"Is more, less?" : insect-insect interactions in a biological control context using water hyacinth as a model
- Weyl, Philip Sebastian Richard
- Authors: Weyl, Philip Sebastian Richard
- Date: 2012
- Subjects: Water hyacinth -- South Africa -- Eastern Cape , Water hyacinth -- Biological control -- South Africa -- Eastern Cape , Insects as biological pest control agents , Miridae -- South Africa -- Eastern Cape , Beetles -- South Africa -- Eastern Cape , Competition (Biology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5724 , http://hdl.handle.net/10962/d1005410 , Water hyacinth -- South Africa -- Eastern Cape , Water hyacinth -- Biological control -- South Africa -- Eastern Cape , Insects as biological pest control agents , Miridae -- South Africa -- Eastern Cape , Beetles -- South Africa -- Eastern Cape , Competition (Biology)
- Description: Interactions between insects have been shown to be important regulators of population abundances and dynamics as well as drivers of spatial segregation and distribution. These are important aspects of the ecology of insects used in biological control and may have implications for the overall success of a particular programme. In the history of biological control there has been a tendency to release a suite of agents against a weed, which in some cases has increased the level of success, while in others little change has been observed. In most of these cases the implications of increasing the level of complexity of the system is not taken into account and there is little research on the effect of releasing another agent into the system. A brief meta-analysis was done on all the biological control programmes initiated in South Africa. Emphasis was placed on multi-species releases and the effects that overlapping niches were having on the number of agents responsible for the success of a programme. Where overlapping niches were present among agents released the number of agents responsible for success was lower than the number established. Water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach in South Africa has more arthropod agents released against it than anywhere else in the world, yet control has been variable. If the biology and host utilisation of all the agents against water hyacinth is considered, a definite overlap of niches is apparent in at least one life stage of all the agents. Therefore the probability of these insects interacting is high, especially if they are established at the same site in the field. Three of the insects released in South Africa have been selected to investigate possible interactions. They are Neochetina eichhorniae Warner, Neochetina bruchi Hustache and Eccritotarsus catarinensis (Carvalho). Y-tube olfactometer bioassays were used to measure responses of these insects to water hyacinth with prior feeding damage by either conspecifics or heterospecifics. This was done to determine whether olfactory cues played a role in host acceptability and avoidance of conspecifics or heterospecifics. The insects were given a choice between damaged and undamaged plants in various combinations. There was a significant preference for the undamaged plants when given a choice between undamaged and damaged plants. However when the insects were given a choice between two damaged plants there was no discrimination between heterospecific or conspecific damaged plants. This may indicate that there is little or no ecological cost for the insect to share a plant with other insects utilising a similar resource. Insect – insect interactions were investigated in a common garden plot experiment to measure the impact that pairwise combinations of the insect may have on their performance. There was a significant interaction between the mirid E. catarinensis and the weevil N. eichhorniae, with the weevil not performing as well when in combination with the mirid than when alone. Interestingly there was a negative interaction between the two weevil species when in combination, however it was impossible to determine which species was being affected if not both. None of the insects performed significantly better when in combination with another insect. A field study on Wriggleswade Dam in the Eastern Cape, South Africa was initiated to determine whether the relationship between the mirid E. catarinensis and the weevil N. eichhorniae could be determined in the field. The performance of the insects at the different sites in the field suggests that there was an interaction between the agents. This interaction did not limit the establishment of either insect at a site, but it did result in one insect dominating at a site over another. Interactions between the three species of insect tested in this thesis suggest that there are both negative and neutral relationships between them. A basic comparison between the insect performances from 15 sites around the country was done to determine if the spatial segregation observed in the field could be extrapolated to the natural South African situation. The interaction observed between N. eichhorniae and E. catarinensis does seem to extrapolate to the general South African situation where there is definite spatial segregation on a landscape level. The co–occurrence of the two Neochetina weevils at these sites suggests that the negative relationship observed between them in the common garden experiment does not extrapolate to the field. The results from this thesis suggest that the interactions between the agents tested would not limit establishment or have significant ramifications on performance. However, there may be spatial and temporal segregation of these species in the introduced range.
- Full Text:
- Date Issued: 2012
- Authors: Weyl, Philip Sebastian Richard
- Date: 2012
- Subjects: Water hyacinth -- South Africa -- Eastern Cape , Water hyacinth -- Biological control -- South Africa -- Eastern Cape , Insects as biological pest control agents , Miridae -- South Africa -- Eastern Cape , Beetles -- South Africa -- Eastern Cape , Competition (Biology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5724 , http://hdl.handle.net/10962/d1005410 , Water hyacinth -- South Africa -- Eastern Cape , Water hyacinth -- Biological control -- South Africa -- Eastern Cape , Insects as biological pest control agents , Miridae -- South Africa -- Eastern Cape , Beetles -- South Africa -- Eastern Cape , Competition (Biology)
- Description: Interactions between insects have been shown to be important regulators of population abundances and dynamics as well as drivers of spatial segregation and distribution. These are important aspects of the ecology of insects used in biological control and may have implications for the overall success of a particular programme. In the history of biological control there has been a tendency to release a suite of agents against a weed, which in some cases has increased the level of success, while in others little change has been observed. In most of these cases the implications of increasing the level of complexity of the system is not taken into account and there is little research on the effect of releasing another agent into the system. A brief meta-analysis was done on all the biological control programmes initiated in South Africa. Emphasis was placed on multi-species releases and the effects that overlapping niches were having on the number of agents responsible for the success of a programme. Where overlapping niches were present among agents released the number of agents responsible for success was lower than the number established. Water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach in South Africa has more arthropod agents released against it than anywhere else in the world, yet control has been variable. If the biology and host utilisation of all the agents against water hyacinth is considered, a definite overlap of niches is apparent in at least one life stage of all the agents. Therefore the probability of these insects interacting is high, especially if they are established at the same site in the field. Three of the insects released in South Africa have been selected to investigate possible interactions. They are Neochetina eichhorniae Warner, Neochetina bruchi Hustache and Eccritotarsus catarinensis (Carvalho). Y-tube olfactometer bioassays were used to measure responses of these insects to water hyacinth with prior feeding damage by either conspecifics or heterospecifics. This was done to determine whether olfactory cues played a role in host acceptability and avoidance of conspecifics or heterospecifics. The insects were given a choice between damaged and undamaged plants in various combinations. There was a significant preference for the undamaged plants when given a choice between undamaged and damaged plants. However when the insects were given a choice between two damaged plants there was no discrimination between heterospecific or conspecific damaged plants. This may indicate that there is little or no ecological cost for the insect to share a plant with other insects utilising a similar resource. Insect – insect interactions were investigated in a common garden plot experiment to measure the impact that pairwise combinations of the insect may have on their performance. There was a significant interaction between the mirid E. catarinensis and the weevil N. eichhorniae, with the weevil not performing as well when in combination with the mirid than when alone. Interestingly there was a negative interaction between the two weevil species when in combination, however it was impossible to determine which species was being affected if not both. None of the insects performed significantly better when in combination with another insect. A field study on Wriggleswade Dam in the Eastern Cape, South Africa was initiated to determine whether the relationship between the mirid E. catarinensis and the weevil N. eichhorniae could be determined in the field. The performance of the insects at the different sites in the field suggests that there was an interaction between the agents. This interaction did not limit the establishment of either insect at a site, but it did result in one insect dominating at a site over another. Interactions between the three species of insect tested in this thesis suggest that there are both negative and neutral relationships between them. A basic comparison between the insect performances from 15 sites around the country was done to determine if the spatial segregation observed in the field could be extrapolated to the natural South African situation. The interaction observed between N. eichhorniae and E. catarinensis does seem to extrapolate to the general South African situation where there is definite spatial segregation on a landscape level. The co–occurrence of the two Neochetina weevils at these sites suggests that the negative relationship observed between them in the common garden experiment does not extrapolate to the field. The results from this thesis suggest that the interactions between the agents tested would not limit establishment or have significant ramifications on performance. However, there may be spatial and temporal segregation of these species in the introduced range.
- Full Text:
- Date Issued: 2012
A spatial and temporal analysis of the changes in alien macrophyte communities and a baseline assessment of the macroinvertebrates associated with Eurasian watermilfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River
- Authors: Fordham, Colin Justin
- Date: 2012
- Subjects: Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5767 , http://hdl.handle.net/10962/d1005455 , Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Description: The majority of South Africa’s fresh water (lotic and lentic), is eutrophic and this has resulted in water hyacinth, Eichhornia crassipes (C.Mart.) Solms. (Pontederiaceae) becoming South Africa’s most damaging aquatic macrophyte. Recently however, concerns have also been voiced over the presence of highly invasive submerged macrophyte species, such as Eurasian water-milfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River. Interaction studies between floating and submerged macrophytes have shown that floating macrophyte dominance restricts light penetration into the water column shading out submerged macrophytes while submerged macrophyte dominance reduces nutrient availability in the water column limiting floating macrophyte growth. This cycle ensures that these species cannot coexist in the same habitat for extended periods of time. The aims of this thesis were to: 1. Investigate changes in the historical and current macrophyte dominance in the Vaal River 2. Determine whether these changes could be attributed to stochastic events, such as floods and herbicide control measures. 3. The physio-chemical conditions of the water column, and whether pressure from herbivory by macroinvertebrates had possibly influenced Eurasian water-milfoil’s ability to dominate. Spatial and temporal analysis of satellite imagery revealed that water hyacinth and submerged macrophyte species dominated different regions of the study area over different periods of time from 2006 to 2010. This was significantly correlated with nitrate concentrations of the water column. One of the lower Vaal River Water Management Areas (WMA) had changed from a water hyacinth dominated state in 2006 to an alternative submerged macrophyte dominated stable state in 2008. It was concluded that this change could be attributed to: a stochastic flooding event in 2006; perturbation from integrated control measures implemented against water hyacinth; and low nitrate concentrations of the WMA. The lack of any substantial macroinvertebrate herbivory pressure or control measures implemented against Eurasian water-milfoil, compared to similar surveys conducted in the U.S.A. and its native range in Eurasia was shown to contribute to its dominance. Future successful integrated control programmes, including biological control against Eurasian water-milfoil, could provide the perturbation required to restore the ecosystem. However, without the reduction in nitrate concentration levels, water hyacinth will remain the dominant stable state of the rest of the Vaal River.
- Full Text:
- Date Issued: 2012
- Authors: Fordham, Colin Justin
- Date: 2012
- Subjects: Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5767 , http://hdl.handle.net/10962/d1005455 , Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Description: The majority of South Africa’s fresh water (lotic and lentic), is eutrophic and this has resulted in water hyacinth, Eichhornia crassipes (C.Mart.) Solms. (Pontederiaceae) becoming South Africa’s most damaging aquatic macrophyte. Recently however, concerns have also been voiced over the presence of highly invasive submerged macrophyte species, such as Eurasian water-milfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River. Interaction studies between floating and submerged macrophytes have shown that floating macrophyte dominance restricts light penetration into the water column shading out submerged macrophytes while submerged macrophyte dominance reduces nutrient availability in the water column limiting floating macrophyte growth. This cycle ensures that these species cannot coexist in the same habitat for extended periods of time. The aims of this thesis were to: 1. Investigate changes in the historical and current macrophyte dominance in the Vaal River 2. Determine whether these changes could be attributed to stochastic events, such as floods and herbicide control measures. 3. The physio-chemical conditions of the water column, and whether pressure from herbivory by macroinvertebrates had possibly influenced Eurasian water-milfoil’s ability to dominate. Spatial and temporal analysis of satellite imagery revealed that water hyacinth and submerged macrophyte species dominated different regions of the study area over different periods of time from 2006 to 2010. This was significantly correlated with nitrate concentrations of the water column. One of the lower Vaal River Water Management Areas (WMA) had changed from a water hyacinth dominated state in 2006 to an alternative submerged macrophyte dominated stable state in 2008. It was concluded that this change could be attributed to: a stochastic flooding event in 2006; perturbation from integrated control measures implemented against water hyacinth; and low nitrate concentrations of the WMA. The lack of any substantial macroinvertebrate herbivory pressure or control measures implemented against Eurasian water-milfoil, compared to similar surveys conducted in the U.S.A. and its native range in Eurasia was shown to contribute to its dominance. Future successful integrated control programmes, including biological control against Eurasian water-milfoil, could provide the perturbation required to restore the ecosystem. However, without the reduction in nitrate concentration levels, water hyacinth will remain the dominant stable state of the rest of the Vaal River.
- Full Text:
- Date Issued: 2012
A systematic revision of selected genera of afrotropical curtonotidae (Diptera: schizophora: ephydroidea) : a phylogenetic approach
- Authors: Kirk-Spriggs, Ashley H
- Date: 2012
- Subjects: Curtonotidae -- Research Diptera -- Research Flies -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5627 , http://hdl.handle.net/10962/d1004747
- Description: The first comprehensive phylogeny of the family Curtonotidae is presented based on molecular markers and morphology. This enabled assessment of evolutionary relatedness, species radiation and zoogeography. A revised classification of the world fauna of the family, based on the results of this study is outlined. Nomenclatural acts flowing from these analyses include: the recognition three new Afrotropical species of Axinota van der Wulp; four new species of a new genus, Tigrisomyia Kirk-Spriggs; and nineteen new species of Curtonotum (six Madagascan and thirteen African). Ten informal species-groups of Curtonotum are recognised. Identification keys are provided for the Afrotropical species of these genera and errors in previous interpretations and designation of type specimens are resolved. Species distributions are mapped and interpreted and discussion is made of the historical biogeographical significance of these distributions.
- Full Text:
- Date Issued: 2012
- Authors: Kirk-Spriggs, Ashley H
- Date: 2012
- Subjects: Curtonotidae -- Research Diptera -- Research Flies -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5627 , http://hdl.handle.net/10962/d1004747
- Description: The first comprehensive phylogeny of the family Curtonotidae is presented based on molecular markers and morphology. This enabled assessment of evolutionary relatedness, species radiation and zoogeography. A revised classification of the world fauna of the family, based on the results of this study is outlined. Nomenclatural acts flowing from these analyses include: the recognition three new Afrotropical species of Axinota van der Wulp; four new species of a new genus, Tigrisomyia Kirk-Spriggs; and nineteen new species of Curtonotum (six Madagascan and thirteen African). Ten informal species-groups of Curtonotum are recognised. Identification keys are provided for the Afrotropical species of these genera and errors in previous interpretations and designation of type specimens are resolved. Species distributions are mapped and interpreted and discussion is made of the historical biogeographical significance of these distributions.
- Full Text:
- Date Issued: 2012
An assessment of caracal population density and human-predator conflict in the Winterberg, Eastern Cape, South Africa
- Authors: Smith, Emma Ruth
- Date: 2012
- Subjects: Felis -- South Africa -- Eastern Cape , Felis -- Effect of human beings on -- South Africa -- Eastern Cape , Predatory animals -- Control -- South Africa -- Eastern Cape , Wildlife depredation -- South Africa -- Eastern Cape , Human-animal relationships , Felis -- Conservation -- South Africa -- Eastern Cape , Felis -- Monitoring -- South Africa -- Eastern Cape , Animal populations -- Estimates
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5644 , http://hdl.handle.net/10962/d1005326 , Felis -- South Africa -- Eastern Cape , Felis -- Effect of human beings on -- South Africa -- Eastern Cape , Predatory animals -- Control -- South Africa -- Eastern Cape , Wildlife depredation -- South Africa -- Eastern Cape , Human-animal relationships , Felis -- Conservation -- South Africa -- Eastern Cape , Felis -- Monitoring -- South Africa -- Eastern Cape , Animal populations -- Estimates
- Description: Human-wildlife conflict frequently involves carnivores, mainly because of their large home ranges and dietary requirements. As such, carnivores tend to be the first animals to be lost in human-dominated ecosystems. This is significant because the removal of carnivores can alter the functionality of ecosystems. However, the conservation of carnivores depends as much on the socio-political and socio-economic landscapes as it does on the ecological one. The consolidation of vast, un-fragmented conservation areas in Africa and the world is unlikely. Thus, unravelling the factors (both biological and sociological) responsible for and influencing human-predator conflict is critical for carnivore conservation. The Winterberg district in the Eastern Cape, South Africa has been a sheep (Ovis aries) farming stronghold for nearly 200 years. Consequently, conflict between farmers and predators is commonplace and depredation of livestock by caracals (Caracai caracal) remains a perennial problem. However, the extent of this human-predator conflict (including a reliable assessment of caracal density) has not been quantified. This study used camera trapping to estimate the density of caracals (a nonindividually recognisable species) in the Winterberg and a structured questionnaire to gauge the general attitudes of the farmers of the region. Caracal density was estimated to be 0.20 caracals/km². This estimate equates to a population of approximately 54 caracals across the entire district. Therefore, caracals do not appear to occur at high densities in the Winterberg. However, the survey of the residents of the Winterberg Conservancy revealed that predators were rated as the greatest problem faced by farmers in the area. Although not significant, it also showed that the size of a respondent's property and sheep mortality due to caracals had the greatest probability of affecting attitudes towards predators. The farmers lost less than 10% of their stock to caracal depredation on an annual basis. Therefore, the general perception that predators were the most important factor in stock loss in the area does not appear to be fully supported by my data. The Winterberg is a male-dominated, multigenerational society and it is likely this propagates certain perceptions towards predators which are a reflection of long-held family traditions and beliefs. Such situations can result in reactions which are disproportionate to the actual scale of the problem. However, my study was limited to a sub-set of the landowners in the Winterberg. Thus, more intensive assessments of caracal space use and community attitudes towards predators are recommended.
- Full Text:
- Date Issued: 2012
- Authors: Smith, Emma Ruth
- Date: 2012
- Subjects: Felis -- South Africa -- Eastern Cape , Felis -- Effect of human beings on -- South Africa -- Eastern Cape , Predatory animals -- Control -- South Africa -- Eastern Cape , Wildlife depredation -- South Africa -- Eastern Cape , Human-animal relationships , Felis -- Conservation -- South Africa -- Eastern Cape , Felis -- Monitoring -- South Africa -- Eastern Cape , Animal populations -- Estimates
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5644 , http://hdl.handle.net/10962/d1005326 , Felis -- South Africa -- Eastern Cape , Felis -- Effect of human beings on -- South Africa -- Eastern Cape , Predatory animals -- Control -- South Africa -- Eastern Cape , Wildlife depredation -- South Africa -- Eastern Cape , Human-animal relationships , Felis -- Conservation -- South Africa -- Eastern Cape , Felis -- Monitoring -- South Africa -- Eastern Cape , Animal populations -- Estimates
- Description: Human-wildlife conflict frequently involves carnivores, mainly because of their large home ranges and dietary requirements. As such, carnivores tend to be the first animals to be lost in human-dominated ecosystems. This is significant because the removal of carnivores can alter the functionality of ecosystems. However, the conservation of carnivores depends as much on the socio-political and socio-economic landscapes as it does on the ecological one. The consolidation of vast, un-fragmented conservation areas in Africa and the world is unlikely. Thus, unravelling the factors (both biological and sociological) responsible for and influencing human-predator conflict is critical for carnivore conservation. The Winterberg district in the Eastern Cape, South Africa has been a sheep (Ovis aries) farming stronghold for nearly 200 years. Consequently, conflict between farmers and predators is commonplace and depredation of livestock by caracals (Caracai caracal) remains a perennial problem. However, the extent of this human-predator conflict (including a reliable assessment of caracal density) has not been quantified. This study used camera trapping to estimate the density of caracals (a nonindividually recognisable species) in the Winterberg and a structured questionnaire to gauge the general attitudes of the farmers of the region. Caracal density was estimated to be 0.20 caracals/km². This estimate equates to a population of approximately 54 caracals across the entire district. Therefore, caracals do not appear to occur at high densities in the Winterberg. However, the survey of the residents of the Winterberg Conservancy revealed that predators were rated as the greatest problem faced by farmers in the area. Although not significant, it also showed that the size of a respondent's property and sheep mortality due to caracals had the greatest probability of affecting attitudes towards predators. The farmers lost less than 10% of their stock to caracal depredation on an annual basis. Therefore, the general perception that predators were the most important factor in stock loss in the area does not appear to be fully supported by my data. The Winterberg is a male-dominated, multigenerational society and it is likely this propagates certain perceptions towards predators which are a reflection of long-held family traditions and beliefs. Such situations can result in reactions which are disproportionate to the actual scale of the problem. However, my study was limited to a sub-set of the landowners in the Winterberg. Thus, more intensive assessments of caracal space use and community attitudes towards predators are recommended.
- Full Text:
- Date Issued: 2012
Anthropogenic threats to resident and dispersing African wild dogs west and south of the Kruger National Park, South Africa
- Watermeyer, Jessica Patricia
- Authors: Watermeyer, Jessica Patricia
- Date: 2012
- Subjects: African wild dog -- South Africa -- Kruger National Park , African wild dog -- Effect of human beings on -- South Africa -- Kruger National Park , African wild dog -- Behavior -- South Africa -- Kruger National Park , Endangered species -- South Africa -- Kruger National Park , African wild dog -- Dispersal -- South Africa -- Kruger National Park , African wild dog -- Conservation -- South Africa -- Kruger National Park , Animal populations -- Estimates -- South Africa -- Kruger National Park
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5636 , http://hdl.handle.net/10962/d1005318 , African wild dog -- South Africa -- Kruger National Park , African wild dog -- Effect of human beings on -- South Africa -- Kruger National Park , African wild dog -- Behavior -- South Africa -- Kruger National Park , Endangered species -- South Africa -- Kruger National Park , African wild dog -- Dispersal -- South Africa -- Kruger National Park , African wild dog -- Conservation -- South Africa -- Kruger National Park , Animal populations -- Estimates -- South Africa -- Kruger National Park
- Description: African wild dog Lycaon pictus populations are declining and the species is listed as Endangered by the IUCN. The Kruger National Park (KNP) is home to the only viable population of wild dogs in South Africa, but census results reveal consistently low numbers since the late 1990s. Wild dogs display wide-ranging behaviour and it is possible that the species might frequently use unprotected lands adjacent to the KNP. However, very little is known about wild dog movements beyond the boundaries of the KNP, and whether or not adjacent land owners are tolerant of the species. Significantly, threats along the boundaries may have negative consequences for the KNP population. This research investigated the dispersal habits of wild dogs beyond the western and southern boundaries of the KNP, and gathered information on human tolerance, and anthropogenic threats in an area of mixed land use. The land west of the KNP presented the best prospect for wild dog range expansion. The wild dog packs operating outside the KNP had smaller home ranges and less home range overlap than the packs operating within the KNP. In addition, my data suggested that the development of conservancies and the formation of ecotourism-based land use practices would be beneficial for wild dog conservation. Failed wild dog dispersals due to snaring and human persecution could threaten the genetic stability and persistence of the KNP population. Therefore, raising awareness and an understanding of the plight of wild dogs is important for improving land owner perception and tolerance outside of protected areas. The rapidly increasing human population continues to infringe on protected lands and fragment landscapes, thus cooperation from individual land owners is vital for the conservation of free-ranging large carnivores.
- Full Text:
- Date Issued: 2012
- Authors: Watermeyer, Jessica Patricia
- Date: 2012
- Subjects: African wild dog -- South Africa -- Kruger National Park , African wild dog -- Effect of human beings on -- South Africa -- Kruger National Park , African wild dog -- Behavior -- South Africa -- Kruger National Park , Endangered species -- South Africa -- Kruger National Park , African wild dog -- Dispersal -- South Africa -- Kruger National Park , African wild dog -- Conservation -- South Africa -- Kruger National Park , Animal populations -- Estimates -- South Africa -- Kruger National Park
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5636 , http://hdl.handle.net/10962/d1005318 , African wild dog -- South Africa -- Kruger National Park , African wild dog -- Effect of human beings on -- South Africa -- Kruger National Park , African wild dog -- Behavior -- South Africa -- Kruger National Park , Endangered species -- South Africa -- Kruger National Park , African wild dog -- Dispersal -- South Africa -- Kruger National Park , African wild dog -- Conservation -- South Africa -- Kruger National Park , Animal populations -- Estimates -- South Africa -- Kruger National Park
- Description: African wild dog Lycaon pictus populations are declining and the species is listed as Endangered by the IUCN. The Kruger National Park (KNP) is home to the only viable population of wild dogs in South Africa, but census results reveal consistently low numbers since the late 1990s. Wild dogs display wide-ranging behaviour and it is possible that the species might frequently use unprotected lands adjacent to the KNP. However, very little is known about wild dog movements beyond the boundaries of the KNP, and whether or not adjacent land owners are tolerant of the species. Significantly, threats along the boundaries may have negative consequences for the KNP population. This research investigated the dispersal habits of wild dogs beyond the western and southern boundaries of the KNP, and gathered information on human tolerance, and anthropogenic threats in an area of mixed land use. The land west of the KNP presented the best prospect for wild dog range expansion. The wild dog packs operating outside the KNP had smaller home ranges and less home range overlap than the packs operating within the KNP. In addition, my data suggested that the development of conservancies and the formation of ecotourism-based land use practices would be beneficial for wild dog conservation. Failed wild dog dispersals due to snaring and human persecution could threaten the genetic stability and persistence of the KNP population. Therefore, raising awareness and an understanding of the plight of wild dogs is important for improving land owner perception and tolerance outside of protected areas. The rapidly increasing human population continues to infringe on protected lands and fragment landscapes, thus cooperation from individual land owners is vital for the conservation of free-ranging large carnivores.
- Full Text:
- Date Issued: 2012
Feeding dynamics of suspension-feeders in the nearshore marine environment adjacent to two contrasting estuaries in the Eastern Cape, South Africa
- Authors: Vermeulen, Ilke
- Date: 2012
- Subjects: Suspension feeders -- South Africa -- Eastern Cape , Suspension feeders -- Food -- South Africa -- Eastern Cape , Coastal organisms -- South Africa -- Eastern Cape , Streamflow -- South Africa -- Eastern Cape , Tetraclitidae -- South Africa -- Eastern Cape , Mexilhao mussel -- South Africa -- Eastern Cape , Polychaeta -- South Africa -- Eastern Cape , Estuarine health -- South Africa -- Eastern Cape , Estuaries -- Freshwater inflow -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5916 , http://hdl.handle.net/10962/d1016242
- Description: Coastal transition zones form important interlinking regions where marine ecosystems, rivers and estuarine environments significantly influence each other. Coastal rocky shores are key habitats that sustain a variety of primary producers and invertebrates and due to the dynamic nature of coastal ecosystems, suspension-feeders on rocky shores can be influenced by an array of autochthonous and allochthonous food sources. Fatty acid and stable isotope trophic markers were employed to distinguish between regional and temporal changes in the potential food sources to rocky shore suspension-feeders in the Eastern Cape Province of South Africa. The primary aim was to assess the spatial and temporal influences of contrasting river flows on the available food sources to three indigenous coastal suspensionfeeders, namely the volcano barnacle Tetraclita serrata, brown mussel Perna perna and tubebuilding polychaete Gunnarea capensis. This was done by examining the intra- and interspecific changes in the fatty acid and stable isotope signatures of the barnacles, mussels and polychaetes in the adjacent marine environment of a freshwater-restricted (Kariega) and freshwater-dominated (Great Fish) estuary during austral summer and winter. Multivariate and Kruskal-Wallis analyses of variance on the fatty acid and isotopic signatures, respectively, identified significant regional changes in the barnacles and mussels, while only stable isotopes distinguished between the Kariega and Great Fish polychaetes (P < 0.05). In addition, significant temporal changes were observed in consumer fatty acids and isotope values in both regions (P < 0.05). Bacterial sources, detritus and phytoplankton assemblages, which are influenced by hydrology and vegetation, differed between regions and were mainly responsible for the regional and temporal separations. Principal component analyses on the consumer fatty acid signatures distinguished between animals situated upstream (i.e. north) and downstream (i.e. south) of the Kariega Estuary mouth in summer. The north/south separation was mainly due to greater contributions of diatoms to northernlocated animals and dinoflagellates and detritus to southern-located consumers. In addition, the south-flowing Agulhas Current on the eastern shores of southern Africa appeared to influence the north/south separation in the Kariega region, as water leaving the estuary was probably entrained into the south-easterly flowing currents, thereby depositing estuarinederived detritus to southern populations. In general, diatoms and detritus were essential food sources to the filter-feeders in summer, and flagellates, diatoms, zooplankton and detritus were important in winter. Coastal macroalgae was a key food source in the Kariega and Great Fish regions during both seasons. Consistently large levels of diatom markers (16:1n-7 and 20:5n-3) and dinoflagellate markers (22:6n-3) in consumer tissues in the Kariega and Great Fish regions identified that phytoplankton was their dominant food source. The barnacles, mussels and polychaetes had similar fatty acid markers and a fairly narrow δ¹³C range (-16.5 to -14.4 ‰), suggesting that they probably consumed similar food. Carbon isotope analyses, however, separated the suspension-feeders into slightly depleted (barnacles; -16.5 to -16.1 ‰), intermediate (mussels; -15.8 to -15.0 ‰) and enriched (polychaetes; -15.0 to -14.4 ‰) consumers, but did not provide conclusive evidence of their preferences for specific phytoplankton. Conversely, fatty acid analyses highlighted that barnacles and mussels had greater proportions of dinoflagellate markers (22:6n-3; 7.0-15.3 % TFA), while polychaetes had larger diatom levels (20:5n-3; 15.1-22.2 % TFA). In addition, all three species had consistently large contributions from bacterial fatty acids (15:0, i-16:0, 17:0 and i-18:0; 4.2-13.6 % TFA) in summer and winter, and large proportions of saturated fatty acids (33.3-53.1 % TFA) including those with 14 to 18 carbons, indicating that bacterial and detritus food sources played an important role in their diets. Barnacles had small levels of terrestrial markers (18:2n-6 and 18:3n-3; <2.5 % TFA) and demonstrated increased omnivorous feeding compared with the other suspension-feeders [increased levels of 20:1n-11 and 20:1n-9, higher 18:1n-9/18:1n-7 ratios at ~2.1, enriched δ¹⁵N values at ~10.6 ‰; zooplankton (potentially including microzooplankton, larvae and protists) contribution of up to 61 % of the diet]. Mussels contained significant proportions of the terrestrial markers (18:2n-6 and 18:3n-3; >2.5 % TFA) and exhibited intermediate omnivory (intermediate levels of 20:1n-11 and 20:1n-9, intermediate 18:1n-9/18:1n-7 ratios at ~1.3, less enriched δ¹⁵N values at ~7.9 ‰; zooplankton contribution of 10-15 % of the diet). The more depleted nitrogen signatures in the mussels relative to the barnacles and polychaetes possibly illustrated a stronger preference for autotrophic food. Polychaetes mainly consumed plant food sources (i.e. microalgae, macroalgae and detritus; high levels of i-18:0, 18:1n-9, 18:4n-3 and 20:5n-3) and displayed little omnivory (low levels of 20:1n-11 and 20:1n-9, low 18:1n-9/18:1n-7 ratios at ~0.4, intermediate δ¹⁵N values at ~9.1 ‰; zooplankton contribution of <10 % of the diet). The barnacles, mussels and polychaetes are all suspension-feeders, originally presumed to consume the same food sources. The variations observed among the species, therefore, may result from differences in the proportional contributions of the various food sources to their diets as well as distinctions in metabolism. The distinct changes in the fatty acid and stable isotope signatures in all three filter-feeders in the Kariega and Great Fish regions are likely influenced by the diversity in regional vegetation and hydrology in the different systems, combined with interspecific differences in resource partitioning among the species.
- Full Text:
- Date Issued: 2012
- Authors: Vermeulen, Ilke
- Date: 2012
- Subjects: Suspension feeders -- South Africa -- Eastern Cape , Suspension feeders -- Food -- South Africa -- Eastern Cape , Coastal organisms -- South Africa -- Eastern Cape , Streamflow -- South Africa -- Eastern Cape , Tetraclitidae -- South Africa -- Eastern Cape , Mexilhao mussel -- South Africa -- Eastern Cape , Polychaeta -- South Africa -- Eastern Cape , Estuarine health -- South Africa -- Eastern Cape , Estuaries -- Freshwater inflow -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5916 , http://hdl.handle.net/10962/d1016242
- Description: Coastal transition zones form important interlinking regions where marine ecosystems, rivers and estuarine environments significantly influence each other. Coastal rocky shores are key habitats that sustain a variety of primary producers and invertebrates and due to the dynamic nature of coastal ecosystems, suspension-feeders on rocky shores can be influenced by an array of autochthonous and allochthonous food sources. Fatty acid and stable isotope trophic markers were employed to distinguish between regional and temporal changes in the potential food sources to rocky shore suspension-feeders in the Eastern Cape Province of South Africa. The primary aim was to assess the spatial and temporal influences of contrasting river flows on the available food sources to three indigenous coastal suspensionfeeders, namely the volcano barnacle Tetraclita serrata, brown mussel Perna perna and tubebuilding polychaete Gunnarea capensis. This was done by examining the intra- and interspecific changes in the fatty acid and stable isotope signatures of the barnacles, mussels and polychaetes in the adjacent marine environment of a freshwater-restricted (Kariega) and freshwater-dominated (Great Fish) estuary during austral summer and winter. Multivariate and Kruskal-Wallis analyses of variance on the fatty acid and isotopic signatures, respectively, identified significant regional changes in the barnacles and mussels, while only stable isotopes distinguished between the Kariega and Great Fish polychaetes (P < 0.05). In addition, significant temporal changes were observed in consumer fatty acids and isotope values in both regions (P < 0.05). Bacterial sources, detritus and phytoplankton assemblages, which are influenced by hydrology and vegetation, differed between regions and were mainly responsible for the regional and temporal separations. Principal component analyses on the consumer fatty acid signatures distinguished between animals situated upstream (i.e. north) and downstream (i.e. south) of the Kariega Estuary mouth in summer. The north/south separation was mainly due to greater contributions of diatoms to northernlocated animals and dinoflagellates and detritus to southern-located consumers. In addition, the south-flowing Agulhas Current on the eastern shores of southern Africa appeared to influence the north/south separation in the Kariega region, as water leaving the estuary was probably entrained into the south-easterly flowing currents, thereby depositing estuarinederived detritus to southern populations. In general, diatoms and detritus were essential food sources to the filter-feeders in summer, and flagellates, diatoms, zooplankton and detritus were important in winter. Coastal macroalgae was a key food source in the Kariega and Great Fish regions during both seasons. Consistently large levels of diatom markers (16:1n-7 and 20:5n-3) and dinoflagellate markers (22:6n-3) in consumer tissues in the Kariega and Great Fish regions identified that phytoplankton was their dominant food source. The barnacles, mussels and polychaetes had similar fatty acid markers and a fairly narrow δ¹³C range (-16.5 to -14.4 ‰), suggesting that they probably consumed similar food. Carbon isotope analyses, however, separated the suspension-feeders into slightly depleted (barnacles; -16.5 to -16.1 ‰), intermediate (mussels; -15.8 to -15.0 ‰) and enriched (polychaetes; -15.0 to -14.4 ‰) consumers, but did not provide conclusive evidence of their preferences for specific phytoplankton. Conversely, fatty acid analyses highlighted that barnacles and mussels had greater proportions of dinoflagellate markers (22:6n-3; 7.0-15.3 % TFA), while polychaetes had larger diatom levels (20:5n-3; 15.1-22.2 % TFA). In addition, all three species had consistently large contributions from bacterial fatty acids (15:0, i-16:0, 17:0 and i-18:0; 4.2-13.6 % TFA) in summer and winter, and large proportions of saturated fatty acids (33.3-53.1 % TFA) including those with 14 to 18 carbons, indicating that bacterial and detritus food sources played an important role in their diets. Barnacles had small levels of terrestrial markers (18:2n-6 and 18:3n-3; <2.5 % TFA) and demonstrated increased omnivorous feeding compared with the other suspension-feeders [increased levels of 20:1n-11 and 20:1n-9, higher 18:1n-9/18:1n-7 ratios at ~2.1, enriched δ¹⁵N values at ~10.6 ‰; zooplankton (potentially including microzooplankton, larvae and protists) contribution of up to 61 % of the diet]. Mussels contained significant proportions of the terrestrial markers (18:2n-6 and 18:3n-3; >2.5 % TFA) and exhibited intermediate omnivory (intermediate levels of 20:1n-11 and 20:1n-9, intermediate 18:1n-9/18:1n-7 ratios at ~1.3, less enriched δ¹⁵N values at ~7.9 ‰; zooplankton contribution of 10-15 % of the diet). The more depleted nitrogen signatures in the mussels relative to the barnacles and polychaetes possibly illustrated a stronger preference for autotrophic food. Polychaetes mainly consumed plant food sources (i.e. microalgae, macroalgae and detritus; high levels of i-18:0, 18:1n-9, 18:4n-3 and 20:5n-3) and displayed little omnivory (low levels of 20:1n-11 and 20:1n-9, low 18:1n-9/18:1n-7 ratios at ~0.4, intermediate δ¹⁵N values at ~9.1 ‰; zooplankton contribution of <10 % of the diet). The barnacles, mussels and polychaetes are all suspension-feeders, originally presumed to consume the same food sources. The variations observed among the species, therefore, may result from differences in the proportional contributions of the various food sources to their diets as well as distinctions in metabolism. The distinct changes in the fatty acid and stable isotope signatures in all three filter-feeders in the Kariega and Great Fish regions are likely influenced by the diversity in regional vegetation and hydrology in the different systems, combined with interspecific differences in resource partitioning among the species.
- Full Text:
- Date Issued: 2012
Leopard population density, home range size and movement patterns in a mixed landuse area of the Mangwe District of Zimbabwe
- Authors: Grant, Tanith-Leigh
- Date: 2012
- Subjects: Leopard -- Monitoring -- Zimbabwe , Leopard -- Conservation -- Zimbabwe , Wildlife monitoring -- Zimbabwe , Wildlife conservation -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5726 , http://hdl.handle.net/10962/d1005412 , Leopard -- Monitoring -- Zimbabwe , Leopard -- Conservation -- Zimbabwe , Wildlife monitoring -- Zimbabwe , Wildlife conservation -- Zimbabwe
- Description: Trophy hunting is often employed as a conservation management tool for large predators. However, in order for this method to succeed, hunting levels must be sustainable. Very little robust population data exist for African leopards (Panthera pardus) in general, and almost no density or spatial ecology data exist for leopards in Zimbabwe. Zimbabwe has one of the highest annual CITES leopard trophy hunting quotas in Africa, the sustainability of which has not been assessed, despite large scale landuse changes over the last 12 years. The focal area of this study was within the Mangwe district, in the south-west of Zimbabwe. The region is dominated by cattle and wildlife ranches, with high levels of leopard hunting, making it an important area for assessing leopard population density and spatial ecology. Three population density estimation methods were employed in my study: a spoor index survey, an unbaited camera-trapping survey and a baited camera-trapping survey. Using three calibration equations, spoor indices appeared to underestimate the leopard population (1.28-3.29 leopards/ 100 km²) as the equations were calibrated for areas with different habitats and leopard densities. In addition, the unbaited camera survey only produced six leopard photographs, unsuitable for individual identification and analysis. By contrast, the baited camera survey produced 292 identifiable leopard photographs, from which 13 individuals were identified. Density estimates calculated using the programme CAPTURE and the M[subscript]h model with the Mean Maximum Distance Moved Outside of Study Area (MMDMOSA) buffer method (4.79±0.83 leopards/100 km²), and the programme SPACECAP, using a buffer of 2.5 km (5.12±0.62 leopards/100 km²), appeared to generate the most reliable leopard population estimates. To assess the spatial ecology, three leopards (one male, two females) were captured and fitted with GPS collars. The home range estimates of the three leopards (95% Kernel UD: male 263 km², females 31 and 45 km²) were smaller than those of leopards in more arid regions, but larger than those of mesic habitats. This suggests that the Mangwe area has a higher quality habitat than the arid regions of Namibia, but less suitable habitat than protected bushveld areas (e.g. Kruger National Park, South Africa). My data represents the first robust leopard density and home range assessment for Zimbabwe. In addition, my results indicate that the current hunting quota issued to the Mangwe area is unsustainable. Consequently, I recommend revising the quota to five leopards for the entire area, and halving the current national leopard quota to 250, until a national leopard census is completed.
- Full Text:
- Date Issued: 2012
- Authors: Grant, Tanith-Leigh
- Date: 2012
- Subjects: Leopard -- Monitoring -- Zimbabwe , Leopard -- Conservation -- Zimbabwe , Wildlife monitoring -- Zimbabwe , Wildlife conservation -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5726 , http://hdl.handle.net/10962/d1005412 , Leopard -- Monitoring -- Zimbabwe , Leopard -- Conservation -- Zimbabwe , Wildlife monitoring -- Zimbabwe , Wildlife conservation -- Zimbabwe
- Description: Trophy hunting is often employed as a conservation management tool for large predators. However, in order for this method to succeed, hunting levels must be sustainable. Very little robust population data exist for African leopards (Panthera pardus) in general, and almost no density or spatial ecology data exist for leopards in Zimbabwe. Zimbabwe has one of the highest annual CITES leopard trophy hunting quotas in Africa, the sustainability of which has not been assessed, despite large scale landuse changes over the last 12 years. The focal area of this study was within the Mangwe district, in the south-west of Zimbabwe. The region is dominated by cattle and wildlife ranches, with high levels of leopard hunting, making it an important area for assessing leopard population density and spatial ecology. Three population density estimation methods were employed in my study: a spoor index survey, an unbaited camera-trapping survey and a baited camera-trapping survey. Using three calibration equations, spoor indices appeared to underestimate the leopard population (1.28-3.29 leopards/ 100 km²) as the equations were calibrated for areas with different habitats and leopard densities. In addition, the unbaited camera survey only produced six leopard photographs, unsuitable for individual identification and analysis. By contrast, the baited camera survey produced 292 identifiable leopard photographs, from which 13 individuals were identified. Density estimates calculated using the programme CAPTURE and the M[subscript]h model with the Mean Maximum Distance Moved Outside of Study Area (MMDMOSA) buffer method (4.79±0.83 leopards/100 km²), and the programme SPACECAP, using a buffer of 2.5 km (5.12±0.62 leopards/100 km²), appeared to generate the most reliable leopard population estimates. To assess the spatial ecology, three leopards (one male, two females) were captured and fitted with GPS collars. The home range estimates of the three leopards (95% Kernel UD: male 263 km², females 31 and 45 km²) were smaller than those of leopards in more arid regions, but larger than those of mesic habitats. This suggests that the Mangwe area has a higher quality habitat than the arid regions of Namibia, but less suitable habitat than protected bushveld areas (e.g. Kruger National Park, South Africa). My data represents the first robust leopard density and home range assessment for Zimbabwe. In addition, my results indicate that the current hunting quota issued to the Mangwe area is unsustainable. Consequently, I recommend revising the quota to five leopards for the entire area, and halving the current national leopard quota to 250, until a national leopard census is completed.
- Full Text:
- Date Issued: 2012
Quantification of the cross-sectoral impacts of waterweeds and their control in Ghana
- Authors: Akpabey, Felix Jerry
- Date: 2012
- Subjects: Water hyacinth -- Control -- Environmental aspects -- Ghana Alien plants -- Research -- Ghana Introduced organisms Economic development -- Social aspects -- Research -- Ghana
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5748 , http://hdl.handle.net/10962/d1005435
- Description: The Akosombo Dam on the Volta River in Ghana was built in 1963 to provide cheap energy to fuel industry and to accelerate the economic growth of the country. It provides hydroelectric power, enhanced fishing and water transportation upstream, and improved opportunities for irrigated farming, especially in the lower reaches, and their attendant economic multiplier effects. A few years after the construction of this major dam, a rapid expansion of industrialization took place in Ghana. This brought about an exponential increase in demand for more electrical power. This led to the construction of a smaller dam at Akuse, downstream of the Akosomho Dam in 1981 and the formation of a headpond at Kpong. The impoundment of the river at the two sites (Akosombo and Kpong) caused an alteration in the existing ecological and biophysical processes in the river basin, including a slowing of the flow of the river, upstream and downstream. Changes in the natural processes, such as a reduction in the flow of the river and an increase in nutrient status of the water, resulted in an invasion of aquatic weeds, increasing the density of aquatic snails (intermediate hosts of schistosomiasis), silting and closure of the estuary, as well as other more subtle effects. The invasion of the river's main course and the dams by aquatic plants led to a corresponding reduction of navigable water both upstream and downstream. The aim of this thesis was to quantify the impact and control of waterweeds, especially water hyacinth, Eichhornia crassipes (Mart) Solms-Laubach (Pontederiaceae), in Ghana. A floral survey on the Kpong Headpond recorded 49 emergent, 12 free floating and I submerged aquatic plant species, many of which were indigenous, but the exotic or introduced water hyacinth was recorded at most of the sampling sites, and was the most abundant and had the biggest impact on the utilization of the water resource. Mats of water hyacinth served as substrates for other, indigenous species to grow out into the main channel of the headpond, including the intake point of the Kpong head works of the Ghana Water Company Limited (GWCL) and landing sites for boats. These mats resulted in a reduction of the fish (fin and shell) harvest, reducing the annual production to far below demand. Water hyacinth was also shown to have severe health implications. A survey of the Ministry of Health records showed that the prevalence of both urinary and intestinal schistosomiasis had risen significantly over time as the abundance of waterweeds, most notably water hyacinth, increased, and ranged between 70% and 75% but up to 100% in some lakeside communities. Based on the work done by an NGO on board the medical boat ("Onipa Nua "), losses in terms of money due to the effect on health of the aquatic weed infestations on the Volta River in 2006 amounted to US$ 620,000. Economic losses due to invasive alien aquatic weeds were also calculated on the Oti River Arm of Lake Volta. It was estimated that about US$2.3 million per annum would be lost to the Volta Lake Transport Company and individual boat transport operators if this section of the river were 100% covered by aquatic weeds (water hyacinth and Salvinia molesta D.S. Mitchell (Salviniaceae)). It was also estimated that US$327,038 was spent annually in monitoring and managing the weeds in the Oti River. Control interventions for aquatic weeds have been implemented in river systems in Ghana. The biological control agents Neochetina bruchi Hustache (Coleoptera, Curculionidae) and Neochetina eichhorniae Warner (Coleoptera, Curculionidae) have been used on water hyacinth infestations in the Oti River Arm of Lake Volta, the Tano River and the Lagoon complex in the south-western part of the country. Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) has been used to control salvinia, and Neohydronomous affinis Hustache (Coleoptera: Curculionidae) to control water lettuce, Pistia stratiotes Lilmaeus (Araceae) in the Tano River and Lagoon complex. Although these projects have been regarded as successful, they have relied on research from elsewhere in the world and no postrelease quantification has been conducted. In evaluating the impact of the biological control agents Neochetina bruchi and Neochetina eichhorniae weevils on water hyacinth infestations in the Tano River, fresh adult feeding scars were recorded as well as the numbers of adult weevils on each water hyacinth plant sampled at six sites. Despite being released in 1994, weevil numbers and resultant damage to plants in the Tano Lagoon was low in comparison to other regions of the world where these agents have been used. The main reason for this is that this lagoon floods seasonally, washing weevil-infested plants out to sea. Water hyacinth then re-infests the lagoon from seed and the weevil populations are low. To resolve this situation, two courses of action are proposed. The first is to mass rear the weevils along the shore of the lagoon and release them when the first seedlings recruit. The second proposal is that additional agents that have shorter lifecycies and are more mobile than the weevils should be released. To this end, the water hyacinth mirid, Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae) was imported from South Africa and released onto the Tano Lagoon in 2009. Retrospective laboratory host specificity trials were conducted on Neachetina eichharniae and Neachetina bruchi weevils 15 years after their release into Ghana to see if any variation in their host ranges had occurred. Considerable damage was inflicted on the E. crassipes leaves by the Neachetina weevils, while little feeding damage was recorded on both Heteranthera callifalia Kunth. (Pontederiaceae) and Eichharnia natans (P.Beauv.) Solms (Pontederiaceae). All the weevils introduced on H callifalia and E. natans died after the first week. This study served to confirm the host specificity and thereby the safety of these agents. Invasive alien aquatic macrophytes have negative impacts on the environment and economy of Ghana. The control of these weeds is essential to socioeconomic development and improved human health standards in riparian communities. Biological control offers a safe and sustainable control option, but requires diligent implementation. However, aquatic weed invasion is more typically a result of the anthropogenically induced eutrophication of water bodies, and this is the main issue that has to be addressed.
- Full Text:
- Date Issued: 2012
- Authors: Akpabey, Felix Jerry
- Date: 2012
- Subjects: Water hyacinth -- Control -- Environmental aspects -- Ghana Alien plants -- Research -- Ghana Introduced organisms Economic development -- Social aspects -- Research -- Ghana
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5748 , http://hdl.handle.net/10962/d1005435
- Description: The Akosombo Dam on the Volta River in Ghana was built in 1963 to provide cheap energy to fuel industry and to accelerate the economic growth of the country. It provides hydroelectric power, enhanced fishing and water transportation upstream, and improved opportunities for irrigated farming, especially in the lower reaches, and their attendant economic multiplier effects. A few years after the construction of this major dam, a rapid expansion of industrialization took place in Ghana. This brought about an exponential increase in demand for more electrical power. This led to the construction of a smaller dam at Akuse, downstream of the Akosomho Dam in 1981 and the formation of a headpond at Kpong. The impoundment of the river at the two sites (Akosombo and Kpong) caused an alteration in the existing ecological and biophysical processes in the river basin, including a slowing of the flow of the river, upstream and downstream. Changes in the natural processes, such as a reduction in the flow of the river and an increase in nutrient status of the water, resulted in an invasion of aquatic weeds, increasing the density of aquatic snails (intermediate hosts of schistosomiasis), silting and closure of the estuary, as well as other more subtle effects. The invasion of the river's main course and the dams by aquatic plants led to a corresponding reduction of navigable water both upstream and downstream. The aim of this thesis was to quantify the impact and control of waterweeds, especially water hyacinth, Eichhornia crassipes (Mart) Solms-Laubach (Pontederiaceae), in Ghana. A floral survey on the Kpong Headpond recorded 49 emergent, 12 free floating and I submerged aquatic plant species, many of which were indigenous, but the exotic or introduced water hyacinth was recorded at most of the sampling sites, and was the most abundant and had the biggest impact on the utilization of the water resource. Mats of water hyacinth served as substrates for other, indigenous species to grow out into the main channel of the headpond, including the intake point of the Kpong head works of the Ghana Water Company Limited (GWCL) and landing sites for boats. These mats resulted in a reduction of the fish (fin and shell) harvest, reducing the annual production to far below demand. Water hyacinth was also shown to have severe health implications. A survey of the Ministry of Health records showed that the prevalence of both urinary and intestinal schistosomiasis had risen significantly over time as the abundance of waterweeds, most notably water hyacinth, increased, and ranged between 70% and 75% but up to 100% in some lakeside communities. Based on the work done by an NGO on board the medical boat ("Onipa Nua "), losses in terms of money due to the effect on health of the aquatic weed infestations on the Volta River in 2006 amounted to US$ 620,000. Economic losses due to invasive alien aquatic weeds were also calculated on the Oti River Arm of Lake Volta. It was estimated that about US$2.3 million per annum would be lost to the Volta Lake Transport Company and individual boat transport operators if this section of the river were 100% covered by aquatic weeds (water hyacinth and Salvinia molesta D.S. Mitchell (Salviniaceae)). It was also estimated that US$327,038 was spent annually in monitoring and managing the weeds in the Oti River. Control interventions for aquatic weeds have been implemented in river systems in Ghana. The biological control agents Neochetina bruchi Hustache (Coleoptera, Curculionidae) and Neochetina eichhorniae Warner (Coleoptera, Curculionidae) have been used on water hyacinth infestations in the Oti River Arm of Lake Volta, the Tano River and the Lagoon complex in the south-western part of the country. Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) has been used to control salvinia, and Neohydronomous affinis Hustache (Coleoptera: Curculionidae) to control water lettuce, Pistia stratiotes Lilmaeus (Araceae) in the Tano River and Lagoon complex. Although these projects have been regarded as successful, they have relied on research from elsewhere in the world and no postrelease quantification has been conducted. In evaluating the impact of the biological control agents Neochetina bruchi and Neochetina eichhorniae weevils on water hyacinth infestations in the Tano River, fresh adult feeding scars were recorded as well as the numbers of adult weevils on each water hyacinth plant sampled at six sites. Despite being released in 1994, weevil numbers and resultant damage to plants in the Tano Lagoon was low in comparison to other regions of the world where these agents have been used. The main reason for this is that this lagoon floods seasonally, washing weevil-infested plants out to sea. Water hyacinth then re-infests the lagoon from seed and the weevil populations are low. To resolve this situation, two courses of action are proposed. The first is to mass rear the weevils along the shore of the lagoon and release them when the first seedlings recruit. The second proposal is that additional agents that have shorter lifecycies and are more mobile than the weevils should be released. To this end, the water hyacinth mirid, Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae) was imported from South Africa and released onto the Tano Lagoon in 2009. Retrospective laboratory host specificity trials were conducted on Neachetina eichharniae and Neachetina bruchi weevils 15 years after their release into Ghana to see if any variation in their host ranges had occurred. Considerable damage was inflicted on the E. crassipes leaves by the Neachetina weevils, while little feeding damage was recorded on both Heteranthera callifalia Kunth. (Pontederiaceae) and Eichharnia natans (P.Beauv.) Solms (Pontederiaceae). All the weevils introduced on H callifalia and E. natans died after the first week. This study served to confirm the host specificity and thereby the safety of these agents. Invasive alien aquatic macrophytes have negative impacts on the environment and economy of Ghana. The control of these weeds is essential to socioeconomic development and improved human health standards in riparian communities. Biological control offers a safe and sustainable control option, but requires diligent implementation. However, aquatic weed invasion is more typically a result of the anthropogenically induced eutrophication of water bodies, and this is the main issue that has to be addressed.
- Full Text:
- Date Issued: 2012
Small mammal communities at high altitude within the Sneeuberg Mountain complex, Eastern Cape Province, South Africa
- Authors: Kok, Armand du Preez
- Date: 2012
- Subjects: Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5766 , http://hdl.handle.net/10962/d1005454 , Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Description: Due to their widespread and specious nature, small mammals are ideal for biogeographical studies. Small mammals also effectively connect various trophic levels by being both consumers and prey items for other animals. The Great Escarpment is the dominant mountain landscape in South Africa. Yet, very little small mammal research has been conducted on the Great Escarpment outside of the Main Drakensberg Mountains. This is surprising given the importance of mountains in shaping regional ecology. In this study, I assessed the diversity and community composition of small mammals at three high altitude (>1700m) sites within the Sneeuberg Mountain Complex (SMC) from June 2009 to May 2010. I also tested the effectiveness of five different bait types for measuring small mammal diversity (i.e. number of individuals caught, species richness, Shannon diversity index and Simpson index of diversity). Out of a total of 423 captures, 292 individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were recorded over 5280 trap nights. The species richness and diversity of small mammals captured at the three sites were similar and this homogeneity was probably related to the regional processes (e.g. climate and latitude) that govern species richness and diversity. The most effective bait type in terms of capture success, species richness and diversity measurements was peanut butter and oats. In addition, the use of richness estimators revealed that peanut butter and oats was the most effective bait for sampling the species richness of small mammals. The effectiveness of peanut butter and oats was related to this bait having a more attractive scent, when compared to the other bait types. Future studies should focus on researching the range of local and regional processes that drive small mammal diversity at high altitudes in South Africa. I also recommend the use of more than one bait type when planning to survey small mammal communities.
- Full Text:
- Date Issued: 2012
- Authors: Kok, Armand du Preez
- Date: 2012
- Subjects: Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5766 , http://hdl.handle.net/10962/d1005454 , Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Description: Due to their widespread and specious nature, small mammals are ideal for biogeographical studies. Small mammals also effectively connect various trophic levels by being both consumers and prey items for other animals. The Great Escarpment is the dominant mountain landscape in South Africa. Yet, very little small mammal research has been conducted on the Great Escarpment outside of the Main Drakensberg Mountains. This is surprising given the importance of mountains in shaping regional ecology. In this study, I assessed the diversity and community composition of small mammals at three high altitude (>1700m) sites within the Sneeuberg Mountain Complex (SMC) from June 2009 to May 2010. I also tested the effectiveness of five different bait types for measuring small mammal diversity (i.e. number of individuals caught, species richness, Shannon diversity index and Simpson index of diversity). Out of a total of 423 captures, 292 individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were recorded over 5280 trap nights. The species richness and diversity of small mammals captured at the three sites were similar and this homogeneity was probably related to the regional processes (e.g. climate and latitude) that govern species richness and diversity. The most effective bait type in terms of capture success, species richness and diversity measurements was peanut butter and oats. In addition, the use of richness estimators revealed that peanut butter and oats was the most effective bait for sampling the species richness of small mammals. The effectiveness of peanut butter and oats was related to this bait having a more attractive scent, when compared to the other bait types. Future studies should focus on researching the range of local and regional processes that drive small mammal diversity at high altitudes in South Africa. I also recommend the use of more than one bait type when planning to survey small mammal communities.
- Full Text:
- Date Issued: 2012
Studies on existing and new isolates of Cryptophlebia leucotreta granulovirus (CrleGV) on Thaumatotibia leucotreta populations from a range of geographic regions in South Africa
- Authors: Opoku-Debrah, John Kwadwo
- Date: 2012
- Subjects: Cryptophlebia leucotreta Cryptophlebia leucotreta -- South Africa Cryptophlebia leucotreta -- Biological control Cryptophlebia leucotreta -- Life cycles Baculoviruses Lepidoptera -- Biological control Tortricidae -- Biological control Microbial insecticides Pests -- Integrated control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5778 , http://hdl.handle.net/10962/d1005466
- Description: Baculoviruses are arthropod-specific DNA viruses that are highly virulent to most lepidopteran insects. Their host specificity and compatibility with IPM programmes has enabled their usage as safe microbial insecticides (biopesticides). Two baculovirus-based biopesticides, Cryptogran and Cryptex, which have been formulated with Cryptophlebia leucotreta granulovirus (CrleGV) have been registered for the control of false codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae) in South Africa and have been successfully incorporated into IPM programmes. However, several studies have indicated that insects can develop resistance to baculovirus-based biopesticide as was shown with field populations of codling moth (CM), Cydia pomonella (L.), which developed resistance to the biopesticide Cydia pomonella granulovirus (CpGV-M) in Europe. Other studies have shown that, under laboratory conditions, FCM populations differ in their susceptibility to Cryptogran and Cryptex. In order to investigate difference in susceptibility as well as protect against any future resistance by FCM to Cryptogran and Cryptex, a search for novel CrleGV-SA isolates from diseased insects from different geographic regions in South Africa was performed. Six geographic populations (Addo, Citrusdal, Marble Hall, Nelspruit, Baths and Mixed colonies) of FCM were established and maintained in the laboratory. Studies on the comparative biological performance based on pupal mass, female fecundity, egg hatch, pupal survival, adult eclosion and duration of life cycle of the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies revealed a low biological performance for the Citrusdal colony. This was attributed to the fact that FCM populations found in the Citrusdal area are not indigenous and may have been introduced from a very limited gene pool from another region. When insects from five colonies, excluding the Baths colony, were subjected to stress by overcrowding , a latent baculovirus resident in the Addo, Nelspruit, Citrusdal, Marble Hall and Mixed colonies was brought into an overt lethal state. Transmission electron micrographs revealed the presence of GV occlusion bodies (OBs) in diseased insects. DNA profiles obtained by single restriction endonuclease analysis of viral genomic DNA using BamH 1, Sa/1, Xba1 , Pst1, Xh01 , Kpn1, Hindlll and EcoR1 revealed five CrleGV-SA isolates latent within the insect populations. The new isolates were named CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl, CrleGVSA Nels and CrleGV-SA Mix isolates. The novelty of the five CrleGV-SA isolates was confirmed by the presence of unique submolar bands, indicating that each isolate was genetically different. PCR amplification and sequencing of the granulin and egt genes from the five isolates revealed several single nucleotide polymorph isms (SNPs) which, in some cases, resulted in amino acid substitutions. DNA profiles from RFLPs, as well as phylogenetic analysis based on granulin and egt sequencing showed the presence of two CrleGV-SA genome types for the CrleGV-SA isolate. Cryptex and CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl and CrleGV-SA Mix were placed as members of Group one CrleGV-SA, and Cryptogran and CrleGV-SA Nels isolate were placed into Group two CrleGV-SA. In droplet feeding bioassays, the median survival time (STso) for neonate larvae inoculated with Group one and two CrleGV-SA were determined to range from 80 - 88 hours (3.33 - 3.67 days), for all five colonies. LDso values for Group one and two CrleGV-SA against neonates from the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies varied between some populations and ranged from 0.80 - 3.12 OBs per larva, indicating some level of variation in host susceptibility. This is the first study reporting the existence of genetically distinct CrleGV baculovirus isolates infecting FCM in different geographical areas of South Africa. The results of this study have broad-ranging implications for our understanding of baculovirus-host interactions and for the application of baculovirus basedbiopesticides.
- Full Text:
- Date Issued: 2012
- Authors: Opoku-Debrah, John Kwadwo
- Date: 2012
- Subjects: Cryptophlebia leucotreta Cryptophlebia leucotreta -- South Africa Cryptophlebia leucotreta -- Biological control Cryptophlebia leucotreta -- Life cycles Baculoviruses Lepidoptera -- Biological control Tortricidae -- Biological control Microbial insecticides Pests -- Integrated control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5778 , http://hdl.handle.net/10962/d1005466
- Description: Baculoviruses are arthropod-specific DNA viruses that are highly virulent to most lepidopteran insects. Their host specificity and compatibility with IPM programmes has enabled their usage as safe microbial insecticides (biopesticides). Two baculovirus-based biopesticides, Cryptogran and Cryptex, which have been formulated with Cryptophlebia leucotreta granulovirus (CrleGV) have been registered for the control of false codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae) in South Africa and have been successfully incorporated into IPM programmes. However, several studies have indicated that insects can develop resistance to baculovirus-based biopesticide as was shown with field populations of codling moth (CM), Cydia pomonella (L.), which developed resistance to the biopesticide Cydia pomonella granulovirus (CpGV-M) in Europe. Other studies have shown that, under laboratory conditions, FCM populations differ in their susceptibility to Cryptogran and Cryptex. In order to investigate difference in susceptibility as well as protect against any future resistance by FCM to Cryptogran and Cryptex, a search for novel CrleGV-SA isolates from diseased insects from different geographic regions in South Africa was performed. Six geographic populations (Addo, Citrusdal, Marble Hall, Nelspruit, Baths and Mixed colonies) of FCM were established and maintained in the laboratory. Studies on the comparative biological performance based on pupal mass, female fecundity, egg hatch, pupal survival, adult eclosion and duration of life cycle of the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies revealed a low biological performance for the Citrusdal colony. This was attributed to the fact that FCM populations found in the Citrusdal area are not indigenous and may have been introduced from a very limited gene pool from another region. When insects from five colonies, excluding the Baths colony, were subjected to stress by overcrowding , a latent baculovirus resident in the Addo, Nelspruit, Citrusdal, Marble Hall and Mixed colonies was brought into an overt lethal state. Transmission electron micrographs revealed the presence of GV occlusion bodies (OBs) in diseased insects. DNA profiles obtained by single restriction endonuclease analysis of viral genomic DNA using BamH 1, Sa/1, Xba1 , Pst1, Xh01 , Kpn1, Hindlll and EcoR1 revealed five CrleGV-SA isolates latent within the insect populations. The new isolates were named CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl, CrleGVSA Nels and CrleGV-SA Mix isolates. The novelty of the five CrleGV-SA isolates was confirmed by the presence of unique submolar bands, indicating that each isolate was genetically different. PCR amplification and sequencing of the granulin and egt genes from the five isolates revealed several single nucleotide polymorph isms (SNPs) which, in some cases, resulted in amino acid substitutions. DNA profiles from RFLPs, as well as phylogenetic analysis based on granulin and egt sequencing showed the presence of two CrleGV-SA genome types for the CrleGV-SA isolate. Cryptex and CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl and CrleGV-SA Mix were placed as members of Group one CrleGV-SA, and Cryptogran and CrleGV-SA Nels isolate were placed into Group two CrleGV-SA. In droplet feeding bioassays, the median survival time (STso) for neonate larvae inoculated with Group one and two CrleGV-SA were determined to range from 80 - 88 hours (3.33 - 3.67 days), for all five colonies. LDso values for Group one and two CrleGV-SA against neonates from the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies varied between some populations and ranged from 0.80 - 3.12 OBs per larva, indicating some level of variation in host susceptibility. This is the first study reporting the existence of genetically distinct CrleGV baculovirus isolates infecting FCM in different geographical areas of South Africa. The results of this study have broad-ranging implications for our understanding of baculovirus-host interactions and for the application of baculovirus basedbiopesticides.
- Full Text:
- Date Issued: 2012
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
The diet of black-backed jackal (Canis Mesomelas) on two contrasting land-use types in the Eastern Cape Province, South Africa and the validation of a new analytical method of mammalian hair identification
- Authors: Forbes, Ross William
- Date: 2012
- Subjects: Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Mammals -- Identification
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5661 , http://hdl.handle.net/10962/d1005345 , Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Mammals -- Identification
- Description: Diet assessments are critical for understanding the foraging behaviour, habitat use and trophic separation of mammalian predators and are vital for gaining insight into how predators influence prey populations. The aim of this research was to qualitatively describe the diet of black-backed jackals (Canis mesomelas, Schreber 1775) using scat analysis on two contrasting land-use types in the Eastern Cape Province, South Africa. Scats were collected on a monthly basis from November 2009 to October 2010 from two game reserves (Great Fish River Reserve and Shamwari Private Game Reserve) and two neighbouring livestock farms. The relative frequency of occurrence of mammal hair (33 – 47 %) and vegetation (32 – 45%)dominated jackal diet throughout the year across the four study sites. Other important prey items included invertebrates (8 – 21 %) and fruit and seeds (3 – 11 %). Birds and reptiles constituted ≤ 2 % of the diet and were only recorded on the game reserves. Significant seasonal dietary shifts were observed on the game reserves but not on the farms. Fruit and seeds were significantly more frequent in the diet during autumn at Great Fish River Reserve and invertebrates were significantly less common in the diet during winter on both reserves. In addition, vegetation was significantly more common in the diet during winter at Shamwari Private Game Reserve. The significant temporal variation of certain prey items is testament to black-backed jackals being opportunistic generalists, foraging on those food items which are most abundant, accessible and energetically beneficial. Land-use type also influenced the diet of black-backed jackals with significantly more invertebrates and, fruit and seeds being recorded on the game reserves than on the farms. By contrast, significantly more mammal hair and vegetation were present in the diet on the farms compared with the game reserves. The mammalian component of the diet was dominated by ruminants and rodents on the game reserves and by ruminants and livestock on the farms. The presence of livestock in the diet of black-backed jackals on the farms highlights their potential impact on the livestock industry in the region and may assist farmers in determining which predators are responsible for stock loss. Previous approaches for identifying mammalian hairs from predator scats have utilised dichotomous keys and reference collections but these are often time-consuming and require a trained individual to carry out the identification. Thus, I also tested the efficacy of an automated pattern recognition programme (HairSnap) for identifying mammalian hairs from black-backed jackal scats. The overall accuracy of the programme was 38 % with black-backed jackal, Greater kudu (Tragelaphus strepsiceros) and striped polecat (Ictonyx striatus) hairs being accurately identified more often (70 – 80 %) than any other species tested. It is likely that both the size and species composition of the sample resulted in the poor accuracy of the programme. However, with the implementation of several improvement measures (e.g. adjustment of the algorithm) the programme may offer a superior, bias-free method of mammalian hair identification. The dietary information gathered here furthers our knowledge of the biology of the blackbacked jackals, especially in the locally important thicket biome. Moreover, understanding their foraging habits allows for more effective management of the species on both game reserves and farmlands. I recommend that future research should focus on quantitatively assessing the diet of black-backed jackals in the Eastern Cape Province and elsewhere. This will compliment the dietary description provided in this study and may offer a biologically more meaningful indication of the relative importance of the prey items.
- Full Text:
- Date Issued: 2012
- Authors: Forbes, Ross William
- Date: 2012
- Subjects: Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Mammals -- Identification
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5661 , http://hdl.handle.net/10962/d1005345 , Black-backed jackal -- South Africa -- Eastern Cape , Jackals -- South Africa -- Eastern Cape , Jackals -- Food , Mammals -- Identification
- Description: Diet assessments are critical for understanding the foraging behaviour, habitat use and trophic separation of mammalian predators and are vital for gaining insight into how predators influence prey populations. The aim of this research was to qualitatively describe the diet of black-backed jackals (Canis mesomelas, Schreber 1775) using scat analysis on two contrasting land-use types in the Eastern Cape Province, South Africa. Scats were collected on a monthly basis from November 2009 to October 2010 from two game reserves (Great Fish River Reserve and Shamwari Private Game Reserve) and two neighbouring livestock farms. The relative frequency of occurrence of mammal hair (33 – 47 %) and vegetation (32 – 45%)dominated jackal diet throughout the year across the four study sites. Other important prey items included invertebrates (8 – 21 %) and fruit and seeds (3 – 11 %). Birds and reptiles constituted ≤ 2 % of the diet and were only recorded on the game reserves. Significant seasonal dietary shifts were observed on the game reserves but not on the farms. Fruit and seeds were significantly more frequent in the diet during autumn at Great Fish River Reserve and invertebrates were significantly less common in the diet during winter on both reserves. In addition, vegetation was significantly more common in the diet during winter at Shamwari Private Game Reserve. The significant temporal variation of certain prey items is testament to black-backed jackals being opportunistic generalists, foraging on those food items which are most abundant, accessible and energetically beneficial. Land-use type also influenced the diet of black-backed jackals with significantly more invertebrates and, fruit and seeds being recorded on the game reserves than on the farms. By contrast, significantly more mammal hair and vegetation were present in the diet on the farms compared with the game reserves. The mammalian component of the diet was dominated by ruminants and rodents on the game reserves and by ruminants and livestock on the farms. The presence of livestock in the diet of black-backed jackals on the farms highlights their potential impact on the livestock industry in the region and may assist farmers in determining which predators are responsible for stock loss. Previous approaches for identifying mammalian hairs from predator scats have utilised dichotomous keys and reference collections but these are often time-consuming and require a trained individual to carry out the identification. Thus, I also tested the efficacy of an automated pattern recognition programme (HairSnap) for identifying mammalian hairs from black-backed jackal scats. The overall accuracy of the programme was 38 % with black-backed jackal, Greater kudu (Tragelaphus strepsiceros) and striped polecat (Ictonyx striatus) hairs being accurately identified more often (70 – 80 %) than any other species tested. It is likely that both the size and species composition of the sample resulted in the poor accuracy of the programme. However, with the implementation of several improvement measures (e.g. adjustment of the algorithm) the programme may offer a superior, bias-free method of mammalian hair identification. The dietary information gathered here furthers our knowledge of the biology of the blackbacked jackals, especially in the locally important thicket biome. Moreover, understanding their foraging habits allows for more effective management of the species on both game reserves and farmlands. I recommend that future research should focus on quantitatively assessing the diet of black-backed jackals in the Eastern Cape Province and elsewhere. This will compliment the dietary description provided in this study and may offer a biologically more meaningful indication of the relative importance of the prey items.
- Full Text:
- Date Issued: 2012
The dispersal of African wild dogs (Lycaon Pictus) from protected areas in the Northern KwaZulu‐Natal Province, South Africa.
- Whittington‐Jones, Brendan Mark
- Authors: Whittington‐Jones, Brendan Mark
- Date: 2012
- Subjects: African wild dog , African wild dog -- Conservation -- South Africa -- KwazuluNatal , African wild dog -- Dispersal -- South Africa -- KwaZulu-Natal , African wild dog -- Effect of human beings on -- South Africa -- KwaZulu Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5893 , http://hdl.handle.net/10962/d1013414
- Description: The number of African wild dogs Lycaon pictus in Northern KwaZulu‐Natal, South Africa has increased substantially over the last six years. This is largely due to a managed metapopulation approach of introductions onto protected areas and private game reserves since 1998. Because of the increasing wild dog population, the likelihood of rural communities surrounding protected areas encountering dispersing wild dogs in northern KwaZulu‐Natal has also increased. Resident wild dog populations currently occur in Hluhluwe‐iMfolozi Park (HiP), Mkhuze Game Reserve (MGR) of Isimangaliso Wetland Park and Thanda Private Game Reserve (TPGR) all of which are bordered by a matrix of natural habitats and human settlements. Thus, land outside these protected areas could be utilized to expand wild dog distribution and provide connectivity between existing resident populations of wild dogs within KwaZulu‐Natal. To investigate the viability of such an approach, Maximum Entropy Modelling (Maxent) was used to characterize habitat niche selection of dispersing wild dogs, and to identify potential dispersal linkages between current wild dog metapopulation reserves. The model was calibrated using 132 location points collected from 2006 until 2009. From 2008 to 2009 I also conducted a survey of 247 community members in tribal authorities bordering HiP and MGR, to understand factors influencing attitudes towards wild dogs. A habitat suitability model with seven predictor variables had an AUC of 0.96 (SD = 0.02) and indicated four variables which best predicted probability of presence for dispersing wild dogs: elevation, road density, land cover and human density. The results suggest that elevation and land cover may be of greater influence for dispersing wild dogs than human density or activity. Elevation was the single most effective variable indicating a higher probability of presence for dispersing wild dogs in lower lying locations; peaking at approximately 200 – 300m a.s.l. Wild dogs also showed a preference for Woodland and Bushland habitats which in KwaZulu‐Natal tend to be found on lower lying topography. A preference for areas of lower human density and a highest probability of presence at road densities of approximately 0.7km/km2 or less would suggest that while wild dogs may show a tendency to avoid areas of high human activity, they can coexist in close proximity to humans. Respondent’s attitudes, knowledge of wild dogs and livestock husbandry were interpreted by the development of a set of indices. Attitudes were positively related to formal education levels and wild dog‐specific education, but were not influenced by demographic factors such as gender, age and employment status. Eighty three percent of respondents believed efforts to protect wild dogs should continue. Respondents with higher numbers of livestock tended to have more positive attitudes towards wild dogs despite generally incurring higher losses to carnivore depredation than those with less livestock. This appears to be because the financial burden of livestock losses to those with fewer livestock is perceived to be a loss of a greater proportion of total financial wealth. The study highlighted the substantial scope for improvement in livestock management. Theft (34 percent), drought (30 percent) and disease (14 percent) were ranked as the greatest problems facing livestock owners while predators were ranked as the greatest problem by only 4 percent of respondents. My findings suggest that wild dogs are generally viewed positively or with ambivalence. Concerns over the potentially increasing threat to livestock, as natural prey numbers outside protected areas decline and wild dogs disperse from natal packs, are likely to be manageable. However, wild dog population expansion within KwaZulu‐Natal will continue to rely on managed core populations on perimeter‐fenced metapopulation reserves with tolerant communities and landowners contributing to the connectivity of isolated reserves. Generation of tolerance can be instilled through continued advocacy and education, supported by conflict mitigation initiatives and rapid response to conflict reports. The implementation of incentive schemes for adjoining private landowners to co‐manage wild dog populations will need to be addressed in conjunction with managed metapopulation practices and law enforcement, to promote range expansion, and reduce potentially lethal edge effects and wild dog‐human conflict.
- Full Text:
- Date Issued: 2012
- Authors: Whittington‐Jones, Brendan Mark
- Date: 2012
- Subjects: African wild dog , African wild dog -- Conservation -- South Africa -- KwazuluNatal , African wild dog -- Dispersal -- South Africa -- KwaZulu-Natal , African wild dog -- Effect of human beings on -- South Africa -- KwaZulu Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5893 , http://hdl.handle.net/10962/d1013414
- Description: The number of African wild dogs Lycaon pictus in Northern KwaZulu‐Natal, South Africa has increased substantially over the last six years. This is largely due to a managed metapopulation approach of introductions onto protected areas and private game reserves since 1998. Because of the increasing wild dog population, the likelihood of rural communities surrounding protected areas encountering dispersing wild dogs in northern KwaZulu‐Natal has also increased. Resident wild dog populations currently occur in Hluhluwe‐iMfolozi Park (HiP), Mkhuze Game Reserve (MGR) of Isimangaliso Wetland Park and Thanda Private Game Reserve (TPGR) all of which are bordered by a matrix of natural habitats and human settlements. Thus, land outside these protected areas could be utilized to expand wild dog distribution and provide connectivity between existing resident populations of wild dogs within KwaZulu‐Natal. To investigate the viability of such an approach, Maximum Entropy Modelling (Maxent) was used to characterize habitat niche selection of dispersing wild dogs, and to identify potential dispersal linkages between current wild dog metapopulation reserves. The model was calibrated using 132 location points collected from 2006 until 2009. From 2008 to 2009 I also conducted a survey of 247 community members in tribal authorities bordering HiP and MGR, to understand factors influencing attitudes towards wild dogs. A habitat suitability model with seven predictor variables had an AUC of 0.96 (SD = 0.02) and indicated four variables which best predicted probability of presence for dispersing wild dogs: elevation, road density, land cover and human density. The results suggest that elevation and land cover may be of greater influence for dispersing wild dogs than human density or activity. Elevation was the single most effective variable indicating a higher probability of presence for dispersing wild dogs in lower lying locations; peaking at approximately 200 – 300m a.s.l. Wild dogs also showed a preference for Woodland and Bushland habitats which in KwaZulu‐Natal tend to be found on lower lying topography. A preference for areas of lower human density and a highest probability of presence at road densities of approximately 0.7km/km2 or less would suggest that while wild dogs may show a tendency to avoid areas of high human activity, they can coexist in close proximity to humans. Respondent’s attitudes, knowledge of wild dogs and livestock husbandry were interpreted by the development of a set of indices. Attitudes were positively related to formal education levels and wild dog‐specific education, but were not influenced by demographic factors such as gender, age and employment status. Eighty three percent of respondents believed efforts to protect wild dogs should continue. Respondents with higher numbers of livestock tended to have more positive attitudes towards wild dogs despite generally incurring higher losses to carnivore depredation than those with less livestock. This appears to be because the financial burden of livestock losses to those with fewer livestock is perceived to be a loss of a greater proportion of total financial wealth. The study highlighted the substantial scope for improvement in livestock management. Theft (34 percent), drought (30 percent) and disease (14 percent) were ranked as the greatest problems facing livestock owners while predators were ranked as the greatest problem by only 4 percent of respondents. My findings suggest that wild dogs are generally viewed positively or with ambivalence. Concerns over the potentially increasing threat to livestock, as natural prey numbers outside protected areas decline and wild dogs disperse from natal packs, are likely to be manageable. However, wild dog population expansion within KwaZulu‐Natal will continue to rely on managed core populations on perimeter‐fenced metapopulation reserves with tolerant communities and landowners contributing to the connectivity of isolated reserves. Generation of tolerance can be instilled through continued advocacy and education, supported by conflict mitigation initiatives and rapid response to conflict reports. The implementation of incentive schemes for adjoining private landowners to co‐manage wild dog populations will need to be addressed in conjunction with managed metapopulation practices and law enforcement, to promote range expansion, and reduce potentially lethal edge effects and wild dog‐human conflict.
- Full Text:
- Date Issued: 2012
The feeding and spatial ecology of cheetahs (Acinonyx jubatus) and lions (Panthera leo) in the Little Karoo, South Africa
- Authors: Vorster, Paul Hendrik
- Date: 2012
- Subjects: Sanbona Wildlife Reserve , Cheetah -- South Africa -- Little Karoo , Lion -- South Africa -- Little Karoo , Cheetah -- Behavior -- South Africa -- Little Karoo , Lion -- Behavior -- South Africa -- Little Karoo , Cheetah -- Food -- South Africa -- Little Karoo , Lion -- Food -- South Africa -- Little Karoo , Spatial behavior in animals , Predation (Biology) , Game reserves -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5693 , http://hdl.handle.net/10962/d1005379 , Sanbona Wildlife Reserve , Cheetah -- South Africa -- Little Karoo , Lion -- South Africa -- Little Karoo , Cheetah -- Behavior -- South Africa -- Little Karoo , Lion -- Behavior -- South Africa -- Little Karoo , Cheetah -- Food -- South Africa -- Little Karoo , Lion -- Food -- South Africa -- Little Karoo , Spatial behavior in animals , Predation (Biology) , Game reserves -- Management
- Description: The re-introduction of large carnivores into relatively small conservation areas that fall within the historic distribution range of the species is becoming an increasingly common occurrence. The success of such re-introductions depends very much on the quality of the information that is available to guide management decisions, but in many cases, little information is available. The re-introduction of lions and cheetahs to Sanbona created the opportunity to monitor the behaviour of re-introduced predators to a relatively large system that was characterised by a low ungulate stocking density and little standing water. The broad aims were to study the feeding and spatial ecologies of the lions and cheetahs, to collect standard base-line data, and to examine the effects of the low prey density and limited standing water on habitat selection, range size and diet. The diet (data collected from direct observation and faecal analysis) was similar to that reported in previous studies, and lions and cheetahs preferred greater kudu, black wildebeest and springbok. Lions preferred medium to large prey items, and cheetahs preferred medium to small prey items. The hilly and mountainous terrain of much of the reserve meant that only 50% of the total space was available to the predators. Home ranges of most of the predators were focused around the single large body of standing water. This is likely to have been a response to the water, the vegetation, and the prey that was attracted to these. Habitat selection was also influenced by inter and intra-specific interactions at least for a solitary male lion and female cheetahs. Range sizes were larger than on some other reserves and it is suggested that this was a result of the low prey density. These results form the basis for management recommendations including the importance of continuing to monitor the system and opening up additional parts of the reserve to the predators.
- Full Text:
- Date Issued: 2012
- Authors: Vorster, Paul Hendrik
- Date: 2012
- Subjects: Sanbona Wildlife Reserve , Cheetah -- South Africa -- Little Karoo , Lion -- South Africa -- Little Karoo , Cheetah -- Behavior -- South Africa -- Little Karoo , Lion -- Behavior -- South Africa -- Little Karoo , Cheetah -- Food -- South Africa -- Little Karoo , Lion -- Food -- South Africa -- Little Karoo , Spatial behavior in animals , Predation (Biology) , Game reserves -- Management
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5693 , http://hdl.handle.net/10962/d1005379 , Sanbona Wildlife Reserve , Cheetah -- South Africa -- Little Karoo , Lion -- South Africa -- Little Karoo , Cheetah -- Behavior -- South Africa -- Little Karoo , Lion -- Behavior -- South Africa -- Little Karoo , Cheetah -- Food -- South Africa -- Little Karoo , Lion -- Food -- South Africa -- Little Karoo , Spatial behavior in animals , Predation (Biology) , Game reserves -- Management
- Description: The re-introduction of large carnivores into relatively small conservation areas that fall within the historic distribution range of the species is becoming an increasingly common occurrence. The success of such re-introductions depends very much on the quality of the information that is available to guide management decisions, but in many cases, little information is available. The re-introduction of lions and cheetahs to Sanbona created the opportunity to monitor the behaviour of re-introduced predators to a relatively large system that was characterised by a low ungulate stocking density and little standing water. The broad aims were to study the feeding and spatial ecologies of the lions and cheetahs, to collect standard base-line data, and to examine the effects of the low prey density and limited standing water on habitat selection, range size and diet. The diet (data collected from direct observation and faecal analysis) was similar to that reported in previous studies, and lions and cheetahs preferred greater kudu, black wildebeest and springbok. Lions preferred medium to large prey items, and cheetahs preferred medium to small prey items. The hilly and mountainous terrain of much of the reserve meant that only 50% of the total space was available to the predators. Home ranges of most of the predators were focused around the single large body of standing water. This is likely to have been a response to the water, the vegetation, and the prey that was attracted to these. Habitat selection was also influenced by inter and intra-specific interactions at least for a solitary male lion and female cheetahs. Range sizes were larger than on some other reserves and it is suggested that this was a result of the low prey density. These results form the basis for management recommendations including the importance of continuing to monitor the system and opening up additional parts of the reserve to the predators.
- Full Text:
- Date Issued: 2012
The trophic ecology of parrotfish of Zanzibar application of stable isotope analysis
- Plass-Johnson, Jeremiah Grahm
- Authors: Plass-Johnson, Jeremiah Grahm
- Date: 2012
- Subjects: Parrotfishes -- Tanzania -- Zanzibar , Parrotfishes , Parrotfishes -- Ecology -- Tanzania -- Zanzibar , Parrotfishes -- Behavior -- Tanzania -- Zanzibar , Parrotfishes -- Food -- Tanzania -- Zanzibar , Scleractinia -- Tanzania -- Zanzibar , Algae -- Tanzania -- Zanzibar , Coral reefs and islands -- Tanzania -- Zanzibar , Coral reef fishes -- Tanzania -- Zanzibar , Stable isotopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5789 , http://hdl.handle.net/10962/d1005477 , Parrotfishes -- Tanzania -- Zanzibar , Parrotfishes , Parrotfishes -- Ecology -- Tanzania -- Zanzibar , Parrotfishes -- Behavior -- Tanzania -- Zanzibar , Parrotfishes -- Food -- Tanzania -- Zanzibar , Scleractinia -- Tanzania -- Zanzibar , Algae -- Tanzania -- Zanzibar , Coral reefs and islands -- Tanzania -- Zanzibar , Coral reef fishes -- Tanzania -- Zanzibar , Stable isotopes
- Description: Parrotfish are a critical component of the herbivore functional group on tropical coral reefs around the world because they mediate competition that occurs between algae and scleractinian corals. Also, because of their feeding technique, which consists of rasping at the substratum with their beak-like teeth, they play an important role in carbonate turnover and the clearing of reef surface area for the settlement of new sessile organisms. Because of these roles, parrotfishes are an important structuring component of coral reef communities. However, individual species can play different roles depending on their physiology, behaviour and ecology. Despite the possible ecological differences that may exist amongst species, specific roles of the fishes remain unclear as the group is most often studied at higher community levels. This thesis applied stable isotope analysis to differing levels of organisation within a parrotfish community to help elucidate their trophic ecology on coral reefs in Zanzibar. Firstly, blood and muscle tissues were compared to identify differences in their isotope signatures. In other organisms, blood turns over faster than muscle tissue so that muscle tissue represents the diet as integrated over a longer period of time. In most species of parrotfish the blood and muscle δ¹³C signatures were not found to be significantly different, but the δ¹⁵N signatures were significantly different between tissues. This indicated that the δ¹³C signature of both tissues would reveal similar dietary information. Conversely, differences in the δ¹⁵N signature indicated that the nitrogen relationship between tissues was more complicated. Secondly, spatial variability in parrotfish, coral, detritus and macroalgae isotope signatures was assessed at different scales. In macroalgae and coral tissues (zooxanthellae and polyp treated separately), the δ¹³C signatures were shown to differ with depth, presumably because of changes in photosynthetic processes related to depth-associated changes in light. While δ¹⁵N signatures were not affected by depth, all organisms showed enrichment at the Nyange reef, the closest reef to the capital of Zanzibar, Stone Town, presumably reflecting the effects of sewage outfall. These results show that processes that impact the δ¹⁵N signatures of primary producers (macroalgae and zooxanthellae) can be traced to higher trophic levels (coral polyps and fish). Lastly, δ¹³C and δ¹⁵N signatures were used to identify ontogenetic dietary changes in multiple species of parrotfish. Four of the species showed stages that varied from the diets that are normally assumed on the basis of their dentition and feeding technique. This indicates that functional roles based on taxonomy or morphology may fail to include possible ontogenetic dietary changes, and may also fail to elucidate the full impact a species could have on coral reef communities. The conclusions from these studies indicate that the species-specific ecological role of parrotfish in coral reef communities can be complex within and between species, and may differ amongst reefs. In light of the natural and anthropogenic pressures that affect coral reef systems, management decisions based on a more complete understanding of the role of these fish in coral reef communities will help decisions that maintain resilience in these fragile systems.
- Full Text:
- Date Issued: 2012
- Authors: Plass-Johnson, Jeremiah Grahm
- Date: 2012
- Subjects: Parrotfishes -- Tanzania -- Zanzibar , Parrotfishes , Parrotfishes -- Ecology -- Tanzania -- Zanzibar , Parrotfishes -- Behavior -- Tanzania -- Zanzibar , Parrotfishes -- Food -- Tanzania -- Zanzibar , Scleractinia -- Tanzania -- Zanzibar , Algae -- Tanzania -- Zanzibar , Coral reefs and islands -- Tanzania -- Zanzibar , Coral reef fishes -- Tanzania -- Zanzibar , Stable isotopes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5789 , http://hdl.handle.net/10962/d1005477 , Parrotfishes -- Tanzania -- Zanzibar , Parrotfishes , Parrotfishes -- Ecology -- Tanzania -- Zanzibar , Parrotfishes -- Behavior -- Tanzania -- Zanzibar , Parrotfishes -- Food -- Tanzania -- Zanzibar , Scleractinia -- Tanzania -- Zanzibar , Algae -- Tanzania -- Zanzibar , Coral reefs and islands -- Tanzania -- Zanzibar , Coral reef fishes -- Tanzania -- Zanzibar , Stable isotopes
- Description: Parrotfish are a critical component of the herbivore functional group on tropical coral reefs around the world because they mediate competition that occurs between algae and scleractinian corals. Also, because of their feeding technique, which consists of rasping at the substratum with their beak-like teeth, they play an important role in carbonate turnover and the clearing of reef surface area for the settlement of new sessile organisms. Because of these roles, parrotfishes are an important structuring component of coral reef communities. However, individual species can play different roles depending on their physiology, behaviour and ecology. Despite the possible ecological differences that may exist amongst species, specific roles of the fishes remain unclear as the group is most often studied at higher community levels. This thesis applied stable isotope analysis to differing levels of organisation within a parrotfish community to help elucidate their trophic ecology on coral reefs in Zanzibar. Firstly, blood and muscle tissues were compared to identify differences in their isotope signatures. In other organisms, blood turns over faster than muscle tissue so that muscle tissue represents the diet as integrated over a longer period of time. In most species of parrotfish the blood and muscle δ¹³C signatures were not found to be significantly different, but the δ¹⁵N signatures were significantly different between tissues. This indicated that the δ¹³C signature of both tissues would reveal similar dietary information. Conversely, differences in the δ¹⁵N signature indicated that the nitrogen relationship between tissues was more complicated. Secondly, spatial variability in parrotfish, coral, detritus and macroalgae isotope signatures was assessed at different scales. In macroalgae and coral tissues (zooxanthellae and polyp treated separately), the δ¹³C signatures were shown to differ with depth, presumably because of changes in photosynthetic processes related to depth-associated changes in light. While δ¹⁵N signatures were not affected by depth, all organisms showed enrichment at the Nyange reef, the closest reef to the capital of Zanzibar, Stone Town, presumably reflecting the effects of sewage outfall. These results show that processes that impact the δ¹⁵N signatures of primary producers (macroalgae and zooxanthellae) can be traced to higher trophic levels (coral polyps and fish). Lastly, δ¹³C and δ¹⁵N signatures were used to identify ontogenetic dietary changes in multiple species of parrotfish. Four of the species showed stages that varied from the diets that are normally assumed on the basis of their dentition and feeding technique. This indicates that functional roles based on taxonomy or morphology may fail to include possible ontogenetic dietary changes, and may also fail to elucidate the full impact a species could have on coral reef communities. The conclusions from these studies indicate that the species-specific ecological role of parrotfish in coral reef communities can be complex within and between species, and may differ amongst reefs. In light of the natural and anthropogenic pressures that affect coral reef systems, management decisions based on a more complete understanding of the role of these fish in coral reef communities will help decisions that maintain resilience in these fragile systems.
- Full Text:
- Date Issued: 2012
Trophic ecology of breeding northern rockhopper penguins, Eudyptes Moseleyi, at Tristan da Cunha, South Atlantic Ocean
- Authors: Booth, Jenny Marie
- Date: 2012
- Subjects: Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5788 , http://hdl.handle.net/10962/d1005476 , Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Description: Northern Rockhopper penguin populations, Eudyptes moseleyi, are declining globally, and at Tristan da Cunha have undergone severe declines (> 90% in the last 130 years), the cause(s)of which are unknown. There is a paucity of data on this species in the South Atlantic Ocean, therefore their trophic ecology at Tristan da Cunha was studied, specifically focusing on diet, using stomach content analysis and stable isotope analysis (SIA), in conjunction with an analysis of diving behaviour, assessed using temperature-depth recorders. In order to evaluate the influence of gender on foraging, a morphometric investigation of sexual dimorphism was confirmed using molecular analysis. Additionally, plasma corticosterone levels were measured to examine breeding stage and presence of blood parasites as potential sources of stress during the breeding season. Northern Rockhopper penguins at Tristan da Cunha displayed a high degree of foraging plasticity, and fed opportunistically on a wide variety of prey, probably reflecting local small-scale changes in prey distribution. Zooplankton dominated (by mass) the diet of guard stage females, whereas small meso-pelagic fish (predominantly Photichthyidae)dominated diet of adults of both sexes in the crèche stage, with cephalopods contributing equally in both stages. Adults consistently fed chicks on lower-trophic level prey (assessed using SIA), probably zooplankton, than they consumed themselves indicating that the increasing demands of growing chicks were not met by adults through provisioning of higher- quality prey. SIA also indicated that adults foraged in different oceanic water masses when feeding for self-maintenance and for chick provisioning, thus temporally segregating the prey consumed for different purposes. It is possible that adults ‘selected’ these higher quality prey for themselves, or this may be a reflection of opportunistic behaviour. At Tristan da Cunha sexual dimorphism was observed in culmen dimensions (length, depth, width), with males having larger beaks and feeding on larger individuals of squid and fish than females. No sexual segregation in terms of foraging habitat (i.e. different water masses, based on ð¹³N or trophic level ð¹⁵N) during the breeding season or pre-moult period was revealed through SIA, and stomach content analysis revealed no sexual differences in prey species targeted. The results of SIA of feathers indicate that during the pre-moult period birds foraged in different water masses than during the breeding period. The fact that throughout the breeding season birds foraged in similar habitats suggests no intra-specific competition, despite both sexes feeding on the same prey.Birds were generally diurnal, daily foragers (12 – 16 hr trips), with extended trips (maximum duration 35.5 hours) and nocturnal diving recorded in a few individuals. Birds dived well within their physiological limits, predominantly utilising the upper 20m of the water column, employing two different strategies to target different prey items. Long, deep (30 – 40 m), energetically costly dives were performed when targeting energy-rich prey (fish), and a greater number of shorter, shallower (5 – 20 m), energy-efficient dives were performed when targeting prey with a lower energy content (zooplankton). More than half of the sampled study population were infected with the intra-cellular blood parasite Babesia, but infection showed no relationship to body mass, corticosterone levels or breeding success. Fasting birds showed no signs of elevated corticosterone levels, suggesting they had acquired sufficient fat reserves prior to breeding. Failed breeders did not exhibit elevated corticosterone levels. Tristan skuas, Catharacta antarctica hamiltoni, were observed to be a significant cause of egg and chick mortality. The absence of sex-based differences in foraging, and the absence of any signs of stress in relation to body mass, presence of Babesia or breeding stage, suggest that there are no obvious signs of high levels of stress or food limitations during breeding at Tristan da Cunha.
- Full Text:
- Date Issued: 2012
- Authors: Booth, Jenny Marie
- Date: 2012
- Subjects: Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5788 , http://hdl.handle.net/10962/d1005476 , Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Description: Northern Rockhopper penguin populations, Eudyptes moseleyi, are declining globally, and at Tristan da Cunha have undergone severe declines (> 90% in the last 130 years), the cause(s)of which are unknown. There is a paucity of data on this species in the South Atlantic Ocean, therefore their trophic ecology at Tristan da Cunha was studied, specifically focusing on diet, using stomach content analysis and stable isotope analysis (SIA), in conjunction with an analysis of diving behaviour, assessed using temperature-depth recorders. In order to evaluate the influence of gender on foraging, a morphometric investigation of sexual dimorphism was confirmed using molecular analysis. Additionally, plasma corticosterone levels were measured to examine breeding stage and presence of blood parasites as potential sources of stress during the breeding season. Northern Rockhopper penguins at Tristan da Cunha displayed a high degree of foraging plasticity, and fed opportunistically on a wide variety of prey, probably reflecting local small-scale changes in prey distribution. Zooplankton dominated (by mass) the diet of guard stage females, whereas small meso-pelagic fish (predominantly Photichthyidae)dominated diet of adults of both sexes in the crèche stage, with cephalopods contributing equally in both stages. Adults consistently fed chicks on lower-trophic level prey (assessed using SIA), probably zooplankton, than they consumed themselves indicating that the increasing demands of growing chicks were not met by adults through provisioning of higher- quality prey. SIA also indicated that adults foraged in different oceanic water masses when feeding for self-maintenance and for chick provisioning, thus temporally segregating the prey consumed for different purposes. It is possible that adults ‘selected’ these higher quality prey for themselves, or this may be a reflection of opportunistic behaviour. At Tristan da Cunha sexual dimorphism was observed in culmen dimensions (length, depth, width), with males having larger beaks and feeding on larger individuals of squid and fish than females. No sexual segregation in terms of foraging habitat (i.e. different water masses, based on ð¹³N or trophic level ð¹⁵N) during the breeding season or pre-moult period was revealed through SIA, and stomach content analysis revealed no sexual differences in prey species targeted. The results of SIA of feathers indicate that during the pre-moult period birds foraged in different water masses than during the breeding period. The fact that throughout the breeding season birds foraged in similar habitats suggests no intra-specific competition, despite both sexes feeding on the same prey.Birds were generally diurnal, daily foragers (12 – 16 hr trips), with extended trips (maximum duration 35.5 hours) and nocturnal diving recorded in a few individuals. Birds dived well within their physiological limits, predominantly utilising the upper 20m of the water column, employing two different strategies to target different prey items. Long, deep (30 – 40 m), energetically costly dives were performed when targeting energy-rich prey (fish), and a greater number of shorter, shallower (5 – 20 m), energy-efficient dives were performed when targeting prey with a lower energy content (zooplankton). More than half of the sampled study population were infected with the intra-cellular blood parasite Babesia, but infection showed no relationship to body mass, corticosterone levels or breeding success. Fasting birds showed no signs of elevated corticosterone levels, suggesting they had acquired sufficient fat reserves prior to breeding. Failed breeders did not exhibit elevated corticosterone levels. Tristan skuas, Catharacta antarctica hamiltoni, were observed to be a significant cause of egg and chick mortality. The absence of sex-based differences in foraging, and the absence of any signs of stress in relation to body mass, presence of Babesia or breeding stage, suggest that there are no obvious signs of high levels of stress or food limitations during breeding at Tristan da Cunha.
- Full Text:
- Date Issued: 2012
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