Journal archives for November 2022

November 01, 2022

A puzzling observation of the crested barbet (Trachyphonus vaillantii) raiding a weaver's nests

@spencer_wp @bushboy @tonyrebelo @jeremygilmore @ludwig_muller @richardgill @happyasacupcake @rion_c @johnnybirder @lukedowney

On 1 September 2000, in Ithala Game Reserve (, I made the following field notes after watching an individual of the crested barbet (Trachyphonus vaillantii, at a colony of the southern masked weaver (Ploceus velatus,

The location was a garden next to the house and garage of an official in the reserve.

No individual of the southern masked weaver was present at the start of the sequence of events.

The most remarkable aspect of this encounter was that the barbet announced itself repeatedly by a staccato call I have not heard before, with a kingfisher-like quality to it, the very antithesis of secretive behaviour.

The barbet perched upside down at the entrance to nests, investigating several nests in this way, before entering one nest so that only the tip of the tail was visible.

After more than 10 seconds it emerged.

A male individual (yellow forehead and beak) of the southern masked weaver returned a few seconds later. This did not vocalise, or antagonistically approach the barbet.

And yet, even after the male of the southern masked weaver returned, the barbet had the colony to itself for more than 15 minutes, free of any opposition or mobbing, or even attendance by any group of the weaver.

The barbet went on to investigate several more nests, entering (and presumably eating the eggs in) two more for about 15 seconds each.

The repeated call, made intermittently by the barbet throughout the sequence, was an irritable/irritated type of vocalisation, like an alarm call. However, the barbet was certainly not alarmed; instead it behaved boldly/brashly.

Several other individuals of the southern masked weaver then returned, However, they did not harass the barbet.

A few minutes after the barbet stopped calling, more than 10 individuals of the southern masked weaver (including several males) returned. They investigated the various nests, vocalising excitedly, as if trying to ascertain the extent of any damage.


Why did the southern masked weaver not attempt to defend its nests?

My tentative interpretation is that the barbet, being capable of injuring the weaver, was warning the species it was victimising to stay away, while it was busy with its raiding.

Has any reader observed similar behaviour?

Posted on November 01, 2022 10:41 AM by milewski milewski | 5 comments | Leave a comment

Shaping of shrubs and trees by herbivory in Ithala Game Reserve, Zululand, South Africa

@dhoare @tonyrebelo @jeremygilmore @richardgill @alastairpotts @troos @botaneek @wynand_uys @craigpeter @rob_palmer @ricky_taylor @reubenheydenrych @pieterwinter @adriaan_grobler @andrew_hankey @benjamin_walton @zarek

In August-September 2000, I spent about ten days in Ithala Game Reserve (, with as much time as possible on foot (see

One of my search-images was for visible damage to, and/or shaping of, woody plants by herbivores.

In the case of mistletoes, I have not tried to identify the spp., instead mentioning them as part of their host-spp.


Aloidendron barberae

  • fallen mature specimen (tree), with crown heavily browsed by Diceros bicornis (many branches up to 5 cm diam. chewed off and eaten); note that Dracaena aletriformis, although common at same location, was untouched by D. bicornis or other herbivores


Cussonia spicata

  • dead specimen, formerly 7 m high, with bole broken at a height of 1.5 m by Loxodonta africana; on the felled section, the foliage and some of the bark eaten
  • felled specimen, formerly 6 m high, probably pushed over by L. africana, and now reduced to skeleton
  • specimen with a clear browse-line, the height of which indicates Giraffa giraffa


Osyris lanceolata

  • specimen of shrubby growth-form, with a hedged appearance, with stems of diam. 2.5 cm, at height >1 m, grossly broken, probably by male of Strepsiceros strepsiceros


Ehretia rigida and possibly also Ehretia amoena

  • several specimens shaped by nibbling by G. giraffa
  • a few specimens showing damage by D. bicornis
  • specimen heavily browsed


Ximenia americana and/or caffra

  • shrubby specimen 2.5 m high, heavily browsed
  • specimen of arborescent growth-form, <4 m high, heavily browsed by G. giraffa, to the point of defoliated stems; regenerating fresh shoots that are browsed as soon as they appear


Heteropyxis natalensis

  • shrubby specimen 5 m high, with browse-line corresponding to height of G. giraffa, and signs of heavy browsing of epicormic regrowth after fire, probably by S. strepsiceros


Hippobromus pauciflorus

  • shrubby specimen <2.5 m, heavily browsed


Combretum erythrophyllum

  • specimen showing signs of browsing by G. giraffa


Cola greenwayi

  • shrubby specimen with stems of diam. 1 cm chopped and eaten by D. bicornis


Brachylaena discolor

  • suppressed specimen, heavily browsed


Euphorbia tirucalli

  • mature specimen on edge of riverbank, with bark removed by D. bicornis

Euphorbia ingens

  • several tall specimens, >15 m high, showing obvious damage by Papio ursinus: pale scars from broken-off segments of branches; on the ground and in the crotch of main branches, several discarded sections, still green, 30-60 cm long, from which the green 'wings' (which project about 2.5 cm from the green stems) have been bitten/nibbled, indicating that not just the growing tips but also the older stems (succulent) are eaten


Dovyalis rhamnoides

  • specimen chopped grossly by D. bicornis


Ziziphus mucronata

  • mature specimen with indistinct browse-line, corresponding to height of G. giraffa
  • several specimens in the form of small trees, heavily browsed by G. giraffa, to the point that foliage is regenerating from relatively thick stems


Berchemia zeyheri (

  • specimen closely browsed by G. giraffa and S. strepsiceros, so that crown eliminated and leaves restricted to branches
  • specimen <5 m high, heavily browsed by G. giraffa, to the point of defoliation
  • suppressed specimen <5 m high, heavily browsed
  • sapling specimen with bark stripped by L. africana
  • suppressed specimen 1 m high, hedged by heavy browsing
  • mature specimen at least 12 m high, with a distinct browse-line attributable to G. giraffa


Canthium inerme

  • specimen heavily browsed

Note: in a wider context, the extreme form of spinescence in this species is noteworthy, suggesting adaptation vs stripping by L. africana


Searsia leptodictya

  • specimen fairly heavily browsed, with induced branching configuration right-angled, tending to bar stripping

Searsia pallens

  • in one stand of this species, many broken branches, up to 1 m long, littering the ground, with dead leaves still attached

Searsia pentheri and Searsia rehmanniana (both occur, but are easily confused)

  • specimen on alluvial plain, browsed by D. bicornis (chopped stems 1 cm thick)
  • specimens with chopped stems, of diam. 1 cm, indicating that D. bicornis ate branches up to 1 m long
  • specimen with a lower branch broken by D. bicornis


  • suppressed specimen 1 m high, with small leaves and many spines 1.5 cm long, hedged to a spherical shape
  • several specimens bearing mistletoes; these parasitic plants have been browsed by G. giraffa to the point of hedging, but not killed/eliminated
  • specimen >3 m high, heavily browsed by G. giraffa; basically non-spinescent, so browsing has produced a coral-like effect, rather than hedging

Gymnosporia buxifolia and Gymnosporia senegalensis (see

Gymnosporia nemorosa

  • mistletoe at 1.5 m high, the parasite heavily browsed, probably by S. strepsiceros


Elaeodendron transvaalense

  • specimen 1.5 m high, heavily browsed, with hedged growth-form, bearing mistletoe, also heavily browsed and hedged
  • shrubby specimen (3 stems at ground level) with a browse-line (2.2 m high) corresponding to height of S. strepsiceros


Mystroxylon aethiopicum

  • mistletoe present on tree 5 m high, indicating that the dense populations of herbivores in the reserve have not eliminated these parasites


Diospyros dichrophylla

  • shrubs < 1 m high, not visibly shaped, but said by game-guard, Leonard Gumede, to be a preferred food-plant of D. bicornis

Diospyros lycioides

  • specimen with stem of diam. <1 cm chopped by D. bicornis, at height 1 m
  • scandent, somewhat liane-like specimen in the crown of a specimen of Vachellia nilotica that had been broken down by D. bicornis; in the case of V. nilotica, most of the branches chopped at stem diam. <1 cm, and several branches chopped at stem diam. up to 1.5 cm; however, in the case of D. lycioides, a few branches chopped at stem diam. 1 cm, but most of the plant left intact, showing that D. lycioides was less attractive than V. nilotica to the individual concerned of D. bicornis

Diospyros scabrida

  • several specimens heavily browsed


Euclea natalensis

  • specimen <1.5 m high on alluvial levee, so heavily browsed that <5% of foliage remains
  • specimen heavily browsed by S. strepsiceros, with a branch >1 m long broken by horns
  • several specimens 1 m high, heavily browsed (probably by S. strepsiceros), with only 10% of foliage left
  • specimen 2 m high, heavily browsed, only 5% of foliage present, and this has regenerated since last browsing
  • specimen 2.5 m high, with a 0.7-1 m long branches, of diam. 1-1.5 cm, grossly broken, probably by horns of male S. strepsiceros, with their thinner stems removed, leaving ragged ends. On same specimen, chopped stems, of diam. 0.7 cm, attributable to D. bicornis.
  • many specimens <1.5 m high, suppressed by herbivory, with signs including those of D. bicornis
  • many specimens with branches up to 1 m long, broken and severed by S. strepsiceros
  • specimen, formerly 2 m high, grossly damaged at 1.5 m high, by the horns of male S. strepsiceros; on the broken branches, only leaves and shoots eaten

Euclea racemosa (all plants seem unaffected by herbivory, with no shaping; Giraffa seems to ignore this species despite its heavy browsing of E. natalensis)

Euclea schimperi (apparently ignored by G. giraffa)

  • specimen showing browsing by D. bicornis (chopped stems 1 cm thick)
  • specimen 2.2 m high, heavily browsed by S. strepsiceros


Olea europaea cuspidata

  • suppressed specimen, with coppicing and epicormic growth in which the leaves are diminutive and ovate (heteroblastic), heavily browsed and with dead branches
  • suppressed specimen, 1.2 m high, heavily browsed and hedged
  • a stand consisting of many suppressed specimens, <1.5 m high, with hedged shapes
  • arborescent specimen 5 m high, with unmodified crown, but hedged coppice-growth (small leaves on densely divaricating stems) up to 1.5 m high, at base of bole


Pappea capensis

  • specimen formerly 4 m high, pushed over, broken (snapped bole of diam. >10 cm), and killed by D. bicornis, with many twig-size stems chopped and eaten


Dalbergia armata

  • specimen heavily browsed, hedged
  • ditto


Schotia brachypetala

  • mature specimen at least 12 m high, with browse-line corresponding to height of G. giraffa


Senegalia nigrescens

  • sapling with stem diam. 6 cm, scraped by tragelaphin horns (Leonard Gumede stated that S. strepsiceros, N. angasii, and T. sylvaticus are all known to scrape the bark, presumably to eat cambium)
  • sapling with bark stripped by L. africana
  • many mature specimens (trees) in full bloom but no foliage, with browse-line attributable to G. giraffa, below which no flowers remain


Vachellia karroo
This species occurs in the reserve ( However, I did not find it to be common here, and I did not notice any evidence of herbivory on it.

Vachellia nilotica ssp. kraussiana (see and and

  • partly pushed-over specimen, with stems 1.5 cm thick chopped by D. bicornis, indicating the wholesale eating of spinescent branches up to 60 cm long
  • in one area, many specimens, of former height at least 4 m, pushed over or broken down by D. bicornis; some specimens were still alive, by virtue of a remaining connection in the xylem
  • specimen formerly 3.5 m high, pushed over by D. bicornis, with bole (basal diam. 15 cm) snapped
  • several flat-topped specimens, formerly <5 m high, pushed over by D. bicornis, with chopped branches of diam. up to 2 cm
  • several specimens, formerly <3 m high, pushed over by D. bicornis, with most of the branches chopped off and eaten at stem diam. up to 5 cm

Vachellia robusta
This species seems to be unattractive to herbivores. I saw a mature specimen (tree, similar to but smaller than already in full foliage, apparently untouched by G. giraffa.

Vachellia tortilis

  • specimen formerly 3 m high, pushed over by D. bicornis; stem broken but crown still alive


A noteworthy difference in destructive foraging between Loxodonta africana and Diceros bicornis is that the former eats Cussonia spicata, but the latter does not (Leonard Gumede, pers. comm.).

Papio ursinus foraged destructively on Euphorbia ingens, to the point of facilitating Diceros bicornis by dropping fresh, edible litter consisting of partly-eaten sections of green stems. The discarded sections remain alive for some time, by virtue of the broken cross-sections sealing over.

In 2000, all the individuals I saw of Sclerocarya caffra were free of visible damage. My explanation is that L. africana was still underpopulated in the reserve at the time.

Searsia rehmanniana, which is even more abundant than Euclea natalensis in the reserve, seems to be ignored by S. strepsiceros (and G. giraffa). This is consistent with the fact that S. rehmanniana is as much associated with the Fynbos Biome as with subtropical savanna.

However, Searsia pallens ( contradicts the above pattern. It occurs mainly in the Fynbos Biome. Yet, it was apparently damaged by males of S. strepsiceros in Ithala Game Reserve, and I repeatedly observed G. giraffa foraging on it in August-September 2000.

The growth-form of V. nilotica in Ithala Game Reserve, in its maturity, is a sturdy but low tree, up to 4.5 m high with a flat crown up to 4.5 m wide, and a bole of diameter similar to the human waist.

Vachellia nilotica seemed to be associated mainly with parts of Ithala Game Reserve that had been ploughed for crops before 1973. However, this species was scarce in the lower-lying parts of the reserve.

In this area, the typical, flat-topped crown was lower than the maximum height of G. giraffa. However, I saw no evidence that the flatness of the crown was owing to shaping by herbivores. Instead, it seemed intrinsic to the growth-form of the subspecies indigenous to this area.

Vachellia nilotica seemed to be a staple of D. bicornis. However, I also observed G. giraffa foraging on it repeatedly.

Game-guard Leonard Gumede stated that, in Ithala Game Reserve, V. nilotica attracted foraging by both L. africana and D. bicornis. However, L. africana stripped the bark, whereas D. bicornis pushed over the small trees, then chopping off and eating branches.

As the plant grows, the flat shape of the crown of V. nilotica was attained when the plant was only 2 m high, with a basal diameter of only about 12 cm.

A local feature is that some individuals of Diospyros lycioides adopt a liane-like growth-form, climbing particularly into the crowns of V. nilotica. During my visit, I observed a specimen that had climbed to a height of >6 m, by means of this growth-form.

(This habit of D. lycioides, of climbing into the flat crown of Vachellia, has not been captured in any of the 807 observations currently posted in iNaturalist.)

Dichrostachys cinerea was, in Ithala Game Reserve, eaten by D. bicornis, but not preferred (Leonard Gumede, pers. comm.). At the time of my visit, D. cinerea (which differs phenologically from V. nilotica) had few green leaves.

Berchemia zeyheri is attractive to both L. africana and G. giraffa, but the former strips the bark, whereas the latter eats the foliage.

The fact that Elaeodendron transvaalense had a browse-line at only 2.2 m high indicates that this species is more attractive to S. strepsiceros than to G. giraffa. This seems to contradict the situation in the Maasai Mara National Reserve in Kenya, where Giraffa tippelskirchi produces a browse-line on Elaeodendron buchananii ( and and and

Both Euclea, consisting of relatively nutrient-poor 'evergreens', and Vachellia, consisting of relatively nutrient-rich 'deciduous' plants, vary in palatability according to the species.

For example, Euclea racemosa and Vachellia robusta seem to be ignored by herbivores, whereas Euclea natalensis and Vachellia nilotica are grossly damaged.

Euclea racemosa tends to occur as a small tree, up to 5 m high, rather than a multi-stemmed shrub. It tends to be untouched by herbivores, despite the obvious browsing on E. natalensis nearby.

The browsing looked heavier on Euclea natalensis than on Diospyros lycioides. Many specimens of the former were maintained as shrubs 2 m high, whereas the latter was free to climb up into the flat crown of e.g. V. nilotica, but tended not to be eaten even when V. nilotica was felled by D. bicornis.

During this visit to Ithala Game Reserve, I found that G. giraffa, S. strepsiceros, and D. bicornis all foraged on E. natalensis in ways that broke stems.

Euclea natalensis seems to be a local staple for both G. giraffa and S. strepsiceros, both of which are fully-populated in the reserve. It is not hedged by herbivory, but many individuals seem suppressed. Males of S. strepsiceros forage wastefully on this species, by breaking the branches.

Euclea natalensis is a staple of D. bicornis in Ithala Game Reserve, seemingly preferred over Dichrostachys cinerea. It is also heavily browsed by G. giraffa (including juveniles). On severaI occasions, I watched G. giraffa eating whole sprays of foliage, and even the dead leaves still attached to the stems after fire.

The following is a particularly detailed excerpt from my field notes from this visit to Ithala Game Reserve in late August-early September 2000:

"I watch an adult female individual of G. g. giraffa foraging wholesale on an upright, 5 m-high, rather spindly, tree of Euclea (probably natalensis), at the full height of the giraffe. The plant has fresh shoots (whitish, not reddish), but it is not these that the animal takes, particularly. Instead, it strips wholesale whole sprays of leaves (including new shoots in a minor percentage of mouthfuls), pausing to chew these very substantial mouthfuls before proceeding. It extends its tongue to the maximum (perhaps up to 20 cm from the upper lip) to hook around the bare part of a stem, forcefully drawing the branch to be grasped between the tongue and the upper lip, then it strips the whole bunch of leaves (perhaps about 20 mature leaves at a time) off and chews them, plus the smaller (still green) stems and small, growing leaves. On one occasion, the stem is snapped in the process, so that the animal takes the whole branch system in its mouth, chewing the leaves and then dropping the brown length of bared stem, about 22 cm long. With each occasion, the force of grabbing the branch tugs the whole crown jerkily, and with each stripping the branches snap back - an unusually forceful mode of foraging for giraffes. I watch as the animal concentrates on and mutilates this plant, as opposed to merely taking a few bites. It takes about six such sprays of foliage, after which I disturb it by approaching on foot. On closer examination, I find that the animal has significantly (?30%) defoliated the plant. There are many similar individuals of Euclea available. So, the victimisation seen on this occasion suggests that when the animal finds a 'sweet' individual, it indulges in 'bulk foraging' on it, at this time of year. Right next to the victimised plant is a tree of Berchemia zeyheri, so it is not that there are no alternatives available. Based on a week of opportunistic observation here, I would guess that, at this time of year, Euclea natalensis contributes about 10% of food mass consumed by the local population of G. g. giraffa, although requiring only <3% of foraging time. I.e. G. g. giraffa does not eat E. natalensis preferentially, and indeed it passes by most individuals of this species that it encounters; however, when it does eat it, it does so wholesale, by stripping leaves and whole shoot systems up to 30 cm long. The fact that I saw repeated extension of the tongue at this individual plant suggests that the animal had already stripped off all the easily available branches by the time I arrived."

Notes on diet of hook-lipped rhino (Diceros bicornis):

In Ithala Game Reserve, the genera Searsia, Gymnosporia, Diospyros, and Euclea are all abundant, and each contains several spp. here. In much of the reserve, these four genera collectively dominate the vegetation.

This is not ideal habitat for Diceros bicornis. However, it had (as at 2000) proven to be sufficient for a significant contribution to the conservation of this species.

During my visit, I learned of the following being eaten: Sanseviera hyacinthoides, Aloidendron barberae, Euphorbia tirucalli, Dalbergia armata, Dichrostachys cinerea, Vachellia nilotica, and Euclea natalensis. Diceros bicornis did not seem to eat V. nilotica and D. cinerea out of proportion to their abundance. However, their commonness in the reserve means that these mimosas were staples here.

Both D. bicornis and G. giraffa foraged on V. nilotica. However, only the former foraged on it destructively.

Diceros bicornis is capable of pushing over even mature trees of Euphorbia tirucalli (Leonard Gumede, pers. comm.). In 2000, the only specimens of E. tirucalli left in the reserve were trees about 4 m high, in protected situations, such as the edges of earth banks on the edges of drainage lines. Where the plants were protected by their topographical position, D. bicornis resorted to using its anterior horn to prise off the bark, which was presumably eaten.

Also see

Posted on November 01, 2022 10:52 PM by milewski milewski | 11 comments | Leave a comment

Is pace of life more conservative than body size, among families of plants?

(writing in progress)

I have known for decades that body size in plants is remarkably plastic, within taxa.

There are innumerable genera of plants in which some spp. have small bodies, and others have large bodies. This can easily be seen in information on the maximum heights.

To mention just one example: Euphorbia varies from tiny herbaceous species to tall trees ( Members of this genus vary from a few centimetres high (e.g. to 20 metres (

This plasticity in plant height, within families, is noticeable among genera and also within species.

However, a related idea has been more peripheral in my mind, possibly because it cannot be seen as such. I refer to pace of life, viz. the rate at which organisms use energy for metabolism, growth, and reproduction.

(Pace of life is most biologically meaningful when expressed relative to body mass, according to allometry (

I have the impression that pace of life follows the opposite trend from body size in plants. That is to say, that pace of life may be among the least plastic, and most conservative, aspects of plant biology, tending to be consistent with families, regardless of the plasticity in plant size.

There are various clues to pace of life in plants.

One is specialisation for either poor soils (which suggests slow pace of life) or rich soils (which suggests fast pace of life).

Oligotrophic plants are specialised for soils, such as deep siliceous sands, that are poor in all nutrients. A prime example is Proteaceae (

Eutrophic plants are specialised for soils, such as alluvial loans, that are rich in all nutrients. A prime example is Brassicaceae (including Capparaceae, and

Proteas vary in plant height from a few cm to 25 m ( However, all are adapted to poor soils, or those that, if dystrophic, tend to be poor in catabolic nutrients such as zinc (

Brassicas vary in plant height from a few cm to 12 m ( However, all are adapted to rich soils, or those that, if dystrophic, tend to be rich in catabolic nutrients such as zinc.

(writing in progress)

Posted on November 01, 2022 10:59 PM by milewski milewski | 0 comments | Leave a comment

November 06, 2022

An odd anecdote about giraffes and spinescence: prickles of Senegalia ataxacantha pose deterrent risk

@tessabrunette @tonyrebelo @jeremygilmore @ludwig_muller @alastairpotts @matthewinabinett @wynand_uys @richardgill

At 8 am on 23 August 2000, I wrote the following field-notes, while on a visit to Ithala Game Reserve, in Zululand, South Africa. I have illustrated these notes with photos from iNaturalist.

(Dear reader, please bear in mind that this is the degree of spinescence of which the celastraceous genus Gymnosporia is capable, in southern Africa: and

"I watch three individuals of Giraffa giraffa giraffa at close quarters, attended by Dicrurus adsimilis (,vid:PrjfOxkgstU)."

"A subadult male individual forages remarkably intensively on a 2 m-high shrub of Gymnosporia buxifolia, eating wholesale. This individual plant happens to lack the spines typical of its genus ( and and and, allowing it to be damaged efficiently and rapidly by this folivore, in a way that would certainly have been retarded by the normal spines of this species ( and and and The animal eats for more than five minutes from this individual shrub, alternating with an adjacent individual of Hippobromus pauciflorus ( and, which it strips in even more wholesale fashion."

"The only limitation, in the case of G. buxifolia, is the branching pattern ( However, the animal takes bites that are as large as possible, some of which are branches more than 15 cm long, consisting of green leaves plus the green stems bearing them, and others of which are the leaves and shoots stripped from lengths of branch. This includes the ripening capsules of G. buxifolia (, which are turning dull orange. A few minutes after this initial bout of foraging, the same individual of G. g. giraffa returns to the same individual plant, and goes over the same branch systems again, suggesting a determination to make the most of this fortuitous lack of spines."

"I clearly see the action of the tongue in drawing shoots towards the mouth, the tongue stretching to the maximum, curling around the stem, and pulling it to where it can be pressed against the upper lip, in order to detach a bite of food. Accordingly, the bite-size during these bouts ranges from a few leaves to a spray of foliage the size of my outstretched hand, including the stem where this is still green and soft, or leaving the stripped stem behind where this is already brown and hard.'

"Then, an odd thing happens. While foraging on H. pauciflorus, the animal - presumably accidentally - takes a length of stem of what I assume to be Senegalia ataxacantha (, a deciduous species currently (seasonally) bare, with alternating stems covered in prickles, emergent above the thicket in the form of several wispy branches. The length of the stem taken is probably about 30 cm, with small side-stems, each about six cm long. The animal draws this into its mouth, along with the rest of the food, but then spends about 1.5 minutes struggling to chew and swallow it. The item apparently lodged by velcro-like action in the mouth and throat. The animal shows discomfort and incapacitation by making 'funny faces', shaking the muzzle, contorting the mouth, and even shaking the whole head, for a prolonged period. Even after more than a minute of this behaviour, I can still see the end of the stem at the opening of the mouth. Finally, it manages to swallow the offending section of stem."

"With reference to the main species, G. buxifolia: this individual of G. g. giraffa has probably reduced the foliage of this individual plant by more than half during these consecutive bouts, leaving it rather bare-looking. The animal seems to have an equal appetite for G. buxifolia and H. pauciflorus, the latter evading wholesale stripping by virtue of being obstructed in the thicket. Only 8 m away is a shrubby individual of Gymnosporia ?nemorosa, with small spines and relatively dark green leaves, which has remained untouched by any of the three individuals of G. g. giraffa."


This anecdote suggests that Senegalia ataxacantha, in the form of wispy, shooting stems, has a remarkable defensive capacity vs giraffes, the inside of the mouth of which has complex linings (e.g. papillae inside the cheeks).

The effect seems similar to what I myself have experienced with the awns on the whole (unhulled) seeds of Avena sativa (, which, after lodging in my throat, could not be moved by my tongue to a chewable position.

According to the literature, the main function of prickles on acacias is to retard - not prevent - foraging by means of snagging and abrasion on the lips ( and and

My anecdote suggests that, at least in the case of giraffes with their extremely specialised mouths, the mechanism goes beyond mere retardation - to something like categorical deterrence.

ACKNOWLEDGMENT: Many thanks to Wynand Uys (see comments below) for helping me to identify S. ataxacantha retrospectively.

Also see

Posted on November 06, 2022 12:55 AM by milewski milewski | 7 comments | Leave a comment

November 08, 2022

Conspicuous darkness in the adaptive colouration of large herbivores

Posted on November 08, 2022 01:54 AM by milewski milewski | 3 comments | Leave a comment

An extreme contrast in the proportional size of the jaws in large herbivores of grassland: ostrich vs warthogs

One of the remarkable aspects of the guild of large herbivores in Africa is the extreme variation in the proportional size of jaws, among species specialised for eating herbaceous plants.

The extremes are shown by the ostrich (Struthio camelus, and warthogs (Phacochoerus spp.,

Warthogs are the most specialised of suids, on a diet of grass (,stems%2C%20roots%2C%20and%20seeds. and and and and

For its part, the ostrich is an 'honorary ungulate' in the sense that it, like coexisting gazelles, eats mainly greens ( and and and and,on%20these%20types%20of%20nutrients. and and

The notion that the ostrich is omnivorous is one of those ambivalences that has misled generations of naturalists. While it is true that the ostrich has the capacity to eat animals and various other categories of food, its staple diet, wherever it lives in the wild, is foliage.

Warthogs, too, retain a capacity for eating animal matter that exceeds that of most ruminants. Therefore, it turns out that the ostrich is directly comparable with coexisting warthogs in an ecological sense - the great phylogenetic distance between them notwithstanding.

Posted on November 08, 2022 02:24 AM by milewski milewski | 14 comments | Leave a comment

November 10, 2022

Display of the tail in the greater kudu (Strepsiceros) is puzzlingly subtle and inconsistent

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Any naturalist familiar with the greater kudu (Strepsiceros strepsiceros, knows that this bovid ruminant sometimes displays the white of its tail while fleeing ( and and,vid:sthInuu-2DA).

Skinner and Chimimba (2005, state:
", with the tail curled upward to show a flash of white hair. This visual contact signal assists calves and subordinates in following group leaders during flight, especially at night".

However, it is only when one focuses on this phenomenon that its subtlety and inconsistency become apparent.

First let us examine the tail when it is inert.

The tail of the greater kudu is proportionately smaller than in most other Bovinae ( This is because it

  • is relatively short and narrow, and
  • has a relatively small tassel.

The following clearly shows the length of the tail in an adult but not fully mature male individual (

Please compare this with e.g. Boselaphus tragocamelus: and,

The following shows the breadth of the tail in S. strepsiceros (

Please compare this with Nyala angasii:

The following shows the size of the tail tassel in S. strepsiceros ( and

Please compare this with Taurotragus oryx:

In S. strepsiceros, the ventral/inner pelage of the tail, apart from the tassel, is consistently white.

However, the tassel is not consistently dark ( and In some individuals, the tassel may be paler than the shaft of the tail (

The tail of the greater kudu changes in proportional size with age since birth, as follows:

In some individuals, the tail, when inert, is so nondescript as to be hardly noticeable ( and and and and

The following are additional views of the INERT TAIL.

Adult males:

Adolescent males:

Adult females:



In the greater kudu, caudal flagging during running from potential predators is relatively subtle, because

In this species and tragelaphins generally, there is no dark/pale contrast between the bare anal skin and the white pelage of the tail (

This is because the anal/perineal skin is merely flesh-coloured ( and and and and

By contrast, the anal skin is dark in various other bovids (e.g. and and and and and


In the greater kudu, caudal flagging during running from potential predators is relatively inconsistent, because

In the approximately 50 photos collated below, only a quarter show full caudal flagging during running, with the tail curled into a loop in which the tassel touches the base of the tail ( and

The following show the tail fully ACTIVATED during running.

The following show the tail NOT activated during running.,vid:lK0zUZL8M0k

The following show the tail SEMI-ACTIVATED during running.


The subtlety and inconsistency of the anatomy, colouration, and activation of the tail in S. strepsiceros may help to explain why most of the descriptions, in field guide-books, are inept or misleading.

For example:

Also please see

Posted on November 10, 2022 08:40 AM by milewski milewski | 18 comments | Leave a comment

November 11, 2022

November 12, 2022

The gut of the African bush elephant is a scaled-up version of that of herbivorous rats

Everyone knows that elephants are herbivores, and that the African bush elephant (Loxodonta africana) is the largest land mammal in Earth.

However, what may be more poorly appreciated is that various rat-like spp. of rodents, including some coexisting with elephants, are likewise specialised for eating mainly green matter. This means that L. africana shares the same foraging guild as e.g. Otomyinae (

In this framing, elephants are essentially scaled-up versions of rodents, in which the odd features of the megaherbivores can be viewed as allometric compensations for the effects of gravity on body size.

The following surprising finding is based on my own analyses.

Allometry hardly affects the gut of Loxodonta africana, relative to rodents (whether herbivorous or omnivorous).

In both cases, the gastrointestinal tract is about 5-fold the length of the head and body, from tip of nose to base of tail.

The main chambers, viz. stomach and caecum, together constitute about 6% of body mass, in both cases. In both cases, the stomach is slightly less capacious than the caecum, which is the widest part of the hindgut.

Although the colon also contributes to fermentation of the food, it is no wider in L. africana than in the rodents, relative to body length as defined.

The small intestine is proportionately slightly shorter in L. africana than in the rodents, compensating by a slightly greater proportional width.


Perrin and Curtis (1980, and

Clemens and Maloiy (1982, and and

The following is my comparison of gut proportions of the African bush elephant and the mean for 19 spp. of rodents sympatric with it. Length of head and body excludes the tail, but includes the proboscis of L. africana; it was measured along the curvature of the back.

Length of gut relative to head and body: L. africana 5.0, rodents 4.74
Mass of stomach relative to body mass (%): L. africana 2.2-2.9, rodents 2.74
Mass of caecum relative to body mass (%): L. africana 2.7-3.2, rodents 3.3
Length of small intestine relative to hindgut: L. africana 1.4, rodents 1.76
Width of small intestine relative to length of head and body: L. africana 0.019, rodents 0.01
Width of colon relative to length of head and body: L. africana 0.078, rodents 0.095
Width of caecum relative to colon: L. africana 1.8, rodents 1.8.


I conclude that the African bush elephant and omnivorous rodents with which it coexists agree in:

  • the length of the gastrointestinal tract as a percentage of full body length: about 500% in each case,
  • the full mass of the caecum as a percentage of body mass: about 3% in each case,
  • the width of the caecum as a percentage of the width of the colon: about 170% in each case,
  • the length of the small intestine as a percentage of the length of the hindgut: approximately similar, viz. 140-190%,
  • the width of the small intestine as a percentage of the full length of head and body: approximately similar, viz. 1-2%, and
  • the width oftbe colin as a percentage of the full length of head and body: approximately similar, viz. 5-10%.

This suggests that L. africana is, in these aspects of its anatomy, just a scaled-up version of the rodents, as opposed to being subject to the allometric principles that have shaped the bodies as a whole. This is remarkable in view of the 40 thousand-fold difference in body masses.

However, this does not apply to the stomach, which is proportionately larger in L. africana than in the rodents.

Posted on November 12, 2022 09:35 AM by milewski milewski | 1 comment | Leave a comment

Body masses of ungulates in Hluhluwe Game Reserve, Zululand, South Africa

Body mass is one of the most important aspects of any animal.

In this Post, I reiterate the data presented in two relatively obscure publications, and I illustrate the forms. The data are averages, usually with fairly large sample sizes.

The location is Hluhluwe Game Reserve, Zululand.

Hitchins, P M (1968) Liveweights of some mammals from Hluhluwe Game Reserve, Zululand. The Lammergeyer 9: 42.

Hitchins, P M (1966) Body weights and dressed carcass yields of impala and wildebeest in Hluhluwe Game Reserve. Lammergeyer 6: 20-23.

Diceros bicornis minor male 856 kg, female 888 kg
male and

Equus quagga burchellii male 276 kg, female 281 kg
male and
female and

Phacochoerus africanus sundevallii male 77 kg, female 52 kg
male and and and and
female and and and and

Kobus ellipsiprymnus ellipsiprymnus male - , female 189 kg
male and female
female and

Aepyceros melampus melampus male 60.5 kg in one study, 61.5 kg in the other, female 45.5 kg
male and and
female and

Connochaetes taurinus taurinus male 237 kg in one study, 239 kg in the other, female 190.5 kg in one study, 190 kg in the other
male and and
female and infant

Tragelaphus sylvaticus sylvaticus male 45.5 kg (n=1), female 33 kg (n=2)
male and and
female and and and

Nyala angasii male 105 kg, female 63 kg
male and female

Syncerus caffer caffer male 667 kg, female -
male and and
female and infant

Posted on November 12, 2022 09:45 PM by milewski milewski | 2 comments | Leave a comment