Theses and Dissertations (Zoology and Entomology)

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Metabolic heat generation in larval masses of the black soldier fly, Hermetia illucens L. (Diptera: Stratiomyidae), at different stocking rates
(University of Pretoria, 2025-02) Weldon, Christopher W.; masombukajt@gmail.com; Masombuka, Thulani Jack
The increasing global population, expected to surpass nine billion by the mid-21st century, necessitates innovative solutions for sustainable food and feed production. Insect larvae, specifically of the black soldier fly (Hermetia illucens), offer a promising alternative through bioconversion technology, wherein insects convert organic waste into valuable products like protein-rich animal feed, human food, and by-products such as frass and chitin. This study investigates the impact of stocking rate and temperature on the heat accumulation, development and growth and performance of black soldier fly larvae fed on pre-consumer fruit and vegetable waste. Larvae were reared at four stocking rates (0.5, 1, 1.5, and 2 g diet per larva) and incubated at three temperatures (27.5°C, 30°C, and 32.5°C). Results showed that increasing stocking rate led to heat accumulation in larval aggregations, which affected larval development. While survival rates were highest at 32.5°C with 0.5 g/larva (44.95%), weight gain was greatest at 30°C. Larval length was highest at 27.5°C. Bioconversion efficiency peaked at 45% with a stocking rate of 0.5 g/larva. Waste reduction efficiency remained consistently high across treatments, demonstrating the adaptability of H. illucens larvae for bioconversion in varied conditions. This research highlights the potential of black soldier fly larvae as a sustainable method for waste management and resource conversion, supporting both food and feed production.
Assessing occupancy of mammals in the Waterberg Mountain Catchment area across spatial scales
(University of Pretoria, 2024-11-19) Keith, Mark; Marshal, Jason P.; u22881027@tuks.ac.za; Naleba, Rodney
The on-going global decline of large mammals mainly due to anthropogenic activities, necessitates enhanced management and conservation efforts. Hence, there is a considerable need for monitoring ecological estimates such as mammal occupancy and distribution in space and time. Monitoring the impact of factors responsible for mammal occupancy and distribution is equally important. Additionally, the scale at which such investigations are carried out is also key to ensure reliable outcomes for informed decision making in the management and conservation of mammals. The Waterberg Mountain catchment (WMC) is situated in the Limpopo province of South Africa. This a very biodiverse area, however, few comprehensive studies on the biological diversity and associated aspects from this area have been carried out. This area consists of several small, fenced wildlife properties. As such, the main activity in the area is eco-tourism (wildlife-based) for economic purposes as well as contributing to conservation. The small, fenced, and the isolated nature of the wildlife properties in the WMC necessitates a considerable level of human intervention in the management of mammals and their environments. I used camera trap data collected between December 2021 and April 2024 from the WMC from several wildlife properties. I analysed the data using multi-species Bayesian occupancy models, modelling mammal occurrence as a function of several site-level covariates, including distance to nearest permanent water sources, distance to roads, normalized difference vegetation index (NDVI), elevation, among others to investigate the key drivers of mammal occupancy in the WMC. Furthermore, I measured site-level covariates at multiple spatial scales to examine if variation exists in mammal occurrence patterns across scales. I also sought to compare occupancy patterns observed between managed (fenced and managed) and non-managed mammal species (free ranging with the ability to cross through fences between properties). The results generally showed that anthropogenic variables were more impactful than environmental variables in driving mammal occupancy. Moreover, deriving covariates at multiple spatial scales had an impact on the mammal occurrence patterns observed. Also, differences between mammal occupancy responses were observed between managed and non-managed mammal species. These general observations were made even though most of the results were not statistically significant (using 95% confidence intervals). These findings highlight the importance of anthropogenic infrastructures including roads, buildings, and fences on mammal occurrence and space use patterns within small, fenced wildlife properties. In addition, the results suggest that scale should always be considered when designing species-environment relationship studies. Finally, the results highlight the importance of the environmental context (small, fenced wildlife properties) on mammals’ occurrence patterns and distribution, which in turn influences mammal ecology.
Impacts of maize cropping systems on soil microbiome phytochemistry and trophic interactions between the fall armyworm, Spodoptera frugiperda (J. E. Smith) and its endoparasitoid Cotesia icipe (Fernandez-Triana & Fiaboe)
(University of Pretoria, 2025-02-14) Yusuf, Abdullahi Ahmed; Mutyambai, Daniel Munyao; Khamis, Fathiya Mbarak; AJALLOH@ICIPE.ORG; Jalloh, Abdul A.
Intensification of staple crop production with synthetic chemical inputs has contributed to negative environmental impacts. Ecological intensification, using diverse maize-cropping systems, has the potential to reverse these detrimental effects and sustainably improve crop productivity. However, the influence of these diverse maize-cropping systems on soil physicochemical properties, the soil and maize-root microbiome, and subsequent plant-insect interactions has not been clearly understood. Diversified maize-cropping systems, such as push-pull cropping systems and maize edible-legume intercropping (MLI) systems, are known to enhance plant defence mechanisms, reducing susceptibility to invasive pests like the fall armyworm (FAW, Spodoptera frugiperda J. E. Smith). This polyphagous pest, originating from the Americas, has become a global concern with its invasion into Africa and subsequent spread worldwide, targeting over 353 host plant species, primarily maize and sorghum, staple crops for most African communities. Despite the widespread damage caused by S. frugiperda, limited research has focused on understanding the influence and mechanisms of diverse maize-cropping systems soil legacy on inducing resistance to pests. Therefore, the goal of this study was to determine the effects of different types of maize-cropping systems (push-pull, MLI, and maize-monoculture) on soil health (the soil's physical and chemical properties), the microbiome (the rhizospheric soil, and the bacterial and fungal communities that live in the roots of the maize plants), and the plant's resistance to damage by the S. frugiperda. This encompassed both direct effects, such as reduced S. frugiperda neonate feeding and larval development, and indirect effects, such as the attraction of the S. frugiperda endoparasitoid, Cotesia icipe (Fernandez-Triana & Fiaboe). Chapter one of this thesis briefly introduces S. frugiperda and emphasises the significance of soil physicochemical properties and the microbiome in diversified maize-cropping systems. It discusses the importance of studying tritrophic interactions in maize-cropping systems, investigated the influence of soil microbiomes on plant-insect interactions, and examined the role of the endoparasitoid, C. icipe in pest management. The chapter also reviews available control methods, suitable farming practices for enhancing soil and plant health, and effective pest management strategies. Finally, it outlines the rationale and objectives of the study. Chapter two outlines the field sampling procedures used on long-term push-pull cropping system farms. The soil physicochemical properties and microbiomes were analyzed using the Bouyoucos hydrometer method and the MiSeq Illumina sequencing platform. The goal was to understand the impact of long-term push-pull cropping systems on the physicochemical properties of soil, rhizospheric, soil and maize-root microbiomes. Soil from push-pull cropping systems had higher levels of pH, electrical conductivity, nitrogen, organic carbon, potassium, phosphorus, calcium, magnesium, and exchangeable acidity, among other parameters, compared to soil from conventional maize-monoculture cropping systems. The study compares the microbiomes relative abundance, diversity, and functional protein pathways with conventional maize-monoculture cropping systems. This chapter emphasizes the less-known belowground interactions within the push-pull, revealing its significance in harboring ecologically important microbial groups that improve soil fertility, decomposition, nutrient cycling, and plant protection compared to maize-monoculture cropping systems. Chapter three examines the impact of crop mixtures, particularly MLI systems, on belowground microbial communities and soil physicochemical properties in maize-cropping systems. By comparing the maize-monoculture cropping system with four different MLI systems, it shows that crop mixtures have a big effect on the rhizospheric soil and the microbial community restructuring around maize-roots. They also facilitate the growth of beneficial fungal and bacterial populations, significantly contributing to agrobiodiversity and belowground ecological services. Chapter four presents the findings on the impact of MLI in comparison with conventional maize-monoculture cropping systems, on soil legacies, maize growth, and the direct resistance of maize plants to S. frugiperda. The chapter includes details on field sampling and soil physicochemical properties, maize plant growth parameters evaluation, and S. frugiperda neonate feeding and larval development. The findings of this study reveals that soil-conditioned by MLI systems enhances nutrient levels and maize growth while reducing S. frugiperda neonates feeding and larval development. Hence, this chapter underscores the positive influence of soil-conditioned by MLI systems on maize plant growth, soil health, and S. frugiperda management. Chapter five discusses how long-term push-pull cropping systems alter the soil and affect plant-soil feedback. It focuses on maize phytochemical profiles, volatile-mediated interactions in plant-insect relationships, and plant growth parameters. The study scrutinizes the behavioural reactions of the S. frugiperda endoparasitoid, C. icipe, to the alterations in volatile profiles resulting from push-pull soil-conditioning, in contrast to conventional maize-monoculture cropping systems. Maize plants grown in soil-conditioned by push-pull had higher soil physicochemical properties, plant biomass, and growth rate. Consequently, S. frugiperda neonates fed less on leaf tissues from soil-conditioned by push-pull in comparison to maize grown in soil-conditioned by maize-monoculture cropping systems. In quantitative and qualitative terms, diverse volatiles were observed in maize plants grown in soil-conditioned by push-pull cropping systems compared to maize-monoculture cropping systems. The volatiles emitted by maize plants grown in soil-conditioned by push-pull cropping systems were significantly more attractive to C. icipe than those emitted by maize plants grown in maize-monoculture cropping systems. Chapter six discusses and concludes the thesis, provides a summary of the study's key findings, explores practical applications of the findings, and offered recommendations for future research endeavors.
Malaria vector composition and insecticide resistance in Vhembe district, a high disease burden region of South Africa
(University of Pretoria, 2025-02) Riddin, Megan A.; Bastos, Armanda D.S.; u21847585@tuks.co.za; Kachali, Kondwani
South Africa’s malaria endemic provinces (Limpopo, Mpumalanga & KwaZulu-Natal) continue to face residual malaria transmission that is partly attributed to outdoor biting and resting Anopheles species. This reduces effectiveness of control interventions as they mostly target indoor vector species. Limpopo Province remains the most affected region in the country, carrying the highest disease burden, particularly in the north-eastern Vhembe district. However, the factors sustaining residual transmission in the area remain unknown. Vectors responsible for transmitting malaria and other potential secondary species have been reported in the area, but in low numbers, as has the presence of species implicated in malaria transmission in other African countries. The role of vectors and other factors, including insecticide resistance, in the persistence of residual malaria remain to be determined. Therefore, this study investigated species composition, feeding preference and insecticide resistant status in mosquitoes from Vhembe, towards understanding the cause of the persistent and residual malaria. Anopheles mosquitoes were collected in Bende Mutale, Tshivaloni, and Gwakwani, some of the areas in the Vhembe district, Limpopo Province, with the highest malaria burden. Mosquitoes were collected using carbon dioxide- and animal-baited traps, dippers and sweep nets over four collection events during the 2022-2023 and 2023-2024 malaria season. Species were morphologically identified to species level, with those belonging to the An. gambiae complex and Anopheles funestus group being identified by species-specific polymerase chain reaction (PCR). For those specimens that could not be identified morphologically, amplification and sequencing of the cytochrome oxidase subunit 1 (COI) barcoding region was performed. Insecticide susceptibility testing was carried out on Anopheles mosquitoes using standard WHO tube bioassays, testing against DDT, deltamethrin, bendiocarb and malathion. PCR and sequencing were used to investigate knockdown resistance (kdr) mutations using a typing approach. Finally, host preference was investigated through bloodmeal analysis on wild-caught blood fed females using PCR and sequencing of the cytochrome b (cyt b) gene. A total of 6,134 Anopheles specimens were collected of which 4,772 were used for insecticide susceptibility testing. Species composition assessment (Chapter 2) revealed that Anopheles gambiae s.l. (n=2,160) comprised of three sibling species in Vhembe: An. arabiensis, An. merus and An. quadriannulatus. The 357 An. funestus s.l. collected consisted of An. rivulorum-like, An. rivulorum, An. leesoni and An. vaneedeni. Other species collected included An. coustani, An. rufipes, An. pretoriensis, An. listeri, An. nili and An. gibbinsi. Nine Anopheles spp could not be assigned to species based on COI sequencing. Insecticide susceptibility testing (Chapter 3) detected potential resistance to bendiocarb and deltamethrin in An. quadriannulatus and An. rivulorum, respectively. Resistance to DDT, deltamethrin and bendiocarb was detected in An. coustani, An. rufipes, and An. pretoriensis. Full insecticide susceptibility to all insecticides was reported in An. arabiensis, An. merus, An. vaneedeni, An. rivulorum-like and An. leesoni. The sodium channel mutation associated with kdr resistance was not detected in any of the An. gambiae s.l. specimens tested. Host-specificity assessed through bloodmeal analyses (Chapter 4) revealed that An. quadriannulatus and An. pretoriensis favoured cattle and goats. Comparative analysis of two cyt b assays confirmed that both amplify mosquito vector DNA in the absence of bloodmeal DNA of adequate integrity. The results of this study support continued entomological monitoring to further investigate the roles of these species in malaria transmission and to monitor insecticide resistance in these populations. Successful implementation of targeted interventions relies on research evidence to effectively reduce vector and malaria burden.
Seasonal small mammal diversity, endocrine correlates, and diet behaviour in rodents across transformed and pristine ecosystems in the Magaliesberg
(University of Pretoria, 2025-02) Ganswindt, Andre; Somers, Michael J.; jawi.ramahlo@up.ac.za; Ramahlo, Mmatsawela
Landscape transformations due to a growing human population lead to increased resource use, declines in natural habitat quality and increased human-wildlife conflicts across ecosystems. As a result, animal population dynamics, stress-related behaviour, and diet may be affected in unknown ways. Rodents can be ideal model species for monitoring ecosystem health. Their relatively small size allows them to use various niches that are inaccessible to larger animals. By investigating the effects of anthropogenic activities and changes in global climate on rodent species, we can assess the impacts these variables will have on wildlife over time. We can also determine the effects of these variables on species abundance, diversity, stress-related endocrine correlates, and diet preference at inter- and intra-specific levels. This study investigated the effects of anthropogenic activity and human-mediated land transformation on capture/recapture frequencies, species richness, and diversity of native small mammal community assemblages in the Magaliesberg Biosphere, North West province, South Africa. Additionally, the study aimed to establish minimally invasive methods for quantifying faecal glucocorticoid metabolites (fGCMs) in six southern African rodent species (Aethomys ineptus, Lemniscomys rosalia, Mastomys coucha, Micaelamys namaquensis, Otomys irroratus, and Steatomys pratensis) by evaluating five enzyme immunoassays (EIAs). Following this, the adrenocortical responses of dominant rodent indicator species to human-mediated practices and seasonal variation were monitored to determine their efficacy in informing on ecosystem health. Methods of keratinaceous (hair and nails) tissue sample collection and preparation methods for rodent diet stable isotope analysis (SIA) were also investigated. The least minimally invasive method was used to assess the diet preferences of two dominant rodent species across differently disturbed landscapes. Five anthropogenically transformed land-use types were investigated: animal rehabilitation and ecotourism centre, agricultural farmstead, residential farmstead, mine-adjacent agricultural farmstead, and nature conservancy. Over three consecutive years, live traps were used to sample rodents during the dry and wet seasons. For validation of fGCM quantification methods, faecal samples were collected daily from enclosures of captive females and males and frozen immediately at -20°C. Biological and physiological stimuli were used, and fGCM concentrations were determined from samples collected before, during, and after each event. Following this, a suitable assay was found to assess the adrenocortical hormone responses of two dominant southern African murids, Lemniscomys rosalia and Mastomys coucha. Faecal samples were collected from traps of captured individuals and measured for fGCM concentrations using the previously validated assay. For diet analysis, hair and nail samples were prepared for SIA mass spectrometry, and carbon and nitrogen isotope ratios were compared. My study found that capture/recapture frequencies differed significantly between sites and seasons, with the highest capture frequencies recorded at the agricultural and residential farmsteads. Species richness and diversity were highest at the residential and industrial-agricultural farmsteads, both of which experienced intermediate levels of anthropogenic disturbance throughout the sampling period. For quantifying fGCMs in rodents, my study identified the 5α-pregnane-3β,11β,21-triol-20-one EIA (detecting fGCMs with a 5α-3β, 11β-diol structure) as most suited in all six species assessed. Using this EIA, it was found that fGCM concentrations of M. coucha were significantly higher in the wet season compared to the dry. Land-use variation had no significant impact on either species, which supports reported synanthropic behaviour (to various extents) in both species. The reduced adrenocortical responses observed in these dominant species in human-transformed areas suggest that when monitoring fGCM concentrations, dominant species such as M. coucha and L. rosalia are not always an ideal indicator of anthropogenic disturbance. Diet-related sampling methods were compared, and hair sample collection was found to be faster and more animal-friendly, resulting in a calmer demeanour and reduced anxious behaviour in animals compared to the effects of nail sample collection. Correlation analyses of hair and nails showed high similarity in δ13C and δ15N isotope ratios within four of the six species analysed. Hair clipping may be classified as the less invasive sampling method and can be used exclusively on rodents, as isotopic variation between hair and toenail samples is negligible. Overall, the findings of the study lend support to the use of minimally invasive methods of data collection and a combination of both dominant and low-population rodent species as biological indicators of ecosystem health to ensure repeatable, long-term data collection and capturing of ecological responses from both generalist and specialist species to elucidate the impacts of anthropogenic activities on wildlife populations and their natural environments.
The mechanisms of socially induced infertility of the highveld mole-rat (Cryptomys hottentotus pretoriae)
(University of Pretoria, 2024-11) Bennett, Nigel Charles; Hart, Daniel William; Oosthuizen, Carel ; u18112537@tuks.co.za; De Wet-Marais, Christiaan
This thesis explores the intricate mechanisms underlying reproductive suppression and queen succession in the highveld mole-rat (Cryptomys hottentotus pretoriae), a cooperatively breeding social rodent within the family Bathyergidae. In these colonies, a dominant breeding female (the queen) exclusively monopolises reproduction, while subordinate members of both sexes are hysiologically suppressed through a complex interplay of social, hormonal, and ecological factors. Central to this hierarchy and suppression is prolactin (PRL), a key hormone in mammalian reproduction that regulates energy allocation and social behaviours, enforcing infertility among non breeding females (NBFs) and ensuring colony stability. Field and laboratory experiments revealed that PRL levels are modulated by ecological and seasonal influences. During the dry season, elevated PRL levels maintain reproductive suppression, possibly through restricted feeding of subordinates by dominant breeders. In contrast, the wet season, marked by increased food availability, triggers a reduction in PRL levels, enabling partial reproductive activation in NBFs and facilitating dispersal opportunities. Experiments involving forced dispersal and sucrose supplementation demonstrated a direct link between decreased PRL levels, improved energy balance, and reproductive activation. However, the dopamine agonist bromocriptine, typically effective in lowering PRL, failed to do so in highveld mole-rats, suggesting an evolutionary resistance to dopaminergic regulation in the dopamine-prolactin (DA-PRL) axis. The findings underscore the centrality of PRL in maintaining socially induced infertility, shaped by energy dynamics and environmental conditions. This strategy is critical for reproductive suppression in cooperative breeders, balancing ecological pressures, genetic risks, and social stability. Among highveld mole-rats, PRL mediated suppression not only sustains the reproductive hierarchy, but also facilitates colony cohesion. Within intact colonies, PRL levels varied significantly among NBFs, with heavier females—potential "beta queens"—exhibiting lower PRL levels and partial reproductive activation. Upon queen removal, females with the lowest PRL levels were most likely to succeed to new queen status (regardless of their relatedness to the breeding male), supported by elevated testosterone levels that enabled the aggression necessary to dominate rivals. Once the new queen was established, her testosterone levels subsided, reducing prolonged aggression, and stabilising the colony. This chapter also found a minimal influence of genetic relatedness on queen succession, emphasising hormonal regulation over incest avoidance. Yet, despite their tolerance for inbreeding, highveld mole-rats showed a preference for unrelated males when available, highlighting a secondary role for genetic diversity in mate selection. The thesis demonstrates how PRL-mediated physiological suppression underpins reproductive hierarchies, illustrating the delicate balance between ecological, hormonal, and social factors that shape reproductive strategies in inbreeding-tolerant species. In conclusion, this work provides valuable insights into the evolutionary adaptations and hormonal mechanisms that maintain reproductive hierarchies in cooperative breeders. The findings have significant implications for understanding how environmental and social factors influence reproductive dynamics, contributing to a broader knowledge of behavioural ecology and the evolution of sociality in mammals.
Bat diversity in the Waterberg mountain catchment, Limpopo province South Africa : patterns and drivers
(University of Pretoria, 2025-02) Keith, Mark; Somers, Michael J.; Parker, Daniel Matthew; tracy.basch@tuks.co.za; Basch, Tracy
The Waterberg Mountain Catchment (WMC) in Limpopo, South Africa, is an important region due to its diverse environments. A large area of the WMC was designated as a United Nations Educational, Scientific and Cultural Organization (UNESCO) Biosphere Reserve in 2001. The WMC spans approximately 650000 hectares and includes a variety of vegetation types and geological formations. There have been shifts in land-use within the WMC, with a recent rise in wildlife-based activities, such as eco-tourism, hunting, and wildlife production. While tourism is often seen as beneficial for biodiversity conservation, it can sometimes lead to decreased diversity due to habitat loss from infrastructure development and the introduction of non-native species. Agriculture, including crop production and livestock farming, is a significant influence in the region, affecting local wildlife by reducing potential habitat and resources, which can lead to increased interspecific competition. The adverse effects of land-use changes impact volant and non-volant mammals differently, as the sustained flight capabilities of volant species enable them to overcome barriers between areas with enough resources to sustain them. Bats are categorised into foraging guilds based on their morphology and behavioural traits. These guilds include open-space foragers, edge-space foragers, and clutter-space foragers, each adapted to different environmental conditions. By using these foraging guilds and species richness, I analysed how different land-use types, and other factors of environmental and anthropogenic drivers in the WMC potentially influenced bat diversity and assemblages in the Waterberg. I further investigated how the various factors might affect bat diversity and relative call activity in the WMC to different extents. By analysing bat assemblages in relation to these factors at various scales (30 m, one km and five km), I aimed to provide insights into how these measures at the scales could influence/affect richness and relative call activity. My key question was what species of bat are present in the WMC and what drivers (anthropogenic or natural) might have influenced the presence or absence of various species and the abundances of those species present. I collected data by active capture and release sampling to manually identify bat species with the use of mist nets, harp traps, and by passively recording bat call data using audio recorders. I analysed my processed call data to determine species richness and relative call activity (using Miller’s Index). Generalised linear mixed models were run using variables measured from satellite imagery and QGIS to determine what drivers influenced distribution. I found that bat species richness was relatively homogeneous across the WMC. I recorded 23 bat species, consistent with historical records of 27 species for the region. I recorded two species, Nycticeinops schlieffenii and Neoromicia anchietae, that had not previously been recorded in the area. My results showed that the foraging guilds that contributed the most to species richness were the open-space and edge-space foraging guilds. Aside from foraging guilds, I also grouped species into adapter and avoider species based on roosting habits and how well the species survive in disturbed environments. The relative call activity of adapter species (mainly free-tailed and vesper bats), compared to avoider species (such as horseshoe bats), was higher due to increased anthropogenic disturbances (such as cleared vegetation for buildings, roads, etc.). Cleared vegetation for buildings and roads etc. would result in reduced roosting sites for Rhinolophus species and other clutter-space guild species. Despite similar species richness across properties, species’ relative call activity varied, with edge-space foraging guilds notably predominant. This guild seemed to benefit from low-intensity agriculture, livestock farms, and areas with cleared vegetation. Clutter-space foragers, which are less adaptable and more sensitive to habitat fragmentation, were notably scarce throughout the WMC. Habitat heterogeneity supports species richness by offering diverse resources and roosting sites, but excessive heterogeneity can negatively impact specialized species like clutter-space foragers. While heterogeneity alone does not affect species richness, the availability of space and the degree of fragmentation do. Clutter-space foragers also had lower detection rates due to their higher frequency calls and limited roosting options in southern Africa, leading to increased interspecies competition. Clutter-space forager relative call activity was influenced by the presence of roosting sites and denser vegetation. The generalised linear mixed model results indicated that bat species richness declined with increased normalised difference vegetation index (NDVI) and vegetation complexity, while relative call activity increased with decreased clutter and distance to clutter. Despite the influence of land-use and water availability on bat populations in other studies, I did not detect an influence of these factors on species richness in my study. Small-scale, low-intensity agricultural lands were less impactful than anticipated, possibly due to seasonal activity and water sources being less limiting. Water sources in the Waterberg are more abundant, thus potentially not being limiting as it may have been in other studies. Some studies also show that agricultural properties surrounded by natural vegetation support bat richness and activity. Aside from seasonal influences, my study didn’t include insect abundance (thus food availability) which may have also influenced the results. Elevation and vegetation types were significant at the five km scale, with higher elevations and dense vegetation reducing bat relative call activity and richness. The study concluded that bat richness and relative call activity are influenced by a combination of elevation, NDVI, and distance to clutter, with broader scales (five km) providing clearer insights into distribution patterns. These factors combined would indicate that change in vegetation cover along an elevational gradient could be a driver of diversity. Thus, land-owners and property management should prioritise the maintenance of cluttered habitats to support avoider species, particularly clutter-space foragers. Research into roosting preferences and specific management of vegetation cover could increase prey relative call activity and foraging opportunities for these species. Establishing buffer zones and ecological corridors to reduce habitat fragmentation and maintaining diverse vegetation structures will help support both adapter and avoider species, contributing to the long-term survival of bat populations in the WMC and similar environments.
A risk assessment of anthropogenic activities on cetaceans in South Africa in light of the expanding oceans economy
(University of Pretoria, 2024-09) Vermeulen, Els; Purdon, Jean; u18011536@tuks.co.za; Grobler, Alannah
The unique oceanographic characteristics of the South African marine environment gives rise to high biological productivity and a wide variety of habitat types. These in turn are able to support a high diversity of marine life, including a variety of cetacean species. In addition to this, the South African marine environment provides biotic and abiotic resources which can be utilised by humans. In an effort to boost the South African economy by expanding the utilisation of its marine environment, Oceans Phakisa was launched in 2014. In light of this expansion, the interaction between marine life and the anthropogenic activities utilising ocean resources must be investigated, and potential risks must be determined. Consequently, a risk assessment of anthropogenic activities on cetaceans in the South African Exclusive Economic Zone (EEZ) was developed. In first instance, the impact of anthropogenic activities on cetacean mortalities was determined. This was done through an analysis of cetacean mortality data collated between 1969 and 2023. Most cetacean mortality records (62%) were not assigned a cause of death. However, at least 38% of cetacean mortalities were associated with an anthropogenic activity. Entanglements in bather protection nets were most frequently identified as the cause of mortalities, followed by bycatch, ship strikes, and entanglement in fishing gear. Midwater trawls were most frequently involved in bycatch incidents, while octopus and rock lobster trap fisheries were most frequently involved in fatal entanglements in fishing gear. Indo-Pacific bottlenose dolphins, Bryde’s whales, humpback whales, and dusky dolphins were frequently identified in anthropogenic related mortalities. Spatial analysis of the mortality data identified the west and south coast of South Africa as hotspots of cetacean mortalities, especially during summer months (October to March). Secondly, the risk that marine anthropogenic activities may pose to cetacean species was assessed. This was done by conducting a spatiotemporal analysis of the distribution overlap of 18 cetacean species and the spatial footprint of 9anthropogenic activities in the South African EEZ. Results indicated that all modelled cetacean distributions in the South African EEZ overlapped with at least one anthropogenic activity. Shipping activity overlapped with all cetacean distributions and may therefore pose the highest overall risk based on spatial overlap. Risso’s dolphins, minke whales, sperm whales and common dolphins were identified as the species with distributions that have a higher than 80% overlap with shipping activity. Results indicated that most cetaceans in the South African EEZ may be at risk from the effects associated with cumulative anthropogenic pressures. The west and south coasts of South Africa were identified as areas were risk to cetacean species from the effects of anthropogenic activities was highest. The results of this thesis provide a baseline analysis of risk which can be used during the development of mitigation and management strategies as well as to inform Marine Spatial Planning processes.
Measuring artificial light at night in the field, and its impact on mosquito vector abundances
(University of Pretoria, 2024-11) Coetzee, Bernard Walter Thomas; Smit, Izak P.J.; Robertson, Mark P.; layla.vanzyl2000@gmail.com; Van Zyl, Layla
The regular variations of light in natural light:dark cycle serve as crucial cues for the timing of biological events. However, the increasing prevalence of artificial light at night (ALAN) disrupts these natural light cycles, having harmful effects on both human and environmental health. ALAN impacts various insects, including key disease vectors like Anopheles mosquitoes, several of which are responsible for transmitting malaria. While there are several methods to measure ALAN, most lack the ability to capture spectral information, making it challenging to quantify ALAN for ecological applications. In this study, I utilized the globally novel Environmental Light Field (ELF) method to characterize the artificial light environments in and around exemplar rural houses in South Africa, Uganda, and Mozambique. Given that the lighting in these areas may significantly influence the risk of vector-borne diseases, especially malaria, it is essential to understand these light conditions. The ELF method makes use of repeat photography to characterise the light detected by an animal’s eye in an entire environment, taking environmental influences such as reflection, refraction and transmission of light into account. My findings indicate that light-emitting diode (LED) lighting dominates across the study sites, with large variability in both intensity and spectral composition among houses with different structures. Interestingly, light conditions inside houses showed more variability than those outside, with light intensities outside ranging from 11.2 to 14 lit (i.e., spanning 2.8 orders of magnitude) and that inside from 11.9 to 15 lit (i.e., spanning 3.1 orders of magnitude). The ELF method effectively measures light as perceived by the animal eye, providing a robust tool for comparing artificial lighting conditions. In this study I also investigated the relationship between the characteristics of the light environment and the abundance of Anopheline mosquitoes in Mamfene, South Africa. While overall white light intensity was not a significant predictor of Anopheline abundance, the percentage of blue light had a significant negative impact on their abundance. By including light environment characteristics, such as blue light content, as predictor variables, we can gain a more comprehensive understanding of factors affecting Anopheline species distribution, abundance, and consequently, potential disease transmission risks.
Host genetics and haemoparasite diversity in the common warthog (Phacochoerus africanus) from South Africa
(University of Pretoria, 2024-12) Bastos, Armanda D.S.; Keaton.rea@tuks.co.za; Rea, Keaton
The common warthog (Phacochoerus africanus) was initially confined to the northern provinces of South Africa; however, in recent decades, they have expanded southwards, with an extralimital range now encompassing most of the country. These expansions are primarily through their natural dispersal ability and translocations into southern conservation areas. However, the degree to which these populations are connected and South African warthogs' genetic structure and diversity is not yet known. Previous studies on warthog genetics have been continent-wide; however, they have not included warthogs from South Africa. We aimed to address this gap by sequencing 92 mitochondrial DNA (mtDNA) and 23 Sex-determining region Y (SRY) gene sequences from significant populations across the warthog’s traditional and extra-limital range. The mtDNA sequences defined 17 haplotypes, whereas the SRY gene defined only one haplotype. Haplotype network analysis revealed a structure reflecting the southward expansion through natural dispersal and recorded translocations. Overall haplotype diversity (Hd) ranged from 0.38 to 0.83, with southern population centres (Addo Elephant National Park Hd=0.38, and Mokala National Park Hd= 0.41) representing the lower end of the range, likely reflecting a founder effect from the initial translocated groups. When combined with continent-wide data, the South African population was confirmed to be an extension of the previously defined southern clade, reflecting the southward expansion of the species from East Africa. The secondary aim of this study was to evaluate the prevalence and diversity of three haemoparastic bacterial genera, namely Anaplasma, Bartonella and Mycoplasma, in warthogs (Phacochoerus africanus) in the Kruger National Park (KNP). Molecular estimates of infection rates for these three genera were determined from DNA extracts from 100 EDTA blood samples using a variety of PCR assays. For Anaplasma, assays targeting the 16S rRNA, citrate synthase (gltA) and the heat-shock operon (groESL) genes were utilised. These assays and subsequent nucleotide sequencing confirmed that 50% (50/100) of warthogs were Anaplasma-positive, with juveniles displaying a significantly higher infection rate (15/18; 83.3%) than adults (35/82; 42,68%). Phylogenetic analyses of individual and concatenated gene datasets confirmed that the Anaplasma species in warthogs is closely related to a novel species detected in Ornithodoros soft ticks from Zambia. Bartonella screening utilised six published assays targeting the riboflavin synthase (ribC), gamma subunit of NADH dehydrogenase (nuoG), and the RNA polymerase beta-subunit (rpoB), citrate synthase (gltA) and filamenting temperature-sensitive mutant Z (ftsZ) gene regions. Despite this broad range of targets, no Bartonella DNA was detected in any samples, suggesting either an absence or very low level of this bacterial genus in warthogs in the KNP. Lastly, samples were screened for Mycoplasma DNA with PCR assays targeting three gene regions, namely 16S rRNA, ribonuclease P (RNase P) and 23S rRNA. Mycoplasma was confirmed in 60/100 (60%) samples through amplification and sequencing of at least one of the three targets. Nucleotide sequencing and phylogenetic analyses of individual and concatenated gene targets confirmed Mycoplasma strains fall within the Mycoplasma parvum-M. suis clade, with one variant, sister to M. parvum, likely representing a novel species. This study on the genetic structure and haemoparasitic diversity in the common warthog highlights both how their expanding distribution, through dispersal and human-mediated translocation, is reflected in their genetic structure and how a significant South African population hosts two potentially pathogenic bacterial genera, Anaplasma and Mycoplasma.
Patterns and drivers of mammal diversity across the Waterberg mountain catchment area, South Africa
(University of Pretoria, 2024-08) Keith, Mark; Somers, Michael John; Parker, Daniel Matthew; michaeltrevornel@gmail.com; Nel, Michael Trevor
Mammal diversity varies spatially and temporally globally, influenced partly by natural and human-induced disturbances on ecosystems. In South Africa, there has been a significant shift in land use from agriculture and livestock farming to wildlife husbandry and breeding. This transition, driven by economic incentives and a move from pastoralism to conservation, has altered wildlife "ownership" and production practices. This study, part of the Foundation Biodiversity Information Program Waterberg Mountain Catchment (FBIP WMC), focuses on the Waterberg region in Limpopo, South Africa. The area is characterized by diverse habitats, topography, and vegetation, yet it remains relatively understudied. The uniqueness of the Waterberg makes it a critical area for conservation efforts. The objectives of this study were to determine the current presence of mammal species compared to historical records, assess the richness, abundance, and diversity of mammal species across the Waterberg, and analyze the fine-scale response patterns of ungulate species to vegetation clearing practices on two privately owned game reserves. This study aims to provide a better understanding of mammal biodiversity in the Waterberg and highlight the potential impacts of land tenure and vegetation manipulation on local mammal populations. Firstly, historical data from virtual museums, online databases and published literature were used to determine the mammal species that could be found in the area. Data obtained from camera traps deployed across 18 properties of the Waterberg were then used to determine the current diversity of mammal species present in the area, which could be determined using camera trap surveys. The FBIP WMC study matched the historically derived data (n = 62 mammals) with some additions and some species missing from the current camera trap survey. Additionally, this study highlights the importance of pairing digital/ virtual repositories with data from scientific studies. This integration benefits conservation efforts by providing better information and management strategies, ultimately promoting and safeguarding biodiversity for future generations. Secondly, species richness, abundance, and evenness across the FBIP WMC were assessed. Non-governmental game reserves exhibited the highest species richness, averaging 39 species, followed by nature conservancies with 36 species, and livestock/agricultural properties with 31 species. Species richness observed in the study aligned with Chao2 diversity estimates for most properties. Generalised linear modelling indicated significant variations in species richness across properties, influenced by factors such as dangerous game fence type, game reserve land use, and the Central Sandy Bushveld vegetation type. Privately owned Big-5 game reserves had higher species abundances, while livestock and agricultural properties showed moderate similarity and lower abundances of unmanaged species. State-owned conservancies had some overlap in unmanaged species. Feeding guild analysis revealed that mixed feeders, omnivores, and selective browsers were common, with specific reserves showing unique proportions of bulk grazers and insectivores. Mesocarnivores remained irrespective of the degree of anthropogenic changes, being abundant across all properties. Thirdly, my research investigated the fine-scale response patterns of ungulate species to vegetation clearing practices as a management tool for woody encroachment. There were differences in Vegetation Condition Index (VCI) and Vegetation Condition Assessments (VCA) between Kaingo and Qwabi, with differences in the mix of woody plants, forbs, and grasses. The site where the bulldozer treatment was used on Qwabi had the best VCI for plant quality. Ungulate occupancy differed significantly between treated and untreated sites at Kaingo. Greater Kudu and Plains Zebra were found in both site types, but most other species preferred untreated sites, which showed higher overall occupancy probability. At Qwabi, more ungulate species were observed at treated sites, although four species were absent there. Blue Wildebeest, Impala, and Plains Zebra favoured treated sites, while Bushbuck showed no site preference. The interaction of VCI and distance to water did not influence individual species’ occupancies. In conclusion, the combined approach of using a large-scale camera trap study, such as the FBIP WMC project, as well as a small-scale study, such as the herbivore response study, is essential for designing, developing, and implementing effective conservation and management plans that promote the longevity and success of mammal populations and ultimately the ecosystems they inhabit. By using both approaches, researchers can improve recommendations to landowners and managers, promote effective habitat restoration, and ensure the conservation of biodiversity in the face of increasing human pressure on the environment.
Reproductive behaviour, space-use and endocrine correlates of free-ranging impala (Aepyceros melampus) during the pre-rut, rut and post-rut phases
(University of Pretoria, 2025-01) Ganswindt, Andre; Webster, Andrea; juanitawessels00@gmail.com; Wessels, Juanita
Reproductive success is closely tied to an animal’s ability to adapt to social and environmental changes, particularly during physiologically stressful periods. Impala (Aepyceros melampus) are seasonally breeding, gregarious antelope and are considered a keystone species, given they contribute significantly to the game meat and tourism industry. Additionally, this species plays a crucial role in vegetation community composition, ecosystem functioning and facilitating the persistence of other species. Despite being an easily accessible study species, there is still limited information on how impala in the South African Highveld respond behaviourally and hormonally to the different phases of the rut. The aim of this study was to investigate reproductive behaviour, space-use and changes in faecal androgen metabolite (fAM) and faecal glucocorticoid metabolite (fGCM) concentrations in free-ranging male and female impala (Aepyceros melampus) over the pre-rut, rut and post-rut phases. As a pre-requisite, the phases of the rut had to be identified in the South African Highveld. Further, two enzyme immune-assays (EIA) had to be biologically validated to determine the most suitable assay for fAM quantification in this species. Lastly, changes in fAM and fGCM concentrations post-defaecation had to be investigated to assess how time and environmental variables affect the stability of hormone metabolites in faeces. Pre-copulatory (investigation, flehmen and following/chasing) and copulatory (mounting) behaviours were recorded as behavioural events and later converted to weekly frequencies. Additionally, latitude and longitude coordinates for breeding and bachelor herds were recorded during each phase of the rut and subsequently analysed. After the successful establishment of a non-invasive method for steroid hormone assessment, faecal samples were collected from male and female impala. Comparisons of the respective quantified hormone metabolite concentrations were made between males of different age classes and social ranks, the phases of the rut and across the two different sections of the Telperion Nature Reserve (TNR). The data indicate that the impala rut in the South African Highveld begins on 9 May and concludes on 15 June. Further, the observed differences in the frequency of reproductive behaviours within and across the phases of the rut provide insights into behavioural investment patterns. Breeding and bachelor herds adapted their space-use in response to the intra-specific interactions and resource availability. We found that the testosterone EIA was the best-suited assay for fAM analysis in male and female impala compared to the epiandrosterone EIA. The hormone stability study showed that immunoreactive fAM concentrations of male and female impala remained stable for up to 12h post-defaecation regardless of the exposed treatment. However, a sex-specific difference in fGCM post-defaecation stability was evident. The observed variation in fAM and fGCM concentrations among the compared variables is driven by a range of complex factors, including ethological, social and environmental aspects. This study increases our understanding of impala population dynamics, showing that they adapt their behavioural and hormonal responses to local social and environmental conditions associated with the rut to enhance reproductive success. As a result, reproduction cannot be viewed as an isolated event; instead, it must be understood in the context of the surrounding environment to fully capture its dynamics. The significance of understanding these aspects is emphasised in this study, as it may promote effective management strategies to ensure the long-term sustainability of impala and their ecosystem.
Oviposition dynamics and sex ratio model assumptions in pollinating fig wasps
(University of Pretoria, 2024-12) Greeff, Jacobus Maree; Van Noort, Simon; De Waal, Pam; simisom2000@gmail.com; Mnguni, Simiso Polite
This thesis investigates a few assumptions of sex allocation in fig wasps, a pivotal subject in evolutionary biology and sex ratio theory. We investigate specifically if species can be considered in isolation of one another, and if the females that share a fig, oviposit simultaneously or sequentially. In doing so the study tries to explain deviations in fig wasp sex ratios from predictions made by classical frequency-dependent selection models. As more mothers oviposit in a fig, their offspring sex ratios become less female biased as predicted, but to a lesser degree than is optimal. The adaptive adjustment is a result of the two mechanisms of sex ratio adjustment in pollinating fig wasps: a passive response due to unlaid female eggs in competitive environments, and a facultative response involving increased male egg production in the presence of co-foundresses. An information-theoretic approach allowed me to contrast different hypotheses and to conclude that the presence of heterospecifics disrupts these mechanisms, leading to maladaptive sex ratios and illustrating trade-offs between versatility and specialization. The standard sex ratio models based on local mate competition theory assumes that females oviposit simultaneous. My direct observations show that sequential oviposition is in fact more frequent than simultaneous oviposition and this can help to explain sex ratios that are too female-biased in multi-mother figs. To investigate sequentiality further, I used an Approximate Bayesian Computation approach to estimate parameters such as wasp entry probabilities, foundress longevity, and ostiole closure timing The estimated parameters suggests that sequential oviposition is very likely because figs stay open for longer than wasps stay alive.
Southern right whale (Eubalaena australis) migratory and foraging behaviour in a changing climate
(University of Pretoria, 2025-01-20) Vermeulen, Els; Vichi, Marcello; u15029507@tuks.co.za; Germishuizen, Matthew
The name “right” whale reflects the violent history of southern right whales (SRW, Eubalaena australis) since their sluggish, predictable coastal behaviour and the tendency to float when dead led to the reputation of being the “right” whales to hunt. Now, the characteristics that contributed to their near demise carry a less sinister connotation, that of being the “right” climate sentinel. Their life histories and wide-ranging migratory behaviour make SRWs ideal candidates for monitoring environmental change. SRWs are capital breeders with discrete periods in their life histories dedicated to foraging and reproduction. Therefore, females have a strong impetus to accumulate sufficient energy reserves during their foraging period to sustain them through pregnancy and calf nursing. Thus, a strong connection exists between foraging efficiency and reproductive success. Foraging efficiency is largely dictated by the environment’s ability to generate productive feeding grounds. Sea ice, for example, has a fundamental role in the life history of Antarctic krill (Euphausia superba), a key prey species for SRWs. Changes in reproductive success in SRWs may indicate climate-induced alterations in prey, such as reductions in sea ice, in their offshore feeding grounds. Following a steady period of recovery from commercial whaling, SRW populations recently began displaying signs of reduced population growth rates and reproductive failure. This prompted an in-depth assessment into potential drivers behind these changes, and their contemporary migratory and foraging behaviour. This thesis is focused on the South African population, which through annual aerial surveys has been extensively monitored since 1969. The resultant time-series of population demographic data has revealed drastic reductions in reproductive success after 2009, together with a northward shift in foraging location as indicated by stable isotopes, and a decline in maternal body condition. To better understand these changes, an assessment into patterns of satellite-derived chlorophyll and sea ice as proxies for foraging habitat quality was performed over the period of observed population-level reductions in reproductive success. This revealed substantial declines in sea ice over historically important foraging grounds for SRWs, which likely contributed to reduced availability of their main prey at high-latitudes; Antarctic krill. The thesis reports on the use of animal-borne Conductivity, Temperature and Depth instruments and dive depth recording tags in better understanding the environmental characteristics of their mid-latitude foraging grounds. Results highlighted the importance of ocean fronts, temperature and salinity in determining favourable foraging grounds. Finally, through the deployment of 26 location-only satellite tags, a comprehensive investigation into the contemporary offshore migratory and foraging behaviour of South African SRWs was performed. From these, areas of high use were identified, and the presence of foraging whales was predicted from eight environmental covariates using Random forest. This significantly increased our knowledge of SRW contemporary habitat use. The findings of this thesis highlight the strong connections between SRWs and their environment, and the vulnerability of the species to climate change and variability. This also reaffirms the utility of SRWs as the “right” sentinels for environmental change.
Foraging strategies and spatial-temporal partitioning by brown hyenas (Hyaena brunnea, Thunberg 1820) around a coastal food source: implications for conservation and ecotourism in the TsauǁKhaeb National Park, Namibia
(University of Pretoria, 2024-11-16) Somers, Michael J.; Wiesel, Ingrid; marie.lemerle@strandwolf.org; Lemerle, Marie Anna
The coastal ecosystem of the TsauǁKhaeb National Park in Namibia serves as an important foraging ground for both brown hyenas (Hyaena brunnea) and black-backed jackals (Lupulella mesomelas). The presence of breeding colonies of Cape fur seals (Arctocephalus pusillus pusillus) provides a year-round food source, with hunting opportunities for the local carnivores. At the Baker’s Bay seal colony, brown hyenas display unique behavioural patterns around a concentrated food source. This thesis aims to investigate the temporal activity patterns, foraging behaviours, movement strategies, and human-wildlife interactions of brown hyenas in this unique context, providing insights that are essential for sustainable wildlife management and ecotourism development. This study was conducted at the Baker’s Bay seal colony from November 2020 to December 2023. A combination of direct behavioural observations and camera trap data were used to analyse the activity patterns of brown hyenas and black-backed jackals at the seal colony. Brown hyenas exhibited individually distinct activity patterns, ranging from nocturnal to diurnal. During diurnal observations, brown hyenas were most active around midday, while black-backed jackal numbers peaked around dawn and dusk. Carnivore activity was influenced by weather conditions. Additionally, brown hyenas showed a preference for fresh carcasses at the seal colony, and displayed surplus killing and caching behaviours of seal pups. Male brown hyenas hunted more frequently, whereas females demonstrated greater efficiency. The analysis of movement patterns using satellite GPS collars revealed that coastal brown hyenas had smaller home ranges and less varied diets compared to their inland counterparts, emphasising the importance of seal colonies as primary foraging sites. Collared brown hyenas exhibited significant overlap in their home ranges around key resources, leading to territorial disputes and highlighting the complex social dynamics among brown hyena clans. The potential for ecotourism development at Baker’s Bay was also explored. Brown hyenas were sensitive to movements such as people walking or vehicles driving, and human disturbances altered their foraging behaviour. Recommendations for sustainable tourism include controlled visitor access, use of infrastructure to minimise disturbance, and continuous monitoring of brown hyena activity patterns to ensure the long-term sustainability of ecotourism in the area. Overall, this study underscores the importance of balancing tourism with conservation efforts. The results provide insights into the behavioural ecology of brown hyenas in a coastal ecosystem, and highlight the importance of developing conservation strategies that consider the unique adaptations of coastal predators and the impact of human activities. By proposing guidelines and recommendations for policymakers and tour operators, this research contributes to the establishment of responsible and sustainable wildlife tourism practices, ensuring the conservation of this unique ecological hotspot.
Evaluation of stable isotope ratios of historical and modern samples of invasive and indigenous murid rodents, with respect to historical urbanization in Gauteng Province, South Africa
(University of Pretoria, 2024-07) Chimimba, Christian Timothy; Hall, Grant; u16125119@tuks.co.za; Engelbrecht, Armand
Natural history traits such as sex and ontogeny (i.e., age), environmental factors such as season, habitat, and time of sampling, and the nature and extent of urbanization may influence the trophic ecology of rodents. The current study used stable isotope analysis (SIA) of modern and historical samples to: 1) investigate the potential influence of natural history traits and environmental factors that also included metrics of urbanization on carbon (δ13C) and nitrogen (δ15N) isotope ratios in murid rodents from Gauteng Province, South Africa; and 2) evaluate their potential trophic ecological shifts due to urbanization over a historical time scale. SIA was conducted on biologically inert fur samples of modern and historical samples (i.e., museum-preserved samples collected over a time scale) of three invasive (Rattus rattus, R. norvegicus and R. tanezumi) and three indigenous (Aethomys ineptus, Mastomys coucha and Otomys angoniensis) murid rodents. Generalized linear models (GLM), analysis of variance (ANOVA) and Tukey’s post-hoc analyses showed that sex, age, and sampling year had minimal impact on δ13C and δ15N isotope ratios, but not sampling locality and season. These results were supported by the analysis of percentage trophic overlaps based on sample size-corrected standard ellipse areas (SEAc). Collectively, these results suggest that in the last century, short-term seasonal fluctuations accounted for a larger proportion of isotopic variation than long-term environmental changes. The results also showed that qualitative categorical land use data as a proxy for urbanization did not adequately account for changes in rodent isotope ratios. Consequently, an attempt was made to identify quantifiable potential sources of short-term variation in δ13C and δ15N stable isotope ratios in these rodents. The identified quantitative variables included monthly median temperature and monthly total rainfall as short-term metrics of environmental change and Normalized Difference Vegetation Index (NDVI) as a metric for vegetation cover and impervious surface area (ISA), both as proxies for urbanization over a historical time scale. The analyses found that both metrics of short-term environmental factors and proxies of urbanization had no impact on δ13C ratios in any of the three invasive and three indigenous murid rodent species investigated, while δ15N ratios of the insectivorous indigenous A. ineptus and M. coucha were found to be influenced by monthly median temperature and impervious surface area. Overall, the largest %SSQs were due to error (i.e., residual), suggesting that apart from the metrics analysed and the interaction between them, there may be other unexplained components that are also responsible for the variation. These results suggest that the murid rodent populations investigated may be shielded from the negative impacts of short-term environmental factors and urbanization through the availability of excess food resources in one of the most urbanized landscapes in South Africa. This has implications on potential knock-on effects in other aspects of the behaviour and ecology of these rodents that may represent an urgent direction of focus for future research initiatives. These results highlight the potential impact of urban landscapes on the trophic ecology of invasive and indigenous murid rodents and their negative impacts on the conservation of other threatened species within urban settings.
Foraging patterns for protein baits by South African fruit fly pests (Diptera: Tephritidae)
(University of Pretoria, 2024-07) Weldon, Christopher W.; Manrakhan, Aruna; Msizisons@gmail.com; Ramaoka, Msizi Ronald
In sub-Saharan Africa, three fruit fly pests, Bactrocera dorsalis (Hendel), Ceratitis capitata (Wiedemann) and Ceratitis cosyra (Walker), are among those of economic significance for a number of commercially grown fruit and vegetable crops. Their presence leads to high yield losses and restricted access to export markets, and limits the economic and social value derived from these commodities. Protein baits are extensively used for monitoring and control of these and other fruit fly species. Control of fruit flies using protein baits or bait application technique (BAT- an attract and kill tactic) requires a sound understanding of their foraging patterns for protein so that application of baits leads to maximum response. The main aim of this project was to improve fruit fly control using tactics that incorporate protein baits. The spatial and temporal foraging patterns of Bactrocera dorsalis, Ceratitis capitata and Ceratitis cosyra for protein baits within a citrus tree with regard to fly age, sex and nutritional status were established in field cages. This was followed by the a study that determined the response of the three pest species to protein baits applied at two different densities. Results showed that bait location in the canopy affects response by B. dorsalis, C. capitata, and C. cosyra with more flies foraging for protein in the middle to upper canopy heights of the tree compared to protein bait positioned on the lower canopy and directly on the ground. The first study also revealed that nutritional status, age and sex influenced protein bait response, with 1 day-old flies with prior access to protein showing a lower response to protein bait, while 10-day-old protein-deprived flies intensely foraged for protein regardless of sex or species. Females responded more to protein baits than males, and foraging for protein peaked in the warmest part of the day when temperatures were between 20-30℃ at a relative humidity ranging between 40-80%. Furthermore, the second study showed that species, diet history and bait density had a significant effect on the response to protein bait. Ceratitis capitata females were more attracted to the bait followed by B. dorsalis, and C. cosyra with the lowest response. Similar to results obtained in the first study, protein deprived females were most responsive to the bait regardless of species and bait density. Additionally, females were more attracted to 10 droplets of 200 µL protein bait applied in 10 traps than a single 2000 µL droplet applied in one trap regardless of diet and species. Based on the results, protein baits should be applied between the mid and upper canopy heights and should be evenly distributed on the tree canopy for increased effectiveness of
Distribution and phenotypic population structure of the tsetse flies Glossina morsitans morsitans Westwood and Glossina morsitans centralis Machado in Zambia
(University of Pretoria, 2024-11) Sole, Catherine L. ; Pirk, Christian Walter Werner; Yusuf, Abdullahi Ahmed; u19395605@tuks.co.za; Muyobela, Jackson
Glossina morsitans s.l. is an efficient vector of African trypanosomiasis, a debilitating and fatal disease of humans and livestock. This study aimed at investigating the current distribution and phenotypic population structure of G. m. centralis Machado and G. m. morsitans Westwood to inform effective vector management strategies in Zambia. To achieve these objectives, the study also evaluating a vehicle-mounted sticky trap (VST) for effective and rapid sampling of G. morsitans over large geographic areas. Randomised block design experiments were used to establish the optimal design of VST. An extensive VST based tsetse survey was then conducted in all tsetse belts in Zambia. The occurrence records obtained from this survey were used to model the distribution of G. m. centralis and G. m. morsitans using a Maxent species distribution model. Landmark-based wing geometric morphometrics was undertaken to investigate the population-level phenotypic variation of the two subspecies. There were no significant differences in catch indices of VST constructed using an all-blue, all-black and 1:1 blue-black panel. Overall, the VST oriented in-line and baited with butanone and 1-octen-3-ol, caught 2.42 and 2.60 times more G. m. centralis and G. m. morsitans respectively, than the standard mobile trapping device, the black-screen fly round. The VST survey captured a total of 15,602 flies with G. m. morsitans (58%) and G. m. centralis (39%) being the most abundant. The predicted potential distribution for G. m. centralis was 80,863 km2 while that of G. m. morsitans was 70,490 km2 representing a 47 and 29% reduction compared to their historical distributions, respectively. Significant differences in wing centroid size and shape were observed between G. morsitans sexes, subspecies and sample locations within each subspecies range. The populations of G. morsitans were found to exhibit significant population-level variation in fly size and wing shape which suggests high levels of population structuring. The main drivers of this structuring could be random genetic drift in G. m. centralis demes and local adaptation to environmental conditions in G. m. morsitans populations.
Physiological and behavioural aspects of climate change vulnerability in ground-foraging passerines inhabiting South Africa’s Tankwa Karoo desert
(University of Pretoria, 2024-07-15) McKechnie, Andrew E.; Cunningham, Susan; Freeman, Marc Trevor; shortjames76@gmail.com; Short, James Curtis
In the face of anthropogenic global heating, understanding how endotherms persist both behaviorally and physiologically in response to temperature extremes has become increasingly important. For this reason, research has primarily focused on those species inhabiting desert environments, where harsh environmental conditions may leave arid-zone endotherms vulnerable to the effects of increasing air temperature (Tair). Due to their primarily diurnal foraging activity and small body size, arid-zone birds have been identified as being particularly vulnerable to the effects of climate change, and therefore the subject of much past and current research. Over the past decade, a multitude of studies have investigated the thermoregulatory performance of arid-zone birds in response to acute heat exposure, mainly quantifying evaporative cooling capacities as well as the maximum Tair species can withstand before the onset of severe hyperthermia (heat tolerance limits; HTL). Such studies have revealed that these variables are correlated with water dependence in southern African spp, with drinking species exhibiting larger evaporative cooling capacities and higher HTLs than their non-drinking counterparts. These data included several species from the Aluadidae, primarily from the genus Calendulauda, focusing on arid zones such as Namaqualand and the Kalahari. Physiological performance decreases in response to high Tb making maximum body temperature (MaxTb) an important metric in determining the maximum environmental temperature endotherms can tolerate. However, MaxTb was not included in the aforementioned analyses and has been found to vary in species occupying different climates. . Therefore, there remains scope to evaluate members of other lark genera occupying other arid zones within South Africa, while assessing whether MaxTb may also be correlated to water dependence. In addition to physiological responses, birds can also make use of thermoregulatory behaviours in response to temperature extremes, whether it be hot (i.e., panting, wing-spreading and shade-seeking) or cold (i.e., ptiloerection). While these behaviours may buffer individuals from the immediate effects of high and low Tair, the prioritization of these thermoregulatory behaviours has been found to force birds to compromise on time spent foraging and maintaining body condition. However, the effects of behavioural thermoregulatory trade-offs across summer and winter seasons and how these may be affected in the face of climate change remain unclear. Therefore, my master’s dissertation aims to address the aforementioned gaps in the literature, providing a quantitative thermal profile for a water-dependent lark species inhabiting the Tankwa Karoo, while providing insights into behavioural thermoregulation in response to seasonal temperature extremes. In my first chapter, I aimed to quantify the thermoregulatory performance and heat tolerance of a water-dependent lark species from the genus Galerida inhabiting the Tankwa Karoo. To do this, I collected thermoregulatory data for 8 large-billed larks (Galerida magnirostris) using open flow-through respirometry, exposing individuals to steadily increasing Tair setpoints until they reached their HTL. Large-billed larks displayed a thermoregulatory capacity comparable to that associated with most desert birds studied to date, possessing a MaxTb of ~ 45°C and an HTL of ~50°C. Combining these data with that previously published, I expanded upon previous efforts investigating the links between drinking behaviour and thermoregulation by assessing whether thermal physiology differences between regularly drinking and occasional - /non-drinking species extend to MaxTb. To do this, I collated published data of MaxTb and the slope of body temperature (Tbslope) above the upper critical limit of thermoneutrality for 18 other southern African arid-zone passerines. My interspecific analyses revealed no differences between drinking and non-drinking species. Therefore, my findings provide a quantitative thermal profile for large-billed larks inhabiting one of the hottest and driest areas in southern Africa, while my interspecific analyses reiterate the overall importance of evaporative cooling in the thermoregulation of arid-zone birds. In the face of predicted decreases in rainfall brought about by climate change, this chapter emphasizes the importance of the conservation of key water sources within arid zones and the role these can play in the persistence of desert avifauna. In my second chapter, I tested the hypothesis that thermoregulatory behaviours are traded off against foraging in response to seasonal temperature extremes, using Karoo chats (Emarginata schlegelii ) as a model species. To do this, I collected behavioural data over both summer and winter seasons for 20 individuals. My data indicated no trade-offs between foraging and thermoregulation during the winter season. However, during summer individuals were found to prioritize heat dissipation behaviours at the expense of time spent foraging in response to high Tair. To gain insight into how these trade-offs or lack thereof may be affected if current climate trends continue, I modelled maximum and minimum daily temperatures for the Tankwa Karoo over the last 38 years. These data revealed limited trends except for a 0.02°C increase in daily summer maximums. Therefore, chapter 2 highlights that while Karoo chats may not be constrained by Tair experienced during the winter season, they may be constrained by thermoregulatory trade-offs between heat dissipation behaviours and foraging during the summer season. These thermoregulatory trade-offs may persist and potentially be exacerbated if current summer warming trends for the Tankwa Karoo continue, posing a threat to the long-term persistence of Karoo chats and other members of the avifaunal community inhabiting this area. In conclusion, my dissertation fills gaps in the current literature regarding aspects of water dependence and thermoregulatory performance, as well as behavioural responses to seasonal temperature extremes. The results presented in my dissertation also provide a foundation on which future studies may build, by addressing topics such as behavioural thermoregulatory trade-offs and the impact these may have on the persistence of the Tankwa Karoo avifaunal community. My chapters also provide insights into the possible impacts increasing Tair could have on the physiological and behavioural thermoregulatory mechanisms in arid-zone birds inhabiting the Tankwa Karoo, highlighting the need to conserve these landscapes in the face of advancing climate change.
Development of effective biorationals for sustainable management of the invasive South American tomato leafminer Phthorimaea absoluta Meyrick (Lepidoptera: Gelechiidae)
(University of Pretoria, 2024-09) Torto, Baldwyn; Yusuf, Abdullahi Ahmed; u21831409@tuks.co.za; Adams, Bashiru
The tomato leafminer, Phthorimaea absoluta Meyrick (Lepidoptera: Gelechiidae) formerly known as Tuta absoluta is an invasive pest of Solanaceous crops with preferences for cultivated tomato (Solanum lycopersicum) where it is a major pest. Herbivory by P. absoluta larvae causes 80-100% yield losses in unprotected fields, with an estimated mean seasonal production loss of at least 114,000 tonnes, translating to about US$ 59.3 million in economic losses in Kenya. Synthetic chemical control has been the mainstay in managing the moth, with limited success because of the cryptic nature of the feeding larvae, the rapid evolution of resistant populations of the moth, and more importantly the negative effect of synthetic chemicals on the environment and non-target organisms. Hence, there is a global demand for more eco-friendly alternatives such as using biorationals to control the moth. Using behavioural assays, chemical analysis, and field trials, behaviour-modifying compounds that mediate the interaction of host, non-host plants, P. absoluta, and two native natural enemies associated with the pest including the generalist mirid predator Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) and the larval parasitoid Stenomesius japonicus (Ashmead) (Hymenoptera: Eulophidae) were identified. The mirid predator N. tenuis is zoophytophagous and may become a pest in the absence of prey by feeding on the tomato plant. The results from these studies revealed that terpenes from constitutive volatiles of host plants such as tomato and nightshade and some selected non-host Asteraceae plants including marigold (Tagetes minuta) and blackjack (Bidens pilosa) elicit significant behavioural responses in the moth and the associated natural enemies. Additionally, terpenes and green leaf volatiles (GLVs) from the predator N. tenuis-induced host plant defense volatiles influence the tritrophic interaction between host plants, P. absoluta, N. tenuis, and S. japonicus. Field trials also showed that combining the sex pheromones (1-octanol and hexyl hexanoate) identified from the Kenyan population of N. tenuis with specific visual cues such as red and white delta traps can be used to suppress both P. absoluta and N. tenuis populations, respectively in a tomato field. Overall, these studies identified different behaviour-modifying chemicals that can be developed into effective biorationals for the sustainable management of P. absoluta and the predator N. tenuis when it becomes a pest.

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