joulukuu 8, 2023

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

The diet and foraging ecology of the sable antelope (Hippotragus niger, - a ruminant combining glamour and vulnerability to extermination - have 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 trophic ( ecology 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, based on a combination of integration and lateral thinking.

Relationship to phylogeny:

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 (


Relationship to distinction between grazing and browsing:

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 (

Relationship to height above ground:

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.

Relationship to the geographical 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 nutrient. A lack of boron relative to other nutrient elements may militate against woody plants.

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.

Relationship to growth-form of grasses:

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.

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 (

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

Relationship to sexual segregation:

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.

Relationship to climate:

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

Of all the species, it is the sable antelope that penetrates the rainiest climates, and the only one that forages, in places, at the edge of rainforest ( and

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 fire:

Fire, much of it anthropogenic, is of routine occurrence 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.

However, this species is not particularly attracted to, or dependent on, the green flush immediately post-fire, in the way that sympatric Alcelaphus lichtensteini ( is. Although presumably eating many of the same grasses as this hartebeest, its niche is to consume them - plus sundry dicotyledonous plants - once they have grown >20 cm, and up to 1 m, high in the regenerative cycle associated with combustion.

Furthermore, 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.

Relationship to termites:

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

Relationship to horticulture:

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

Julkaistu joulukuu 8, 2023 10:46 IP. käyttäjältä milewski milewski | 28 kommenttia | Jätä kommentti

joulukuu 7, 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:

Julkaistu joulukuu 7, 2023 03:06 IP. käyttäjältä milewski milewski | 23 kommenttia | Jätä kommentti

joulukuu 4, 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


Julkaistu joulukuu 4, 2023 04:12 AP. käyttäjältä milewski milewski | 8 kommenttia | Jätä kommentti

joulukuu 2, 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

Julkaistu joulukuu 2, 2023 06:59 AP. käyttäjältä milewski milewski | 4 kommenttia | Jätä kommentti

joulukuu 1, 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:

Julkaistu joulukuu 1, 2023 05:44 AP. käyttäjältä milewski milewski | 33 kommenttia | Jätä kommentti

marraskuu 28, 2023

Flora and vegetation of Shimba Hills National Reserve in coastal Kenya, including a description (1969) by Richard Estes

@dejong @richardgill @zarek @dianastuder @kai_schablewski @peakaytea @marcoschmidtffm @wasinitourguide @troos @craigpeter @bartwursten

Also see



The following is the main reference to the flora of Shimba Hills National Reserve:[5:ACOTPO]2.0.CO;2.short[5:ACOTPO]2.0.CO;2/ANNOTATED-CHECKLIST-OF-THE-PLANTS-OF-THE-SHIMBA-HILLS-KWALE/10.2982/0012-8317(2005)94[5:ACOTPO]2.0.CO;2.short

The following is a thesis on the topic of the effects of Loxodonta africana on the vegetation:

The following publication is also relevant:


The following is an electronic record of the writings - now at risk of permanent loss in paper form - of a noteworthy researcher ( more than half a century ago.

I refer to pages 4-6 in Estes, Richard D and Estes, Runhild K (1969) The Shimba Hills sable population: First progress report. National Geographic Society, hippotragine antelope study.

'Anon. 1968', 'Glover', and 'Makin' refer to the following:

  • Anon. (1968) A reconnaissance inventory survey of the indigenous forest areas of Kenya. Part 2: Shimba Hills sampling unit. Spartan Air Services Limited. Ottawa, Canada. 59 pages.
  • Glover P E (1969) Report on an ecological survey of the proposed Shimba Hills National Reserve. East African Wildlife Society. 148 pages.
  • Makin J (1968) The soils in the country around Shimba Hills Settlement, Kikoneni and Jombo mountain. Soil Survey Unit, Department of Agriculture, Kenya.

In the following verbatim transcript, I have updated and corrected the scientific names.


[start of verbatim transcript]

"The flora of the Shimba Hills is rich and varied. Glover collected over 1000 species in four months. An inventory of trees found in forest reserves (Anon., 1968) lists 109 species of trees.

The Forest Department 1:50,000 map..., prepared from aerial photographs taken in 1964, distinguishes five different vegetation types including...pine plantations. Glover classifies the vegetation into five main types (not counting the plantations) and over 10 subtypes. The types shown on the map are listed below, with brief descriptions of Glover's main subtypes and the commonest species.


Glover distinguishes three subtypes:


A fairly dense woodland 30-40 feet high with an understorey. This type is common in unburnt, drier areas of the coastal hinterland south and west of the Shimba Hills, but is confined mainly to drainage lines and the northwestern tip of the reserve. A Manilkara ( is often the dominant tree, with Elaeodendron schweinfurthianum (, Searsia natalensis (, Antidesma membranaceum (, Apodytes dimidiata (, Zanthoxylum holtzianum (, Diospyros loureiriana (, etc.


More open, fire-resistant secondary bush has invaded extensive areas of formerly open grassland. The commonest trees and shrubs are Tetracera boiviniana (, Securidaca longipedunculata (, Rourea coccinea ssp. boiviniana (, Ochna purpurea (, Ozoroa mucronata (, Stereospermum kunthianum (, Ormocarpum kirkii ( and Dichrostachys cinerea (

'Sagebrush': Another type of invading woody growth, composed of Vernonia zanzibarensis ( and Lantana camara ( is popularly referred to as 'sagebrush'. It forms a dense low shrubby growth which infests a considerable part of the grassland, especially the Forest Department's plantations. While the Lantana is an exotic, Glover points out that Vernonia infestation represents a normal stage in the succession back to forest. As far as is known, neither is used by herbivores, although birds eat the fruits - and spread the seeds - of the Lantana. Both species are vulnerable to fire.


The origin of the Shimba Hills grasslands is indeterminate. There is some evidence, in the form of truncated soils, that they represent old cultivation sites maintained by fire, rather than edaphic grasslands created by seasonal waterlogging (Makin; Glover). The invasion of bush and sagebrush in the absence of burning bears out the view that Shimba grasslands are a fire subclimax.

The grassland consists mainly of tufted perennials, separated by bare ground; basal cover averages probably less than 5 percent. While there are many species, tall stalks of Hyparrhenia filipendula ( and Hyperthelia dissoluta ( appear dominant following the long rains unless burnt off during the dry season. Andropogon spp., especially A. dummeri [now synonymjsed with the following sp.] and A. schirensis (, are co-dominant and may actually be more plentiful though less conspicuous. In Makin's (p. 14) view, Andropogon is an 'unpalatable and poorly nutritious grass which characterises burnt-over and infertile soils.' This genus is nevertheless heavily utilised by sable [Hippotragus niger roosevelti] in most of the areas we have investigated. A far more unpalatable grass, which grows in widely separated clumps and dominates on gravelly slopes, is Trachypogon spicatus ( ); neither it nor Cymbopogon caesius ( ('pepper grass') was ever seen to have been grazed.

The lushest pastures are to be found on the edges of the copses, upon old termite mounds, and growing in depressions. Here Megathyrsus maximus (, ...Digitaria milanjiana (, including D. mombasana), Urochloa brizantha (, and Setaria trinervia ( grow most abundantly, along with Hyparrhenia filipendula. Other common constituents of the open grassland include Eragrostis spp. and Ctenium concinnum (

In places, especially on ridges, the open grassland is dotted with single trees or clusters of doum palms, in particular the symmetrically branched Hyphaene coriacea ("

[end of verbatim transcript]


Julkaistu marraskuu 28, 2023 01:03 AP. käyttäjältä milewski milewski | 7 kommenttia | Jätä kommentti

marraskuu 25, 2023

Diet of the sable antelope, part 1: Hippotragus niger roosevelti, with special mention of osteophagy

@paradoxornithidae @dejong @matthewinabinett @jakob @jwidness @simontonge @tandala @ldacosta

In the late 'sixties, the late Richard Estes ( spent 10 weeks in the Shimba Hills in coastal Kenya. The dates were 17 Oct.-8 Dec. 1968 and 1-14 March 1969.

His purpose was to study a rare and threatened subspecies of large bovid, namely the eastern sable antelope (Hippotragus niger roosevelti,

Richard Estes was, at the time, an authority on the western white-bearded wildebeest (Connochaetes mearnsi), and he went on to become the global authority on the sable antelope.

The eastern sable antelope was originally restricted to a limited strip of coastal East Africa, straddling the border between Kenya and Tanzania.

Its habitat was the northernmost, attenuated form of miombo woodland (, in which only one species of Brachystegia persists under the equatorial regime of bimodal seasonal rainfall.

Estes undertook this study nearly 60 years ago. At that time, the eastern sable antelope still remained in small numbers on the coastal plain in Kenya, in attenuated woodland of Brachystegia spiciformis ( and Afzelia quanzensis (, and at the edges of fire-free forest containing Manilkara and Diospyros. These populations at low altitudes, which Estes did not field-study, have since been exterminated.

The species has survived in Kenya only in the Shimba Hills. Here, the vegetation ( is a picturesque forest/savanna mosaic, only vaguely related to the northernmost miombo woodland.

The Shimba Hills were protected, before Estes' study, mainly for the purposes of watershed and forestry (with part of the area cleared for plantation of Pinus). The National Reserve was designated in 1968 ( and

The main purpose of this Post is to record, electronically, previously unpublished information that risks being lost to Science with the passage of time.

In this, part 1, the topic is the diet of the eastern sable antelope in the Shimba Hills.

My reference (xeroxed) is:

*Richard D Estes and Runhild K Estes (1969) The Shimba Hills sable population. First progress report. National Geographic Society, hippotragine antelope study.

The above report includes data from:

+Table 15 in Glover P E (1969) Report on an ecological survey of the proposed Shimba Hills National Reserve. East African Wildlife Society. 148 pages (as referred to in the above report). This study was made in March through May 1968.

In the following dietary list (as well more generally as in all three parts of this series of Posts), I have updated the species-names, several of which have been revised/synonymised since 1969.



*Cyperus hemisphaericus


*+Andropogon schirensis
eaten intensively in October and March

*+Ctenium concinnum

+Cymbopogon caesius

*+Digitaria milanjiana
eaten intensively in October and November

*+Diheteropogon amplectens

*Eragrostis perbella

+Eragrostis racemosa

*Hylebates chlorochloe

*+Hyparrhenia filipendula
eaten intensively in October and November

*+Hyperthelia dissoluta

+Megathyrsus infestus

*+Megathyrsus maximus
eaten intensively in November and March

*+Panicum trichocladum

*Paspalum orbiculare

*Setaria parviflora

*Setaria sphacelata
eaten intensively in March

*+Setaria trinervia (possibly synonymous with sphacelata)

+Sporobolus pyramidalis

*Sporobolus sp.

*+Urochloa brizantha
eaten intensively in November and March

*unidentified grass, possibly Pennisetum sp.
eaten intensively in November



*Justicia sp.


*Crotalaria emarginata

*Galactia argentifolia



*Rourea coccinea ssp. boiviniana


+Albizia adianthifolia

+Albizia gummifera


*+Securidaca longipedunculata


+Ximenia caffra

The following excerpts from the text in Estes and Estes (1969) are relevant to diet.


Pages 9-10:

"The sable is primarily a grazer on grasses of medium height, preferring the greenest and tenderest available plants. The Longo Magandi herd often specialised on one or two common grasses for a few days while the plants were at the preferred stage of growth, changing to others when the first ones became a little taller and coarser. Plants were usually not grazed shorter than about four inches. Two areas that were burnt in November and December were unutilised by sable until the leaf table exceeded six inches, although tall unburnt grassland was the only alternative. However, the unburnt grassland offered an understorey of green grass. The usual grazing method is to gather in a clump of blades with dexterous lip movements, then to bite off and chew a length of up to a foot...Generally speaking, the sable grazed most intensively around the edges of the copses, in hollows and on termite mounds in open grassland - i.e. in the places where the lushest, tenderest grasses grow...[several] of the grasses, which grow most abundantly in these situations but are not among the commonest grasses, were heavily grazed by sable so long as they were green and young: Megathyrsus maximus, Digitaria milanjiana, and Urochloa brizantha. An unusual habit of Shimba Hills sable is bone-chewing. It was observed on 30 different occasions, and appeared to be a practice indulged in by all herd members. It was usual for an animal to spend up to half an hour chewing a bone, meanwhile frothing at the mouth, and even to transport small pieces from one place to another when the herd moved. The sites of an elephant and of a buffalo skeleton were among the places most frequently visited by the Longo Magandi herd. At those places animals were seen apparently seeking pieces of bone to chew. Long bones were evidently preferred, but probably because few remained at these sites, sable were also seen to chew pieces of pelvis and even vertebrae. Glover also comments upon bone-chewing behaviour. The pronounced deficiency of calcium and phosphorus in Shimba Hills soils is a probable explanation. Yet the sable and other wildlife had failed to discover salt and bone meal put out on a cleared piece of ground the previous November by the following March. Although it was sited near a route not infrequently used by the sable, apparently it remained undetected. The obvious solution would be to establish a lick at one of their 'bone yards'."

Page 6:

"The grassland consists mainly of tufted perennials, separated by bare ground; basal cover averages probably less than 5 percent. While there are many species, tall stalks of Hyparrhenia filipendula and Hyperthelia dissoluta appear dominant following the long rains unless burnt off during the dry season. Andropogon spp., especially A. dummeri and A. schirensis, are co-dominant and may actually be more plentiful though less conspicuous. In Makin's (p. 14) view, Andropogon is an 'unpalatable and poorly nutritious grass which characterises burnt-over and infertile soils.' This genus is nevertheless heavily utilised by sable in most of the areas we have investigated. A far more unpalatable grass, which grows in widely separated clumps and dominates on gravelly slopes, is Trachypogon spicatus []; neither it nor Cymbopogon caesius was ever seen to have been grazed."

For the crucial role of mineral nutrients in the diet and drinking water of the sable antelope, please also see

to be continued in

Julkaistu marraskuu 25, 2023 04:50 IP. käyttäjältä milewski milewski | 5 kommenttia | Jätä kommentti

marraskuu 24, 2023

The morphlings versus the axolotls (how frogs have warped tadpoles into new shapes and sizes), part 3

...continued from

Large toads have tadpoles no longer than about 3 cm, which metamorphose into small ‘adults’ with snout-vent length not much more than 1.5 cm (and in some cases, I gather, as little as a third of this).

By contrast, the American bullfrog (Lithobates catesbeianus,, which is about the size of a large toad in maturity and is probably the largest non-toad frog in North America, has tadpoles up to 17.7 cm long. I have not found data on snout-vent length at metamorphosis but if the tadpole is >15 cm then presumably the frog is initially at least 5 cm long, severalfold the corresponding size in toads.

The metamorphs of L. catesbeianus can weigh 5 g, compared to <0.05 g in the case of bufonids with similar mature sizes. That’s a difference of two orders of magnitude in body mass at the stage of metamorphosis.

I think it’s safe to say that in most comparisons of bufonids with ranids of similar mature body mass, we can expect a difference of an order of magnitude in body mass at metamorphosis.

Furthermore, ranids such as Lithobates seem to be a bit like centrolenids, in retaining more of the tail at metamorphosis (when the animal leaves the water) than is true of most families of frogs. Bufonids don’t seem to go in for the retention of a residual tail at all.

So typical toads and typical frogs (ranids, so familiar in Europe and North America, although absent from South Africa where their place is taken by pyxicephalids) are similar in their commonness and fecundity, but differ in their development: bufonids have morphlings whereas ranids do not.

The following illustrations show the body sizes relative to human figures for scale.

The species illustrated is the natterjack toad (Bufonidae: Epidalea calamita, of Europe, but the body sizes and shapes are typical of many bufonids including Sclerophrys pantherina.

The natterjack toad is about average size for a toad, usually about 7 cm snout-vent length in maturity. The tadpoles, which complete their growth within two months, are small and this toad metamorphoses at about 0.7 cm snout-vent length.

Initially the morphlings (which are diurnal, presumably to avoid being cannibalised) are easily mistaken for invertebrates in the poolside herbage. The morphlings are so small relative to the fully mature animal that they take 3-4 years to reach sexual maturity.

The point of all of this is that toads typically metamorphose at remarkably small body size, which means that their life history can best be understood by dividing it into not just the three stages normally described for amphibians, viz eggs, larvae, and adults, but rather into four stages: eggs, tadpoles, morphlings, and adults.

The morphling can be thought of as an adult at larval size, and the development of toads can be interpreted, in a sense, as peramorphic – although I’ve never seen this suggested in any literature or anywhere on the internet.

Bufonidae: Epidalea calamita: mature individual:

Epidalea calamita morphling:

Epidalea calamita morphling:

The following reference invokes peramorphosis in frogs of the family Ceratophryidae ( From the abstract it’s not clear what the basis of peramorphosis is.

The ‘early onset of metamorphic transformations’ mentioned in the abstract is indeed what peramorphosis is all about, but the features concerned in this case seem too subtle or obscure to be specified in the abstract. So I’ll have to delve into the body of the paper itself.;jsessionid=0FB2DFDE4A06FDA17DBD9C02A397C7C9.f03t02?deniedAccessCustomisedMessage=&userIsAuthenticated=false

I assume that the lungs of toads only develop at or after metamorphosis (?known as long ago as 1931 when Noble wrote his book about amphibians).

However, it’s worth noting that in many other families of frogs the lungs start to develop well before metamorphosis, along with the developing legs.

This means that the later stages of the tadpole already possess, and use, lungs in many frogs as well as in the salamanders.

Toads seem to be an exception, which makes sense to me in view of the tiny size of the toad tadpoles.

So in toads the appearance of the lungs coincides with the loss of the external tail, whereas in salamander larvae there is no such coincidence because lungs are already present in the larva, and the tail is not lost; while in most tadpoles there is no such coincidence because the lungs develop before the tail is lost.

The paper below, Cohen & Alford (1993), gives data on the body sizes of morphlings for Rhinella marina.

I infer that a morphling can be defined in this species as having snout-vent length less than 3 cm.

The smallest morphlings seem to have snout-vent length of 9 mm, which is bigger than I thought, at least in the population these authors studied. I can’t understand how a morphling of 0.9 cm could possibly weigh as little as 0.025 g (which if memory serves is the minimum body mass given a paper by Shine). A morphling of length 0.9 cm is certainly at least blowfly size, not housefly size and certainly not fruitfly size. But I would still classify these as morphlings, because even at ca 1 cm they are still tiny relative to fully mature body sizes. So tiny that an additional, even tinier, larval stage seems ‘over the top’.

The significance of the morphling stage in toads is that:

this stage combines larval body size with adult form;

toads have essentially two consecutive ‘baby’ stages in their life history, viz tadpole and morphling;

morphlings are subject to cannibalism by juveniles regardless of whether they are also cannibalised by adults;

morphlings are part of a life history strategy of extreme fecundity (enormous clutches of eggs, up to 30,000 by a single mother), in which parental care is replaced by parental ‘hyperinvestment’.

The morphlings of Anaxyrus terrestris (, which I take to have snout-vent length of ca 8 mm, can be as small as 0.055g according to the figures in

For comparison, a house fly (length 6mm) has body mass of 0.012g. This means that even the smallest morphlings of Anaxyrus terrestris are about five-fold heavier than the average house fly.

Fully mature Anaxyrus terrestris reaches snout-vent 8 cm or up to 9.2 cm, which is large for a frog.

So the morphlings are small but certainly much larger than fruit fly size.

The hylid Litoria caerulea ( is a large frog. Its tadpole reaches about 5 cm long including the tail. The freshly metamorphosed (tailless) frog has a snout-vent length of about 1.6 cm, which means that it is initially about the same size as a man’s thumbnail. That means about the size of those big dung beetles one sees in elephant faeces. It can live >20 years, and over that time it grows to a snout-vent length of 10 cm.

Compare this with bufonids. Although the mature cane toad (Rhinella marina) is bigger than Litoria caerulea, its tadpole is smaller, reaching only 3.1 cm long including the tail. The freshly metamorphosed (tailless) stage is about 0.7 cm long snout-vent, about the size of a blowfly. This then goes on to grow even more than is the case in Litoria caerulea.

So there is a difference between this hylid and this bufonid, in relative size of tadpole and freshly metamorphosed frog. The difference in body mass is about an order of magnitude, in the case of both the fully-grown tadpole and the freshly metamorphosed ‘adult’ (tailless for the first time).

There is certainly a difference in life history strategy here. It remains debatable whether this difference justifies the introduction of a new term, viz ‘morphling’ (which needs objective criteria), for the extremely small freshly metamorphosed stage of the bufonid, which is more fecund than the hylid.

The value of making this distinction would be more apparent in a comparison with Pseudis (, which has a much larger tadpole again and does not seem to grow much after metamorphosis.

Incidentally, Hyperolius ( has a tadpole that is larger, relative to the mature size of the frog, than is the case for Litoria caerulea. This is partly because the fully mature Hyperolius is so small. No matter how we define ‘morphling’, Hyperolius would certainly not qualify as possessing such a stage in its life history. The whole concept of a ‘morphling’ probably only matters in large frogs, i.e. frog species in which the fully mature stage has a snout-vent length of say >5cm.

Julkaistu marraskuu 24, 2023 06:49 IP. käyttäjältä milewski milewski | 0 kommenttia | Jätä kommentti

The morphlings versus the axolotls (how frogs have warped tadpoles into new shapes and sizes), part 2

...continued from


The best examples of morphlings are to be found in true toads (Bufonidae), and particularly the largest species of toads. While some of the African and Asian toads are fairly large as frogs go, the true giants of the bufonid family occur in the Neotropics. Below I show the distribution ranges of two of the largest spp., namely Rhinella marina and R. diptycha. There is some overlap between these two species in the southeastern Amazon basin, but essentially the former is found to the north and the latter to the south. Rhinella marina extends from southernmost Texas all the way to the Amazon. Rhinella diptycha takes over in the caatinga, cerrado, chaco, Atlantic forest, and Pantanal, reaching northern Argentina although it does not extend as far south as the Pampas.

What this means is that, collectively, these two spp. of large toads cover most of South and central America. Even if morphlings were restricted to just these two spp. and no other frogs, their existence would be noteworthy, not so?

Rhinella marina:

Rhinella diptycha:

See 'Cannibalism is Common' in

This was written by Rick Shine or his colleagues, and explains how cannibalistic the large toad Rhinella marina (introduced into Australia and now a major pest) can be. As he points out, it’s not the fully mature individuals that are most cannibalistic, it’s the young adults. These young adults semi-specialise on eating the morphlings of their own species (which Rick Shine of course does not call morphlings, calling them ‘metamorphs’ instead. But the point is that the life history strategy of this large species of true toad, which is presumably typical of Bufonidae generally, involves a level of cannibalism that is systematic rather than being an occasional aberration. Each individual of this species has to survive a veritable gauntlet of cannibalism during the course of its life, in the morphling stage which is like a second infancy after metamorphosis.

(See my other Post about cannibalism in amphibians,


I have been unsure whether the incidence of morphlings is essentially a scaling phenomenon within Bufonidae, or a phenomenon that will remain after corrections for fully mature body size. I’m leaning towards the latter based on a small species of North American toad, namely Anaxyrus debilis.

Anaxyus debilis ( is so small that I would not expect it to have morphlings. However, its metamorphs are larger than I expected, and far larger than those of enormous toads such as Rhinella marina. This makes it clear that A. debilis falls into a different pattern of development, as opposed to just being a 'scaled-down cane toad' as it were, in which the morphlings cease to be remarkably small relative to the adults.

Breeding females of A. debilis have snout-vent length 4.6-5.4 cm, while metamorphs have snout-vent lengths 1.9-2 cm. Please bear in mind that the morphlings of R. marina have snout-vent ca 1 cm. Having metamorphs even smaller than in R. marina is what one would expect from the small species A. debilis if the two toads shared a pattern in common. Instead, the truth is that in A. debilis, compared with R. marina, the adults are smaller and the metamorphs are larger. So the pattern is broken. This suggests that morphlings occur in some, but certainly not all, bufonids. It’s still possible that morphlings occur in all large bufonids, but if so it won’t be just because they grow large.

Adding to the pile of sometimes inconsistent information on the actual sizes of adults and morphlings in true toads (Bufonidae):

I have before me a source that states that in Rhinella marina, the mature toads are male 14 cm and body mass 1 kg, and female up to about 23 cm and up to 1.5 kg. The morphlings are as follows: “In spite of the enormous size of its parents, a newly-formed cane toad is no more than 6-7 mm long.” This refers no doubt to snout-vent length.

Adults of Phrynobatrachus (, with snout-vent length about 2 cm, have body mass ca 0.5 g. I deduce that the body mass of the morphlings of R. marina is usually 0.1 g or less.

Putting the idea behind the invention of the word ‘morphlings’ as simply as possible:

Bufo bufo, the typical true toad, has a mature female body mass ca 100 g. The following value needs checking, but, assuming that the freshly metamorphosed toad has body mass ca 0.1 g (= ten to a paper clip!), these ‘babies’ are only 0.1% of maternal body mass. Yet these metamorphs are widely and unquestioningly called ‘adults’.

The central problem: how can a toad possibly be called ‘adult’ at only 0.1% of mature body mass? Fact is, true toads have BOTH LARVAE AND INFANTS, and ‘morphling’ is the name I suggest for these infants.

A problem with 'toadlet' is that morphlings are not peculiar to toads, and toads are not clearly defined anyway.

The morphlings are, remarkably, proportionately similar to the fully mature stage, i.e. morphlings are as TINY relative to the fully mature stage as infants would be, but are shaped like mature animals, not like infants.

Putting this another way: in true toads (particularly the largest spp.), the life history is divided into two completely different processes. During the larval stage, there is little change in body size but immense change in body form. After metamorphosis, the situation is quite different: there is immense change in body size but minimal change in body form. Of course this is the basic pattern in amphibians in general, but there is extreme polarisation in bufonids.

The trouble with the word ‘infant’ in this context is that it is too vague. Infant can mean any kind of baby. Instead of increasing understanding by boosting precision, it detracts from understanding by boosting vagueness. Putting this another way, imagine a scientific tradition in which frog tadpoles (which are particularly different from adults, even relative to salamander larvae) had no particular name but were just called ‘larvae’ or, worse still, ‘juveniles’. There’s absolutely nothing incorrect about calling frog tadpoles juveniles, because that is indeed what they are. The trouble is that, while correct, this is too vague.

I only discovered at age 63, after a lifetime of particular interest in and study of frogs, that true toads have exceptionally tiny ‘adults’, because this fact, although known for many centuries, has been hidden by the lack of an apt term.

Another problem with calling these juveniles of true toads ‘infants’ is that this would introduce unnecessary confusion between the ‘adult’ infants and the larval infants. If the morphling is really an infant, then why is the tadpole not also an infant? For example, a kangaroo neonate is just as much an infant as a zebra neonate, obscuring the enormous difference in degrees of development between extremely altricial and extremely precocial neonates among mammals. If one said ‘frog infant’ to most people, I suspect that they would imagine tadpoles. For that matter, why don’t we call foetuses in mammals ‘infants’? In Science, the more precise and specific the word used to describe something, the better.

It seems basic to the definition of morphlings that they would belong mainly, or only, to large species of frogs. This is because what ‘morphling’ describes is a ‘second babyhood’ after metamorphosis, which makes most sense where the eventual fully mature body size is far greater than that at metamorphosis. Of course, fully mature body size is not the only operative variable; also important is the maximum size of the tadpoles. For example, the huge toad Rhinella marina has both large mature body size and extremely small tadpoles at full development of its larval stage.

Based on this thinking, it seems sure that another example of a frog lineage with morphlings is the Conrauidae of Africa. This family contains the largest of all frogs, Conraua goliath (, which can reach 3.6 kg. A frog that large seems likely to qualify for morphlings just on mature body size alone, but as it happens C. goliath also qualifies in terms of its larva: the tadpoles are of unremarkable size compared with other frogs, reaching only 5 cm long before metamorphosing. Those would be large tadpoles for a bufonid, but they are more or less the same size as those of large ranids.

For comparison, the largest frog in North America apart from Rhinella marina is Lithobates catesbeianus (Ranidae), which reaches a maximum body mass of 0.8 kg and has tadpoles 5-7.5 cm long and up to 18 cm long. The African and North American giant frogs are directly comparable because both are among the more aquatic of frogs worldwide.

The West African giant has tadpoles less than a third the length of the North American giant despite having fully mature mass four-fold greater. Morphlings for sure?

This is rather nice, because what it would mean is that both the largest aquatic frog on Earth (C. goliath) and the largest terrestrial frog (R. marina) on Earth have morphlings.


To North Americans, leopard frogs (Ranidae: Lithobates pipiens and related spp.) are bog-standard frogs, similar to the closest thing to a bog-standard frog in the southwestern Cape of South Africa, namely Amietia fuscigula (Pyxicephalidae). The mature frogs are >10 cm snout-vent length, and the freshly metamorphosed juveniles have a snout-vent length of about 2.5 cm, which is a quarter of the mature dimension. The juveniles grow for a further three years before reaching sexual maturity, and then after that keep growing to some extent to full maturity.

These relative sizes are illustrated below. It may help to know the dimensions of my hand: 10 cm wide at the palm, with the last section (phalanx) of middle finger being about 2.5 cm long.

As you can see, the freshly metamorphosed juvenile frogs are not particularly small relative to the human hand. They are about 2.5-fold longer than the morphlings of toads of comparable mature body size, which means that they presumably weigh an order of magnitude more than morphling toads, likewise freshly metamorphosed from the tadpole stage.

The following photo shows the mature size of Lithobates pipiens or a closely related species. If the palm is 10 cm wide, you can see that this frog exceeds 10 cm in snout-vent length.

The following is another photo of the same type of frog, again showing similar mature dimensions.

I’m not sure that the following juvenile is freshly metamorphosed, but it must be close. As you can see, its snout-vent length is about one inch. It’s certainly a ‘baby’, but not nearly as diminutive as morphling toads (Bufonidae). These relative sizes are quite ordinary for juvenile vs mature vertebrates and there’s no need for a special term for these juveniles. My guess is that, although the fully mature stage is comparable in body mass between leopard frogs and toads, the freshly metamorphosed stage is an order of magnitude different in body mass. That’s why I feel that the word ‘morphling’ is useful for the small juveniles. The morphling toad would weigh about as much as the visible section of upper hindleg of the frog in the photo below. following photo shows a handful of the freshly metamorphosed juveniles. Again, as you can see the body size is about one inch long snout-vent, with a body volume similar to that of the last phalanx of the middle finger of a man. Considering that a small standard paper clip weighs about 1 g, it seems safe to assume that the distal phalanx of the middle finger weighs more than a gram, and that in turn the freshly metamorphosed frog also weighs somewhat more than 1 g. Compare this with the minimum size of morphlings in that paper by Shine and co-authors, in which I remarked that it took 20 morphlings to weigh as much as a paper clip.


Perhaps the most famous of all frogs w.r.t. paternal (fatherly) care, namely Darwin’s frog (Rhinodermatidae: Rhinoderma darwinii, may have been hiding in plain sight as an example of what we call the ‘morphling’ phenomenon.

Nobody with any broader knowledge of frogs can have failed to hear of this species of frog, because the male does something so bizarre, with no parallel in any other animal: it ‘gestates’ the tadpoles in its vocal sac.

By the way, the description ‘vocal sacs’ is rather misleading in the same sense as ‘cheek-pouch’ is misleading for the extensive compartments into which certain hamsters stuff food while foraging. The sacs in question, in R. darwinii, extend from the throat all the way on the ventral surface of the male frog, to the groin and on the flanks almost to the back. Entrance to this modified and extended vocal sac, which creates a space between the skin and the muscles of the body, is gained through a pair of slits inside the mouth. What we’re talking about is a huge and newly-invented cavity, effectively sealed off, into which offspring can be inserted for the purposes of parental care. And from which there is a process of ‘giving birth’ because of the sphincters involved.

The male (snout-vent length 2.2-2.8 cm, slightly less than the female which reaches 3.1 cm) guards the large (diam. 4 mm) eggs until they are nearly hatched (which takes 3-4 weeks), and a noteworthy possibility is that the eggs he chooses are not necessarily the ones he’s fathered because the females lay up to 40 eggs, far more than the male can actually gestate. Just before they hatch, the male takes up to 19 eggs into his mouth and gets them to pass through the paired slits into the ‘vocal sacs’. The eggs hatch about three days later in this body cavity of the male (which may or may not be the father) body and, provided with enough yolk by the mother at the time of hatching, they continue to develop as larvae in this cavity, for 50-70 days. Goicoechea et al. (1986) have shown that the tadpoles nourish themselves partly on secretions inside the male’s sac, which would be an even more remarkable case of male gestation. The male ‘gives birth’ to the offspring when they have partly metamorphosed, with just a stump of the tail remaining and a length (presumably snout to ‘tail’ tip) of about 1cm (which is about the size of a morphling toad).

Please see this video clip of the male ‘giving birth’'s_Frog#p0074thp . You can see from this footage that the ‘neonates’ are small relative to the size of the male, which makes mechanical sense because he has to fit up to 19 into a cavity under his skin. If the adult male is 2.5 cm long and his newborns about 1 cm long, this may not seem like a big difference in length. However, because of overall scaling principles one would not expect the newly metamorphosed frogs to be as small, relative to mature size, as we find in large toads. Considering how tiny the adults are in R. darwinii, I’d suggest that the newborns are small enough to be called ‘morphlings’, which makes sense because a lot of them have to be accommodated in the ‘vocal sac’.

A different way of putting this: morphlings may be consistently about 1 cm long in all species, regardless of the great variation in adult body sizes, because of an allometric exponent. What makes them morphlings is that the babies are small relative to those of other frogs of similar adult sizes.

What constitutes a morphling inevitably depends on the body size of the frog species in question. But the bottom line is that any one inch-long adult male that accommodates more than a dozen newly metamorphosed offspring in a single cavity of his body is almost self-evidently accommodating morphlings, i.e. unusually small metamorphs.

If so, I suspect that many or most frog lineages with external development (eggs laid out of the water, and development of the larvae within the egg capsules based on yolk) will turn out to have morphlings as well. This would include, for example, Arthroleptis ( in Africa and Eleutherodactylus ( in the Neotropics. This needs confirmation, though.

Rhinoderma darwinii newly born with adult male. This ‘baby’ may not look particularly tiny next to an adult male but please bear in mind that even the adult is only one inch long:

Newborn Rhinoderma darwinii; this individual looks less than 1 cm long to me:

Here are two more examples relevant to morphlings, heterochrony, and the flexibility of development in frogs.

We’ve seen that true toads feature morphlings, which are extremely small ‘adults’. The superficially toad-like Pelobatidae, which occur in Europe and spend much of their lives underground but breed in seasonal pools, turn out to be different, and more like paradoxical frogs in their life history.

Paradoxical frogs (Pseudis) have tadpoles that grow up to 25 cm long (taking four months to grow this large), then metamorphose into adults of only a bit more than 7 cm snout-vent length. Well, in the case of pelobatids such as Pelobates fuscus, the tadpoles can grow to 8-10 cm long or even up to 15-20 cm long in some cases (compared with only about 3 cm long for the tadpoles of even the largest true toads such as Rhinella marina). After metamorphosis the snout-vent length is a mere 2-4 cm, which means shrinkage even if one allows for the fact that the external tail has been lost.

I infer that this aspect of the development of pelobatids differs from their Nearctic counterparts the Scaphiopodidae (, which is perhaps one of the reasons why the spadefoot toads of the Northern Hemisphere, previously all lumped into one family, have now been split into a North American family and a different Eurasian family.

Secondly, in the Hyperoliidae, an African family that includes apparently annual reed-frogs in the genus Hyperolius:
the South African Kassina maculata grows to 6 cm snout-vent length as an adult, but its tadpoles reach up to 13 cm before metamorphosing (the larval phase takes up to 10 months). Here again, there must be shrinkage even allowing for the loss of the external tail.

So European Pelobates and African Kassina seem to be further examples of the phenomenon episomised by South American pseudids.

Again, note the difference:
Sclerophrys pantherina stays small as a tadpole, and fully metamorphoses into a tiny version of the adult, but elsewhere in South Africa (as far south as Zululand) we have the hyperoliid Kassina which does the opposite, growing into a tadpole so large that, even in full maturity, the metamorphosed frog never regains such length in its head and body.

These are extremely different patterns but previously hidden by a lack of suitable terms. I dare say there are naturalists in South Africa who know much about frogs but don’t appreciate this axis of difference, because the literature has not brought it out for what it is.

to be continued in

Julkaistu marraskuu 24, 2023 12:00 AP. käyttäjältä milewski milewski | 0 kommenttia | Jätä kommentti

marraskuu 23, 2023

Bold black-and-white in females of the sable antelope (Hippotragus niger): anti-predator warning or maternal emulation of masculinity?

For naturalists, a central puzzle of the sable antelope (Hippotragus niger) is why its females combine

  • thoroughly conspicuous colouration (on face as well as rest of figure) with
  • lethal-looking horns (sharp-pointed, and straight enough to be deployed forwards, but curved enough to be deployed against a predator on its back).

The sable antelope is one of the few spp. of ruminants - a clade that comprises hundreds of spp. on various continents - that shows this combination.

(Two caveats: this applies only to the nominate subspecies of the sable antelope, and to fully mature females. In this Post I refer particularly to the subspecies Hippotragus niger niger, and to individual females older than eight years ( However, for conciseness I will just call these 'sable antelope' and 'females'.)

At first glance, the pattern in question suggests aposematism (, which by definition is warning colouration vs predators.

However, aposematic colouration seems far-fetched in ungulates, which rely on vigilance and fleeing as their main anti-predatory strategy.

Furthermore, this explanation would fail scrutiny in the following ways:

  • there is limited evidence that the sable antelope is apt to defend itself from predators by means of its horns, thus undermining the explanatory power of aposematism;
  • aposematism typically applies to non-apparent anti-predator defences (e.g. the glands of skunks), whereas the horns of antelopes are fully apparent;
  • the colouration and horns of females emulate those of males - in which the configuration of horns and colouration are more parsimoniously explained intraspecifically, w.r.t. masculine rivalry; and
  • the sable antelope does not show particularly strong maternal protection of infants and small juveniles, which tend to lag behind their mothers at a most vulnerable time of their lives.

A subsidiary puzzle, which overlaps in the conceptual framework with the main puzzle stated above, is as follows.

There are many bovids ( in which females resemble males, in possessing horns, in being maned and/or bearded, and in having similar colouration between the sexes.

However, in most of these, males are not immediately apparent as such, i.e. there is minimal sexual dimorphism in body size and horn size and form.

In the sable antelope, mature males differ enough from females to be easily recognisable. This is because mature males have

The implication is that the appearance and armaments of females may be emulations of masculinity. This seems as plausible as any explanation invoking anti-predator adaptations.

According to Richard Estes (, the emulation of male appearance by female bovids may be explained by the fact that there is sexual non-segregation, throughout the year, in the spp. concerned. Territorial males would tend to ostracise male offspring at the adolescent stage. However, it is in the mothers' interests to keep their adolescent sons in the protection of the group for as long as possible.

Hence - so goes Estes' hypothesis - females have evolved to match mature males in armaments (horns) and masculine appearance, so that they can protect the adolescents from ostracism for as long as possible.

This explanation seems satisfactory for most lineages of 'plains game' in which there is so little sexual dimorphism that males can be hard to distinguish from females in the field. I refer particularly to wildebeests ( and other alcelaphins, as well as oryxes (

However, this does not fully explain the odd combination of features in the sable antelope. What remains to be explained are that

  • sexual dimorphism remains great enough that, to the human eye, mature males are easily distinguished (by body size and horn length) from mature females,
  • masculine colouration is boldly black-and-white,
  • the colouration of mature females matches the masculine boldness,
  • the horns of females are more credibly intimidating than those of alcelaphins or even oryxes, and
  • there is a particular pattern of what looks like 'warning colouration' on the face.

The anomalies shown by the sable antelope may possibly be explained by its particular habitat and foraging niches, which put a 'arti ular premium in maternal defence of adolescent sons.

The sable antelope, unlike most alcelaphins, inhabits relatively nutrient-poor savannas, in which it depends on small patches of relatively nutrient-rich soil and grasses grown to a certain height after fire. I refer mainly to narrow drainage lines called 'dambos' (, which tend to have clay-rich soil and to be free of trees, and on which the grasses tend to be fairly palatable but only suitable for the sable antelope when they reach about 0.5-1 m high, following combustion in the previous dry season.

What this means is that in the sable antelope, unlike most 'plains game', there may be intense competition among the sex/age classes for crucial food, localised in a generally unpalatable type of vegetation. The best grasses would tend to be taken by the territorial male, and adolescent males in particular would tend to marginalised by the masculine aggression of the territorial male.

Estes and Estes (1969, The Shimba Hills sable population. First progress report), referring to Hippotragus niger roosevelti, state on page 13:

"Sub-adult males [2-3 years old] are often found in nursery herds...Adult sable bulls thus show more tolerance than many other territorial antelopes; for instance male wildebeest are ejected from the herd as yearlings...This tolerance is promoted by submissive (= female) behaviour on the part of young males...The tolerance of males within the nursery herds until a relatively advanced age may be adapted to the frequently low population density in this species. Bachelor herds into which young males might go when evicted from the nursery herds often do not exist, which makes young males that much harder to drive from the nursery herd."

Estes and Estes, The sable in Rhodesia. Second progress report), referring to Hippotragus niger niger, state on page 12:

"Nursery herds of H. n. niger usually include one adult bull. Although more than one adult male has frequently been recorded by different observers, this is actually an unusual and temporary most cases the supernumerary adult males are simply sub-adults. Males are tolerated in the nursery herds up to around the age of three, by which time H. n. niger bulls are often black except for their hindlegs."

Julkaistu marraskuu 23, 2023 05:56 AP. käyttäjältä milewski milewski | 12 kommenttia | Jätä kommentti