Journal archives for December 2023

01 December, 2023

Why have two coexisting bovids, the sable antelope (Hippotragus niger) and Lichtenstein's hartebeest (Alcelaphus lichtensteini), diverged in vomeronasal (flehmen) expression?

@beartracker @matthewinabinett @paradoxornithidae @tonyrebelo @jeremygilmore @botswanabugs @capracornelius @henrydelange @christiaan_viljoen @dejong @tandala @oviscanadensis_connerties @davidbygott @nyoni-pete

The sable antelope (Hippotragus niger, and Lichtenstein's hartebeest ( and are sympatric and biologically comparable.

Both species are

  • gregarious bovids (,
  • of similar body size (about 150-200 kg),
  • approximately restricted to the miombo biome (,
  • specialised on a diet of grasses growing on nutrient-poor soils, and
  • less sexually dimorphic (e.g. with horns present in both sexes) than expected for gregarious, polygynous ruminants.

However, the sable antelope and Lichtenstein's hartebeest differ remarkably in their facial expressiveness when using the vomeronasal organ ( and for intraspecific communication.

Various mammals exhibit a facial expression called 'flehmen' ( when 'sniffing' for hormones/pheromones and other substances of sociosexual significance. In many cases, this is done by paying attention to the urine of conspecifics, and in some cases the urine is taken in liquid form into the mouth, before flehmen is expressed.

In ungulates, flehmen is an expression in which

  • the muzzle is lifted and the jaws open wide enough to inhale slowly by mouth,
  • the nose is retracted, at least partly closing the external nares,,
  • the upper lips are fully raised,
  • the tongue is withdrawn.

(Note that flehmen does not involve any action of the tongue-tip in touching a surface/material of interest and then placing the tongue-tip at the location of the vomeronasal organ on the roof of the mouth. Please see

This expression seems to aid the passage of hormones/pheromones to the vomeronasal organ via the roof of the mouth, while simultaneously reducing the distraction of normal olfaction, by reducing nasal inhalation.

Flehmen can thus be thought of as an expression facilitating 'smell' by means of the mouth, or a deliberate and fine-tuned 'tasting of the air'.

This expression occurs in adult males of about 86% of all ungulates ( and,more%20are%20on%20the%20brink.).

Flehmen is most commonly seen when males monitor the urine of females for oestrus (

However, our two species are remarkably deviant from the norm, in opposite ways.

In the case of the sable antelope, what is odd is that flehmen is expressed by not only males but also

In the case of Lichtenstein's hartebeest, what is odd is that no flehmen expression has ever been observed at all, even in mature males.

What this means is that the sable antelope has boosted flehmen to its maximal incidence among all ungulates, whereas Lichtenstein's hartebeest - like all members of the genera Alcelaphus and Damaliscus - seems to have downplayed this expression to the point of losing it completely.

Indeed, in Alcelaphus and Damaliscus, males seem to take no interest in the urine of females (please see

On page 126, Estes (1991) states of the sable antelope:
"Bulls accompanying a herd routinely urine-test all females...Other cows and even young calves also perform the urine test very frequently, unlike other ungulates." (This applies also to Hippotragus equinus, page 117.)

The following show flehmen in mature males of the sable antelope:,vid:lKJZQKCNvdY,st:0,vid:2rdGZ5ntfYo,st:0

On page 138, Estes (1991) states:
"Antelopes of the genera Alcelaphus and Damaliscus are the only bovids so far known that do not urine-test females (i.e., sample the urine, then curl the lip and/or open the mouth in the flehmen grimace). Yet they have an apparently functional vomeronasal organ. How do they find out when a cow is coming into heat?"

I have found no relevant depictions of Lichtenstein's hartebeest. This is unsurprising, because there is no behaviour drawing the attention of photographers.

However, the following shows how males of a congener sniff the posterior of females, with the mouth closed:


Can any reader explain the extreme incidence of flehmen in the sable antelope, vs its absence in Lichtenstein's hartebeest?

Possible clues include the following:

The genus Hippotragus, including the sable antelope, is extreme among ruminants in its sociosexual behaviour.

The relevant syndrome comprises a confusing combination of facets, including:

  • intimidating horns (designed for harm rather than ornamentation and ritual), present in both sexes and relatively precocial,
  • minimisation of skin-contact among individuals, with no mutual grooming and minimal maternal grooming,
  • female emulation of masculine self-advertisement and assertiveness,
  • conspicuous dark/pale contrast on the face, suggesting 'warning colouration',
  • loose bonding between infants and mothers, and
  • delayed expulsion of adolescent males from the group.

Please also see:

When this syndrome is sufficiently understood, could the emphasis on flehmen emerge as somehow compatible/complementary/compensatory with the other facets?

For its part, Lichtenstein's hartebeest is not 'opposite' or 'converse' to the sable antelope, because it too is relatively sexually monomorphic among ruminants.

However, the main peculiarities of Alcelaphus are in anatomy, including

These anatomical features are consistent with extreme cursoriality (speed and endurance in running), and specialisation for selectively grazing relatively short grasses by taking bites that are not only small, but obligatorily so.

This suggests that flehmen has been lost in Alcelaphus (and Damaliscus) partly because this expression is constrained by the exceptional 'tightness' of the mouth.

Wildebeests (Connochaetes) have faces as elongated as those of other alcelaphins, but do show the flehmen expression ( and

This is perhaps explained by the fact that the muzzle is broader in wildebeests than in other alcelaphins, allowing enough flexibility for an 'eversion' of the upper lip that may be constrained in Lichtenstein's hartebeest.

The only ungulates, as far as I know, that rival alcelaphins in the tightness of the gape are giraffes (Giraffa). However, giraffes, unlike Lichtenstein's hartebeest, show flehmen (

This is perhaps explained by the length and flexibility of the upper lip ( and

The upper lip of giraffes is, together with the tongue, adapted for the selection of shoots on trees and shrubs ( and and and

The difference in the width and flexibility of the gape between hippotragin and alcelaphin bovids is evident when the animals are fleeing:

Posted on 01 December, 2023 05:44 by milewski milewski | 34 comments | Leave a comment

02 December, 2023

Diet of the sable antelope, part 2: Hippotragus niger niger, with particular reference to basaltic soils in Zambezi National Park

@troos @wynand_uys @richardgill @bartwursten @dejong @simontonge @tonyrebelo @jeremygilmore @jwidness @jakob @adriaan_grobler @reubenheydenrych @andrew_hankey

...continued from

My reference (xeroxed) is:
Richard D Estes and Runhild K Estes (1970) The sable in Rhodesia. Second progress report. National Geographic Society, hippotragine antelope study.

As in part 1, my reason for making this electronic record is that the valuable information in this report, now more than half a century old, risks permanent loss otherwise.

More particularly, the main location, in what is now Zambezi National Park (, seems never to have been subsequently visited by naturalists. It happens inadvertently to be shown in, which is not an actual plotting of the observation.

Estes' main study area, 26 km upriver from Victoria Falls, now approximates merely to a remote picnic site. I refer to Chamunzi, as shown in

I assume that this obsolescence is because the original Victoria Falls National Park was reconfigured with the gazetting of the adjacent Zambezi National Park in 1979 (a decade after the fieldwork reported here). The 'Chundu Loop' ( and and around Chundu Vlei, consisting of tracks routinely accessible to visitors to Victoria Falls National Park in 1969, seem to have been excised from the tourist circuit in Zambezi National Park. This permanently closed the area to the public, except for 4X4 adventurers.

The fact that Estes' report refers to a now-forgotten patch of basaltic terrain makes the information all the more worthy of securing in the public record.

Fieldwork was conducted in June-July 1969.

Description of relevant vegetation on basaltic soils northwest of Chundu Vlei in what was, at the time, Victoria Falls National Park (page 4):

(as in part 1, I have brought all the scientific names up to date)


"The grasses...are mostly small and sparse annuals, that turn almost white in the dry season. Aristida spp. predominate in many places. On heavy clay soils, a low annual, Moorochloa eruciformis, tended to be dominant, while Andropogon fastigiatus was often common on rocky ground. Taller, tufted perennials occurring in scattered clumps, especially along dry watercourses and on hillsides, included Andropogon gayanus mainly, followed by Cymbopogon caesius, and Hyparrhenia spp., with occasional Sorghum versicolor and Bothriochloa pertusa [sic]. The seasonally waterlogged vlei grasslands are dominated by tufted perennials. The leaf table averaged about two feet high in June/July, with flowering stalks making a thin screen of up to 6 ft. On one meadow (Chundu Loop) that was sampled for dominant species, Ischaemum afrum and Andropogon gayanus appeared co-dominant, followed by Cymbopogon caesius, Hyparrhenia filipendula (?), Heteropogon contortus, Bothriochloa pertusa [sic], Dicanthium annulatum and tall Aristida spp., with Moorochloa eruciformis and Andropogon fastigiatus on the edge of the bordering mopane scrub. The vlei grasslands had a reddish brown colour, though green stool shoots were still being produced by some plants late in July, especially Cymbopogon caesius (Pepper grass)[]."

Description of relevant vegetation on deep siliceous sand in what was, at the time, Victoria Falls National Park (page 4):

"The grass cover here is better and richer in species than in the basalt zone, consisting mainly of tufted perennials...The leaf table averaged about one foot and all grasses and already ceased growing, apparently before the end of June...Chamabonda Vlei, a drainage line grassland some 12 miles long..., has a somewhat different species composition than vleis of the basalt soils. The grass cover tended to be thicker and taller, dominated by Hyparrhenia spp., with abundant Heteropogon contortus, Digitaria sp., and Eragrostis superba, with an understorey of Cynodon dactylon and Panicum repens, which formed a lush sward on the site of a dried-up pan."

The following shows Hippotragus niger niger in Chamabonda Vlei, which now falls within Zambezi National Park:

The following shows a dried-up pan and dense grass in the same area:

In the following dietary list, I have updated the species-names, several of which have been revised/synonymised, since 1969.

V = Victoria Falls National Park (now Zambezi National Park)
C = Chobe National Park
H = Hwange National Park (Robins Camp)
M = Matobos National Park


*Asterisked spp. are those heavily utilised by H. niger niger in this study

1 = good forage value, 2 = average forage value, 3 = poor forage value, x = occurring in disturbed areas (Rattray J M 1960 The habit, distribution, habitat, forage value and veld indicator value of the commoner Southern Rhodesian grasses. Rhod. Agr. J. 57(5): 424).


*Andropogon gayanus 1 V H

Andropogon chinensis 2 V

*Andropogon fastigiatus 2 V

Andropogon schirensis 2 V

Aristida adscensionis H

Bothriochloa insculpta 1 H M

Chloris gayana 1 H

Chloris virgata 1 x H

Cynodon dactylon 1 x C

Dactyloctenium giganteum 1 C

Dicanthium annulatum 2 H

*Digitaria eriantha (incl. setivalva) 1 C M

*Digitaria milanjiana 1 H

Eragrostis rigidior 2 x C

Eragrostis superba 2 V H

*Heteropogon contortus 2 V H M

Hyparrhenia filipendula 2 H M

*Ischaemum afrum V H

*Megathyrsus maximus 1 H M

*Moorochloa eruciformis 2 x V

Panicum coloratum 1 H

Pogonarthria fleckii C

Pogonarthria squarrosa x M

Rottboellia exaltata 1 x V

Schizachyrium sanguineum 3 V

Schmidtia pappophoroides 1 V C

Setaria sphacelata 2 V

Sorghum versicolor 2 V

Sporobolus ioclados M

Sporobolus panicoides 3 V

*Themeda triandra 2 M

Urochloa brachyura 1 x C H

Urochloa brizantha 1 x H

Urochloa trichopus x H



Blepharis bainesii V



Combretum apiculatum C


Croton megalobotrys C


Diplorhynchus condylocarpon V


Grewia monticola V


Tarchonanthus camphoratus M

Fabaceae: Faboideae:

Philenoptera nelsii C

Philenoptera violacea V

Fabaceae: Caesalpinioideae:

Bauhinia petersiana V

Thespesia garckeana V

The following is another excerpt from the text in Estes and Estes (1970), relevant to diet.


Pages 13-15:

"In general, dry grasses were selected [during the dry season, when observations were made], even when green shoots of species sable are known to eat at other times were present. Having previously noted that in other areas they invariably selected the tenderest and greenest grasses, the sight of sable subsisting on standing hay came as a surprise. It apparently marked a definite change-over in diet coinciding with the period when preferred grasses cease active growth. In fact, they continued to select many of the same species that we had seen sable feeding on in the rainy season...The fact that the shift took place while green shoots could still be found may indicate that the effort required to gain a fill of green grass outweighed its nutritional advantage over cured grass. In Victoria Falls National Park, the grazing preferences and behaviour of herds living in the mopane/mixed deciduous savanna [on basaltic soils] both differed considerably from the other sable we observed. Throughout June and July, the diet of the Big Herd [on basaltic soils], for instance, consisted largely of two small annuals: Moorochloa eruciformis and Andropogon fastigiatus. The former was particularly abundant in the mopane/Combretum scrub grassland where the herd spent most of its time. Such common constituents of vlei grasses as Andropogon schirensis and Andropogon gayanus, Sorghum versicolor, Cymbopogon caesius and Heteropogon contortus, present in scattered clumps, were grazed to a limited degree only, while Hyparrhenia spp., even though still producing green stool shoots in July, appeared untouched. The two annuals were not only completely dry but also lay on the ground as litter in many places. The Big Herd was harvesting the Moorochloa and A. fastigiatus like cattle feeding on loose hay. Each part of the pasture where the herd fed was worked over in minute detail. Often the sable spent several days in succession within an area of a few hundred square yards. Grazing animals progressed so slowly that a movement of no more than a few yards in half an hour was not exceptional. For example, a yearling was seen to stand without moving a single yard for 10 minutes, eating the whole time, gathering in large mouthfuls of the hay before pausing to chew and swallow. The heavy black cotton soils preferred by this Moorochloa crack deeply and become highly friable after drying and trampling. Consequently annuals were regularly pulled up by the roots, often with a clod of earth attached. The sable spent considerable time in discarding the clods, shaking their heads vigorously to break them off, gaping and pushing with their tongues to eject clods that got into their mouths. Roan and zebra feeding on the same type of pasture near the Salt Pan at Robins Camp were also seen to pull up many plants by the roots. By the time the herd had finished working over an area the ground was stripped bare in many places; in others unpalatable Aristida spp. concealed the extent of bare earth. Such a pattern of utilisation would create havoc in perennial grassland, but in a pasture consisting largely of annuals, it may be asserted that the sable were fully exploiting their food resources with a minimum of damage. Litter would have mulched and helped protect the soil against drying and excessive insolation. On the other hand, aside from fertilising the soil, the trampling of the sable made it more friable, helping to prevent 'capping' - a very common occurrence in Rhodesia due to understocking (Savory, pers. comm.) - which by preventing rain from penetrating the soil drastically reduces rainfall effectiveness. In any case, the real damage to such pasture in Victoria Falls National Park was done long ago...The same animals displayed another still more unusual feeding habit: they consumed quantities of a prostrate perennial herb, Blepharis bainesii, that resembled and was as prickly as a thistle. It grew abundantly in the same places as their favourite annual grasses, a small ball of spiny leaves surrounding blue flowers at the end of a thin, wiry stem. A sable would gingerly close its mouth over one, grip the stem with its lips, and pluck it. Then, standing with head outstretched and tilted to one side, mouth gaping, it would proceed to ensalivate the ball until it was soft enough to chew and swallow. Since it was impossible for us to pull up or hold one without pricking our fingers, sable apparently have pretty tough gums. Apart from the herds along the Zambezi, most of the other sable we observed followed what we had come to consider the normal grazing pattern for the species: they kept moving while grazing, from tuft to tuft of preferred perennial grasses, and usually shifted their ground from day to day. Andropogon gayanus, Ischaemum afrum, Heteropogon contortus, Digitaria eriantha, Bothriochloa pertusa [sic,] and Dicanthium annulatum were heavily utilised in most areas. These are the same genera and many of the same species that sable prefer in Zambia, Tanzania and Angola; only Heteropogon contortus, commonly and unaffectionately known as spear grass because of its sharp, clinging seeds, is less common in regions of higher rainfall. Generally speaking, these and other preferred grasses were found growing most luxuriantly in the ecotone between woodland and vlei - i.e. on the 'edge'. The grasses commonly dominant in the lower and wetter parts of the vleis (Hyparrhenia spp., Tristachya superba, Setaria and other Digitaria spp.), taller and also greener, were largely unutilised in June and July. Perhaps in years when the vleis remained unburned, sable work their way toward the centre as the dry season advances and end up feeding on these other grasses. In Victoria Falls National Park, as already noted, a herd of bachelor males was more or less resident on the Chundu Loop vlei at the beginning of June (although feeding on the same grasses as sable that stayed on the edge). Not until July fifth was a nursey herd seen grazing out on this meadow. This and other observations suggested that sable do feed out in the vleis later in the dry season, with adult males in the vanguard. But in Wankie [Hwange] National Park and wherever roan occur together with sable, the former is seen feeding out in the middle of the vleis far more often than the latter. Their habitat and food preferences overlap, more or less, according to season and other factors, but the overlap occurs mainly on the edge, from which the two orient in opposite directions: sable toward the woodland and roan toward the grassland."

The following illustrate Blepharis bainesii:

to be continued in

Posted on 02 December, 2023 06:59 by milewski milewski | 13 comments | Leave a comment

04 December, 2023

'Flehmen' is an exaggeration in elephants, while underplaying the reality of their vomeronasal dexterity

@paradoxornithidae @matthewinabinett @tonyrebelo @jeremygilmore @botswanabugs @ldacosta @maxallen @jwidness @ptexis @christiaan_viljoen @zarek @dejong

The vomeronasal organ ( performs chemical perception (

It is, by definition, located on the partition between the nasal cavity and the buccal cavity, allowing access from

  • above, via the nostrils (nares), or
  • below, via the mouth, or
  • both.

(The vomeronasal organ is discernible in the human foetus. However, it is regarded as relictual/vestigial, and probably functionless, in most adult individuals of Homo sapiens,,of%20the%20accessory%20olfactory%20system.)

In many mammals, vomeronasal perception is associated with flehmen ( and

In the literature, elephants ( are regarded as expressing flehmen (see references below).

This would be remarkable, because

Actually, I see scant evidence that elephants express flehmen. This has been misrepresented in the literature.

However, the reality is even more remarkable.

This is that elephants use the vomeronasal organ in an uniquely direct and precise way, among mammals.

Crucial to realising that 'flehmen' is a misnomer in elephants is that this term refers to peculiar facial expressions, not events of sensory application as such.

This can perhaps best be explained by comparing elephants with mice.

Both rodents and proboscideans clearly possess a vomeronasal organ, even in adulthood.

In both cases,

  • the organ is embedded in a bony partition which is simultaneously the floor of the nose and the roof of the mouth, and
  • it is accepted that the organ is specialised for intermittent perception of substances of sociosexual significance, such as hormones/pheromones.

However, flehmen is unrecorded in rodents. There is no particular facial expression or posture associated with vomeronasal sensing. Instead, it seems that rodents merely inhale substances of interest via the nose, or lick them, or both.

If 'flehmen' or 'the flehmen response' were a sensory event, the literature would surely regard rodents as qualifying for flehmen. However, as far as I know, no author has made such a claim. Instead, the literature seems, at least tacitly, to acknowledge that flehmen is absent in rodents, in contrast to e.g. lagomorphs and hedgehogs.

The facial expression/posture of elephants, when applying the vomeronasal organ, has little in common with flehmen in ungulates, carnivores, lagomorphs, etc. Instead, it seems identical to that of simply placing a food-item, or drinking water, in the mouth.

So, how can flehmen be claimed in elephants?

The action of elephants in placing the proboscis in the mouth does not necessarily qualify as a facial expression in the first place, let alone flehmen. And it shares none of the diagnostic aspects of a flehmen expression, mentioned in the text of a previous Post (

It is perhaps unsurprising that elephants use the tip of the proboscis to place substances of interest directly at the vomeronasal location on the roof of the mouth.

However, what seems misleading - and incorrect - is that the term 'flehmen' has been stretched to include this action of the proboscis, on the basis of context.

Such conflation tends to deplete the term 'flehmen' of meaning, while at the same time obscuring something more worthy of recognition.

I refer to the following possibility:
Elephants may be the only mammals that - in partial emulation of snakes and lizards ( and and and - dexterously procure samples of interest and then place them directly at the vomeronasal location.

This is as opposed to the relatively awkward approach of merely inhaling by mouth, or taking urine into the mouth and then inhaling by mouth.

Once we appreciate the approach taken by elephants, a new question arises, as follows.

Why is it that even those mammals with relatively long and 'dexterous' tongues have not been recorded sampling substances of sociosexual interest with the tongue-tip, and then placing the tongue-tip at the vomeronasal location?

This question applies particularly to


Posted on 04 December, 2023 04:12 by milewski milewski | 25 comments | Leave a comment

07 December, 2023

Diet of the sable antelope, part 3: Hippotragus niger variani, with special mention of geophagy


...continued from

Please see:

My reference (xeroxed) is:
Richard D Estes and Runhild K Estes (1970) Preliminary report on the giant sable (Hippotragus niger variani). Third progress report. National Geographic Society, hippotragine antelope study.

Fieldwork was conducted in September 1969-March 1970.

The special interest of this report is that it dates back to the period before the Angolan Civil War ( During this war, which lasted more than a quarter of a century, all scientific contact with Hippotragus niger variani was lost.

After the war, H. n. variani was found to have survived, albeit barely so. Intensive efforts have been made in the last two decades to secure the remaining populations. However,

  • there are currently only two observations of this subspecies in iNaturalist (,
  • as far as I know the diet has not been studied beyond what Estes found in this report, and
  • to this day there has never been a study of the diet of H. n. variani in the dry season.

Also of special interest is the mention of geophagy ( at the bases of large mounds of macrotermitines (

The following excerpts, relevant to diet, are verbatim except for the clarifications and links I have inserted (in square brackets) and interspersed. References cited within these excerpts are:


Pages 5-6:

"There are three main vegetation types [in Luando Nature Reserve,], determined primarily by topography and drainage:

  • Brachystegia/Julbernardia woodland, on elevations and other well-drained sites. The greater part of the reserve consists of this woodland. Julbernardia paniculata, Brachystegia boehmi, Isoberlinia angolensis, B. spiciformis, and B. floribunda are the dominant trees, while a variety of other pinnately compound species of the Caesalpinioideae are common. Which species dominate varies according to position in the soil catena. For instance, B. floribunda tends to dominate on gravelly and rocky soils in the upper end of the catena, while Isoberlinia angolensis, B. ?longifolia together with three species of Uapaca [] are commonest in the ecotone between edaphic grassland and woodland. Large termite mounds, many supporting sizeable trees, are prominent features of the woodland.
  • Anhara grassland, equivalent to the dambos [] of Zambia, caused by seasonal waterlogging, interrupts and interdigitates with the woodland. The dominant grasses are Loudetia spp., though small sedges (especially Kyllinga spp.) are more abundant in many places than are grasses. The anharas are studded with grey conical and umbrella-shaped termite mounds [ and]. These provide slight elevations upon which trees and shrubs are able to gain a footing in an otherwise inhospitable environment.
  • Floodplain grassland bordering the Luando, part of the Cuanza [] and their major tributaries. Grasses grow taller and more luxuriantly here than on the anharas."


Kyllinga is now part of Cyperus (

Pages 11-12:

"The giant sable of the Quimbango region [] frequented woodland during the rainy season. The main reason for preferring woodland over anhara was long-ago deduced by Blaine (1922: 321): 'The undergrowth is light, consisting of little low seedlings of bush a few feet high, and a fine, soft, sparsely-growing grass, which is the principal food of the sable...The soil is a sandy loam enriched with leaf-mould, giving place on the dambos to the usual sun-baked knobbly grey clay, where a hard, coarse grass grows which the sable never seems to eat.' This statement is as true today as it was 50 years ago. The Loudetias which dominate the meadows are all wiry stems and no leaf - making them exceptionally good for thatching but useless for grazing (except in their youth, when sable eat a certain amount). In 72 observations of Herds A and C in which the habitat was specified, it was found, however, on the edge of an anhara or tree grassland 47 times (65 percent). Here again, the main reason is that their favourite grasses grow more luxuriantly here, where the ground stays moister than in the woodland without becoming waterlogged like the anharas. Thus the giant sable, like its counterparts in Kenya and Rhodesia, may be thought of as being largely an edge species...But during the rains, good grasses also grow luxuriantly on and around the termite mounds which are so abundant throughout the woodland. The way sable move from mound to mound is an outstanding characteristic of their feeding behaviour. Investigations of termite mounds have shown that they possess a higher content of humus, nitrogen, and colloidal matter than the surrounding soil, as well as a higher maximum water retaining capacity (Murray, 1938 in Glover [sic], 1964). Large termitaria also occur in the anharas, forming islands upon which grow many of the same grasses found in the woodland. These too are visited by sable, even when the surroundings are muddy or actually underwater, for they are not reluctant to venture on to such ground in order to reach an objective. Not only did they readily cross anharas during the rains, but Herd A regularly went out onto Congolo and Cibila anharas both to drink and to visit a number of different salt licks (characteristically found at the bases of termite mounds; samples have been collected for chemical analysis). On at least one occasion, the herd spent some time wandering about a flooded area while feeding upon the grasses growing on slight elevations - most of these being defunct termite mounds of a small type confined to the anharas. On the other hand, sable are only transient in such places; as a rule they frequent firm ground. In fact, after a heavy rainfall in the study area, it was predictable that Herd A would be found in the highest and driest woodland near the Camana picada [motorable track] until the water had drained off and sunk into the low-lying part. As the water table receded, the sable gradually moved back down the catena [,to%20accumulate%20near%20the%20bottom.], showing a preference for the grasses growing on soil that was still moist but firm enough so that their hooves did not sink in deeply. The apparent danger - of injury or increased vulnerability to predators - may deter sable from frequenting very soft ground, as an adult's foot may sink in as much as 45 cm (by actual measurement in a patch of loamy soil). The tendency to favour one part of the catena over another was also discernible on a seasonal basis. The highest ground, with gravelly soils and generally short grasses (except on the termite mounds) was most frequented during the heavy rains of February and early March. From mid-March to mid-April the rains failed. Within a fortnight, the grasses in the high woodland began to turn yellow, while the leaves of some herbs and trees turned yellow or red and began to fall. By that time, the herd had shifted its ground to the lowest woodland bordering the Cibila anhara where the water had been ankle-deep after the last big storm. Here, the general level of the grass was higher (almost 50 cm) with stands up to three metres tall on some termite mounds, and the pasture was as lush as ever. Then came a final week of rain during which the herd moved back to the high woodland, where the grasses quickly resumed growing. The existence of a catena in Herd A's home range is obviously of major significance in its distribution, for it enables the herd to find preferred habitat in one part or another under any given set of conditions."

Pages 13-14:

"The giant sable prefers the same types and selects many of the same species that members of other sable populations were seen to select, especially in Tanzania's Rungwa Game Reserve [], where habitat conditions are very similar...Thus such tufted perennials as Brachiaria, Digitaria, Panicum and Setaria spp. are universal favourites. In short, they prefer the best available pasture grasses; furthermore, they select each species at its tenderest and most nutritious stage of growth. A sable typically bites off the outer 15-30 cm of the plant and seldom crops closer than 20-30 cm. Larger, coarser grasses such as Tristachya superba and Hyparrhenia spp. are also taken as long as they remain tender, but the lower 50 cm or so of these plants may be left, whereas such feathery grasses as Themeda triandra and Hyparrhenia filipendula may be cropped to 10 cm or less. From superficial examination, it often appeared that a herd had specialised almost entirely on one or two different species for a period of a week or two. But whenever grazed plants were actually collected and compared, it turned out that a number of very similar-looking species had been selected. Usually ten or more species accounted for 90 percent of the plants in the sample; seldom did one species make up more than 25-30 percent of the total. The grazing calendar of the sable is closely tied to the phenology of the grasses...Each grass reaches maturity at a particular time, with the result that there is a regular succession of (apparently) dominant grasses, as one common species after another comes into flower. Thus two Digitaria spp. dominated the woodland in November and December, respectively, succeeded by a Tristachya sp. in February and an Andropogon sp. in March. On the anharas, which lagged behind the woodland pastures for some time, an Eragrostis sp. was the first to flower in November, followed by a different Tristachya sp. and finally by Loudetia spp. beginning the end of January. The last of all to mature were the very tall species such as Pennisetum purpureum and Hyparrhenia spp., of which at least 10 occur. Interestingly enough, they started to grow most vigorously after the rains ceased in mid-March, and appear to be largely confined to well-drained deep soils. They are most abundant along the roadside, where they form a narrow strip on either side, in abandoned fields, where tall Hyparrhenia form almost pure stands, and on termite mounds, especially those in the lower parts of the catena. Lately the sable have been seen to feed heavily in some of the flowering Hyparrhenias, but the very tall and coarse species that grow in the plantations and along the roadside are apparently only palatable in their early stages. Sable are also browsers. Considering the general lack of reliable information about this animal, it is remarkable that two of its favourite browse plants have been faithfully recorded by almost every person who has ever observed and written about it. Thus Statham (1922) reported that...Diplorhynchus condylocarpon...and...Dolichos sp. were of major importance in the sable's diet. Undoubtedly it was the local people who called attention to these plants, just as they pointed them out to us, along with a number of other plants that sable browse. In practically every case, observations have borne out their information, although so far we have not seen [Dolichos] eaten. In the case if Diplorhynchus, we have seen sable browsing this very common small tree in almost every area visited to date, and giant sable have been taking it in quantity since the beginning of the study. A low leguminous shrub, Mucuna stans, was equally heavily browsed by Herd B in November and December. For instance, of 75 plants examined in a place where the herd had been feeding, 45 had been browsed. It was one of the dominant shrubs in this part of the woodland, whereas Diplorhynchus was far commoner in the home range of Herd A, which fed on Mucuna stans only occasionally. It is worth noting that both species, the latter in particular, are abundant in abandoned cultivation. Of the dozen-odd other herbs and woody plants which the sable have been seen to browse in Luando, only three were heavily utilised. Early in the season, two succulent Commelina spp. were taken while in flower. Beginning in January, Julbernardia paniculata, the dominant tree, was browsed with increasing frequency. Lately, herds in both the study area and near Mulundo have been feeding heavily on a Blepharis sp., a herb with blue flowers and spiny bracts; last July sable in Victoria Falls National Park were observed eating the dried heads of B. bainesii. The actual percentage if the sable's diet that is made up of browse is unknown and of course variable. It seems unlikely, though, that browse ever accounts for more than 20 percent of the diet."

Tristachya superba:

Diplorhynchus condylocarpon:

Mucuna stans:

The following are spp. of Dolichos in the miombo biome:

Julbernardia paniculata:

Posted on 07 December, 2023 15:06 by milewski milewski | 23 comments | Leave a comment

08 December, 2023

An integrated interpretation of the diet and foraging behaviour of the sable antelope (Hippotragus niger)

The trophic ( ecology of the sable antelope (Hippotragus niger, - a ruminant combining glamour and vulnerability to extermination - has been studied intensively over the last half-century.

However, as far as I know, no author has yet provided a satisfactory overall interpretation - which I attempt in this Post.

The best summary so far published of the diet and foraging behaviour of this hippotragin bovid is that of Estes (1991, pages 123-124):

The sable antelope is "closely identified with the well-watered Miombo Woodland Zone...The most distinctively different race is H. n. niger...found south of the Zambezi...this race inhabits the driest savanna, undertakes seasonal movements of up to 50 km, and forms the largest herds (up to 200 head and sometimes even 300 in Zimbabwe)...The sable favours a mosaic arrangement of woodland and grassland. The woods have to be open enough to support an understorey of grasses, which are utilised in the rainy season. Sable herds range the open grasslands in the dry season in search of green plants, including the forbs and foliage that make up c. 20% of their diet. Termite mounds, which support lusher growth than the surrounding leached, ancient soil, have many of the grasses and browse plants they like best. Dry-season movements depend on the availability of water and food. Forage quality is in turn closely dependent on annual, manmade fires that burn off the tall, dead grasses within a month or two after the rains end. Greenflush comes up along the drainage lines with their heavier clay soils while the droughtier woodland soils remain blackened and lifeless until woody plants put out new leaves in the miombo spring, a good month before the rains begin, attracting the sable back to the woods. Sables regularly visit salt licks, typically situated at the bases of termite mounds; and where soils are particularly poor, they may visit the sites of old kills to chew bones, presumably to acquire calcium and phosphorus."

In a recent series of three Posts, I have revisited information on the diet of the sable antelope (

The following is my synthesis of the trophic ecology, based on a combination of integration and lateral thinking.


Hippotragin bovids are all adapted to trophic poverty. That is to say: in the context of ruminants in general, their habitats produce food in limited quality, or quantity, or a combination of these.

  • In the case of Hippotragus, the vegetation is copious (and luxuriant in the case of two subspecies of the sable antelope), but generally unpalatable owing to its fibrousness.
  • In the case of most spp. of Oryx, the vegetation is sparse albeit generally of good quality because the soils are fairly nutrient-rich.
  • In the case of Addax and Oryx gazella, there is a combination of sparse vegetation (owing to aridity) and generally nutrient-poor soils.

The sable antelope is, among all hippotragins, the species for which adaptation to poverty is least apparent.

Please consider the following:

The habitat of the sable antelope, although overlapping with that of Hippotragus equinus (, has generally the most copious (and thus fibrous) vegetation inhabited by any hippotragin species.

This is partly because H. n. variani lives under mean annual rainfall of as much as 1400 mm (



The various spp. of hippotragins span a wide range of climates, from desertic ( to mesic.

Of all hippotragins, it is the sable antelope that penetrates the rainiest climates. This is the only one of these spp. that

The main relevance w.r.t. diet and foraging ecology is that plant matter tends, other factors being equal, to be more fibrous, the rainier the climate.

This may help to explain why

RELATIONSHIP TO THE GEOGRAPHIC CATENA (,to%20accumulate%20near%20the%20bottom.)

The sable antelope tends to spend the wet season in woodland, and the dry season in vegetation in which trees and shrubs are relatively sparse. This is puzzling, based on the assumption that open vegetation is treeless mainly owing to a relative lack of water.

However, the puzzle is resolved by realising that dambos ( may be treeless owing to shortage of not water but rather certain nutrients. A lack of boron relative to other nutrient elements may militate against woody growth.

Because trees and tall shrubs demand more water than do grasses, the soils in dambos retain enough water in the dry season for some green growth of the grasses to continue in the dry season.


Hippotragins all eat mainly grasses. The sable antelope conforms to this generalisation.

However, dicotyledonous plants, ranging from foliar-spinescent herbaceous Acanthaceae (e.g. Blepharis bainesii, through leguminous lianes (e.g. Dolichos and Mucuna) to shrubs/trees, contribute significantly to the diet. This contribution is likely to be disproportionately great in terms of the supply of crucial micronutrients, particularly copper and cobalt (

Does the sable antelope differ from Hippotragus equinus in the extent/degree to which it takes dicotyledonous plants (

At the southern limit of its distribution, the sable antelope penetrated

Here, it may have found a niche by accepting grasses rejected by the various other ungulates. Evidence for this comes from a reintroduced population, which treats as a staple a species of grass (Chrysopogon serrulatus, ignored/avoided by other species including the plains zebra (


The sable antelope is unusual, among non-bovin grazers, in seldom attempting to reach ground level with its mouth.

By the same token, it seems not to have been recorded

  • foraging at the maximum height of its neck, let alone adopting any bipedal posture in foraging, or
  • using its horns to break down foliage, in the way recorded for certain tragelaphins.

There are several photos on the Web of the sable antelope grazing short, green grass. However, all are in zoos ( and


In the wild, the sable antelope, unlike various other ruminants, seems never to graze - let alone form - lawns (

Instead, this species takes grass

  • at considerable height above ground, and
  • in relatively large bites.

One lawn-forming grass is fairly frequently eaten by the sable antelope, viz. the cosmopolitan species Cynodon dactylon ( However, I assume that this occurs where the species has not been subject to lawn-formation, and has grown above 20 cm high.

The fact that the sable antelope - like all hippotragins - has scant relationship with lawns is consistent with its combination of

  • sparse populations, in which the number of individuals per unit area would be insufficient to maintain lawns in the first place, and
  • the relative lack of coexisting grazers, particularly in miombo vegetation.

The mouths of alcelaphins are adapted to grazing on lawns, in that the gape is so narrow that each bite is small and must be detached by the relatively weak pressure of the lower incisors against the toothless palatal pad. By contrast, in the sable antelope the gape is so wide that the animal can easily bite off substantial items with its sharp-edged premolars ( and

In the following, the premolars are the anterior-most cheek-teeth:

The following is a comparable view of the skull of Alcelaphus caama. The dentition of the upper jaw is similar to that of the sable antelope.

However, the alcelaphin is incapable of biting any item off by means of its premolars, because the tight skin at the junction of lips and cheek constrains both


In general among gregarious ruminants, there is a correlation between sexual dimorphism in size (of the body and the horns/antlers) and sexual segregation in foraging (

Hippotragins show minimal sexual dimorphism and minimal sexual segregation.

Among the hippotragins, the sable antelope is

  • the most sexually dimorphic species,
  • the only species in which adult females can readily be distinguished from adult males at some distance, and
  • the most gregarious species, given the aforementioned seasonal congregations of H. n. niger.

However, any differences in diet and foraging ecology between the sexes remain subtle enough that they have yet to be demonstrated.

The following excerpt from Estes and Estes (1970) seems relevant:

"Along the Zambezi River above Victoria Falls [in June-July 1969] most sable had dull, 'staring' coats...But adult males, inexplicably, looked as glossy as ever...The Combretum/mopane scrub grassland was absolutely infested with larval Matopos National Park, where tick birds have been virtually eliminated..., some sable were seriously infested...These were...the only other sable that appeared in generally poor condition...and had dull, staring coats (again excepting adult males) further resembled the Big Herd [mentioned above] in frequenting a home range of less than two square miles, and remaining on the same pasture day after day."

Estes and Estes did not offer any explanation for how the adult males, although visibly somewhat thin, managed to maintain the gloss of their pelage under stresses that affected females and juveniles more visibly.

Territoriality is less-developed in hippotragins than in alcelaphins, possibly because the environmental poverty of hippotragins means that home-ranges tend to be larger than can practically be patrolled by mature males. Furthermore, hippotragins tend not to form 'bachelor herds'.

I have the impression, based on the literature, that the sable antelope is the only strictly territorial species of hippotragin; and, even in this species, bachelor herds tend to be somewhat nebulous.


Fire, much of it anthropogenic, occurs routinely in the miombo biome, including the dambos (relatively treeless drainage lines subject to seasonal waterlogging).

In this loose sense, fire seems intrinsic to the foraging ecology of the sable antelope.

On one hand, the sable antelope is attracted to the post-fire green flush more than is the roan antelope.

On the other hand, the sable antelope is not as dependent on the post-fire green flush as much as is sympatric Alcelaphus lichtensteini ( is.

Please note that

  • the sable antelope, although presumably eating many of the same grasses as Lichtenstein's hartebeest, consumes grasses - plus sundry dicotyledonous plants - once they have grown >20 cm, and up to 1 m, high in the regenerative cycle associated with combustion; and
  • the large mounds of Macrotermes (, with which H. n. variani is particularly associated, tend to be exempt from fires that routinely sweep the matrix among the mounds.


The sable antelope occurs both patchily in the miombo biome, and somewhat beyond this biome.

Within the miombo biome, the species - more than H. equinus - may be at least indirectly dependent for its sustenance on the large mounds of termites, particularly fungus-culturing termites (Macrotermitinae).

The crucial trophic role of fungus-culturing termites is likely to be manifold, including the following.

Large mounds tend


In a sense, the whole of the miombo biome is anthropogenic, via a system of slash-and-burn cultivation (

This horticultural regime is

  • intense enough to be ecologically profound, but
  • scattered enough in space and time that an illusion of 'wilderness' is maintained.

The niche of the sable antelope can thus be seen as, in a sense, 'successional', rather than being extraneous to disturbance by humans.

However, the sable antelope has not been recorded foraging on domestic species of plants.

This perspective raises the following question:

Where the long-standing pattern of slash-and-burn cultivation has been discontinued in conservation areas, has the result - other factors being equal - been an increase or a decrease in the population densities of the sable antelope?

Posted on 08 December, 2023 22:46 by milewski milewski | 35 comments | Leave a comment

11 December, 2023

An index to my Posts on the bovid genus Hippotragus: the sable antelope (Hippotragus niger) and the roan antelope (Hippotragus equinus)



Posteriolateral view:

Ischio-abdominal pattern:

Adaptive radiation of dark flank-band:

Conspicuousness of prepuce:

Conspicuousness of tail:

Conspicuousness of ears:

Malar stripe:

Female self-advertisement:




Use of horns:

Caudal flagging:




Diet and foraging ecology:

Diet of subspecies H. n. variani in Angola:

Diet of subspecies H. n. niger in Zimbabwe:

Diet of subspecies H. n. roosevelti in Kenya:


Flehmen, compared to hartebeest:


Kenya (habitat of subspecies H. n. roosevelti):

Angola (including habitat of subspecies H. n. variani):

Botswana (habitat of subspecies H. n. niger):

Posted on 11 December, 2023 19:14 by milewski milewski | 0 comments | Leave a comment

16 December, 2023

Is the sable antelope the only ungulate - indeed mammal - that advertises its penis with black-and-white punctuation?

@dragonfyre @fabienterrade @lefebvremax @ldacosta @tonyrebelo @jeremygilmore @maxallen @paradoxornithidae @beartracker @tandala @dejong @zarek @jakob @jwidness @michalsloviak @oviscanadensis_connerties @davidbygott @karoopixie @christiaan_viljoen @henrydelange @botswanabugs @wynand_uys @ludwig_muller @marcelo_aranda @ptexis @douglasriverside @matthewinabinett @simontonge @alexdreyer @variani18 @nyoni-pete @bobby23 @magdastlucia @aguilita

In the sable antelope (Hippotragus niger,, the presence of the penis is visually unmistakable in adult males.

This is because the tip of the preputial sheath ( is covered with blackish hairs. This is offset by the adjacent surface of the belly, which is broadly white in crisp contrast with the dark of the flanks.

The following shows that the colouration in question is apparent - like an exclamation mark under the belly - even at some distance:

The preputial colouration seems congruent with the overall boldness, in dark/pale contrast, of the colouration of the whole figure. The pattern is part of the year-round masculine self-advertisement in the sable antelope.

This punctuation of the prepuce is the most reliable guide to the sex of the individual, in a species in which fully mature females can emulate males in all other aspects of colouration (

The preputial pigmentation facilitates the differentiation of the sexes in extant spp. of Hippotragus. This is true despite the remarkable emulation of other male features in females of these and other hippotragin bovids (

The following shows how easily mature females of the southern sable antelope (Hippotragus niger niger) can be distinguished from males, despite a lack of sexual dimorphism in the rest of the colouration:


At first consideration, it may seem unremarkable that a large mammal advertises its masculinity in this pointed way.

However, on closer examination it turns out that the sable antelope is likely to be unique in this respect.

It is true that the preputial sheath is also dark-tipped in the roan antelope (Hippotragus equinus, and and and

However, this is of limited conspicuousness ( and and, partly because the function of the pale pelage on the belly is categorically different.

In the roan antelope, the ventral surface of the torso is countershaded, in keeping with an overall postcranial inconspicuousness of the figure in full profile.

By contrast, in the sable antelope the same surface accentuates the boldness of the colouration, to the degree of qualifying as a bleeze (

The crucial difference, then, between the sable antelope and the roan antelope is that only in the former does the preputial contrast form part of a bleeze.

Furthermore, the sable antelope exceeds the roan antelope (and all other hippotragins) in sexual dimorphism. For example, can readers tell the sex of the following specimen of the roan antelope:

In the remaining two genera and six spp. of hippotragins, there is only a trace of the pattern.

In the gemsbok (Oryx gazella), there is merely a hint of emphasis ( and

Among alcelaphin bovids, the bontebok (Damaliscus pygargus pygargus) resembles the sable antelope in the darkness of the flanks and the crisp demarcation of a conspicuous white belly ( However, neither this nor any other alcelaphin shows any emphasis of the prepuce.

Among reduncin bovids, the most bodly-coloured forms are

However, once again, in both cases, the prepuce is not accentuated, so that the presence of a penis is not advertised.

Among rupicaprin bovids, some views of chamois (Rupicapra spp.) show a narrow preputial tassel ( and and and and and

Furthermore, the northern chamois (Rupicapra rupicapra, tends to be conspicuously dark-and-pale in winter pelage (
and and

However, the tassel in question

Bisons - which are bovin bovids - are another example of advertisement of the penis by means of a tassel ( and Furthermore, this can be a conspicuous part of the dark ventral silhouette of the figure.

However, in Bison there is no dark/pale contrast in the ventral pelage, suggesting that the main mode of advertisement, as in Rupicapra, is olfactory.

In African buffaloes (Syncerus, and, the tassel is sparse, but the preputial sheath is associated with a small abdominal dewlap.

When adult males of Syncerus micturate, this pendulous structure tends to twitch visibly. However, there is no dark/pale accentuation.

Turning now from the family Bovidae to the family Cervidae:

A preputial tassel occurs in some deer, e.g. the fallow deer (Dama dama, and and In the rutting season, this conspicuously twitched in masculine display (


  • the darkness of this tassel seems to be owing to staining by urine and/or secretions, rather than pigmentation (, and
  • the function of the tassel seems to be mainly olfactory.

In the red deer (Cervus elaphus, and and, the prepuce has similar position and twitching to that in the fallow deer. However, the tassel is too short to be conspicuous.

In the wapiti (Cervus canadensis, and, the prepuce is located in a relatively anterior position, as in various bovids.

However, there is no preputial tassel, and any visual display is merely a matter of subtle twitching. The following ( shows this as the animal micturates on itself for olfactory advertisement.


Several spp. of primates have conspicuous colouration on the penis and/or prepuce ( and and and and

However, in primates,


A distinctly dark-pigmented but short-haired preputial tip seems to be unique to Hippotragus.

Even in this genus, it may have been absent in the recently-extinct bluebuck (Hippotragus leucophaeus,

The most convergent species, in this respect, is the northern chamois. This rupicaprin also resembles the sable antelope in having

  • sharp horns, designed for inflicting injury rather than as a form of adornment for ritual sparring,
  • conspicuously dark colouration overall, albeit only in winter,
  • conspicuously dark-and-pale markings on the face, reminiscent of aposematic colouration,
  • minimal sexual dimorphism in horns and colouration,
  • retention of adolescent males in the maternal group up to the age of 2-3 years, and
  • a pugnacious demeanour relative to most other ruminants.


The distinctive genital advertisement of the sable antelope has been in plain view since European explorers first encountered the species.

However, nobody seems to have noticed that this feature is functionally unique to this species.

This may be because such an appreciation would depend on

  • applying a converse approach to the prevailing reductionism in Zoology, and
  • broadening the context, to encompass the bewildering diversity of other ungulates, and mammals in general.

It is only when one stands back far enough to combine detailed scrutiny with a panoramic view of hippotragins, bovids, ruminants, ungulates, and mammals that the extreme position of the sable antelope becomes fully apparent.

Posted on 16 December, 2023 04:03 by milewski milewski | 23 comments | Leave a comment

21 December, 2023

What is the location of this picture worth a thousand words?

@pachogut @joachim @ivanparr @misumeta @paddy18 @nyoni-pete

Please scroll to third large photo in

Who knows Chobe National Park ( well enough to pinpoint this precise location?

The most similar that I have found in iNaturalist is

The photo in question is remarkable for several reasons.

Firstly, the horizontal interruption of the water creates an initial illusion of two different photos, one above the other.

Secondly, in this general area, the sable antelope penetrates extensive treeless grasslands, despite being a species dependent on the edges of woodlands.

Thirdly, it is noteworthy to see the sable antelope near the western wildebeest (Connochaetes taurinus mattosi) and large groups of the plains zebra (Equus quagga chapmani). Typically, the sable antelope shuns congregations of 'plains game'.

@moxcalvitiumtorgos @rion_c
Could you please identify the waterfowl in the photo in question?

Posted on 21 December, 2023 20:58 by milewski milewski | 3 comments | Leave a comment

Surprising adaptive radiation of the dark-pigmented flank-band in hippotragin bovids

@michalsloviak @ldacosta @paradoxornithidae @oviscanadensis_connerties @capracornelius @maxallen @christiaan_viljoen @botswanabugs @beartracker @dejong @aguilita @tonyrebelo @jeremygilmore @tandala @jwidness @jakob @felix_riegel @ludwig_muller @davidbygott @saber_animal @matthewinabinett @chewitt1 @calebcam @johnnybirder @wnyjw @simontonge @ptexis @variani18

A dark-pigmented flank-band ( occurs in various tribes of Bovidae (

This feature is most obvious in gazelles (

However, it occurs also, in subtle and variable form, in hippotragin bovids (

How does a dark flank-band function, as a product of natural selection?

(As a matter of contemporary interest, this is the unsatisfactory answer given today by Artificial Intelligence, in the form of com:


In the adaptive colouration of ruminants, the basic dichotomy is between enhancing inconspicuousness on one hand, and enhancing conspicuousness on the other.

Certain species, inhabiting dense vegetation, are adaptively inconspicuous to onlookers (particularly predators) by virtue of either

By contrast, certain other species of ruminants, inhabiting open vegetation, are adaptively conspicuous - a phenomenon underplayed in textbooks.

This seems to result from the following cost-benefit situation:

The lack of cover means that the animals are inevitably apparent to onlookers (particularly predators). So, instead of attempting to evade detection, they rely instead on gregarious vigilance and cursorial escape. Accordingly, 'plains game' optimise for ease of intraspecific communication - particularly in aid of group-cohesion and the advertisement of sociosexual status - at the scale of the whole figure.

A dark flank-band can potentially serve either conspicuousness or inconspicuousness. If bold enough, it might make the whole figure obvious. In a more subtle configuration, it might function more like tiger-striping, tending to hide the figure against a somewhat complicated background.

Given the above conceptual framework:

How can we interpret the various configurations of the dark flank-band that have arisen in hippotragins?

This tribe is particularly intriguing, because - even more than in gazelles - the feature of colouration in question has proven to be surprisingly plastic in evolutionary terms.

Among hippotragins, the dark flank-band can be classified as follows:

  • categorically absent: Hippotragus equinus, Hippotragus leucophaeus, and Addax nasomaculatus (summer pelage);
  • so poorly-developed as to be irrelevant w.r.t. the relationship to predators: Oryx leucoryx, Oryx dammah, and Oryx callotis;
  • sufficiently well-developed to aid overall conspicuousness, in divergent ways: Oryx gazella vs Oryx beisa; and
  • subsumed into a clear-cut distinction between relatively dark flank and pale ventral pelage on the torso: Hippotragus niger and Addax nasomaculatus (winter pelage).

In no species of hippotragin is the dark flank-band as conspicuous as in typical gazelles. This is because it is situated too low (i.e. too far in a ventral direction) on the torso for either its darkness or its offsetting by the whitish, ventral to it, to raise it to visual prominence.

The species in which the dark-pale contrast on the lower flank is most conspicuous is H. niger, in which the flank-band is hardly recognisable as such.

This contrast is so strong in H. niger that it clearly enhances overall conspicuousness ( This applies even to females of Hippotragus niger roosevelti, which always lack the conspicuous overall darkness of males.


In order to illustrate and elaborate the points made above:
first, I present illustrations according to the categorisation above, which crosses generic boundaries, and
second, I present illustrations on a species-by-species basis, in every case choosing views in full profile.











Now, turning to a species-by-species account:


This is the only extant species of hippotragin in which there is hardly any trace of a dark flank-band ( and and and and

The countershading on the torso in H. equinus conforms to adaptively inconspicuous colouration.

However, even in this species, some individuals (particularly in H. e. koba) retain a relictual flank-band ( and and and and


Please see illustrations in

There is consistently, in every adult individual of this species, a conspicuously clear-cut boundary between the white pelage on the ventral surface of the torso, and the adjacent ground-colour.

The existence of a flank-band in H. niger niger is revealed ontogenetically.

This is illustrated in Fig. 13 E on page 153 of Grobler (1980, file:///C:/Users/Antoni%20Milewski/Downloads/Body_growth_and_age_determination_of_the_Sable_Hip.pdf).

Juveniles, by seven months old ( and and, tend to shed the natal pelage in a horizontal band between the medium-tone pelage of the torso and the ventral whitish of the abdomen. The new hairs are precocially dark.

The ground-colour on the flanks tends to be dark, even in females of a subspecies (H. n. roosevelti) in which females never turn as dark as adult males (


In the absence of information for this extinct species (, I assume similarity to H. equinus.

However, mature males are reputed to have been pale enough to resemble pallid spp. of Oryx.


The dark flank-band is faint in most individuals ( and and and

The maximum development is shown in the following, unusual individual (

In O. leucoryx, the whole torso is extremely pale, making the figure extremely conspicuous ( The flank-band is thus functionally redundant, in convergence with the summer pelage of Addax nasomaculatus.


The following ( and and and give the impression that a flank-band is absent in Oryx dammah.

However, in many individuals the feature remains in vestigial form, particularly just posterior to the elbow and near the knee ( and and and and and

In O. dammah, the flank-band is redundant, because the whole torso is adaptively conspicuousness by virtue of large-scale pallor on the flanks and scapulae (, contrasting with relative dark on the forequarters (


The dark flank-band is fairly well-developed in most individuals (

However, it confers negligible adaptive conspicuousness, because the ventral surface of the torso is hardly paler than the flanks ( and

Instead, it is plausible that, in O. callotis, the flank-band tends to reduce conspicuousness, by means of disruptive colouration ( and and and

Please see


In this species, the flank-band is narrow (

However, it is dark enough to be conspicuous owing to its contrast with the mainly pale pelage of the torso ( and first photo in

Of all hippotragins, O. beisa most resembles the pattern epitomised by gazelles. However, it falls short of most spp. of gazelles, in terms of conferring graphic conspicuousness in full profile ( and


In this species, the dark flank-band is consistently dark, and broader than in any other hippotragin ( and and

The following ( is particularly instructive.

Note the conspicuousness, even at distance, of a species of gazelle, namely Antidorcas marsupialis, in the background. This is owing to not only the presence of a dark flank-band in this gazelle, but more importantly the high position of this band, allowing the ventral white to catch sunlight in an eye-catching way.

The important inference is that the flank-band of O. gazella does not function in the same way. Instead, when viewed in full profile, it seems to serve mainly to provide dark underscoring to the medium tone of the torso (

What this amounts to is a particularly odd permutation of colouration ('anti-countershading') in a large mammal, as follows:

The white ventral panel - with its intrinsic potential for either countershading or highlighting - remains fully intact. However, it is overridden by the 'false-shading' effect of the relatively ventrally-located dark flank-band.

Thus, my interpretation of the function of the flank-band is that it enhances conspicuousness, in contrast to the closely-related O. callotis, and in a different way from the closely-related O. beisa.


The following ( and show the absence of pattern on the flank in summer pelage.

In A. nasomaculatus, a flank-band is, in a sense, redundant, because the pallor of the whole torso is already extremely conspicuous.

The following ( and show how crisp the distinction can be, in winter pelage, between the medium-tone of the flank and the white of the belly.

This feature is adaptively ambivalent. This is because


A principle in adaptive colouration, underplayed in the literature, is that a given feature of design can have different - even contrary - effects depending on 'design-context'.

For example, the same band/stripe/panel, located in the same position on the figure, can have opposite effects, according to other design-features around it and elsewhere on the figure.

The following are two examples of this principle.


The belly is whitish/white in both Oryx beisa and Oryx gazella (as in most other hippotragins, as well as most gazelles). However,

  • in O. beisa the ventral whitish tends to offset the (narrow) dark flank-band, enhancing conspicuousness, whereas
  • in O. gazella the ventral white effectively 'disappears'; the (broad) dark flank-band prevails in darkly defining the ventral silhouette of the figure, thus eclipsing the white below it in plain sight.


Please closely examine the following of O. gazella ( and H. niger (

In both cases, there is a distinct boundary-line running from the elbow ( and to the stifle-fold ( and

The important differences are that, in O. gazella

  • the dark lies ventral to this boundary, whereas in H. niger the dark lies dorsal to this boundary, and
  • the white of the belly is restricted inconspicuously to the shaded ventral surface, whereas in H. niger the white of the belly extends conspicuously on to the sunlit ventral part of the flank.

My interpretation is that a single ancestral boundary, between a dark flank-band and a white belly, has evolved contrarily in these two spp., as follows:

  • in O. gazella, the shift of the flank-band in a ventral direction has given it a function of conspicuously dark underscoring of the torso - which can be thought of as 'anti-countershading', whereas
  • in H. niger, the shift of the flank-band in a dorsal direction (together with its seamless blending with the ground-colour on the flank) has given it a function of conspicuously pale underscoring of the torso.

By the same token, a single ancestral feature, viz. white ventral countershading, has become redundant in O. gazella, whereas it has become the most noticeable feature on the whole torso in H. niger.

In summary:

In hippotragins, adaptive radiation in the patterns studied here has arisen

  • within a given genus, and even
  • within a single 'superspecies', consisting of O. gazella, O. callotis, and O. beisa.

This radiation has been accomplished not so much by defying phylogenetic constraint as by subtlely reconfiguring already existing features.

Also see

Posted on 21 December, 2023 23:49 by milewski milewski | 19 comments | Leave a comment

25 December, 2023

Has the post-withers mane-tuft of Hippotragus evolved in mimicry of oxpeckers (Buphagus)? part 1

@tonyrebelo @jeremygilmore @beartracker @paradoxornithidae @dejong @zarek @matthewinabinett @christiaan_viljoen @henrydelange @douglasriverside @tandala @oviscanadensis_connerties @maxallen @michalsloviak @jwidness @davidbygott @ludwig_muller @ptexis @botswanabugs @aguilita @marcelo_aranda @bobby23 @jakob @dinofelis @capracornelius @pmeisenheimer @brenainn @nyoni-pete @richardgill @i_c_riddell @koenbetjes @joseph103 @elisebakker @nickleggatt @lallen

Here are introductory images: and

This is the anatomical location of the withers:

Hippotragus spp. ( are attractive to oxpeckers (Buphagus spp., and

It is obvious that these birds often perch just posterior to the withers ( and and and and and and and and

However, here is something odd.

In the following of Hippotragus equinus, how many individuals are perching just posterior to the withers? (

The answer is two. So, what is the third object?

The answer is: a special tuft of the mane, which seems to have evolved to attract oxpeckers - somewhat like a decoy on a pond attracting ducks - in this genus of hippotragin bovids.

Now, please closely examine the following ( What do you see: bird(s), or mane-tuft(s)?

How about the following ( and


The mane in H. equinus is

The post-withers mane-tuft grows so promptly that it rivals the horns in length in small juveniles ( and and

The following shows the post-withers mane-tuft from behind: and

The West African subspecies, Hippotragus equinus koba, is extralimital to one of the two spp. of oxpecker, namely Buphagus erythrorhynchus ( and

In this subspecies, the post-withers mane-tuft may be hardly noticeable in adults ( and and and and

However, it remains present ( and and and


Hippotragus niger also shows a post-withers mane-tuft ( and and and

The following ( shows the size of the post-withers mane-tuft relative to Buphagus erythrorhynchus, the smaller-bodied of the two oxpeckers.

However, the feature in question is less discrete than in H. equinus.

This is mainly because, in H. niger, the mane is


In H. niger, as in H. equinus, the mane - including the tuft in question - is extremely precocial ( and

Infants of H. niger:

Juveniles of H. niger: and

A noteworthy aspect of the development of the mane in H. niger is that

This differentiation by means of pigmentation, as opposed to an actual gap in the mane, may apply even to adult males (


The post-withers mane-tuft (or dark pigmentation to the same effect) remains prominent despite the lowering of the neck in foraging.

The anatomical position thus potentially enhances the value of this feature in attracting oxpeckers.

This applies to both spp. of Hippotragus, as shown in the following:


second photo in


to be continued in

Posted on 25 December, 2023 06:29 by milewski milewski | 41 comments | Leave a comment