A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, for the degree of Master of Science. Johannesburg 1993. / The prediction that savanna communities with similar conditions of plant available moisture (PAM) and available nutrients (AN) have similar structural and functional features was tested for a range of southern African savanna types. This prediction forms the basis of an hypothesis that savannas can be classified functionally on the basis of PAM and AN. Nineteen South African savanna types were sampled over a rainfall gradient of 369 to 690 rnm pa and on different geological parent materials. Ecologically meaningful indices of PAM and AN were derived using climate and soil physical and chemical data. The floristic structural and functional characteristics of the woody plant and herbaceous components of the savanna communities were ordinated and classified in relation to the PAM and AN gradients. The functional classifications were assessed in the plane of PAM and AN. Plant available moisture was indexed as the mean number of growth days per annum derived form a water balance modelling approach. This index reflected the duration of the growing season in days and was suitably detailed for use at the community level. The AN indices ranged in complexity from a measure of the availability of individual nutrients in the soil to an index based on the results of a bioassay experiment. The usefulness of the AN indices was assessed on a number of criteria and the soil A horizon total nitrogen content in mg/kg was chosen as a suitable AN index. The species composition of the woody plant and graminoid communities was primarily related to the PAM gradient with AN having a significant but secondary effect. There was overall a high degree of similarity between woody plant and graminoid floristic types. The distribution of members of the woody plant families, Mimosoideae, Caesalpinoideae and Combretaceae were primarily related to the AN gradient. The higher taxonomic classifications of the graminoid communities, based on subfamilies and tribes, were primarily related to PAM. Structural trends of the woody plant and herbaceous communities were related to the PAM gradient but not to soil fertility. There were a range of structural types for similar conditions of PAM and AN. The functional trends of the woody plants were primarily related to the AN gradient with PAM having a secondary but significant effect while the graminoid community functional trends were primarily related to PAM with AN having a secondary but significant effect. The woody plant and graminoid communities were notgrouped into functional types in the same way. It was evident from this study that these South African savanna types were related floristically, structurally and functionally to either or both of PAM and AN, which are hypothesised to be the primary determinants of savanna structure and function. Although communities with similar conditions of PAM and AN were not consistently functionally similar, the functional classifications of both the woody plant ami graminoid communities mapped well onto the PAM-AN plane. This indicated that the PAM-AN plane does have potential foruse as an overall framework for the classification of savannas on a functional. basis. / AC2017

No abstract available. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1983.

The Drakensberg rock-jumper (Chaetops aurantius) is a high-altitude passerine endemic to South Africa and Lesotho, living along a highly disrupted portion of the southern Great Escarpment from the Drakensberg highlands in the north-east to the Sneeuberg in the west, above an altitude of 1500 m. Along with the Cape rock-jumper (C. frenatus), this genus provides one of the stronger faunal links between the floristic biomes known as the Drakensberg Alpine Centre (DAC) and the Cape Floristic Region (CFR). Despite this, there is a significant lack of information regarding the species. The great majority of information is based on incidental observation, and no dedicated study has been undertaken. I conducted a series of field excursions between January 2011 and November 2012 in order to explore the rock-jumper’s feeding ecology, diet, habitat usage and genetic diversity. By trapping the birds, I was able to mark them individually with unique colour ring-combinations, and pluck a tail feather for genetic analyses. Observational data reveal that birds living close to their lower altitude threshold (c. 1500 m) are strongly habitat specific, living in boulder fields dominated by grassy vegetation. However, in areas at higher elevations (c. 2000 – 2500 m) this restriction seemed to fall away, possibly as a result of farming practices in those areas – higher grazing pressure results in shorter grass and less foraging effort for the birds. They live in groups ranging from pairs to small family groups of up to twelve individuals and maintain year round territories. Territory defence takes the form of calling and displaying from a prominent rock or boulder and becomes particularly noticeable just prior to, and during, the breeding period. No colour ringed individuals were ever spotted in boulder fields outside from where they had been initially ringed. This, coupled with the behaviour of territory maintenance, suggests a strongly sedentary lifestyle. Genetic inferences are constrained by a small sample size (only 25 birds were caught), but results indicate that some genetic isolation is occurring – a single haplotype was exhibited in birds from across the southern Escarpment, while seven private haplotypes show that any genetic mixing is likely to be historical rather than current. Historical gene flow would most probably have occurred during the last glacial maximum (18 000 years before present), when the cooler, drier conditions which are currently restricted to high peaks would have been much more extensive, thereby decreasing the distance required for effective dispersal. This is in agreement with the observation results, concluding that although there has been movement of birds across the southern Escarpment in the past, it does not appear to be occurring currently. However, this does leave plenty of scope for further work, particularly in the genetic diversity of the species, and in expanding the ecological observations to include the breeding biology.

The lack of fundamental biological information on the honey badger Mellivora capensis and its vulnerable conservation status were the motivating factors behind this study. A study population of 25 individuals (12 females; 12 males) was radio-marked in the Kgalagadi Transfrontier Park (KTP), South Africa. Through a combination of radio telemetry and visual observations (5 244 h) of nine habituated individuals (five females; four males), the feeding ecology, scent marking and social behaviour of the honey badger were investigated. The honey badger is a solitary, generalist carnivore with strong seasonal differences in diet. In support of optimal diet theory, the cold dry season diet is characterized by low species richness, low foraging yield, high dietary diversity and increased foraging time while the reverse is true in the hot wet and hot-dry seasons. The honey badger appears to shift between alternative prey species depending on their availability on a seasonal and daily level. The daily activity patterns of both sexes show a strong seasonal shift from predominantly nocturnal activity in the hot-wet and hot-dry season to more diurnal activity in the cold-dry season and this appears to be primarily affected by temperature. Despite marked sexual size dimorphism (males a third larger than females), no intersexual differences in diet or foraging behaviour were observed, but there were sexual and in males age-related differences in movement patterns, scent marking and social behaviour. The honey badger appears to have a polygynous or promiscuous mating system, but did not fit the general mustelid pattern of intrasexual territoriality. Instead, adult males had extensive overlapping home ranges (548 km2) that encompassed the smaller, regularly spaced home ranges of the females (138 km2) and young males (178 km2). Receptive females are an unpredictable and scare resource in space (large home ranges) and time (no breeding season) with a long time to renewal (inter-birth interval > 1 year). As a result adult males adopt a roaming rather than a staying tactic with competition for access to the mating burrow mediated by a dominance hierarchy loosely based on age, mass and testes size. The hierarchy appears to be maintained through regular aggressive and agonistic interactions and scent marking. Data suggest that latrine scent marking in adult males is related to advertising social status and maintaining the dominance hierarchy though “scent matching”. In females and young males latrine visits are rare, but token urination is common and its association with foraging behaviour suggests that it mediates spatio-temporal separation and/or resource utilization. Interspecific interactions between the honey badger and other mammalian and avian predators were common and included intraguild predation and interspecific feeding associations between the honey badger and seven other species (two mammals; five birds). The most common foraging associations were observed between the honey badger and the pale chanting-goshawk Melierax canorus and black-backed jackal Canis mesomelas. These associations appear to be commensalisms, with associating species benefiting from increased hunting opportunities and intake rate but no significant costs or benefits to the honey badger. Copyright 2001, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Begg, CM 2001, Feeding ecology and social organisation of honey badgers (Mellivora capensis) in the southern Kalahari, DPhil thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-11282005-145818 / > / Thesis (DPhil (Zoology))--University of Pretoria, 2001. / Zoology and Entomology / unrestricted

Two methods for predicting regions susceptible to invasion by alien aquatic animals were developed for southern Africa (excluding Zimbabwe and Mozambique). In the "traditional" (data-poor) approach, distributions of three categories of alien "indicator" species (warm mesothermal, cold stenothermal and eurytopic) were compared to seven existing biogeographical models of distribution patterns of various animals in southern Africa. On the basis of these comparisons a synthesis model was developed which divided southern Africa into seven regions characterised by their susceptibility to invasion by alien aquatic animals with particular habitat requirements. In the "data-rich," geographic information systems (GIS) approach, the distribution of trout (Oncorhynchus mykiss and Salmo trutta) in selected "sampled regions" was related to elevation (as a surrogate of water temperature) and median annual rainfall (MAR) (as a surrogate of water availability). Using concentration analysis, optimum conditions for trout were identified. Regions within a larger "predictive area" which satisfied these conditions, were plotted as a digital map using the IDRISI package. Using this method seven models of potential trout distribution were generated for the following regions: northern Natal (two); southern Natal/Lesotho/Transkei (three), eastern Cape (two) and western Cape (two). Since two of the models were used to refine the methods, only five models were considered for the final assessment. In a modification of the GIS method, another model of potential trout distribution, based on mean monthly July minimum air temperature and MAR parameters, was developed for the region bounded by 29º - 34º S and 26 º - 32°E. This model showed marked similarities to another model, developed for the region bounded by 29 º - 32°S and 26º - 32°E, which was based on elevation and MAR parameters. The validity of the models developed was assessed by independent experts. Of the six models considered, four received favourable judgements, one was equivocal and one was judged to be poor. Based on these assessments it was concluded that the GIS method has credibility and could be used to develop a "data-rich" model of the susceptibility of southern Africa to invasion by alien aquatic animals. This method represents an alternative to the bioclimatic matching approach developed by scientists in Australia. The GIS method has a number of advantages over the "traditional" method: it is more amenable to testing, has greater flexibility, stores more information, produces images of a finer resolution, and can be easily updated. The traditional method has the advantage of being less expensive and requiring a less extensive database.

As the dry season progresses across southern Africa, the availability and quality of food declines for large herbivores. Female white rhinos compensate for these declines by expanding and/or shifting their home ranges. These changes may be to incorporate habitat types that contain high quality food or quite simply more food. To determine the factors that drive these seasonal changes in home ranges, I focused on dry season changes in the availability and quality of grass in habitats utilised by white rhinos in the Ithala Game Reserve, South Africa. I expected that if food quality was the main driver, white rhinos would follow optimal foraging principles and incorporate habitat types with the highest nutritional quality into their dry season home ranges. Alternatively, due to their large body size (>1000 kg) and thus ability to survive on low quality food, they may rather incorporate habitat types with high food availability. In contrast to previous studies, I found that during the dry season female white rhinos did not increase the size of their home ranges, but rather shifted their home range boundaries. This resulted in individuals increasing the amount of Bushveld and decreasing the amount of Wooded Grasslands within their dry season home ranges. When I explored the different factors that could explain these patterns, I found that changes in the crude protein content of grass was the key factor driving the incorporation and exclusion of habitat types in the home ranges. During the dry season, white rhinos incorporated the habitat that had the smallest seasonal reduction in crude protein content, while excluding the one with the largest decrease in crude protein. As a result, my results suggest that the search for high quality best explains the seasonal home range shifts of female white rhinos in the Ithala Game Reserve. / Thesis (M.Sc.Ecology)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

The long-term economic viability and ecological integrity of savanna rangelands is being undermined by increasingly dense woody thickets at the expense of palatable herbaceous cover. This process is known as shrub- or bush-encroachment. Bush encroachment is a subset of a broader ecological riddle underlying the coexistence of woody and herbaceous vegetation that has been the subject of many ecological models. The ecophysiological mechanisms and interactions between trees and grasses on which most assumptions of ecological models are premised have seldom been tested empirically. This document synthesises the results of greenhouse and field-based investigations of the underlying ecological mechanisms and ecophysiological interactions between encroaching Acacia mellifera trees and grasses in a semi-arid environment. In a greenhouse study, I determined the contribution of N2 fixation to the N-budget of Acacia mellifera under conditions of both varying N availability and competition from grass. Tree seedlings had longer shoots and greater total dry mass in the absence of grass. The leaf δ15N values were lower with grass than without grasses. Thus, trees were more reliant on N2 fixation in the presence of grasses. N2 fixation may enable the tree seedlings to survive competition with grass at critical and vulnerable developmental stages of germination and establishment. In a field removal experiment, I monitored the growth rates, water relations and mortalities of shrubs around which neighbouring woody plants were removed (target) and control shrubs over three years. Results showed target trees to have benefitted from removal of neighbours, which was manifested in significantly faster growth rates, less negative predawn water potential and a relatively small degree of canopy die-back. Nonetheless, neighbouring trees appeared to prevent the whole plant mortalities resulting from severe environmental stress. Growing in close proximity with neighbours could therefore yield positive and negative ecophysiological effects. In another greenhouse experiment, I tested the effects of the separation of moisture uptake with depth between tree seedlings and grasses on two common substrate types. I also examined the influence of repeated grass clipping on the persistence of soil moisture. Results indicated a three-tier rooting pattern with a top layer exclusively exploited by grasses, an intermediate layer occupied by both grass and tree roots and deeper layers exclusively tapped by trees. Tree seedling biomass was negatively affected by grass competition although the biomass of grass was enhanced in the presence of tree seedlings on sandy substrates only. The repeated clipping of grass benefitted tree seedlings on rocky substrate more than it did on sandy substrate. The effects of heavy grazing on soil moisture availability to woody shrubs and thus bush encroachment may be contingent on substrate type, being more acute on rocky terrains. Grass competition suppresses tree seedlings but the removal of grass by grazing weakens this suppressive effect, particularly on rocky substrates. The insufficiency of space and soil resources on rocky substrates may necessitate increased investment in root biomass by plants. It is not known why grasses have lower densities on rocky substrates than on sandy substrates, but the obstruction by rocks disadvantages grasses against tree seedlings, leaving grasses vulnerable to grazing pressure. This may allow the woody plants on rocky substrates to benefit more from grass removal than on sandy substrates. Root restriction by rock barriers and, perhaps, sparse soil volume further lead to small tree sizes on the rocky substrate. Small shrubs are less likely to compete intensively for resources and cause density-dependent mortality. Intraspecific competition may maintain shrub sizes within the threshold that can be supported by available resource pools. I conclude from my results that the two-layer hypothesis of niche separation between savanna vegetation is valid although there is an overlap in the grass and tree rooting depth/moisture uptake. An additional factor that affects the success of A. mellifera is the substrate.Trees are more dense on rocky substrates but grow larger on sand. I have further shown that A. mellifera trees fix nitrogen when competing with grasses but do not do so when grasses are absent. A mechanistic model of savanna dynamics will need to integrate water use patterns, substrate and nutrients to make effective predictions about encroachment patterns. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

This study assessed the importance of overwash and breaching events on the ichthyofaunal community structure in the medium-sized temporarily open/closed Mpekweni Estuary located on the southeast coastline of southern Africa. The fish in the littoral zone of the estuary were sampled using a 5m seine net while the channel region was sampled using two nets, a smaller meshed 30m seine net to target the estuarine spawning species and the juvenile estuarine-dependant marine spawners, and a larger meshed 50m seine net to target the larger marine and freshwater spawning species. Intensive monthly sampling over two years provided data on selected physico-chemical and biological parameters. During the two year sampling period from November 2005 to October 2007 the estuary breached in late July 2006 and remained open till the sandbar re-formed across the mouth in late December 2006. Thus, sampling encompassed three open/closed phases 1) initial closed period, 2) open period and 3) re-closed period after the berm was re-formed. The open period was divided into two phases 1) the out-flow phase and 2) the tidal phase. A total of 36 fish species representing 19 families were sampled using the various seine nets employed during the investigation. In the littoral zone, the estuarine spawners (Estuarine Utilisation Category, [EUC] I), mainly the Gobiidae, Glossogobius callidus, dominated the samples numerically and by biomass. The smaller estuarine spawning species sampled in the channel were numerically dominated by Gilchristella aestuaria in conjunction with two other EUC I species, Atherina breviceps and G. callidus. The estuarine-dependant marine spawners (EUC II), however, dominated the ichthyofaunal biomass of the channel. The abundance and biomass of the larger species targeted were dominated by estuarine-dependant marine spawning species (EUC II), principally Rhabdosargus holubi. During the closed periods of the estuary, total fish abundance and biomass displayed weak seasonal patterns. The breaching event and subsequent open period was associated with a decrease in the total abundances of fish in the littoral zone and channel of the estuary, reflecting the out-flow of estuarine biomass-rich water into the marine environment. The breaching event coincided with a shift in the community composition of the ichthyofauna, reflecting the recruitment of marine spawning species into the estuary. Numerical analysis identified two distinct spatial fish communities within the estuary, a community associated with the mouth region and one comprising the rest of the estuary. The absence of any further spatial patterns in the ichthyofaunal community structure within the Mpekweni Estuary appear to be ascribed to the virtual absence of horizontal patterns in physico-chemical and biological parameters recorded in the system. Cohort analyses were employed to determine possible recruitment events for selected estuarine and marine spawning species. The estuarine spawning species displayed continuous recruitment patterns throughout the study, which appeared to be unaffected by the breaching event. Conversely, the larger marine spawning species displayed multiple cohorts, indicating non-continuous recruitment. Subsequent retrospective analysis of cohorts for the different species identified summer recruitment peaks that coincided with the breaching event and open period. Minor recruitment of marine spawning species also occurred during overwash events. The recruitment of ichthyofauna into the estuary was quantified during three distinct hydrological events: overwash, out-flow phase immediately after breaching and tidal phase during the period when the mouth was open. Estimates of fish recruitment were highest during the outflow phase immediately after the estuary breached and declined as the estuary became tidally inundated with marine water. Although not as high as the outflow and tidal phases, recruitment was evident during overwash events. Results of the current study highlight the importance of both breaching and overwashing events in structuring the ichthyofaunal community composition in a medium-sized southern African temporarily open/closed estuary. These results are broadly in agreement with similar studies conducted both locally and in other regions of the world.