Browsing by Author "Zungu, Manqoba Moses."

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Aspects of fruit digestion and selection in selected Southern African avain frugivores.
(2014) Zungu, Manqoba Moses.; Downs, Colleen Thelma.
Fruit-frugivore interactions play a central in maintaining the structure and diversity of ecosystems through their effects on seed dispersal. Because fruit selection and thus fruit removal represents the first stage in the seed dispersal process, understanding factors affecting fruit selection can play an important role in the formulation of sound conservation efforts especially light of the on-going habitat change. However, to date, the research is inconclusive as to factors affecting fruit selection as results have revealed inconsistent and controversial with a huge variation in fruit selection patterns between species and within individuals of the same species. The huge inter- and intra-specific variation in fruit selection patterns precludes any generalizations on fruit selection notwithstanding the research effort addressing the issue. One factor that could be attributed to this pattern is that most studies on fruit selection patterns in frugivorous birds have studied fruit attributes or physiological adaptations of frugivores to fruits in isolation. Because fruit profitability is affected by both pre- and post-ingestional factors, studying these factors in isolation deprives us of fresh insights into the fruit-frugivore interaction. Therefore by relating the physiological aspects of frugivores to fruit characteristics, this study aims to provide a link between the physiology of birds and their feeding ecology. Cape white-eyes (Zosterops virens), red-winged starlings (Onychognathus morio) and speckled mousebirds (Colius striatus) were used for this study. In the first part of this thesis, transit times and digestive efficiencies of birds fed equicaloric glucose and sucrose artificial fruit diets of varying concentrations were determined. Three concentrations were used: low (6.6%), medium (12.4%) and high (22%). Digesta transit times of birds increased with an increase in concentration for all diets but were generally higher on glucose diets. This finding has been widely reported in other similar studies. The increase in digesta transit times with an increase in sugar concentration may be due to high nutrient density on high concentration diets which require a longer processing time. Intake rates, on the other hand, decreased with an increase in sugar concentration. The inverse relationship between food intake and nutrient levels has often been attributed to compensatory feeding which posits that birds respond to nutrient dilution by increasing intake to allow a constant flux of assimilated energy. Indeed, speckled mousebirds and Cape white-eyes maintained a constant assimilated energy intake on sucrose diets by modulating food intake rates. The apparent assimilation efficiencies of glucose diets for all species were comparable and typical of those found in other frugivorous birds. However, red-winged starlings displayed low assimilation efficiencies for sucrose diets and lost significant body mass on all sucrose diets. The lack of significant sucrase activity in this species was attributed to this finding. This study showed the importance of digestive physiology in explaining fruit selection patterns in frugivorous birds. The second part of this thesis assessed the deterrence effects of tannins which are ubiquitous secondary compounds in plant material and are known for their ability to bind to protein which reduces nitrogen availability in the diet. In this study, birds were fed artificial fruit diets containing varying levels of tannins (0%, 2.5% and 5%) in paired choice tests. It was predicted that tannins would have no effect at low concentrations but at higher concentrations would act as deterrents although the levels at which they would become deterrents would differ among species. Red-winged starlings preferred the control diet, were indifferent to the medium tannin diet and were deterred by the high tannin diet whereas speckled mousebirds and Cape white-eyes were not deterred at all concentrations. The discrepancy in the results was attributed to differences in taste sensitivity, tolerance levels and detoxification mechanisms of secondary compounds between species. Occasional geophagy and consuming a broad diet were also implicated in producing the results obtained. Plant secondary compounds in fruits are diverse and their effects are similarly diverse and there is a possibility that different groups of secondary compounds generate disparate effects. Similar studies on other types of secondary compounds may thus contribute towards a broader understanding of the role of secondary compounds in mediating fruit-frugivore interactions. Overall, this study showed how diet affects ability to handle secondary compounds in fruits. The third part of this thesis addressed the influence of ethanol concentration on fruit selection in frugivorous birds. Because ethanol is ubiquitous in fruits and its concentration is positively correlated to fruit sugars, it has been suggested that because frugivores could use its odour to locate fruiting plants, they should select fruit with high ethanol concentrations. The aim of this study was to test this hypothesis by determining whether frugivorous birds show a preference for fruit laden with alcohol at levels equivalent to those of over-ripe fruits. Birds were provided with two artificial fruit diets in pairwise choice tests: an experimental diet containing 1% ethanol and an artificial fruit diet with no ethanol. For all species, there were no significant differences in the amount of fruit consumed between the two food types. These findings provided corroborating evidence to the suggestion that birds are unlikely to prefer over-ripe fruits compared to ripe fruits due to the negative impacts associated with ingesting ethanol at high concentrations. However, it could be possible that the lack of preference observed in this study was because the ethanol concentrations used were too low to be detected. Overall, this study suggests that at high concentrations, ethanol in fruits acts as a deterrent rather than an attractant. The last part of this thesis was conducted to determine the use of taste and olfaction by red-winged starlings in making foraging decisions. To determine whether they use taste in fruit selection, they were concurrently offered a control artificial fruit diet with another artificial fruit diet flavoured with different concentrations of ethanol and various fruit essences. To test whether they were able to use olfaction to locate food, they were provided with two choices: artificial fruit suspended over either banana and orange fruit essences and ethanol of varying concentrations or a control artificial fruit (without essence). It was hypothesized that (1) red-winged starlings have tasting ability which helps them in selecting fruits to feed on and that (2) red-winged starlings use olfaction to locate food. Results were consistent with the first hypothesis but inconsistent with the second one. Thus, red-winged starlings use taste when selecting fruits to feed on but do not use olfaction to locate fruit sources. The latter was unexpected because birds with olfactory bulb sizes similar to theirs exhibit advanced olfactory abilities. It was speculated that the lack of olfactory abilities in starlings could be attributed to the fact that this study was conducted outside of this species’ breeding season when olfactory abilities were likely to be lowest and also to that olfactory abilities may not have been important at the scale investigated in this study. Overall, the study showed that the sense of taste in birds plays an important role in making foraging decisions than currently appreciated. Overall, this thesis demonstrated the value of relating physiological attributes of frugivores to fruit attributes in acquiring deeper understanding of fruit-frugivore interactions. One particular advantage of the methodology employed in this study was that it controlled for covariance among fruit characters and also removed the confounding effects of as seed size and secondary compound composition. The shortcoming of this approach is related to the applicability of the results to the field conditions. Therefore an approach combining laboratory and field observations may produce results that may be important in informing us about how to manage our ecosystems.
Impacts of anthropogenic disturbance on persistence patterns of forest mammals in an urban-forest mosaic of eThekwini Municipality, Durban, South Africa.
(2018) Zungu, Manqoba Moses.; Downs, Colleen Thelma.; Kalle, Riddhika Vinod.; Tharmalingam, Ramesh.
The burgeoning human population size and the consequent land development pressures to meet its various needs has led to an unparalleled increase in the rates at which natural environments are converted for anthropogenic purposes. Among the major drivers of landscape modification by humans, urbanisation is arguably the most damaging, persistent and rapidly expanding across the globe. With the expansion of urbanisation, an increasing proportion of global biodiversity will be affected. The Ethekwini Municipality Area (EMA) is an urbanised landscape with high levels of biodiversity in South Africa. However, this area has a relatively large human population (~3.5 million), most of which is poor. Furthermore, it is located within a region (KwaZulu-Natal) undergoing rapid landscape changes. High development pressures, unauthorised development practices, conflicting governance systems and the preponderance of development priorities over environmental concerns has subjected most of the EMA to human activity. Considering these pressures, it is important to understand how wildlife adapt and persist in this human dominated landscape in order to guide conservation action. The aim of this study was to assess the impacts of anthropogenic disturbance on persistence patterns of forest mammals (excluding bats) in an urban-forest mosaic in the EMA, Durban, South Africa. The objectives were to: (1) determine factors affecting the occupancy of forest mammals; (2) determine the effects of landscape context on mammalian richness; (3) determine the effects of patch attributes and species’ ecological and life-history traits on nestedness patterns and (4) determine the effects of anthropogenic disturbance and abiotic factors on activity patterns and temporal niche overlap of mammals. Between May–September 2016 and December 2016–April 2017, mammalian surveys were conducted in forest patches within the study area using remote-triggered camera traps. Furthermore, data on vegetation structure at each camera trap location was recorded in order to better understand the habitat requirements of species. The results showed varying responses of mammals to landscape and habitat structural variables. The blue duiker (Philantomba monticola), bushbuck (Tragelaphus scriptus), bushpig (Potamochoerus larvatus), and Cape porcupine (Hystrix africaeustralis) were negatively affected by the loss and degradation of forest habitat and the increase in matrix development intensity whereas the large-spotted genet (Genetta tigrina) and vervet monkey (Chlorocebus pygerythrus) were relatively unaffected by such changes. Among habitat variables, an intact undergrowth and a high density of large trees were found to be important for the occurrence of many species found in this area as they provide sufficient breeding, roosting and browsing resources for specialist species that respond negatively to urban development. The results also demonstrated the importance of habitat area and its spatial configuration to the occurrence and persistence of mammals in this area. Patches that supported a high diversity of mammals were significantly larger, closer together, more contiguous and less separated by roads and urban development than patches that supported fewer species. The mammalian assemblage in the EMA was found to be significantly nested, with nestedness patterns related to patch size and isolation. This suggested that both the ability of species to persist on patches of various sizes and the ability to move to patches with different degrees of isolation affects the distribution and abundance of mammals in this area. Ecological specialists were found to be under more severe threat from further loss of forest habitat, which will likely threaten the long-term ecosystem functioning of forest habitat. When the activity patterns of species in the EMA were compared with activity patterns of the same species occurring in a less-disturbed landscape (Isimangaliso Wetland Park), no significant shifts in activity patterns were observed for most species except for common duiker (Sylvicapra grimmia), vervet monkey and Cape porcupine. Furthermore, there was only partial support for higher temporal overlap in activity patterns of ecologically similar species in the highly-disturbed EMA. Overall, the results presented in this thesis have provided insights into the persistence abilities of mammal species found in the EMA. The results have also provided basic ecological information on poorly known taxa, which will advance our understanding of their ecology locally and regionally. To ensure the continued persistence of mammals in the EMA, conservation efforts should prioritise the prevention of further loss of habitat, particularly large tracts of contiguous habitat. Furthermore, measures aimed at improving matrix permeability (e.g. stepping stones or corridors) should be promoted. This will help in reducing the negative effects of roads, which will ultimately increase landscape connectivity. Nevertheless, this is a metropolitan area with high development pressures, which are expected to increase even further in the future given the rapid population growth rate and the need to provide basic services to the people. Therefore, town planners, land owners, ecologists, and other decision makers need to consider the whole landscape, including the matrix, in the planning phase of future development projects in this area in order to minimise potentially negative effects on biodiversity.
The influence of the conservation of forests and public attitudes on the persistence of African crowned eagles in the mosaic of eThekwini Municipality, KwaZulu Natal, South Africa.
(2022) Maseko, Mfundo Sibongakonke Terrance.; Downs, Colleen Thelma.; Zungu, Manqoba Moses.
Abstract available in PDF.
Role and effects of wild southern African ungulates on seed dispersal of selected alien invasive plants.
(2021) Msweli, Lindelwa Sibongakonke.; Downs, Colleen Thelma.; Zungu, Manqoba Moses.
Abstract available in PDF.