Doctoral Degrees (Ecology)

Permanent URI for this collectionhttps://hdl.handle.net/10413/7487

Browse

Now showing 1 - 20 of 43

Anthropogenic impacts on forest mammals in the Southern Mistbelt Forests in the Midlands of KwaZulu-Natal, South Africa.
(2023) Cordier, Craig Paul.; Downs, Colleen Thelma.; Ehlers Smith, David Alan.; Ehlers Smith, Yvette Cathrine.
Habitat loss worldwide is a major threat to biodiversity. Forest loss is affected by numerous factors, including natural climate change and anthropogenic disturbances (e.g., logging, habitat conversion or increased fire activity). Forest fragmentation results in reduced patch sizes, increased edge effects, and connectivity between patches negatively impacted. Forest fragmentation effects on species differ, with some considerably more sensitive to these changes than others, often resulting in their local extinction. By monitoring biodiversity, effective conservation measures can be implemented to conserve the biodiversity in these forests. Remote camera traps have become an increasingly popular tool to study wildlife in a reliable, non-invasive way. Firstly, the use of camera traps as a research tool in Africa using a systematic review was determined. This highlighted the countries with studies that used camera traps the most, as well as determined the terrestrial wildlife and habitat types receiving the most focus. The findings from assessing camera trap research in Africa revealed that most studies were conducted in South Africa, with most studies focusing on the occupancy of mammals, with a particular focus being on large carnivores, the majority of which were leopard Panthera pardus. Most studies were conducted in forests, followed by savannah/bushveld. Secondly, the presence of forest mammalian species was assessed in the Southern Mistbelt forests in the Midlands of KwaZulu-Natal, South Africa. These forests are fragmented because of both natural and anthropogenic factors. An extensive camera trapping survey was conducted between October 2020 and April 2021 (wet season), and between May 2021 and September 2021 (dry season), with 14 indigenous forest patches being sampled. A total of 339 camera trap stations were deployed in this study, with microhabitat conditions, in a 20 m radius around each camera trap, collected to determine their impact on bushbuck Tragelaphus scriptus, a diurnal forest specialist, and Cape porcupine Hystrix africaeaustralis, a nocturnal generalist, and how the microhabitat conditions potentially impacted their occupancy between the austral wet and dry seasons. Bushbuck were the most recorded mammalian species recorded during both seasons. Cape porcupine presence was recorded more during the dry season, with various microhabitat variables influencing their occupancy. Cape porcupines, as generalists, likely use the forest food resources during the dry season. Bushbuck presence was lower in state-owned forests, likely because of the hunting activities observed in these forests. Thirdly, data collected from the camera trapping surveys were used to determine the influence of landscape factors, including patch size, landscape configuration (number of neighbouring patches), and patch isolation (distance from mainland patch), on forest mammalian species diversity in forest patches, between the wet and dry seasons. Patch size strongly influenced forest mammalian species richness, which was relatively low, with more species occupying larger patches than smaller patches. Similarly, landscape configuration affected species richness and was generally higher in those forests surrounded by multiple forest patches. Forest isolation, however, did not seem to be particularly impactful in determining forest mammalian species diversity. Overall, this research showed the value of camera traps as a research tool and their effectiveness in studying rare and elusive mammalian species in Africa. Effects of anthropogenic disturbances on various forest mammalian species were highlighted, with activities such as hunting and uncontrolled resource harvesting, such as collection of fuelwood, medicinal plants and building materials by the local communities, impacting the presence of various forest mammalian species, particularly forest specialist species, such as the blue duiker Philantomba monticola. The importance of maintaining small forest patches, often considered of low conservation value, was highlighted. These act as essential ‘stepping stones’ between forest patches, allowing species to traverse a landscape mosaic. The need for conservation measures not to disregard the importance of these small forest patches is emphasised, as they are vital assets to maintain species richness in landscape mosaics with forest patches.
Aspects of common hippopotamus (Hippopotamus amphibius) behavioural ecology and their consequences in managed systems in South Africa.
(2020) Fritsch, Camille Jacques-Armand.; Downs, Colleen Thelma.
Abstract available in PDF.
Aspects of monitoring wild and captive Nile crocodile (Crocodylus niloticus) populations in southern Africa = Izingxenye zokubhekelela uhlobo lwengwenya yasendle nevalelwe yaseNile (Crocodylus niloticus) e-Afrikha eseningizimu.
(2021) Myburgh, Hendrik Albert.; Downs, Colleen Thelma.
As biodiversity across the globe declines because of anthropogenic activities, the need for conservation efforts increases. For conservation efforts to be successful, it is imperative that detailed information about species and their populations; size and status within and outside of protected areas be collected. In freshwater systems, crocodile population demographics can provide an integrated view of ecosystem state, but the habitat and cryptic nature of crocodilians confound the derivation of population demographics for the taxa. Crocodile populations were historically monitored by fixed-wing aircraft, helicopter or limited spotlight surveys in those areas that are navigable by boat. These techniques are costly and labour-intensive; require specialised personnel and equipment, and are subject to observer bias and low accuracy in size class estimations. Furthermore, they produce population demographic data that is not verifiable as they rely on decisions and opinions of observers in the moment of surveying, often fromfast-moving platforms. Lately, unmanned aerial vehicle (UAV) techniques have been shown to accurately and effectively count crocodiles, but they still require costly software and hardware packages. In this study, low-cost, open-source UAV techniques were developed as an alternative method to monitor and survey crocodilians, particularly Nile crocodiles (Crocodylus niloticus), both in captivity and in the wild. In South Africa, Nile crocodiles occur in open bedrock systems with relatively little riparian vegetation, an ideal scenario for the application of UAVs. The possibility of improved population demographic data for wild Nile crocodile populations by converting size data derived from UAVs to age data was explored by radiocarbon dating Nile crocodile claws. Morphometric correction factors applicable to UAV census are derived, and a fixed-wing survey is compared with a commercial-grade UAV survey of wild Nile crocodile populations in the Kruger National Park. The limitations and applicability of these approaches for crocodilian and other ecological studies were assessed. Their future applications in ecology and management are proposed. Iqoqa Njengoba impiliswanomvelo kuwo wonke umhlaba yehla ngenxa yezenzo ezidalwe ngabantu, isidingo sokongiwa kwemvelo siyakhula. Ukuze imizamo yokongiwa kwemvelo ibe impumelelo, kuyaphoqa ukuthi kuqoqwe ulwazi olunzulu mayelana nokuphilayo kanye nezinhlobo zakho, ubungako kanye nesigaba phakathi kanye nangaphandle kwezindawo ezivikelwe. Emanzini aphilayo, uhlobo lwemiphakathi yezingwenya zingasinika iso eliyinhlanganisela lesimo sohlalonhlaliswano yokuphilayo nokungaphili, kodwa isimo sendawo yokuhlala kanye nesingachazeki sididisa ukwehlukanisa ukutholakala komphakathi wezinhlobo zezingwenya. Imiphakathi yezingwenya yayibhekelelwa emandulo ngendizamshini ehlala phezulu emoyeni, indiza enophephela emhlane noma amasaveyi angemaningi agqamile kulezo zindawo okuhambekayo kuzo ngezikebhe. Lawa masu ayabiza futhi adinga amandla okusebenza, adinga abasebenzi abaqondene kanye nemishini yokusebenza, kanti futhi ancike ekuchemeni kobukelayo kanye nezinga eliphansi ngobungako besihlawumbiselo sohlobo. Okunye futhi, akhiqiza imininingo yohlobo lwemiphakathi engathembakali njengoba ethembele ezinqumeni kanye nemibono yababukela ngesikhathi sokwenza amasaveyi, okujwayele ukuthi kube izinhlaka ezihamba ngokushesha. Kamumva nje, amasu esithuthi ezingasetshenziswa muntu ezisemoyeni, i-unmanned aerial vehicle (UAV) asevezwe njengakhombisa ukubalwa kwezingwenya okuqondile nokunemiphumela emihle, kodwa asadinga ubuchwepheshe obubizayo kanye nezindodla zobuxhaxhaxha bobuchwepheshe. Kulolu cwaningo, okungabizi, amasu ezizinda ezivulekile e-UAV kwaqanjwa njengenye yendlela engasetshenziswa ukubhekelela nokusaveya izingwenya, kakhulukazi izingwenya zaseNile (Crocodylus niloticus), zozimbili ezivalelwe kanye nezasendle. ENingizimu Afrikha, izingwenya zaseNile zivela ekusetshenzisweni kwamadwalamsuka avulekile anotshalovikelo olungeluningi, okuyisibonelo esincomekayo sokusebenzisa ama-UAV. Ukuba khona kwemininingo ethuthukile yezinhlobo zemiphakathi yezingwenya zasendle zeNile ngokushintsha ubungako bemininingo etholakale kuma-UAV ukukhulisa imininingo kwaphenywa ngekhabhoni yomoya ukubona izindlawu zengwenya yaseNile. Izimo zokulungisa ukusebenza kokubala kwe-UAV kutholakele, kanti futhi isaveyi yophiko olunganyakazi luqhathaniswa nesaveyi ye-UAV yohlobo lokusebenza lwemiphakathi yohlobo lwengwenya yasendle yaseNile e-Kruger National Park. Imikhawuko kanye nokusebenzeka kwalezi zindlela zokubhekelela izingwenya kanye nezinye izicwaningo zezemvelo kwahlolwa. Ukusebenza kwayo kwesikhathi esizayo emvelweni kanye nokwenganyelwa kuyaphakanyiswa.
Aspects of the ecology and persistence of vervet monkeys in mosaic urban landscapes in KwaZulu-Natal, South Africa = Izingxenyezici zendawomvelompiliswano kanye nokwanda kwezinkawu zohlobo lwe-vervet ezindaweni zasemadolobheni ezihlukahlukene ngokwezimo zempilo KwaZulu-Natali eNingizimu Afrika.
(2022) Pillay, Kerushka Robyn.; Downs, Colleen Thelma.
The geological era in which we live is termed the Anthropocene and is causing the greatest loss of biodiversity and species brought on by a single species: Homo sapiens. The human population places great demands on the environment, altering and modifying it to suit people’s needs. Urbanisation is one of the greatest anthropogenic land-use modifications, predominantly for infrastructure and housing developments. This results in the loss of natural green spaces where wildlife lives, forcing them into smaller fragmented habitats, often having to share the urban mosaic landscape with humans. These increased interactions often lead to humanwildlife conflict. Generally, urbanisation affects species negatively. However, some species exhibit the ability to persist in urban areas, successfully utilising resources for their natural life traits. One such primate species persisting in urban mosaic landscapes is the vervet monkey, Chlorocebus pygerythrus, particularly in the eThekwini Municipality, Durban, KwaZulu-Natal Province, South Africa. Increased human population growth and associated urban transformation have increased contact between humans and troops of vervet monkeys using residential and industrial gardens. This has led to increased human-wildlife conflict, with vervet monkeys often persecuted because of their damage to human property and harassment. Little is known about the ecology of urban vervet monkeys, so to assess and manage this wildlife conflict, a need to determine the behavioural ecology and persistence of vervet monkeys were investigated in this study. This study analysed vervet monkeys' spatial ecology in the mosaic urban-forest landscape and provided insight into their home ranges and habitat use here. Additionally, the effects of anthropogenic activities and human-wildlife conflict on wild vervet monkeys were documented. The results contribute to understanding the foundation of human-vervet conflict resolution programmes and support for further education and coexistence with wildlife in mosaic urban landscapes. The conservation of vervet monkeys should be supported by all who live in these areas, not by some factions. The presence of primates, such as the vervet monkey, that use managed green spaces, such as gardens, in the eThekwini Municipality should provide the public with the ultimate catalyst and insight into protecting and conserving this species and others for future generations. Overall, the results presented in this thesis provide an understanding of the persistence of this Old World primate in mosaic urban landscapes. Iqoqa Isikhathi esiphila kuso mayelana nesimo sendalo yomhlaba esikuwo saziwa ngele-Anthropocene siyimbangela yokushabalala okusezingeni eliphezulu yokusatshalaliswa kwendawomvelompiliswano kanye nohlobo lwezilwane okubangelwa uhlobo olulodwa: oluyi-Homo sapiens. Izidalwa ezingabantu zinomthelela omkhulu emvelweni ngendlela yokuthi ziguquguqula imvelo ukuze kufezeke izidingo zazo. Ukwakhiwa kwezindawo zasemadolobheni kungenye yezinguquko ezidalwa ngabantu lapho besebenzisa umhlaba ikakhulukazi ukwakha izindawo zokuhlala kanye nezingqalasizinda. Lokhu kuholela ekuthini kuntuleke izindawo okuphila kuzo izilwane zasendle okube sekudala ukuthi lezi zilwane zigcine sezihlala ezindaweni ezimpintshekile zaba zincane. Lokhu kube sekuholela ekuthini zigcine sezibanga indawo nabantu basemadolobheni. Lokhu kwanda kokuhlalisana nabantu kuholela ekushayisaneni phakathi kwabantu kanye nezilwane. Nokho-ke, kunohlobo olukhombisa ukuthi luyakwazi ukuqhubeka nokuphila kahle ezindaweni ezingamadolobha ngokuzizamela kulokho okukhona ukuze luziphilise ngendlela efanele. Uhlobo olukhombise ukuthi luyakwazi ukuqhubeka nokuziphilisa ngaphansi kwesimo sasemadolobheni yilolu lwezinkawu ezaziwa nge-vervet, Chlorocebus pygerythrus,ikakhulukazi endaweni kaMasipala weTheku, eThekwini, esifundazweni saKwaZulu-Natali, eNingizimu Afrika. Ukwanda kwesibalo sabantu kanye nokuguquka kwesimo senhlalo yabantu okuhambisana nakho sekwenze ukuthi kwande nokuhlangana kwabantu nemihlambi yezinkawu ezizitika ezingadini zabantu emakhaya kanye nasezingadini zabalimi abakhulu. Lokhu sekuholele ekushayisaneni phakathi kwabantu kanye nezilwane zasendle okwenza ukuthi izinkawu ezingama-vervet zizithole zisenkingeni ngenxa yokucekela kwazo phansi impahla yabantu kanye nokuba yisicefe esingapheli. Aluluningi ulwazi olukhona mayelana nezinkawu zasemadolobheni ezingama-vervet, ngakho-ke lolu cwaningo lwaphenya mayelana nokuziphatha kwalezi zinkawu ngaphansi kwezimo zendawo eseziguqukile kanye nokwanda kwazo ukuze kuhlolwe kuphinde kulawulwe lokhu kushayisana nezilwane zasendle. Lolu cwaningo lwahlaziya izindawo ezingamahlathi asedolobheni okuhlala kuzo lezi zinkawu ezingama-vervet, lwase lunikeza ulwazi olujulile mayelana nezindawo okuhlala kuzo lezi zinkawu kanye nendlela eziziphilisa ngayo kulezi zindawo. Okunye okwaqoshwa phansi yimithelela yezinto ezenziwa ngabantu kanye nokushayisana phakathi kwabantu kanye nezinkawu ezingama-vervet. Imiphumela yocwaningo yathasisela olwazini olumaqondana nezinhlelo okungakhelwa phezu kwazo ukuxazululwa kokushayisana kwabantu nezinkawu ezingama-vervet, iphinde isekele ukufunda okuqhubekayo mayelana nokuhlalisana nezilwane zasendle ezindaweni ezisakhula zasemadolobheni. Kumele kusekelwe ukongiwa kwezinkawu ezingama-vervet yibo bonke abahlala ezindaweni ezisemadolobheni, kungabi ngabathile kuphela. Ukuba khona kwalolu hlobo lwezilwane ezifana nezinkawu ezingama-vervet ezindaweni ezisetshenziswa nezenganyelwe njengezingadi zomphakathi njengezikaMasipala weTheku kumele kuhlomise amalungu omphakathi ngolwazi nanogqozi lokuvikela kanye nokonga lolu hlobo lwezilwane kanye nezinye izinhlobo ukuze nezizukulwane ezizayo zikwazi ukuzibona ziphila. Ekugcineni kwakho konke imiphumela etholakale kulolu cwaningo iveze ulwazi nokuqonda mayelana nokwanda kwalolu hlobo lwezinkawu ezindaweni ezingamadolobha.
Aspects of the ecology of African woolly-necked storks (Ciconia microscelis) in an anthropogenic changing landscape in KwaZulu-Natal, South Africa.
(2018) Thabethe, Vuyisile.; Downs, Colleen Thelma.
Urbanisation is the fastest-growing forms of anthropogenic land use change and a major threat to biodiversity worldwide. However, despite the negative impacts of urbanisation on native species, some species persist in urbanised environments and this thesis aimed to examine one such species, the African woolly-necked stork (Ciconia microscelis). African woolly-necked storks have recently colonised urbanised environments in KwaZulu-Natal, South Africa, and are now common in suburban areas in particular. Despite its proximity to human settlements and recent high abundance in suburban areas, knowledge of the African woolly-necked stork remains poorly documented in South Africa. Therefore, this thesis aimed to investigate the aspects of ecology of African woolly-necked storks within the suburban landscape to determine what factors facilitate their ability to persist in these environments. Firstly, I assessed the long-term trends in occupancy, colonisation and extinction of African woolly-necked storks as a function of change in land cover across KwaZulu-Natal Province, South Africa. This was accomplished by applying dynamic occupancy models to Counts in South Africa. African woolly-necked stork wetland occupancy was relatively stable (ψ = 0.37-0.39) across years. However, they rapidly extended their distribution range to urbanised environments, becoming common in man-made wetlands. Overall, this study found that the increased area of anthropogenic areas led to an increase in the probability of wetland colonisation by African woolly-necked storks. Secondly, I investigated the foraging opportunities that might be responsible for the recent colonisation of urbanised environment by African woolly-necked storks. I found that a significant number of householders (71%) deliberately fed African woolly-necked storks daily throughout the year and the majority provided meat while others fed inappropriate food such as bread. Furthermore, I found that, African woolly-necked storks were relatively habituated in urban areas of KwaZulu-Natal, with some even feeding from hand and others going inside homes to find the supplemental food. These results showed that the African woolly-necked stork is successfully utilising and exploiting anthropogenic food – a novel behaviour for this species. Thirdly, given that the selection of appropriate nest sites has major implications on reproduction success and survival of urban bird species, I was interested to determine if African woolly-necked storks bred in urbanised areas and, if so, which features of the nest site and surrounding habitat influenced their occupancy. I found 30 African woolly-necked stork nests in suburban areas of KwaZulu-Natal. African woolly-necked storks have successfully established breeding sites in suburban areas (mostly in domestic gardens), especially near swimming pools, while exotic pine (Pinus elliottii) and eucalyptus (Eucalyptus spp.) trees were the most preferred trees. Anthropogenic structures were also used as nesting sites suggesting a nesting behaviour shift. Lastly, after acquiring evidence that African woolly-necked storks successfully utilise anthropogenic food and have established a breeding population in urban areas, I was interested to know what food they provisioned to their nestlings. Furthermore, I investigated the breeding behaviour of African woolly-necked storks using direct observations and infrared camera traps during three breeding seasons (2015-2017). Although anthropogenic food was provided to nestlings, African woolly-necked storks provisioned their nestlings predominantly with natural food, primarily amphibians, particularly guttural toads (Amietophrynus gutturalis). African woolly-necked storks consistently reoccupied most nest sites across study years since initial discovery, suggesting that this population was at least stable. For the first time, I documented evidence of cooperative breeding where more than two adults provided care to a single nest. (Amietophrynus gutturalis). African woolly-necked storks consistently reoccupied most nest sites across study years since initial discovery, suggesting that this population was at least stable. For the first time, I documented evidence of cooperative breeding where more than two adults provided care to a single nest.
Aspects of the ecology of three mongoose species along a rural–urban landscape gradient of KwaZulu- Natal, South Africa.
(2020) Streicher, Jarryd Peter.; Downs, Colleen Thelma.; Ramesh, Tharmalingam.
Many small carnivore species are of particular concern for conservation because of their elusive behaviour, diminutive size and crepuscular habits. Management and research tend to be challenging and thus is often limited. Several members of the Herpestidae family fall into this research dead zone, including the large grey mongoose (Herpestes ichneumon), slender mongoose (Galerella sanguinea), white-tailed mongoose (Ichneumia albicauda) and marsh or water mongoose (Atilax paludinosus). The distribution range and other aspects of the ecology of these and other such species, has remained vague for much of the sub-tropical regions of southern Africa because of the scarcity of comprehensive data. There is little understanding of the basic ecology of these mongoose species, and limited progress has been made in understanding the tolerance of these species within a changing environment. These species of mongoose appear to persist across KwaZulu-Natal’s (KZN), South Africa, anthropogenically modified habitats (farmlands and urban). Small carnivore species, such as mongooses, can provide models of how medium-sized carnivores tolerate differing degrees of anthropogenic land-use change. A global review of the current knowledge and research effort for urban mammalian mesocarnivores was conducted. In the last decade, there has been a dramatic increase in the number of studies that focus on medium-sized mammalian carnivores. Disproportionate levels of urban studies exist for mesocarnivores. Several species have been comprehensively studied in the United States of America and the United Kingdom. These two developed countries held more than half of all studies on urban mammalian mesocarnivores. Areas of the world that are undergoing rapid urbanisation have the most significant deficiency of research. Across Africa, the spatial ecology of the Herpestidae family remains relatively poorly studied. We investigated how anthropogenic land-use change affects aspects of the ecology of three co-existing mongoose species (large grey, water and white-tailed) in the agricultural setting of the KZN Midlands. Individuals of these three species of mongooses were trapped, collared and tracked using GPS-UHF (ultra-high frequency). The results presented show that the three focal species have different spatial requirements and movements from previous stated in literature. The natural habitat and farmland mosaic of the KZN Midlands are segregating the preferred habitats into small fragments. These niche fragments are intensely used by each species and allow them to co-exist in these anthropogenically modified environments. Besides these species’ generalist nature, their behavioural plasticity may assist them in persisting in anthropogenically modified landscapes. In the absence of apex predatory control, an expansion in the range and population number of Herpestidae species is expected. This study provides crucial information on the spatio-temporal ecology of large grey, water and white-tailed mongoose in the KZN Midlands. The spatial movements of the three co-existing species in this study highlighted the variability that is present at a species and individual level. Further research is required to address the human–wildlife conflict that takes place locally. The urban aspect of the large grey, water and white-tailed mongoose ecology is also understudied, and we recommend further research be targeted. The spatial ecology of water mongoose in the urban green space matrix of the Upper Highway Area of eThekwini, KZN, was subsequently investigated. This was to compare aspects of their ecology between fragmented natural farmland and urban mosaic using similar methods. Water mongooses occurred at a high density in the fragmented green Durban Metropolitan Open Space System (D’MOSS). Insight into the spatial ecology of urban water mongoose (home range, core area utilisation, overlap and habitat use) determined using GPS telemetry data from 14 water mongooses from July 2018 - October 2019. Water mongooses had constricted spatial movements that were highly dependent on natural refugia, and individuals intentionally avoided built-up areas of the urban matrix. The confined nature of these green spaces consequently resulted in home range sizes that were significantly smaller than their farmland conspecifics. However, the species behavioural plasticity and generalist nature has allowed the species to occur at higher population densities in the green spaces of the urban matrix of the Upper Highway Area. Furthermore, the effects of urban sprawl on the dietary ecology of water mongooses using faecal analyses was conducted. Water mongooses scat samples (n = 104) were opportunistically collected and with the aid of members of the Kloof Conservancy during the study. Urban water mongooses consume a diverse array of dietary items (9 categories), which is dominated by three categories (relative frequency of occurrence: crustaceans 35.7%, invertebrates 19.9%, small mammals 19.1% and other 25.2%). Seasonal variation in the diet only occurred for crustaceans and invertebrates with the other dietary categories consumed equally throughout the seasons. Additionally, it was demonstrated that urban water mongooses are supplementing their diets with anthropogenic waste (chicken bones, plastic particulates and cigarette butts). The broad diversity in dietary categories and supplementation of anthropogenic waste demonstrates the generalist opportunistic feeding behaviour and adaptability of the species in an urban matrix. An online questionnaire survey was conducted to investigate socio-ecological attitudes and general perspectives towards mammalian mesocarnivores across a land-use gradient (rural–urban) from the uMgungundlovu to eThekwini Municipalities of KZN. Significant trends were assessed using the frequency of responses. The public held a range of different perspectives. Overall, respondents viewed mesocarnivores as non-threatening and vital for the environment. However, black-backed jackals (Canis mesomelas) were commonly identified as a problematic pest species, that subsequently are targets of predator control pressures by rural participants. The survey also identified that smaller, behaviourally flexible species (mongoose species and cape genet Genetta tigrina) were commonly sighted and are potentially increasing in both land-use types in the absence of competition and predatory control. Vehicle collisions are the primary cause of mesocarnivore fatality reported by participants of the survey. The impact of mesocarnivores was perceived differently along a land–use gradient which links to levels of interaction. The study emphasises the importance of citizen science and community engagement when attempting to understand the drivers of human–wildlife interactions and potential mitigation strategies. The present multifaceted study has improved our understanding of solitary members of the Herpestidae family and how anthropogenic changes affect them across a land-use gradient. Furthermore, the behavioural flexibility and adaptability of mongooses in enabling them to persist at differing degrees of anthropogenic pressure were evident. However, the size class of mammalian mesocarnivores remains understudied in Africa, and this is of concern in a rapidly developing region.
Aspects of the ecology of trumpeter hornbill (bycanistes bucinator) across urban-forest mosaics in KwaZulu-Natal, South Africa.
(2016) Chibesa, Moses.; Downs, Colleen Thelma.
Abstract available in PDF file.
Aspects of the use of vultures in traditional medicine in KwaZulu-Natal, South Africa, and conservation implications.
(2022) Manqele, Nomthandazo Samantha.; Downs, Colleen Thelma.; Selier, Sarah Anne Jeanneta.
Eighty percent of people in developing countries use traditional medicine either as a primary source of healthcare or as supplementary to western medicine. Traditional medicines are mainly derived from wild plants and animals. There has been a marked global increase in the use of animals and their body parts as ingredients in traditional medicine. The harvesting and use of wildlife resources in traditional medicine are largely unregulated and involve many species of conservation concern. This is true for African vultures, as evidence indicates that traditional medicine is responsible for 29% of African vulture mortalities. Currently, six out of seven vulture species in South Africa face a serious threat of extinction. The threatened species are listed under the Threatened or Protected Species regulations, which prohibit hunting and consumption. However, evidence suggests a long-standing use of vultures in traditional medicine in KwaZulu- Natal, South Africa, yet so much remains unknown about this practice. Understanding the belief system and the socio-economic dispositions underpinning the belief-based use of vultures will favour vulture conservation efforts in the province. Research was undertaken with the aim of advancing the knowledge base regarding the use of vultures in traditional medicine in KwaZulu-Natal. Accordingly, the following objectives were established: 1) to assess human-vulture interactions in a dynamic ecosystem, 2) to evaluate the dynamics behind the illegal harvesting and trade of vultures and their body parts, 3) to investigate the ethnomedicinal use of vultures by traditional health practitioners and 4) report on the efficacy of religion as an alternative for traditional medicine use. The study involved local communities surrounding protected areas and specific groups such as hunters, muthi traders, and traditional healers. A mixed-methodology approach was adopted, and data were collected using questionnaire surveys, in-depth interviews, focus group discussions and observations. A total of 728 respondents contributed to this study. Local people’s perceptions towards vultures were predominantly positive. Respondents appreciated vultures for removing carcases, thus keeping the environment clean. Results also demonstrated that hunting and wildlife consumption were common in the study areas, and that the hunting and use of vultures were a part of this. Vultures were harvested from protected areas and sold directly to traditional healers and also to muthi traders. Vultures were reportedly important in traditional medicine, but their harvesting was limited because it was perceived as a criminal activity, and the birds reportedly occurred in smaller numbers than before. In traditional medicine, seven vulture parts were used, but the head treated the majority (62%) of ailments reported. Seventy-one percent of the uses for vulture-based remedies were spiritual in nature. Religious practices such as church attendance, prayer and fasting, coupled with products like holy water, can provide relief from physical and psychological ailments. In this study, the role of religion in contributing positively to human health and well-being was underscored. Overall, results from this study can be instrumental in guiding efforts to improve vulture conservation in KwaZulu-Natal and other parts of South Africa.
Assessing anthropogenic impacts on the persistence of forest mammals within the Indian Ocean coastal belt of southern KwaZulu-Natal province.
(2016) Ehlers Smith, Yvette Cathrine.; Downs, Colleen Thelma.
Abstract available in PDF file.
Building a conservation strategy for the harpy eagle in the Amazon Forest.
(2020) Pereira de Miranda, Everton Bernardo.; Downs, Colleen Thelma.; Peres, Carlos Augusto.
Apex predators are threatened worldwide and are considered a priority in the conservation biology agenda. Their decline is associated with habitat loss and degradation, and persecution arising from perceived and actual conflict with humans. The trophic cascades emerging from the loss of apex predators can disrupt the regulation of prey populations, seed dispersal, tree composition and nutrient cycles derived from carcass deposition, with widespread consequences for biodiversity. The harpy eagle (Harpia harpyja) is the Earth's largest eagle and is considered a flagship species for Amazon Forest conservation. Harpy eagles are threatened by poaching and by loss and degradation of habitat. This thesis is comprised of nine chapters—being seven of them data chapters—related to harpy eagle biology and conservation. Chapters 1 and 9 are respectively an introduction and a synthesis about the subjects I approached. In Chapter 2, I created a predictive model of the species range aimed at understanding the current distribution, the contraction of the species distribution compared with the original range, and sites that currently have notable potential for reintroduction of harpy eagles. In Chapter 3, I analyse the effects of environmental parameters such as moonlight and temperature on prey selection probability. In Chapter 4, I aimed to establish the factors that drive the killing of harpy eagles by local people, including the relation between livestock predation and harpy killing. Chapter 5, I explore the nesting, timing and rates of visitation to nests by parent and fledged eagles as it relates to the viability of harpy nests as ecotourism attractions. In Chapter 6, I conducted a meta-analysis that synthesises data on nest tree selection by harpy eagles with the tree species preferences by loggers. In Chapter 7, I test the hypothesis that harpy eagles are agents of accumulation of nutrients, by concentrating decaying remains of prey items at nest sites over decades, thereby biomagnifying soil and foliage nutrient profiles. In Chapter 8, I describe rates of prey delivery by harpy eagles to their nests, and the composition of this prey, to understand the effects of forest loss on harpy eagle feeding ecology. This multi-faceted set of topics were combined in the field with a new, responsible ecotourism strategy focused on harpy eagles. Subsequently, I hope to build an evidence-based, economically-viable conservation strategy for the largest eagle on Earth, as well as to understand their keystone function of harpy eagles in Neotropical forest ecosystems.
The comparative ecology of Natal's smaller estuaries.
(1983) Begg, George William.; Hanks, John.; Bowmaker, A. P.
Fifty one of Natal's 73 estuaries have been almost completely overlooked in terms of any scientific study, despite which a marine nursery function has commonly been attributed to each of them. In the knowledge that many of these systems were normally closed and others were in a seriously degraded state, this study was undertaken with the aims of examining their present day community structure in order to provide a basis upon which their future condition can be monitored and to provide a classification of these coastal resources. The study area incorporated 62 different systems extending over 240 km of the Natal coastline south of the Tugela River. During the three year study period (Sep 1979 - Nov 1982) 82 515 specimens, comprising an assemblage of 125 different species, were caught by means of a small beam trawl. These comprised 86 species of fish, 21 species of crabs and 18 species of prawns. The data obtained were correlated to abiotic variables such as mouth condition, salinity, temperature, dissolved oxygen, water transparency, depth, nature of the substratum and peripheral vegetation. Based on the ability of biota to synthesize environmental variables into one common response, multi-variate analysis is used to demonstrate the similarity in community structure between open and closed systems (for example) or between fresh and saline systems, and thereby resolve an age-old argument about estuary classification. The data also suggest that in their present day condition only six of the systems studied make a significant contribution to the recruitment of estuarine-dependent marine stocks (sensu stricto) principally because of their open mouth condition. Closed systems, deliberately classified as lagoons, have a different resource value, being utilized primarily by resident species that can complete their life cycle within the system. An appreciation of this salient difference helps to reinforce the critical need for an effective management strategy to be implemented to prevent Natal's dwindling estuarine resources from deteriorating any further. The term 'estuarine-dependence' is critically examined in this context to show that a species more dependent on estuaries than any other, is man. It is argued that man's continued abuse of these resources is shortsighted, and that the most serious threat of all is sedimentation, accelerated in this instance beyond the geological norm by catchment mismanagement. The practical application and value of classification to planning and management is demonstrated and a methodology proposed, based on community responses, for the monitoring of the future environmental condition of each estuary and lagoon in Natal.
The conservation ecology of the African tigerfish Hydrocynus vittatus in the Kavango River, Namibia.
(2017) Jacobs, Francois Jakob.; Downs, Colleen Thelma.
Abstract available in PDF file.
Controlling woody plant encroachment in a southern African savanna.
(2021) Monegi, Piet.; Tsvuura, Zivanai.; Ward, David Mercer.; Tjelele, Julius Tlou.
Woody plant encroachment is considered one of the most extensive forms of degradation affecting savannas in arid and semi-arid ecosystems. Thus, reactive interventions such as chemical and mechanical controls, as well as fire application remains the norm in management of woody plant encroachment. I conducted a series of woody plant control experiments at the Agricultural Research Council’s Roodeplaat experimental ranch, situated in Gauteng Province, South Africa. The first experiment was a tree-thinning study at two savanna sites that differ in soil texture and woody species. Site 1 was on previously cultivated clay-dominated soils characterized by severe soil erosion and was encroached by Vachellia tortilis. Site 2 has never been cultivated and was on sandy soils with several woody species. At each site, 24 30 m × 30 m plots separated by 5 m wide fire breaks were established. Trees were removed to the approximate equivalents of 0% (control-no removal), 10%, 20%, 50%, 75% and 100% (complete removal of trees), followed by herbicide application on half of the stumps for each plot. I also investigated the effectiveness of Tree Poppers® (weed wrench) as a low-cost mechanical control tool to physically uproot seedlings and saplings of woody plants. To examine the effectiveness of the Tree Popper®, I used eight dominant tree species that were grouped into three height classes (0-49 cm, 50-99 cm, 100-150 cm) of ten seedlings and saplings per species per height class. In addition, investigated the effects of five years of annual burning on vegetation dynamics in a Vachellia karroo woodland. To determine the effects of annual burning on vegetation dynamics, plots (0.25 ha) established in 2013 were used. These studies are summarized below: (1) I determined the combined effects of tree species, tree thinning, stump diameter and herbicide application on resprouting patterns of woody plant species (Dichrostachys cinerea, Ehretia crispa, E. rigida, Gymnosporia buxifolia, Pappea capensis, Searsia lancea, S. caffra, Vachellia karroo, V. nilotica, V. robusta, V. tortilis and Ziziphus mucronata) that encroach study site 1. All the tree species in this study resprouted after cutting. Herbicide application significantly reduced the resprouting ability of D. cinerea, E. rigida, V. robusta and Z. mucronata. Tree removal positively influenced the resprouting ability and vigour of E. crispa only. The diameter of stumps was an important factor in determining resprouting ability, with shoot production decreasing with increasing stump diameter. The findings from this study suggest that woody plants are more likely to resprout and survive as juveniles than as adults after cutting. (2) I found no significant differences in the number of seedlings and saplings uprooted by Tree Popper®. However, there were significant differences in the number of juveniles uprooted using a Tree Popper® with a few individuals of Vachellia species uprooted. The effectiveness of the Tree Popper® may be due to differences in plant morphological structure, particularly the root system. The Tree Popper® is not an effective tool for controlling the Vachellia species used in this study. However, communal ranchers may mechanically control shallow-rooted tree seedlings with the Tree Popper® but not deep-rooted ones, specifically Vachellia species. (3) In the tree thinning experiment, I determined the effects of different tree thinningintensities on grass species-richness, composition, cover, β diversity, and soil fertility. I found that tree thinning did not have any significant effects on grass species-richness in either study site. However, we found a clear separation of different grass species among the treatments over the study period. Different levels of tree thinning increased the abundance of two dominant grass species (i.e. Digitaria eriantha and Panicum maximum) in both study sites, particularly in moderate (50%) and high removal (75% and 100%) treatments. However, the nitrophilous grass (i.e. P. maximum) will likely decline in abundance with time, particularly in the 100% thinning treatment because the ecological process that is responsible for N-fixation is no longer existent. Contrastingly, I found no evidence that tree thinning affects the amunt of soil cover. In addition, tree thinning did not have a significant impact on soil fertility in either study site. I recommend maintaining a stand density of 50% in rangeland affected by woody plant encroachment. In this study, 50% thinning created an opportunity for different palatable grass species to increase in abundance, which may help to increase forage production. (4) I determined the effects of different tree removal-intensities on grass production, tree-seedling establishment and growth, and the growth of the remaining large trees. In site 1, tree-removal treatments (i.e. 75 and 100%) significantly reduced grass biomass production after the first growing season, with no effect after the second season. In site 2, tree removal significantly increased grass biomass production. I found no significant effect of tree removal on tree seedling establishment in site 1. In site 2, tree removal had a significantly negative effect on overall tree seedling establishment. In both sites, there were no significant differences in tree seedling growth. Moderate (50%) to high (75%) removal of trees had a positive effect on the growth of remaining large trees in both study sites. I found that increased and/or diminished grass biomass production plays a vital role on tree seedling recruitment. Reduced tree competition facilitates the growth of the remaining large trees. An implication of these findings is that regardless of the substantial costs of woody plant control, the recovery of key ecosystem services such as an increased forage production may not be realised. However, this may be system-specific. In other systems, the absence of management interventions such as tree removal may compromise provision of ecosystem services and ecosystem functioning. (5) In the fire experiment, I investigated the effects of five years of annual burning on the density of young and adult Vachellia karroo plants. This study also aimed to investigate the effects of annual burning on tree growth (i.e. height, stem diameter and canopy size). The results supported the “fire-trap” paradigm by demonstrating substantially higher densities of young plants in the burned plots than in the unburned plots. In addition, the recruitment of young plants and saplings into adult trees was significantly higher in the unburned plots than in the burned plots. V. karroo populations substantially increased in growth (height and basal diameter) in the unburned plots. Different grass species changed in abundance in response to annual burning. However, I found no significant changes in grass species diversity and richness between the treatments. I found that the removal of the grass layer by fire and repeated topkill increased the number of young V. karroo individuals. Annual burning limited V. karroo juveniles and saplings from reaching an adult size class that may have detrimental effects on the herbaceous layer. I demonstrated that grass species composition is more prone to fireinduced changes than species diversity and richness in our study area. In conclusion, I show that managers of savanna rangelands may use annual burning to achieve specific vegetation structural objectives. This thesis demonstrated that mechanical- and chemical -control, as well as fire application influences the structure and functioning of savannas. By creating gaps that promote grass production, these management practices may assist increase the economic viability of savanna ecosystems. However, despite the popular belief that reduced tree densities promote ecosystem functions, this thesis demonstrates that the impact of control techniques (especially tree thinning) on forage production vary across savanna sites. This thesis also shows that management with prescribed annual fire reduced woody plant encroachment across the 5-year study, suggesting that fire management can be beneficial and should be explored as a management method.
Crocodile (Crocodylus niloticus) meal diets as a potential for replacement of fishmeal protein in commercial production of Mozambique tilapia (Oreochromis mossambicus)
(2022) Luthada-Raswiswi, Rendani Winnie.; Mukaratirwa, Samson.; O'Brien, Gordon Craig.
Fishmeal production is mainly sourced from the forage fish species. Fish caught for fishmeal production potentially represents a loss in producing higher trophic level species in the ecosystem. Low stock abundance reduces ecosystem services such as food provisioning to other elements of the ecosystem. Increasing demand, unstable supply, and the high price of the fishmeal with the expansion of aquaculture made it necessary to search for alternative protein sources. Crocodiles are farmed mainly for producing skins used in the production of high-quality fashion accessories. However, the demand for crocodile meat, especially in South Africa, is very low and strict regulations are imposed onto the industry about the use and disposal of crocodile carcasses. This study was conducted to assess the nutritional value of crocodile meals and their suitability as a fishmeal replacement in animal feeds, especially fish. Systematic review and meta-analysis results showed the gap that some animal by-products, including crocodile meat, had not been assessed as protein sources in aquaculture or animal feeds. Different size groups of fish are not considered in studies when testing different alternatives for fishmeals. The nutritional values of Crocodylus niloticus derived meal obtained in the current study is of comparable quality for use in aquaculture feeds, compared to by-products meal quality reported for meal derived from bovine bones and meat, feathers, blood and other poultry by-products. There were similarities in the gross feed conversion ratio for fry and the specific growth rate for fingerlings of Oreochromis mossambicus among all the experimental diets fed. That means the Crocodylus niloticus meal is a suitable animal protein source for replacing fishmeal in Oreochromis mossambicus diets. Some haematological parameters such as red blood cells count, and haemoglobin concentrations were significantly different among Oreochromis mossambicus fed crocodile-based and commercial diets. However, platelets count, haematocrit value, mean cell volume, mean cell haemoglobin, and mean cell haemoglobin concentrations were not significantly different among all diets fed. More future studies are recommended for different levels of Crocodylus niloticus meal in other fish species, different size groups, and haematological parameters. This study provides new information to the aquaculture industry regarding reducing supply constraints imposed by high cost and competitive uses for fishmeal and waste management on crocodile farms.
Diversity of edible insects and their related indigenous knowledge: evidence from KwaZulu-Natal and Limpopo provinces, South Africa.
(2021) Hlongwane, Zabentungwa Thakasile.; Munyai, Thinandavha Caswell.; Slotow, Robert Hugh.
Entomophagy is an ancient indigenous practice that has played a significant role in human nutrition around the world. In addition, the traditional use of edible insects forms an important part of food culture in Africa. Edible insects are widely consumed across the African continent for their taste, nutritional value, or as an emergency food source during times of food shortage. They have been proposed and recommended as a sustainable food source that can assure food security, because edible insects are rich in protein, fats, amino acids, iron, zinc, and energy. As a result, edible insects play an essential role in human nutrition. In addition, the trade of edible insects plays an important role in improving livelihoods in developing countries. However, little is known about the diversity and nutritional composition of various insects consumed in South Africa. In addition, little is being done to document traditional knowledge on the consumption of insects, and processes involved in harvesting, processing, and preparing edible insects. This study aimed to document indigenous knowledge regarding the consumption of edible insects, their diversity and distribution, and their nutritional composition. This was done by (i) reviewing existing literature on the diversity of insect and their nutritional status in Africa. (ii) documenting consumption patterns, methods, or techniques used in collecting and preparing insects in South Africa. (iii) determining the nutritional composition of some major insect groups consumed in Africa, (iv) determining the most preferred insect groups, and (v) by documenting the socio-economic benefits of trading insects. Closed and open-ended questions were conducted in various rural areas in five and four local municipalities in KwaZulu-Natal (KZN) and Limpopo. To document indigenous knowledge about trading, consumption, collection and preparation methods used in these provinces. Dried samples of four insect groups were procured from different markets across Vhembe district, Limpopo Province. The nutritional composition of the procured insect types was analysed using the standard Association of Official Analytical Chemist (AOAC) methods. A systematic review was conducted to determine the diversity and nutritional composition of edible insects consumed in Africa. A systematic review search resulted in 98 eligible papers listing 212 edible insect species from eight orders that are used as food in Africa. The highest protein (range: 20–80%) and fat (range: 10–50%) content were recorded in order Lepidoptera. While the highest carbohydrates (range: 7–54%) content was reported in order Coleoptera. Majority of the people still practice entomophagy in Limpopo while, there are only a few people consuming insects in KwaZulu-Natal. Gynanisa caterpillar, Gonimbrasia belina (mopane worm), termites, Encosternum delegorguei (stink bug), Cirina forda (emperor moth), Locustana spp. (brown locust), Zenocerous spp. (grasshopper), Carebara vidua (ant), and Cicadoidea spp. (cicada) were used as food in Limpopo and KwaZulu-Natal. From these, mopane worms and termites were the most preferred species. These insects were primarily collected from the wild, and consumed either fried, boiled, roasted, sundried, or as relish. Nutritional benefits and tradition were the primary reason for consuming insects in the two provinces. However, religion and discomfort associated with consuming insects were the main reasons for not consuming insects. Findings from the nutritional analysis of four insect types showed that termite (soldiers/ workers) had the highest protein and iron content, while Gynanisa caterpillar had the highest zinc content. The ranges of the percentage contribution of the insects studied relative to the Estimated Average Requirement (EAR) for protein amongst different age groups, indicated that the insects would contribute significantly to addressing protein deficiencies, 89.5-160.4% EAR for 4-8 years old children and 29.9-53.6% EAR for childbearing women (19-50 years). However, because Gonimbrasia belina are consumed in a relatively higher portion size than the other edible insects, it would be a good source of protein for different population groups. Generally, boiling with or without salt added resulted in a significant increase in protein, iron, and zinc content of Gonimbrasia belina samples. On the other hand, frying resulted in a significant decrease in protein content of Gonimbrasia belina samples. Five insect groups were traded for cash income in Vhembe district, Limpopo province. Of these, mopane worm was the most traded insect. Trading insects provided financial support and cash income to unemployed people in this province. Income generated from trading insects range from R100 - R200 ($6, 2 - $12, 3) per week to above R2000 ($123, 3) per week with the majority of traders making an income of R600 -R1000 ($36, 9-$61, 6) per week. Unemployment and poverty were the main reason for trading insects. Despite the economic benefit associated with trading insects, few governmental organizations in Limpopo included edible insects in economic development strategies. In addition, insect trading took place in the informal markets along the street, pavements, and on table stalls made of cardboard and wood. Safety and hygiene were the major issues of concern stated by the respondents in Vhembe district. Therefore, government need to provide infrastructure and financial support to improve the trading conditions of edible insects. Also, policy and legislation that recognise and govern the consumption, trading, and harvesting of edible insects are required, because edible insects play an important role in income generation. In addition, edible insects contribute to food and nutrition security in developing countries with chronic nutrient deficiencies. Therefore, the consumption of insects should be promoted and encouraged in poor communities.
The ecology and conservation biology of Lilian's lovebird Agapornis lilianae in Malawi.
(2014) Mzumara, Tiwonge I.; Downs, Colleen Thelma.
Despite their popularity, parrots are the world’s most threatened birds. Lovebirds (Agapornis) are very popular pet and aviary birds and as ecologically specialised species in the wild, they are also among the most threatened group of birds. Lilian’s lovebird Agapornis lilianae is a mopane Colophospermum mopane woodland specialist. This study represents the first detailed investigation of the species ecology in the wild. The current distribution of Lilian’s lovebird in Malawi was explored. Furthermore, the extent of the largest resident population in Liwonde National Park (LNP) was investigated. Five new atlas records are reported; three within 40-56 km of the LNP population, and two were over 150 km south and north of LNP respectively. One of them in Kasungu National Park is about 66 km from the Lilian’s lovebird population in Luangwa Valley, Zambia. Lilian’s lovebirds occurred throughout LNP with the highest abundance in the central section. Seasonal movements to areas outside the park were recorded. A variety of vegetation types were used by the lovebirds. The strongest vegetation associations were with seasonally wet grasslands and not mopane woodlands. The abundance and density of the Lilian’s lovebird in LNP was investigated. The highest density estimates of 17 ± 4.8 lovebirds km-2 were recorded in LNP’s mopane woodland. However, number of observations per transect differed significantly. Waterhole counts had the lowest estimates (10 ± 3.5 lovebirds). Flyway counts had the intermediate estimate (14 ± 3.0 lovebirds). The total population of Lilian’s lovebirds in LNP is therefore estimated to be about 4000 individuals. The use of line transect counts at the end of the rainy season is recommended for continued monitoring of Lilian’s lovebirds abundance in LNP. Lilian’s lovebird is a secondary cavity user adapted to mopane woodlands. We investigated its roost characteristics and roosting behaviour. We quantified tree and roost site variables for roost and non-roost trees. Roosting behaviour was observed during the morning and late afternoon. Lilian’s lovebirds’ roosts were located in large tall mopane trees with a mean diameter at breast height (dbh) of 57.4 ± 1.64 m, a mean height of 16.5 ± 0.42 m, and with a mean cavity height of 10.0 ± 0.05 m. All roosts were located in mopane trees within mopane woodland with 10 – 50 % tree cover. Non-roost areas had significantly smaller trees (mean dbh = 39.4 ± 1.72 m) and were located significantly closer together. Human disturbance was low in both areas, however, evidence of elephant Loxodonta africana browsing was high with large areas of stunted mopane woodland recorded in non-roost areas. We recommend that the current LNP vegetation map be updated to highlight areas of stunted mopane woodland unsuitable for Lilian’s lovebird roosts. The impact of elephant browsing on large mopane trees should be assessed to understand its impact on the availability of suitable cavities for lovebirds and other tree cavity-reliant vertebrate species. Investigations into the diet and foraging behaviour of the Lilian’s lovebird revealed they fed on 30 different plant species. These occurred in six habitat types, two of which were outside LNP (agriculture fields and dambos). In the wet season majority of Lilian’s lovebirds (23 %) foraged in dambo areas, whilst in the dry season (August – November) the lovebirds mainly foraged in grasslands with tree cover (18 %). In mopane woodland feeding flock sizes differed significantly between the wet (mean = 20 ± 1.0 lovebirds) and dry season (mean = 34 ± 2.3 lovebirds). Grass seeds were their main food source from December to June. Lilian’s lovebirds diet was more diverse from July to November and included leaves, leaf buds, fruits, fruit seeds and herbs. Grass seeds fed on during the wet season had a high protein and energy content. The Lilian’s lovebirds foraging habitat is protected within LNP, however, early burning in areas outside the park needs to be monitored. The breeding biology of the Lilian’s lovebird was investigated. Data were collected through a combination of direct observations and infrared camera traps during three breeding seasons. Results show large similarities with the black-cheeked lovebird A. nigrigens in Zambia. The breeding season was from February to May. Lilian’s lovebirds nested mainly in south-east oriented deep cavities (≥ 1 m) located in large mopane trees (mean dbh = 57.6 ± 2.35 cm). Nests were located in loose clusters in the areas they roosted (mean distance to nearest nest = 24.2 m). Nest fidelity was observed. Clutch size ranged from 3 – 6 eggs, (mean 5.0 ± 0.22). We recorded 49 % hatching success and 69 % fledging success. Results suggest a low breeding success mainly due to the loss of eggs to predation. The use of poison to kill wildlife is a threat to biodiversity. In LNP illegal hunters poison naturally occurring waterholes to catch mammals and birds for food. Lilian’s lovebirds are among the victims at these poisoned waterholes. Lilian’s lovebird population in LNP represents about 20 % of the global population. The drinking habits of the Lilian’s lovebird, the availability of natural waterholes and the occurrence of poisoning incidents in LNP were investigated. Results showed Lilian’s lovebirds congregate at waterholes in the dry season with flock sizes ranging from 1 to 100 individuals. Significantly larger flock sizes were seen in the dry season compared with the wet season. The number of poisoning incidents/year ranged from 1 to 8. The dry season had the highest numbers of poisoning incidents. Lilian’s lovebirds were killed at approximately four poisoning incidents each year between 2000 and 2012. The number of lovebirds found dead at a poisoned pool ranged from 5 to 50 individuals. A list of other species affected by the poisoning is provided. There is need for increased efforts in preventing this lethal activity in the park. Avian diseases are considered to be one of the key threats to bird conservation. Psittacine beak and feather disease (PBFD) is the most significant infectious disease in psittacines. It is caused by the beak and feather disease virus (BFDV) and currently has no cure. PBFD threatens the survival of wild populations of endangered parrots in Africa. The occurrence of BFDV was investigated in wild populations of Lilian’s lovebird. In addition, evidence of blood parasites presence was also investigated to determine their general health. All samples (n = 48) tested negative for BFDV. Blood parasites were observed in 13 of the 48 samples (27 %). Investigation of virus occurrence in other known populations of the species is recommended to assess the conservation risk faced. Lilian’s lovebirds (n = 55) were mist-netted and ringed in LNP. Measurements showed that females were significantly larger than males. About 50 % of the birds ringed in October were half way through their primary moult indicating that moulting starts in earlier months possibly just after the breeding season in April. This study highlights three of the key threats (waterhole poisoning, habitat loss and predation) to the conservation of Lilian’s lovebirds in LNP and provides proposed actions to address these threats.
Ecology and evolution of the specialized hemipepsis-wasp (Hymenoptera : Pompilidae) pollination guild in South Africa.
(2011) Shuttleworth, Adam.; Johnson, Steven Dene.; Brothers, Denis John.
Pollinators are believed to have played a key role in the radiation of flowering plants. The Grant-Stebbins model of pollinator-mediated speciation, in which evolutionary shifts between pollinators result in phenotypic diversification and enforce reproductive isolation, is one of the most compelling hypotheses for the rapid diversification of angiosperms. A key principle in this model is that plant pollination systems tend towards specialization, resulting in convergent suites of floral traits (syndromes) associated with particular types of pollinators. However, the expectation of pollination system specialization is not always supported by ecological data and has also been questioned on theoretical grounds. In this thesis, I examine pollination by Hemipepsis spider-hunting wasps (Hymenoptera, Pompilidae, Pepsinae) and use this system to address questions about levels and proximal mechanisms of floral specialization, floral shifts and convergent evolution of floral traits. Specialized pollination by Hemipepsis wasps is a newly described pollination system within the angiosperms. I document pollination by these wasps for the first time in 15 South African grassland plant species, including two species of Eucomis (Hyacinthaceae) and 13 asclepiads (Apocynaceae: Asclepiadoideae). In one of the asclepiads, Xysmalobium undulatum, I describe a bimodal pollination system involving both Hemipepsis wasps and a cetoniine beetle. I also describe an unusual and potentially antagonistic pollination mechanism whereby wasps are systematically dismembered during the insertion of pollinia in the two asclepiads Pachycarpus asperifolius and P. appendiculatus. I have used these and previous case studies to establish the existence of a new pollination guild, consisting of at least 21 plant species (across 10 genera and three families), that are reliant on four functionally similar species of Hemipepsis wasp for pollination. Plants in the guild are distributed throughout the moist grasslands of eastern South Africa and flower from September through until early May, peaking in December/January. The Hemipepsis-wasp pollination guild is characterized by high levels of functional specialization (17 of the 21 known guild members are pollinated exclusively by Hemipepsis wasps), despite the absence of morphological adaptations to prevent non-pollinating insects from accessing nectar. I used field and laboratory based experiments to explore the function of floral traits in enforcing specialization. These showed that Hemipepsis wasps primarily use scent, rather than visual cues, to locate flowers, but I was unable to firmly identify specific compounds responsible for the attraction of these wasps (compounds that elicited antennal responses in preliminary GC-EAD experiments did not attract wasps in bioassays). The chemical composition of the floral scents of guild members was examined for 71 individuals representing 14 species in addition to previous studies, and found to comprise complex blends of volatiles (usually containing between 30 and 50 compounds), typically dominated by aliphatics and monoterpenes with small amounts of aromatics. I also showed that the floral colours of guild members are similar to background vegetation, suggesting that floral colours are adapted for crypsis to avoid detection by non-pollinating insects. Palatability choice experiments with honeybees showed that non-pollinating insects find the nectars of at least three of the asclepiad guild members distasteful. Plants in this guild thus appear to achieve specialization through biochemical filters (scent as an attractant and differentially palatable nectar) and cryptic coloration. Pollinator-mediated convergence in floral traits is the fundamental basis for pollination syndromes, but has seldom been rigorously analyzed. Flowers in the Hemipepsis-wasp pollination guild share several qualitative traits, including dull greenish- or brownish-white colour, often with purple blotches, exposed sucrose dominant nectar with a relatively high sugar concentration (typically over 50% sugar by weight) and a sweet/spicy fragrance to the human nose. To test for convergent evolution in guild members, I compared scent, nectar and colour traits of guild members to those of congeners with different pollinators. Although traits often differed between guild members and their congeners, I found little evidence for overall convergence in floral scent profiles and nectar properties, but floral colours in the guild were significantly closer to the colour of background vegetation than those of congeners. At this stage, the lack of knowledge about specific floral volatiles that influence Hemipepsis-wasp behaviour and secondary nectar constituents that limit non-pollinator visits makes it difficult to identify the extent of biochemical convergent evolution within the guild. The directions and functional traits involved in evolutionary transitions between pollination by Hemipepsis wasps and other vectors are currently difficult to ascertain as there is limited phylogenetic data for the plant families concerned. In the genus Eucomis, fly and Hemipepsis-wasp pollinated species are very similar in floral morphology and colour, but differ strongly in floral scent. Using manipulative field experiments in conjunction with detailed analyses of colour, scent and morphology, I was able to show that a shift between wasp and fly pollination could be induced simply by manipulating oligosulphides in the scent emission from inflorescences. When considered in combination with other experiments highlighting the importance of scent as a pollinator attractant for all guild members, this suggests that scent properties may have played a key role in the evolutionary transitions between pollination by Hemipepsis wasps and other vectors. This research has established that pollination by Hemipepsis spider-hunting wasps is more geographically and phylogenetically widespread than was previously known, and has confirmed that these wasps are important and consistent pollinators in southern African grassland ecosystems. I have shown that a distinct guild of plants is specialized for pollination by these wasps. The high levels of specialization within this guild highlight the effectiveness of biochemical filters and cryptic coloration in limiting the spectrum of flower visitors. The major challenge ahead will be to identify the floral volatiles that attract Hemipepsis wasps and the non-sugar constituents that make the nectars of some guild members differentially palatable. These would both contribute greatly to our understanding of floral specialization and the mechanisms involved in the radiation of the angiosperms.
The ecology and parasitology of small mammals from selected sites in Swaziland.
(2007) Mahlaba, Themb'alilahlwa A. M.; Perrin, Michael Richard.
The study was initially a long term study of the ecology of small mammals at Mlawula Nature Reserve in the eastern part of Swaziland. Due to the drought and dwindling numbers of rodents in the reserve the study was redirected to determining the factors resulting in the low numbers. The impacts of food and cover and grazing by the larger ungulates were studied. In addition, the age class distribution and gastro-intestinal parasites of small mammals were studied. A study of the small mammals in the Siphiso Valley of Mlawula Nature Reserve was conducted over four years from August 2000. The population density, biomass and composition of the small mammal community in the area were studied. The community comprised of Mus minutoides A. Smith, 1834, Mastomys natalensis (A. Smith, 1834), Lemniscomys rosalia (Thomas, 1904), Crocidura hirta Peters, 1952, Steatomys pratensis Peters, 1846 and Graphiurus murinus (Desmarest, 1822). Mus minutoides was the dominant species with pregnant females caught from November to May. Species richness varied significantly with the time of the year. The biomass, density and numbers of small mammals were low and by the end of the second year of the study, small mammal density was close to zero. Mastomys natalensis from a Middleveld study site, Luyengo, Swaziland were used to study the age structure of the population by means of eye lenses. The eye lens to age (in days) curve determined by Leirs (1994) was applied. A large percentage of M. natalensis in winter (June) were 2 months old while in spring/summer (October to March) the population consisted mainly of 3 month old specimens. A very low number of specimens were older than 4 months. This suggests a high mortality/removal rate of the young especially in the winter months. The impact of grazing pressure and rainfall on small mammal densities were investigated. High grazing pressure by ungulates rendered the habitat unsuitable for small mammals as it removed cover and encouraged colonization by alien invasive plant species. This effect was exacerbated by diminishing and unpredictable rains, such that mild grazing pressure negatively impacted on small mammal communities and on individual species. When the small mammals disappeared from the study site, M. natalensis was reintroduced to determine the factors that led to the disappearance. Supplementary food resulted in the longest persistence of the reintroduced mice while the impact of additional cover was small. Predation was likely responsible for the rapid decline of the reintroduced mice. Small mammals were examined for ectoparasites and gut parasites as these were thought to negatively impact on their physiology and reproduction. Ectoparasites collected included the ticks Ixodes sp. and Boophilus sp., the mite Allodermanyssus sp. and another species of mite. The gastrointestinal tracts contained the helminths Syphacia sp., Heligmonina sp., Trichuris sp., Protospirura sp., two unidentified nematode species and different cestode species. A new species of heligmosomoid nematode is described and named.
The ecology of large-spotted genets within an urban landscape.
(2015) Widdows, Craig David.; Downs, Colleen Thelma.
Urbanization is one of the most damaging and rapidly expanding forms of anthropogenic landscape modification and is having profound consequences on biodiversity worldwide. The global increase in urbanization has resulted in exclusion of many carnivore species from human-altered landscapes due to a variety of anthropogenic impacts. However, despite the negative impacts of urbanization on carnivores, certain species such as large-spotted genets (Genetta tigrina) exhibit an ability to persist within urban areas. Despite their extensive distribution range, large-spotted genets are poorly studied in comparison to other African carnivores, with a handful of studies conducted on genetics, activity patterns and diet. Furthermore, no studies have focused on their ecology in an urban environment. There have been increasing reports of large-spotted genets within urban areas throughout KwaZulu-Natal, South Africa. The mosaic of patches of native vegetation within this urban landscape provides habitats for a variety of wildlife species. The main aim of the study was to investigate the ecology of large-spotted genets within an urban landscape and to determine what factors facilitate their ability to persist in an urban environment. Residential interviews were conducted to ascertain information pertaining to behavioural observations, land use as well as wildlife conflict and public perceptions of genets. Chi-square (x2) goodness-of-fit tests were used to determine significant differences in the frequency of responses. Domestic pet food was the main food item genets were observed eating. The most cited cause of genet fatalities were attacks by domestic animals and collisions with vehicles. Genets were reported using roof spaces for resting during daylight hours and as locales for breeding. The majority of respondents expressed positive attitudes towards genets in urban areas; negative views stemmed from concerns of disease transfer and impacts on wild bird populations. We investigated the relationship between occurrence of large-spotted genets with various environmental variables believed to influence their site occupancy and detection in an urban environment. Presence/absence data was collected from 28 camera trap stations between June 2012 and October 2013 in Kloof, KwaZulu-Natal, South Africa. Average estimated occupancy of urban genets was 0.62 ± 0.14 with a detection probability 0.19 ± 0.03. Model selection indicated that bush cover and placement of camera traps on wide paths negatively influenced large-spotted genet occupancy. Both winter and fringe habitats influenced the site occupancy of large-spotted genets positively. Furthermore, bush cover was negatively associated with detection probability of urban genets. The dietary composition and the influence of predictable feeding stations on urban large-spotted genets were investigated through scat analysis. Scats were collected on a monthly basis over a year from eleven midden sites. Invertebrates were the dominant prey items consumed with small mammals also forming an important component of the diet. Significant seasonal variation was recorded with the presence of birds and pollution in the scats with highest recorded frequencies during spring and winter respectively. During winter, when invertebrate abundance declined, urban genets increased their intake of anthropogenic refuse resulting in plastic, elastic bands and various other waste products present in the scats. We investigated the effect of anthropogenic structures on the roost temperatures of large-spotted genets. Roost temperatures were recorded using i-Button® temperature loggers at known genet roosts in anthropogenic structures as well as in natural roost sites (tree hollows and rocky overhangs). Over the seasons temperatures varied significantly between months and among different roosts. However, anthropogenic roost temperatures were significantly higher than ambient temperatures throughout the study period. Furthermore, anthropogenic roosts had higher temperatures (with lower variability) than natural roost sites. This study indicated the importance of anthropogenic structures as daytime roosts and for breeding for large-spotted genets within an urban matrix. Given their adaptability and apparent success within the urban environment, we investigated the movement ecology of large-spotted genets within the urban landscape. Large-spotted genets were captured and fitted with global positioning system mobile transmitters. Although seven individuals were trapped, detailed data were only obtained for two individuals. Minimum convex polygons (MCPs), 95% and 50% kernel density estimates (KDEs) were calculated for a male and female large-spotted genet. The 95% kernel density home range sizes showed relatively small home range sized for both individuals, with an area of 48.2 ha (female) and 17.5 ha (male). Habitat selection within home ranges indicated that the male large-spotted genet preferred urban residential habitat while the female genet avoided nearby croplands. Both individuals used most of the habitats within their study area. Variable habitat used by both individuals in this study confirmed the species’ ability to adapt to the urban mosaic of habitats. This thesis showed the importance of a variety of factors on the distribution of large-spotted genets in landscapes where natural habitats are threatened by changing land use and increasing human populations. Furthermore, this thesis illustrated the ability of genets to live in an urban mosaic landscape by using a variety of anthropogenic resources.
Ecosystem carbon change of shrub-encroached grasslands across a precipitation gradient in South Africa.
(2015) Mureva, Admore.; Ward, David Mercer.
Abstract available in PDF file.

Browse

Browsing Doctoral Degrees (Ecology) by Title