Augrabies Falls National Park Research Articles

Seismicity and neotectonic uplift in the Augrabies Falls National Park, Namaqualand, Northern Cape, South Africa

Gneissic rocks in the Augrabies Falls National Park are part of the Proterozoic Namaqua-Natal mobile belt. Finding neotectonic evidence in old terranes is always not an easy task. In South Africa, the mid-Miocene is believed to be the beginning of neotectonics. This study investigated the occurrence and recurrence of earthquake activity, occurrence of faulting, jointing, uplift, and potholes in the gneisses cropping out around the Augrabies Falls area that may account for neotectonics. A historic seismic event obtained from the United States Geological Survey (USGS), and seismic epicenters downloaded in October 2015 from IRIS earthquake browser and overlaid on a satellite image with digitised faults and lineaments, indicates that the area is seismically active and is a zone of seismic risk. Potholes occurring today on a dry surface at approximately 613 m above sea level are a direct consequence of the Griqualand-Transvaal neotectonic uplift, which generated a major fault along which water flows continuously. It is concluded that the Augrabies Falls National Park area is a zone of neotectonics. This zone should not be considered for the storage of nuclear wastes.

Habitat Suitability Model for Black Rhinoceros in Augrabies Falls National Park, South Africa

To assist with identifying land for reintroduction, a habitat suitability model (HSM) for black rhinoceros (Diceros bicornis) was developed in the arid Augrabies Falls National Park, South Africa, from records of sightings, feeding trails and dung middens. Logistic regression and Bayesian Information Criterion were employed to construct and select the best HSM from >35 eco-geographical variables. The modelled and the observed distributions of black rhinos did not differ (P = 0.323) and k-fold cross-validation confirmed the model's ability to predict the distribution of independent data. The HSM consisted of five variables: availability and equitability of three preferred foods, distance to roads, habitat heterogeneity, slope and shade. The variables ‘distance to water’ and ‘rockiness’ were also included in the confidence set of models. Only 50% of the study area had a habitat suitability exceeding 11%, but featured 89% of rhino locations. Of 10 vegetation communities, two with high volumes of favourite foods were preferred. Feeding areas with a high density of preferred food plants were also highly preferred. The riverine vegetation community was not preferred, because its abundant browse was not of the preferred species. The apparent avoidance of roads warrants more research and the attention of park managers.

Spatial and temporal scaling in habitat utilization by klipspringers (Oreotragus oreotragus) determined using giving‐up densities

AbstractAn animal's pattern of habitat use can reveal how different parts of its environment vary in quality based on the costs (such as predation risk) and benefits (such as food intake) of using each habitat. We studied klipspringer habitat use in Augrabies Falls National Park, South Africa using giving‐up densities (GUDs; the amount of food remaining in a resource patch following exploitation) in experimental food patches. We tested hypotheses related to how salient habitat variables might influence klipspringers' perceptions of foraging costs. At small spatial scales (3–4 m), klipspringer GUDs did not vary with cover and open microhabitats, or with the four cardinal aspects (shading) around shrubs. Adding water adjacent to food patches did not influence GUDs, showing that water is not a limiting complementary resource to food. Generally, klipspringers do not appear to be physiologically constrained. There was no difference in GUDs between four daily time periods, or between summer and winter; however, a significant interaction effect of time‐of‐day with season resulted from GUDs during the midday time period in winter being significantly higher (perceived value lower) than during the same time period in summer. At moderate spatial scales (10–60 m), klipspringer GUDs increased with distance from rocks because of increased predation risk. Based on GUDs collected at the largest scale (two 4.41‐ha grids), klipspringers preferred foraging at greater distances from drainage lines and on pebble and cobble substrates. Overall, this study has shown the efficacy of measuring GUDs to determine klipspringers' habitat utilization while foraging.

Mapping the Landscape of Fear of the Cape Ground Squirrel (Xerus inauris)

The suitability of a habitat to an animal includes food availability, physical and climatic factors, population interactions, and safety from predators. Mappings of vegetation, soils, and microclimates across ecological landscapes have become standard and important tools for assessing an animal's habitat. More elusive to the researcher, yet of equal importance to the animal, has been the ability to map the predation risk perceived by an animal. Laundreet al., in developing the concept, defined the landscape of fear as the spatial map of the animal's predation cost of foraging. We mapped this landscape of predation costs by measuring the use of depletable food patches (yielding giving up densities (GUDs)) arranged as a grid across the landscape of interest. The landscapes of fear for 3 colonies of Cape ground squirrels (Xerus inauris) in Augrabies Falls National Park, South Africa, revealed large and distinct spatial variation in predation costs that appeared to be governed primarily by proximity to burrows and open sight lines. By converting the GUDs into quitting harvest rates (joules per minute), we believe we have translated the animals' perceptions of risk into a physical map whose contours across the landscape represent lines of equal foraging costs. Among the 3 colonies only 3-22% of the space resulted in low foraging costs (,2,500 J/min), whereas 31-92% of the sampled areas represented very high foraging costs (.5,000 J/min).

Scale‐dependent foraging costs: habitat use by rock hyraxes (Procavia capensis) determined using giving‐up densities

Individuals select for habitats at different scales. Can a species’ response to different spatial and temporal heterogeneities be placed in a common currency? Is it possible to rank the relative importance of different habitat features on the organism's behavior and ecology? Do the effects of different spatial and temporal heterogeneities interact in predictable ways? To address these questions, we quantified hyrax habitat use at a series of rocky outcrops (koppies) and an isolated gorge in Augrabies Falls National Park, South Africa. We measured the hyraxes’ perceptions of feeding opportunities and costs using giving‐up densities (GUDs) within experimental food patches. At very small spatial scales (2–3 m), we tested whether hyraxes have lower GUDs under cover (shrubs or rocks) or 2–3 m away in the open. Hyraxes valued cover highly, consistently showing lower GUDs in cover microhabitats. This preference did not result from differences in energetic costs, as hyraxes did not track sun in winter or shade in summer. At moderate spatial scales (10–80 m), we tested whether hyraxes act as central place foragers with lower GUDs closer to their dens. GUDs increased with increasing distance to dens at four koppies, but not at the gorge. At larger spatial scales, preferences differed between colonies based on differences in habitat structure, with hyraxes on similar structures (koppies) behaving similarly. We evaluated how foraging costs varied with temporal heterogeneity within the day, among days, and among seasons. Hyraxes showed their lowest GUDs in the early mornings and late afternoons. Hyraxes shifted foraging locations among days, which may result from sentinels shifting location on consecutive days and/or hyraxes managing their food. Differences between GUDs during the various sample periods were not seasonally correlated. We conclude that spatial and temporal habitat utilization by hyraxes may be driven more by predation risk rather than other costs.

Tasty figs and tasteless flies: plant chemical discrimination but no prey chemical discrimination in the cordylid lizard Platysaurus broadleyi

Lizards use visual and/or chemical cues to locate and identify food. The ability to discriminate prey chemical cues is affected by phylogeny, diet, and foraging mode. Augrabies flat lizards (Platysaurus broadleyi) are omnivorous members of the lizard clade Scleroglossa. Within Scleroglossa, all previously tested omnivores are capable of both prey and plant chemical discrimination. At Augrabies Falls National Park, P. broadleyi feed on both insects (black flies) and plant material (figs), and as scleroglossans, are predicted to discriminate both plant and prey chemicals. However, Platysaurus broadleyi use visual, not chemical cues, to detect and capture black flies, which occur in large concentrations in the study area. We tested free-ranging individuals for the ability to discriminate insect and plant chemicals from controls. There was a significant stimulus effect such that lizards tongue-flicked fig-labelled tiles significantly more than the remaining stimuli, spent more time at the fig-labelled tile, and attempted to eat fig-labelled tiles more often than tiles labelled with control or insect stimuli. Platysaurus broadleyi is exceptional in being the first lizard shown to possess plant chemical discrimination but to lack prey chemical discrimination. We suggest that an absence of prey chemical discrimination may be a consequence of foraging behaviour and environmental effects. Because insect prey are highly clumped, abundant, and aerial, profitable ambushing using visual cues may have relaxed any selective pressure favouring insect prey chemical discrimination. However, a more likely alternative is that responses to figs are gustatory, whereas as prey chemical discrimination and plant chemical discrimination are usually mediated by vomerolfaction.

The role of flowering plant species in the survival of blackflies (Diptera: Simuliidae) along the lower Orange River, South Africa

This study is an investigation of the role that plants play in the survival of adult blackflies by providing shelter and carbohydrate food. A detailed phenological study of the 29 most abundant plant species in the Augrabies Falls National Park showed that throughout the year the percentage of plant species flowering was remarkably constant. It is therefore unlikely that the availability of carbohydrates would limit adult Simulium survival at any time of the year. Blackflies were recorded feeding on the flowers of Pappea capensis. Acacia karroo, A. mellifera, Tamarix usneoides, Ziziphus mucronata, Scholia afra and Sisyndite spartea. An additional survey showed that another 64 plant species flowered throughout the year, and these can be regarded as potential carbohydrate sources. Blackflies were observed sheltering in dense shrubs and trees that provide protection against predation and harsh environmental conditions. This study suggests that vegetated drainage lines are the means by which adult blackflies survive dispersal away from the river. It is concluded that carbohydrate scarcity cannot be considered a limiting factor to adult blackfly survival along the lower Orange River.

Climate change in conservation areas of South Africa and its potential impact on floristic composition: a first assessment

SummaryProjected climate change has been suspected of affecting the biota of conserved nature areas in different and significant ways. Nevertheless, strategic management within some nature conservation agencies appears relatively unprepared for the possible consequences of climate change. National level planning of reserve design networks has also tended to skirt the issue, possibly owing to insufficient analysis. This paper provides a first assessment of the possible effects of climate change on plant diversity within the protected area network of South Africa. A climate change scenario of increased temperature but no change in precipitation resulted in derived optimum growth days increasing in some reserves through increased temperature extending the growing season. In some other reserves optimum growth days declined through greater evapotranspiration. We concentrated on the larger reserves of the latter group for which conditions that are more limiting were predicted. Plant species were evaluated in terms of their critical limits in growth days and minimum temperature. Over a third of the species analysed for one reserve (Augrabies Falls National Park and Melkbosrand) was indicated to become locally extinct with climate change. Another reserve in the region showed fewer than 1% local extinctions. It is clear that although a certain magnitude of climate change is a prerequisite for these extinctions, the rate and number of extinctions depend strongly on the different environmental tolerances of the specific biotic components of the conserved area. Potential immigration of other species to Augrabies Falls/Melkbosrand required to balance the projected extinctions with climate change would need migration abilities and conditions that are unlikely to be met. A net decrease in plant diversity may thus be expected. The results confirm that with the climate change scenario used, the concept of sustaining species through fixed protected areas may be fundamentally flawed, at least in certain areas.

Use of heterospecific cues by the lizard Platysaurus broadleyi for food location

Flat lizards (Platysaurus broadleyi) at Augrabies Falls National Park, South Africa, are restricted to rocky terrain where the predominant tree is the Namaqua fig (Ficus cordata cordata). P. broadleyi readily feeds on Namaqua figs when they are available, and the lizards sometimes form large (maximum recorded=134) congregations under fruiting fig trees. The distance lizards travel to fruiting trees also exceed normal daily foraging distances. Location of fruiting fig trees by a lizard can have a high pay-off because figs are energetically rich and trees fruit irregularly and asynchronously, resulting in a resource that is available, but unpredictable in time and space. The prediction that bird activity in fig trees provides a cue to the presence of ripe figs was tested experimentally. By placing cages containing birds and empty control cages in trees devoid of fruit, we demonstrated that P. broadleyi are drawn to fig trees with high bird congregations. We also tested if the presence of a fig tree was necessary to draw lizards to bird congregations by placing cages containing birds and empty control cages in a matched-pairs design on rock away from trees. Namaqua fig trees were not necessary to draw lizards to bird congregations.

Habitat and patch use by hyraxes: there’s no place like home?

Models of central place foraging predict that animals should forage more thoroughly in resource patches located closer to the central place. Travel time, cost of transporting food back to the central place, and exposure to predators should all act to increase foraging costs with increasing distance from the refuge. We examined habitat and patch use in rock hyraxes (Procavia capensis) inhabiting a group of kopjes in a semiarid savanna, Augrabies Falls National Park, South Africa. We tested the prediction of more intense patch use closer to the central place by measuring giving‐up densities (GUDs) in experimental resource patches set at four different distances from the kopje and in two microhabitats differing in cover. Surprisingly, hyraxes had their lowest GUDs at intermediate distances from the kopje. These unexpected results suggest that the sentinel behaviour of hyraxes alters the probability of detection of predators for animals foraging away from the kopje.

Flowering plant biodiversity of Augrabies Falls National Park: a comparison between Augrabies Falls National Park, Kalahari Gemsbok National Park, Vaalbos National Park and Goegap Nature Reserve

A list of flowering plants has been compiled for the Augrabies Falls National Park, which occupies an area of approximately 18 600 ha. This list of 364 species represents 210 genera and 74 families. The Monocotyledonae are represented by 76 species (20.9 of the total number of species) and the Dicotyledonae by 288 (79.1 ). Approximately 54 of these species occur only in the Augrabies Falls National Park and not in one of the other conservation areas with which it was compared. According to the life form spectrum, the Augrabies Falls National Park is a therophyte-hemicryp- tophyte area. Five of these spesies are endemic to the Southern African floristic region. One of them is a rare species.

Popups on Moon Rock, Augrabies Falls National Park

Naturally occuring popups (or A-tents) occur mainly on outcrops of horizontally compressed, sheeted granite. They consist of two slabs of surface rock pushed up to form a tent-like structure, or a surface sheet pushed up into an arc. Although popups have been studied in several countries, none have so far been described in South Africa. A survey of Moon Rock, a granite dome in the Augrabies Falls National Park, led to the discovery of 14 of these structures, including both angular and arched forms. The dimensions and orientations of the high, angular forms support the hypothesis that they constitute a stress release phenomenon, but the characteristics of the low, thin plated forms suggest that these are erosional features. The structures are eventually destroyed by the movements, as yet largely unexplained, of surrounding rock slabs, and by the gradual abrasion of the edges of the popped up slabs as a result of slight movements caused by daily heating and cooling of the surface sheet.

The major vegetation communities of the Augrabies Falls National Park, Northern Cape. 1. The southern section

Classification, description and mapping of the vegetation of the Augrabies Falls National Park, Northern Cape, were initiated. The classification is intended to serve as a basis for the establishment of an efficient wildlife management programme as well as conservation policies for the Augrabies Falls National Park. Using the BBPC suite, according to Braun-Blanquet procedures to classify the vegetation of the southern section of the Augrabies Falls National Park, six major plant communities are recognised. A hierarchical plant community classification, description, ecological interpretation and a vegetation map are presented.

Space partitioning between two small mammals in a rocky desert

An analysis was made in Augrabies Falls National Park, South Africa of the factors that allow coexistence of two small herbivorous mammals: the rock hyrax Procavia capensis and the dassie rat Petromus typicus. The rocky habitat provides adequate food and living shelters of varying sizes. There appears to be competition for shelters: Petromus occupies only those shelters that are too small for Procavia with the result that the population of Petromus is small and restricted to certain favourable areas whereas Procavia is abundant and widespread.

The diet of<i> Petromus Typicus</i> (Petromuridae, Rodentia) in the Augrabies falls National Park

The diet of Petromus typicus from three sites in Augrabies Falls National Park was analysed. Grass is the main item of the diet but the proportion of grasses to dicotyledons is determined to some extent by availability.

The freshwater fishes of the middle and lower Orange river

The occurrence and distribution of freshwater fishes of the middle and lower Orange River in the Republic of South Africa is presented, based on a survey conducted in September 1980. Particular attention is paid to the Augrabies Falls region including the Augrabies Falls National Park. Comments on the distribution and conservation status of the fishes are given.

Notes on the mammal fauna of the Augrabies falls National Park AND surrounding areas, with special reference to regional zoogeographical implications

An annotated checklist of the mammals recorded by direct or indirect means on or near the Augrabies Falls National Park, is provided. Speculations are offered as to which species have become locally extinct during historical times. The , Orange River as a faunal dispersal corridor and barrier, is considered. A numerical analysis to determine whether the Augra- 
 bies Falls district falls within the Namib or the South West Arid biotic zone, is discussed.

<i>Phrynomerus Annectens</i> (Werner), a rare frog in the Augrabies Falls National Park

During a visit (1977.01.28) to the Augrabies Falls National Park, Republic of South Africa, a heavy shower of rain brought relief to prevailing hot, dry conditions. A specimen of the rare South West African Red banded Frog Phrynomerus annectens (Werner) was collected that evening, on the lawn of the administration block.

A phytosociological and phytogeographical study of Augrabies Falls National Park, Republic of South Africa

An outline of the physiography and climate of the Augrabies Falls National Park is given. The plant communities occurring in the Park are described and their ecology is briefly discussed. A brief discussion on the phyto-geography of the area, and on the flora and growth forms is added.

A new Platysaurus (Squamata: Cordylidae) from the Northern Cape Province, South Africa

BRANCH, W.R., and M.J WHITING. 1997. A new Platysaurus (Squamata: Cordylidae) from the Northern Cape Province, South Africa. Afr. J. Herpetol. 46(2): 124–136. A new species of Platysaurus is described from the Gordonia-Kenhardt district of Northern Cape Province, South Africa. Numerous features of scalation and colouration distinguish it from all other southern African Platysaurus. The new species is morphologically most similar to, and was previously confused with, P. capensis from northern Namaqualand, the Richtersveld and southern Namibia. There is no evidence for genetic exchange between the new species and P. capensis, which are separated by 100 km. Therefore, based on allopatry, the presence of two autapomorphies (dorsal forelimb scales subequal to those on hindlimb and unique male colouration), and significant differences in eight other scalation features, the Augrabies population meets the criteria for designation as a new species within an evolutionary species concept. These lizards occur in very high densities in the Augrabies Falls National Park where black flies (Simulium spp.) form a major food resource.