Browsing by Author "Wilson, Amy-Leigh."

Now showing 1 - 2 of 2

Aspects of the ecology of Cape porcupines on farmlands, peri-urban and suburban areas in KwaZulu-Natal, South Africa.
(2018) Ngcobo, Samukelisiwe Princess.; Downs, Colleen Thelma.; Wilson, Amy-Leigh.
The unprecedented changes in the environmental and ecological processes of the biosphere have led some to believe that we have transitioned into a new geological era from the Holocene. This current era is known as the Anthropocene epoch, termed as such due to the unprecedented human-induced environmental change. Humans have dominated global changes in the environment and climate through the conversion of natural land-use systems into anthropogenic landscapes dominated by agriculture, urban and industrial development. The conversion and destruction of natural habitats into anthropogenic ones have caused shifts in ecosystem functions, and ultimately this has dire consequences for biological diversity globally. Although many species have gone extinct due to anthropogenic land-use changes, some have persisted and thrive within human-dominated landscapes. These species have adapted well to these landscapes, to the point whereby they have modified their behaviour to exploit anthropogenic resources, and increase in numbers. However, the expansion of human land-use into historically wildlands means that wildlife and humans will increasingly interact with one another. This is cause for concern, particularly with the projection of future anthropogenic land-use expansion and intensification. As a result, there is need to research how wildlife in human-dominated landscapes adapt and how their survival will influence human-wildlife interaction in the future. Cape porcupines, Hystrix africaeaustralis, are one of those species which have benefited from anthropogenic change of the landscape. However, due to their effectiveness in exploiting anthropogenic food and shelter resources, they have been perceived as problematic. This has led to their persecutions in certain areas, particularly within agricultural systems. But they are also becoming increasingly problematic also in suburbia. Therefore, as motivation for this study, we aim to investigate the spatial ecology of Cape porcupines in human-dominated landscapes of farmland and urban areas. This is because there is very little information on their space use and the research on Cape porcupines is outdated. Consequently, due to their potential to become conflict-causing, there is urgency to determine their spatial ecology and contribute knowledge towards their conservation and management in these landscapes. Therefore, Cape porcupine home range and habitat use along a land-use gradient were investigated. A total of fifteen individual Cape porcupines were captured and fitted with Global Positioning System (GPS) collar transmitters in farmlands of Fort Nottingham, a peri-urban estate near Howick, and in a suburban estate in Ballito, in KwaZulu-Natal, South Africa. Data obtained from the GPS transmitters were used to estimate Cape porcupine home ranges using the Kernel Density Estimator (KDE) (Chapter 2). Overall estimated Cape porcupine home ranges were very small (n = 9, mean ± SE: 39.37 ± 6.33 ha) compared with other Hystrix porcupines. Farmland Cape porcupine home ranges (24.57 ha) were the smallest relative to the peri-urban (34.61 ha) and suburban areas (45.18 ha). These results were as expected, since it has been revealed that porcupine home ranges are determined by forage availability. Consequently, these human-dominated habitats have anthropogenic food resources that are constant relative to natural resources. This means that the expansion of human-dominated landscapes will result in the contraction of Cape porcupine home ranges as they benefit from anthropogenic resources. With the aid of the radio-telemetry data, we also determined Cape porcupine habitat use in the farmland, peri-urban and suburban areas, in KwaZulu-Natal, South Africa (Chapter 3). Habitat use of Cape porcupines were investigated at the landscape-scale (2nd order of selection) and the home range-scale (3rd order of selection). Habitat use of Cape porcupines varied at the two-levels of selection, and individual Cape porcupines utilized different habitats, but generally selected the forest with bushland habitat above other habitats. We thought Cape porcupine habitat use would be determined by habitats dominated by anthropogenic food resources (crops and gardens). However, Cape porcupines utilized natural food resources although they lived in human-dominated landscapes. Their habitat use was determined by the presence of forest with bushland habitat, and to a less extent by croplands or residential gardens. This means that at this point, Cape porcupines opportunistically utilized anthropogenic food resources according to their availability. However, these results should be interpreted with caution since the study duration was limited by battery life of the GPS transmitters (~ 5 months). This study revealed that Cape porcupine showed individual variation in ranging patterns and habitat use which were likely influenced by forage availability. In addition, Cape porcupines shifted their spatial behaviour depending on the landscape they inhabited. Therefore, the behavioural flexibility of Cape porcupines enabled them to adapt to anthropogenic changing land-use and successfully persist there.
Aspects of the thermal physiology and fruit digestion of Knysna (Tauraco Corythaix) and Purple-crested (Gallirex porphyrelophus)
(2010) Wilson, Amy-Leigh.; Downs, Colleen Thelma.
Chapter 2: Avian frugivores have been somewhat poorly studied with regards to the effects that different fruit sugar types and concentrations have on their digestive efficiencies. Digestion of sugars in equicaloric and equimolar artificial fruit of different sugar types at varying concentrations and molarities were therefore investigated in two relatively large South African frugivores, the Knysna (Tauraco corythaix) and the Purple-crested (Gallirex porphyreolophus) Turaco. Artificial fruits of 6.6, 12.4 and 22% sucrose and glucose respectively and artificial fruits of 0.42, 0.83 and 1.66 mol L-1 sucrose and glucose respectively were used to determine daily food and energy intake, digestive efficiencies and digestive transit times. Digestive transit times of both Turaco species were slower with an increase in sugar concentration and molarity, irrespective of sugar type. Food intake of both Turaco species increased with decreasing concentration and molarity, irrespective of sugar type suggesting compensatory mechanisms for energy requirements. Apparent assimilation efficiencies of both Turaco species ranged from 61.4-90.0% and 60.2-92.4% for equicaloric and equimolar artificial fruit diets respectively. Consequently these two frugivores appear to be tolerant of sugar type and would be expected to select fruits based on energy yields. Future studies of the composition of indigenous forest fruit sugars may give insight into food preferences of the Turaco species and their role as potential seed dispersers of fruiting tree species. Chapter 3: The effects that different fruit sugar types and concentrations have on food preferences of avian frugivores have been relatively poorly studied. Although it has been recently advocated that preference is based on equicaloric energy it is also important to note whether preferences change as energy content changes. Therefore, sugar preferences of equicaloric and equimolar artificial fruit of different sugar types at varying concentrations and molarities were investigated in two relatively large South African frugivores, Knysna (Tauraco corythaix) and Purple-crested (Gallirex porphyreolophus) Turacos. Artificial fruits of 6.6, 12.4 and 22% sucrose and glucose respectively and artificial fruits of 0.42, 0.83 and 1.66 mol L-1 sucrose and glucose respectively were used to determine sugar preferences. Knysna Turacos preferred the sucrose to the glucose equicaloric artificial fruit diet at low concentrations whereas Purple-crested Turacos showed no preference for either diet. Both Turacos species preferred the sucrose equimolar artificial fruit diet to the glucose at low concentrations. At high concentrations neither species showed a preference for either equicaloric or equimolar artificial fruit diets. This suggests that energy requirements influence food preferences more than sugar type and that birds will select fruit that is higher in energy irrespective of sugar type. This complements an earlier study on digestion of sugars at varying concentrations of differing equicaloric and equimolar artificial fruit sugar types. It again emphasizes the need for future studies looking at the composition of indigenous forest fruit sugars in order to obtain insight into the role of these avian frugivores as potential seed dispersers of fruiting tree species. Chapter 4: Avian frugivores may select fruit based on their seed loads and pulp to seed ratios and this may have important implications for their role as seed dispersal agents. Consequently the effect of different seed packaging was investigated in two relatively large South African frugivores, Knysna (Tauraco corythaix) and Purple-crested (Gallirex porphyreolophus) Turacos. Small-seeded artificial fruits containing on average five black plastic beads (2.24 mm diameter) and large-seeded artificial fruits containing one average one single black plastic bead (3.85 mm diameter) were used to investigate transit rates and food preference. Total seed volume in the two fruits was on average approximately equal (29.42 mm3 and 29.88 mm3 for small- and large-seeded fruits, respectively). Bead transit rates ranged from 38-45 min for Knysna Turacos and 36-50 min for Purple-crested Turacos with faster transit rates on the small-seeded diet. Pulp transit rates ranged from 25-39 min for Purple-crested Turacos and 34-40 min for Knysna Turacos. Purple-crested Turacos had significantly shorter pulp transit rates on the large-seeded than the small-seeded diet whereas Knysna Turacos had no significant difference between diets. Knysna Turacos preferred the small-seeded to the large-seeded artificial fruits whereas Purple-crested Turacos showed no preference for either diet. Further studies on avian dispersers will contribute to a greater understanding of their evolutionary relationship with fruiting plants. In particular, future studies establishing suitable seed sizes and volumes for use in determining the effect of seed packaging on larger birds are required as well as studies looking at seed packaging of indigenous forest fruit and the effects of seed packaging on digestion and food preference in indigenous avian frugivores may give insight into the role of avian frugivores as fruit consumers and seed dispersers. Chapter 5: Fleshy-fruited plants and frugivores share a mutualistic relationship with plants offering the frugivores a reward of fleshy fruit pulp in order to disperse their seeds. In return frugivores receive a food source and consequently a source of energy. However all fruits are not equal in terms of available energy and consequently the digestion efficiency of six indigenous tree species was investigated in an avian frugivore, the Knysna Turaco (Tauraco corythaix). It was predicted that the Turacos would process these indigenous fruits efficiently and have fast transit rates and high intake rates irrespective of species. Fruits were fed to the Turacos in separate trials to determine daily food and energy intake, digestive efficiencies and digestive transit times. Digestive transit times of Knysna Turacos (c. 12-28 min) fall within the range of published examples for other frugivorous birds. Apparent assimilation efficiencies of the Turacos ranged from c. 15-84% and were generally lower than those observed in other avian frugivores. Future studies looking at the nutritional composition of indigenous forest fruit may provide insight into the Knysna Turacos digestive efficiency and consequently their food preferences and role as potential seed dispersers of fruiting tree species. Chapter 6: Seed dispersal plays an important role in the persistence, regeneration and maintenance of plant communities. It is therefore not surprising that much attention has been paid to the germination potential of seeds ingested by frugivorous animals. Consequently the aim of this study was to determine what effect ingestion of seeds by Knysna Turacos (Tauraco corythaix) has on the germination rate and germination percentage of indigenous South African tree species. Fruits from twelve tree species were fed to the Turacos in separate trials and seed retention times were determined as it has been suggested that a longer seed retention time may increase germination rates. At the end of each trial, seeds were extracted from excreta of individual birds and planted in trays containing potting soil. Germination was recorded daily until 14 days post of no germination. Knysna Turacos seed retention times were in the range of those obtained by other studies with Ficus sur seeds having the fastest retention times (12.4 ± 0.8 min) and Celtis africana the slowest (34.6 ± 5.6 min). Mean percentage germination of ingested seeds was not significantly different to pulp removed and whole fruit seeds indicating that ingestion by Knysna Turacos did not enhance percentage germination through either seed coat abrasion or pulp removal. Seed ingestion by Knysna Turacos did not influence the rate at which seeds germinated in 75 % of the tree species while it did for ingested F. lutea, F. natalensis and F. sur seeds which germinated significantly sooner than whole fruit seeds. Future studies relating the composition of indigenous forest fruits to food preferences of Knysna Turacos may give insight into their role as potential seed dispersers of indigenous fruiting tree species. Chapter 7: Frugivorous animals play a major role in dispersing tropical, and to a lesser extent, temperate tree species. In order to attract potential seed dispersers, plants generally offer a reward of fleshy fruit pulp. Criteria for fruit choice by avian frugivores are influenced by a number of non-nutritive (e.g. fruit size and colour) factors; and nutritional composition of the fruit. There is a paucity of nutritional composition and other fruit trait data of indigenous South African fruit. This information is necessary in order to determine which frugivores are likely to ingest which fruits and consequently act as potential seed dispersal agents. This information would provide us with an understanding of the inter-relationships between indigenous fruit and frugivores in South Africa. Consequently nutritional composition was investigated in various indigenous fruit species that avian frugivores feed on. Fruits were collected from 38 indigenous tree species found in KwaZulu-Natal afromontane and coastal forests. Pulp was freeze-dried to constant mass and then analyzed for sugar, lipid and protein content; and for water content determination. Fruit width in this study ranged from 4 mm (Searsia rehmanniana and Trema orientalis) to 40 mm (Annona senegalensis, Ficus sur and Xylotheca kraussiana). Of the fruits examined in this study 29% were black and 43% red when ripe. Most (84%) fruit species analysed for sugar content were hexose dominant with 50% being fructose and 34% being glucose dominant. Only 16% of the fruit species analysed were sucrose dominant. Fruits in this study were generally observed to be high (mean: 68.1 ± 3.3%; n = 30) in water content; and low in protein and lipid content respectively (mean: 8.2 ± 0.5%; 9.3 ± 2.2%; n = 30) indicating that these fruits species could be considered as nutrient-dilute. Future studies need to determine the nutritional composition of the remaining indigenous South Africa fruit in order to develop a comprehensive database as well as examining non-nutritive factors. Together this information would play a key role in understanding fruit preferences and consequently seed dispersal and would therefore be useful in developing management plans for forest conservation. Chapter 8: Many seasonal thermoregulation studies have been conducted on Holarctic birds that live in predictable, highly seasonal climates with severe winters. However, relatively few studies have been conducted on their southern hemisphere Afrotropical counterparts that encounter less predictable climates with milder winters. These latter birds are expected to conserve energy in winter by down-regulating their metabolic rates. Therefore in this study, metabolic rate was measured during summer and winter in Knysna Turaco, Tauraco corythaix (Musophagiformes, Musophagidae) (c. 310 g), a non-passerine, in order to test whether there is energy conservation in winter. No overall significant differences in resting metabolic rates over a range of ambient temperatures were observed between winter and summer. However, whole-organism basal metabolic rates were 18.5 % higher (p = 0.005) in winter than in summer (210.83 ± 15.97 vs. 186.70 ± 10.52 O2 h-1). Knysna Turacos had broad thermoneutral zones ranging from 20-28 oC in winter and 10-30 oC in summer. These results suggest that Knysna Turacos show seasonal thermoregulatory responses that represent cold defense rather than energy conservation, which is contrary to what was expected. Keywords: sugar digestion, sugar preference, seed packaging, basal metabolic rate (BMR), resting metabolic rate (RMR), phenotypic flexibility, indigenous fruit, germination percentage, germination rate, fruit sugars, protein, lipids, fruit size, fruit colour, Knysna Turaco, Purple-crested Turaco.