Factors affecting pinniped skull morphology
- Authors: Penaluna, Julia Elizabeth
- Date: 2023-04
- Subjects: hybridisation -- South Africa , Sexual dimorphism (Animals) , Craniology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61306 , vital:70077
- Description: Morphologies have evolved due to trade-offs between competing selective pressures. This is especially true for the skull. Not only does it contain the brain and the organs that are responsible for sensory function, but it is also contains components that play important roles in feeding, breathing, balance, defence, aggression and communication. The pinnipeds, a group of species that has evolved from terrestrial origins and became adapted to the marine environment, are under numerous selective pressures within the marine environment. These species have had to evolve in order to capture and process food underwater, and to dive. In addition, they are also characterised by substantial sexual size dimorphism in some species. Pinnipeds also make use of numerous marine and haul-out habitats with varying characteristics and complexity. Hybridisation has been recorded among pinnipeds, resulting in the production of hybrid offspring with characteristics that are different to their parent species. The aim of the study was to investigate the effect of these life history characteristics on skull and mandible morphology of pinniped species using three dimensional geometric morphometrics. To achieve this, 43 skull and 15 mandible 3D landmarks were collected using a Microscribe G2X digitizer with 0.2mm accuracy, on the skull and mandibles of 17 species of pinnipeds across three families, and one hybrid species. In total, 96 specimens across these species were examined. Data on the different life history characteristics of each species were collected from the literature. These data were plotted onto the PCA results in order to create and visually compare minimum convex polygons for each life history category. The results found that phylogeny, feeding strategy and sexual dimorphism were the most important factors in explaining differences in pinniped skull and mandible shape and size. may have resulted in these changes. Similarly, the inclusion of more species, covering a broader range of life histories may be beneficial. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Penaluna, Julia Elizabeth
- Date: 2023-04
- Subjects: hybridisation -- South Africa , Sexual dimorphism (Animals) , Craniology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61306 , vital:70077
- Description: Morphologies have evolved due to trade-offs between competing selective pressures. This is especially true for the skull. Not only does it contain the brain and the organs that are responsible for sensory function, but it is also contains components that play important roles in feeding, breathing, balance, defence, aggression and communication. The pinnipeds, a group of species that has evolved from terrestrial origins and became adapted to the marine environment, are under numerous selective pressures within the marine environment. These species have had to evolve in order to capture and process food underwater, and to dive. In addition, they are also characterised by substantial sexual size dimorphism in some species. Pinnipeds also make use of numerous marine and haul-out habitats with varying characteristics and complexity. Hybridisation has been recorded among pinnipeds, resulting in the production of hybrid offspring with characteristics that are different to their parent species. The aim of the study was to investigate the effect of these life history characteristics on skull and mandible morphology of pinniped species using three dimensional geometric morphometrics. To achieve this, 43 skull and 15 mandible 3D landmarks were collected using a Microscribe G2X digitizer with 0.2mm accuracy, on the skull and mandibles of 17 species of pinnipeds across three families, and one hybrid species. In total, 96 specimens across these species were examined. Data on the different life history characteristics of each species were collected from the literature. These data were plotted onto the PCA results in order to create and visually compare minimum convex polygons for each life history category. The results found that phylogeny, feeding strategy and sexual dimorphism were the most important factors in explaining differences in pinniped skull and mandible shape and size. may have resulted in these changes. Similarly, the inclusion of more species, covering a broader range of life histories may be beneficial. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Foraging behaviour and thermal physiology of Cape sugarbirds: sex-specific responses to temperature
- Authors: Molepo, Mokgatla Jerry
- Date: 2017
- Subjects: Sexual dimorphism (Animals) , Sex differences Birds -- Behavior
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/19124 , vital:28775
- Description: Body size (Mb) determines an animal’s energy and water demands for thermoregulation. Sexual dimorphism in Mb is common across many species, but its physiological consequences (e.g. energy and water demands) remain poorly understood. In this study, I determined if the sexually dimorphic Cape Sugarbird (Promerops cafer)–males are up to 15% larger than females, show sex-specific foraging patterns and physiological responses. To determine intraspecific variability behavioural in response to temperature, I compared flower visitation rates between male and female Cape Sugarbirds at different times of the day, and among days that varied in maximum air temperature. A total of 1207 males and 561 females were observed. Female Cape Sugarbirds visited flowers more often and continued to feed especially on hot days. Males generally dominated flower resources throughout the day, except on hot days. I also compared physiological responses in EWL, RMR and Tb between males and females at high air temperatures. There were no significant differences between the two sexes. Aggression which was overlooked appeared to have a high influence on foraging behaviour of Cape Sugarbirds. These results suggest that female Cape Sugarbirds will be more prone to energy and water stress during hot and dry summers in the Fynbos region because of resource dominance by male Cape Sugarbirds. Endemic birds, such as the Cape Sugarbird, warrant a conservation priority, especially since they are the dominant pollinator of the Protea plants in the Fynbos biome. The findings of this study will provide insights into population persistence of Cape Sugarbirds in response to predicted heat waves and rise in global temperatures.
- Full Text:
- Date Issued: 2017
- Authors: Molepo, Mokgatla Jerry
- Date: 2017
- Subjects: Sexual dimorphism (Animals) , Sex differences Birds -- Behavior
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/19124 , vital:28775
- Description: Body size (Mb) determines an animal’s energy and water demands for thermoregulation. Sexual dimorphism in Mb is common across many species, but its physiological consequences (e.g. energy and water demands) remain poorly understood. In this study, I determined if the sexually dimorphic Cape Sugarbird (Promerops cafer)–males are up to 15% larger than females, show sex-specific foraging patterns and physiological responses. To determine intraspecific variability behavioural in response to temperature, I compared flower visitation rates between male and female Cape Sugarbirds at different times of the day, and among days that varied in maximum air temperature. A total of 1207 males and 561 females were observed. Female Cape Sugarbirds visited flowers more often and continued to feed especially on hot days. Males generally dominated flower resources throughout the day, except on hot days. I also compared physiological responses in EWL, RMR and Tb between males and females at high air temperatures. There were no significant differences between the two sexes. Aggression which was overlooked appeared to have a high influence on foraging behaviour of Cape Sugarbirds. These results suggest that female Cape Sugarbirds will be more prone to energy and water stress during hot and dry summers in the Fynbos region because of resource dominance by male Cape Sugarbirds. Endemic birds, such as the Cape Sugarbird, warrant a conservation priority, especially since they are the dominant pollinator of the Protea plants in the Fynbos biome. The findings of this study will provide insights into population persistence of Cape Sugarbirds in response to predicted heat waves and rise in global temperatures.
- Full Text:
- Date Issued: 2017
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