School of Animal, Plant and Environmental Sciences (ETDs)
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Item Surface water dependencies and activity patterns of mammalian herbivores in South Africa(University of the Witwatersrand, Johannesburg, 2024-10) Padayachy, Janiel; Hetem, Robyn; Strauss, Willem Maartin; Venter, JanAn increase in aridity in Africa may make water availability more variable, thus understanding how animals respond to these conditions is important for future wildlife management and conservation. However, mammalian herbivores with varying water requirements may respond differently to changes in water availability and predation. Using camera trap data, I analysed the spatial distribution relative to surface water sources and the 24-hour activity of 16 mammalian herbivores across 10 sites in South Africa. As expected, water dependent herbivores were generally closer to water, but only at sites where lions were absent. Herbivores with low water requirements were more nocturnal, potentially reducing water required to cool themselves evaporatively when active during the heat of the day. But that nocturnal activity was reduced when lions were present, likely reducing predation risk, increasing water requirements to dissipate heat and forcing herbivores to remain close to water. Nocturnal activity increased with body size in mixed-feeders and grazers, but decreased with body size in browsers, potentially reflecting more time spent foraging by large browsers. Using a novel approach of multistate diel occupancy models I showed that herbivores were generally active during both the day and night, and that the presence of lions impacted occupancy of preferred prey species (blue wildebeest, gemsbok and zebra). Diel occupancy of water-dependent prey (blue wildebeest) was influenced by an interaction between lion presence and distance to water sources. Thus environmental factors as well as physiological and morphological features affected the timing of activity and spatial distribution of several mammalian herbivore species in South African wildlife areas, which should be considered for future research and management of these species.Item The Gene Catalogue and Functional Analysis of the Gut Microbiome of Lions in Etosha National Park(University of the Witwatersrand, Johannesburg, 2024-09) Belger, Carl Warner; Hetem, Robyn; Hazelhurst, ScottCharacterising the microbiomes of free-living mammals may aid conservation efforts, yet the gut microbiome of carnivores is underrepresented. This study represents the first description of the gut microbiome of free-living African lions (Panthera leo melanochaita). Faecal samples from 20 lions were collected in Etosha National Park, Namibia and microbial DNA was extracted. Samples were then whole genome sequenced, and classified using MetaPhlAn and Genome Taxonomy Database toolkit. The two most abundant bacterial genera in the lions’ gut microbiomes were Bacteroides (16.9%) and Phocaeicola (16.6%). Microbiome diversity was similar between the sexes and across seasons as assessed through Bray-Curtis dissimilarity and Shannon diversity index. The genus Clostridium_AH was more abundant in male lions (P = 0.007; d.f. = 22), while Aphodousia (P = 0.003; d.f. = 22) was more abundant in females. Lions captured in winter had a high abundance of Plesiomonas relative to those captured in summer (P = 0.008), whereas lions captured in summer a high abundance of Dysosmobacter (P = 0.038; d.f. = 22), Pelethomonas (P = 0.021; d.f. = 22), Metalachnospira (P = 0.033; d.f. = 22) and Clostridium Q (P = 0.012; d.f. = 22) compared to those captured in winter. Following various taxonomic classification approaches, a third of the reads (33.6%) present in the lion gut microbiome remained unclassified. We constructed 272 metagenome assembled genomes, from seven bacterial phyla, representing mostly new species which will contribute to understanding of the carnivore gut microbiome.Item The potential of regenerative agriculture in creating climate adaptive and gender inclusive food systems: a study of rural communities in Mpumalanga, South Africa(University of the Witwatersrand, Johannesburg, 2024-08) Govender, Yashila; Kabisa, Mulako; Pereira, LauraNumerous social-ecological risks to food systems are brought on by industrial agriculture – resulting in various narratives around the sustainability of agriculture, offering a solution to the problems confronting this system. One of these narratives is regenerative agriculture (RA), which has recently gained popularity. The potential of regenerative agriculture could contribute to sustainable agriculture and is capable of addressing climate adaptation challenges and potentially fostering gender inclusivity within food systems. Despite growing interest around regenerative agriculture, this concept is not well understood or researched in South Africa, especially in rural farming villages. This research delves into the multifaceted domain of regenerative agriculture and looks to describe this in the South African context. This study sets out to achieve three research questions, what is the definition of regenerative agriculture in a South African context, what is the current understanding around this concept among smallholder farmers in farming villages of Bushbuckridge and if so, how does regenerative agriculture considers the local gender dynamics in rural farming communities? A mixed methods approach was used for this study. Ten expert interviews with key stakeholders in the agricultural sector were conducted to construct a definition of regenerative agriculture tailored to South African conditions. Thereafter, individual interviews were used to gauge the level of understanding and adoption of regenerative practices among smallholder farmers in the villages of Bushbuckridge. This sample consisted of 74.2% female and 25.8% male. Finally, an in-depth analysis of how regenerative agriculture compared with local dynamics in rural farming communities was conducted through participatory engagement. A total of 54 participants participated in focus group discussions. The results indicate there is a multifaceted understanding of regenerative agriculture in South Africa, with most experts indicating that regenerative agriculture is practiced under the name of conservation agriculture (CA). Aspects of both practices have some commonalities with agroecology, such as principles of soil conservation, polyculture and no-tillage that are highly promoted in South Africa. Additionally, smallholder farmers in Mpumalanga practice regenerative agriculture, with different adoption rates in different villages. Furthermore, this research highlights that the adoption of regenerative agriculture in rural farming communities requires further discussion and stakeholder engagement, especially with women, and includes socio-economic and cultural factors. This study contributes to the broader discourse on regenerative agriculture by providing a context-specific definition, indicating that regenerative agriculture is an overlap of agroecology and conservation agriculture in South Africa, shedding light on the challenges and opportunities for smallholder adoption, and emphasizing the importance of community-based approaches in regenerative agriculture educational programs. The research underscores the need for tailored education and extension programs that account for local conditions and socio-cultural factors.Item An initial estimation of the concentrations of methane (CH4) emitted from the Wakkerstroom wetland and Majuba power station in Mpumalanga province, South Africa(University of the Witwatersrand, Johannesburg, 2024-08) Bobo, Christine; Scholes, Mary C.; Furniss, David. G.The continuous increase in methane (CH4) emissions to the atmosphere poses a formidable challenge to Earth's climate resilience and exacerbates the impacts of global warming. This study compared microbial CH4 concentrations from the Wakkerstroom wetland to fossil fuel concentrations from the coal stockpiles at the Majuba power station in Mpumalanga, South Africa, using three methodological approaches: flexfoil bags, isotopic analysis, and satellite data. Seasonal ground measurements were collected in 3L flexfoil bags and analysed for CH4 mole fraction using a Picarro 2301 calibrated to the WMO X2004A CH4 scale. Samples were prepared for isotopic analysis by continuous-flow isotope-ratio mass spectrometry using an Isoprime Trace Gas system. Findings from ground sampling measurements showed that for three out of the four seasons, Phragmites australis at the Wakkerstroom wetland had the highest CH4 concentration [spring (0.209 ± 0.076 ppm), autumn (0.537 ± 0.239 ppm), and winter (0.132 ± 0.065 ppm)], and the coal stockpiles at the Majuba power station had the lowest CH4 concentration [summer (0.022 ± 0.021 ppm), autumn (0.014 ± 0.053 ppm), and winter (0.002 ± 0.004)]. Isotopic measurements, which identify and differentiate gas sources by examining distinct isotopic signatures, showed that the Wakkerstroom wetland had consistently light, 13C depleted isotopic signatures seasonally ranging between -61.4‰ to -55.6‰. In contrast to this, the Majuba power station coal stockpiles had inconsistent isotopic signatures through the sampling seasons- heavier CH4 emission isotopic signatures with 13C enrichment during spring and summer at -35.3 ± 1.0 ‰ and -43.5 ± 3.5 ‰ respectively, and lighter isotopic signatures with 13C depletion during autumn and winter of - 62.0 ± 1.6 ‰ and - 87.0 ± 10.3 ‰ respectively. On a larger temporal and spatial scale, satellite-based measurements from the Tropospheric Monitoring Instrument (TROPOMI) showed no significant differences between Wakkerstroom (1855.4 ± 18.0 ppb) and Majuba power station (1857.1 ± 22.9 ppb) in terms of the total column averaged dry-air mole fraction of methane (XCH4). An increasing trend in CH4 mole fraction, in Southern Africa as measured at Cape Point Global Atmospheric Watch (GAW) station over a 39-year period was also observed. Meteorological variables, particularly wind direction, had a more significant impact on CH4 mole fractions at Cape Point than at the Wakkerstroom wetland. The multi-faceted approach of utilizing the three measurement techniques provided a comprehensive view of atmospheric CH4 showing that wetlands could be more significant CH4 hotspots in comparison to coal stockpiles at power stations. Measuring methane concentrations is challenging due to its inherent complexity, thus the utilisation of different measurement methodologies further highlighted the spatial and temporal variability of CH4 concentrations at both the wetland and the coal stockpiles.Item Behavioural and physiological responses of sable antelope to heat and aridity(University of the Witwatersrand, Johannesburg, 2024-10) Haylock, Kiara Avelyen; Hetem, Robyn; Parrini, FrancescaThe increased probability of longer, more extreme dry seasons, due to rapidly rising temperatures and the increased frequency and intensity of droughts, threatens water-dependent, selective grazers throughout Africa. Phenotypic plasticity such as behavioural adjustments and physiological flexibility may buffer the impacts of spatiotemporal variations in resource availability and climate. My project aimed to assess variations in home range size, movement distances, behavioural states of movement, fine-scale activity, microclimate selection and body temperature of sable antelope (Hippotragus niger niger), a water-dependent selective grazer, in relation to spatiotemporal variation in vegetation greenness and environmental heat load. To address the aim of my project, I measured body temperature and fine-scale activity using biologging in ten free-living GPS-collared sable antelopes in the semi-arid Bwabwata National Park of Namibia. Each collar was fitted with a miniature black globe thermometer to assess microclimate selection. A weather station with a standard black globe thermometer recorded black globe temperature and air temperature. Data collection spanned 24 months, from May 2016 to April 2018. The dry season was a critical period for sable antelopes, particularly the late dry season when high ambient temperatures compounded reduced resource availability. As conditions became hotter and browner with the progression of the dry season, home ranges elongated towards the Kavango River and increased in size by ~50% from the early dry to the late dry season. In response to increased 24-hour mean black globe temperature and increased exposure to brown vegetation, the 24-hour mean hourly displacement distance of sable antelopes increased with progression of the dry season, mostly due to the increased frequency of long, directed movements to the Kavango River during the late dry season. One sable antelope travelled between 13 and 30 kms every 4-5 days to access water from the river during the late dry season. Using Hidden Markov Models, four behavioural states were identified from the movement tracks of sable antelopes: resting, foraging, local movement and relocating. The long, directed movements to water, classified as a relocating behavioural state, predominated during the late dry season. Sable antelope displayed an increase in relocating behaviour and a decrease in foraging behaviour associated with high 24-hour mean black globe temperature and increased proportion of brown vegetation exposure. Sable antelopes also displayed an increase in local movement with increased exposure to brown vegetation and high 24-hour mean black globe temperature, but a decrease in resting behaviour with an increase in the proportion of brown vegetation exposure. Driven by decreasing vegetation greenness and increasing black globe temperatures, sable antelopes reduced their diurnal proportion of activity with progression of the dry season, associated with a reduction in activity during the heat of the day in response to increased exposure to brown vegetation, high 24-hour mean black globe temperature and an increased proportion of time spent in the shade. Sable antelopes did not fully compensate for lost diurnal activity, despite increased nocturnal activity during hot and dry conditions, as total 24-hour activity decreased with progression of the dry season. Sable antelopes also selected higher quality microclimates (i.e. microclimates that were on average 6.7 ± 0.2 oC cooler than direct sun) when increasingly exposed to brown vegetation and high 24-hour maximum black globe temperature. Fluctuations in 24-hour body temperature increased during the dry season with maximum amplitudes of body temperature rhythm of >5 oC within a single day during the late dry season. Sable antelopes displayed a reduction in minimum 24-hour body temperature in response to decreased 24-hour black globe temperature and increased exposure to brown vegetation during the early dry season, likely due to energy deprivation. While minimum body temperatures remained low during the late dry season, sable antelopes displayed an increase in maximum 24-hour body temperature in response to increased mean 24-hour black globe temperature and increased exposure to brown vegetation, likely due to water deprivation. High maximum 24-hour body temperatures, indicative of dehydration-induced hyperthermia, increased the likelihood of relocating movements to the Kavango River which in turn were associated with a subsequent decline in maximum 24-hour body temperatures. By linking body temperature to a behavioural state of movement, I am the first to demonstrate a direct link between access to a water resource and maximum body temperature in a free-living antelope species. The behavioural flexibility exhibited by sable antelopes during the dry season failed to buffer reduced resource availability as fluctuations in body temperature indicated that sable antelopes experienced nutritional and water stress. My findings highlight the importance of incorporating physiological measurements into behavioural and ecological studies to inform management decisions and improve conservation efforts in the face of climate change.Item Landscape-scale carbon stocks in the subtropical thicket of the Baviaanskloof, South Africa(University of the Witwatersrand, Johannesburg, 2024-08) Kooverjee, Neha; Smart, Kathleen; Fisher, Jolene; Scholes, BobSouth Africa’s subtropical thicket biome has garnered interest for its potential for carbon sequestration through the restoration of degraded land, funded locally and internationally by the carbon market. Accurate carbon estimation of pre- and post-restoration carbon storage is key to monitoring the progress of restoration efforts and determining accurate estimates of carbon increase. Most past thicket studies have based landscape-scale carbon estimates on plot data alone, without accounting for the spatial variation in factors such as soil depth, resulting in overestimates of the average potential carbon that can be stored. The aim of this research was to estimate and create maps showing the spatial distribution of the thicket carbon stocks in the Baviaanskloof Nature Reserve, South Africa, by calculating the amount of carbon stored in the soil, woody biomass, root biomass and litter biomass across the thicket area of the reserve using plot data with remote sensing imagery. Soil organic carbon was estimated using soil profile data collected in the same primary catchment as the Baviaanskloof and extrapolated across the landscape using a Random Forest-based regression model. Woody carbon was estimated using previously recorded in situ carbon recordings. This data was then extrapolated across the landscape using raster data for vegetation height and cover, climate data, and elevation as predictor variables. Root and litter carbon were then calculated individually based on the woody carbon estimates and ratios of root and litter carbon to woody carbon from a past study. The average soil organic carbon (37.7 ± 29 t ha-1), woody carbon (18.1 ± 4 t ha-1), root carbon (3.1 ± 0.7 t ha-1), and litter carbon (2.4 ± 0.5 t ha-1) estimated in this study for intact thicket are all lower to varying degrees than those of past thicket studies that were based solely on plot data, indicating the importance of accounting for variation in the landscape and its effect on carbon stocks. The results of this study indicate that slope position, a proxy for soil depth, has a significant effect on thicket carbon stock. Woody carbon, root carbon and litter carbon estimates significantly decreased downslope, but soil organic carbon, the largest carbon pool in thicket, significantly increased downslope. In general, the results also indicate an increase in carbon after restoration, however, an illogical trend of lower potential root and litter carbon compared to current carbon in degraded thicket is present, indicating that the results of this study are not reliable for restoration planning and decision-making. This may be due to the inaccuracy of global Light Detection and Ranging (LiDAR) products, such as the Global Land Analysis and Discovery (GLAD) canopy height dataset, over non-forested areas such as thicket which are much shorter. Accurate estimates of current and potential carbon and accurate monitoring of restoration is important in tracking South Africa’s progress towards its biodiversity conservation goals under the Convention on Biological Diversity, and carbon emission reduction goals under the Paris Agreement. With access to locally captured LiDAR imagery that is suited to the short, dense structure of thicket vegetation and the topography of the landscape, and a larger database of in situ thicket carbon recordings, the methods used in this study could be employed to calculate more accurate carbon estimates and aid in directing restoration efforts to the most appropriate areas.Item 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, 2024-03) Naidoo, Riyanta; Iqbal, SafiyyahHyenas 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.Item Higher Education Sustainability: Investigating the barriers and opportunities to sustainable infrastructural development in tertiary education institutions(University of the Witwatersrand, Johannesburg, 2024-03) Buthelezi, Nontobeko Lynda Valerie; Engelbrecht, Francois; Reid, MemoryThe research investigates sustainability initiatives in South African higher education, focusing on the refurbishment of water heating systems at the University of the Witwatersrand, Johannesburg. It examines the economic and environmental impacts of adopting greener technologies, highlighting the importance of stakeholder engagement. Using a mixed methods approach, the study combines qualitative interviews to understand stakeholder perspectives with quantitative analysis of costs and carbon emissions. The findings reveal that the new water heating system significantly reduces emissions—6.6 times less than the traditional system—resulting in a 9.71 kg monthly carbon footprint versus 64.296 kg with old geysers. Financial analysis shows an 81% cost reduction in water heating expenses due to the switch from grid electricity to natural gas, achieving a 4.16% return on investment. The research underscores the challenges in securing broad stakeholder support and the importance of a holistic sustainability approach that integrates economic, environmental, and social factors. It highlights the potential of such initiatives to reduce environmental impact, save costs, and drive innovation, providing insights for future sustainability efforts in higher education.Item The Effects of Land Use Change on Water Quality in the upper Berg - and Breede River catchments, Western Cape, South Africa(University of the Witwatersrand, Johannesburg, 2024-08) van Wyngaard, Zahn; Sheridan, CraigPollution of surface water resources is gaining global attention due to increasing freshwater stress and scarcity. This study assessed how land use changes in the upper catchments of the Berg and Breede rivers affect water quality. Land Cover Data, covering a 22-year period, was prepared, categorised, and analysed. Land use classes include “natural”, “urban”, “agricultural”, “water bodies”, “mining” as well as “degraded land, bare rock, and soil”. Changes of these land use classes were analysed to establish their influence on water quality parameters such as electrical conductivity, pH, total nitrogen including ammonium, nitrate and nitrite, orthophosphate, and sulfate. In the Berg River catchment, urban, natural, water bodies and degraded land, bare rock, and soil increased while agricultural and mining decreased. In the Breede River catchment, urban, water bodies and degraded land, bare rock, and soil as well as mining increased while agricultural and natural decreased. In the Berg River catchment, Dissolved Inorganic Nitrogen (ammonium, nitrate and nitrite), as well as pH increased while electrical conductivity, sulfate, and orthophosphate decreased. In the Breede River catchment, ammonium and orthophosphate increased while a decrease in electrical conductivity, nitrate and nitrite, pH, and sulfate was noted. In the Berg River catchment, the following correlations, or relationships, were noted. Urban land was correlated with ammonium and sulfate; agricultural land was correlated with electrical conductivity and sulfate, natural land cover was correlated with electrical conductivity, orthophosphate, and sulfate. Water bodies were correlated with orthophosphate, sulfate, degraded land, bare rock, and soil was correlated with ammonium and mining was correlated with electrical conductivity, orthophosphate, and sulfate. In the Breede River catchment, urban land was correlated with ammonium and orthophosphate, agricultural land was correlated with nitrate and nitrite and pH, and natural land cover was correlated with electrical conductivity, ammonium, and sulfate. Water bodies were correlated with electrical conductivity, nitrate and nitrite, and sulfate, degraded land, bare rock, and soil were correlated with electrical conductivity, ammonium, orthophosphate, and sulfate, and mining was correlated with electrical conductivity, ammonium and sulfate. The study therefore recommends that we mitigate land use change impacts on water quality by enforcing strict land-use regulations, promote sustainable agricultural practices, protect riparian areas and wetlands, implement better stormwater and wastewater management, educate the public, and coordinate integrated water resource management efforts to reduce pollution of scarce surface water resources.Item Assessing the climatic suitability and environmental responses of Anthonomus morticinus Clark (Coleoptera: Curculionidae), a potential biological control agent of Solanum mauritianum Scopoli (Solanaceae) in South Africa(University of the Witwatersrand, Johannesburg, 2024-10) Keizan, Yaron Yakov; Byrne, Marcus; Venter, NicInsect biology is greatly influenced by the surrounding climate. Desiccation, owing to low relative humidity, poses a significant threat to insect populations, especially those with small body sizes. To avoid exposure to low relative humidity (RH) levels, insects actively seek out nearby microenvironments with raised RH. The flowerbud feeding weevil Anthonomus morticinus is an optimistic agent to limit the spread of the highly invasive Solanum mauritianum throughout South Africa. However, the restricted geographic range shown by A. santacruzi in South Africa due to climatic unsuitability questions how A. morticinus will respond to climatic variables, particularly humidity. The effect of low temperatures has shown to be a limiting factor by Mkhomazi (2022) on the survival of A. morticinus, but the effects of RH remains untested. This study examined the influence of RH on the survival and oviposition of A. morticinus inhabiting S. mauritianum inflorescences. Furthermore, this study also intended to reveal the influence of lethal humidities on A. santacruzi cultures compared to that of A. morticinus when sheltered by host inflorescences. Anthonomus morticinus colonies inhabiting S. mauritianum bouquets were kept at seven relative humidities, from ~80% to ~20% for a period of 14 days. Survival and oviposition, observed by dissection of buds, were recorded. For comparison, colonies of A. morticinus and A. santacruzi were maintained at 20% and 46% relative humidity for seven days to determine if the species had differing responses at the lower RH levels. A. morticinus survival and oviposition showed no significant differences at the decreasing humidity levels. Moreover, no significant differences were observed in the survival between A. morticinus and A. santacruzi at 46% and 20% RH. Weevils residing within the S. mauritianum flowers and shoots were shielded from the unfavourable environmental humidities owing to higher humidity levels within these microclimates. These results highlight the dependence of biological control agents on their hosts for more than just food and reproduction but also for physiological functionality.