WIReDSpace

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Communities in WIReDSpace

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Now showing 1 - 5 of 20

Recent Submissions

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    How energy and thermal landscapes influence habitat use in chacma baboons (Papio ursinus)
    (University of the Witwatersrand, Johannesburg, 2025-10) Botha, Katinka; Hetem, Robyn; McFarland, Richard
    Landscape heterogeneity drives chacma baboon movement, behaviour and habitat use. Here, baboons alter their responses to the changing environment to balance thermoregulation and resource acquisition. This study incorporated historical data from multiple habituated troops within the Swebeswebe Wildlife Estate, along with more current field data collected while following a troop of 69 individuals. Behavioural data were collected in 30-minute scan sampling intervals to assess activity budgets and shade use, while corresponding GPS data tracked movement. Climatic conditions were recorded through an onsite weather station along with miniglobe thermometers placed in representative microhabitats, including one carried while tracking the troop. Landscape features, and food and water availability were mapped to analyse how biotic and abiotic factors influenced troop movement, behaviour and habitat use. Baboons travelled further under high heat loads and low water availability. They, however, only expanded their home ranges, particularly along the main river system, during periods of water scarcity. In contrast to travel distance, the frequency of travel behaviour, as well as rest behaviour, increased with higher temperatures and water availability. As a result, a trade-off was observed in foraging behaviour, highlighting prioritisation between thermoregulation and energy acquisition with differing environmental drivers. Social behaviour decreased under higher water availability but, in contrast, increased with higher vegetation greenness. Vegetation greenness was a key driver to shade use, a behaviour critical for thermoregulation, particularly under higher heat loads. In line with thermoregulatory activity, baboons selected stable microclimates, preferring cooler, densely vegetated habitats, particularly during peak heat loads in the day and in the wet season. Baboon distribution shifted seasonally, with troops found closer to their main cave sleep site and rivers during the dry season and being found further away from fence lines. This indicated a more constrained spatial use pattern in times of resource scarcity. These findings highlight the flexible responses of baboons to thermal and resource landscapes. The understanding of these patterns is crucial for their conservation through the protection of heterogeneous landscapes, and a broader understanding of their ecological resilience in the face of worsening climate change.
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    The relationship between landscape functional patch type and soil ecotoxicity along a pollution gradient
    (University of the Witwatersrand, Johannesburg, 2025-10) Bisnath, Celine; Situngu, Sivu; Weiersbye, Isabel
    Anthropogenic stressors such as mining and smelting disrupt soil processes and degrade landscape functionality, creating long-term barriers to ecological rehabilitation. The Landscape Function Analysis (LFA) model is widely used to monitor landscape recovery. It works by delineating a fixed portion of the landscape into regions of resource accumulation (patches) and areas of resource loss (interpatches). Each region is then visually and physically assessed for its soil-surface attributes, which relate to indices of landscape function (stability, infiltration, and nutrient cycling). However, the LFA model is field-based, so it cannot directly capture landscape function in terms of chemical and ecotoxicological degradation, and these are integral aspects of ecosystem function. This study aimed to determine whether complementing soil physicochemical and ecotoxicological indicators with LFA metrics could improve the assessment of ecosystem function in contaminated environments. This research was conducted along a heavy metal pollution gradient at an area next to a smelter complex, using the Trigger–Transfer–Reserve–Pulse (TTRP) model as a conceptual foundation. Three complementary approaches were applied: (1) measuring soil properties and deriving LFA indices in patches and interpatches; (2) assessing the toxicity of soil leachates to the euryhaline cladoceran Daphnia magna (D. magna) and the marine bacterium Aliivibrio fischeri (A. fischeri); and (3) evaluating soil and leachate phytotoxicity using vascular plant bioassays. The results indicated significant variation in soil chemistry along the gradient, with decreasing organic matter (p = 0.003) under higher contamination. The correlations between the LFA indices and soil parameters were weak, indicating that surface indicators were insufficient to reflect subsurface chemical impairment. For toxicity to D. magna and A. fischeri, the results revealed significant toxicity in leachates from highly contaminated sites, with increased immobilisation of D. magna (p = 0.021) and inhibition of A. fischeri luminescence (p < 0.001) corresponding to higher concentrations of Cu, Zn, and Pb. Some leachates from areas with moderate LFA scores still exhibited strong toxicity, indicating that the visual surface condition may underestimate chemical stressors. The vascular plant bioassays revealed strong inhibition of germination (p < 0.05) and root growth (p < 0.05) in soils and leachates from highly contaminated areas, with root elongation being the most sensitive endpoint. These vascular plant patterns were consistent with aquatic bioassay results and correlated with elevated metal concentrations and electrical conductivity (r = 0.67 and r = 0.92, respectively). Differences between patch and interpatch soils diminished with increasing contamination. Collectively, these findings showed that heavy metal contamination and salinity decouple surface structure from subsurface processes, disrupting the TTRP feedback that maintains landscape resilience. This study proposes an expanded LFA framework for smelter contaminated sites, incorporating chemical and ecotoxicological diagnostics alongside traditional surface metrics. The integrated approach captures both visible and latent dimensions of ecosystem function, offering a more mechanistic and sensitive tool for monitoring rehabilitation and ecological recovery in degraded areas.
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    Development of new radiation hard materials with high secondary electron emission yield for the nuclear industry
    (University of the Witwatersrand, Johannesburg, 2025-09) Baldwin, Cameron Lance; Sideras-Haddad, Elias
    Photomultiplier tubes (PMTs) play a crucial role in various research fields, particularly in particle physics, where they serve as highly sensitive detectors for light. These experiments often occur in environments with extreme radiation levels, exposing PMT components to prolonged radiation damage that can degrade their performance over time. A critical element in the PMT structure is the dynode system, which facilitates signal amplification through the secondary electron yield (SEY) mechanism. SEY is fundamental to enhancing the initial photoelectron signal, making it essential to the detection process. Therefore, materials used for dynodes must not only exhibit a high SEY but also possess significant radiation hardness to ensure long-term stability and minimize frequent replacements. In this study, Aluminum Oxide (Al2O3) and Magnesium Oxide (MgO) were selected for evaluation based on their potential to meet these criteria. The materials were subjected to controlled gamma irradiation from a Co-60 source at varying doses. Theoretical Monte Carlo simulations were conducted to assess the radiation damage in terms of displacements per atom (DPA), while SEY measurements were performed post-irradiation to quantify the impact of the radiation exposure on the SEY of the Al2O3 and MgO samples. SEY measurements were conducted at the 6 MeV Tandem Accelerator at the iThemba Laboratory for Accelerator-Based Sciences (LABS) in Johannesburg. The existing microprobe setup was adapted to enable electronic measurements of SEY from MgO and Al2O3 samples across different radiation doses. These adaptations allowed for precise quantification of SEY variations as a function of absorbed gamma radiation dose. The results indicate a clear inverse relationship between radiation dose and SEY: as the radiation dose increases, SEY decreases. This degradation is attributed to ionizing events induced by gamma rays, leading to the formation of vacancies and interstitial defects within the material. These structural defects alter the electronic properties of the dynodes, ultimately reducing their amplification efficiency (SEY). This study provides valuable insights into the radiation tolerance of dynode materials and highlights the importance of selecting robust materials to enhance the longevity and reliability of PMTs in radiation harsh environments.
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    Investigating the Challenges of Adopting Social Media Intelligence (SOCMINT) as a Tool for Mitigating National Security Threats in South Africa – The July 2021 Unrest Case Study
    (University of the Witwatersrand, Johannesburg, 2025) Rikhotso, Bridget Vulani; Moodley, Kebashnee
    The purpose of this study was to examine the challenges faced by the South African intelligence community in adopting Social Media Intelligence (SOCMINT) as a tool for mitigating national security threats, particularly in light of the failure to predict the July 2021 civil unrest. As we enter the Fourth Industrial Revolution (4IR), technological innovations are reshaping the intelligence collection landscape, with social media technologies offering new methods for addressing national security concerns. Despite the significance of SOCMINT, the South African intelligence agencies have not fully embraced this discipline, contributing to one of the nation's major intelligence failures. While the driving forces and consequences of the July 2021 unrest have been extensively analysed, the reasons behind the intelligence agencies' inability to anticipate it remains underexplored. This interpretive study aimed to uncover these challenges, guided by the Technology-Organisation-Environment (TOE) framework integrated with the Unified Theory of Acceptance and Use of Technology (UTAUT). Data was collected from intelligence experts and analysts to provide a comprehensive perspective on the issue. A single organisation case study approach was adopted to achieve a deeper understanding of the phenomenon within the intelligence community. This study developed an integrated conceptual framework underpinned by the Technology Organisation Environment (TOE) framework and UTAUT Theory. This integrated framework was used to investigate the challenges that hinder the adoption of SOCMINT through a qualitative case study that was conducted in the South African intelligence community. Data for this research was collected from twelve participants representing operations, IT, analysts, and management. Findings revealed that the major challenges experienced are more organisational (Management support, Technology Inclination and Cost) and environmental (Silo, Government Regulations and Coordination) as factors of adoption. From the technological context, there were no major challenges highlighted with the exception of security. Other technological factors or challenges raised by participants, compatibility, expectancy, and performance, were unpersuasive and immaterial to the adoption of SOCMINT.