Archivos de diario de junio 2023

01 de junio de 2023

Anecdotes on the nature of ungulates, from a farm in Namibia

@tonyrebelo @jeremygilmore @botswanabugs @paradoxornithidae @matthewinabinett @martinmandak

In 2001, I was told the following by Elisabeth Straube, who had lived on a farm in the Khomas Hochland of Namibia, 135 km southwest of Windhoek (


Over the years, Elisabeth had hand-reared various species of wild and domestic animals.

A neighbouring farm had a large population of Equus hartmannae ( Intruders illegally killed a mother, orphaning its female infant.

When Elisabeth took this infant into her care, it was already in a thin and weak state. The milk of domestic Bos proved unsuitable, resulting in diarhhoea.

Despite time being against the survival of the infant, Elisabeth kept experimenting to find a solution. Based on advice from an elderly woman in the area, she followed local lore in giving the infant 4-5 tablespoons of dry, black tea-leaves. This did indeed stop the diarrhoea, buying some time.

Other farmers tipped off Elisabeth about the sweetness of equine milk compared to ruminant milk, so she resorted to klim milk (, and added fructose (fruit sugar). This she dispensed to the infant up to 14 times per day, in a wine bottle, solving the problem of surrogate lactation. Later, this infant would lick sugar from the sugar-pot on the tea table.

As the infant grew, it soon became jealous. It bit car tyres, and tried to bite humans. It would enter the house and jump between the chairs occupied by Elisabeth and others, as if to separate them. When still an infant (with long pelage on the belly), it tried to bite Elisabeth's husband.

This led to the infant/juvenile being banished to a property near Okahandja (, at the age of about six months.

Several months later, Elisabeth visited this individual, which was locked in a kraal. The zebra recognised Elisabeth's voice before seeing her, and cried out immediately. It then accepted Elisabeth in reunion, despite the elapsed interval. Elisabeth was told by experienced locals that E. hartmannae will remain emotionally attached to a foster-mother for the rest of its life - even if this was a man, not a woman.

I infer that this reflects both the strength of maternal imprintation in Equus and the particular social structure of E. hartmannae.


Antidorcas marsupialis has a reputation - somewhat paradoxical in view of its common name - of being unwilling to jump over fences, preferring to crawl under them.

However, Elisabeth observed the carcase of an individual of A.marsupialis that had tried to jump a fence. It had failed to clear the top wires, so that its hind hooves got caught. The animal died - in the way more familiar for Strepsiceros strepsiceros - hanging upside down with the tips of its fore hooves just above the ground (for a photo of a similar casualty, please scroll in


Elisabeth hand-reared an individual of Madoqua damarensis. This animal covered its faeces, as does the domestic cat (Felis catus). It dug a hole with its hooves, then squatted over the hole to defaecate, then used its hooves again, to scrape earth over the faeces.

Elisabeth also hand-reared an individual of Raphicerus campestris steinhardti. She found that this species did not behave in a similar way.


Elisabeth told me that, during a lean period, she observed that Strepsiceros strepsiceros zambesiensis on the farm were weak, and seemed incapable of jumping fences in the usual way. Several individuals were found to have failed to clear the top wires, and died hanging on the fence from their hind hooves. Under these conditions, Elisabeth found that the meat of culled individuals was dark red and, somewhat paradoxically, jelly-like yet not softened by cooking.

During the same period, when foliage was scarce, she observed that S. s. zambesiensis resorted to eating the spines and prickles - which are normally avoided by delicate movements of the lips and tongue during foraging - of shrubs such as acacias.

Elisabeth noticed this when she tried to prepare the tongues of the carcases for the table. The tongues - although appearing fairly normal on the surface - proved to be unfit for consumption, because numerous spines were lodged inside them.

These lodged spines and spine-tips included

This observation indicates that

  • when starving, S. s. zambesiensis can endure the pain of a riddling of the tongue with embedded spines, in an attempt to survive on the leafless twigs, and
  • this does not result in so much inflammation that the tongue becomes obviously swollen.


Elisabeth also hand-reared an individual of the domestic pig (Sus scrofa), and found it to be so intelligent and responsive that it made a particularly rewarding pet.

I find this surprising, for the following reasons.

Most mammals subjected to domestication have become decephalised in the process (, but this is particularly so for Sus.

Furthermore, there is little about the niche of the wild ancestor that would suggest an evolutionary pressure for intelligence exceeding that general for artiodactyls. If anything, one would expect minimal intelligence in Sus relative to other artiodactyls, because of the extreme fecundity of this genus.

Homo and Sus are in various ways biologically similar enough (omnivory, relatively pale muscle-tissue, sundry physiological processes) for Sus to be a suitable model in laboratory work in medicine. However, Homo and Sus could hardly differ more in pace of life (particularly in rates of growth and reproduction). This has been the basis for an extremely successful 'mutualism' in domestication, in which the gulf between Homo and Sus has been further widened by selective breeding in which fecundity has increased, and braininess has decreased, in Sus.

Thus, to find that, despite the conceptual framework outlined above, the domestic pig remains more intelligent than most artiodactyls, is deeply puzzling.

Publicado el junio 1, 2023 12:24 TARDE por milewski milewski | 1 comentario | Deja un comentario

02 de junio de 2023

Ecologically relevant aspects of the biogeography of fungus-culturing termites in southern Africa

In iNaturalist, the coverage of termites is poor.

This is unfortunate, because these insects are ecologically important.

In this Post, I compensate somewhat for this deficiency by reviewing the literature on the biogeography of certain termites in southern Africa, in an interpretive way.

The references are

Let us begin with the astonishing fact that termites (presumably Macrotermes) have been recorded burrowing as deep as 84 m. This has important implications ecologically, particularly for the retrieval of leached nutrients and the boosting of productivity in whole ecosystems.

Marais and Irish (1989) state "we have observed active termite tunnels at the following depths in South West African caves: 25 m (Pofaddergat), 27 m (Ghaub Cave), 47 m (Dante's Cave), 84 m (Arnhemgrot)"

The following provides information in the location of these caves:

Ghaub Cave and

Dante Cave

Arnhem Cave: 85 km east-southeast of Windhoek and

I infer that the species penetrating underground to a depth of 84 m is Macrotermes natalensis.

The subfamily Macrotermitinae of the family Termitidae consists of fungus-culturing termites. This means that they function more like large herbivores than like mere invertebrate agents of decomposition.

Macrotermes is an extremely important genus of termites. However, few naturalists have a grasp of it, even at the generic level - partly owing to confusion with Odontotermes. One of the reasons why the biogeography of Macrotermes remains so obscure is that the size and shape of the mounds varies greatly among, and within, species.

For example:
The mounds of Macrotermes natalensis (

Macrotermes natalensis

  • is the only species in its genus to penetrate south of 28 degrees South,
  • reaches part of the Highveld (, as far south as 29 degrees South in Free State province in South Africa, - marginally penetrates the Nama Karoo (, and
  • reaches nearly as far south as 33 degrees South in Eastern Cape province of South Africa.

Tinley (1985) refers to the occurrence of large mounds of Macrotermes natalensis in the Eastern Cape, at the southerly limit of the genus. The large mounds occur in a strip, hugging the coast from Transkei ( to near East London (,_South_Africa). The soils in these landforms are red loams with clay subsoil.

Near East London, the mounds of M. natalensis have diameters of about 10 m and heights up to 2.5 m. They are covered in bush-clumps of Phoenix reclinata ( and Phyllanthus reticulatus (, exempt from wildfire.

Richard Knight told me, in 2001, that the (aggregated?) mounds of M. natalensis in Transkei ( actually reach 200-300 m in diameter and 5 m in height; these are usually on duplex, not seasonally waterlogged soils. He emphasised the prominence of these mounds in the landscape, with soils and vegetation extremely different from the surroundings. Richard Knight claimed that the mounds were more or less covered in forests, in which e.g. Mimusops reached bole diameters exceeding 50 cm.

(I have yet to reconcile any differences in the accounts given by Ken Tinley vs Richard Knight.)

Macrotermes penetrates rainforest in tropical Africa, but not in southern Africa.

Macrotermes subhyalinus ( builds mounds at least 6 m high in Angola and northeastern Africa, but no higher than 4.2 m in Kaokoland (, where it penetrates the pro-Namib.

Macrotermes bellicosus ( in Uganda transports earth into its mounds at rates of 0.4-0.9 cubic metres per hectare per year. This produces mounds averaging 4-8 cubic metres per hectare.

Some spp. of Macrotermes (e.g. vitrialatus and falciger) harvest plant matter, including living plants which they cut down, in the open. In this way they resemble the hodotermitids Hodotermes ( and Microhodotermes ( Adding to this similarity is the fact that M. vitrialatus - like the ecologically powerful Hodotermes mossambicus ( - does not build mounds.

Other spp. of Macrotermes forage on the ground surface (mainly for litter and faeces, including those of Bos and Loxodonta) under the cover of mud-runnels. They construct these temporary shelters ad-hoc, as they go along. Examples are M. natalensis, M. michaelseni, and M. subhyalinus.

Let us focus on Namibia, where the relationship of large-bodied, fungus-culturing termites to aridity and temperature is relatively easy to describe.

The biogeography of Macrotermes and Odontotermes in Namibia, proceeding from north to south, is as follows:

Publicado el junio 2, 2023 07:08 TARDE por milewski milewski | 13 comentarios | Deja un comentario

04 de junio de 2023

Termite mounds in tropical Asia are puzzlingly different from those in Africa

Everyone knows that the only part of the world that bears any faunistic resemblance to Africa is tropical Asia, particularly the Indian subcontinent.

However, what may be poorly appreciated by most naturalists is how this relates to the ecologically important fungus-culturing termites, Macrotermes and Odontotermes.

Both of these genera occur in both Africa and Asia. However, the main differences are that the largest above-ground structures

  • are built by Macrotermes in Africa, vs by Odontotermes in Asia, and
  • are far smaller in Asia than in Africa.

Lee and Wood (1971), on page 172, states:
"Large termite mounds (species not identified) are common on grey soils near Soekamandi ( in Java."

Mounds, large enough to be sites for the cultivation of dryland crops, are scattered through rice paddies on the flat lowlands of Thailand.

In Sri Lanka, mounds of Odontotermes redemanni (,of%20sugarcane%2C%20tea%20and%20coconut.) are large enough for the cultivation of crops.

In central Congo, there are large fossil mounds (now abandoned) of termites, dating from a previous dry period. These nave densities of 4-7/ha, and occupy 30% of the ground surface. The outer layer of these mounds is fairly fertile. However, the central mass consists of subsoil, which has proven to be infertile for cultivated crops when levelled. In this area, horticulture has produced large patches of sterile ground.

Hesse (1955) noted that, in many areas of East Africa, the mounds of termites are used as earth-licks (i.e. for geophagy), by Bos and wild ungulates. (My commentary: in my experience, this includes the relatively small mounds of Odontotermes.)

The chapter 'Effects on vegetation' in Lee and Wood (1971, pp. 162 ff) is a good review of the patterns of vegetation on large mounds. "In Thailand, Pendleton (1941) noted that large termite mounds (Macrotermitinae) were occupied by a dense growth of trees and shrubs which did not grow well, if at all, on the padi or forested land around them".

Publicado el junio 4, 2023 02:06 MAÑANA por milewski milewski | 3 comentarios | Deja un comentario

05 de junio de 2023

In stotting its bleeze, the Patagonian mara (Dolichotis patagonum) may be the most ungulate-like rodent on Earth

@gonsaro @r-a-p @kfinn @jeremygilmore @santiagoramos @enricotosto96 @nicoolejnik @paradoxornithidae @botswanabugs @tonyrebelo

The Patagonian mara (Dolichotis patagonum, is a relatively cursorial caviid rodent (, with a body mass of about 10 kg.

Please see and

This may be the only rodent on Earth that

  • stots ( by means of stiff-legged, bouncing locomotion, and
  • possesses a bleeze (defined as a dark/pale pattern so bold that it makes the whole figure conspicuous, even at distance, and even when stationary).

The combination of stotting and displaying a large-scale conspicuous pattern on the hindquarters is associated with ruminants, from Ourebia ourebi (about 15 kg, to Alcelaphus caama (about 130 kg,

Among animals featuring this combination, the Patagonian mara is possibly

  • the only rodent, and
  • the smallest of all mammals.

(Please also see

The following show that the bleeze of the Patagonian mara

  • is situated on the hindquarters, from the base of the tail to each haunch,
  • has a mainly horizontal orientation,
  • shows dark/pale contrast, independent of sheen/anti-sheen effects, and
  • subsumes but is not contributed to by the tail, which is short and bare.

The following shows that, in some individuals, there is a whitish patch near each knee (at the junction of flank and hindleg). In posteriolateral view, this extends the bleeze in an anterior direction (

The following show that the bleeze of the Patagonian mara is conspicuous even when the standing figure is viewed in full profile ( and

The following suggests that the white band of the bleeze can be flared/erected (

The following shows the appearance of the bleeze when the animal flees ( and

The following shows that the bleeze is concealed by sitting, which is a frequently used posture in the Patagonian mara ( and

The following show the stotting gait of the Patagonian mara:

The Patagonian mara has long, slender legs for a rodent, and might be described as a 'cavy on high heels'. However, it remains digitigrade (, not unguligrade (

The following show the walking gait of the Patagonian mara:

The following show the similarity in walking gait between the mara and a like-size African bambi, Raphicerus campestris (about 10 kg):


Bambis (ruminants with body mass 15 kg or less) occur in South America. However, all of these depend on cover, and have inconspicuous colouration. The niche for a bambi in open vegetation has been usurped by a rodent, on this continent.

With the possible exception of one species/subspecies of Ourebia (which is marginal to the body mass criterion for bambis, anyway), no bambi on Earth possesses a bleeze.

(Please see

The steenbok possesses a conspicuous white patch on the buttocks. However this qualifies as a flag rather than a bleeze, because it is

Furthermore, the steenbok does not stot.

Aspects of the Patagonian mara that are evolutionarily convergent with bovid bambis include

  • extremely large eyes, adapted for good vision by day,
  • hue-differentiation in the ground-colour
  • monogamy, and
  • precociality at birth.

However, there is negligible convergence with bovid bambis in

in view of the limited convergence between the Patagonian mara and ungulates, its possession of a well-developed bleeze is surprising. In displaying this conspicuous pattern, particularly by stotting, it outdoes its bovid counterparts - despite being otherwise only superficially ungulate-like.

Publicado el junio 5, 2023 12:39 MAÑANA por milewski milewski | 39 comentarios | Deja un comentario

Interpretive notes on the termite family Hodotermitidae in Africa, part 1: Hodotermes (Coaton and Sheasby, 1972, 1975)

@tonyrebelo @beetledude @botswanabugs @jtermiteo @r_r_r_ @hamishrobertson

The aim of this Post is to provide an interpretive review of several half-century old, but still best-of-their-kind, papers about the African members of an ecologically extremely important family of insects, viz. Isoptera: Hodotermitidae.


My first reference is Coaton W G H and Sheasby J L (1975,

Hodotermes is restricted to subSaharan Africa, and contains two spp.

Hodotermes occurs in southern and East Africa, as far north as Eritrea. However, H. mossambicus occurs only as far north as Ethiopia. Hodotermes erythreensis replaces H. mossambicus in Eritrea, Somaliland, and possibly Somalia and easternmost Ethiopia (

My commentary:
Biogeographically, H. mossambicus is remarkable in paralleling a pattern in the ungulates, in which

  • many genera and spp. occur in southern and East Africa, but not West Africa,
  • there is a broad disjunction between southern and East Africa, and
  • the Horn of Africa tends to have a distinctive fauna.

Hodotermes mossambicus occurs mainly where mean annual rainfall is <750 mm, except for East Africa, where it may extend to 800 mm. It occurs widely in Namibia (50-600 mm) and Botswana (200->600 mm), including the southwestern Kalahari (Kgalagadi Transfrontier Park,

Hodotermes mossambicus is absent from most of the Namib, but present in the Namib in Kaokoland and at Walvis Bay. In the Kalahari, it is restricted to the finer-grained substrates, and perhaps absent from the coarsest, nutrient-poorest sands. However, it is present (see Coaton 1963, and in sparse populations on dunes/sandflats.

My commentary:

Hodotermes mossambicus is somewhat tolerant of salinity (also see Popov et al.). In Zimbabwe, it is absent from granitic substrates, except where saline.

My commentary:
Hodotermes mossambicus seems to prefer base-saturated substrates.

Each colony has several/many hives (diameter <60 cm), at densities of 85-96 hives per hectare. The hives are 1.8-12.2 m deep. Only a few of the hives in each colony contain reproductives. Storage chambers for food are extraneous to the hives, and are mainly <30 cm deep. The hives within each colony are linked by tunnels, 2.5-7.5 cm in diameter.

My commentary:
The subterranean location of the hives, with no clue at the surface, protects H. mossambicus from predation by large myrmecophages ( This helps to balance the exposure of the workers as they scurry on the surface (including in cold weather) while foraging.

The diet is mainly, but not exclusively, grass.

My commentary:
In contrast to the normal conception of a termite, Hodotermes mossambicus acts as a grazer of mainly dry 'sweet' grass. It drinks at depth, as opposed to the horizontal commuting performed by grazing ungulates.


In Zululand, the mean annual production of grass is at least 3 tonnes (dry matter) per hectare. Hodotermes mossambicus is capable, in its own right, of harvesting most of this production.

My commentary:
This implies suppression of wildfire, and conservation of nutrient elements, e.g. nitrogen, sulphur, and selenium, that are easily volatilised and depleted by combustion.

Coaton and Sheasby (1975) state:
"Coaton (1958) reported that extensive areas in Zululand carried saturated populations of H. mossambicus which were consuming grass at an estimated rate of 1-3 tons per morgen (1.06-3.17 metric tons per hectare) per year." Some populations consumed the entire crop of hay on a given site, where production of hay is about 3 tons per morgen (3.17 metric tons per hectare).

"Veld hay was produced at a rate of just on 3 metric tons/hectare over stretches of Lowveld and Zululand Thornveld in the Game Corridor between the Hluhluwe and the Umfolosi Game Reserves, an area not grazed by livestock in which H. mossambicus is present, although not in pest extreme case is cited of an ungrazed area in Zululand, which for years had been completely denuded by the end of winter, yielding 3 metric tons of baled hay per hectare per annum after saturated harvester termite infestation had been exterminated; at the other end of the scale, a far lighter infestation in an ungrazed test enclosure in the central Orange Free State has been recorded as removing only about 100 kg per hectare per year out of a total hay production of just over one metric ton".

My commentary:
I infer that H. mossambicus is fully a part of the habitat of wild ungulates in Zululand, even though this area is on the moist side, climatically. The map in Coaton and Sheasby (1975) shows the species to be present in Ndumo. uMkhuze, and St Lucia reserves. This termite shares a guild with the fauna of ungulate grazers of Zululand, which are noteworthy in that they extend from tropical to subtropical latitudes.

"On numerous occasions foraging workers of H. mossambicus have been observed to be cutting down lush green grass, the supplies gleaned being taken directly underground or left lying on the surface around the foraging ports, for subsequent collection...Thriving colonies have also been recorded as doing extensive damage to growing small-grain, legume and fodder crops where the diet must have consisted almost exclusively of green plant material."

Coaton and Sheasby (1975) describe a situation in which the entire diet of a colony for years was lawn grass, viz. Cenchrus clandestinus ( in a green state.

"From the observations presented above it is clear that under natural conditions in the field colonies of H. mossambicus can thrive on a practically undiluted diet of green vegetation" (appropriately cured, of course, after cutting).

My commentary:
This is a clear reference to

  • foraging by day in winter, and by night in summer,
  • damage to agricultural crops, and
  • consumption of not only dry but also green grass, the latter being in some cases 100% of the diet, and/or 100% of the green grass present on a given site.

My second main reference is Coaton and Sheasby (1972,

Referring to Namibia, these authors state:
"Including the vast Northern Kalahari region, which is rather lightly infested by harvester termites except on the more consolidated soils of river flood-plains, omurambas, vleis, and dune valleys, it is very conservatively estimated that H. mossambicus consumes approximately 25% of the aggregate hay yield of South West Africa during every year of average rainfall. In years of drought, when grass regeneration is poor, this figure would be doubled or even trebled. Apart from lowering the stock-carrying capacity of the territory by at least one-quarter these termites are facilitating soil erosion and desert encroachment through their removal of the protective grass cover."

The following seems to have no presence on the Web, even as a mere citation:
Grube S (2000) Soil clumps - indicators of foraging activity by Hodotermes mossambicus (Hagen) (Isoptera, Hodotermitidae) in northern Namibia. Cimbebasia 16: 269-270.

This author states that dumping of soil at the surface, by Hodotermes mossambicus, is not correlated with foraging activity. Foraging activity peaked in the rainy season, whereas the dumping of soil peaked in winter.

My commentary:
Are these termites feeding fertiliser to the grass and herbivores? Why is it that no author mentions the faeces of Hodotermitidae, which - in my experience - appear dark and nutrient-rich, like valuable fertilizer?

Lee and Wood (1971,, on page 180, state in a worldwide context: "It is only in South Africa that the depredations of termites in pastures have been considered sufficiently injurious to merit the adoption of extensive control measures."

However, even in central Asia, the hodotermitid Acanthotermes ahngerianus is a pasture pest, where grass grows. Bare areas around the nests may occupy 20% of the surface. (Also see the second comment below.)

My commentary:
I take this as evidence of the role of herbivory - with ungulates and termites working in concert - in producing low, palatable, fire-free vegetation in South Africa. I note that no termite on Earth is known to cut and maintain hedges or lawns. The fact that H. mossambicus eradicates lawns (patchily), rather than promoting or maintaining them, is crucial for understanding how the same species can be despised as a pasture pest by pastoralists, and valued as a natural member of the grazing guild by wildlife managers who understand the longer-term, more holistic relationships among herbivory, fire, and nutrient-cycling.

to be continued in

Publicado el junio 5, 2023 02:28 MAÑANA por milewski milewski | 15 comentarios | Deja un comentario

07 de junio de 2023

The role of fungus-culturing termites in turning Kalahari sand into an ecosystem of megaherbivores in the Okavango

(writing in progress)

See and

My references are McCarthy et al. (1991,

What I have learned from these studies:

The Okavango is not a delta, but an alluvial fan

The channels keep changing, as the accumulation of organic matter blocks them

Peat fires deplete this organkc matter

Most (96%) of the water evaporates, instead of sinking into the earth

Thus there is a pan-like effect, in which a considerable quantity of salt builds up in the Okavango

Islands are formed partly by termite mounds, via a mechanism of precipitation of solutes

Evaporation and precipitation are aided by the transpiration of trees

The centres of islands tend to be so saline that they are bare of vegetation

I infer that:

  • the accumulation of peat presumably acts as a bank for iodine, over the century of accumulation of peat in each channel, and
  • the concentration of calcium carbonate on islands, particularly based on termite mounds, would also act as a bank for iodine, in the form of iodate.

Iodine flows in, in extreme dilution, in the water of the Okavango River. It is somewhat concentrated by evaporation, and then greatly concentrated by evaporation from islands, aided by

  • transpiration from trees,
  • precipitation of calcium carbonate, and
  • binding to peat.

Iodine is thus stored in non-volatile forms, over time.
The peat fires that deplete the organic matter are mild, with combustion so slow that minimal smoke is produced. Thisnpossibly minimkses volatilisation, conserving much of the iodine.

Because the watershed of the Okavango River is flat and sandy, silt is scarce in the Okavango. Thus, remarkably, the main land-building material for the construction of islands is actually precipitated solutes, e.g. calcium.

The groundwater under the islands is actually saline.

I infer that the islands of the Okavango act almost like the pans of the semi-arid Kalahari, farther afield.

In both cases,

  • fairly fresh water surrounds the evaporational surface, which concentrates salt and calcium from the water,
  • ungulates are likely to seek nutrients by geophagy, perhaps at the periphery of the saline centre of the evaporative surface,
  • groundwater under the evaporative surface is likely to be saline, in contrast to the surrounding water at the same horizontal level.

Basically, both pans in the Kalahari and islands in the Okavango can concentrate iodine from the surrounding fresh waters, and store it in calcium-rich material at tne surface, where iodate is likely to be stabilised. In the case of the islands of the Okavango, leaching of IO3 by rainfall is likely to be prevented on termite mounds.

Peat layers aggrade by about 5 cm per year, to a cumulative depth of about 5 m, before the channel blocks and shifts elsewhere. This takes about one century.

"Water in the Okavango swamps is of the carbonate-rich variety typical of continental regiions" (McCarthy and Metcalfe, 1990).

Islands have precipitation of calcium carbonate from evaporation of the waters of the Okavango River. This precipitate is concentrated by termites.

In the capillary fringe area of islands, calcium precipitates out first (edges of islands), whereas sodium reaches the centre of the island in solution, precipitating out there to form a trona crust (

Island centres:
"During the rainy season, surface crusts are dissolved and leached down into the soil...the rainfall rarely contributes to the water table, and the rainfall and its dissolved salts are merely held in the profile...During the dry season, the salts are returned to the surface" (McCarthy and Metcalfe, 1990).

McCarthy and Metcalfe (1990): the observed concentrations of calcium in the Okavango are calculated to have required 22,000 years, to the nearest order of magnitude. Thksnis likely to err on the conservative side, because rates of evaporation are greater now than in the past.

My commentary:

  • I infer that these deposits are about as old as those in heuweltjies in the Western Cape province of South Africa.
  • Peat may possibly act as a trap and bank for selenium, as well as iodine.

Salt tends to accumulate in the centres of the islands, to be eventually leached to the saline groundwater table, or redissolved, leading to the recovery of vegetation on the saline surfaces.

The result:
Although certain zones do become saline, there are many opportunities for geophagy of iodate and calcium, without excess salinity.

McCarthy does point out, in certain of his papers, that the calcium precipitated on islands is brought up (and concentrated?) by termites (mounds?).

Notes from McCarthy, McIver and Verhagen (1991):

I infer that the whole island fringe acts like a termite mound, in the sense that it is

  • elevated,
  • colonised by trees,
  • replete with calcium carbonate,
  • unleached,
  • perpetuated by the precipitation of solutes, by virtue of transpiration, and
  • ?fire-free.

The centres of the islands act like land, in which bare ground develops because of salinity.

The fringe of the island is raised by the precipitation of silica and calcium originating in the waters of the Okavango River. The centre of each island is at a lower altitude than not only the fringe of the island, but also the water level of the surrounding marsh/swamp. This is because, in contrast to the fringe lf the island, the centre is actually deflated. Obviously, the level of the groundwater beneath the centre of the island is likewise lower than the water level of the surrounding marsh/swamp. This is true for all of the islands, regardless if the stage in the flood-cycle. The saline water in the centre of the island may actually sink into the briney watertable there, because saline water is denser (heavier) than fresh water.

(writing in progress)

Publicado el junio 7, 2023 04:30 MAÑANA por milewski milewski | 7 comentarios | Deja un comentario

08 de junio de 2023

Interpretive notes on the termite family Hodotermitidae in Africa, part 2: Microhodotermes (Coaton and Sheasby, 1974)

...continued from

The body mass of Hodotermes mossambicus is recorded as 7.66 mg.

My commentary:
Is this the fully-grown worker? Is this as large as the largest-bodied termite in Australia? (see,antennae%20of%2020%2D26%20segments.)

Hodotermes mossambicus

  • is effectively a grazer (more so than confamilial Anacanthotermes)
  • digs extremely deeply
  • corresponds biogeographically to the distinctive fauna of large mammals in southern and East Africa
  • corresponds biogeographically to the largest termitophage on Earth
  • has no counterpart in the Sahel or North Africa
  • is excluded by leaching climates and winter rainfall
  • has no ecological counterpart on any other continent (although Anacanthotermes in India deserves further investigation)
  • builds no mounds, yet greatly affects soils and fire-regimes.

The size of the colonies of Hodotermes mossambicus is approximately constant. Hence, during dry periods, it clears all the grass from an expanding area. I note that this happens instead of the colony allowing its size to be reduced by drought. So, H. mossambicus seems to operate with the same inertia as large herbivores. The result is freedom from combustion and its associated wastage.

Seely M K and Mitchell D (1986) Termite casts in Tsondab sandstone. pp. 109-112 in: Palaeoecology of Africa and the surrounding islands, ed. by E M van Zinderen Bakker, J A Coetzee and L Scott, vol. 17. A A Balkema, Rotterdam.

Hodotermes mossambicus occurs even in the 'sand sea' of the Namib. Its surface burrows have diameter about 1.15 cm. One nest serves an area of 1,900 square metres, with 16 soil dumps and 125 foraging entrances/exits, with mean density 0.3 holes per square metre.

Hodotermes mossambicus on the dunes of the Namib becomes active after unusual rainfall, which occurs at a frequency less than once per decade.

Hodotermes mossambicus burrows down to the water table. Whenever the supply of grass suffices, it makes saliva-cemented 'pedotubules'.

My commentary:
It is remarkable that a grazing termite survives even in the Namib desert. The fact that H. mossambicus penetrates the Namib, but remains absent from Transkei-Pondoland-southern Natal, and the vicinity of Barberton (,_South_Africa), indicates that freedom from leaching is biogeographically important to this termite.

Hewitt P H, van der Westhuizen M C, van der Linde T C de K, and Mitchell J (1990) The dry matter, energy and nitrogen budget of the harvester termite Hodotermes mossambicus (Hagen). S Afr J Sci 86: 30-34.

580 individual termites (were these all fully-grown workers?) weighed 4442 mg (fresh mass) or 834 mg (dry mass).

Hodotermes mossambicus eats almost exclusively dry grass, with an efficiency of conversion of 4.8-6.4%.

The rate of consumption of air-dry plant matter is 7-1,500 kg per hectare per year.

Of the energy ingested, 67% goes to maintenance, 6% to growth, and 27% to faeces. Of the nitrogen ingested, 63% goes to growth, and 37% foes to faeces. There is no fixation of nitrogen in the gut.

The energy-conversion of H. mossambicus is inefficient for an insect. Nitrogen, however, is converted to biomass about as efficiently as in ruminants.

My commentary:
This strengthens the analogy with ungulate grazers. Hodotermitids differ from most other termites in producing faeces which are potentially valuable as fertilizer for herbaceous plants.

About 700 kg per hectare of soil is brought to the surface, per year. The soil dumps of H. mossambicus are about 5-fold richer in nitrogen than the surrounding soil.

"Approximately 14 times more dry grass was collected in the winter than green grass in the summer. Populations actually increase in dry times, rather than decreasing as they do in coexisting ungulates.

Most soil-dumping occurs in late summer-autumn. The nitrogen-richness of dumped soil indicates faecal content. The concentration of nitrogen in faeces is about 1.16%. This suggests a role resembling that of earthworms, rather than other termites.

Hodotermes mossambicus does use faeces to construct its hives. However, most of the faeces are dumped back on to the ground surface, serving as fertiliser for grass.

My commentary:
This is a good reference for the fertilisation effect of Hodotermes on the topsoil.

For every 100 kg (dry matter) of grass ingested, about 5 kg of this species of termite is produced.

Reproduction may amount to 3 million individuals per hectare per year.


My third main reference is Coaton W G H and Sheasby J L (1974) National survey of the Isoptera of southern Africa. 6. Microhodotermes Sjoestedt (Hodotermitidae). Cimbebasia Series A, vol. 3, no. 6, pp. 47-59.

My commentary:
Please note that these authors do not mention any relationship between H. viator and heuweltjies (

Like Hodotermes, this genus is approximately restricted to non-leaching climates (mean annual rainfall <750 mm). Whereas Hodotermes is associated with summer rainfall, Microhodotermes is associated with winter rainfall.

My commentary:
The threshold value of 750 mm of rainfall seems to correspond to Paarl Mountain, where I observed M. viator (

The genus Microhodotermes occurs under winter rainfall not only in southern Africa, but also in North Africa, where Hodotermes is absent. The North African spp. are:

  • Microhodotermes maroccanus (Morocco), and
  • Microhodotermes wasmanni (Tunisia, Libya, and Egypt).

My commentary:
Note that this genus, and the whole family, is absent from the Sahel ( This parallels various ungulates and myrmecophages such as Equus, Alcelaphus, Connochaetes, Raphicerus campestris, and Sylvicapra grimmia, which are typical of semi-arid climates in southern Africa, but have no wild counterparts in the Sahel in West and west-central Africa.

Microhodotermes viator

  • was not recorded by these authors from the Agulhas Plain,
  • was recorded from what is now Addo National Park (, marginally penetrating climates in which rainfall in summer exceeds that in winter,
  • has an abrupt eastern border to its distribution indicating mutual exclusiveness with Macrotermes natalensis,
  • occurs under a range in mean annual rainfall from <125 mm to 750 mm, and an altitudinal range from the coast to 1,700 m.

My commentary:
The upper limit of rainfall is similar to that for H. mossambicus. There seems to be exact geographical complementarity between this hodotermitid and the southernmost fungus-culturing termite, with both spp. ostensibly capable of building large mounds.

Microhodotermes viator

  • collects faeces of ungulates to some extent, as food,
  • inhabits a single hive per colony, in contrast to H. mossambicus,
  • builds a low, broadly conical mound, up to 1.5 m diameter, above each hive, the latter being buried just below the general level of the ground and about 0.5 m below the apex of the mound,
  • forages over a radius of up to 45 m around the (buried) hive, by emerging from small holes at various distances from the hive, and
  • sometimes makes little piles of sticks and other litter at the entrance of these holes.

My commentary:
There are regions of winter rainfall (mediterranean-type climates) in Europe, California, Chile, Western Australia, and South Australia. However, none of these has any termite ecologically similar to Microhodotermes.

Microhodotermes viator does not extend to the 'karoid' vegetation ( and of the southwest Kalahari (it does not extend north of the Orange River ( at the longitudes of the Kalahari).

My commentary:
Microhodotermes viator penetrates the southwestern Namib.

(Please also see

Publicado el junio 8, 2023 09:15 TARDE por milewski milewski | 9 comentarios | Deja un comentario

10 de junio de 2023

A preliminary list of plant genera indigenous to both South America and Africa

(writing in progress)

My reference is Gentry A H (1993,, pages 500-547.



Publicado el junio 10, 2023 08:33 TARDE por milewski milewski | 0 comentarios | Deja un comentario

Aposematism in Anthia in South Africa

Publicado el junio 10, 2023 10:27 TARDE por milewski milewski | 6 comentarios | Deja un comentario

11 de junio de 2023

Thermoregulatory panels in the guanaco

Bare, pale skin occurs

  • on the ventral surface of the tail, extending via the buttocks to the groin, inner upper hindlegs, belly, and posterior flanks.
  • on the brisket, extending to the pits of the forelegs and the inner upper forelegs.

These two tracts, each multifaceted, are narrowly connected, to each side of a large patch of pelage on the chest.


There is an intriguing aspect of the anatomy of the guanaco, located at the abdomen ('inguinal'), near the elbow ('axillary'), on the buttocks, and on the ventral surface of the tail.

This is

  • the sharp differentiation of long pelage from apparently bare skin, and
  • the difference between the pale skin of groin, buttocks, and tail and the dark skin of the perineum.

The main function of the pale, apparently bare skin (which also seems to occur on the inner surface of the upper forelegs) seems to be thermoregulation, rather than display by means of colouration.

When the animal stands under normal conditions, the panels of apparently bare skin are 'closed', by virtue of

However, when the slight hunching of the torso is relaxed, what becomes visible is the clear distinction between the ventral pelage and the apparently bare skin,

These apparently bare surfaces presumably function to regulate body heat, via perspiration ( and and and and radiation. In cold weather, the apparently bare panels can be covered, mainly by postural adjustments including the 'clamping' of the tail.

Few ungulates on Earth possess this mechanism, which may be related to the unusually narrow 'waist' of camelids ( and

At first glance, there is little remarkable about the pale tract on the abdomen in the following ( and

However, on closer scrutiny it can be seen that there is a considerable area of pale, apparently bare skin. There is another, similar but smaller, patch of pale, apparently bare skin just posterior to the elbow.

Publicado el junio 11, 2023 05:10 MAÑANA por milewski milewski | 0 comentarios | Deja un comentario