The diet and ecological role of black-backed jackals, Canis Mesomelas, in two conservation areas in the Eastern Cape Province, South Africa
- Authors: Brassine, Mathilde Chloé
- Date: 2012
- Subjects: Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Wildlife conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5660 , http://hdl.handle.net/10962/d1005344 , Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Wildlife conservation
- Description: Mammalian predators are keystone species and can have disproportionately large impacts, relative to their abundance, on the communities and ecosystems they inhabit. In addition, predator-prey interactions (including bottom-up and top-down effects) are the fundamental linkage among species in food webs. Thus, understanding the food requirements of predators is imperative. There have been no comprehensive studies on the diet of black-backed jackals (Canis mesomelas) across a full seasonal cycle in the Albany Thicket Biome of the Eastern Cape Province. This biome is rich in plant diversity, is highly nutritious for herbivores and supports a large number of mammalian species, yet it is poorly conserved. The aim of the present study was to establish the diet of black-backed jackals on two conservation areas where thicket vegetation dominates (Great Fish River Reserve and Kwandwe Private Game Reserve). The diet was assessed using scats collected monthly from June 2009 to May 2010 and a sample of 25 stomachs over the same period. At both sites and across all seasons, mammalian hair was encountered most often (93% of all scats) and a total of 23 mammal species were consumed. Of the mammals recorded in the scats, hair from several ungulate species was encountered most frequently and these were mostly hider species (offspring hidden in tall vegetation just after birth). On a seasonal basis, the proportion of mammalian hair was lowest in autumn. However, the contribution of fruits (Carissa haematocarpa, Diospyros lycioides and Grewia robusta) to the diet was significantly higher during this season. This suggests that black-backed jackals may employ diet switching in the Eastern Cape as a mechanism to capitalise on seasonally abundant food sources. Based on the stomach content analysis, invertebrates were consumed as frequently as mammalian prey throughout the year but mammalian prey was recorded in greater quantity (i.e. volume and mass). Thus, scat analysis may have overestimated mammalian prey and fruits and underestimated the importance of invertebrates, particularly highly digestible species (e.g. termites). In spite of these differences, scat analysis demonstrated similar general and seasonal trends as the stomach content analysis. Thus, scat analysis can provide an efficient and relatively accurate source of information on the diet of blackbacked jackals in the Eastern Cape. Both stomach content and scat collection methods depicted the black-backed jackal as a generalist and opportunistic predator, mainly relying on mammals and invertebrates. Although the results of my study suggest that black-backed jackal may be important predators of certain ungulate species, further study on their prey preferences, actual biomass ingested and the effects on the population viability of prey species is required in order to develop a robust management plan for the species in the protected areas of the Eastern Cape.
- Full Text:
- Date Issued: 2012
- Authors: Brassine, Mathilde Chloé
- Date: 2012
- Subjects: Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Wildlife conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5660 , http://hdl.handle.net/10962/d1005344 , Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Wildlife conservation
- Description: Mammalian predators are keystone species and can have disproportionately large impacts, relative to their abundance, on the communities and ecosystems they inhabit. In addition, predator-prey interactions (including bottom-up and top-down effects) are the fundamental linkage among species in food webs. Thus, understanding the food requirements of predators is imperative. There have been no comprehensive studies on the diet of black-backed jackals (Canis mesomelas) across a full seasonal cycle in the Albany Thicket Biome of the Eastern Cape Province. This biome is rich in plant diversity, is highly nutritious for herbivores and supports a large number of mammalian species, yet it is poorly conserved. The aim of the present study was to establish the diet of black-backed jackals on two conservation areas where thicket vegetation dominates (Great Fish River Reserve and Kwandwe Private Game Reserve). The diet was assessed using scats collected monthly from June 2009 to May 2010 and a sample of 25 stomachs over the same period. At both sites and across all seasons, mammalian hair was encountered most often (93% of all scats) and a total of 23 mammal species were consumed. Of the mammals recorded in the scats, hair from several ungulate species was encountered most frequently and these were mostly hider species (offspring hidden in tall vegetation just after birth). On a seasonal basis, the proportion of mammalian hair was lowest in autumn. However, the contribution of fruits (Carissa haematocarpa, Diospyros lycioides and Grewia robusta) to the diet was significantly higher during this season. This suggests that black-backed jackals may employ diet switching in the Eastern Cape as a mechanism to capitalise on seasonally abundant food sources. Based on the stomach content analysis, invertebrates were consumed as frequently as mammalian prey throughout the year but mammalian prey was recorded in greater quantity (i.e. volume and mass). Thus, scat analysis may have overestimated mammalian prey and fruits and underestimated the importance of invertebrates, particularly highly digestible species (e.g. termites). In spite of these differences, scat analysis demonstrated similar general and seasonal trends as the stomach content analysis. Thus, scat analysis can provide an efficient and relatively accurate source of information on the diet of blackbacked jackals in the Eastern Cape. Both stomach content and scat collection methods depicted the black-backed jackal as a generalist and opportunistic predator, mainly relying on mammals and invertebrates. Although the results of my study suggest that black-backed jackal may be important predators of certain ungulate species, further study on their prey preferences, actual biomass ingested and the effects on the population viability of prey species is required in order to develop a robust management plan for the species in the protected areas of the Eastern Cape.
- Full Text:
- Date Issued: 2012
Changes in diet resource use by elephants, Loxodonta Africana, due to changes in resource availability in the Addo National Park
- Authors: Du Toit, Jana
- Date: 2015
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape , Wildlife conservation , Addo Elephant National Park (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10731 , ISSN http://hdl.handle.net/10948/d1021194
- Description: Animals are restricted in their diets by several factors, most notably the availability and quality of resources. Variation in resource availability causes herbivores to shift their diets seasonally and spatially. Elephants (Loxodonta africana), are known to have extensive impacts on plant communities, altering ecosystem functioning and causing a decline in biodiversity. In enclosed areas, these impacts are increased leading to a decline in resource availability and presumably resource quality. In the Addo Elephant National Park, the Main Camp section has a history of high elephant impacts and therefore reduced resource availability. Whereas, the recently added Colchester section has greater resource availability, due to the absence of elephants in this section since the fencing of the Park. This study investigated the changes in diet (diet breadth, preference and diet quality) of elephants due to an increase in resource availability. Three alternative hypotheses were contrasted: 1) elephants as generalist foragers, 2) elephants as optimal foragers, or 3) elephants learning foraging behaviour. Using microhistological analysis, the diets of elephants were described over five sampling periods (August 2010 – February 2014) in both sections. Forage availability was estimated using a modified line-intercept method, and was used to determine changes in preference by relating forage availability to use. In the Colchester section the diet breadth of elephants increased, and was coupled with a high initial variation between the diets of elephants, which decreased in subsequent sampling periods. This supported the elephants learning foraging behaviour hypothesis. However, there was no increase in diet preference by elephants in the Colchester section, which supported the elephants as generalist foragers hypothesis. There was also no difference in the diet quality of elephants in the Main Camp and Colchester sections, which did not support any of the three hypotheses. The elephants learning foraging behaviour hypothesis is proposed to be the link between the alternate two hypotheses, and given enough time, either of the two could be supported. The lack of difference in preference and diet quality between elephants in the Main Camp and Colchester sections is hypothesised to be due to the population level (not measured for individuals) at which these were measured. Microhistological analysis of faeces was used to describe the diet of elephants, which was compared to the diet described by DNA metabarcoding. Microhistological analysis is a traditional, favoured technique used in describing the diet of wild herbivores, whereas DNA metabarcoding is a relatively new and untested technique. These two techniques have not yet been compared in the diet of megaherbivores. Results indicated that microhistological analysis identified significantly more grass in the diet of elephants, than DNA metabarcoding did, which was expected as previous studies also found overestimation of grasses. Microhistological analysis identified more plant families in the diet of elephants, than DNA metabarcoding. Most of the differences between the two techniques can be attributed to the difference in taxonomic resolution, which was due to the lack of a complete reference collection for DNA metabarcoding. Although either of the two techniques can be used to describe the diet of elephants, the most reliable results would be obtained when using both techniques. The findings of this study suggest that due to the high initial variation between the diets of elephants, with an increase in resource availability, the impacts will also initially be highly varied. This suggests that identifying plant species to monitor elephants impacts initially will be difficult. However, important plant species, or those known to be vulnerable to elephants impacts should be carefully monitored initially and monitoring should not only occur annually, but also seasonally.
- Full Text:
- Date Issued: 2015
- Authors: Du Toit, Jana
- Date: 2015
- Subjects: Elephants -- Nutrition -- South Africa -- Eastern Cape , Elephants -- Habitat -- South Africa -- Eastern Cape , Wildlife conservation , Addo Elephant National Park (South Africa)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10731 , ISSN http://hdl.handle.net/10948/d1021194
- Description: Animals are restricted in their diets by several factors, most notably the availability and quality of resources. Variation in resource availability causes herbivores to shift their diets seasonally and spatially. Elephants (Loxodonta africana), are known to have extensive impacts on plant communities, altering ecosystem functioning and causing a decline in biodiversity. In enclosed areas, these impacts are increased leading to a decline in resource availability and presumably resource quality. In the Addo Elephant National Park, the Main Camp section has a history of high elephant impacts and therefore reduced resource availability. Whereas, the recently added Colchester section has greater resource availability, due to the absence of elephants in this section since the fencing of the Park. This study investigated the changes in diet (diet breadth, preference and diet quality) of elephants due to an increase in resource availability. Three alternative hypotheses were contrasted: 1) elephants as generalist foragers, 2) elephants as optimal foragers, or 3) elephants learning foraging behaviour. Using microhistological analysis, the diets of elephants were described over five sampling periods (August 2010 – February 2014) in both sections. Forage availability was estimated using a modified line-intercept method, and was used to determine changes in preference by relating forage availability to use. In the Colchester section the diet breadth of elephants increased, and was coupled with a high initial variation between the diets of elephants, which decreased in subsequent sampling periods. This supported the elephants learning foraging behaviour hypothesis. However, there was no increase in diet preference by elephants in the Colchester section, which supported the elephants as generalist foragers hypothesis. There was also no difference in the diet quality of elephants in the Main Camp and Colchester sections, which did not support any of the three hypotheses. The elephants learning foraging behaviour hypothesis is proposed to be the link between the alternate two hypotheses, and given enough time, either of the two could be supported. The lack of difference in preference and diet quality between elephants in the Main Camp and Colchester sections is hypothesised to be due to the population level (not measured for individuals) at which these were measured. Microhistological analysis of faeces was used to describe the diet of elephants, which was compared to the diet described by DNA metabarcoding. Microhistological analysis is a traditional, favoured technique used in describing the diet of wild herbivores, whereas DNA metabarcoding is a relatively new and untested technique. These two techniques have not yet been compared in the diet of megaherbivores. Results indicated that microhistological analysis identified significantly more grass in the diet of elephants, than DNA metabarcoding did, which was expected as previous studies also found overestimation of grasses. Microhistological analysis identified more plant families in the diet of elephants, than DNA metabarcoding. Most of the differences between the two techniques can be attributed to the difference in taxonomic resolution, which was due to the lack of a complete reference collection for DNA metabarcoding. Although either of the two techniques can be used to describe the diet of elephants, the most reliable results would be obtained when using both techniques. The findings of this study suggest that due to the high initial variation between the diets of elephants, with an increase in resource availability, the impacts will also initially be highly varied. This suggests that identifying plant species to monitor elephants impacts initially will be difficult. However, important plant species, or those known to be vulnerable to elephants impacts should be carefully monitored initially and monitoring should not only occur annually, but also seasonally.
- Full Text:
- Date Issued: 2015
The foraging ecology of Wedge-tailed Shearwaters (Ardenna Pacifica) in the tropical Western Indian Ocean
- Authors: Keys, Danielle Zuanda
- Date: 2018
- Subjects: Birds of prey -- Behavior -- South Africa -- Western Cape , Animal behavior , Wildlife conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/31251 , vital:31348
- Description: The distribution and abundance of prey largely influences how marine predators forage. Thus, understanding how marine predators respond to such changes becomes imperative when making decisions in marine spatial planning, especially in light of global climate change. Tropical marine systems are known for their relatively low productivity and high unpredictability of prey resources. Compared to higher latitudes, very few studies on seabirds have been implemented in the tropics. The Wedge-tailed Shearwater Ardenna pacifica is an Indo-Pacific tropical seabird with a wide distributional range. However, like many other seabirds, its population numbers are currently declining. Very little is known about the at-sea distribution of Wedge-tailed Shearwaters in the tropical western Indian Ocean. Therefore, this thesis investigates the foraging ecology of Wedge-tailed Shearwaters in the western Indian Ocean by tracking the fine scale movements of individuals at sea. This study was conducted in two different oceanic environments, namely D’Arros Island and Fouquet Island, St Joseph Atoll in the Amirantes Group in Seychelles archipelago as well as Réunion Island in the Mascarene archipelago during the Wedge-tailed Shearwaters breeding seasons. Here I aimed to investigate the foraging distribution of Wedge-tailed Shearwaters on Réunion Island in relation to different stages of the breeding period. I also compared the foraging ecology of all three populations, subjected to different abiotic and biotic factors. Furthermore, I investigated foraging site fidelity in individuals and repeatability within individual flight characteristics. To my knowledge, this is the first study to comprehensively investigate the foraging ecology of Wedge-tailed Shearwaters using global positioning system (GPS) loggers. This study demonstrated that the Wedge-tailed Shearwaters implement flexible foraging strategies throughout different stages of their breeding period and between different islands. In Réunion, during the shearwater breeding season, sexual segregation was prominent during early chick rearing and both sexes implemented dual foraging. As suggested by previous studies, it is likely that long trips were implemented for self-maintenance, whereas multiple short trips were implemented to meet the high energetic demands of the chicks. Several important foraging areas were identified for these Wedge-tailed Shearwaters. During incubation, shearwaters from Réunion faithfully foraged towards the south east of Madagascar near the East Madagascar Current and flew over large areas of the Mascarene Basin. During chick rearing, shearwaters significantly constricted their range closer to the colony and exploited deep waters on the south-west of Réunion Island. Shearwaters concentrated near oceanographic features such as the Pérouse Seamount (which is a known area of high productivity) as well as the Bourdonnais Ridge. There was no clear evidence for spatial or sexual segregation between individuals from the two study colonies in Seychelles during incubation and birds utilized a broader foraging range than birds from Réunion. This is likely to be the result of a large annual phytoplankton bloom which coincides with the shearwater breeding season in Seychelles, providing many foraging opportunities within the Seychelles Basin. The shearwaters from Seychelles exploited the Amirante Basin, East Somali Basin, and parts of the Seychelles archipelago. Shearwaters from D’Arros flew further east and foraged in the Mascarene Basin. Shearwaters from all populations foraged over deep, relatively unproductive waters with relatively high sea surface temperatures which are similar oceanographic features favoured by tuna. Foraging plasticity between individuals from different colonies was observed with varying flight bearings, flight durations and the maximum distances travelled from their respective colonies. Shearwaters displayed dissimilar levels of site fidelity, where shearwaters from Réunion faithfully foraged towards south east Madagascar, while shearwaters from Seychelles foraged over a wide range over the Seychelles Basin. Foraging effort for shearwaters from Fouquet was lower than shearwaters from Reunion and they spent less time at sea and foraged closer to their colony. These difference in behaviour responses between colonies may be advantageous to shearwaters, indicating that they may be able to respond to some level of environmental variability resulting from climate change and anthropogenic pressures. Lastly, during chick rearing, though shearwaters showed low levels of repeatability in flight characterising, foraging site fidelity was high amongst some of the individuals. Here we see that shearwaters continuously rely on permanent features, like seamounts and possibly fish aggregating devices, which are known to attract high abundances of tuna. Shearwaters may to some extent be relying on memory to find prey in a seemingly unpredictable environment. This study has helped us gain valuable insight about the foraging ecology of Wedge-tailed Shearwaters in the western Indian Ocean. Together with similar studies determining the at-sea behaviour of seabirds, better informed recommendations can be made to marine spatial planners as to where much needed pelagic marine protection should be implemented to preserve marine life in this fascinating part of the global ocean.
- Full Text:
- Date Issued: 2018
- Authors: Keys, Danielle Zuanda
- Date: 2018
- Subjects: Birds of prey -- Behavior -- South Africa -- Western Cape , Animal behavior , Wildlife conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/31251 , vital:31348
- Description: The distribution and abundance of prey largely influences how marine predators forage. Thus, understanding how marine predators respond to such changes becomes imperative when making decisions in marine spatial planning, especially in light of global climate change. Tropical marine systems are known for their relatively low productivity and high unpredictability of prey resources. Compared to higher latitudes, very few studies on seabirds have been implemented in the tropics. The Wedge-tailed Shearwater Ardenna pacifica is an Indo-Pacific tropical seabird with a wide distributional range. However, like many other seabirds, its population numbers are currently declining. Very little is known about the at-sea distribution of Wedge-tailed Shearwaters in the tropical western Indian Ocean. Therefore, this thesis investigates the foraging ecology of Wedge-tailed Shearwaters in the western Indian Ocean by tracking the fine scale movements of individuals at sea. This study was conducted in two different oceanic environments, namely D’Arros Island and Fouquet Island, St Joseph Atoll in the Amirantes Group in Seychelles archipelago as well as Réunion Island in the Mascarene archipelago during the Wedge-tailed Shearwaters breeding seasons. Here I aimed to investigate the foraging distribution of Wedge-tailed Shearwaters on Réunion Island in relation to different stages of the breeding period. I also compared the foraging ecology of all three populations, subjected to different abiotic and biotic factors. Furthermore, I investigated foraging site fidelity in individuals and repeatability within individual flight characteristics. To my knowledge, this is the first study to comprehensively investigate the foraging ecology of Wedge-tailed Shearwaters using global positioning system (GPS) loggers. This study demonstrated that the Wedge-tailed Shearwaters implement flexible foraging strategies throughout different stages of their breeding period and between different islands. In Réunion, during the shearwater breeding season, sexual segregation was prominent during early chick rearing and both sexes implemented dual foraging. As suggested by previous studies, it is likely that long trips were implemented for self-maintenance, whereas multiple short trips were implemented to meet the high energetic demands of the chicks. Several important foraging areas were identified for these Wedge-tailed Shearwaters. During incubation, shearwaters from Réunion faithfully foraged towards the south east of Madagascar near the East Madagascar Current and flew over large areas of the Mascarene Basin. During chick rearing, shearwaters significantly constricted their range closer to the colony and exploited deep waters on the south-west of Réunion Island. Shearwaters concentrated near oceanographic features such as the Pérouse Seamount (which is a known area of high productivity) as well as the Bourdonnais Ridge. There was no clear evidence for spatial or sexual segregation between individuals from the two study colonies in Seychelles during incubation and birds utilized a broader foraging range than birds from Réunion. This is likely to be the result of a large annual phytoplankton bloom which coincides with the shearwater breeding season in Seychelles, providing many foraging opportunities within the Seychelles Basin. The shearwaters from Seychelles exploited the Amirante Basin, East Somali Basin, and parts of the Seychelles archipelago. Shearwaters from D’Arros flew further east and foraged in the Mascarene Basin. Shearwaters from all populations foraged over deep, relatively unproductive waters with relatively high sea surface temperatures which are similar oceanographic features favoured by tuna. Foraging plasticity between individuals from different colonies was observed with varying flight bearings, flight durations and the maximum distances travelled from their respective colonies. Shearwaters displayed dissimilar levels of site fidelity, where shearwaters from Réunion faithfully foraged towards south east Madagascar, while shearwaters from Seychelles foraged over a wide range over the Seychelles Basin. Foraging effort for shearwaters from Fouquet was lower than shearwaters from Reunion and they spent less time at sea and foraged closer to their colony. These difference in behaviour responses between colonies may be advantageous to shearwaters, indicating that they may be able to respond to some level of environmental variability resulting from climate change and anthropogenic pressures. Lastly, during chick rearing, though shearwaters showed low levels of repeatability in flight characterising, foraging site fidelity was high amongst some of the individuals. Here we see that shearwaters continuously rely on permanent features, like seamounts and possibly fish aggregating devices, which are known to attract high abundances of tuna. Shearwaters may to some extent be relying on memory to find prey in a seemingly unpredictable environment. This study has helped us gain valuable insight about the foraging ecology of Wedge-tailed Shearwaters in the western Indian Ocean. Together with similar studies determining the at-sea behaviour of seabirds, better informed recommendations can be made to marine spatial planners as to where much needed pelagic marine protection should be implemented to preserve marine life in this fascinating part of the global ocean.
- Full Text:
- Date Issued: 2018
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