In the arid African savanna, the limited availability of water strongly affects plant productivity, but other key drivers of vegetation dynamics, such as herbivory and fire, are usually considered to have a relatively minor impact. The main purpose of this study was to characterise the spatial and temporal pattern in plant productivity in the 100 000 hectare Tswalu Kalahari Reserve (TKR) in the semi-arid Northern Cape and relate the observed changes to potential drivers using medium spatial resolution of MODIS Enhanced Vegetation Index (EVI) time series data (16 day, 250 m) from 2000 to 2015. The time series of EVI for the past 16 years in TKR presented a highly seasonal pattern which fluctuated between years. A composite of annual small integrated value of EVI images highlighted spatial and temporal heterogeneity of plant productivity in the area. The EVI value was mainly influenced by rainfall and effect of fire and herbivory was considered to be minor. These observations confirmed the extreme variability of plant productivity in the drylands in the summer rainfall region of South Africa. Additionally, most of the values concerning the phenometrics of EVI differ significantly among vegetation types. This suggests that the structure and function of the vegetation determine plant productivity as well as their being a possible effect of soil property and reflectance. The trend in plant productivity computed by residual trend analysis (RESTREND) detected a significant positive trend in plant productivity in the east and south west of TKR, which overlapped with shrub-dominated vegetation, providing evidence for possible ongoing bush encroachment in these areas. On the other hand, a negative trend was detected in some locations in the west. The data generated from MODIS EVI and the small integrated value of EVI using TIMESAT produced biologically interpretable results. However, the correlative relationship between the EVI derived from Landsat Operational Land Imager (OLI) and plant cover estimated in the field was poor or not significant and needs to be examined further.

Fencing, particularly electric fencing, is widely used across South Africa for livestock and game ranching practices. Recent studies found that leopard tortoises (Stigmochelys pardalis) are more prone to dying from electrocution along electric fences than any other taxa. However, no studies have quantified tortoise mortality along non-electric fences or assessed the impact of fence structure. With South Africa being home to more tortoise species than anywhere else in the world, thus is a conservation concern. This study quantifies tortoise mortalities associated with electrified and non-electrified fences and relates these rates to fence structure (mesh or strand). Open veld transects are used as controls to estimate background mortality. This study also reports the distribution and abundance of different fence types along 2200 km of roads in the southeastern Karoo, allowing the cumulative impacts of different fence types to be estimated. All fence types had significantly higher tortoise mortalities than open veld transects. Leopard tortoise mortalities were significantly higher along electric fences than non-electric fences. Despite forming only approximately 4% of all roadside fencing, electric fences account for 56% of leopard tortoise mortalities. This study validates concern for increased electric fence use in the future and the potential impacts on leopard tortoises. When considering the current abundance of fence types and their associated mortalities, the total number of leopard tortoise mortalities along electric and non-electric fences are similar. Angulate tortoise (Chersina angulata) mortalities were significantly higher along mesh fences than strand fences, but did not differ between electric and non-electric fences. Angulate tortoises appear to wedge themselves in mesh fences and are unable to escape. This study highlights the current threat of non-electric fencing on tortoises as no similar findings have been reported. These additional tortoise mortalities should be considered alongside other emerging threats when questioning the longevity of these tortoise populations, not only in the Karoo, but globally. The implementation and practicality of previously suggested mitigation strategies are discussed and alternative mitigation strategies are suggested. This study concludes that raising of the electric strands is impractical and the implementation of rock aprons are ineffective. Live tortoises displayed active behavior when temperature was above 20 °C, thus thermostatic switches for electric fences could potentially reduce tortoise mortalities without compromising fences function.

In an ecological context, ‘flexibility’ refers to an animal’s ability to respond immediately to environmental stimuli through physiological and behavioural adjustments. Specifically, primates exhibit a high degree of ecological flexibility, which allows them to persist through environmental changes that vary in duration and predictability. To cope with the variability of conditions within their habitats, baboons have evolved flexibility in ranging behaviour, social behaviour, and diet. Natural disasters are predicted to increase across the globe, and many parts of the world are experiencing longer wildfire seasons and higher wildfire frequencies than ever before. The aim of this study is to use an existing data set to assess how baboons responded, behaviourally and physiologically, to an extensive wildfire. I compare home range use, activity budgets, faecal glucocorticoid concentrations, and urinary C-peptide concentrations three months after the fire to the same three months in the previous year for the same 16 adult females. In the months following the fire, the baboons had a larger spatial range compared to the same months in the year prior. The additional area incorporated unburnt areas into their home range, which were preferentially used over burnt areas. Behavioural adjustments included notably less time spent engaging in social behaviours than in the year prior. Perhaps most surprisingly, postfire physiological indicators did not suggest high levels of psychological, energetic, or nutritional stress, as glucocorticoid concentrations were significantly lower post-fire compared to the year prior, while C-peptide concentrations were not significantly different between the two periods. The troop appears to have benefited from a surfeit of exotic pine seeds that were released by pine trees as a result of the fire. This unexpected nutritional windfall, in addition to the inclusion of vineyards within their ranging patterns, may explain why there were no physiological indicators of nutritional stress despite the loss of most above ground biomass. Despite suffering the loss of 12 troop members in the fire and injury to a further 12 individuals, adult females in the Tokai troop were able to adjust to a severe and extensive change to their home range. Although primate ecological flexibility has been widely documented, this is the first study to explore the behavioural and physiological responses of baboons to extensive habitat changes resulting from a wildfire, and the potential implications for the management of wildlife on the urban edge.

No description available.

Within South Africa martial eagles reporting rates have decreased by almost 60% over the last two decades. Similar declines have also been reported within Kruger National Park (KNP), which is regarded as a stronghold for this species. Declines within KNP have been attributed to the low productivity rates. As apex predators, marital eagles are considered to be good indicators of ecosystem health, being sensitive to the cumulative effects of disturbance down the food chain. Changes in the breeding performance of martial eagles may therefore indicate broader environmental change within the ecosystem. In this study, we aim to explore which environmental variables (e.g. climate, land cover, tree cover, fire and elephant abundance) within each territory correlated with martial eagle breeding performance in the hope that we may better understand which variables affect martial eagles breeding performance and whether these may have changed over time to cause the low levels of fecundity presently seen within KNP. We found that breeding productivity (young per territorial pair) was positively influenced by higher precipitation and Normalized Difference Vegetation Index (NDVI) and negatively impacted by high temperatures during the previous year. Breeding rate (breeding attempt per territorial pair) appeared to be negatively influenced by higher tree cover within 6 km of the nest site. Nesting success (outcome of a breeding attempt) was correlated with higher NDVI and lower relative levels of precipitation during the previous year. Using longer term climatic data and the relationship between climate in the previous year and productivity, (the variable which directly relates to annual fecundity), we hindcast the predicted productivity over the last three decades (2018-1986) to explore whether change in climate conditions (precipitation, temperature and NDVI) might reveal declines in productivity. No such declines were predicted, thus, our results do not explain why productivity has declined within KNP.

No description available.

Livestock grazing is a key form of land-use around the world. Sustained, heavy grazing pressure, however, changes the vegetation structure of arid and semi-arid regions, often resulting in the local extinction of perennial, palatable species. It also causes changes in species composition through its impact on the recruitment of palatable and unpalatable rangeland species. Fence-line contrast studies are often used as natural experiments, since they contrast the long-term impact of herbivory between two different land tenure regimes and grazing intensities. This study used a fence-line contrast approach to investigate the long-term impact of high grazing pressure at a site in Namaqualand, South Africa. Forty pairs of permanently marked plots, separated by a fence (with communal grazing land on one side and commercial rangelands on the other) were established in 1996 to study the long term impacts of livestock grazing. Vegetation structure and composition of the plots were analysed in 1996 and 2006. The plots were resurveyed in 2016 as part of an on-going monitoring programme in the area. The main objective of this study was to investigate changes in the vegetation structure between the overgrazed communal rangelands and the relatively lightly grazed commercial rangelands over the 20 year period. All species in the paired plots were identified and assigned to 10 growth forms based on their height and life histories (e.g. annuals, perennials, geophytes). Differences in the average % cover as well as the number of species in each of the growth forms were compared across treatments. Differences in shrub volume, mean number of adults and the number of seedlings for each of five key indicator perennial shrub species between treatments and over time were also assessed. The five-indicator species covered a range of palatabilities from unpalatable and semi-toxic (Galenia africana), moderately palatable (Ruschia robusta, Eriocephalus microcephalus) and highly palatable (Tripteris sinuatum, Pentzia incana). Monthly rainfall totals and livestock grazing pressure for locations on the communal side of the fence, recorded by an on-site assistant, were also related to the changes recorded in rangeland composition over the study period. Results indicated that there was a decline in total vegetation cover in both commercial and communal rangelands in 2016 relative to the two earlier sampling periods. The patterns observed appeared to have been influenced strongly by the reduction in annual plant cover which was especially noticeable on communal rangelands. This in turn was probably as a result of the low rainfall experienced in the seven months prior to the 2016 sampling period. The number of species in the remaining growth forms did not differ between treatments and over time. Galenia africana had the largest volume of the perennial shrub species although considerable variation exists between treatment and years. The average number of individuals of mature G. africana shrubs was significantly greater in the communal plots at all time steps. The relative patterns of abundance of the different growth forms between land use treatments were maintained across sampling periods. Continuous heavy grazing over long periods in spatially constrained grazing systems changes the vegetation from being perennial to annual-dominated. This is analogous to switching from a predictable equilibrium system with forage reserve being transferred from one year to the next to one driven more directly by seasonal rainfall. Such rangelands are more characteristic of disequilibrium systems which are more unpredictable in terms of forage supply and livestock production potential. Vulnerable people who are not buffered from economic shocks will be more severely affected by the variability in forage supply for their livestock. The impact of sustained heavy grazing over long periods of time, therefore, has important consequences for people's livelihoods.

Many species in a wide variety of taxonomic groups have shown shifts in their distribution ranges in recent decades. Rapidly changing distributions may lead to novel biotic interactions between species that have not historically interacted. As generalist predators, corvids are a potential threat to other species in areas where they have recently colonized or where their numbers have increased. Tortoise species appear to be one taxonomic group that may potentially suffer serious negative effects from increased corvid abundance. One species of corvid which has shown a significant range increase in the last two decades in western South Africa is the Pied Crow (Corvus albus). In conjunction with this expansion have come observed accounts of large numbers of tortoises being found depredated under Pied Crow nests, raising concerns over their impact on tortoises in these areas. Southern Africa has the richest biodiversity of tortoises in the world and a high rate of endemism. The endemic species are mainly restricted to the Cape region, where the genera Chersina, Homopus and Psammobates have their evolutionary centre. In this thesis, I explore how widespread tortoise predation by Pied Crows was during the crow's breeding season. I aimed to quantify the proportion of Pied Crow pairs that provision tortoise to their chicks and the numbers being depredated, as well as the species of tortoises involved. During the 2016 breeding season, I monitored 125 active Pied Crow nests in western South Africa. For the majority of these nests (n=93) there was no evidence for any tortoise predation. For the 32 pairs, where predation was recorded, I found that 15 pairs depredated ≤1 tortoise – week, five pairs depredated depredated between 1 and 2 tortoise–week , and 12 pairs depredated >2 tortoises–week. The tortoises prey remains found depredated depredated under Pied Crow nests had an average straight carapace length of 5.57 cm (range 3.5 cm - 9.8 cm) and 91% of them were Angulate Tortoises. Crows favour smaller tortoises with impacts for smaller species, or younger age classes. I also explored whether any environmental variables explained probability of tortoise predation or predation rates. Environmental variables examined included weather variables, land cover types, distances to roads and primary productivity values, and for a subset of nests the abundance of tortoises counted from transects. Although predation rate showed spatial variation among the study areas with most predation occurring in arid areas with high mean temperatures and low rainfall, no single environmental variable successfully predicted the variation in spatial predation.

Cape gannets (Morus capensis) are one of the dominant seabirds in the Benguela current ecosystem and feed mainly on sardines (Sardinops sagax) and anchovy (Engraulis encrasicolus). Starting in the late 1990s the distribution of these fish shifted from the west coast of South Africa to the south-east coast. This has resulted in gannets on the west coast feeding extensively on fishery wastes, which slows the growth of chicks and decreases their fledging mass. I compared the foraging ecology, diet and body condition of adult Cape gannets from two colonies, one where individuals have been feeding on fishery wastes (hake) for several years (Malgas Island; west coast) and the other where individuals feed on natural prey (Bird Island; south coast). In October and November 2009, through the use of GPS loggers I compared the foraging behaviour of birds from the two colonies. I compared the diet of gannets at the two colonies, using stomach contents samples and an isotopic mixing model using stable isotope ratios of carbon and nitrogen in blood, feathers and potential prey. I also compared the body condition of adults by measuring pectoral muscle thickness and other morphological parameters. These results were analysed with data from a concurrent hydro-acoustic survey of the distribution and abundance of pelagic fish along the coast of South Africa. The hydro-acoustic survey showed that more than half of the sardine and anchovy stocks were present on the west coast for the first time in several years but that the overall biomass of these two species remained low in the southern Benguela. Stomach samples and isotopic analysis of blood showed that gannets at both colonies fed mainly on sardines during the study period. Long-term diet estimates from feather isotopes suggest that there was little hake in the diet of birds at Malgas Island, despite the direct diet samples showing that hake and saury dominated the diet over the preceding 10 months. This could be due to insufficient prey sampling or the diet samples not being representative of the gannet population as a whole. Gannets from Bird Island made longer foraging trips and flew further from their colony than did those from Malgas Island. Individuals from this colony had slightly greater pectoral muscle thicknesses and body masses (after controlling for size) than those from Bird Island, but 4 this was not significant. Despite gannets from Malgas Island relying on fishery wastes for a number of years, there has been little effect on body condition among breeding birds when compared with Bird Island gannets feeding on pelagic fish. Two possible reasons for this are that (1) when feeding on fishery wastes, adults decrease their reproductive effort to preserve body condition or (2) gannets on the west coast have regained body mass and pectoral muscle rapidly since the local recovery of sardines. It is likely that the gannets from Bird Island have greater foraging costs due to intra-specific competition for food as the colony has increased five-fold in size over the last 50 years. However, chick growth and adult body condition have been affected only marginally. Despite the presence of sardine and anchovy on the west coast, it is likely that Cape gannets are food limited, especially since there is also a strong spatio-temporal overlap of gannet foraging with the large commercial purse-seine fishery. Better spatial management of this fishery is necessary to ensure the persistence of seabirds and other top predators in the southern Benguela.

Bibliography: leaves 43-49. / Wildlife populations in southern Africa are increasingly forced into smaller areas by the demand for agricultural and residential land, and many are now restricted by protective fences. Although numerous studies have focused on the impacts of elephants and other browsers on vegetation in large, open areas, less is known of their effects in restricted areas. The woody vegetation in Ithala Game Reserve, a fenced conservation area of almost 30 000 ha, was monitored annually from 1992 to 2000 to assess the impact of browsers on vegetation structure and composition. Three categories of tree were identified: those declining in abundance (e.g. Aloe marlothii and A. davyi), those increasing in abundance (e.g. Seolopia zeyheri and Euclea erispa), and those with stable populations (e.g. Rhus lucida and Gymnosporia buxifolia).