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The effect of stressors, disturbance regimes and environmental gradients on riparian arthropods: implications for management and conservation.
(2025) Hadebe, Asande.; Munyai, Thinandavha Caswell.; Slotow, Robert Hugh.; Nkuna, Sindiso Charlotte.
Riparian zones remain highly threatened by anthropogenic activities and climate change despite being ecologically valuable ecosystems. Understanding their complex and dynamic nature is crucial to effectively restore, manage, and conserve them and their biodiversity. Therefore, this study aimed to examine the influence of riparian environmental gradients, stressors, and disturbance regimes on the biodiversity of terrestrial arthropods and their implications for management and conservation policies. The first objective was to systematically review, using PRISMA guidelines, the response of riparian arthropods to flooding, alien plant invasion, and river engineering at a global scale and identify potential management strategies. The second objective was to determine, at a local scale, whether seasonal changes, location and increasing distance along the uMngeni riparian habitats, and from these habitats to the adjacent uplands, affect ant and spider diversity, community composition, and their foraging strategies, using pitfall traps. Findings from the systematic review highlighted that terrestrial arthropods’ biodiversity was predominantly adversely affected by flooding, alien plant invasion, and river engineering due to changes in environmental conditions, although responses to alien plant invasion differed among taxa. At the local scale, ant and spider richness in the studied gradients were not affected by seasonality or distance from the river and along the river. However, during the wet season, ant abundance decreased with increasing distance from the riparian to the upland areas, while spider abundance increased. The representation of spider foraging strategies was affected by season and location (study sites: Umgenipoort vs Hilton), contrary to that of ants which was only influenced by distance. Distance from the riparian habitats to the uplands significantly influenced ant community composition, whereas seasonal variation was the primary driver of spider community composition. Species turnover mainly accounted for overall beta diversity, with some ant and spider species unique to specific distances within the studied gradients. To conserve riparian biodiversity and function from further threats, eligible studies from the systematic review suggested creating and protecting heterogeneous habitats within riparian zones, restoring native vegetation and natural water flow, while considering species-specific ecological needs. This study has highlighted the factors that compromise riparian biodiversity and ecological processes that explain the observed patterns, providing valuable insights for conservationists to predict ecological changes. It also highlights the need for collaboration and long-term monitoring to sustain biodiversity and ecosystem functions along riparian zones.
Submerged gravel shorelines of the Inner to mid-shelf offshore Hottentot’s Bay, Namibia.
(2024) Heeralal, Tamera.; Green, Andrew Noel.
The western margin of southern Africa hosts extensive diamond placer deposits spanning from the lower Orange River to the southern Namibian coastline. These diamonds are associated with gravels deposited by surfzone processes during sea level fluctuations. During the postglacial transgression (23,000 to 6,000 BP), these diamondiferous gravels were concentrated and submerged. This study focuses on Area 4 of ML103A offshore Hottentots Bay, employing pseudo-3D seismic profiles, multibeam bathymetry, backscatter data, and over 6,400 drill cores to analyse the geomorphology and seismic stratigraphy of the inner to mid-shelf region. With the use of a pseudo-3D grid of ultra-high-resolution sub-bottom profiles and extensive borehole data, this study reconstructs the morphology of the paleo-land surface (H1) on which the current shelf sediments lie. H1 comprises a weathered bedrock surface overlain by saprolite or clay and mantled by Eocene-age sandstones. The overlying unconsolidated sediment consists of four seismic and lithostratigraphic units (C-F), including lowermost gravel Units C and D deposited in multiple phases from late Oligocene to late Pliocene/Pleistocene. These deposits formed lowstand lags in small channels on the inner shelf edge and developed into a thickly embayed beach on the innermost shelf. The bedrock-hosted embayment provided preferential accommodation for multi-stacked gravel beaches, contrasting with barrier spit and back barrier sequences to the south, closer to the Orange River. Once accommodation in the embayment was filled, material spilled into the strait, forming linear beaches anchored by a landward bedrock high, resistant to wave reworking and preserved through overstepping during significant sea level rises, notably MWP-1B of the Holocene. The dissertation emphasizes the need for further dating of these gravel beaches, challenging due to the polycyclic nature of their materials.
Southern African pythons (Python natalensis): diet, human perceptions, and persistence despite anthropogenic factors.
(2025) Kyle, Kirsty Jane.; Downs, Colleen Thelma.
Throughout the world, biodiversity is facing declines for multiple reasons, including climate change, land transformation, and habitat loss. Many species are facing decline and extinction, with little known about their basic life cycles and behaviours. This is especially true of ectotherms because of the additional challenges and difficulties involved in studying animals that do not feed as regularly as endotherms and are not necessarily active every day, or are not always readily apparent when they are active. This study focused on the southern African python (Python natalensis), the largest snake on the southern African subcontinent, about which little is known. Some research has been conducted regarding their breeding behaviour, but little is known about their diet, social interactions, persistence, seasonal and temporal behaviour, or anthropogenic impacts, uses, or importance. The overall aim of this study was to assess the persistence of the southern African python in South Africa, determining the threats faced and establishing baseline information about their life history, as well as documenting their anthropogenic significance. A systematic literature review was conducted on the family Pythonidae, examining the work done on the various species worldwide and highlighting areas that could be focused on for the benefit of their conservation. We found that the vast majority of work has been conducted on individuals in captivity, which has negative consequences for the management and conservation of wild animals. Social media was used to establish a detailed list of species of mammals, birds, reptiles, and fish that southern African pythons have been recorded eating, as well as document several novel feeding behaviours, specifically scavenging, caudal luring, active hunting, and an ontogenetic shift in their diets as they age. An online questionnaire and in-person interviews were conducted to gather information about the South African people’s perspectives on pythons, documenting a trend of positivity towards these snakes, while also highlighting misinformation, which was addressed in a bilingual educational poster.We assessed some of the cultural beliefs about these snakes, as well as some of their applications and uses in traditional medicine practices. Finally, we compared the occurrence data of southern African pythons over a ten-year time period, in light of land-use change, to establish whether they are persisting, increasing, or decreasing in their distribution in KwaZulu-Natal. We found that they are persisting through much of their range; however, there are proportionally more records from within protected areas than outside of them. We also established that pythons favour savannah regions, with rainfall between 500 and 900 mm p.a., below 400 m.a.s.l., with median summer temperatures between 22 and 26°C and median winter temperatures above 12°C. Conservation and management recommendations are made.
Shoreface stratigraphy: evolution and morphology observations from southern Mozambique.
(2024) Draycott, Henna Lesley.; Green, Andrew Noel.
Shoreface morphology and stratigraphy are poorly documented but are acknowledged to be important influences on shoreline behaviour during changing sea level. A wide, low gradient wave-dominated shoreface off Xai-Xai in southern Mozambique is developed on the Holocene wave ravinement surface cut into deltaic sands punctuated by lithified aeolianite ridges. The 2 km-wide mobile shoreface sand body extends to -23 m depth and averages 10 m in thickness. Seismic stratigraphic analysis accompanied by seabed cores, reveals the shoreface to be underlain by a deltaic sedimentary sequence. The modern shoreface mimics the wave ravinement surface and this, in turn is influenced by the presence of aeolianite ridges that create a pronounced break in slope that defines the base of the modern shoreface. Comparison with theoretical shoreface profiles reveals contrasting interpretations depending upon the model chosen and emphasizes the acknowledged but still little understood role of geologic inheritance on shoreface morphology and evolution.
The effect of linear infrastructure on vertebrate fauna in Hluhluwe-iMfolozi Park and northeastern KwaZulu-Natal, South Africa.
(2025) Cormac, Cameron Tyler.; Downs, Colleen Thelma.; Price, Cormac.; Streicher, Jarryd Peter.
Global anthropogenic growth continues to increase, threatening not only wildlife but the health of the entire biosphere. The anthropogenic growth coincides with an increase in vehicle traffic, placing further stress on natural environments as the mortality rates of fauna from vehicle collisions rise, thereby increasing human-wildlife conflict. It is to avoid this human-wildlife conflict that protected areas are so beneficial. However, global studies have shown that public roads in protected areas cause large numbers of wildlife mortalities, threatening the stability of these wildlife refugia, and that increasing tourism rates add further ecosystem stress by increasing wildlife-vehicle collisions (WVCs). The conflict faced by wildlife is also disproportionate between taxa, with reptiles and large predators facing the highest threat levels. Therefore, effective measures must be taken to minimise the effect of anthropogenic structures on natural environments as vehicle traffic density increases globally, particularly in Africa, where little research has been conducted on the ecological impact of linear infrastructure. In light of the conservation challenges associated with linear infrastructures, this study had four aims. Firstly, to identify the species assemblage of vertebrate WVCs along the R618 road that bisects Hluhluwe-iMfolozi Park (HiP) and of the R22 road that passes through the northern border of iSimangaliso Wetland Park (ISWP). Secondly, to determine the demographics of reptiles present on paved roads in HiP, ISWP and an adjacent developing community on ISWP’s border. Thirdly, to determine the amount of road avoidance by lions (Panthera leo) and blue wildebeest (Connochaetes taurinus) in HiP. Finally, to determine the interaction with anthropogenic structures by cheetahs (Acinonyx jubatus) and African wild dogs (Lycaon pictus) in HiP. Roadkill and herpetofauna presence data were collected along R618 and R22 in HiP, ISWP, and the ISWP-adjacent Giba Rural Community (GRC) monthly from March 2021 to March 2023. Vertebrate mortality and reptile occupancy were determined by assessing species diversity and abundance, mapping hotspots of mortality and reptile occupancy and using a suite of ecological factors to identify drivers of vertebrate mortality and reptile occupancy. Spatial analysis programs and global positioning system (GPS) data collected from 11 lions and 21 wildebeest were used to determine the average distance to roads for the two species and to examine how this distance differed across road types. Additionally, GPS data collected from nine collared cheetahs and 17 collared African wild dogs were used to determine the average distance to anthropogenic structures and to compare these distances across structures. In addition, hotspot analyses were conducted to determine key areas of use near roads or anthropogenic structures and statistical analyses of the habitat features were performed to determine how they affected the distance kept from roads for lion and wildebeest and anthropogenic structures for cheetah and wild dogs across multiple wet and dry seasons from May 2019 to April 2022. A total of 1606 road mortalities were recorded, with small-bodied vertebrates (< 5 kg) comprising most of the identified species. Amphibians had the highest mortality rate (1066 individuals), while birds had the highest species diversity (31 identified species). High mortality levels were concentrated in areas with unsloped road surfaces and increased vehicle traffic within HiP, while the surrounding habitat had a larger influence on mortalities within ISWP. Reptile presence was significantly higher in protected areas. However, the majority (78.3%) were found as road mortalities, with a significant difference between the number of live and dead individuals observed between protected and unprotected land. Snakes comprised the majority (70.3%) of observed reptiles, with reptile observation frequencies varying according to habitat intactness and type, as well as vehicle traffic patterns and road design, with light conditions having a minor influence on reptile road occupancy. The majority of lion and wildebeest GPS fixes were within 1 km of roads in HiP, with hotspots of wildebeest activity near roads (within 400 m) occurring close to water sources, and hotspots of lion activity near roads occurring near areas frequently utilised by tourists or park staff. Where distance to dirt and paved roads, and to tourist locations, were key driving factors, significant differences were observed between lion and wildebeest males and females, with male lions and female wildebeest maintaining the smallest distances to roads. Finally, despite cheetah and wild dog heavily utilising over 20,000 ha (21%) of the total area protected by HiP, both species only had a significant presence in less than 3% (~2,880 ha) of HiP. Cheetahs also maintained greater distances from anthropogenic structures than wild dogs, with male cheetahs and female wild dogs maintaining the smallest distances for each species. Distances from anthropogenic structures were lowest near dirt roads and unfenced structures and highest from paved roads. The results showed that intervention is needed along portions of the two public roads in both protected areas and the ISWP adjacent GRC, particularly during the wet season, with mortality rates as high as 13 carcasses per km. Mitigation measures should be implemented to reduce wildlife mortality along roads in both locations, with specific measures targeting small vertebrates. All planned mitigation measures should focus on the sections identified as high mortality zones. Further studies are needed, as roads in HiP clearly negatively affect lions and blue wildebeest, with both species avoiding them. As hotspots of lion, blue wildebeest, cheetah, and African wild dog activity were centred around areas with typically high rates of human visitation, this increases the risk of human-wildlife conflict and the influence of human activity on movement patterns in both lions and blue wildebeest. This is of concern as lions, cheetahs, and African wild dogs are species whose persistence is threatened in HiP. Therefore, this study's results provide key insights into conservation concerns and further indicate the need for more effective species management to reduce human-wildlife conflicts in the rural communities surrounding HiP and ISWP.