any paler in the blesbok than in the bontebok. However, the differences are that, in the blesbok,

  • the dorsal sheen is poorly-developed,
  • the pale ventral pelage is restricted, and reduced to a combination of countershading and an abdominal flag, and
  • the white anterior edge of the hindleg, just below the knee, is narrower than in the bontebok.


  • the abdominal flag of the blesbok ( does not occur in the bontebok, having been subsumed within a broader white, ventral panel, and
  • the ulnar flag of the blesbok does not occur in the bontebok, the dark/pale contrast on the posterior surface of the upper foreleg - although just as clear - functioning as an anterior extension of the ventral white of the thorax (and thus being better-regarded as part of the lateral bleeze) in the bontebok.


The ischiopygal bleeze of the bontebok is about as large as the facial bleeze, but located at the opposite pole of the figure ( and

The pale posterior feature of the bontebok

  • extends from the rump to the tail-stalk and the buttocks,
  • is largely white, and
  • contrasts with the dark pelage around it.

Comparison with blesbok:

The ischiopygal flag of the blesbok bears the same relationship to the ischiopygal bleeze of the bontebok as the abdominal flag of the blesbok ( bears to the white ventral panel of the lateral bleeze of the bontebok.

Furthermore, the ischiopygal flag of the blesbok depends mainly on sheen effects, whereas the ischiopygal bleeze of the bontebok depends mainly on the depigmentation of the pelage.


The lower legs of adults of the bontebok are largely white, making them conspicuous in locomotion.

Comparison with blesbok:

Both the bontebok and the blesbok possess a pedal flag. However, this feature is better-developed in the bontebok, in which

  • the white pelage is more extensive, particularly on the outer surfaces of the lower legs, and
  • there is less individual variation.


In the bontebok, there is a considerable sheen on the short, sparse pelage on the posterior surface of the ear pinnae. In some.views this produces a noticeably pale aspect to the back-of-ear.

However, after perusing hundreds of photos, I have not found this effect to be strong or consistent enough to qualify as an auricular flag. It is better-regarded as an incipient/residual version of the pattern in the blesbok (see below).

Comparison with blesbok:

The ear pinnae seem identical in size and pigmentation in the bontebok and the blesbok.

However, perusal of hundreds of photos shows that the sheeny quality of the posterior surface is better-developed in the blesbok ( and than in the bontebok.

This, together with the distraction presented by the relatively well-developed sheen on the withers and back, disqualifies the bontebok, in my view, for an auricular flag (

The lack of an auricular flag in the bontebok is significant evolutionarily. This is because all of the postcranial pale features are better-developed in the bontebok than in the blesbok.


Please see


The colouration of adults of the bontebok is configured in such a way that the figure is conspicuous, regardless of whether

to be continued in

For an index to my many Posts about the genus Damaliscus, please see

Posted on March 11, 2023 01:51 AM by milewski milewski | 20 comments | Leave a comment

March 13, 2023

Which ruminant is born with the most conspicuous facial pattern of colouration? part 1: hippotragin and alcelaphin bovids

@tandala @simontonge @paradoxornithidae @tonyrebelo @jeremygilmore @oviscanadensis_connerties @davidbygott @dejong @michalsloviak @christiaan_viljoen @capracornelius @gigilaidler @maxallen

Various ruminants have bold facial markings in both sexes, helping to make the animals adaptively conspicuous.

An example is

However, in most ruminants, infants hide for a period ( This makes it adaptive for the colouration to be inconspicuous at birth.

In this Post, I examine four species of bovids with boldly-marked faces, and I illustrate the colouration in infancy, relative to that in adulthood.

These are

  • two hippotragins, in which infants hide, and
  • two alcelaphins, in which infants accompany their mothers continually right from the start.


In this species of hippotragin bovid, adults possess a facial bleeze.

At birth, the facial pattern is not plain. However, it is so nebulous that it is certainly inconspicuous (

As infants grow, the facial pattern, like the horns, develops precocially.


This hippotragin bovid probably qualifies for a facial bleeze in adults (

The relationship of infants to adults is similar to that in Oryx gazella.

However, the pattern is so precocial that an argument can be made for at least a facial flag in infants. If so, H. equinus may exemplify the presence at birth of a facial flag, in ruminants.


This species of alcelaphin bovid certainly qualifies for a facial bleeze in adults.

As in the hippotragins shown above, infants are born with a trace of the facial pattern of adults. However, the relative placement of dark/pale is puzzlingly inverted (see and


Unlike the three species shown above, the facial colouration of Connochaetes albojubatus is ambivalent in its boldness. However, I include it here because it is the form of wildebeest with the most conspicuous facial colouration.

In the case of wildebeests, the patterns tend to be obfuscated by

  • the confusing complex of species/subspecies, in which various aspects/features of colouration vary in emphasis rather than presence/absence,
  • sheen/antisheen and other effects of illumination, and
  • individual variation.

However, in adults of C. albojubatus, the cheeks tend to be clearer and paler than in other forms of wildebeest, and equally sheeny. This means that C. albojubatus is the wildebeest most likely to qualify for a facial flag.

What is noteworthy is that the facial pattern is also more preocial in C. albojubatus ( than in other wildebeests, with the possible exception of another form with a pale beard, viz. Connochaetes mearnsi.


The facial pattern in adults of C. albojubatus is, owing to individual variation and the effects of illumination, not consistent enough to qualify for a bleeze. Its maximum expression is seen in

This pattern - which does qualify as a facial flag - consists of

  • a consistently black rostrum,
  • a pale beard, located close enough to the dark muzzle to provide pale/dark contrast, and
  • cheeks that are usually pale, sheeny, and free of brindling.


There are too few photos available to assess individual variation. However, the black rostrum tends to be fully expressed at birth.

The cheeks of infants are not as obviously pale as in most adults, and the pale beard (although precocial) is inconspicuous at birth.

However, a previously overlooked aspect is that, unlike adults, the blackish of the face extends ventral to the eyes ( The facial insignia are thus, in a limited sense, better-developed in infants than in adults, making wildebeests unusual among ruminants.

It is noteworthy that Damaliscus pygargus, another alcelaphin, also has a distinction between infants and adults in the colouration of the orbits. The difference is that, in infants of D. pygargus, the orbits are noticeably pale, not noticeably dark (

Scroll in

Scroll in


The facial pattern in juveniles of C. albojubatus is as conspicuous as that in adults (

As growth proceeds, the pelage below the eye loses its black pigmentation (


I know of no ruminant that is born with a facial bleeze.

A facial flag at birth seems plausible in Hippotragus equinus. This would be consistent with

Since infants of H. equinus hide initially, it is unknown how the precociality of the facial pattern is adaptive. Even in adults, the adaptive value of bold facial colouration in hippotragins remains poorly understood.

What is more complex, and even more intriguing, is the ontogeny of the facial pattern in certain alcelaphins.

The facial pattern in infants of wildebeests ranges from inconspicuous in Connochaetes gnou ( and and scroll to fifth photo in to conspicuous in C. albojubatus.

The remaining forms are intermediate, with Connochaetes mearnsi and Connochaetes taurinus mattosi ( apparently exceeding Connochaetes taurinus taurinus, C. t. cooksoni, and C. t. johnstoni.

For infants of wildebeests to have conspicuous colouration seems consistent with extreme adaptation for gregariousness in open environments, and extreme precociality at birth.

However, it remains unexplained why wildebeests vary in this respect.

It remains possible that C. mearnsi (see first comment below) exceeds C. albojubatus in the consistent boldness of the facial pattern in infants. This depends on further photographic evidence.

Given that, in adults, the facial pattern in C. mearnsi is less conspicuous than that in C. albojubatus, this might make C. mearnsi unique among ruminants, in having a facial pattern more conspicuous at birth than in adulthood.

In this context, I remind readers that infants of wildebeests also possess a pedal flag (, absent in adults.

Posted on March 13, 2023 09:23 PM by milewski milewski | 28 comments | Leave a comment

March 14, 2023

Which ruminant is born with the most conspicuous facial pattern of colouration? part 2: Rupicapra

Posted on March 14, 2023 04:15 PM by milewski milewski | 0 comments | Leave a comment

March 15, 2023

Adaptive colouration in the bontebok (Damaliscus pygargus pygargus), part 2: infants, juveniles, and adolescents

...continued from

The bontebok is well-known for its extreme colouration. However, what is not generally appreciated is how complex the facial colouration is, as it develops from birth to adulthood.

This complexity has never, as far as I know, been described, let alone explained.

At birth, the colouration of the bontebok is fairly plain (

This is puzzling, given that infants do not hide in this species, instead accompanying their mothers from the start.

However, the puzzle of plain colouration in infancy is eclipsed by a greater puzzle as the animal grows into the juvenile stage.

This is because the facial pattern goes through a series of changes that seem superfluous to the relatively simple conversion of the fawn-coloured rostrum of infants to the white rostrum of adults.

It is almost as if Nature has used the juvenile face of the bontebok as a canvas, on which to paint - merely for their own sake - a series of organised designs, before erasing them ( and and


At birth, the bontebok is fawn-coloured with countershading, plus

The pattern on the head may seem negligible at first glance. However, on closer examination it poses a fundamental evolutionary puzzle.

I describe this pattern as follows:

The facial pattern of infants of the bontebok is inconspicuous, because

  • the pale feature on and near the orbits is small-scale, and
  • there is no dark pelage, anywhere on the head.

However, what is remarkable is that this pattern is not merely a nebulous or incipient version of the adult colouration, as is the case in hippotragin bovids (

Instead, the pattern is different from that in adults. It is as if infants and adults are different species.

To be precise, the only parts of the head of infants that already show adult colouration are:

  • a small whitish triangle just above the rhinarium, and
  • the whitish hairs on the anterior surface of the ear pinnae.

The following show infants close-up:

The following show infants with their mothers:

The infantile pattern of colouration persists to the age of three months. At this stage the horn-tips have appeared, and the body mass exceeds a quarter of maternal body mass:

The following series of photos, of an individual infant (1-2 months old), is one of the clearest expositions on the Web of the infantile colouration of the bontebok. The infantile colouration of the bontebok is not as pale as that of the blesbok, but more clearly shows countershading.

Damaliscus pygargus pygargus:


The following series provides one of the clearest illustrations of juvenile colouration in the bontebok: and and

At the juvenile stage, the colouration on the neck, body, and legs changes directly towards that of the adult.

However, the colouration of the head goes through convoluted changes.

The first change on the head is a darkening of the rostrum (

The following ( and and and and show that there is a brief stage at which the darkest part of the juvenile figure (apart from the developing tail-tassel) is a particular panel on the front of the face.

This is closely followed by a darkening of the orbits, and the appearance of a complex, pale streak from the cheek, through the temple, to the crown (third photo in and and

The following shows the dark/pale differentiation on the cheek (

The following shows the maximum extent of pale on and near the temples (

The pale on the temples is among the last signs of the juvenile colouration to disappear (

The whitish ventral surface of the mandibles remains in the juvenile stage ( The following shows the discrete pattern that arises at 0.5-1 year old, only to vanish in adulthood (

The following show juveniles nearly 6 months old:

The following show juveniles about one year old, when the dark on the rostrum is being gradually replaced by the white hairs of adulthood:

The following ( and and and show particularly clearly the tardiness of the posterior surface of the upper foreleg, above the carpal, in turning dark.

Throughout the juvenile stage, the ventral surface of the neck retains the countershading that will eventually be lost in adulthood (

The following, of juveniles more than one year old ( and, show several aspects particularly clearly, viz.

  • the horns are about three-quarters of full length and the body mass is about 60% of maternal body mass,
  • the dark pelage on the figure remains paler than that of adult females,
  • the face remains proportionately shorter than in adults, limiting the prominence of the whitish (which is not yet fully white) on the face, and
  • the dark pelage on the legs remains incomplete.

When the horns reach three-quarters of their full length ( and, the few juvenile features remaining include

  • a trace of countershading on the ventral surface of the neck,
  • incompleteness of the dark above the carpal, and
  • a pale streak on the temple.


One of the last features to form completely is the dark pelage on the posterior surface of the upper foreleg, just below the white patch on the ulna ( and

As the rostrum rapidly lengthens and the facial colouration approaches completeness, a dark periphery to the pale features on the forehead and rostrum can intensify and linger ( and

The colouration becomes complete before the horns have attained their full length ( However, a trace can remain of the last juvenile feature to disappear, namely the pale vertical streak on the temples, even when the horns seem full-length.


The complexity of the changes in facial colouration can be contrasted with the simplicity of the changes on the hindquarters ( and

Unlike the facial bleeze, the ischiopygal bleeze of the bontebok starts to appear at the end of infancy (, and then simply and directly continues to completion within a mere three months.

The ischiopygal bleeze is complete at about six months old (, when the face is still unrecognisably different from that of adults.

Almost every aspect of the ontogenetic development of colouration in the bontebok is puzzling, from the viewpoint of adaptation and evolution.

The main questions arising from this examination are as follows:

  • how is it adaptive for infants to have cryptic colouration, given that they do not hide (this is particularly puzzling because the plain colouration persists despite the body mass being trebled from birth to three months old)?
  • why does the facial pattern go through such complex, temporary changes from three months to one year old? and
  • how has such disparity arisen between the pygal bleeze and the facial bleeze, with the former developing early and directly, vs the latter being delayed until adolescence, and emerging from an unrecognisably different, transitional pattern?

Also see

For an index to my many Posts about the genus Damaliscus, please see

Posted on March 15, 2023 03:39 AM by milewski milewski | 33 comments | Leave a comment