School of Animal, Plant and Environmental Sciences (ETDs)

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A comparative analysis of mining environmental management programme reports following a change to the one environmental system
(University of the Witwatersrand, Johannesburg, 2022) Mathe, Lebogang; Watson, I.
The mining fraternity has recently seen a shift in terms of environmental requirements under the ambit of the Mineral and Petroleum Resources Development Act 28 of 2002 (MPRDA) to the National Environmental Management Act 107 of 1998 (NEMA). The objective was to ensure a streamlined environmental compliance and to put emphasis on integrated environmental management. The One Environmental System (OES) was introduced which denotes that all environmental related projects or activities, including mining, are regulated through an ambit of one system. NEMA is recognised as an overarching law which provides for co-operative environmental governance; therefore, all environmental related activities are regulated under its ambit and EIA regulations. In this research report, the Environmental Management Programme (EMP) reports and Environmental Authorisations that were issued under the MPRDA and the 2014 NEMA regulations respectively, were analysed using the respective regulations to compare the environmental management measures outlined in the reports to achieve better environmental results. The aim of the research was to assess whether the Environmental Authorisations granted in terms of NEMA reflect better environmental results as compared to those issued under the MPRDA. Better environmental results mean improved management plans with clearer assessment of impacts, more detailed mitigation measures with specific, achievable, relevant and time bound actions that do not pose harmful effects on the environment and communities. A mixed method of analysis was implemented which included a review and comparison of legislation, evaluation and scoring of 20 EMPs (10 submitted under MPRDA and 10 submitted under NEMA) and interviews with key informants, namely competent authorities and the Environmental Assessment Practitioners (EAPs) were conducted to support the findings of the reports. In conclusion, the reports analysed presented a significant improvement and better environmental results under NEMA. The interviews conducted with authorities and the EAPs have also substantiated the observations made in terms of Environmental Management Programme reports and Environmental Authorisations submitted. The findings indicated that there were similarities in the MPRDA and NEMA regulations as 4 | P a g e regards some environmental requirements. However, the MPRDA lacked to outline a detailed description of environmental requirements needed to manage environmental impacts. Thus, applicants provided limited information in terms of the management of impacts. NEMA has provided additional requirements, including baseline environmental information, specialist reports and public participation amongst others; these contributed to improved environmental results. The study revealed that the reports submitted under NEMA provided better environmental management measures as compared to the reports submitted under MPRDA.
Biodiversity stewardship in south africa - an assessment of the klipkraal biodiversity stewardship programme and its potential for conservation
(University of the Witwatersrand, Johannesburg, 2024) Butler, Kirsten
The importance of conservation in agriculture has become more apparent over the last couple of years, however it involves complex social-ecological relationships and as agriculture is a critical industry for human survival, biodiversity conservation in the industry is a major challenge worldwide. In South Africa, biodiversity stewardship programmes, which involve agreements between landowners and conservation authorities to secure land in biodiversity priority areas, are becoming a prominent method of conservation in agriculture. Yet there is a lack of research on the conservation benefits and whether they show improvements in the area’s biodiversity. This study focussed on the Klipkraal biodiversity stewardship programme which consists of two privately owned functional cattle farms in a peri-urban area of the southern grasslands of Gauteng making up 2 656 hectares of land of which 1 600 hectares are natural vegetation, and the remaining area is cultivated land used for farming maize and soya. The study sought to answer the question: what is the ecological state of the area and does this programme have potential for conservation in the long-term? The aim of this study was to assess the potential conservation benefits and sustainability of the Klipkraal biodiversity stewardship programme. The study involved both qualitative and quantitative data collection, including landcover mapping, field surveying to assess the vegetation state and mammal diversity and distribution of the site, and interviews with key stakeholders. The landcover mapping allowed for a visual representation of the various landcover types and percentage coverage of each of the six landcover types found in the study area. Vegetation assessments at five different sites resulted in an understanding of the vegetation structure, composition and cover across the two farms and from this it was established that the vegetation structure and species diversity differ, but the species composition is similar throughout the study site. An anthropogenic disturbance score was allocated to each site and the highest rated anthropogenic scores correlated with the sites consisting of the highest exotic species. The mammal assessments showed that the varying vegetation structure allows for specialist species to occupy a range of habitats within the site and also indicated that there are barriers to the movement of large mammals within the site. The results of the vegetation and mammal assessment which suggest a diverse range of vegetation units, habitats, and mammal diversity, emphasise that the area is important for conservation. The interviews revealed the multiple challenges involved in the Klipkraal Biodiversity Stewardship Programme and requirements in order for the programme to be successful in the long term. These include a need for willingness of landowners to put their time and resources into conservation efforts on their properties, a need for constant monitoring of management strategies, the importance of expanding the stewardship areas to ensure conservation of the entire area and not just isolated fragments of the area. However, key challenges in expanding the programme were also revealed, such as scepticism by landowners in entering land agreements with the government and in Gauteng, many areas of conservation interest are made of multiple small properties that are owned by different landowners which means a lot of effort is required in getting each landowner to sign up. Insight was also given into the roles of the various stakeholders and the relationship between the Gauteng Department of Agriculture and Rural Development (GDARD) and the landowners, and it was indicated that GDARD’s role is to provide guidance, education and resources when available to the landowners in order to manage their protected area. This study can be used as a baseline study for GDARD to measure the progress in conservation in terms of the landcover and ecological aspects at the site and to monitor any changes in landowner-GDARD dynamics.
Characterisation of Drought Using Hydrological and Meteorological Indices: A Case Study of Bethlehem, South Africa
(University of the Witwatersrand, Johannesburg, 2023) Tshabalala, Khanyisile; Evans, Mary; Masindi, Khuliso
The study aims to assess the severity and evolution of drought/s in Bethlehem using the hydrological: Streamflow Drought Index (SDI), Reconnaissance Drought Index (RDI), Effective Reconnaissance Drought Index (eRDI) and meteorological: Standardised Precipitation Index (SPI), Agricultural Standardised Precipitation Index (aSPI), and Precipitation Deciles (PD) indices. These indices were computed using the Drought Indices Calculator (DrinC). The RDI, eRDI, aSPI, and SPI identified three drought events between 1980 and 2017. The PD on the other hand, identified particular years between 1980 and 2017 that received below-normal to much below- normal precipitation. Further, the years identified to have received below normal to much below normal precipitation fell between the drought periods identified by the other indices, such as the 1980 – 1990 drought identified by the SPI, RDI, aSPI, and eRDI; the PD identified 1982, 198, 1985, and 1986 as specific years the received significantly low precipitation within the decade long drought. Of critical note is the absence of the SDI results, stream levels data was not available at the time the results presented in this report were computed. The unavailability of SDI values did not compromise or negatively affect the results presented in this study as the computed indices had a strong correlation, implying the reliability of the results presented in this report
Cognition in urban-dwelling yellow mongoose, Cynictis penicillata
(University of the Witwatersrand, Johannesburg, 2024) Muller, Mijke; Pillay, Neville
Cognition involves perceiving and processing environmental cues and devising appropriate behavioural responses to act on the acquired information. Studying animal cognition in an urban setting provides insight into the occurrence of behavioural changes in urban-adapted animals. This thesis aimed to investigate the cognitive abilities of a population of yellow mongoose, Cynictis penicillata, inhabiting locations with differing extents of urbanisation in South Africa. First, I investigated whether mongooses could learn to solve a puzzle box problem of increasing complexity. The mongooses were able to solve the problem at each stage of complexity, but took longer in a residential ecological estate than those frequently visiting a residential garden. These results indicated that mongooses were capable of innovation, but their problem-solving abilities were influenced by the level of disturbance in their environment. Secondly, I investigated whether mongooses exhibited cognitive flexibility. The mongooses were able to inhibit a non-rewarding behaviour, even when it was previously rewarded, in favour of a newly rewarded behaviour during the puzzle box task. Additionally, they could solve the puzzle box problem during distraction, but took longer with the most distraction, likely splitting their attention between solving the problem and remaining vigilant. Combined, the mongooses were capable of reversal learning and divided/alternating attention, providing evidence of cognitive flexibility in this mongoose population. Thirdly, I investigated the effects of a direct human approach on the problemsolving ability of mongooses. In areas of heightened human disturbances, the mongooses had reduced tolerance to humans, but were equally efficient at solving the puzzle box problem following human disturbance than those in areas of reduced human disturbance. Those more tolerant of humans improved their problem-solving efficiency, likely adapting to the disturbance. Finally, I investigated whether mongooses experienced a paradox of choice (i.e. whether too much choice can be cognitively challenging). The mongooses in my study appeared to experience cognitive difficulties when presented with extensive choice, providing support for a paradox of choice. These results provide evidence that urban-living yellow mongooses’ successful adaptation to an urban habitat may be attributed to their cognitive abilities, allowing them to exploit novel resources and flexibly adapt to the rapid environmental changes associated with urbanisation. However, the disturbance associated with urbanisation may negatively affect problem-solving efficiency, which may impact successful food acquisition, and the increased availability of resources may be cognitively challenging for urban-living yellow mongooses.
Factors limiting karoo shrub populations in the Nama-Karoo
(University of the Witwatersrand, Johannesburg, 2023-09) Hebbelmann, Lisa; O’Connor, Tim; Witkowski, Ed
The Nama-Karoo Biome occupies the central and western region of South Africa. Nama-Karoo shrublands are dominated by karoo dwarf shrubs and in the wetter eastern regions annual and perennial grasses are interspersed among shrubs. Rainfall and grazing are the main drivers of vegetation change in the Nama-Karoo. Stocking rate, season of grazing and animal type are important influences on vegetation community composition, and rainfall determines shrub growth and the abundance of grass. More recently, fire has been identified as a driver of vegetation change. Understanding vegetation change is important for land managers in the Nama-Karoo as changes in karoo shrub communities have implications for forage availability. This thesis is focused on understanding how grazing, fire, grass-shrub competition, and soil moisture and temperature affect the composition, structure, growth and phenology of karoo shrubs in the Eastern Upper Karoo. Livestock type and stocking rate vary greatly over the greater Nama-Karoo area. Plant composition data from the Afrikaner-Hereford grazing trial at Grootfontein show that grazing has a strong legacy effect on Karoo rangelands and grazing-induced compositional and structural changes are clear many years after grazing has ceased. Different sheep breeds affect karoo shrub communities in different ways. There was a severe negative effect of heavy stocking with dorper sheep on karoo shrub communities and their structure; the impacts of merino sheep were significant but less severe. Effects of animal type and stocking rate were not consistent across the sites but appear to be dependent on edaphic factors. Soil physical properties appear to play an important part in determining the long term effects of grazing on karoo shrub communities. Fire is a novel disturbance in the Karoo. Nine sites which had experienced fire for the first time in history were studied for the effect of fire on the composition and structure of their shrub communities. The immediate effect of fire on karoo shrub communities was severe and the legacy effect of fire was significant. The nature of recovery after a fire depended on the abundance of fire-intolerant obligate reseeder shrubs that are killed by fire compared to the abundance of fire-tolerant resprouting shrubs. Rainfall and grazing management were important determinants of shrub recovery after a fire. As rainfall increases, grass biomass is predicted to increase, and this may result in fire becoming a more frequent occurrence in the Nama-Karoo. During periods of high rainfall, the biomass of grass in the Nama-Karoo increased at the expense of shrub cover. The effect of grass-shrub competition on shrub growth and phenology is not adequately explained by existing hypotheses of niche separation and succession. A field experiment which examined the growth and phenology of karoo shrubs in the presence of grass (unclipped control) and the absence of grass (grass removed by clipping) did not provide evidence of a competitive effect from grass on shrub growth or phenology. It did, however, provide valuable insight into how shrub growth and phenology are influenced by soil moisture and temperature. Rainfall in the Nama-Karoo is sporadic and a karoo shrub’s ability to utilise soil moisture will determine its ability to grow and successfully recruit. Shrub growth, with or without grasses in the vicinity, was strongly correlated with rainfall, but this was modified by temperature. Similarly, soil moisture and temperature were important for stem growth and phenology. Flowering occurred in response to soil moisture all year round but seeding occurred mainly during summer. Patterns of growth and phenology can be used by land managers to optimise shrub production while allowing phenological processes to take place. The findings of this study provide further insight into how grazing, fire, competition, soil moisture and temperature influence shrub populations and their structure, and these are discussed in the context of an existing state-and-transition model for the Eastern Upper Karoo. The importance of animal type and stocking rate, and how they vary across Nama-Karoo landscapes, is highlighted. The legacy of both grazing and fire reveal that the transitions between the alternate states of Nama-Karoo shrublands are not easily reversed in a management timeframe. It may take decades for a community changed by grazing or fire, acting independently or in conjunction, to return to their former state even under benign management. These findings along with a description of how soil moisture and temperature influence shrub growth and phenology have been used to make ecologically sound recommendations for the management of Nama-Karoo rangelands. Future research is needed to improve our understanding of how edaphic factors limit and influence karoo shrub populations across a variety of karoo landscapes, how repeat fires might change karoo vegetation, and whether temperature and the presence of pollinators influences shrub seed set. An assessment of the economic implications of vegetation change in the Nama-karoo is warranted so that management recommendations can be made with both ecology and economy in mind.
Functional feeding groups of mayfly nymphs (Ephemeroptera) in South African rivers of the North West and Limpopo Provinces
(University of the Witwatersrand, Johannesburg, 2024-02) Bossman, Esi H.; Harrison, James du G.; Woodford, Darragh J.
Researchers, primarily in the Northern hemisphere, have extensively studied mouthpart morphology and dietary variability in Ephemeroptera (colloquially called mayflies). Ephemeroptera are key primary consumers in rivers around the world and are used as aquatic biomonitoring indicators due to interspecific variation in ecological tolerances that make them good indicator taxa. Cummins (1973, 1974) created a functional feeding groups (FFG) classification system, based on northern hemisphere macroinvertebrates, as a universal tool to functionally categorise organisms based on their primary feeding mode within their habitat. The FFG classification system is useful in identifying interrelations between structural and functional components of an ecosystem. The aim of this study was to contribute knowledge on FFGs for particular mayfly species, in the southern African savanna biome, through mouthpart morphology and gut content analysis. Four study sites were sampled from the Magaliesberg (M) and Waterberg (W) catchments. There were three species studied, namely Afroptilum parvum (Family Baetidae), Afronurus barnardi (Family Heptageniidae) and Elassoneuria sp. (Family Oligoneuriidae). These species’ mouthparts were dissected and their macro- and microstructures were prepared for viewing with Scanning Electron Microscopy (SEM) and light microscopy. Micrographs and images showed variation in mouthpart morphology between all three species, with special attention to the labia and maxilla microstructures. The identification and description of microstructures that differentiate mayfly species (and the adaptations of these appendages to facilitate food uptake and ingestion) are important to address knowledge gaps regarding mayfly mouthpart morphology. A Principal Component Analysis (PCA) showed distinct grouping of the three species, with mandibles and maxillary palps showing the most variation between species. After analysis, the following feeding groups were assigned: Afroptilum parvum is a collector-gatherer feeder, Afronurus barnardi is a brusher-scraper feeder and Elassoneuria sp. is a filter feeder. This study showed, in part, that the Cummins’ (1973, 1974) classification categories were too broad for classifying organisms from a South African savanna stream. However, it is a good foundational starting point for region specific FFG classification systems. Thus, it is recommended to use the classification system Cummins created as a starting point for classifying organisms into FFGs with an initial definition that can be expanded upon to create individual classification systems for different localities.
Home range establishment of translocated African elephants (Loxodonta africana) in a savanna environment
(University of the Witwatersrand, Johannesburg, 2023-09) Ngorima, Patmore; Parrini, Francesca; Boyers, Melinda; Mariotti, Elena
Data from nine female African elephants translocated to Hurungwe Safari Area that had been collared was used to estimate home range patterns. Monthly home ranges for each elephant were estimated using the 50% and 95% Kernel Density Estimates (KDEs) method for a period of 20 months following translocation. At the population level, a linear regression model was used to test for the effect of months from release on the home range patterns. The findings revealed that the 95% home range of the elephants increased over time, while the 50% home range decreased since their initial release. I went further to compare the individual differences using the generalised additive model. The results showed some individual differences in patterns of exploration, with some displaying more linear home range patterns than others. Over and above, a considerably positive and relevant relationship between time and variation in the extent of the home range was observed.
Personality profiles of the Namaqua rock mouse (Micaelamys namaquensis), the Mozambique thicket rat (Grammomys cometes) and the woodland dormouse (Graphiurus murinus)
(University of the Witwatersrand, Johannesburg, 2023-09) Mampa, Nthabiseng; Linhsan, Emmanuel Do; Madikiza, Kim
Personality is the variation in behaviour amongst individuals, which arises as a result of genetic differences and exposure to different environments. Although the term is usually associated with humans, multiple studies have found evidence for personality in other non-human taxa such as rodents, fish, reptiles, and primates, which ultimately showed that personality is ubiquitous. Personality determines how individuals react in different situations throughout their life, such as when they encounter stressors, interact with their conspecifics, prey and predators, how they select seeds and the distance to which they disperse, when displaying aggression, and when facing novel objects, their propensity to take risks, among other behaviours. Personality traits are most described using terms such as bold and shy, aggressive, docile, and avoidant. These terms relate to individual coping style, temperament, and correlated traits. Given the importance of personality, this study was aimed at studying personality in the woodland dormouse, Mozambique thicket rat and Namaqua rock mouse, in order to understand personality and how it varies among species and within species, i.e., between sexes. In consideration of the importance of genetic factors in the development of personality, it was expected that there would be differences among the three rodent species despite being exposed to similar environmental conditions. It was also expected that there would be differences between males and females within each species due to the influence of sex hormones on personality. Two standardised personality tests were conducted, namely the open-field and the novel object test to measure boldness, shyness, exploration, and avoidance when facing novelty by observing the frequency and duration of the behavioural responses exhibited during these tests. The study showed that rodents react to novelty by showing both shy and bold behavioural responses. However, the three species differ from each other in boldness and shyness. Males and females also showed differences in their behavioural responses to novelty. Overall, this study highlighted two strategies used for survival in nature. In consideration of this, it would be beneficial to preserve pristine forests to protect keystone structures that are crucial for preserving diversity in species and personality types. However, more studies on long-term trapping and correlation with personality tests could reveal more information on the personality profiles and their subsequent consequences.
The effects of concurrent extreme temperature and water deficit on the phytochemical profile and phytopharmacological activities in Portulacaria afra Jacq
(University of the Witwatersrand, Johannesburg, 2024) Adeleye, Oluwafunbi Christianah; Risenga, Ida
In nature, all plants are exposed to stress which are mostly biotic and abiotic stress factors. Previous studies have demonstrated the impact of various abiotic stress factors on the production of secondary metabolites in therapeutic plants. Plant responses to stressors brought on by a combination of antagonistic abiotic factors have shown to be phenomenal compared to when plants are exposed to single a factor. According to latest climate change models, it is believed that plants would suffer unique or demanding concurrent abiotic stresses in the years to come. South Africa has been experiencing increasing temperatures over last 40 years and being regarded as a climate change ‘hot spot’ by the Intergovernmental Panel on Climate Change (IPCC). Therefore, it is critical to conduct research on the impact of climate change on the bioactive compounds in therapeutic plants. The overarching aim of this study was to establish and scientifically document, for the first time to our knowledge, the phytochemical profile, medicinal properties and phytopharmacological attributes of Portulacaria afra, a widely renowned medicinal plant used for treating several skin conditions and oral infections which also includes the assessment of the effects of concurrent extreme temperatures and water deficit/drought on species’ biological activities. In this study, South African Portulacaria afra plants were selected from healthy parent plants and propagated from cuttings. Samples were allowed to grow and establish a root system in the greenhouse for up to three months. After three months, 180 potted plant samples were exposed to treatments and not watered for up to 144 hours (6 days), and 45 control samples were placed under 25oC (ambient) and watered every second day with 500ml of water. The control samples were kept at 25°C maximum night-time temperature (7pm to 5am) and 27°C maximum day time temperature. Plants undergoing treatment (coded as treatment A, B, C, D) were treated as follows: A and B were exposed to 0/10ºC (night/day) and 5/15ºC (night/day) respectively, while C and D were exposed 20/40°C (night/day) and 35/45°C (night/day), respectively. Five potted plants were harvested in each treatment three times for up to 6 days (144hrs). Sample harvesting was scheduled episodically every 48hrs (48, 96, 144) and were then airdried under 40°C for 2 to 3 days. The aqueous (water) extracts at a temperature of 60°C, alongside methanol, n-hexane, and ethyl acetate extracts were derived from the leaves, stems, and roots. The extracts were then used to investigate the phytochemical composition, antibacterial efficacy, antioxidant capacity and antidiabetic potential. The qualitative phytochemical screening encompassed the preliminary assessment of saponins, flavonoids, glycosides, quinones, phenols, terpenoids, steroids, phytosteroids, volatile oil, carbohydrates, amino acids, and coumarins. The quantitative analyses were performed to determine the total phenolic content (TPC), total flavonoid content (TFC), while the antioxidant assays were performed to determine the reducing, scavenging and chelating abilities against DPPH, H2O2 and metal (Iron) chelating. The antibacterial activities against gram-negative Escherichia coli and gram-positive Staphylococcus aureus, Streptomyces griseus were assessed through agar well diffusion assay. The antidiabetic potential was evaluated using In vitro inhibitory α-amylase assay. Chemical profiling of various extracts from the leaves, stems, and roots of P. afra was conducted to identify and quantify some secondary metabolites. The methanolic leaf extracts exhibited a notable presence of quinones, phenols, steroids, and coumarins, whereas the aqueous leaf extracts contained moderate presence of saponins, terpenoids, quinones, and coumarins. Ethyl acetate leaf extracts were characterized by a strong presence of tannins and a moderate presence of phytosteroids. Conversely, n-hexane leaf extracts showed considerable saponin levels, moderate tannins, and terpenoids. Significantly strong presence of secondary metabolites was observed in methanolic stem extracts, particularly terpenoids, steroids, phenols, and coumarins. Notably, coumarins, known for their anticancer properties, were prominently present in methanolic leaf and stem extracts, with a moderate presence in root extracts, hinting at potential pharmaceutical applications and future roles in public health. Aqueous stem extracts exhibited strong glycoside presence, while ethyl acetate and n-hexane stem extracts exhibited few fewer secondary metabolite groups, ranging from moderate to weak presence. Distinctive chemical profiles were observed in root extracts, with ethyl acetate extracts showing significantly stronger quinone presence. Methanolic root extracts displayed moderate presence of coumarins and glycosides, whereas aqueous root extracts showed a low glycoside presence. The highest total phenolic contents (TPCs) and total flavonoid contents (TFCs) were found in methanol stem extracts and aqueous root extracts, respectively. Notably, aqueous root extracts exhibited the highest TPC and TFC among all root extracts. Antibacterial activity assays showed a wide range on inhibitory effects of n-hexane extracts from leaf, stem, and root against test microorganisms. Ethyl acetate leaf extracts demonstrated considerable inhibitory efficacy against Staphylococcus aureus, while methanolic extracts showed zero zone of inhibition. Aqueous root extracts showed strong antibacterial activity against Staphylococcus aureus, whereas other extracts showed no significant activity. Inhibition zones ranged from 13 to 24 mm for the plant extracts. The assessment of antioxidant potential through DPPH, H₂O₂ scavenging, and metal chelating assays showed varied activity among extracts. Ethyl acetate root extracts showed the strongest H₂O₂ scavenging activity, while aqueous stem extracts showed the strongest antioxidant activity against DPPH radicals. Aqueous and n-hexane root extracts showed the strongest metal chelating ability. The in vitro antidiabetic activity showed that all plant parts were active against α-amylase, with the highest inhibitory action recorded from the methanolic leaf extracts, followed by the methanolic root extracts
The effects of resource variability on the demographic rates of black and white rhinoceroses
(University of the Witwatersrand, Johannesburg, 2023) Ndlovu, Latoya; Marshal, Jason
Given the importance of rhino survival and reproduction to conservation goals, the aim of the study was to investigate the effects of resource variability on the demographic rates of black (Diceros bicornis) and white (Ceratotherium simum) rhinos at Lapalala Wilderness. I used historical rhino-monitoring, rainfall and vegetation greenness data to investigate the vital rates of two rhino populations. I investigated population demographics (mainly density, growth rates, age and sex structure) and survival using stratified Cox models. Black and white rhino density peaked at 0.06 rhinos/km2 and 0.2 rhinos/km2 , respectively during the study period and was below the estimated maximum density for suitable rhino reserves. Average growth rate for the black rhinos was 4.784%, which was almost half of the white rhino’s rate of 8.861%. The survival of both species was stage-specific, and rainfall effects were similar for both species and age groups as low amounts of rainfall, which likely represent decreased forage availability, were associated with increased mortality risk. Decreasing greenness was also associated with increased mortality except with white rhino calves, where mortality increased with greenness. I suggest that this case might have been caused by their nutritional requirements: most grasses lose nutritional value as the season progresses (i.e., represented as increases in greenness values and so reduced access to high quality forage might affect mom’s body condition and her ability to produce nutritious milk, consequently resulting in increased mortality rates of calves. I also investigated the reproductive phenology (mainly conception and birth timing, age at primiparity and inter calving intervals) and birth sex ratios in relation to sex allocation theories. White rhinos conceived and calved at an earlier age compared to the black rhinos; mean age at primiparity for white and black rhinos was 9.448 years (8.467, 10.43) and 11.724 years (10.52, 12.927), respectively. Conceptions for both species peaked during the wet season and were associated with periods of high forage availability; however, births were asynchronous and occurred throughout the year. Effects of rainfall and greenness on age at first conception differed between species; the odds of having their first calf increased with rainfall, EVI and NDVI for white rhinos but decreased with EVI and NDVI for the black rhinos. Increases in wet-season integrated greenness during conception periods might indicate a shorter period of access to high quality forage for the black rhinos. Age at primiparity increased with density for both species because population density increases competition for resources, potentially making it difficult for females to accumulate the body mass and energy reserves needed to reproduce. Inter-calving intervals increased with rainfall, supporting the idea that excessive amounts of rainfall might result in lower forage quality, which then affects maternal body condition. In conclusion, vital rates of black and white rhinos are associated with resource availability as a function of environmental stochasticity and density, which in turn affects productivity and performance as climate change results in more variable conditions.
The function of “plant biltong” collected by bush Karoo rats (Otomys unisulcatus)
(University of the Witwatersrand, Johannesburg, 2024) Sanweni Siyabong Patrick
Food storing is a commonly observed strategy in many rodents living in environments with seasonally fluctuating food availability. Stored food allows small mammals to survive through food restricted periods and has been extensively studied in the northern hemisphere, characterised by cold winters. It could also be adaptive in semi-deserts of the southern hemisphere, such as the Succulent Karoo, which experience winter rainfall and hot dry summers. Here I want to understand the function of food plants carried back by bush Karoo rats (Otomys unisulcatus) to the stick lodges they build in the Succulent Karoo. Some of the food plants carried back to their lodges dry out, forming what I refer to as “plant biltong” or ‘plantong.’ To date, the function of the plantong remains unknown. Plantong might function as food in the dry season, or it might just be left over from food eaten at the lodge, or it can aid in construction of the lodges. I studied which plant species were collected as plantong, and whether there were seasonal differences in collection and consumption of plantong. I observed 15 lodges over 12 months and recorded the fate of plant pieces carried back to each lodge by bush Karoo rats. I tested experimentally whether they do eat the plantong. Plant species that were collected and dried out to become plantong were mostly annual shrubs (Zygophyllum retrofractum, Lycium cinereum, Salsola zeyheri, Helichrysum), grass species (Schismus) and perennials species (Atriplex, Drosanthemum spec, Galenia sarcophylla, Hermannia, Mesembryanthemum, oxalis sp, Chlorophytum crassinerve, Psilocaulon sp.). Most plant pieces were collected in winter and spring which is in the moist season. Plantong was consumed the most in the autumn (end of the dry season). Collected plant pieces were multifunctional. Most, 68%, of plant pieces carried back to the lodge were eaten green before they became plantong,Of the plant pieces that were collected, 12% were later eaten as plantong, 11% was incorporated into the structure of the lodge, while the fate of 9% was unknown. Experiments in captivity showed that bush Karoo rats indeed eat plantong. Plantong was not stored for months (from moist to dry season), but mostly days to weeks. Thus, I regard plantong as a food source derived from leftover food during collection and consumption but not as stored food for later consumption during harsh conditions.
The Impacts of Ungulate Foraging on Small Mammal Diversity in a Protected Site and Livestock Grazing Site
(University of the Witwatersrand, Johannesburg, 2023-09) Dlamini, Sifiso; Linhsan, Emmanuel Do; Madikiza, Kim
Vegetation cover and food availability are important determinants of how favourable an area is for the settlement of animals, especially small mammals such as rodents, which rely heavily on vegetation for protection against predators and access to food. This study investigated the impact that ungulate foraging activities (both domesticated and wild) have on small mammal diversity in two Short Euphorbia Thicket habitats within the Albany Thicket Biome: a natural site in the Great Fish River Nature Reserve and an adjacent livestock grazing site belonging to Kwandwe Private Game Reserve. Trapping was carried out over 7-day/7-night trapping sessions during the wet and dry seasons at each site, with grids of 10 x 10 traps with a 10 m spacing. Over a total of 5,600 trap nights/days, 272 unique individuals of six small mammal species (4 rodents, 1 shrew, and 1 sengi) were captured. Habitat (i.e., the 1 ha area studied on each site) and microhabitat differences were assessed for the two study sites using plant cover at different heights, the number of bushes, the presence of Euphorbia bothae, as well as the amount of bare ground and rocky surfaces around each trap station. Between the habitats, vegetation in all the height categories differed significantly during each season, while the number of bushes did not differ. The microhabitats also showed seasonal variation, with the dry season having less vegetation cover than the wet season. Although greater vegetation cover was recorded during the wet season, small mammal abundance was low, as were species richness and diversity. It was the dry season that had the higher small mammal abundance for both sites, with the protected site having four times the abundance (across all species) of the livestock grazing site. Small mammal diversity was, however, highest at the livestock grazing site, where the species were evenly represented, whereas the protected site had unevenly represented species with a lower diversity. It is concluded that both domesticated and wild ungulate foraging activities, as well as seasonal changes in climatic conditions, alter vegetation cover. This determines whether a habitat is conducive for small mammals, thereby driving their richness, abundance, and ultimately diversity within a habitat.
The implications of mandible morphology and dental structure on the feeding ecology and predatory behaviour in Hyaenidae (hyenas) using geometric morphometric analyses
(University of the Witwatersrand, Johannesburg, 2024) Nadioo, Riyanta; Iqbal, Safiyyah
Hyenas are often overlooked as being successful predators due to their scavenging behaviour. However, their morphological adaptations allow them to succeed in bone-cracking behaviour, an act that most carnivores are unable to achieve. Craniodental morphology influences carnivore performance, therefore understanding the functional morphology of carnivore mandibles would allow for the justification of Hyaenidae behaviour. This study investigates the morphological differences between the Hyaenidae mandible and large carnivore mandibles in Africa, as well as the differences in mandible morphology within the Hyaenidae family. This study uses a two-dimensional landmark-based geometric morphometric methodology to analyse morphological features on the carnivore mandibles and dentition to determine the morphological clusters linking the carnivore species, determine how the mandible morphology accommodates biomechanical needs, and to determine the implications that mandible morphology and dentition has on feeding ecology. The results of this study indicated that the sizes (PC1) of the carnivore mandibles were clustered according to their respective families (i.e. Hyaenidae, Canidae, and Felidae), however the shape (PC2) of the mandibles differed according to diet. The mandible morphology of the hypercarnivorous Hyaenidae displayed evident adaptations to osteophagy behaviour, including a thickened corpus, a large masseteric fossa, an anteriorly-displaced coronoid, and robust and blunt-like canines. The Proteles cristata, however, displayed mandibular adaptations to a hypocarnivorous diet. Ultimately, it was found that an increased resistance to bending forces and an increased area for muscle attachment on the mandible, directly relates to an increase in the Hyaenidae bite force, improving their feeding and hunting success.
The influence of plant phenolic compounds on the host range of Coniatus tamarisci Fabr. (Coleoptera: Curculionidae): a potential biological control agent of invasive Tamarix L. (Caryophyllales: Tamaricaceae) Taxa in South Africa
(University of the Witwatersrand, Johannesburg, 2022) Hatile, Sivenathi Luvolwethu; Byrne, Marcus; Mayonde, Samalesu
Tamarix L. (Caryophyllales: Tamaricaceae) are halophyte species that are native to Eurasia, North Africa, and southwestern Africa. These phreatophyte trees or shrubs have become prominent and widespread invaders in North America, South America, Australia, and South Africa. In South Africa, the Alien and Invasive Species regulations of the National Environmental Management: Biodiversity Act 2014 (NEM:BA) has classified invasive Tamarix as category 1b invader, which require control. Thus, three potential biological control agents have undergone laboratory-based host-specificity trials for the long-term sustainable control of Tamarix. The first two of these biocontrol agents, Diorhabda carinulata (Desbrochers.) (Coleoptera: Chrysomelidae) and Trabutina mannipara (Hemprich & Ehrenberg) (Hemiptera: Pseudococcidae), both failed the laboratory-based host-specificity trials because they completed their life cycle on the indigenous T. usneoides E. Mey ex Bunge. Previously, potential biocontrol agents were selected based on their native distribution and the phylogenetic relatedness of the invasive weed to indigenous nontarget species. However, it has recently been suggested that secondary metabolites also play a major role in insect host selection, and thus should be considered to improve the selection criteria of potential biocontrol agents. The current study is based on the third biocontrol agent that recently underwent laboratory based host-specificity trials in South Africa, Coniatus tamarisci (Fabr.) (Coleoptera: Curculionidae). This was in conjunction with an analysis of the potential influence Tamarix phenolic compounds have on insect host selection. The results show that although C. tamarisci could complete its’ life cycle on T. usneoides, the weevil had a low affiliation/risk associated with the indigenous Tamarix taxon. This advocates for the conduction of open field host-specificity trials, which will allow for a better understanding of C. tamarisci behaviour in a natural setting. Regarding phenolic compounds, three phenolic acids have been identified as being significantly prominent in T. usneoides compared to the invasive Tamarix taxa present in South Africa. These are gallic acid, dehydrodigallic acid, and syringic acid. These compounds are associated with protection from plant herbivory, which could explain the behaviour of C. tamarisci when exposed to and reared on T. usneoides.
The supply of ecosystem services along an urban-rural gradient, in Johannesburg, South Africa
(University of the Witwatersrand, Johannesburg, 2024) Jaxa, Busisiwe; Schwaibold, U.
Currently, the entire world is experiencing an unparalleled process of urbanisation, which is marked by an increase in population, economic progress, and the spread of urban areas. Although urbanisation presents opportunities such as economic advancement, enhanced infrastructure, and improved living conditions, it also brings about adverse effects on the natural environment. Ecosystem services vary along urban-rural gradients as they are largely affected by land use and land cover change. There is an increasing focus on urban ecosystem services that enhance urban resilience. Nonetheless, there has been minimal research conducted in South Africa regarding the effects of urbanisation on the provision of ecosystem services. This study aimed to investigate the impact of urbanisation on ecosystem services in the greater Johannesburg area and provide a deeper understanding of how the provision of three specific ecosystem services has evolved. These ecosystem services included temperature regulation, flood regulation and carbon sequestration. The land surface temperature (LST) along each gradient was derived from the Landsat (5 TM, 7 ETM+, 8 OLI) datasets available in the Google Earth Engine. Carbon storage was determined by estimating biomass using basic tree measurements. Soil compaction was measured as a proxy for the flood regulation ecosystem service. Lasty, land cover change was also assessed with the use of the ArcGIS software. The findings revealed that the supply of ecosystem services increased with an increasing distance from the city centre. Temperature and soil compaction were found to be high at the urban end of the gradient and carbon storage was found to be low at the urban end of the gradient. The land cover assessment revealed that the City of Johannesburg has suffered a substantial loss of green spaces over the 20 years, as the area covered by built-up surfaces increased. This study, therefore, has how how green spaces in urban areas enhance the sustainability of cities by supporting the supply of various ecosystem services including flood and climate regulation, carbon sequestration and storage. It has also shown that, the rapid urbanisation that the city experienced has led to a reduction in the overall supply of ecosystem services, whilst rural landscapes on the other hand continue to maintain the provision of these services. In order to enhance the green infrastructure in urban areas, it is recommended that, the urban natural systems are integrated in the urban planning and infrastructure initiative
The value of large trees and their protection where elephants and trees co-exist
(University of the Witwatersrand, Johannesburg, 2024) Cook, Robin Michael; Henley, Michelle; Witkowski, Edward
Increasing African elephant (Loxodonta africana) numbers in many southern African protected areas have raised concerns about their impact on large tree species and subsequent effects on biodiversity. However, sustainable strategies for managing elephant impact on particular large trees of concern require stakeholder support. Concerned stakeholders in South Africa's Associated Private Nature Reserves (APNR), a protected area containing a high density of waterholes and elephants, are implementing tree protection methods to protect large trees from elephant impact, but few studies have assessed these methods’ efficacy. This thesis aimed to understand stakeholder perception of the value of large trees. Thereafter, I investigate elephant impact on the large tree component within the APNR over a 12-year period while also assessing the relationship between the persistence of the nests of large tree nesting birds and that of the trees themselves. Lastly, I assessed the effectiveness of various implemented tree protection methods to mitigate against elephant impact. A combination of qualitative and quantitative analysis was used to measure stakeholders’ values on large tree and elephant population dynamics, as well as management strategies to reduce the impact on large trees. The results show that stakeholders were concerned about the loss of large trees and its impact on other species. However, they disagreed on the most effective management strategy to minimise elephant impact, with varying values across stakeholder generations and professions. The persistence trends of 2,758 large trees comprising three species of concern were analysed between 2008-2020 to understand the impact of elephants and other environmental factors on tree mortality. The annual large tree mortality rate from 2008-2020 was 5.6%, with varying declines among tree species and the most significant declines occurring during dry periods. Furthermore, the long-term impact of elephants on trees nested in by the critically endangered white-backed vulture (WbV, Gyps africanus) was studied in riparian and woodland habitats to investigate both tree and nest persistence. Ten tree species were utilised for nesting sites, with woodland trees more at risk to elephant impact verses those in the riparian habitat. However, there was no direct correlation between WbV nest loss and tree fall. Lastly, when considering tree protection methods, about half of the 2,758 trees surveyed were wire-netted as potential elephant impact mitigation strategy. Trees with a stem diameter >40 cm that were wire-netted had the highest persistence rates, but the wire-netting needed replacing after four years. Overall, wire-netting was the most practical method for larger- scale implementation, particularly on larger trees elephants cannot push over. Of the four tree protection methods evaluated in this study in terms of their effectiveness and practicality as a mitigation strategy, beehives were found to be the most effective at protecting trees but proved to be the most expensive in comparison to wire-netting, concrete pyramids and creosote jars
Tracing multiple aquatic ecosystem stressors across a land-use intensification gradient: A multi-tooled environmental forensic approach
(University of the Witwatersrand, Johannesburg, 2024) Levin, Jonathan Chaim; Woodford , D.J.; Curtis, C.J.
South Africa requires advanced freshwater management approaches to address complex catchment stressors acting on aquatic ecosystems. An environmental forensics toolbox could help disentangle pollution sources, informing stressor-focused adaptive management. Existing national, spatial resource strategies that define aquatic resource objectives, overlook modelling different aquatic stressor-linked components across spatio-temporal scales to disentangle individual stressor effects along land-use intensification gradients. This thesis investigated how spatio-temporal, physico-chemical water quality parameters, dissolved and sediment-bound trace metals as well as fish tissue δ34S all collected from 15 river sites in the tributaries of the Gwathle River Catchment, positioned in the Platinum Belt of South Africa across a land-use intensification gradient, can be used to disentangle aquatic stressors. Through using a spatio-temporal generalised linear mixed effects model (GLMM) approach, the importance of employing a multi-hydrological-spatial (sub-basin, cumulative basin and riparian buffer) scale approach to link stressors (drivers) to changes in key catchment water quality parameters as opposed to a single scale approach was identified. At the sub-basin scale, ammonium concentrations were best explained by urban stress through wastewater effluent, Cu increased with mining via leaching from pollution control dams and mineral discharges, while turbidity increased with higher agricultural coverage, following greater tillage practices and irrigation. River pH was positively predicted for by slope heterogeneity at the cumulative-basin scale, while sulfate increased with mining at the cumulative 100 m riparian buffer, from leaching and discharges. Dissolved inorganics, including trace metals, are routinely assessed in national aquatic resource assessments, yet metals in sediments demonstrating legacy effects, are yet to be integrated. Using geo-spatial models across seasons, dissolved and sediment Cr concentrations were found to be driven primarily by mining both at the sub-basin scale, while dissolved Zn concentrations reflected sub-basin lithology and sediment-bound Zn reflected cumulative basin scale urban stress and lithology. Concordance correlation indicated that the Cr had a substantial positive stress-tracking agreement between the two media, with both tracking Cr land-use intensification gradient inputs while Zn displayed negligible concordance. While fish tissue δ15N has been used to trace nutrient pollution, no local or international research has assessed time-integrated fish tissue δ34S as a sulfur stress-tracer from interacting urban, agricultural and mining stressors. Using a spatio- temporal GLMM modelling approach, it was found to be possible to distinguish key agricultural and mining stressors on aquatic ecosystems, with δ34S being relatively enriched following sub-basin scale agriculture and relatively depleted following cumulative basin scale mining activities. The outcomes of this research expands our knowledge base on using aquatic physico-chemical parameters, inorganic media indicators, and biotic tracers, towards the development of a potential environmental forensic toolbox to elucidate complex pollution sources and pathways for enhanced catchment management and freshwater governance in South Africa.
Understanding disturbance, vegetation density, seed banks and pollination for the conservation of Protea curvata
(University of the Witwatersrand, Johannesburg, 2023) Mabuza, Precious Gugulethu Babalwa; Balkwil, Kevin
Background Aims: Protea curvata (Proteaceae) is a threatened species endemic to Mpumalanga, South Africa. Previous records of the species showed discrepancies in location data and information on population demographics was sparse. At the time of the study (2018), the last IUCN assessment of P. curvata was 20 years ago and one subpopulation of the species was reported to have a low number of mature individuals. In 2017, a census of another subpopulation indicated that the mature individuals were the most abundant cohort and there was no recruitment of P. curvata seedlings. Thus, there was uncertainty regarding how population size, population demographics and threats faced by the species may have changed over the last 20 years. The study aimed to update the IUCN status of P. curvata and to assess factors relating to P. curvata recruitment, namely the breeding biology of the species and the woody species composition on P. curvata sites. Methods: A census was conducted on P. curvata sites. Census data and site composition was compared between sites with contrasting management. Soil samples were collected from six sites. Pollination modes in P. curvata were investigated by manually pollinating inflorescences that were covered at bud phase to exclude animal pollinators. Five treatments were tested: autogamous selfing, tree geitonogamous selfing, inflorescences geitonogamous selfing, natural outcrossing and pollen supplemented outcrossing. Seeds from each treatment were weighed and tested for viability using TTZ staining. Animal pollinators were observed in the field and through camera traps positioned in front of non-covered inflorescences. Key Results: Five subpopulations were identified. P. curvata recruitment was low in two subpopulations and absent in three subpopulations. When comparing the site with the lowest recruitment (Site A) to the site with the highest recruitment (Site C), woody cover and tree density was higher on the site with low recruitment – indicating bush encroachment. This was attributed primarily to long intervals between fires at Site A. Site A showed a concerning net decline in subpopulation size (3% loss per year). Despite having more P. curvata juveniles, Subpopulation C showed a similar rate of decline (2% loss per year). The species was identified as endangered; with severe hailstorms and delayed, intense fires posing the major threats. Hailstorms compounded fire-induced damage on P. curvata bark. Flowering declined significantly after a hailstorm. (x̄pre-hail = 10.94 inflorescences per tree, x̄post-hail = 4.28 inflorescences per tree, p-value = 0.0031). During pollination experiments, Protea curvata was able to self-pollinate. However, seed mass and viability were significantly higher in outcrossed treatments. Viability in naturally outcrossed treatments (x̄=42.7%) was similar to pollen-supplemented outcrossed treatments (x̄=32.1%), but significantly higher than treatments of autogamous selfing (x̄=21.95%), geitonogamous selfing within inflorescences (x̄=27.1%) and geitonogamous selfing within trees (x̄=26.2%) [C.I= 95%; d.f.= 4, 95; Fcalc= 4.5; p = 0.0021]. Colletid bees and Apid bees contributed to P. curvata pollination via geitonogamy and early removal of self-pollen from stigmas. Birds were the most frequent visitors of P. curvata and were the most effective pollinators due to their prominent role in natural outcrossing. Bats infrequently visited inflorescences but may possibly complement outcrossing since they make contact with stigmas and do not spend their visit time restricted to one inflorescence or tree. P. curvata was non-serotinous and possessed a short-lived, soil seed bank. Across all sites, the average viability of seeds in the soil was well below that of freshly collected seeds from pollination experiments (4–9% for soil seed bank; 22.0–42.6% for fresh seeds). Seed bank size was surprisingly low in subpopulations with high flowering. Conclusions: Reducing seed loss after release from the canopy appeared to be more important than high flowering for maintaining a large seed bank. Therefore mild, frequent fires will be essential for reducing bush encroachment, making way for seed deposition and encouraging seedling survival

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Browsing School of Animal, Plant and Environmental Sciences (ETDs) by SDG "SDG-15: Life on land"

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