Investigating the fitness of sea turtles nesting in South Africa
- Le Gouvello du Timat, Diane Z M
- Authors: Le Gouvello du Timat, Diane Z M
- Date: 2020
- Subjects: Sea turtles -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48445 , vital:40877
- Description: The South African rookeries of the South Western Indian Ocean (SWIO) loggerhead and leatherback regional management units have been continuously monitored for more than 5 decades, representing one of the longest-running sea turtle beach protection and monitoring programmes in the world. Although such conservation has been successful in protecting adults on land when they come to nest, it might not be enough to ensure population recovery if survival is not ensured across all life stages. Sea turtles are particularly vulnerable to direct threats and changing environmental conditions because they are long-lived, slow maturing, and have low survival rates at early life stages, making them conservation-dependent. These characteristics also render them difficult to conserve as a consequence of their wide geographic distributions, spanning multiple jurisdictions and legislative systems with different conservation targets, and a complex life cycle with changes in habitats and diets at different life stages. Sea turtle populations have been severely depleted as a result of historical over-exploitation and current threats including fisheries bycatch, direct harvest, habitat loss, pollution and pathogens, and climate change. In many cases however, population declines have been reversed by a variety of effective conservation measures such as beach protection programs, and marine protected areas, enabling successful population recovery around the world. Despite protection and apparent increase in abundance, indirect pressures can still affect turtle populations. Therefore, it is fundamental to evaluate the effectiveness of conservation measures (using fitness traits such as female and hatchling sizes) and examine underlying trends. The aim of this thesis was thus to evaluate the fitness of loggerhead and leatherback sea turtles nesting in South Africa. Long-term female size trends over time were evaluated and the populations were split between first-time nesters and experienced nesters. As sea turtle reproductive output (clutch size only) is correlated with female size and evidence is showing that in some populations individual female size is decreasing, the effects of maternal body size on reproductive output and hatchling fitness were investigated for both species. Crawling and swimming speeds were used as proxies of hatchling fitness, because these two traits positively influence their survival. An oceanic model was further used in combination with a particle tracking framework to estimate, for the first time, post-hatchling dispersal of loggerhead and leatherback turtles in the SWIO. I investigated whether the trend in female size for loggerhead turtles nesting in South Africa is a result of their foraging strategy to determine if there is a foraging dichotomy (neritic and oceanic). Despite an apparent increasing population, a significant 3.7 and 3.6 cm decrease in the size of both recruit and remingrant female loggerhead turtles, but a stable mean size of leatherbacks for both age groups was observed. I hypothesise that these contradictory effects are attributable to the very distinct foraging ecologies of the two turtle species and speculate that these variations in carapace length may be driven by environmental change. The reproductive strategy of both loggerhead and leatherback turtles nesting in South Africa supports the optimal egg size theory with larger turtles producing larger clutches but not larger eggs. Egg size was thus constant irrespective of maternal length. Hatchlings with longer carapaces and flippers had higher swimming speed, suggesting that larger hatchlings are fitter (potentially higher survival) than smaller ones by spending less time in high predation risk areas (i.e. beach and nearshore). The model revealed that dispersal trajectories of both loggerhead and leatherback sea turtle hatchlings were very similar and simulations indicated that initial active swimming (frenzy) as well as variability in oceanic conditions strongly influenced dispersal of virtual hatchlings. The trends observed in this study emphasize the importance of long-term monitoring, examining not only abundance but also individual size, to understand population dynamics, support recovery planning and prioritize future conservation practices. Furthermore, the findings of this study have important implications for overall population growth if smaller hatchlings of lower fitness are produced as a result of climate change and thus have decreased dispersal abilities and lower likelihood of survival.
- Full Text:
- Date Issued: 2020
- Authors: Le Gouvello du Timat, Diane Z M
- Date: 2020
- Subjects: Sea turtles -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48445 , vital:40877
- Description: The South African rookeries of the South Western Indian Ocean (SWIO) loggerhead and leatherback regional management units have been continuously monitored for more than 5 decades, representing one of the longest-running sea turtle beach protection and monitoring programmes in the world. Although such conservation has been successful in protecting adults on land when they come to nest, it might not be enough to ensure population recovery if survival is not ensured across all life stages. Sea turtles are particularly vulnerable to direct threats and changing environmental conditions because they are long-lived, slow maturing, and have low survival rates at early life stages, making them conservation-dependent. These characteristics also render them difficult to conserve as a consequence of their wide geographic distributions, spanning multiple jurisdictions and legislative systems with different conservation targets, and a complex life cycle with changes in habitats and diets at different life stages. Sea turtle populations have been severely depleted as a result of historical over-exploitation and current threats including fisheries bycatch, direct harvest, habitat loss, pollution and pathogens, and climate change. In many cases however, population declines have been reversed by a variety of effective conservation measures such as beach protection programs, and marine protected areas, enabling successful population recovery around the world. Despite protection and apparent increase in abundance, indirect pressures can still affect turtle populations. Therefore, it is fundamental to evaluate the effectiveness of conservation measures (using fitness traits such as female and hatchling sizes) and examine underlying trends. The aim of this thesis was thus to evaluate the fitness of loggerhead and leatherback sea turtles nesting in South Africa. Long-term female size trends over time were evaluated and the populations were split between first-time nesters and experienced nesters. As sea turtle reproductive output (clutch size only) is correlated with female size and evidence is showing that in some populations individual female size is decreasing, the effects of maternal body size on reproductive output and hatchling fitness were investigated for both species. Crawling and swimming speeds were used as proxies of hatchling fitness, because these two traits positively influence their survival. An oceanic model was further used in combination with a particle tracking framework to estimate, for the first time, post-hatchling dispersal of loggerhead and leatherback turtles in the SWIO. I investigated whether the trend in female size for loggerhead turtles nesting in South Africa is a result of their foraging strategy to determine if there is a foraging dichotomy (neritic and oceanic). Despite an apparent increasing population, a significant 3.7 and 3.6 cm decrease in the size of both recruit and remingrant female loggerhead turtles, but a stable mean size of leatherbacks for both age groups was observed. I hypothesise that these contradictory effects are attributable to the very distinct foraging ecologies of the two turtle species and speculate that these variations in carapace length may be driven by environmental change. The reproductive strategy of both loggerhead and leatherback turtles nesting in South Africa supports the optimal egg size theory with larger turtles producing larger clutches but not larger eggs. Egg size was thus constant irrespective of maternal length. Hatchlings with longer carapaces and flippers had higher swimming speed, suggesting that larger hatchlings are fitter (potentially higher survival) than smaller ones by spending less time in high predation risk areas (i.e. beach and nearshore). The model revealed that dispersal trajectories of both loggerhead and leatherback sea turtle hatchlings were very similar and simulations indicated that initial active swimming (frenzy) as well as variability in oceanic conditions strongly influenced dispersal of virtual hatchlings. The trends observed in this study emphasize the importance of long-term monitoring, examining not only abundance but also individual size, to understand population dynamics, support recovery planning and prioritize future conservation practices. Furthermore, the findings of this study have important implications for overall population growth if smaller hatchlings of lower fitness are produced as a result of climate change and thus have decreased dispersal abilities and lower likelihood of survival.
- Full Text:
- Date Issued: 2020
Implementation of safety measures in selected public high schools in the Alfred Nzo East education district
- Authors: Mditshwa, Simbongile
- Date: 2020
- Subjects: Schools -- Security measures School safety and security
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10353/17895 , vital:41975
- Description: The main aim of the study was to find out how safety measures are implemented in selected public high schools in the Alfred Nzo East Education District. The study was motivated by multiple media reports about incidents that have to do with the safety of learners especially in rural public schools. This case study was grounded in the interpretive paradigm and the qualitative approach was adopted. The study was theoretically guided by the principles from both the Street-Level Bureaucracy (SLB) and the Rational Decision Making Model (RDMM). The data was collected from three schools in the Alfred Nzo East Education District, Eastern Cape, RSA. A purposive sampling technique was utilized to choose the research participants. A total of 21 human participants were involved in interviews where two teachers per school, two learners per school, two SGB parents and a principal were interviewed. Interviews were supplemented with short observations and document analysis. The findings of the research include the following: educators get a minimal empowerment to manage school safety in terms of access to school, scholar transport and on. The researched schools had no school-based safety policies. Some of the challenges included the level of roadworthiness of the vehicles that are used to transport school children which exposes learners to a high risk and that puts more pressure on school safety. Drugs and dangerous weapons are other factors which contribute to the instability of school safety. The researcher recommended that educators should be empowered through support from the principals and from the district coordinator through frequent policy implementation conference using online platform to minimize the costs of physical conferences. I recommended that the community must be active whistle-blowers for drug smuggling because drugs in schools emanate from the communities. Indemnity forms, release forms and school-based policies must be made available for implementation and referencing purposes. Schools should establish healthy relationship with external stakeholders like traditional leaders, SAPS and the Department of Social Development to curb lack of safety in schools.
- Full Text:
- Date Issued: 2020
- Authors: Mditshwa, Simbongile
- Date: 2020
- Subjects: Schools -- Security measures School safety and security
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10353/17895 , vital:41975
- Description: The main aim of the study was to find out how safety measures are implemented in selected public high schools in the Alfred Nzo East Education District. The study was motivated by multiple media reports about incidents that have to do with the safety of learners especially in rural public schools. This case study was grounded in the interpretive paradigm and the qualitative approach was adopted. The study was theoretically guided by the principles from both the Street-Level Bureaucracy (SLB) and the Rational Decision Making Model (RDMM). The data was collected from three schools in the Alfred Nzo East Education District, Eastern Cape, RSA. A purposive sampling technique was utilized to choose the research participants. A total of 21 human participants were involved in interviews where two teachers per school, two learners per school, two SGB parents and a principal were interviewed. Interviews were supplemented with short observations and document analysis. The findings of the research include the following: educators get a minimal empowerment to manage school safety in terms of access to school, scholar transport and on. The researched schools had no school-based safety policies. Some of the challenges included the level of roadworthiness of the vehicles that are used to transport school children which exposes learners to a high risk and that puts more pressure on school safety. Drugs and dangerous weapons are other factors which contribute to the instability of school safety. The researcher recommended that educators should be empowered through support from the principals and from the district coordinator through frequent policy implementation conference using online platform to minimize the costs of physical conferences. I recommended that the community must be active whistle-blowers for drug smuggling because drugs in schools emanate from the communities. Indemnity forms, release forms and school-based policies must be made available for implementation and referencing purposes. Schools should establish healthy relationship with external stakeholders like traditional leaders, SAPS and the Department of Social Development to curb lack of safety in schools.
- Full Text:
- Date Issued: 2020
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