Masters Degrees (Ecology)

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Aardvark and people: can a shy species be widely known in a localised area?
(2022) Makwati, Nolutho.; Kraai, Manqhai.; Tsvuura, Zivanai.
The increase in human populations has led to humans sharing space with wild animals even in the natural habitats of the animals. Conflicts may arise when people and wildlife attempt to fulfill their needs which can be detrimental to one or both parties, and this type of conflict is called human-wildlife conflict (HWC). The human needs include people hunting wild animals for consumption of the animal and trading in animal body parts.Hunting is one of the factors that decreases populations of numerous animal species, and it occurs in many parts of the world e.g. in Africa, Asia and South America, where it contributes to extinction of species. The conservation and management of burrowing animals is a major challenge due to their elusive and nocturnal behaviour. The aardvark is an African medium-sized, burrowing mammal whose conservation status has not been updated recently due to the difficulties associated with studying nocturnal animals. Aardvarks may play a significant ecological role in the ecosystems in which they occur, such as by changing the landscape through their digging activities, or through affecting the dispersal of seeds. Therefore, the aim of this study was to explore the influence of humans on population trends and activity patterns of aardvarks outside protected areas, and to determine people’s perceptions about the animal. The study was conducted in Ncunjane village in Msinga Local Municipality, KwaZulu-Natal Province of South Africa. To understand people’s perceptions about aardvark in their community, I used a semistructured questionnaire survey. I asked personal information of the participants (sex, level of education and age), and questions related to people’s perceptions about the aardvark, such as people’s knowledge, myths, and their uses of the animal or its body parts. To determine activity patterns of the animal, I focused on aardvark foraging activities in a semi- arid savanna ecosystem that is also used as a communal rangeland over eight months between 2020 and 2021. I measured and quantified aardvark foraging holes using 53 50 m × 10 m transects where there was evidence of aardvark activity. In addition, I quantified aardvark burrowing of dens in the dry, wet and early dry seasons using walking transects guided by a research assistant who knows the area. I found that people have different perspectives about aardvark with the majority (78%) of respondents having strongly positive perceptions. The positive perceptions arise from aardvark not causing physical harm to people, and fleeing away upon sighting people. I found that aardvarks were mainly hunted for meat while some animal body parts were sold to traditional healers for traditional medicine. All seasons consisted of a greater number (> 51%) of old than new and very old foraging holes.The surface area of new, old, very old holes differed significantly with season (P < 0.0001) and the depth of new, old and very old holes also varied with season (P < 0.0001). In addition, the contents of foraging holes varied with age of the hole and season in that new holes lacked evidence of plant life across seasons. Aardvark dens were used by other animals such as spiders, wild cats, Cape porcupines and snakes. Hence, an increase in aardvark holes can be associated with significant landscape heterogeneity for vegetation and animal life. Aardvarks in Ncunjane fed close to their dens presumablyto mitigate against human predation through hunting threats, which may directly affect the extent of aardvark digging activities. These results show that aardvarks may be categorised as ecosystem engineers as the burrows provide shelter for other animals, also, their effects on other animals are disproportionate to their abundance. These results highlight that aardvarks are threatened by human uses and may decline in abundance in the area. Finally, aardvarks remain poorly studied in landscapes shared with humans. Further studies to assess aardvark numbers in human-dominated landscapes are required which can raise awareness and play a significant role in conservation of aardvarks.
The prevalence and implications of non-native wild boar Sus scrofa in KwaZulu-Natal, South Africa.
(2023) James, Claudette Njabulo.; Downs, Colleen Thelma.
Humans’ introduction of species into areas where they do not naturally occur has led to ecological and economic havoc. Introduced species can become invasive, exerting negative pressures on native species and the environment. Wild boar (Sus scrofa) is distributed worldwide except for Antarctica. The species is highly destructive and has been regarded as an invasive alien species in many parts of the world. Researchers have done many studies on wild boar investigating various aspects of the species, such as its biology, biochemistry, ecology, epidemiology, genetics, and archaeology. Invasive animals' effects on the environment and ecological systems were explored and focused on the impacts of exotic mammals, with wild boar as the species of interest. The potential for invasive spread by the European wild boar in South Africa was assessed by determining potentially suitable habitats using bioclimatic variables and the maximum entropy model, and then related to the present distribution records of the species in the country. Wild boars were found to have great potential to extend their invasive distribution range in South Africa. The prevalence of feral wild boar in KwaZulu-Natal (KZN) Province, South Africa, was investigated using camera trap surveys. The camera trap surveys revealed that there were no feral wild boar populations in the Midlands of KZN, but in other parts of KZN. The selling of wild boar in relation to the present legislation on wild boar in South Africa is illegal. The selling of wild boar contributes to the spread of the species in the country, as determined in this study. We recommend that the sale of wild boar should be monitored in South Africa by conservation authorities and the animals confiscated from the offenders and euthanised to prevent the further uncontrolled spread of the species. Moreover, we recommend the revision of the legislation regulating wild boar in South Africa to prevent the uncontrolled spread of the species in the country.
Assessing the trade of reptile species in the South African pet trade.
(2021) Mantintsilili, Asekho.; Downs, Colleen Thelma.; Shivambu, Tinyiko Cavin.; Shivambu, Ndivhuwo.
Despite the negative impacts that the pet trade has on the native and non-native biodiversity, economy and human health, the research suggests that the demand for pets and the extent of trade in live animals as pets has increased dramatically over the years. As a result, many species, including reptiles, have been translocated and introduced into new or non-native environments. Some of these have established feral populations, become invasive and are causing significant environmental and socio-economic impacts on non-native environments. Reptiles are among the most popular groups of animals in the pet trade industry globally. Trade in pet reptiles in South Africa is large and one of the major pathways through which non-native species, including invasive species, are introduced into the country. Despite this, little is known about the dynamics of the wildlife trade in pet reptiles globally. To understand the dynamics of the global trade in pet reptiles, we carried out a comprehensive literature search to gather relevant information from reptile pet trade-based publications. We further compiled a list of traded pet reptiles from all South African physical pet stores and online advertising websites to determine which species are traded, pose an invasion risk and have potential environmental and socio-economic impacts. We found a total of 39 publications based on the reptile pet trade from 1994 – 2021 worldwide. Our analyses revealed that the research effort was not uniform globally, with the majority (63.6%) of all relevant studies originating from three continents (Asia, Europe, and North America). Moreover, the United States of America (North America) and Indonesia (Asia) produced the greatest research outputs (12.1% each) compared with other countries across the world. We found at least 1140 reptile species belonging to 60 families involved in the global pet trade, with invasive red-eared slider Trachemys scripta elegans being the most frequently studied species (number of studies = 23/39). Of the recorded species, at least 79 are invasive, 46 endangered, 29 critically endangered, while only 546 are CITES-listed. In terms of reptile species sold in South Africa, we recorded a total of 2771 individuals representing 88 unique reptiles, 69 from physical pet stores and 18 from online advertising websites. KwaZulu-Natal, Gauteng and Western Cape Provinces had the highest number of pet stores and online advertising websites; therefore, they subsequently recorded the highest number of pet reptiles compared with other provinces. Physical pet stores were found to have the highest number of species compared to online trade. Of the recorded species, 76 are nonnative, and 15 of these are invasive to South Africa. Moreover, only 32 pet reptiles are listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). For current distributions, red-eared slider Trachemys scripta elegans, P. guttatus, and Western diamondback rattlesnake Crotalus atrox had the largest predicted climatic suitability. The future predictions for the latter two species were predicted to increase, while red-eared slider suitability shifted. Some species, such as Burmese pythons Python bivittatus, showed low invasion risk based on climatic suitability. However, given their large body size, history of invasion and their popularity in the pet trade, they are most likely to escape or be released from captivity and become invasive. A total of 76 reptile species were assessed for environmental and socio-economic impacts using the Generic Impact Scoring System (GISS), Environmental Impact Classification for Alien Taxa (EICAT), and Socio-Economic Impact Classification for Alien Taxa (SEICAT). Using GISS, we found that 13 species had environmental impacts (E_GISS), while 11 species had socio-economic impacts (SE_GISS). For EICAT and SEICAT, 13 species had environmental impacts, and eight had socio-economic impacts, respectively. The most popular pet species, red-tailed boa Boa constrictor, green iguana Iguana iguana, P. bivittatus, T. elegans, and central bearded dragon Pogona vitticeps had impacts in all the three scoring schemes. The later species and corn snake (Pantherophis guttatus) scored the highest for all impact schemes. Species sold in high numbers, with large climatically suitability and potential impacts, are more likely to establish feral populations and become invasive should they escape or be released from captivity. We, therefore, recommended that the trade in pet reptiles should be constantly monitored to avoid new introductions and the implications that the pet trade may have to the country.
Development and application of novel ornithological survey methods for the detection of cryptic avian indicator species that predict grassland health.
(2021) Beaumont, Stuart Nicholas.; Downs, Colleen Thelma.
The anthropogenic pressure on South African grasslands to meet the needs of the burgeoning human population has exposed them to extensive permanent transformation and degradation. Indicator species may identify changes in the grassland ecosystem. One such indicator species for natural sourveld grassland condition in South Africa is the red-winged francolin (Scleroptila levaillantii), whose population density is negatively correlated to grazing intensity and annual burning. Pointing dogs (Canis lupus familiaris) have been used extensively to aid ecologists in detecting these and other cryptic gamebirds to establish abundance. Here, a reliable method was developed to count cryptic gamebirds in the Greater uMgeni Vlei Expansion Area, KwaZulu-Natal Midlands, South Africa, where the route through a survey site was flexible. A variation to the existing distance sampling technique was proposed where the dog global positioning system (GPS) track was the transect line. The study investigated the effect of varying environmental conditions on the distance from which a pointing dog could reliably and consistently detect a bird and allow calculating a detection distance based on influential environmental variables. Between March – October 2021, using pointing dogs fitted with GPS devices, controlled and uncontrolled trials were conducted on Japanese quail (Coturnix japonica) and red-winged francolin in their natural habitat, respectively, to establish the environmental conditions that affect detectability and the detection distance from which a dog can detect a bird of known location. A total of 21 surveys were conducted (August 2020 – October 2021), on four survey sites by one or two pointer dogs fitted with GPS devices, to establish the population densities and territory of red-winged francolin. Individual area of search, established from the detection distance based on nominal wind speed and GPS track, was calculated. The redundancy in area of search enabled the evaluation of relative proficiency of detection of red-winged francolin. Of the environmental variables monitored, only nominal wind speed significantly influenced detection distance, where an increase of one-knot wind strength resulted in an increase in detection distance by 0.64 m. This enabled an area of search, considerate of influential environmental conditions, to be derived and the probability of detection within that search area = 1. Results showed significantly better precision and accuracy when surveying with two dogs when compared with one dog. The calculation of detection distance, where the probability of detecting a bird at this distance = 1, addresses the bias of varying scenting conditions. The established area of search, where the probability of detecting a bird within this area = 1, addresses the situation where known coveys in an area of known size remain undetected. Since the area of search is independent of time spent searching and normalised for redundancy, the bias introduced by varying physical aptitude is mitigated. Consideration for the application of this method should be given to the environmental conditions under which the surveying is planned since the detection distance function is derived for conditions at the present study sites. These techniques, based on a variable survey route through the survey site, may be used by citizen scientists to assist land managers, conservationists, and ecologists in establishing the abundance of red-winged francolin, contributing to burning and grazing regime management to enhance conservation efforts for the species.
Interactive effects of fire history and elevated 2 temperature on aboveground productivity in a high 3 altitude mesic grassland in South Africa.
(2021) Mvelase, Thembeka Ayanda.; Tedder, Michelle Jennifer.; te Beest, Mariska.
Abstract available in PDF.
Role and effects of wild southern African ungulates on seed dispersal of selected alien invasive plants.
(2021) Msweli, Lindelwa Sibongakonke.; Downs, Colleen Thelma.; Zungu, Manqoba Moses.
Abstract available in PDF.
Ant community responses to fertiliser application and disturbance in a mistbelt grassland, KwaZulu-Natal.
(2021) Khoza, Lindiwe Rebecca.; Munyai, Thinandavha Caswell.; Andersen, Alan N.
Abstract available in PDF.
The contribution of goats to household food security in selected communities of KwaZulu-Natal, South Africa.
(2021) Khowa, Anele Aurelia.; Kraai, Manqhai.; Tsvuura, Zivanai.
The growth of the human population in the world has been occurring at a rapid rate. This presents a challenge of how the world food demands will be met. These challenges are always felt the most in developing countries, and result in a lot of people in developing countries turning to alternative sources of income other than employment to manage their food situation. One of the alternatives includes a reliance on animal husbandry in order to meet and improve their livelihoods particularly with respect to food. Furthermore, small-scale farming of animals such as goats, sheep, pigs and chickens has also been an income source when the animals are sold. In developing countries, pastoralism and agro-pastoralism frequently occur among disadvantaged communities, who are often found in arid or semi-arid regions. As a result, goats have been shown to be an important type of livestock that can be kept in such conditions without financially stressing their owner by requiring constant care of supplementary feeds and medication. Goats are known for their resilience which allows them to cope with stressful conditions while being able to reproduce. This resilience and productivity of goats allows their owners to be able to liquidate them for cash if there is a need and also be able to slaughter them for their household consumption. Here, I investigated the contribution of small-scale goat farming to household food security in rural and peri-urban areas in KwaZulu-Natal (KZN), South Africa. The study was carried out in rural and peri-urban areas of Msinga, Kokstad, Howick and Pietermaritzburg in KZN. I used structured questionnaire surveys to determine the contribution of goats to household food security from the farmers’ responses. The questions asked related to the sale of goats (number, sex, age and sale value of the animal) and how the money generated from goat sales was spent. The study also determined goat sales from 27 households in three villages occurring in Msinga over a 2- year period of 2017 to 2018. I also assessed the participation of small-scale farmers in two livestock auctions, which took place in 2019 and 2020 by recording the age, sex, and coat-colour of the animals taken to auctions. The results obtained from the study showed that goats played a role in household food security as a source of cash as well as consumption in strenuous times. These findings of the study highlight that smallscale goat farming provides an alternative food source and income source for disadvantaged farmers. These findings were more prevalent in the rural areas, which kept more goats than those found in the peri-urban areas. Goats in rural areas ranged from 5 to 150 goats in a herd, and 5 to 50 goats in a herd while in periurban areas. Goats were a source of cash in numerous ways including sale of skins after slaughter that are used to craft household items such as stools that can be sold for cash. Adult goats were sold more at the farmers’ homesteads than auctions where buyers opted for younger goats. My results also showed that small-scale farmers use all possible avenues to sell their goats, as they sold a high number of animals from home and did not depend on infrequent livestock auction events. However, there were benefits derived from participating in auctions in terms of the relatively higher prices obtained there. For example, female and male goats sold for R2 177 and R1 268, respectively at auctions. The price was similar for females (R1 083) and males (R1 065) in homesteads. At auctions, female and male goats sold for R2 177 and R1 268, respectively. From homesteads, female and male goats sold for R1 083 and R1 065, respectively. Colour of goats proved to be an important trait at auctions as light-coloured goats were in higher demand than black goats. Homestead sales also remain a useful practice as farmers generate income to assist in day-to-day household expenses instead of waiting for infrequent auction events. Furthermore, small-scale farmers who plan to participate in auctions should pay attention to the characteristics (age, colour, and sex) of their animals when populating their herds. Sub-adult, light-coloured and female goats were the animals that were highly sought after at auctions.
Protected area management and planning challenges: sustainability and integrity – a cursory investigation of the role of the management plan.
(2021) Goosen, Magda.; Downs, Colleen Thelma.
Formally established protected areas in South Africa date back to the turn of the 19th century, yet requirements for protected area management plans only became mandatory approximately a century later. Before the promulgation of the Environment Conservation Act No. 73 of 1989 and subsequently the World Heritage Convention Act in 1999 and the National Environmental Management: Protected Areas Act 57 in 2003, requirements for management plans were voluntary, and guidance to its content was fragmented across various international, national and provincial policy instruments. There has been little academic debate on the relevance and content of protected area management plans to date and how such a long-term planning document can respond to emerging threats and opportunities. An improved understanding of these plans, and the role they play in biodiversity conservation, is required. The aims of this investigation were two-fold. The first was to gain insight into the challenges of effective management of protected areas, the long-term protection and sustainability of these areas, and, notably, the management plan’s role in addressing these challenges. The second was to evaluate the contribution and legislative weight that the management plan has in the efficient management, sustainable and ethical use, and long-term sustainability of protected areas within South Africa. Given that the above aims cover a potential insatiable field of research, this thesis was focused on the legal and policy framework for management plans and the management plans role in effectively managing these areas. Within this context, the following questions were addressed: ▪ What is the role of management plans in the effective management of protected areas? ▪ How does the legal and policy framework ensure that the derived plan is relevant and achievable and ultimately accomplishes the protected area purpose? ▪ What decision-making principles should be considered to facilitate sustainable and ethical use of protected areas, and what role does protected area management plans play in ensuring justifiable use of protected areas? ▪ What are the consequences when a long-term public-interest decision potentially isolates it from its transfrontier context, and what is the legislative weight of the management plan in mitigating such consequences? ▪ What role does the management plan, a long-term planning document, play in mitigating the impacts of or responding to immediate emerging threats and opportunities? It was found that despite being the principal legislative framework for management plans, the World Heritage Convention Act and the National Environmental Management: Protected Areas Act did not consolidate the plethora of management plan requirements for protected areas. As a consequence, the legislative provisions for protected area management plans were, in several instances, fragmented, conflicting and ambiguous. A consolidation of relevant provisions in these two statutes together with emerging best practice is, therefore, recommended. This consolidation may also provide greater clarity on the contemporary understanding of the contribution of protected areas to conservation and people’s well-being, i.e. it may entail a refurbishment of the ‘purpose’ of protected areas. Furthermore, the parallel evolution of the management of protected areas, the recreational use of these areas, and protected area management plans over the last century have brought about a complex relationship between these three aspects. Because of the fragmentation of legal and policy frameworks relating to these aspects, a need for a consolidated decision-making framework that provides for the basis for ethical and transparent decision-making could exclude inconsistent interpretations of legislation and policies. Incorporating such a decision-making framework in the protected area management plan can enhance transparency and accountability by the State or management authority to fulfil its fiduciary duty. Understanding of the above aspects was enhanced through a literature review and a case study of a development application in the area bordering the Tembe Elephant Park. The case study highlighted some of the potential consequences of a long-term public-interest decision that isolates a protected area from its transfrontier context and the role of an adaptive management plan in responding to these impacts and other current emerging threats and opportunities. A robust management plan remains the most relevant planning tool to address the complexities around protected area management and the fragmented legislative and policy frameworks for the effective management of protected areas in South Africa. Whereas management plans cannot be expected to cover explicitly every emerging circumstance – the principles included in such plans should provide the necessary guidance to decision-makers for unique circumstances and decision making.
Influences of bush encroachment and intensity on small mammals in a mesic savanna, Pretoria, South Africa.
(2021) Zwane, Thabile Jane.; Kraai, Manqhai.; Tsvuura, Zivanai.; Tjelele, Julius Tlou.
Abstract available in pdf.
Aspects of the urban ecology of the Spotted Thick-knee (Burhinus capensis)
(2021) Josiah, Kyrone Kent.; Downs, Colleen Thelma.
Abstract available in PDF.
Ecology of the South African giraffe (Giraffa camelopardalis giraffa) across a land-use gradient in central KwaZulu-Natal, South Africa.
(2020) Nyathi, Memeli Jefrey Jethro.; Downs, Colleen Thelma.; Calverley, Peter Markham.
Abstract available in pdf.
Parthenium hysterophorus distribution and efficacy of control in Hluhluwe-Imfolozi Park, northern KwaZulu-Natal.
(2020) Mbatha, Sethabile Khwezi.; Tedder, Michele Jennifer.; Carbutt, Clinton.; Mutanga, Onisimo.
Abstract available in pdf.
Impacts of foraging behavior [sic] by Cape porcupines and their effects on nutrient cycling in mesic savannas.
(2021) Kraai, Unathi Masiobi.; Tsvuura, Zivanai.; Kraai, Manqhai.; Mkhize, Nthuthuko Raphael.; Mgqatsa, Nokubonga.; Tjelele, Julius Tlou.
Through feeding and associated activities, herbivores play a major role in determining the structure of savannas. The Cape porcupine (Hystrix africaeaustralis) is a semi-fossorial, large (ca. 12 kg) herbivorous rodent with a generalist foraging strategy that feeds on plant parts occurring above- and below ground. Subterranean foraging by porcupine may influence biotic and abiotic processes in that area. The extent of soil and vegetation perturbation may be pervasive on the landscape so that these animals may be considered as ecosystem engineers. The digging activities of ecosystem engineers are significant as they influence soil properties (e.g. nutrient cycling) including germination of trapped seeds and establishment of seedlings. These changes may occur at small and large scale on a landscape. The utilisation of woody vegetation and ecosystem engineering by such animals, particularly by shy and nocturnal species, is understudied in African savannas. The study was aimed at: (1) quantifying the extent of herbivory by the porcupines on target trees during the wet and dry season in three mesic savanna sites, and (2) evaluating the effects of Cape porcupines’ digging on nutrient cycling (total carbon and total nitrogen) and quantify establishment of vegetation on the mounds. Sampling was undertaken at three mesic savanna sites in South Africa: (i) Roodeplaat Farm in Gauteng Province; (ii) Goss Game Farm; and (iii) Bisley Valley Nature Reserve, both in KwaZulu-Natal Province. I used 30 m × 30 m plots to quantify porcupine foraging holes and bark damage on adult trees at Roodeplaat and Goss while 10 m × 10 m plots were used at Bisley where porcupines foraged on seedlings and saplings of woody plants. I also collected porcupine dung samples over the dry and wet season for micromorphological examination of porcupine diet. I collected soil samples from the mound soil of foraging holes and from adjacent locations within 0.5 m of the hole for analysis of amounts of total carbon and total nitrogen. Measurements of foraging holes comprised of two perpendicular diameters on the soil surface and the maximum depth. Porcupines utilised different tree species of various sizes at the three sites while targeting specific parts of these trees. At Roodeplaat, porcupines targeted Vachellia robusta on which they consumed the trunk part immediately below ground, whereas at Bisley, roots and the lower trunk of V. nilotica seedlings and saplings were utilised, also through digging holes while the bark of the lower trunk (up to 0.7 m) of Spirostachys africana trees was stripped off at Goss. I found that 70% of young V. nilotica trees in or adjacent to holes in Bisley were scarred or destroyed as a result of porcupine feeding on them, while 16% of S. africana trees were wounded at Goss. Only 7% of V. robusta trees were damaged at Roodeplaat. In Bisley, I found that grasses and forbs established faster on the mound than on the surrounds, i.e. seedlings germinated first on the mound than the adjacent not disturbed soil. I also found that foraging holes provide shelter to other animals especially those from the arthropod group e.g. spiders. Amounts of total carbon and total nitrogen were similar between the mounds and undug soil. These findings are discussed in terms of nutrient cycling through digging, breaking down of plant parts and herbivore-induced mortality of main tree species. I argue that tree thinning from ringbarking by porcupine through their foraging activities ameliorates woody plant encroachment in mesic savannas.
Effects of increased temperature on growth and nutritional value of mesic grasslands, with or without woody legume seedling competition.
(2020) Gili, Nikilita.; Tedder, Michelle Jennifer.; Scogings, Peter Frank.; Mkhize, Nthuthuko Raphael.
Mesic grasslands are complex ecosystems covered in grasses and other graminoid vegetation. The species composition varies due to variation in rainfall and temperature; these grasslands are climatically supported. They also vary in nutritive value and grasslands with high species richness have low nutritive value because grasses differ genetically. Grasses’ response to high temperature and competition is species dependent. Grasslands are ideal for ecological experiments because grasses grow fast and their response to environmental changes is noticeable. Therefore, an experiment of induced warming with legume seedlings interaction was conducted at the University of KwaZulu-Natal, using open top chambers and Vachellia sieberiana var. woodii. This was done to determine the effect of increased temperature on the biomass, growth, morphology and nutritive value of Themeda triandra and Aristida junciformis. These species were chosen because they occur naturally and dominate in the Ukulinga farm, where the experiment was conducted. They also have contrasting palatability, T. triandra is highly palatable and A. junciformis is less palatable. Vachellia sieberiana seedlings were grown from seed and transplanted after two months to the field to interact with grasses for four months. The results suggest that the interaction of warming and woody seedlings reduces the biomass of the investigated species. This implies that warming reduces grass biomass. Plant traits such as grass height, leaf area, tiller width and tuft diameter responded differently to the treatments. The fibre (neutral detergent fibre) of T. triandra was increased by warming. The interaction of warming and woody seedlings had no effect on the regrowth fibre content. The interaction of warming and woody seedlings increased the protein content of A. junciformis. Warming and woody seedlings independently increased the protein content of T. triandra. The response of plants to increased warming will help ecologists understand the effects of global warming. To provide more insight into these findings, further research on specific species with longer experimental duration and high woody seedling neighbour density is of importance.
Fleshy-fruited invasive plant species in KwaZulu-Natal, South Africa: native avian seed dispersal and impact assessment.
(2019) Bitani, Nasiphi.; Downs, Colleen Thelma.
Globally, alien plant species have been recognised as a major threat to biodiversity. The increased global trade and travel have resulted in the increased introduction of new species. Direct or indirect introductions of alien invasive plant species result in altered ecosystem functioning, negatively affect economies, human health and wellbeing. In forest systems, habitat fragmentation has major impacts on biodiversity including the facilitation of alien invasions. Habitat alteration creates disturbance zones that are associated with increased invasion success. South Africa, like other parts of the world, is severely affected by alien plant species. Fleshy-fruited invasive species are amongst the most damaging invasive species with major environmental, social and economic impacts. Fleshy-fruited invasive plant species integrate into local seed dispersal networks and form mutual relationships with local avian seed dispersers leading to increased invasion potential. The success of avian mediated seed dispersal is influenced by the functional traits of both the plant and avian seed dispersers. Considering the negative impacts of fleshy-fruited alien invasive species it is important to understand ecological processes leading to their successful spread and if high priority species are being targeted for management to guide policy and conservation. Understanding avian mediated dispersal is important as it gives insights into the species that could promote alien plant invasion. The aim of the present study was to assess avian seed dispersal, and ecological and socio-economic impacts of fleshy-fruited alien invasive plant species. The objectives were to (1) predict avian seed dispersers of fleshy-fruited alien invasive plant species; (2) determine the assemblage of native avian species potentially dispersing the seeds of Lantana camara; and (3) determine the socio-economic and ecological impacts of fleshy-fruited alien invasive plant species. Firstly, we predicted the avian seed dispersers of fleshy-fruited invasive plant species in the Indian Coastal Belt Forest of KwaZulu-Natal Province, South Africa using functional traits of avian species (body mass, gape width, bill length, degree of frugivory, foraging strategy, abundance and habitat specificity) and fleshy-fruited invasive plants (crop size, fruit size, seed size, number of seeds, plant height, plant habitat, fruiting period and derived invasiveness score). The results showed that small, abundant forest generalist avian species were potentially effective dispersers of fleshy-fruited invasive species. Fleshy-fruited invasive plant species that were more likely to persist in the disturbed Indian Coastal Belt Forest through avian-mediated seed dispersal were small-seeded, open habitat plants with relatively longer fruiting duration. Secondly, we assessed the role of native avian species in the potential dispersal of a highly invasive shrub Lantana camara of the family Verbenaceae in Pietermatzburg, KwaZulu-Natal, South Africa. Avian species visiting L. camara were observed and potential dispersal distances estimated. The results showed that native avian species were potential seed dispersers of L. camara were mostly relatively small, moderately frugivorous avian species. The dark-capped bulbul (Pycnonotus tricolor) showed relatively high visitation frequencies to L. camara and was more likely the main effective dispersers of the plant. Potential seed dispersal distances were shown to range from 9 to 45 km and long distance seed dispersal distances were shown to be rare and only limited by rarely large avian frugivores. Lastly, we assessed the ecological and socio-economic impacts of fleshy-fruited invasive species using the generic impact scoring system. The results showed that fleshy-fruited invasive plant species have both socio-economic and environmental impacts. The highest environmental impacts were shown to be on ecosystem and vegetation, or plant and the highest socioeconomic impacts were on agriculture, forest production and human health. The results presented in this thesis provide essential insights into the importance of avian mediated seed dispersal in the invasion of fleshy-fruited invasive plant species. The findings of the study also highlight the importance of predictive approaches in informing the management of invasions and showed fleshy-fruited invasive plant species with high socio-economic and ecological impacts. Knowledge of species with high impacts will help in guiding resource allocation and preventing the introduction of high-risk species. Also, ecologists and other decision-makers should consider ecological processes that are leading to the spread of invasive plant species in management practices or plans.
Assessment of the current ecological integrity of the uMngeni River, KwaZulu-Natal, South Africa, using fish community structures and attributes of the Labeobarbus natalensis (Castelnau, 1861) populations.
(2019) Dlamini, Pumla Vanessa.; Downs, Colleen Thelma.; O'Brien, Gordon Craig.
Rivers are the main source of freshwater water for human communities and provide people with numerous ecosystem services such as water purification, transportation, power generation, food supply, and water for domestic, agricultural and industrial use. Water resources, and the ecosystem services they provide, are particularly important in developing countries, such as South Africa. The uMngeni River, is a strategic resource that provides water to two of the largest cities in KwaZulu-Natal Province (the uMgungundlovu and eThekwini municipalities), with more than four million people, making it socio-economically important. As such, to maintain sustainability the protection of the river is important. However, in South Africa and KwaZulu-Natal, the impact of anthropogenic activities has made riverine ecosystems one of the most threatened types of ecosystems in the world. The use of fish as key indicators of the ecological state of aquatic ecosystems is well established as their vulnerability to environmental change, mobility, longevity and relative ease of species identification make them good indicators. This study evaluated the current ecological integrity of the uMngeni River in KwaZulu-Natal using multiple lines of evidence including fish communities and the state of Labeobarbus natalensis (the KwaZulu-Natal yellowfish) populations, and environmental variables. The research was undertaken in the major man-made lakes (dams) in the uMngeni River (namely Midmar, Albert Falls, Nagle and Inanda Dams) and in the rivers of the uMngeni Catchment. Abiotic lines of evidence investigated included water quality and habitat, while the biotic lines of evidence included fish community structures and attributes of the population of L. natalensis. Fish community structures at eight selected River Eco-status Monitoring Programme (REMP) sites in the uMngeni catchment were considered. This included consideration of how the fish communities responded to changes in a range of environmental variables and alien fishes using the Fish Response Assessment Index (FRAI), we were able to determine that the ecological integrity of the uMngeni River decreases in a downstream gradient from the upper reaches of the catchment to lower reaches, due the synergistic effect of multiple anthropogenic stressors. The multivariate analyses indicated that the anthropogenic impacts responsible for shifts in fish community structures, and the associated ecological integrity of the river were related to changes in instream habitats and water quality stressors primarily. Most of the environmental changes identified can be linked to flow modifications and land use activities throughout the uMngeni catchment. Assessments of attributes of the L. natalensis populations from large instream impoundments in the uMngeni River (namely Midmar, Albert Falls, Nagle and Inanda Dam) resulted in diminishing wellbeing of the populations of this endemic migratory fish progressively both in abundance and structure, down the length of the catchment. The quality and quantity of water diminished down the catchment gradient with this gradient and the effect of the barriers themselves can partially be attributed to the impaired state of the populations. Impoundments are not preferred by juvenile and young L. natalensis that prefer shallow riffle habitats that are lacking in dams, the occurrence of many predatory alien fishes in the dam can also be attributed to the absence of small yellowfish in the dams. The outcomes of this study can contribute to the sustainable management and development of conservation plans for the rivers and dams in the uMngeni catchment. Major stressors that should be mitigated include the barrier effect and operation or flow releases from the large dams and smaller weirs etc. that cause river fragmentation in the catchment. It is recommended that management plans for the conservation of the fishes in the catchment should be developed which is achievable as the current supply of resources in the catchment is balanced with the demand for use. Fish passages should be established in all of the dams in the uMngeni River to allow migratory fish free passage along the river and to re-establish river connectivity processes. Additionally, the removal of redundant weirs or partial man-made barriers is recommended to alleviate the effects of fragmentation particularly on the yellowfish in the catchment. More research is required to understand the migratory requirements of fishes in the catchments and the cost-benefit of mitigating river fragmentation to achieve a sustainable balance between the use and protection of resources in the catchment. Finally, the study has identified water quality and flow stressors that are negatively affecting the wellbeing of the fish communities in the catchment. The water quality stressors derived from land-based activities and associated management of flows in the catchment must be improved to attain a sustainable balance between the use and protection of the resources of the uMngeni Catchment.
The effects of Chromolaena odorata on tree growth dynamics at Buffelsdraai Landfill site.
(2019) Ramaano, Rerani.; Tsvuura, Zivanai.; Moyo, Hloniphani Peter Mthunzi.
Ecological restoration is a process which assists the recovery of an ecosystem which was previously disturbed or degraded. Through continuous disturbances, invasive alien plants (IAPs) are able to successfully spread and establish themselves while reducing the diversity and the abundance of native plants. The IAPs invade both human and non-human modified landscapes thus causing huge threats to biodiversity conservation and ecosystem services provision. The invasion of alien plants at Buffelsdraai Landfill Site Community Reforestation Programme is a major threat to reforestation success. Buffelsdraai is under rehabilitation through a community reforestation programme that focuses on active involvement of nearby communities in propagating seedlings and planting them on site. The study was conducted in a former sugarcane field which has been planted with diverse native tree species, but invaded by dense stands of Chromolaena odorata. This study aimed to 1) determine the influence of a woody shrub C. odorata on the growth dynamics of replanted native trees at the Buffelsdraai Landfill Site, and 2) to assess the efficacy of cutting height and frequency in mechanical control of C. odorata. Over a period of 12 months, the growth responses of three native tree species (i.e., Vachellia natalitia, Brachylaena discolor and Erythrina lysistemon) were investigated by measuring stem length and diameter, trunk basal diameter, tree height and canopy diameter, under four treatments. The treatments consisted of: (i) a control, where no clearing of C. odorata or grasses was undertaken beneath the canopy of trees; (ii) clearing of C. odorata from underneath trees; (iii) clearing of grass from underneath trees; and (iv) clearing of both grass and C. odorata from trees. Measurements were undertaken on 264 trees, 88 individual trees per species, 22 individuals per species per treatment at the beginning and the end of the study. Stem, trunk and canopy length, diameter, and tree height growth data within each tree species were analysed using generalized linear models. Tree height growth comparisons among the tree species was analyzed using a non-parametric Kruskal-Wallis test since the data did not meet the assumptions of a One-way ANOVA. There were no significant differences between all four treatments across the tree species (P > 0.05). However, E. lysistemon growing where there was grass removal had significantly higher (P = 0.033) trunk basal diameter growth, than other treatments. Results from this study showed that the removal of C. odorata at the Buffelsdraai community project had no impact on the trees due to short time period of the study. Overtime we expect that tree performamce would increase with less C. odorata competition. Trees performed equally well in the presence and absence of grass and C. odorata. Young tree saplings of pioneer species were used for this study which could be a possible influence of these results. To investigate the impact of C. odorata mechanical control, 28 plots (5 m × 5 m) were established, at least 2 m apart, with one designated as the control with no cutting of the plants. The two treatment combinations were between cutting frequencies which had: (1) cutting frequency made up of single, twice and thrice cutting; and (2) stem cutting height which had 30, 100 and 200 mm cutting heights aboveground. I used 420 C. odorata plants (i.e. 3 cutting heights × 9 replicate plots × 15 plants + 15 control plants). Plants were first cut in November 2016, the coppice regrowth was cut on plants in 18 plots in February 2017, and a third cut was made on plants in the last nine plots in May 2017. Stump basal diameter, the number, length and diameter of resprouting shoots were measured at 3-month intervals. Mean number of resprouting shoots, mean shoot length and diameter of the resprouts, mean shoot length:diameter ratio (shoot taper function) of resprouts, shoot production (shoots mm-1) and mean total shoot basal area:stump basal area ratio for all treatment combinations were analysed using the Friedman’s test. The relationship between cut stem diameter and the number of resprouting shoots, resprouting shoot length, and resprouting shoot diameter were explored using correlation analysis. There was a significant difference in the number of resprouts produced across all treatment combinations (P < 0.001). The 30 mm cutting height produced the least number of resprouts with increasing cutting cycles compared to the 100 and 200 mm cutting height. Shoot length and diameter decreased with cutting frequency, with smaller shoots produced with continued cutting cycle. There were significant difference in the shoot length and diameter of shoots produced in the 30 mm cutting height in the last cutting cycle and those that were produced on 200 mm cutting height. Shoot taper function and shoot production showed significance (P < 0.001), with smaller number of shoots produced in the 30 mm cutting height over the cutting frequencies (P < 0.001). Total shoot basal area:stump basal area ratio did not differ significantly across the cutting heights and the cutting frequencies. There was a strong positive relationship (r = 0.91; P < 0.001) between the number of resprouts and stem diameter across all repeatedly cut stems in all cutting heights and the number of resprouts produced in each cutting height decreased over each cutting frequency. Repeated cutting of C. odorata at a lower cutting height of 30 mm may deplete its energy reserves, reducing the number of resprouts produced, thereby leading to death of the plants. Repeated cuttings at short-term intervals also prevents the plants from growing to reproductive maturity and seed production, leading to no seed dispersal to increase infestations
The breeding system and demography of the Transvaal Sesame-bush, Sesamothamnus lugardii (Pedaliaceae)
(2019) Bijl, Alison.; Johnson, Steven Dene.; Midgley, Jeremy J.
The aim of this research was to assess the breeding system, pollination relationship and demography of the Transvaal Sesame-bush, Sesamothamnus lugardii N. E. Br. Ex Stapf. (Pedaliaceae). S. lugardii is an arid savanna succulent shrub which can be found throughout Zimbabwe, southern Botswana and in northern South Africa, where it is anecdotally thought to be rare. Two populations of S. lugardii were assessed in Limpopo, South Africa. The floral traits of S. lugardii suggest that it is specialised for pollination by long-tongued hawkmoths. The flowers bloom in the evening, are large, sweetly scented and pale in colour. The corolla tubes are very long (ca. 10 cm) and narrow. Very long-tongued hawkmoths (Agrius convolvuli) were found to be the only visitors capable of accessing the nectar at the base of the S. lugardii corolla tubes while foraging and simultaneously interacting with the reproductive structures, successfully pollinating the flowers. S. lugardii is an obligate outcrosser, dependent on A. convolvuli hawkmoths for sexual reproduction. The high-risk traits of the S. lugardii breeding system, namely pollinator specialisation and obligate out-crossing, could render S. lugardii vulnerable to extinction. Predation of flowers by scarab beetles in the study population at Mapungubwe National Park resulted in low fruit set. At Morongwa Private Safari Lodge florivory was negligible and fruit set was higher. In both study populations, S lugardii was dominant in patches across the landscape, but only a small proportion of the numerous plants observed were seedlings. Little is known about the population dynamics of S. lugardii, but the absence of seedlings suggests a potentially vulnerable demography. The large shrubs were heavily impacted by meso- and mega-herbivores, but are resilient to herbivory, as they are capable of bark recovery and epicormic resprouting. However, the ever-increasing numbers of large herbivores at Mapungubwe could reach a critical threshold beyond which the populations of S. lugardii lose their resilience, putting them at risk of local extirpation. The number of seedlings in the populations at Mapungubwe decreased between an initial study conducted in 2005 and the recent assessment in 2014. This may be due to sporadic recruitment, but could also indicate a demographic bottleneck limiting seedling establishment. The low-risk traits associated with demography, namely resilience through longevity and vigorous resprouting, offset the high-risk traits by buffering the populations from decline during periods of reproductive failure. The environment in the study populations at present favours the continued survival of S. lugardii, despite the slow population turnover and low rate of reproductive success. Should the environmental conditions become less favourable for S. lugardii, then the extinction risk could greatly increase over a short period of time, and could even result in local extirpation.
Snake population declines and conservation: a global synthesis, and perspectives from southern Africa, based on long-term field observations.
(2018) Schmidt, Warren Robert.; Downs, Colleen Thelma.
Amphibian and reptile declines have been documented from across the globe in recent decades. This is a result of anthropogenically driven effects including transformation of the landscape, habitat destruction, environmental degradation, road mortality, leaching of chemicals and pollutants into the environment, genetic isolation and disease. More recently, several well-studied declines affecting snakes have been documented in the literature. Most studies emanate from North America and Europe, with a small percentage from Australia. Due to the absence of long-term site monitoring in Africa, the extent of snake population declines is mostly unknown and at best, speculative. My study aimed to provide baseline data on snakes from South Africa based on long-term field observation and accumulative data spanning a period of approximately 30 years, from 1988 – 2018. In my experience, I have noted perceived declines in several geographical regions, including species-specific declines. Whilst the primary focus of this study was on snakes, these declines extend to other amphibian and reptile species, and brief reference is made to these in the specific site studies. Firstly, in Chapter 1, I reviewed the published literature globally pertaining to snake conservation, population ecology and documented snake population declines and the contributing factors thereof. The causes of decline are complex and often interlinked, having a cascading effect. For example, a population of snakes isolated by roads and urban development will become genetically isolated, leading to weakened immunity and increased stresses, making them susceptible to disease and overloaded parasite burdens. Therefore, a population experiencing declines is affected by several interlinking causes. All contributing factors must be carefully analysed to initiate mitigation measures to prevent further decline. Secondly, in Chapter 2, I reviewed our current understanding of global snake diversity, conservation and systematics to quantify species diversity and conservation trends in extant snake species. We are far from understanding true snake species diversity with numerous new species being described by science annually. Systematics and taxonomy, including phylogenetic relatedness, are all crucial aspects required to facilitate and implement effective conservation measures if we are to conserve world snake diversity. Thirdly, in Chapter 3, I have presented snake data pertaining to road mortality based on a study undertaken along the R516 national road in Limpopo Province, South Africa. Road mortality has been identified as a contributing factor of snake population declines in many regions of the globe. The increasing network of roads and associated vehicular traffic is cause for concern, not only in protecting snakes, but other faunal species as well. In Chapters 4 and 5, I examined data from personal archived records taken at two different, well-defined, field study sites – one site situated in a former grassland habitat in Gauteng Province, which is now completely transformed, and a second site on the lower South Coast of KwaZulu-Natal Province, which has experienced relatively lower rates of anthropogenic habitat transformation. Both sites have been randomly surveyed for a period spanning approximately 30 years and may represent two of the longest-running site specific herpetological surveys undertaken in southern Africa. The impact of anthropogenic habitat transformation through ecological succession and urban development on species populations and diversity is discussed in detail. In the absence of consistent, methodologically robust surveys using trap arrays and mark-recapture studies, which are absent in South Africa, long-term field observation may be the only available option in identifying possible snake declines. This sentiment is echoed elsewhere across the globe where numerous seasoned herpetologists have indicated that snakes have declined in their respective field sites in recent decades. My data support this. In Chapter 6, I selected a common, widely distributed snake species, the rinkhals (Hemachatus haemachatus), as a species-specific candidate. These elapid snakes appear to have experienced dramatic declines in some parts of their range, i.e. the Western Cape and eastern Zimbabwe, but which are still thriving within a peri-urban environment on the eastern highveld in Gauteng. Factors contributing to its success or decline are discussed. In conclusion, our current lack of long-term monitoring is highlighted, as well as challenges and possible solutions and methods to gain better insight and understanding of snake population declines regionally and globally. The pros and cons of utilizing citizen science, virtual museums and social media data sets is discussed within the context of providing skewed data that may mask underlying population trends, providing a biased output which may in turn affect accurate conservation assessments. This thesis aims to be a qualitative study rather than a quantitative analysis. However, various population and ecological models are being researched for further statistical testing.

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