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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Revision of some dwarf chameleons (Sauria: Chamaeleonidae: Bradypodion) from eastern South Africa.

Raw, Lynn Roy Graham. 13 December 2013 (has links)
This dissertation has the object of re-examining the taxonomic status of the dwarf chameleons related to Bradypodion melanocephalum and Bradypodion caffrum from eastern South Africa. The historical context of previous taxonomic treatments is reviewed. The basis of the taxonomic interpretation was established after a review of available alternatives. Cladistic analysis is used to elucidate the relationships of the taxa. The number of separate taxa that can be distinguished has been increased by the revival of one previously described taxon, the discovery of heretofore unknown populations and by the detection of the composite nature of some of the previously described taxa. Diagnoses and descriptions of the taxa under review are provided along with a key to their identification. The geographic distribution of these Bradypodion taxa is reviewed in the context of present ecological parameters and in terms of the historical evolution of the study area. Comparison is made with the distributions of other taxa of plants. invertebrates and vertebrates occurring in the same general area. This appears to indicate a shared evolutionary history with a number of localised areas of endemicity. The conservation status of these Red Data Book and CITES-listed dwarf chameleons is discussed with discussion of threats and priorities for further action. The use of these dwarf chameleon species as indicators for the identification of endemic areas should have important implications for conservation strategies in eastern South Africa. This dissertation is not to be considered as a publication for the purposes of zoological nomenclature. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.
52

Sexual selection of multiple ornaments in the red-collared widowbird.

Pryke, Sarah R. 13 December 2013 (has links)
Although sexual selection often explains the evolution and maintenance of a single male ornament, it is unclear how the multicomponent nature of most sexual displays evolves. Theoretical models suggest that handicap signalling should converge on a single most informative quality indicator, whereas additional signals are more likely to be arbitrary Fisherian traits, amplifiers, or exploitations of receiver psychology. Despite the predictions that multiple handicap signals are unlikely to be stable, the male nuptial plumage of the highly polygynous (ca. 3, but up to 9 actively nesting females) red-collared widowbird Euplectes ardens comprises two classic quality-indicating avian ornaments (handicaps); a long graduated tail (22 cm) and a red carotenoid throat patch (collar). To investigate the evolution and maintenance of these handicaps in the red-collared widowbird, a population was studied in the Hilton district, KwaZulu-Natal, South Africa, where these small (males ca. 20 g) African weaverbirds (Ploeceidae) inhabit a grassy valley during the breeding season. Multivariate selection analyses, used to investigate net, direct and indirect female selection, demonstrated an unusually strong fitness effect of natural tail length (47%) on male reproductive success (the order and total number of nests acquired). There were no other effects of morphology, ectoparasite load, display rate, territory quality, tail asymmetry or collar measures (hue, brightness and size) on reproductive success, suggesting that females base their mate choice exclusively on only one handicap signal, extreme tail elongation. Although ignored in mate choice, there is strong evidence that the variable carotenoid collar (ranging from yellow to red) functions as a status or agonistic signal in male contest competition for territories. Compared to 'floating' males (that did not establish a territory in the area), resident males had a 60% larger and 23 nm 'redder' (longwave hue) collar. Model presentations also corroborated the status signalling function of the collar as territorial males were less aggressive towards conspecific models with intense collar displays, and males with greater carotenoid investment responded more aggressively to the models. In captive experiments, non-breeding brown males painted with red 'collars' dominated orange painted, control brown, novel blue collared and testosterone-implanted males in dyadic contests over food resources. In addition, experiments in the field demonstrated that males manipulated with larger and redder collars established and maintained territories in the area, whereas most males with small, orange or blackened collars failed to establish or retain territories. Thus the size and particularly redness of the costly carotenoid collar reliably signals male status and fighting ability in male contests. The unique negative phenotypic relationship between the expression of tail length and carotenoid pigmentation, suggests strong overlapping developmental costs (and allocation conflicts) between the two handicap ornaments. This tradeoff is predicted to be strongest between signals with the same or similar costs. Although current theory predicts that multiple handicaps should be evolutionary unstable, the coexistence of multiple costly ornaments in the red-collared widowbird is stable because of selection by different receivers, females and males (i.e., multiple receivers). / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2001.
53

The influence of gender on thermoregulation in pouched mice, Saccostomus campestris.

Mzilikazi, Nomakwezi. 19 December 2013 (has links)
Saccostomus campestris display sexual disparity in the use of summer daily torpor in response to energy stress. The hypothesis that males may compensate for a limited heterothermic capacity with lower normothermic body temperatures by maintaining lower resting metabolic rates relative to females was tested. Furthermore, the influence of testosterone on torpor incidence in males was investigated. Body temperature (T[b]) and oxygen consumption (VO₂) were measured at various ambient temperatures (Tₐ) and were compared between the sexes under food ad libitum and food restriction treatments. There were no significant differences in T[b] and VO₂ between sexes under food ad libitum treatment. Under food restriction there were pronounced sex differences in the employment of heterothermy. Females defended a lower setpoint T[b] for torpor (ca. 25°C), than males (ca. 29°C), and also employed torpor more frequently than males. Non-torpid males did, however show slight reductions in VO₂ under food restriction. The effect of testosterone on daily torpor was investigated by comparing minimum T[b]and torpor frequency of castrated mice implanted with testosterone-filled (experimental) and saline-filled (control) silastic capsules in response to food ad libitum and food restriction treatments. Testosterone inhibited torpor in males. The majority of control animals employed torpor under both food ad libitum and food restriction diets. It was concluded that although the animals were capable of shallow, summer torpor, it was confined to moderate ambient temperatures and was not used at low Tₐ's where several animals became pathologically hypothermic. Females derive energetic benefits from the use of torpor whereas males may partially compensate for their limited heterothennic capacity by a reduction in resting metabolic rates, accompanied by moderate reductions in body temperature during energetically stressful periods. The difference in the capacity for daily heterothenny between sexes was attributed to differences in their reproductive physiology. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.
54

Utilisation of low density vacuum zones by white rhinos in the Umfolozi Game Reserve.

Shrader, Adrian Morgan. 19 December 2013 (has links)
White rhinos in the Umfolozi Game Reserve (UGR) are managed with a 'Sink Management Policy' which utilises natural dispersal patterns of white rhinos from an area of high density (the core), to areas of low density (vacuum zones). This study was initiated to determine how white rhinos utilised the vacuum zones, as the management staff of the UGR felt that white rhinos were not dispersing into them but utilising them only as areas of trophic resources. Significantly different white rhino densities were established in the Makhamisa and Masinda vacuum zones by removing white rhinos from Masinda. Changes in the density of white rhinos were monitored and the age and sex compositions determined. No significant changes in the density of white rhino groups were recorded during the study, however, the density of individuals in Makhamisa increased significantly in the dry season, while the density in Masinda did not change. The reason for this increase could not be determined, however, the most likely explanation was that rhinos moved toward the Makhamisa study area in search of surface water which was present in the White Umfolozi River. During the dry season the water level in the Umfolozi River was low so the white rhinos where able to cross into the study area. However, owing to the above average rainfall, resources were not limited in either study area, and most likely in most of the reserve. Thus, it could not be determined why white rhinos would need to enter the Makhamisa study area. Changes in grass height, grass colour, and the availability of water in pans and streams were monitored throughout the study. The grassland community compositions of the two study areas were found not to be significantly different. The total utilisation of the different grassland communities by white rhinos during the study were determined for both study areas. White rhinos in the two study areas utilised the grassland communities in a similar pattern throughout the study. During the wet and dry seasons, white rhinos primarily foraged in the short grassland community (Panicum coloratum & Themeda-Urachloa), their staple grassland community, and were not observed to switch and start foraging in the tall grassland community (Themeda & Themeda-Panicum). their reserve community. White rhinos in both study areas were able to forage in their stable grassland community throughout the dry season because of the above average rainfall experienced during the study The results of the study suggest that white rhinos outside the study areas did not utilise the vacuum zones for trophic resources. However, as the study was conducted in a year with above average rainfall, these findings may not represent how white rhinos utilise the vacuum zones in years with average or below average rainfall. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1998.
55

Habitat use and feeding ecology of the roan antelope at Weenen Nature Reserve.

Taolo, Cyril Lebogang. 13 January 2014 (has links)
The roan antelope Hippotragus equinus equinus, is listed as endangered in the South African Red Data Book. A herd of nine roan were introduced to Weenen Nature Reserve (WNR) in 1988. The herd has since increased to sixteen animals. The aim of the study was to determine those habitat characteristics which influenced the preference or avoidance of the habitat types available at WNR. The extent to which the antelope's occurrence was correlated with certain habitat elements was determined. The roan preferred open woodland on gently undulating terrain. Themeda triandra was found to be the most common grass species in the diet of the roan. Cauline grass species such as Hyparrhenia spp. were avoided in the dry season. Dicots assumed greater importance in the diet in the dry season. Several management practices employed at the reserve were assessed to determine their influence on habitat use by the roan. These practices were not found to be incompatible with the goal of conserving roan antelope in the reserve. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.
56

The role of Anopheles arabiensis (Diptera: Culicidae) in malaria transmission and control in Gokwe and Binga districts, Zimbabwe..

Masendu, Hieronymo Takundwa. January 1996 (has links)
Opportunistic feeding behaviour and partial exophily make An. arabiensis much more difficult to control by indoor residual spraying than any other vector in the Afro-tropical region. The persistent malaria outbreaks in Zimbabwe despite decades of indoor house spraying prompted this investigation into the role of An. arabiensis in malaria transmission and assessment of the possible impact of this control measure. The study was conducted in the malaria endemic districts of Binga and Gokwe. An. gambiae complex mosquitoes were collected from artificial outdoor resting sites, and from human dwellings by i) daytime hut searches, ii) pyrethrum spray catches and iii) exit window traps. Mosquito components were processed to enable: i) the distinction of An. arabiensis from An. quadriannulatus and An. merus on the basis of the pale band at the junction of the hind leg 3/4 tarsomeres; ii) species identification and scoring of inversion polymorphism on the basis of the X chromosome and autosomes respectively; iii) the determination of blood meal sources using the Ouchterlony precipitin test; and iv) identification of An. gambiae s.l. using polymerase chain reaction (PCR) and enzyme electrophoresis techniques. Entomological assessment of residual spraying included determining: the vector resting densities indoors and outdoors, bioassay and insecticides susceptibility tests. Data were also collected on hut profiles, knowledge-attitudes-practices surveys, and household malaria prevalence . surveys. An. arabiensis and An. quadriannulatus were found in sympatry in Binga and Gokwe, and in addition, An. merus was found in Gokwe. Most species identifications were made using PCR; which was found to have 7.5% and 41.6% levels of error for An. arabiensis and An. quadriannulatus respectively, using the cytogenetic technique as benchmark. The pale band technique yielded > 80% correct identification for An. arabiensis but the extent of overlap in the pale band lengths between An. arabiensis and An. quadriannulatus renders the method unsuitable for distinguishing these two species. Inversions 2Rb and 3Ra were found floating in An. arabiensis, with 60% frequency in the former. The Wright's F statistic value of -0.0416 indicated an excess of heterozygotes, and a state of panmixis in the vector population. No significant differences were observed between 2Rb karyotypes in host choice. Human blood indices among indoor (0.82), exit trap (0.98) and outdoor resting (0.30) specimens suggested exophilic behaviour. This was corroborated by the high fed:gravid ratios of 6.8: 1 and 11.6: 1 in sprayed and non-sprayed dwellings respectively. This was worsened by a high feeder-survivor index (FSI) of 93 % among exit trap specimens. The susceptibility to deltamethrin coupled with residual efficacy nine weeks post-spray indicated the suitability of the insecticide. Rural dwellings were suitably built for spraying but had no mosquito proofing. Personal protective measures are hardly known; sleeping outdoors occurs in Siabuwa. While An. arabiensis bites humans indoors the partial exophily it exhibits is a threat to indoor residual insecticide spraying. An integrated malaria control approach is recommended. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.
57

Intersex in four South African racial groups in Durban.

Grace, Hatherley James. January 1970 (has links)
Chapter I The ontogeny of sex development is introduced and a definition of the intersexual state is given. A resume of intersexes recorded in South Africa is presented together with figures showing the increased demand for cytogenetic services in the country. The motivation for this study is discussed. Chapter II The biological concept of sex is outlined together with notes on the evolution of the dioecious state in animals. Thereafter a brief account of the normal and abnormal intersex states in invertebrates and vertebrates is given. Chapter III Examples of some of the abundant references to ambisexual individuals found in the classical literature, history and mythology are listed and the status of intersexes in modern society is discussed: it does not vary much from the times of ancient Greece and Rome. Chapter IV A summary of the events which led to the establishment of cytogenetics as an independent discipline is given. The discovery of nuclear sex dimorphism is noted and methods of investigation of intersexual patients are described. A detailed description is given of cytogenetic technical. "methods, ; and leads to a diagrammatic explanation of the differential diagnosis of intersexes. This is used as a basis for the classification and accordingly a simplified, unambiguous system is proposed and defended. The sources and numbers of pat~ ients recorded in this thesis are explained. Chapter V The sex chromatin is described in detail? with a description of the methods used for its demonstration and evaluation. A pilot study of normal women of the four races established that there is no inter-racial variation in chromatin frequency. Reasons are given for disregarding nuclear appendages as an accurate indication of 'sex '. Chapter VI Embryological stage s i n the development of the human urogenital tracts are recounted after considering the mechanisms of sex determination. Pathogenesis of intersexuality is considered briefly. Chapter VII Gonadal dysgenesis of the female, including Turner's syndrome and phenotypes of both male and female are presented. The classification, pathology, aetiological and cytogenetic factors are described. Illustrative case reports and extensive discussion of the syndrome are presented. Chapter VIII The Klinefelter syndrome occurs in males with supernumerary X chromosomes; a number of chromatin negative, hypogonadal conditions mimic the syndrome: they are described, with notes on the classification, pathology, aetiology and the cytogenetic features. A series of case reports demonstrate both chromatin positive and negative types. Special reference is made to the dermatoglyphic profiles which were discovered to differentiate the XY males into two groups. Chapter IX Three syndromes, the XXX, XYY and agonadism, were not encountered in this study and are consequently not discussed. Chapter X The adrenogenital syndrome has several distinctive signs which are mimicked by induced virilization; these are described and a number of case reports are presented to illustrate the syndromes. Chapter XI Male intersexes occur in several different forms: the classification of the group is explained and a distinction is made between intersexes and those with simple, or 'pseudo-intersexual', defects. The signs of the different syndromes are detailed, together with data concerning the aetiology and cytogenetics. A series of patients' case histories is used to illustrate the various syndromes. Chapter XII Idiopathic female intersexuality is defined and a short explanation of the classification is given. The signs found in this syndrome are detailed and a single case report, which is of exceptional interest because of severe masculinization and the formation of a phallic urethra, is presented. Chapter XIII Hermaphroditism is defined and the subgroups are explained. The variability of signs is discussed and details of anatomy and histology of the genital tract are given . A single hermaphrodite was encountered during the survey and the case is described. Three other patients, all infants, were suspected of being hermaphroditic but because gonadal biopsy was not undertaken they were discharged from hospital without a diagnosis having been made. Discussion of the aetiological mechanisms is presented and the need for early diagnosis and treatment is emphasized. Chapter XIV Some of the simple genital anomalies and somatic defects which resemble intersex are mentioned and are illustrated by attenuated case reports. Chapter XV The incidence of those intersexual conditions recognizable at birth by anatomical deformity is calculated from a total population of 21,000 live births recorded during the calendar year, 1969. The incidence was very low (1:7000) and does not permit analysis of inter-racial distribution. Prevalence is calculated from the number of new patients seen by the author during 1969 in Durban. Some interesting observations were made but the primary objective, to determine whether or not intersexuality is more prevalent in the Bantu than any other race, could not be answered with certainty because of the small number of patients. Hermaphroditism was shown not to be the most common type of intersex syndrome in the Bantu. Chapter XVI An outline is given of the normal dermatoglyphic features of the finger prints and palms. Some references of the patterns in Turner's and Klinefelter's syndromes are available from the literature and are compared with the profiles of patients from this series. A distinct dimorphism was found in chromatin negative hypogonadal males and was thought to distinguish between those with congenital or acquired pathology. Normal values for South Africans have not been established satisfactorily and the urgent need for this information is stressed. Chapter XVII A general discussion of the highlights of this study of the epidemiology, clinical presentation and cytogenetics of intersexuality is given and a number of conclusions are drawn . / Thesis (M.Sc.)-University of Natal, Durban, 1970.
58

The evolution of the house sparrow (Passer domesticus) in southern Africa.

Msimanga, Audrey Ottilia. January 2001 (has links)
The house sparrow, Passer domesticus, is one of the most successful invading bird species in the world. It was introduced to southern Africa around 1900 and has since spread through the region. Its dispersal was characterised by an initial slow phase followed by a rapid increase in the rate of spread. Following 50 years of slow spread, the rate of dispersal accelerated to over 80 km/year. The initial slow rate can be attributed to an Allee effect, defined as "a disproportionate reduction in reproduction below a threshold population density due to reduced probability of finding a mate". The rapid phase involved a combination of long-range jumps (leap-frogging dispersal) and diffusive movement over short distances. Dispersal was significantly faster along railway lines. Introduction of the house sparrow, Passer domesticus, to southern Africa involved unknown numbers of both the domesticus race of Europe and indicus of Asia, resulting in the establishment of a genetically diverse founder population along coastal South Africa. The birds have undergone significant differentiation since introduction about 100 years ago. Significant sexual size dimorphism was detected among southern African house sparrows, especially in flight structures. Males were larger than females in all characters except tarsus and claw length. Overall body size variation was clinaly ordered with a general increase in size with latitude in conformity with Bergmann's rule. Tarsus length also increased southwards, with the longest tarsi in birds of coastal sites in South Africa and the shortest in Zimbabwe. Patterns of variation in morphological characters paralleled climatic trends, especially minimum temperature and humidity. Beak size and shape of Zimbabwean birds appeared to be under the greatest influence of climatic factors. Shorter and more conicaly shaped beaks were selected for in females in Zimbabwe. Natural selection was modifying the morphological characters resulting in adaptive radiation in morphology of southern African populations. Few studies of microevolution (change in morphology over a short period) have been conducted in birds and none in invading bird species in the tropics. A founding population comprising both the Asian and the European races of the house sparrow, P. d. domesticus and P. d. indicus first arrived in Zimbabwe 30 years ago. Because of its recent introduction to Zimbabwe and because of its known potential for rapid adaptation and differentiation elsewhere in its new range, the house sparrow provided the ideal case study in microevolution in tropical Africa. Morphological differentiation in Zimbabwean populations of the house sparrow was analysed to determine temporal variation in local samples and the extent of variation from parent populations of Asia and Europe. Samples collected since arrival in Zimbabwe up to 1980 were compared with those collected from current populations in 1998/1999 to determine local changes over time. The Zimbabwean samples were then contrasted with samples from Asian and European populations to determine the extent of differentiation in the introduced birds of Zimbabwe. Zimbabwean populations had differentiated from their Asian parents in six of the seven morphological characters examined. The greatest differentiation was in beak size and shape for both males and females. Males developed larger beaks and shorter wings than the Asian birds and female beaks became more conical. A large proportion of the potential phenetic diversity of the founding population of both domesticus and indicus genes had been realised in Zimbabwe. / Thesis (M.Sc.)-University of Natal, Durban, 2001.
59

Feeding ecology and carrying capacity of a reintroduced pack of African wild dogs in a relatively small, fenced reserve.

Niemann, Sophie Mary. January 2010 (has links)
Reintroduction has been used successfully as a tool to restore declining populations of many threatened species. However, the lack of detailed evaluations of past reintroduction attempts has hindered a priori planning of management actions to achieve conservation goals. The metapopulation approach resulted in the most extensive and successful reintroduction efforts of the African wild dog (Lycaon pictus) in South Africa, but the approach was only recently evaluated by Gusset et al. (2008). For future reintroduction attempts to be successful on relatively small reserves, extensive evaluations are needed. Particular focus on feeding behaviour and impact on prey populations is essential to predict sustainability and carrying capacities in these areas for the African wild dog. A small reintroduced population of African wild dogs (pack number varying from 3 to 13 during the study period) were studied in the Karongwe Game reserve (79 km2) between January 2002 and January 2004. Fourteen prey species were identified: impala (Aepyceros melampus, 60 %) was the most dominant prey followed in descending order by bushbuck (Tragelaphus scriptus, 7.4 %), waterbuck (Kobus ellipsiprymnus, 4.9 %), warthog (Phacochoerus aethiopicus, 4.7 %), kudu (Tragelaphus strepsiceros, 4.4 %), and grey duiker (Sylvicapra grimmia, 4.4 %). Generally, prey were included in the diet in relation to abundance, and the dogs were not rate maximizing foragers but, unlike the findings of previous studies, were opportunistic feeders. The fences and angles in the fence, were used to assist hunting, but only for medium sized prey, impala and bushbuck, which were killed significantly more than expected along the fence line. A predictive prey preference model was then tested, but the model did not account for possible differences in feeding behaviours and prey preferences found in this, nor another study from the small Shambala Game Reserve. The model had limited accuracy as a predictive tool for proposed reintroductions into relatively small reserves. Models which can predict carrying capacity and minimum area requirements were also tested. Large variation and low numbers were predicted, which conflicted with social requirements needed for the survival of the population; further the models did not account for interspecific competition nor simultaneous depletion of prey by other guild predator. If the metapopulation approach is to continue to be successful and sustainable, more detailed evaluations of reintroductions of African wild dog on relatively small, fenced reserves are needed to determine the impact of these dogs on prey populations, and to determine if African wild dog feeding behaviour does differ for these areas in comparison to previously described open systems. With this information, more appropriate protocols regarding reintroduction and management can then be developed, thereby meeting one goal of management and conservation for the African wild dogs and their coexisting prey populations, and which can be used as a model for managing other large predators. / Thesis (M.Sc.)-University of KwaZulu-Natal, 2010.
60

Biodiversity of spiders (Araneae) in a savanna ecosystem and the processes that influence their distribution.

Whitmore, Cheryl. January 2000 (has links)
I describe the spider biodiversity for a savanna ecosystem, assess sampling techniques, investigate surrogate measures of species richness and measure the biotic and abiotic processes affecting spider diversity. Spiders were sampled at Makalali Game Reserve, Northern Province, South Africa from February to December 1999 using pitfall traps, sweep netting, beating and active searching. A total of 4832 individuals from 268 species (14 potentially new), 147 genera (8 endemic and 2 new records for South Africa) and 37 families (1 new record for South Africa) were recorded. There was no overall significant difference in spider diversity among different physiognomic habitat types. However, analysing the results at a functional group level revealed that the web builders were significantly affected by the habitat type. Mopane woodland habitat type had the greatest number of web builders and general bushveld the least. Sweeping and active searching sampled the greatest number of individuals and species respectively. I recommend a combination of at least beating and active searching, which together sampled the highest number of unique species, for efficient and cost effective surveys. There was a significant relationship between the spider species richness and other invertebrate richness. However, the relationship is not significant when functional groups are considered separately. There was also a significant relationship between the number of species and families and species and genera. However, species level identifications remain ideal for conservation purposes. Inexperienced participants significantly overestimate the number of species. The use of surrogates is not supported by the work conducted in this study. It is still unclear what biotic and abiotic processes or combination of processes influence spider diversity patterns at the local scale. Different spider functional groups are significantly influenced by different factors. However, habitat diversity (branches and vegetation density) was the most common factor influencing spider diversity . Predicted diversity (modelled using GIS and beta-coefficients from multiple regression analyses) was higher than measured diversity values. While further research into the role of other environmental variables is clearly required, current reserve management should aim to maximise microhabitat structural diversity. / Thesis (M.Sc.)-University of Natal, Durban, 2000.

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