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. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Degradation of forest environments in South Africa have greatly affected both the plants and animals that interact with these plants. It is therefore important to understand plant-animal interactions in forest ecosystems in an effort to develop strategies for forest conservation. Animal dispersal can assist in the restoration of forest plant diversity and consequently animal diversity. Wahlberg’s epauletted fruit bat (Epomophorus wahlbergi) occurs in the eastern part of South Africa and is known to feed on fruit, nectar, pollen and flowers. It is an important disperser of various indigenous and alien invasive forest fruit species. Little is known about the benefits these bats get from feeding on fruit. Furthermore, the buccal cavity and lingual adaptations of fruit bats in Southern Africa are unknown. This study investigated morphological and physiological adaptations for frugivory in E. wahlbergi. In particular, the palatal and lingual morphological structures of E. wahlbergi were examined by light microscopy and scanning electron microscopy. The results of this study showed that the morphological structures of tongue papillae in E. wahlbergi were similar to that of other fruit and nectar feeding bats. The structural arrangement of tongue papillae in E. wahlbergi probably allows food to move from the anterior part of the tongue and collect at the median line of the posterior part of the tongue, and thereafter move down to the pharynx. These bats had an elongated tongue, wide, flattened molar teeth, and a hard papillae structure observed on the upper palate at the posterior end of the buccal cavity. This papillae structure has not been described previously; and it appears that it is with this structure, together with the palatal ridges, and teeth that E. wahlbergi crushes fleshy fruit to extract the juices when feeding. Consequently palatal and lingual structures of E. wahlbergi showed morphological adaptations for efficiently feeding on fleshy fruit and nectar. South African indigenous and exotic fleshy fruits available to E. wahlbergi are found to be generally hexose dominant. These bats are suggested to have high glucose intake irrespective of sugar concentration to power their high energy demands due to flight. High glucose intake could result in increased blood plasma glucose levels which are detrimental to mammals of small body size. This study investigated the diel variations in blood plasma glucose concentrations of E. wahlbergi. Epomophorus wahlbergi’s blood plasma glucose concentration was lower (5.24 ± 0.38 mm ol/l) at 18h00 before feeding and increased during/after feeding (8.19 ± 1.24 mm ol/l), however bats appeared to regulate it within limits. Their range in concentrations was higher than the normal mammalian blood plasma glucose concentrations range. Consequently these bats appear to regulate their blood plasma glucose concentration although at a range higher than normal mammalian levels and thus reduce the negative consequences associated with hyperglycemia. The data obtained provide a baseline for comparison with free-ranging E. wahlbergi. Proteins are important in a diet to provide the required nitrogen and amino acids necessary for maintaining body tissues. Fruits, however, appear to have energy-rich but protein-limited foods. Frugivores that feed exclusively on fruit may therefore have difficulties in maintaining their protein requirements since fruits are generally high in sugar content but low in protein content. The importance of protein in the diet of E. wahlbergi was determined by measuring diet intake at varying levels of protein in the laboratory. Epomophorus wahlbergi were offered equicaloric 15 % glucose solutions with varying protein concentrations (2.58, 5.68, 7.23 g soy protein/kg H2O) and a solution with no protein. This was repeated using 15 % sucrose instead of glucose solutions. Epomophorus wahlbergi’s volumetric intake of the respective glucose and sucrose solutions varied among individual bats, with total volumetric intake highest for the solution with no protein (control) and lowest at 2.58 g/kg soy protein concentration solution for glucose and 5.68 and 7.23 g/kg soy protein concentration for sucrose. These bats appeared to prefer sugar solutions without or low protein, and their daily protein intake was relatively low. This suggests they have low-protein requirements, and this relates to their characteristic low-protein fruit available in the wild. Feeding and digestive efficiency has been widely studied in frugivorous and/or nectarivorous birds but relatively few studies have been done on bats, particularly African bats. Feeding on a liquid nectar diet and fruit juices could cause physiological challenges for nectarivores and/or frugivores as they have to balance water and energy intake from this liquid diet. Mammalian kidneys have to eliminate salts and nitrogenous wastes, conserve water during water restriction as well as excrete it when ingested in excess. Morphological renal characters are known to be reliable indicators of urinary concentrating abilities in mammals. Short digesta residence time is a digestive trait that is known to be associated with frugivory and this may be a problem since digestive efficiency is a function of the length of digesta retention time. Histological sections of E. wahlbergi kidneys and small intestines were examined under microscopy to determine water regulation and specialization for sugar absorption respectively. Cortex and medulla length measurements were taken to calculate the medulla: cortex ratio (M/C) and the percent medullary thickness (PMT). The observed M/C ratio and PMT of E. wahlbergi is typical of a mesic species. Epomophorus wahlbergi feeds on a watery diet and does not need to concentrate urine; therefore the medulla and cortex were more or less the same size. Analysis of the histological sections showed that the kidney structure of these bats allows efficient water regulation in a mesic environment. The microvilli of E. wahlbergi intestine were relatively long with a large surface area thus serves the purpose for efficient digestion and absorption of sugars in these bats. Future studies need to be done to determine the mechanisms by which these bats regulate their blood plasma glucose levels, and also determine intake on a selection of fruit in order to broaden research to adaptation of these bats on low-protein diets. This study contributes to a greater understanding of the physiological and morphological mechanisms that may affect fruit intake and consequently dispersal. It will contribute to a greater understanding of plant-animal interactions in southern Africa. / Thesis (M.Sc.)-University of KwaZulu-Natal, Piertermaritzburg, 2012.