Foraging in a dynamic environment: movement and stable isotope ecology of marine top predators breeding at the Prince Edward Archipelago
- Authors: Carpenter-Kling, Tegan
- Date: 2020
- Subjects: Marine ecology , Stable isotope tracers , Estuarine ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49049 , vital:41596
- Description: Marine ecosystems are experiencing rapid changes due to climate change. The associated temporal and spatial changes in resource distribution impacts on the foraging behaviour of marine top predators. If these changes negatively affect the ability of marine predators to forage efficiently, there may be dire consequences for their populations. However, evidence of foraging plasticity during adverse conditions, or generalist foraging behaviour, can allow inference about the resilience of species to environmental change and provide essential knowledge towards effective and proactive conservation measures. I examined plasticity in the trophic ecology of 12 marine predator species breeding on Marion Island, southern Indian Ocean, over three years (2015 – 2018), a period characterized by pronounced environmental variability. Firstly, I correlated behavioural states inferred along the GPS tracks of incubating wandering, grey-headed, sooty and light-mantled albatrosses to environmental variables that are indicative of biologically productive oceanographic features. Secondly, I analysed δ13C and δ15N blood values in 12 marine predator species (the afore-mentioned albatrosses as well as king, gentoo, macaroni and eastern rockhopper penguins, northern and southern giant petrels and Antarctic and sub-Antarctic fur seals) over two seasons: summer and autumn. My results revealed that the foraging behaviour of all the species is, to some degree, either plastic (temporally variable isotopic niche) or general (large isotopic niche which remained similar over time), except for the king penguin (small isotopic niche which remained similar over time), a known foraging specialist. Furthermore, despite their dynamic foraging behaviour, resource partitioning among the predators was maintained over time. Due to the ease and relatively low cost of collecting tissues for stable isotope analysis it has the potential to be a powerful tool to monitor the trophic ecology of marine predators. I thus used my simultaneously collected dataset of GPS tracks with the stable isotope blood compositions to investigate some of the assumptions underlying the inferences made from marine predator δ13C and δ15N blood values. I reconstructed species- and guild- specific δ13C and δ15N isoscapes for eight seabird species. Following this, I coupled individual-based movement models of northern giant petrels with global marine isotope models to explore the sensitivity of tissue δ13C values to a range of extrinsic (environmental) and intrinsic (behavioural, physiological) drivers. My results demonstrate the strong influence of reference isoscapes on the inference of stable isotope compositions of marine predators. Furthermore, I show that caution should be used when using non-species-specific or temporally inaccurate isoscapes. I furthermore demonstrate that biological interactions, such as competition for food resources, either past or present, as well as spatio-temporal distribution of food patches strongly influence the foraging behaviour of marine predators. These findings highlight the importance of integrating biological interactions in species distribution models which are used to predict possible distributional shifts of marine predators in the context of global changes. My thesis further developed previously available methods and presents a novel approach to investigate sources of variance in the stable isotopic composition of animals’ tissues.
- Full Text:
- Date Issued: 2020
- Authors: Carpenter-Kling, Tegan
- Date: 2020
- Subjects: Marine ecology , Stable isotope tracers , Estuarine ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49049 , vital:41596
- Description: Marine ecosystems are experiencing rapid changes due to climate change. The associated temporal and spatial changes in resource distribution impacts on the foraging behaviour of marine top predators. If these changes negatively affect the ability of marine predators to forage efficiently, there may be dire consequences for their populations. However, evidence of foraging plasticity during adverse conditions, or generalist foraging behaviour, can allow inference about the resilience of species to environmental change and provide essential knowledge towards effective and proactive conservation measures. I examined plasticity in the trophic ecology of 12 marine predator species breeding on Marion Island, southern Indian Ocean, over three years (2015 – 2018), a period characterized by pronounced environmental variability. Firstly, I correlated behavioural states inferred along the GPS tracks of incubating wandering, grey-headed, sooty and light-mantled albatrosses to environmental variables that are indicative of biologically productive oceanographic features. Secondly, I analysed δ13C and δ15N blood values in 12 marine predator species (the afore-mentioned albatrosses as well as king, gentoo, macaroni and eastern rockhopper penguins, northern and southern giant petrels and Antarctic and sub-Antarctic fur seals) over two seasons: summer and autumn. My results revealed that the foraging behaviour of all the species is, to some degree, either plastic (temporally variable isotopic niche) or general (large isotopic niche which remained similar over time), except for the king penguin (small isotopic niche which remained similar over time), a known foraging specialist. Furthermore, despite their dynamic foraging behaviour, resource partitioning among the predators was maintained over time. Due to the ease and relatively low cost of collecting tissues for stable isotope analysis it has the potential to be a powerful tool to monitor the trophic ecology of marine predators. I thus used my simultaneously collected dataset of GPS tracks with the stable isotope blood compositions to investigate some of the assumptions underlying the inferences made from marine predator δ13C and δ15N blood values. I reconstructed species- and guild- specific δ13C and δ15N isoscapes for eight seabird species. Following this, I coupled individual-based movement models of northern giant petrels with global marine isotope models to explore the sensitivity of tissue δ13C values to a range of extrinsic (environmental) and intrinsic (behavioural, physiological) drivers. My results demonstrate the strong influence of reference isoscapes on the inference of stable isotope compositions of marine predators. Furthermore, I show that caution should be used when using non-species-specific or temporally inaccurate isoscapes. I furthermore demonstrate that biological interactions, such as competition for food resources, either past or present, as well as spatio-temporal distribution of food patches strongly influence the foraging behaviour of marine predators. These findings highlight the importance of integrating biological interactions in species distribution models which are used to predict possible distributional shifts of marine predators in the context of global changes. My thesis further developed previously available methods and presents a novel approach to investigate sources of variance in the stable isotopic composition of animals’ tissues.
- Full Text:
- Date Issued: 2020
The nature of postgraduate student-supervisor relationship in the completion of doctoral studies in education: an exploration in two African universities
- Authors: Rugut, Cornelius Kipleting
- Date: 2018
- Subjects: Universities and colleges -- Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10948/17955 , vital:28545
- Description: Postgraduate supervision and particularly the student-supervisor relationship in doctoral studies has recently become a topic of great discussion in the academic arena. The relationship between the student and the supervisor is central to the successful completion of doctoral studies. Production of more PhDs in Africa is of great significance, seeing that there is a growing need for highly trained researchers to support the national social, economic and environmental goals of African countries. However, statistics show that the completion rate of doctoral studies in Africa is still very low. As such, the focus of this study was to explore the nature of the student-supervisor relationship in the completion of educational doctoral studies in two African universities, namely, Nelson Mandela University in South Africa and Moi University in Kenya. In order to answer the main research question: “What is the nature of the student-supervisor relationship as experienced by graduates who recently completed their educational doctoral studies in two African universities?” a qualitative approach was used, located within an interpretivist paradigm and positioned as an intrinsic interpretive case study. Convenient and purposive sampling was utilised to select participants who had recently completed their doctoral studies in education within the last five years. An individual semi-structured interview and drawings were used to generate the data with ten participants, five from each of the two Universities. The data was analysed thematically and the model for interpersonal supervisor behaviour of Mainhard, Roeland, Tarkwijk and Wubbels (2009), was used to make meaning of the findings. The findings were discussed under four areas, namely, expectations of the student-supervisor relationship, experiences of the student-supervisor relationship, negotiating the student-supervisor relationship and perceptions of the student-supervisor relationship in the successful completion of doctoral studies. These findings revealed that there were moments of cooperation or opposition, as well as instances of dominance or submission in the student-supervisor relationship. However, it appeared that negotiation was at the centre of the relationship, as it was evident that it strengthened the affiliation between the student and the supervisor and thus created a harmonious working relationship, while the lack of proper negotiation created discontent and opposition between the student and the supervisor. The conclusions from the findings were used to generate implications which could be helpful to university management in improving postgraduate supervision and in so doing, promote the success rate of doctoral studies in African universities.
- Full Text:
- Date Issued: 2018
- Authors: Rugut, Cornelius Kipleting
- Date: 2018
- Subjects: Universities and colleges -- Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10948/17955 , vital:28545
- Description: Postgraduate supervision and particularly the student-supervisor relationship in doctoral studies has recently become a topic of great discussion in the academic arena. The relationship between the student and the supervisor is central to the successful completion of doctoral studies. Production of more PhDs in Africa is of great significance, seeing that there is a growing need for highly trained researchers to support the national social, economic and environmental goals of African countries. However, statistics show that the completion rate of doctoral studies in Africa is still very low. As such, the focus of this study was to explore the nature of the student-supervisor relationship in the completion of educational doctoral studies in two African universities, namely, Nelson Mandela University in South Africa and Moi University in Kenya. In order to answer the main research question: “What is the nature of the student-supervisor relationship as experienced by graduates who recently completed their educational doctoral studies in two African universities?” a qualitative approach was used, located within an interpretivist paradigm and positioned as an intrinsic interpretive case study. Convenient and purposive sampling was utilised to select participants who had recently completed their doctoral studies in education within the last five years. An individual semi-structured interview and drawings were used to generate the data with ten participants, five from each of the two Universities. The data was analysed thematically and the model for interpersonal supervisor behaviour of Mainhard, Roeland, Tarkwijk and Wubbels (2009), was used to make meaning of the findings. The findings were discussed under four areas, namely, expectations of the student-supervisor relationship, experiences of the student-supervisor relationship, negotiating the student-supervisor relationship and perceptions of the student-supervisor relationship in the successful completion of doctoral studies. These findings revealed that there were moments of cooperation or opposition, as well as instances of dominance or submission in the student-supervisor relationship. However, it appeared that negotiation was at the centre of the relationship, as it was evident that it strengthened the affiliation between the student and the supervisor and thus created a harmonious working relationship, while the lack of proper negotiation created discontent and opposition between the student and the supervisor. The conclusions from the findings were used to generate implications which could be helpful to university management in improving postgraduate supervision and in so doing, promote the success rate of doctoral studies in African universities.
- Full Text:
- Date Issued: 2018
Freshwater invertebrate assemblages of the Eastern Cape Karoo region (South Africa) earmarked for shale gas exploration
- Authors: Mabidi, Annah
- Date: 2017
- Subjects: Invertebrates -- South Africa -- Karoo , Shale gas -- Conservation -- South Africa -- Karoo Freshwater animals -- South Africa -- Karoo Stream ecology -- South Africa -- Karoo
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/13713 , vital:27301
- Description: The Eastern Cape Karoo region is semi-arid with highly variable rainfall. This variability in rainfall sustains a mosaic of surface freshwater bodies that range from permanently to temporarily inundated. These waterbodies provide habitats for diverse invertebrate assemblages. The imminent hydraulic fracturing for shale gas has a potential to modify the water regime, with particular risk of salinisation. Accumulation of salts in freshwater wetlands results in loss of biodiversity, as invertebrate species shift from salt intolerant to salt tolerant species. This study therefore aims to expand on existing knowledge and provide new information on the distribution, diversity and structure of macroinvertebrate assemblages associated with various freshwater bodies in the region prior to shale gas exploration. Limnological and ecological aspects of thirty-three waterbodies (rivers, dams and depression wetlands) were investigated between November 2014 and March 2016. An experimental study on the effects of salinity on hatching success of branchiopod resting eggs was also included in the research. Rivers were characterised by high conductivity and depression wetlands by high turbidity, while dams had relatively higher pH than the other two waterbody types. In terms of global phosphorus interpretation guidelines, the results indicate that freshwater systems in the study region are predominantly eutrophic, indicating that agricultural run-off, particularly from livestock dung (goats, cattle and sheep), is an important source of phosphorus in the freshwater systems studied. Our results revealed new distribution records for branchiopod crustaceans in the Eastern Cape region, including the first record of Laevicaudata. Results showed that the sampled variables were unable to explain the variation in physicochemistry and invertebrate assemblage of several sites. Waterbody type, whether a depression wetland or a river, was the only factor that consistently showed an effect on the composition of both physicochemical data and invertebrate data. Depression wetlands ranged from completely bare to being extensively covered by macrophytes. Therefore, the effect of macrophyte cover in structuring macroinvertebrate assemblages was the focus of further investigation. The results indicated that the macrophyte cover gradient had little influence on the structure of the invertebrate assemblages in the depression wetlands, while only the presence/absence of vegetation significantly influenced the structure of the invertebrate assemblages in these systems. Surface area, dissolved inorganic nitrogen and pelagic chlorophyll-a were the environmental variables that best explained the variation in the macroinvertebrate assemblages among the sites. However, the differences in macroinvertebrate richness, abundance and distribution patterns among sites were only weakly influenced by local and regional environmental factors. These findings suggest that invertebrate in temporary wetland systems are adapted to the highly variable nature of temporary habitats, thus the influence of local variables is negligible. Results of the experimental study, on the effect of salinity on hatching success of branchiopod resting eggs, revealed that hatchling abundance and diversity of large branchiopods was significantly reduced at salinities of 2.5 g L−1 and above. Salt-tolerant taxa such as Copepoda and Ostracoda were the only ones to emerge in the highest salinity of 10 g L−1. Thus, should the region continue to experience increasing aridity and possible shale gas development, which all aggravate the salinisation problem, severe loss of branchiopod diversity (Anostraca, Laevicaudata, Spinicaudata and Notostraca) is likely to occur. This may lead to considerable decline in invertebrate diversity in the region, with cascading effects on food webs and ecosystem functions. The findings of this study can potentially be used in comparative studies on wetland invertebrate ecology in other semi-arid regions and in the formulation of policy and strategies for biodiversity conservation.
- Full Text:
- Date Issued: 2017
- Authors: Mabidi, Annah
- Date: 2017
- Subjects: Invertebrates -- South Africa -- Karoo , Shale gas -- Conservation -- South Africa -- Karoo Freshwater animals -- South Africa -- Karoo Stream ecology -- South Africa -- Karoo
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/13713 , vital:27301
- Description: The Eastern Cape Karoo region is semi-arid with highly variable rainfall. This variability in rainfall sustains a mosaic of surface freshwater bodies that range from permanently to temporarily inundated. These waterbodies provide habitats for diverse invertebrate assemblages. The imminent hydraulic fracturing for shale gas has a potential to modify the water regime, with particular risk of salinisation. Accumulation of salts in freshwater wetlands results in loss of biodiversity, as invertebrate species shift from salt intolerant to salt tolerant species. This study therefore aims to expand on existing knowledge and provide new information on the distribution, diversity and structure of macroinvertebrate assemblages associated with various freshwater bodies in the region prior to shale gas exploration. Limnological and ecological aspects of thirty-three waterbodies (rivers, dams and depression wetlands) were investigated between November 2014 and March 2016. An experimental study on the effects of salinity on hatching success of branchiopod resting eggs was also included in the research. Rivers were characterised by high conductivity and depression wetlands by high turbidity, while dams had relatively higher pH than the other two waterbody types. In terms of global phosphorus interpretation guidelines, the results indicate that freshwater systems in the study region are predominantly eutrophic, indicating that agricultural run-off, particularly from livestock dung (goats, cattle and sheep), is an important source of phosphorus in the freshwater systems studied. Our results revealed new distribution records for branchiopod crustaceans in the Eastern Cape region, including the first record of Laevicaudata. Results showed that the sampled variables were unable to explain the variation in physicochemistry and invertebrate assemblage of several sites. Waterbody type, whether a depression wetland or a river, was the only factor that consistently showed an effect on the composition of both physicochemical data and invertebrate data. Depression wetlands ranged from completely bare to being extensively covered by macrophytes. Therefore, the effect of macrophyte cover in structuring macroinvertebrate assemblages was the focus of further investigation. The results indicated that the macrophyte cover gradient had little influence on the structure of the invertebrate assemblages in the depression wetlands, while only the presence/absence of vegetation significantly influenced the structure of the invertebrate assemblages in these systems. Surface area, dissolved inorganic nitrogen and pelagic chlorophyll-a were the environmental variables that best explained the variation in the macroinvertebrate assemblages among the sites. However, the differences in macroinvertebrate richness, abundance and distribution patterns among sites were only weakly influenced by local and regional environmental factors. These findings suggest that invertebrate in temporary wetland systems are adapted to the highly variable nature of temporary habitats, thus the influence of local variables is negligible. Results of the experimental study, on the effect of salinity on hatching success of branchiopod resting eggs, revealed that hatchling abundance and diversity of large branchiopods was significantly reduced at salinities of 2.5 g L−1 and above. Salt-tolerant taxa such as Copepoda and Ostracoda were the only ones to emerge in the highest salinity of 10 g L−1. Thus, should the region continue to experience increasing aridity and possible shale gas development, which all aggravate the salinisation problem, severe loss of branchiopod diversity (Anostraca, Laevicaudata, Spinicaudata and Notostraca) is likely to occur. This may lead to considerable decline in invertebrate diversity in the region, with cascading effects on food webs and ecosystem functions. The findings of this study can potentially be used in comparative studies on wetland invertebrate ecology in other semi-arid regions and in the formulation of policy and strategies for biodiversity conservation.
- Full Text:
- Date Issued: 2017
A positive behaviour intervention approach to discipline at a primary school in Port Elizabeth
- Authors: Matthews, Thomas
- Date: 2016
- Subjects: School discipline -- South Africa -- Port Elizabeth Behavior modification
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10948/11564 , vital:26938
- Description: Learner discipline has become a major concern in South African schools. A society of entitlement has been bred over the past 20 years. The school is an open system that influences its environment and is being influenced by it too. The most challenging concern, at least for teachers, is to create and to maintain a form of order and structure at schools. The troublesome situation has an impact on teachers as they have to spend more time addressing challenging behaviour instead of spending that time on teaching a set curriculum and syllabus. Unfortunately, teachers report feelings of being ill-prepared to deal effectively with the challenging behaviour of learners in schools. Hence it is imperative to consider strategies to foster school discipline to manage and modify challenging behaviour in schools. To date, most researches have shown a major paradigm shift from the punitive disciplinary measures of the past towards a rather preventive and more positive approach. It became inevitable that learner discipline should be correctional and educational – especially after the abolishment of corporal punishment in South African schools. An increase attention has started to concentrate on early identification and prevention of challenging behaviour and on strategies to resolve such behaviour at its earliest appearance. Some of the guiding determinants for this positive approach are vested in maintaining a safe, harmonious and orderly environment that is conducive to teaching and learning. The outcry is to promote and encourage discipline amongst learners. An approach that has been termed school-wide positive behaviour intervention and support seems to address most of the challenging behaviours. Through the use of document analysis, observation and group interviews school-wide positive behaviour intervention and support was embraced. The findings further revealed that through proper planning, implementation strategies, and in-service training positive behaviour approach can be implemented in schools as framework for school discipline in primary schools. School-wide positive behaviour intervention and support will contribute successfully in managing and modifying challenging behaviour, fostering discipline in schools, and to educate learners in the habit of accountability and responsibility for their actions without using punishment following specified rules. Doing so some of the critical and developmental outcomes of education in South Africa will be realized. Although research in this area is limited, there are encouraging signs that a coordinated adoption of validated practice could substantially reduce challenging behaviours and thereby enhance the social and emotional well-being of learners in today’s society.
- Full Text:
- Date Issued: 2016
- Authors: Matthews, Thomas
- Date: 2016
- Subjects: School discipline -- South Africa -- Port Elizabeth Behavior modification
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10948/11564 , vital:26938
- Description: Learner discipline has become a major concern in South African schools. A society of entitlement has been bred over the past 20 years. The school is an open system that influences its environment and is being influenced by it too. The most challenging concern, at least for teachers, is to create and to maintain a form of order and structure at schools. The troublesome situation has an impact on teachers as they have to spend more time addressing challenging behaviour instead of spending that time on teaching a set curriculum and syllabus. Unfortunately, teachers report feelings of being ill-prepared to deal effectively with the challenging behaviour of learners in schools. Hence it is imperative to consider strategies to foster school discipline to manage and modify challenging behaviour in schools. To date, most researches have shown a major paradigm shift from the punitive disciplinary measures of the past towards a rather preventive and more positive approach. It became inevitable that learner discipline should be correctional and educational – especially after the abolishment of corporal punishment in South African schools. An increase attention has started to concentrate on early identification and prevention of challenging behaviour and on strategies to resolve such behaviour at its earliest appearance. Some of the guiding determinants for this positive approach are vested in maintaining a safe, harmonious and orderly environment that is conducive to teaching and learning. The outcry is to promote and encourage discipline amongst learners. An approach that has been termed school-wide positive behaviour intervention and support seems to address most of the challenging behaviours. Through the use of document analysis, observation and group interviews school-wide positive behaviour intervention and support was embraced. The findings further revealed that through proper planning, implementation strategies, and in-service training positive behaviour approach can be implemented in schools as framework for school discipline in primary schools. School-wide positive behaviour intervention and support will contribute successfully in managing and modifying challenging behaviour, fostering discipline in schools, and to educate learners in the habit of accountability and responsibility for their actions without using punishment following specified rules. Doing so some of the critical and developmental outcomes of education in South Africa will be realized. Although research in this area is limited, there are encouraging signs that a coordinated adoption of validated practice could substantially reduce challenging behaviours and thereby enhance the social and emotional well-being of learners in today’s society.
- Full Text:
- Date Issued: 2016
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