Electronic Theses and Dissertations (PhDs)

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Browsing Electronic Theses and Dissertations (PhDs) by SDG "SDG-4: Quality education"

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    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.
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    Farming systems in South Africa beyond 2020: a scenario-based study, using systems analysis, of the connectivity between farming systems in the Vhembe district, Limpopo, South Africa
    (University of the Witwatersrand, Johannesburg, 2024) Materechera-Mitochi, Fenji; Scholes, Mary
    Agriculture is a significant contributor to the South African economy and overall development as it contributes to poverty reduction and food security. It is against this backdrop that agricultural development becomes a focus area for decision making amongst stakeholders, as it is directly linked to food systems. The traditional approach to agricultural production in the country has been one that views farming as mainly based on land ownership and yield in isolation from the broader context of the four drivers of production namely land, labour, capital and enterprise. The concept of farming systems provides a broader perspective on farming and encompasses the entire value chain for a commodity which includes production, management practices, marketing, value addition, financial resources, and policies. The South African agrarian structure is characterised by a dualism in which large-scale commercial farmers co-exist alongside small-scale farmers. This is a legacy of the apartheid system of governance. Large-scale commercial farmers, who are mostly capital intensive, have historically been regarded as the main drivers of national food security while small-scale farmers on the other hand are viewed as significant contributors to food security at a household level. Both farmers are therefore important contributors to the national agricultural economy. Research on the two types of farmers in the South African context is usually focused on the respective farmers’ approaches to production individually and does not consider them as joint ventures. This study was aimed at providing an alternative approach to viewing South Africa’s farming systems by evaluating current farming systems in the Vhembe district of Limpopo, South Africa, using systems analysis as a tool to highlight the connectivity of the interactions within and between them. The study also aimed to conceptualize scenarios for sustainable future farming systems in South Africa. The Vhembe district in the Limpopo province was chosen for the study because both largescale commercial and small-scale farmers occur and due to the favourable sub-tropical climate, the area has become a hub for the farming of numerous high value crops that contribute positively to the country’s agricultural economy. The study made use of a mixed methods approach that combined the analysis of primary data obtained from in-depth interviews and secondary data obtained from an agricultural database to identify and characterize large-scale commercial and small-scale farming systems in the Vhembe district. The study examined the drivers of production for three different commodities, macadamia nuts, mangos and avocado iii pears, the two types of farming systems and their connectivity. The study was grounded on the conceptual framework of systems thinking and used a systems analysis tool i.e., causal loop diagrams to analyse the connectivity between the two farming systems. Lastly, the study developed conceptual scenarios using a deductive scenario method to conceptualise scenarios for the future of the two farming systems and the different commodities. Key findings of the study showed that farming systems need to be understood through the lens of the four drivers of production. Land as a driver of production interacts with multiple other factors in shaping the management of a sustainable farming system. Examples of these factors include the link between land availability, ownership and farm size, decision-making and resource allocation tied to land management practices, and socio-economic considerations including the diversification of livelihoods by incorporating non-farm income and the farmers’ adaptability to uncertainties such as climate change. The findings also revealed that there are interconnections between the two types of farming systems presenting potential for enhanced production and commercial opportunities. The conceptual scenarios developed in the study and the systems thinking tool of causal loop diagrams proved to be valuable tools to inform decision making and policy development. The study’s main conclusion points to the potential of large-scale commercial and small-scale farming systems in South Africa operating as joint ventures in the future and enhancing the sustainability of agricultural production and livelihoods. It also recommends the use of systems thinking that includes social, financial and environmental values and impacts in decision making for agricultural development.
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    Unravelling the speciation process in barking geckos (Ptenopus: Gekkonidae)
    (University of the Witwatersrand, Johannesburg, 2024) Becker, Francois S.; Tolley, Krystal A.; Graham J. Alexander
    Barking geckos (genus Ptenopus) are a group of terrestrial, burrowing lizards endemic to southern Africa, with three currently recognised species: P. kochi, P. carpi, and P. garrulus, the last containing the subspecies P. g. garrulus and P. g. maculatus. Males produce uniquely loud vocalisations to attract females to the burrows, a trait which is involved in mate recognition. I produced the first comprehensive phylogeny for the genus, which supported several deep divergences and the presence of unrecognised species. I then applied the unified species concept in an integrated taxonomic framework to delimit species within Ptenopus. I used multiple lines of evidence including genetic-spatial analyses, advertisement calls, ecological divergence, and morphology to test the evolutionary independence of putative species suggested by phylogenetic species delimitation analyses. Based on these findings, I suggest there is a total of eight species of Ptenopus, and that the two subspecies P. g. garrulus and P. g. maculatus should be elevated to full species. I provide provisional descriptions of four additional species. The advertisement calls and preferred habitats were clearly distinct among these proposed species, while morphological characters were generally less reliable for species identification. I also tested various candidate hypotheses of divergence drivers in the genus using multiple regression on matrix models (MRMs). The MRMs supported the hypothesis that substrate specialisation was the main factor over other factors as the key driver of divergence. Geographic barriers, including rivers and mountains or ridges, also appear to be important drivers of some of the more the recent divergences. The Namib Desert is the centre of diversity for the genus Ptenopus, containing seven of the eight proposed species. There was also strong evidence for reproductive character displacement in the advertisement calls of sympatric species, indicating the importance of calls in mate recognition and the maintenance of species boundaries. This is the first study to show evidence for reproductive character displacement of vocal traits in a non-avian reptile.