Ecosystems and Ecology
Ecosystems and Ecology
Author: Prof Koos Bothma
Licensed under a Creative Commons Attribution license.
CASE STUDY: THE SOUTH-WESTERN KALAHARI ECOSYSTEM
The south-western Kalahari is a vast, arid ecosystem in southern Africa where ecological tolerances are
stretched to the limit in a never-ending pursuit of survival and propagation by vegetation and animals. It
will be used here as a case study to illustrate the concept of an ecosystem, although it is by no means an
intricate one.
This tumbleweed at sunset on a bare red dune near Loffiesdraai windmill in the Kgalagadi Transfrontier Park
in the south-western Kalahari ecosystem in August 1999 is the wind-blown, dried inflorescence messenger
of the Bushman poison bulb Boophane disticha
The Kalahari Sand System is the largest area of contiguous sand in the world and it underlies numerous
ecosystems and bioregions. Its sands are discussed in some detail by Dougill and Thomas (2004) in the
reference below. It stretches from the Orange River in South Africa north along eastern Namibia, western
Botswana, western Zambia and eastern Angola to the tropical south-western parts of the Democratic
Republic of the Congo, as far as 1°N. It underlies two great wetlands, the Okavango Delta of Botswana
and the Liuwa Plain of western Zambia. Its south-western corner is most arid because the mean annual
rainfall increases to the north-east. The south-western Kalahari is a semi-desert that forms a separate
ecosystem within the Savanna Biome and it contains four distinct bioregions. These bioregions contain
seven large landscape classes and 20 different landscapes based on morphology, soil and vegetation.
The seven large landscape classes are: the high dunes; the low dunes; the plains on deep, reddish sand;
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the plains and terraces adjacent to the riverbeds; the grassy pans on compact whitish calcrete outcrops;
the scattered patches of irregular dunes; and the riverbeds and pans.
The term Kalahari was probably first used by the naturalist explorer A. Smith for this region in 1834 and
refers to the Kgalagadi people who then inhabited it. The name Kgalagadi means place of thirst. Today
the south-western Kalahari forms an integral part of the Kgalagadi Transfrontier Park of some 37 991 km²
following the amalgamation of the Kalahari Gemsbok National Park of South Africa with the adjacent
Gemsbok National Park of Botswana on 7 April 1999. The official launch took place on 12 May 2000.
Inorganic components
The major inorganic components of the south-western Kalahari ecosystem are its geology, soils, climate,
and water resources.
Geological formations
The thick bed of sand that covers most of the surface of this ecosystem makes it difficult to study
the underlying geology, most of which is known only from borehole cores. The rocks below the
sands are part of the Karoo Sequence which consists of the Dwyka and Prince Albert Formations
with some dolerite intrusions as vertical dykes. The Dwyka Formation was deposited during an
ice age and consists of pebbles within a fine shale-like matrix. The Prince Albert Formation
consists of shale that was deposited in an ancient shallow sea. The pre-Kalahari surface was
dissected by rivers which drained north-eastward towards Botswana. The clayey gravel Wessels
Formation and its overlaying clayey Budin Formation originated from Karoo Sequence rocks while
the overlaying sandstone, grit and conglomerate of the Eden Formation yielded most of the sand.
All these Formations were deposited under conditions that were wetter than present. The later
calcrete of the Mokalanen Formation and sand of the Gordonia Formation indicate a change to a
more arid environment while the clayey, diatomaceous limestone of the Lonely Formation was
deposited in erstwhile lakes during a wetter phase in an otherwise arid period. The clay and sand
of the Goeboe Goeboe Formation were deposited by water flow into the now normally dry pans
and riverbeds. The Gordonia Formation represents the wind-blown sands that currently cover
much of the land surface.
There are no surface outcrops of the Wessel and Budin Formations. The Wessel Formation
consists of deeply deposited gravels that were probably derived from glacial tillite deposits in the
Dwyka Formation. The Budin Formation consists of red clay which came from the Dwyka and
Prince Albert Formations and accumulated in a pre-Kalahari riverbed. The Eden Formation is
visible on the surface along the current riverbeds, especially in the Auob River Valley. This
Formation was probably deposited as a braided river system on a low relief surface and consists
of visible but variable red, brown, yellow, cream and green sandstones, grits and conglomerate
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lenses. The sandstone sediments, that are less well consolidated than the rest, contain a network
of hollow tubes that were either created by burrowing organisms or plant roots. The Mokalanen
Formation consists of nodules which are hardpan calcrete outcrops that were deposited in an
already semi-arid environment. The Lonely Formation occurs as clayey, diatomaceous limestone
steps along the sides of some of the larger pans. These calcrete deposits contain the fossilized
skeletal remains of diatoms and gastropods (molluscs) and have been intruded by the roots of the
current vegetation. These fossils are always associated with pans and water courses and indicate
that this Formation was formed in a shallow pan or a sluggishly flowing river with some aquatic
vegetation. This probably happened during a wetter phase which occurred some 19 000 to 12
000 years ago in what was a long-term arid period when windblown sand was already present.
The Goeboe Goeboe Formation occurs as horizontal sediments on the pans and riverbed floors.
These sediments are relatively young and some are still forming at present. The main
components are quartz, calcite, montmorillonite and feldspar. The surface sands of the Gordonia
Formation are the most abundant geological feature in this ecosystem. They consists of sand of
varying colour depending on the degree of iron dioxide which is present. These sands contain the
iron-rich minerals magnetite, haematite and ilmemite among other heavy minerals such as garnet,
rutile, tourmaline and zircon.
Geomorphology
There is a variety of dunes and dune patterns that have formed on the surface. Near the
riverbeds the dunes are simple and linear but they become partially transverse and tend toward
barchanoid ridges further away. In isolated spots, irregular, ellipsoidal, parabolic dunes have
formed where the surface of older, stabilized dunes have become mobile again following the loss
of vegetation and wind action. In other parts dunes are less developed while there are two major
riverbeds. These rivers seldom flow and only do so following excessive rainfall in their catchments
areas in Namibia. The Auob River flows more regularly than the Nossob River. Without its sandy
surface cover and with the current arid climate the south-western Kalahari would be a young
plateau where vertical erosion by the rivers that cross it has ceased. Some of the pans along the
Nossob Riverbed were formed when the flow of water could no longer remove the sand load
rapidly enough. The pans away from the rivers have become deflated by wind action and
trampling by larger wildlife.
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The most arid south-western part of the south-western Kalahari ecosystem is covered by extensive parallel
red dunes that are interspersed by well-vegetated interdune valleys as is shown south of the Auob River in
this aerial view at sunrise in the Kgalagadi Transfrontier Park in the south-western Kalahari ecosystem in
August 1999
Climate
The south-western Kalahari developed after the dissection of the topography during the wetter
Miocene period which lasted from some 24 to 7 million years ago when the then existing river
valleys were filled with sandy clay. Parts of these sediments were then re-deposited as poorly
rounded and sorted conglomerates. When an arid period started some 7 million years ago the
calcrete and silcrete deposits and outcrops were formed. Another wetter period then caused the
onset of active erosion by rivers that now drained towards the south. The most recent wet phase,
which lasted from some 19 000 to 12 000 years ago, allowed diatoms and molluscs to flourish in
the pans. A subsequent arid period and the prevailing winds then formed most of the linear dunes
and filled parts of the Nossob riverbed with deep sediments. Currently the ecosystem is
experiencing a relatively wetter period which has stabilized the sand and vegetation.
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Sociable weaver birds Philatairus socius are typical of the south-western Kalahari ecosystem where
they nest in dead trees such as this one near Dankbaar windmill in the Kgalagadi Transfrontier Park in
June 1982
The current wide ambient temperature range and erratic rainfall create an annual hot, dry season,
a hot, wet season and a cold dry season. The erratic annual rainfall usually varies from 185 to
230 mm, but some years are exceedingly dry and others exceedingly wet. The month of highest
rainfall is January and the annual rainfall is cyclic with nine years of high rainfall followed by nine
years of low rainfall. The mean annual rainfall increases north-eastward into Botswana with a low
mean of 150 mm per year in the extreme south-western part of the south-western Kalahari
ecosystem. The ambient temperature varies from -10.3° C in the winter to 45,4° C in the summer,
but open sand surfaces will daily reach a peak temperature of 70° C or more in the summer. Light
snow in midwinter has been recorded but is a rare phenomenon. In the winter ice may rarely form
on the dune surfaces when they are wet.
Soils
The aeolian soils of the south-western Kalahari are broadly called Kalahari sands. However, there
are five distinct groups of Kalahari sand, with the red and yellow sands being dominant. These
soils support the terrestrial organisms and they anchor the plants. Through colloidal clay-humus
complexes the soils also provide solutions from which the plants obtain water and mineral
nutrients and provide a habitat for the micro-organisms that are essential in the decomposition of
organic matter that recycle vital biochemicals.
The red and yellow Kalahari sands form the parent material of the red Hutton and yellow Clovelly
soil forms. These soils vary in thickness from a few centimetres to several metres or deeper. Soils
near the riverbeds contain limestone materials which vary in colour from white to yellowish-white
and grey. The uppermost layer of these soils is often hard and impervious and breaks into blocks
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of boulder limestone. Soils in the pans contain calcareous materials and soft, powdery lime that
absorbs water well.
A tumbleweed; the windblown, dried inflorescence of the Bushman poison bulb Boophane disticha;
that has become lodged near a silver cluster-leaf tree Terminalia sericea near Loffiesdraai windmill in
the Kgalagadi Transfrontier Park of the south-western Kalahari ecosystem in January 1997. These
trees only grow on areas with deep sand
The main Kalahari sand groups are red eutrophic, fine and medium sandy soils of the Hutton soil
form; yellow-brown eutrophic and calcareous fine and medium sandy soils of the Clovelly soil
form; deep calcareous reddish-brown and grey-brown loam and clay loam soils of the Oakleaf,
Dundee and Valsrivier soil forms; brown calcareous sandy clay loam soils of the Swartland soil
form; and shallow brown and yellow-brown calcareous sands and loams of the Mispah soil form.
The Hutton soil form mainly gives rise to the typical red dunes of the south-western Kalahari.
These sands are largely aeolion (wind-blown) in nature and the quartz grain surfaces are covered
in iron oxide. The quartz grains are well-rounded and sorted as a result of the wind action. These
homogeneous sands are freely permeable to water and absorb most of the rainfall rapidly to store
moisture deeply, with a good grass cover developing in consequence. This moisture lasts well
into the winter and the sands are penetrated on the surface by burrowing animals, such as
gerbils, golden moles and mole-rats.
The Clovelly soil form is similar to the Hutton soil form in its aeolian origin and the texture of its
sands. However, the quartz grains have a yellow to yellow-brown colour due to different chemical
and mineralogical properties. The soils are eutrophic with little horizon differentiation and
therefore have a high exchange of calcium, magnesium, sodium and potassium. Some of these
soils occur as undulations and dune-like formations on the banks of and in the immediate vicinity
of the Auob and Nossob riverbeds. Others occur on the eastern, leeward side of pans and
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deflected basins. These sands are freely permeable to water but are underlain by an
impermeable calcrete substratum. The surface sands form a habitat for some plants and for
burrowing animals such as aardvarks, porcupines, springhares, mole-rats, mongooses, honeybadgers and a host of mice and rats.
Brant’s whistling rat Parotomys brantsii is a typical, diurnal, rodent that burrows extensively in the
south-western Kalahari ecosystem and feeds on the succulent stems of grasses and the leaves of
bushes. This one was photographed in the Kgalagadi Transfrontier Park in August 1999
The Oakleaf, Dundee and Valsrivier soil forms are confined to the beds and floodplains of the
Auob and Nossob Rivers and occur as narrow but continuous strips. The soils are alluvial in origin
and often consist of loam or clay loam. They vary in colour from reddish-brown to brown and
grey-brown and commonly contain lime concretions and nodules in the subsoil. These soils are
alkaline with high concentrations of soluble salts. Their origin is mainly Karoo sediment rocks and
mica with poor water penetration. The mica originated in the catchment areas in Namibia and is
abundant in the Nossob River. These soils become impermeable when wetted and have a low
productivity. Soils of the Swartland soil form are the most important component of the pans. They
occur as thin, light brown topsoil with an extremely hard consistency and are highly calcareous
and alkaline.
In terms of plant producers the soils of this ecosystem are well supplied with the essential
nutrients for plant growth and they are relatively free from the effect of leaching. However, the
soils are generally low in nitrogen while the Hutton soil form is also low in phosphate. Cattle that
graze the available require phosphate licks. The soils of the pans and riverbeds are more fertile
than those of the dunes as they have higher phosphate levels. Consequently these pans and
riverbeds form an important habitat for wildlife.
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The pans and riverbeds are normally dry and the rivers flow infrequently at intervals of several
decades. The pans away from the riverbeds require self-maintenance because they are not
subject to even occasional flooding from other regions and the combined interaction of their biotic
and abiotic components is essential in these processes. Artificial waterholes may be highly
mineralized and many contain high concentrations of toxic elements such as arsenic, mercury
and nitrates (see Bothma 2005 below). The pans also form an important source of essential
minerals for the larger herbivores.
Antelopes such as this gemsbok Oryx gazella in the dry Nossob riverbed of the Kgalagadi Transfrontier Park
in the south-western Kalahari ecosystem in July 2001 eat the soil of pans and other brackish areas to
supplement mineral deficiencies such as salt in their diet
Organic components
The main environmental factor that effects the production of the organic trophic levels in the southwestern Kalahari ecosystem is sufficient rainfall. It has been shown that even the denuded destruction
zone around a waterhole will be repopulated by the best possible grazing following abundant rainfall.
Drought and rainfall periodicity therefore have a significant impact on the herbaceous plants, but the
deep-rooted woody plants are able to survive long periods of minimal rainfall.
Vegetation
The vegetation of the south-western Kalahari can be placed into 20 landscapes, which are the
focal points for its large animals. These landscapes were described with the aid of Landsat ETM
satellite images and 1:5000 orthophoto maps and earlier vegetation and habitat descriptions.
There are seven large landscape groups in the south-western Kalahari ecosystem which contain
the following landscapes:
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The parallel, grass-covered, high dunes near the banks of the Auob River mainly contain the grey
camel thorn tree Acacia haematoxylon as a woody plant and are dominated by the tall dune
bushman grass Stipagrostis amabilis. Prostrate creepers such as the moisture-rich gemsbok
cucumber Acanthosicyos naudianus and tsamma melon Citrullus lanatus occur seasonally on the
naked dune crests and are an important water resource for wildlife.
The tsamma melon Citrullus lanatus of the south-western Kalahari ecosystem is a major source of
moisture for wildlife and the San people. Tsamma melons, such as these near Loffiesdraai in the
Kgalagadi Transfrontier Park in January 1997, consist of up to 90 per cent water
The irregular high duneveld occurs south of the Auob River and between the Auob and Nossob
Rivers in the south. It contains scattered grey camel thorn trees, the black thorn Acacia mellifera
and the shepherd’s tree Boscia albitrunca as a shrub, the latter acting as ideal cover for the larger
carnivores. The grasses vary but the three-thorn bush Rhigozum trichotomum dominates the
calcareous soils in the valleys between the dunes and its leaves and flowers are an important
source of browse.
Mainly close to but north of the Auob River and on both sides adjacent to the Nossob River the
parallel high dunes support an open tree savanna mainly consisting of the camel thorn tree
Acacia erioloba and the black thorn tree, with a variety of other woody shrubs and grasses. This
landscape forms an important grazing area for wildlife that move there from the riverbeds at
times.
The low dunes mainly occur in the interior areas away from the riverbeds. A combination of the
camel thorn tree and the mostly unpalatable Kalahari sour grass Schmidtia kalahariensis forms
an open tree savanna in the northern part of the ecosystem. This landscape contains numerous
herbivores such as springbok, blue wildebeest and gemsbok, and carnivores such as lions,
cheetahs, spotted hyaenas and black-backed jackals.
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The riverbed of the fossil Nossob River, as seen here at Lijersdraai in the Kgalagadi Transfrontier Park
in the south-western Kalahari ecosystem in January 1984, has an abundance of sweet grazing during
the rainy season
The irregular low dunes are a large landscape of grass-covered irregularly shaped dunes in the
more arid southwestern part of this ecosystem north of the Auob River. It contains numerous
large pans and the grey camel thorn tree is the most conspicuous component of the woody
vegetation. There is a large variety of grasses and forbs. The vegetation of the dunes differs from
that of the interdune valleys with the black thorn tree, the shepherd’s tree and the grey camel
thorn tree being the most conspicuous woody plants. The interdune valleys mainly contain the
grey camel thorn tree, the blackthorn and the three-thorn bush.
The second large landscape of this ecosystem consists of the undulating low dunes that occur
throughout the area between the Auob and the Nossob Riverbeds. The prominent woody plants
are the camel thorn tree, the grey camel thorn tree and the shepherd’s tree. The landscape
contains several palatable species of grass and various types of dwarf shrub.
There are two types of plains landscape on reddish sand. Grey camel thorn trees and dune
bushman grass occur in large patches throughout the interior regions away from the riverbeds but
the dunes are seldom more than 6 m high. Other palatable grass species attract large herbivores
to this landscape. The flat grassy plains with scattered shrubs that also occur on reddish sand in
the central interior region are slightly undulated and contain scattered but low grey camel thorn
trees.
The calcrete outcrops, terraces and floodplains along the Auob and Nossob Rivers form an
important wildlife habitat. They contain scattered individual camel thorn, grey camel thorn and
shepherd’s trees and some dwarf woody shrubs but the grass layer is poorly developed.
There are four types of landscape on whitish sand on the plains and terraces adjacent to the
riverbeds and grassy pans. The scattered large camel thorn tree, three-thorn bushes and small
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bushman grass Stipagrostis obtusa clumps occur on slightly compact calcareous and whitish
sand in the dune valleys, near pans and adjacent to the Auob and Nossob Rivers and provide
shade and palatable forage to large herbivores in the wet season. After rains these flats are
covered in yellow beds of the devil thorn Tribulus zeyheri. The black thorn, three-thorn and small
bushman grass landscape of the riverbed terraces occurs on the calcareous terraces near pans
and the rivers and also provides good grazing to short-grass grazers such as blue wildebeest in
the wet season. A small landscape unit of dwarf ganna shrubs Solsola spp, mixed with the kapok
bush Eriocephalus spp., occurs on the edges of the pans and calcareous outcrops adjacent to the
Nossob River, while large patches of uniform small bushman grass form a further landscape unit
in local patches on whitish, compact sandy soils on terraces and floodplains next to the Nossob
River.
The sap of the bulb of the Bushman poison bulb plant Boophane disticha as shown here in the interior
sandveld dunes of the Kgalagadi Transfrontier Park in the south-western Kalahari ecosystem in June
1997, is used as a toxin in the poison arrows of the San people when hunting
The riverbeds and pans contain six types of landscape. The pans both have bare floor surfaces
and are commonly known as salt pans, or they have grassy surfaces. Both types occur on
whitish, strongly alkaline calcareous and silted soils. The vegetation on and around a pan differs
markedly from that of the surrounding area and often shows concentric zoning. Around some of
the larger pans in the northern part of this ecosystem, stands of the worm-bark false-thorn tree
Albizzia anthelmintica occur. The riverbeds contain four types of landscape with a dense layer of
white buffalo grass Panicum coloratum and the scattered large camel thorn trees in the northern
part of the Nossob riverbed. This grass offers good grazing to the larger antelopes. An isolated
stand of the blue bush Lebeckia linearifolia occurs in the lower Auob and Nossob Riverbeds and
on some high parallel dunes in the vicinity. There is no grass cover in this landscape unit. From
its confluence with the Auob River northward for some 160 km a landscape that is characterized
by shrubs and scattered camel thorn trees with a limited grass cover occurs. The Auob Riverbed
represents a narrow zone of large camel thorn and grey camel thorn trees on moderately
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compacted calcareous sandy soils while the dominant types of grass are the unpalatable sour
Kalahari grass and the palatable small bushman grass. The final landscape is the striking and
highly irregular dune landscape with its striking ellipsoidal parabolic dunes which are only found in
a few isolated places within the interior duneveld. The only woody plants in this landscape unit
are a few black thorn and shepherd’s trees and shrubs.
Floristically the south-western Kalahari ecosystem is impoverished with a reduced landscape
differentiation. The camel thorn tree, the grey camel thorn tree and the shepherd’s tree are
characteristic of several types of landscape and are all listed as protected trees in the National
Forests Act of South Africa (Act 84 of 1998). The camel thorn tree has a significant ecological role
for numerous types of animal for feeding, nesting or resting. Grazing impacts are localized by a
natural rotational grazing system that involves localized and long-distance movements by the
major herbivores, often following rainfall. The interior dunes and plains are only utilized by wildlife
during the wet season.
Geology, soil and climate have therefore dictated the nature and development of the vegetation of
the south-western Kalahari. In turn the vegetation dictates the number, distribution and type of
larger herbivores that can be sustained there. Consequently it also dictates the number and
distribution of those larger carnivores that prey on these herbivores.
The cheetah Acinonyx jubatus often utilises the open Nossob riverbed of the Kgalagadi Transfrontier
Park in the south-western Kalahari ecosystem, as seen here in January 1975, as a hunting ground
because these open plains do not impede its high-speed chases
Animals
The south-western Kalahari ecosystem is the realm of a surprisingly rich invertebrate fauna about
which little is known. The invertebrate faunal complement includes 37 genera and 51 species of
sand-adapted tenebrionid beetle which live in the dunes and form 60 per cent of all the beetles of
the south-western Kalahari.
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Of the vertebrates, the reptiles all have arid zone affinities and this ecosystem coincides with a
number of distributional range limits. Endemic taxa include the gecko Colopus wahlbergi furcifer
and the Kalahari serrated tortoise Psammobates oculifer. The poorly known blind snake Typhlops
boylei also occurs. There is also a range of amphibians, with the bushveld rain frog Breviceps
adspersus adspersus, the giant bull frog Pyxicephalus adspersus adspersus and the Tremelo
sand frog Tomopterna cryptotis reaching their southernmost distribution limit in this ecosystem.
Snakes such as this puff-adder Bitis arietans at Gharagab windmill in the Kgalagadi Transfrontier Park
in January 1978 are abundant in the south-western Kalahari ecosystem and are especially deadly to
cats such as the cheetah, leopard and lion
The birds of the south-western Kalahari are sedentary, insectivorous or carnivorous, and nongregarious; or they are nomadic granivores that are gregarious even when they are breeding. All
the ground-dwelling sedentary birds are cryptically coloured to avoid predation. Breeding is
initiated in most species by the onset of the wet season or by associated ecological effects. Nest
orientation is related to the season of breeding and capitalizes on maximal shade in the hot
season. Evaporative cooling is employed by all the birds of this ecosystem where surface water is
a rare commodity. The use of large communal nests by the sociable weaver Philetairus socius is
also a thermoregulatory strategy. The ostrich Struthio camelus is a large terrestrial and
herbivorous bird.
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The huge sociable weaver Philatairus socius nest in a dead camel-thorn Acacia erioloba tree near
Ardlamont windmill in the Kgalagadi Transfrontier Park in the south-western Kalahari ecosystem in
1991 could contain op to 300 nest chambers which are occupied by a pair of birds each
This male ostrich Struthio camelus in the Nossob riverbed in the Kgalagadi Transfrontier Park of the
south-western Kalahari ecosystem in July 2001 represents the largest, living terrestrial bird in the
world
Much of the plant production in the south-western Kalahari is utilized by the rodent complement
whose populations fluctuate greatly with the amount of rainfall received and therefore the amount
of plant food being produced. In turn this affects the occurrence and abundance of raptors such
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as the tawny eagle Aquila rapax, martial eagle Polemaetus billicosus, bataleur Terathopius
ecaudatus and southern pale chanting goshawk Melierax canorus, and the smaller mammal
carnivores such as the Cape silver fox Vulpes chama, black-backed jackal Canis mesomelas and
caracal Caracal caracal which mainly feed on the rodents. There are 17 species of rodent that are
known to occur in the south-western Kalahari ecosystem, with their sizes varying from as little as
5 g to 3 kg, with the majority weighing less than 100 g. Most of the rodents are diurnal but some
activity will continue on moonlit nights. Only the common mole-rat Cryptomys hottentotus is totally
fossorial. Most of the rodents are granivorous but some are also partially insectivorous in their
diet. The rodent mole and springhare Pedetes capensis eat a variety of plant material. Major
fluctuations in the rodent population occur mainly in response to rainfall fluctuations. The hairyfooted gerbil Gerbillurus paeba and the four-striped grass mouse Rhabdomys pumilio are,
however, consistently numerous and support the maintenance of a minimum raptor and mammal
carnivore population. Most of the reproductive activity happens in the hot, wet season. The lack of
large diversity in the rodent population is probably caused by the absence of particular habitat
requirements although the species diversity in this ecosystem is larger than expected.
The tree rat Thallomys paedulcus, photographed in January 1985 at Loffiesdraai windmill in the
Kgalagadi Transfrontier Park of the south-western Kalahari ecosystem, utilises the camel-thorn tree
Acacia erioloba as its habitat where it feeds nocturnally on the fine leaves. These trees form a habitat
and source of food for a variety of animals
The south-western Kalahari ecosystem contains a relatively small population of smaller
carnivores. The yellow mongoose Cynictis penicillata is common but prefers a dune habitat while
the suricate Suricata suricatta prefers a riverbed one. The other species show no clear habitat
preference. The small black-footed cat Felis nigripes is rare as this ecosystem is at the western
end of its distributional range. The only other small cats that occur in the south-western Kalahari
are the wildcat Felis sylvestris and the caracal. The slender mongoose Galerella sanguinea is
encountered occasionally along the riverbeds while the banded mongoose Mungos mungo is
known only from rare sightings. Invertebrates, reptiles, rodents, hares, birds and smaller antelope
form the main diet for the wildcat and the caracal. Foraging honey badgers Mellivora capensis are
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frequently accompanied by chanting goshawks and occasionally also by black-backed jackals.
Many rodents that are dug out of their burrows by the badgers and manage to escape capture by
the badgers are then captured by the goshawks and jackals in a form of symbiotic hunting. The
aardwolf Proteles cristatus is a specialized carnivore that almost entirely feeds on long-nosed
harvester termites of the genus Trinervitermes.
This suricate Suricata suricatta attacking a scorpion at Twee Rivieren in the Kgalagadi Transfrontier
Park of the south-western Kalahari ecosystem in January 1989 is a small, diurnal, burrowing and
sociable carnivore that prefers the riverbeds as habitat and mainly eats invertebrates
The canids are represented by three medium-sized species which includes bat-eared fox Otocyon
megalotis, Cape silver fox and black-backed jackals. Their diet mainly consists of smaller
animals, with the bat-eared fox being mainly insectivorous in diet. In the south-western Kalahari
ecosystem Cape silver fox and black-backed jackal are not known to attack the lambs of smaller
antelope and their largest prey seems to be the springhare.
In the Kgalagadi Transfrontier Park of the south-western Kalahari ecosystem, the bat-eared fox
Otocyon megalotis as shown here in the Auob riverbed in July 1981, is a nocturnal insectivorous
carnivore
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There are three types of hyaena in the south-western Kalahari ecosystem, with the aardwolf
specializing on long-nosed harvester termites, the brown hyaena Hyaena brunnea being mainly a
scavenger and the spotted hyaena Crocuta crocuta a scavenger and an adept hunter when
hunting as a pack. Brown hyaenas will also eat wild fruits, including the moisture-rich tsamma
melon, when they are available. The spotted hyaena is dependent on a regular surface water
supply.
The larger cats include lions Panthera leo, leopards Panthera pardus and cheetah Acinonyx
jubatus and they all hunt mammal prey opportunistically. Consequently, their survival depends
largely on the abundance of ungulates such as the gemsbok, blue wildebeest, eland, red
hartebeest, springbok, grey duiker and steenbok which in turn is dependent on the abundance of
rainfall and the resultant vegetation quantity and quality. These herbivores move locally and
regionally in response to rainfall and will suddenly congregate in large numbers in the riverbeds
after suitable abundant rain. The provision of artificial waterholes has, however, caused some of
the herbivore population to become sedentary. In times of drought the larger carnivores will
readily make use of other prey such as the smaller carnivores, porcupines Hystrix
africaeaustralis, the smaller and more sedentary antelope and even springhares. Cheetah seldom
take prey larger than springbok Antidorcas marsupialis and are mainly found along the riverbeds
which these antelope favour and which provides an ideal hunting ground for a high-speed chase.
Leopard and lion utilize the larger herbivores such as the eland, gemsbok and blue wildebeest too
but they are opportunistic hunters and will prey on whatever suitable prey becomes available. The
lion is the apex predator in this ecosystem.
The fossil riverbeds such as that of the Nossob River at Kwang in the Kgalagadi Transfrontier Park of
the south-western Kalahari ecosystem contain many ancient loops and ox-bows where lions Panthera
leo may find shelter in the shade on a hot day such as in January 1984
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Ecosystems and Ecology
Conclusions
The south-western Kalahari ecosystem is relatively waterless with erratic and low rainfall. It is a largely
featureless and marginal habitat and not as complex as some other ecosystems. Nevertheless it consists
of a matrix of food chains of a tenuous nature. Any disturbance in one element is likely to create ripple
effects throughout the ecosystem. The best management approach seems to be to have as little as
possible human intervention. The provision of artificial water may be the only intervention that could
increase the ecological capacity of this ecosystem for wildlife. Despite appearing to be ancient, the
current ecosystem seems to have developed relatively recently following an extensive wet period that
ended some 12 000 years ago, although it is currently experiencing a wetter phase within a dry period. If
and when environmental conditions change again, the current delicate equilibrium is likely to shift as
thresholds of tolerance are passed.
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