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The kalahari environment, by David S. G. Thomas and Paul A. Shaw, Cambridge University Press, Cambridge, Number of pages: Price $55 ($).
Table of contents
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- Kalahari Solar Power Project
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- Historical background
- The Plight of the Kalahari Lions | Natural Selection
One of its favourite dishes is the gemsbok, but when they are not available lions also eat antelopes, porcupines and other small mammals. The Kalahari lion is lighter and males have black manes. Social weavers Social weavers are a sub-species of the weaver birds, named for their ability to weave very large communal nests. The communal nests can measure up to 6 meters long and 2 meters high, and can weigh as much as 1, kg while housing up to birds. The nests are built with insulated walls to maintain a stable temperature inside the nest to keep the weavers warm at night and cool during the day.
Like the gemsbok, social weavers seldom need to drink water. Camelthorn tree The camelthorn tree is an acacia tree endemic to the Kalahari region. It is practically the only tree that has adapted to the Kalahari environment and is thus a key component of the ecosystem. The camelthorn tree provides nutrients for other plants and shrubs, which grow more densely around the trees, while their leaves provide food for animals. The shade of the tree also serves as a refuge for animals during the day and the social weavers build their nests in its branches.
Hoodia cactus The Hoodia cactus thrives in extremely high temperatures, and takes many years to mature. The San people, who have inhabited the Kalahari for more than 22, years as hunters-gathers, have traditionally eaten this cactus to stave off hunger and thirst during long hunting trips or times of drought. A few years ago, scientists identified the molecule present in the Hoodia cactus which fools the brain into believing it is not hungry. Pharmaceutical companies have since started conducting clinical tests with the intent to sell diet pills using the unique molecule featured by Hoodia.
The San people, who currently live in poverty, are demanding a share of the profits for the use of their traditional knowledge and for the right to access this resource. All the above species are interdependent. The Kalahari Lion feeds on the gemsbok. The gemsbok feeds on plants that hold water such as the Hoodia cactus.
The weaver makes its nest in the camelthorn tree, and so on. When one species becomes extinct, it has a ripple effect on a number of other species. Although none of the above species are currently threatened by extinction, others are not as lucky. Endangered species in the Kalahari include the African wild dog, the African wild cat, the Cape vulture and the aardvark. However, generally speaking, endemic species are more vulnerable to extinction than other species as they are able to survive only under very specific environmental conditions. Thus efforts must be made to ensure unique drylands species such as the meerkat, the gemsbok, the Kalahari lion, social weavers, the camelthorn tree and the hoodia cactus continue to thrive.
About the Convention. Strategic Plan for Biodiversity Mechanisms for Implementation. The Cartagena Protocol. Thematic Programmes.
First, the activity data were compared with and without the influence of a specified variable to investigate the effect of said variable. Thereafter, the means of the activity data were determined according to each class of the specified variable and compared with each other. To investigate the effect of rainfall on herd size, rain was accepted as being present only when a minimum of 10 mm had fallen in a particular month.
This was to ensure that a sufficient amount of water had been received to induce vegetation sprouting. The generalised linear model incorporated a lag effect in order to accommodate a response time for vegetation after the occurrence of rain. A total of 17 rainfall stations are located in the Kalahari Gemsbok National Park.
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- Sustainable Livestock Management in the Kalahari.
- Database and Expert Systems Applications: Proceedings of the International Conference in Vienna, Austria, 1990;
- Springbok behaviour as affected by environmental conditions in the Kalahari.
- Disorder in Physical Systems: A Volume in Honour of John Hammersley;
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A georeferenced grid was created to match specific rainfall stations with herd locations. Two thousand questionnaires were distributed and The researcher completed Observations lasted from one to more than ten minutes, most observations not continuing more than three minutes. Food item selection was considered at growth form level.
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Tree leaf consumption remained low throughout the day. Shrubs were consumed at a lower rate the later in the day it became, possibly due to decreasing moisture content. Diet selection of springbok is affected by season. An investigation into the seasonal changes in nutrient content of springbok food plant species in the Kalahari showed that the crude protein and phosphorus levels were especially low during the cold-dry season Stapelberg et al. Browse species had a higher crude protein and phosphorus content than grass species.
Consequently, springbok could consume a higher quality diet if they changed their feeding strategy to include more browse than grasses in their diet during the winter months.
Springbok were observed to eat Rhigozum trichotomum leaves throughout the year, but especially so when the plants were freshly sprouting. This supports observations by Bothma , who described a rapid response by springbok to newly emerging green sprouts of R.
This species was not specifically selected as food during times when a diversity of fresh plant growth was present, except when in flower. When flowering, springbok were observed to move through R.
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It has also been reported that springbok consume plant underground storage organs as a source of moisture Williamson , but that could not be confirmed during the present study. No data were collected on nocturnal feeding by public respondents because of tourist travel restrictions, and the data collected by the researcher were mostly qualitative. Springbok were observed to feed at night during all three seasons of the year. Two peak feeding times were reported during the hot-dry season as opposed to one in the cold-dry and hot-wet seasons. Feeding periods were also longer during the two dry seasons than in the wet season.
These observations could indirectly be seen as supporting the hypothesis that animals feed on plant material at night because of elevated moisture levels. Nocturnal feeding behaviour could be a form of depredation prevention by the herd through having vigilant individuals awake while some continue resting Siegfried, ; Treves, These licks are mostly associated with pans Van Rooyen et al. In the present study, utilisation of such licks was especially prominent around the Kannaguass waterhole in the Nossob riverbed.
It is unclear whether this was the case in the present study, as springbok were observed to drink water intermittently while also utilising licks. The licks that were observed all occurred within the piosphere zone Jeltsch et al. Although only 21 activities were listed in the questionnaire, up to 31 different activities were specified by respondents. The mean percentage of springbok involved in these activities over all time periods during the whole study period showed that feeding in sunlight occurred most often Six of all the recorded activities related directly to feeding.
When these two activities were compared with the rest of the activities by Analysis of Variance of Contrast Variables, it was found that feeding in the sunlight occurred significantly more frequently than all other activities Table 1. Frequency of feeding in the shade 2. The lack of a significant difference in the frequency of shaderelated activities feeding, standing, lying down and walking indicated that the time spent in the shade was divided equally between these activities.
Springbok herds were often observed to rest in the shade during the heat of the day.
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During such resting periods, different animals in the herd would be involved in different activities, such as standing, walking and feeding. The main objective of spending time in the shade other than feeding is assumed to be to rest. Daily trends of all activities are presented in Figure 3. Fewer springbok were observed to be feeding in the sunlight the later in the day it became up to approximately Figure 3a.
Activities that reached their peak frequency in the hour during sunrise included sleeping in direct sunlight Figure 3d and playing in the shade Figure 3f.
Feeding and playing in direct sunlight Figures 3a and 3f reached their peak frequency during early morning, while lying down and playing in the shade Figures 3c and 3f occurred at their lowest frequency then. Lying down in direct sunlight Figure 3c reached a peak during the late morning, while feeding in the shade Figure 3a and standing in direct sunlight Figure 3b had a low frequency of occurrence then. Activities that peaked at midday included feeding in the shade Figure 3a and standing in direct sunlight Figure 3b , while feeding in direct sunlight Figure 3a occurred at its lowest frequency.
During early afternoon standing and lying down in the shade Figures 3b and 3c and walking in direct sunlight Figure 3e had a high frequency of occurrence, whereas lying down in direct sunlight Figure 3c did not occur often then. A generalised linear model was used to test the null hypothesis that the frequency of an activity in springbok herds did not differ significantly between the three different seasons. Nonetheless, they showed a few notable results.
This may suggest that winds from the north to northeast are hotter winds that add to thermoregulation stress in springbok. Springbok may subsequently adapt by changing their feeding behaviour to specifically feed in the shade. Rainfall is a key environmental factor in the southern Kalahari Van Rooyen et al. Herd sizes varied between seasons and months. The largest mean herd sizes were recorded during June at The largest herd recorded during the study period consisted of springbok found in the far northern part of the Nossob riverbed, close to Kannaguass waterhole, in April Springbok herd sizes therefore increased during the cold-dry season and decreased during the hot-dry season.
This phenomenon appeared to be linked to specific rainfall patterns rather than to rigid seasonal boundaries. Bothma and Mills , although using total counts instead of herd sizes, reported similar trends. However, during the present study period, blue wildebeest were either not present or were some distance away from the springbok herds studied in Blue wildebeest were sometimes witnessed to feed in conjunction with springbok, as if moving in a convoy.
Moreover, gemsbok were close to springbok more often than blue wildebeest. According to Knight , the blue wildebeest grazes at a higher level than the springbok and seems to precede springbok as low-level grazer. Qualitative observations confirmed this during the study period.
Blue wildebeest have wide muzzles that are suited for grazing relatively close to the ground. The results of the present study suggest that springbok and blue wildebeest coexist in the Kalahari by avoiding competition through niche separation. They also suggest that although these two animal types occur together, springbok and blue wildebeest more often prefer not to feed in close proximity. A similar situation occurs between plains zebra Equus quagga , white-bearded wildebeest Connochaetes taurinus subsp.
The Thomson's gazelle is morphologically similar to the springbok and is also a selective feeder.
The Plight of the Kalahari Lions | Natural Selection
However, in their study, Sinclair and Norton-Griffiths concluded that the white-bearded wildebeest were regulating the Thomson's gazelle in the Serengeti through competition. Competition can therefore not be excluded as a factor regulating the springbok population in the Kalahari and more research on this aspect is required. Gemsbok are considered roughage feeders and the majority of their diet consists of grass.