Thesis (MComm)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Recently countries have become more aware of the potential anti-competitive effects of anti-dumping measures. This is mostly due to the view that anti-dumping measures, as trade policy instruments, are at odds with the objectives of competition policy. According to many economic writers the only rational economic justification for anti-dumping measures is predatory dumping as an extreme form of price discrimination. Apart from the dramatic change in the economic justification for the use of anti-dumping measures over the last decades, there has also been a significant change in the countries that implement these measures. Since the Uruguay Round of Multilateral Trade Negotiations there has been a shift from developed countries to developing countries being the main users of these policy tools. In the last couple of years the member countries of the Southern African Customs Union have been under increased pressure by private firms to enable the use of anti-dumping measures on intra-regional goods trade. However, the appropriateness of utilising these measures on intra-regional trade in the context of a custom union has been a contentious issue in recent economic debate. These measures erect trade barriers among the member states which are against the basic premise of a customs union. This has resulted in most economists calling for the prohibition and replacement of anti-dumping measure with either coordinated domestic or harmonised regional competition policies. In developing the regional and national policies on anti-dumping the SACU member states can follow two main stream approaches. The first is the incorporation of various competition principles into anti-dumping rules to limit the negative welfare and anti-competitive effects of utilising anti-dumping measures, while the second is the abolition of anti-dumping measures in the region which is then replaced by competition policy. The option best suited for SACU depends on the differing viewpoints on implementing anti-dumping measures in a customs union. However, irrespective of which policy combination is chosen, regional and national polices and authorities will have to be created, adapted and/or amended in order to have an effective interaction between anti-dumping and competition policies applicable to intra-regional trade. / AFRIKAANSE OPSOMMING: Lande het ontlangs meer bewus geword van die moontlike negatiewe uitwerking wat maatreëls teen storting van goedere in markte kan hê op plaaslike en internasionale mededinging. Dit is hoofsaaklik as gevolg van die siening dat teen-stortingsmaatreëls, as instrumente van handelsbeleid, se doelwitte teenstrydig is met die van mededingingsbeleid. Volgens vele ekonomiese skrywers is die enigste rasionele ekonomiese regverdiging vir teen-stortingsmaatreëls predatoriese storting as ‘n uiterse vorm van prysdiskriminasie. Afgesien van die dramatiese verandering in die ekonomiese regverdiging vir die gebruik van teen-storingsmaatreëls oor die laaste dekades, het daar ook ‘n beduidende verandering plaasgevind in die lande wat hierdie maatreëls om goedere handel implementeer. Sedert die Uruguay Rondte van Multi-laterale Handelsooreenkomste het daar ‘n verskuiwing plaasgevind van ontwikkelde lande na ontwikkellende lande as die belangrikste gebruikers van hierdie beleidsinstrumente. In die laaste paar jaar het private firmas die lidlande van die Suider-Afrikaanse Doeane-Unie onder toenemede druk begin plaas vir die gebruik van teen-storingsmaatreëls op invoere vanaf die res van die streek. Alhoewel, huidiglik is die toepaslikehid van die gebruik van hierdie maatreëls op handel, in die konteks van ‘n doeane-unie, steeds ‘n omstrede kwessie binne ekonomiese dabatte. Hierdie maatreëls rig handelsversperrings tussen lidlande op wat teen die basiese veronderstelling van ‘n doeane-unie is. As gevolg hiervan is die meeste ekonome van die opinie dat teen-storingsmaatreëls vervang moet word met óf gekoördineerde binnelandse of geharmoniseerde streeks- mededingingsbeleid. Die SADU-lidlande kan twee benaderings volg in die ontwikkeling van streeks- en nasionale beleid oor teen-storingsmaatreëls. Die eerste is the insluiting van verskillende mededingingsbeginsels in bepalings wat handel oor teen-storingsmaatreëls om sodoende die moontlike negatiewe gevolge van hierdie maatreëls te beperk. Die tweede opsie is om teen-storingsmaatreëls op streeks-invoere met bededingingsbeleid te vervang. Die mees gepasde opsie sal af hang van die verskillende standpunte rondom die toepaslikheid van teen-stortingsmaatreëls in ‘n doeane-unie. Alhoewel, ongeag die beleidskombinasie wat gekies word sal nasionale en streeks-beleid en owerhede geskep, aangepas en/of gewysig moet word ten einde ‘n effektiewe interaksie tussen teen-storingsmaatreëls en mededingingsbeleid binne SADU te verseker.

The Anostraca are a group of crustaceans belonging to the class Branchiopoda. They are predominantly restricted to temporary, inland waterbodies, which in southern Africa, include rockpools, animal wallows, and large "pans". The anostracan fauna of southern Africa was last examined in detail in 1929 by Barnard, and recent collecting in a number of areas indicated the need to update earlier work. A total of four genera, each belonging to a separate family, and forty-six species, some of which had not previously been described, are presented in this thesis. The monogeneric family Streptocephalidae is well represented in Africa, and the fauna of Africa south and north of the Zambezi and Kunene Rivers, as well as Madagascar is reviewed. The Streptocephalus species are characterised by having an S-shaped antennal process, terminating in a cheliform "hand" region. The species were divided into ten groups based on similarities in antennal process morphology. The descriptions of five new species have been published, and an update on distribution and specimen data for a number of species are presented. An additional, as yet unpublished new species from Zimbabwe is presented. The genus Artemia, although well researched in other parts of the world, has been largely ignored in southern Africa. Bisexual populations occur along the Cape coast, and a set of specimens from Namibia, which includes only females, may indicate that A. parthenogenetica is also present on the subcontinent. The frontal knob morphology of the Cape specimens is similar to that of A. tunisiana from northern Africa and the Mediterranean. The family Branchipodidae is characterised by the fusion of the basal joints of the male antennae to form a so-called "clypeus". This family is represented in southern Africa by a diverse fauna of the genus Branchipodopsis. Eleven previously described species, as well as five new species are presented. An attempt was made to divide the sixteen species into species groups, as was done for the streptocephalids, but this proved difficult. The taxonomically useful characters in this genus are largely restricted to the basal processes. An additional character, the presence of expansions of the posterior thoracic segments in the females of some species could be useful. Much intraspecific variation in clypeus morphology was evident, particularly in two of the widespread species. Branchipodopsis species commonly occur in small pools which fill a number of times during the wet season and this has probably led to the development of localised adaptations, and intraspecific variation, or even species endemic to very restricted areas. Three sets of specimens which belong to the family Branchipodidae, but to no known genus, were recently collected from north-eastern Natal, the eastern Cape and the Namib desert in Namibia. These specimens share a single, large process positioned medianly on the fused basal joints, as opposed to a pair of processes in this position. However, the morphology of the penes, and the position and form of other antennal processes could indicate that the specimens are not congeneric. Unfortunately, more material is necessary before the descriptions of two of these possible new genera can be published. Three species of the genus Branchinella, of the family Thamnocephalidae, occur in southern Africa. These species have a well developed frontal process, and fully retractible penes. Bran chin ella spinosa was recorded from the Makgadikgadi Pan in northern Botswana, and was probably introduced to this area from north Africa, or Europe, where it has a wide distribution. The other two southern African species have been collected from few localities, and in small numbers, and this may be connected to cyst hatching processes. The southern African anostracan fauna exhibits distinct distribution patterns and these . appear to be influenced by climate, with rainfall having the dominant influence in the western half of the subcontinent, and temperature influencing distribution in the eastern half. The high altitude Escarpment forms a barrier to the movement of species between the coastal margin and the central plateau region. The formation of the Escarpment could have resulted in vicariance speciation in some anostracans, but in most cases, allopatric speciation appears to have occurred. The type of habitat also influences species distribution in a number of ways. The great anostracan species richness in southern Africa is probably related to the climatic heterogeneity of the subcontinent, as well as the possible origin of two genera in Gondwanaland, and the absence of a Pleistocene glaciation in Africa. Large parts of southern Africa have not been sampled, and the exact status and distribution of many species is uncertain. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1994.

A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science. April, 2013 / Recognising the mechanisms that led to the deposition of the Plio-Pleistocene caves of South Africa provide an irreplaceable window into the environment at the time. Differentiating between various accumulating agents based on the markings and accumulation variances has become an integral part of palaeontological research. Large birds of prey have been investigated for their connection to the Australopithecus africanus type specimen, commonly, the Taung Child. The verreaux’s eagle, Aquila verreauxii, was investigated in this study to establish whether it produced a taphonomic signature that would be distinguishable from other similarly sized raptors and small mammalian carnivores. Prey remains were collected from 11 nesting-sites in the Gauteng and Northwest Provinces as well as nesting-sites from across the Northern and Western Cape Provinces. The objective was to illustrate how prey selection was directly influenced by the immediate environmental stresses. Prey was analysed in terms of prey choice, skeletal part representation and the markings that the skeletal elements bore. Of the total of 886 specimens that were collected, rock hyrax (Procavia capensis), hares (Lepus sp.), Smith’s red rock rabbit (Pronolagus rupestris) and helmeted guineafowl (Numida meleagris) were the most common. The skeletal part representation directly mirrors the feeding behaviour of Verreaux’s eagles: body parts with larger muscle attachments and skeletal elements covering choice meat options were most often targeted and damaged. Finally, ten damage types were recorded as well as the combinations thereof, of which chewed and crenulated edges, V-nicks, removal of bone and punctures featured prominently. The results showed that verreaux’s eagles do leave a characteristic taphonomic signature in terms of the assemblage composition as well as the markings on bone surfaces.

A thesis submitted to the Faculty of Medicine University of the Witwatersrand, Johannesburg fulfilment of the requirements for the degree of Philosophy / Seven Y chromosome probes and thirteen restriction enzyme digests were used to examine a conservative estimate of 20000bp, and no new Y-specific polymorphisms were revealed by these systems. The Y chromosome probe 49a, which reveals a Y-specific haplotype with TaqI, was shown to reveal five new complex polymorphisms with Bglll, Hindlll, Pst I, PvuII and Sstl. The new polymorphisms exhibit great genetic diversity, and each enzyme reveals numerous haplotypes, which mostly occur infrequently and are population-specific. The haplotypes for a given enzyme do not correlate strictly with those revealed by the other enzymes, including TaqI, suggesting that each polymorphism results from a combination of restriction site mutations and rearrangement events. Association between the different 49a polymorphisms occurs only in individuals of recent common genetic origin. Y-specific 49a/TagI haplotypes were determined for 933 individuals drawn from 23 different African populations. A total of 31 new haplotypes were observed, some of which contained new alleles or allelic variants. Duplication, in addition to CpG mutation, is implicated in the generation of certain allelic variants. Cluster analysis of genetic distances between populations was calculated using the 49a/TagI haplotype frequencies. Y-specific 49a/TagI haplotype analysis of individual populations was not sufficiently sensitive to accurately distinguish between the different Bantu-speaking Negroid tribal groups. Cluster analysis of larger groupings was more stable, and with the exception of the Khoisan, resulted in a basic split between African and non-African populations. The linkage disequilibrium of the XY275 MspI Y-linked polymorphism was determined. The high allele was generally found in association with the Y chromosome, but the Y-associated low allele was found to occur in Bantu-speaking Negroids, Khoisan-speaking Negroids, the Khoisan, two groups of mixed ancestry, and the Caucasoid South African Asiatic Indian population. The discovery of Y-associated low alleles in non-African as well as African populations suggests that more than one Y chromosome gave rise to the present-day non-African population. The pDP31/EcoRI, p21Al/TagI and Y Alu polymorphisms were also studied in several southern African populations. The pDP31 duplication occurred at high frequencies in Caucasoids, and could be used to indicate Caucasoid male gene flow into hybrid populations. The p21Al/TagI point mutation showed no distinct trends in frequency in the different populations, and several Taql mutations are proposed to have occurred in the repeat unit recognized by this sequence. The Y Alu polymorphism occurred infrequently in Caucasoids, at intermediate frequency in the Khoisan, and at high frequency in Negroids. The presence of the Y Alu insertion in all three major population groups studied is interpreted to suggest that the insert predates the diversification of Homo sapiens. The relationship between the different Y-linked polymorphisms was determined in the populations studied. The Y Alu polymorphism is believed to have originated once from sequencing data, but such information is not available for the other Y polymorphisms studied. No absolute relationship was observed between the Y Alu polymorphism and the 49a/TagI, XY275 Mspl, pDP31/£coRI and p21Al/TagI polymorphisms. It is suggested that the latter polymorphisms have arisen more than once. / WHSLYP2017

A thesis submitted to the Faculty of Medicine, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy / Two classes of hypervariable loci, VNTRs and (CA)n repeats, represent a rich source of highly polymorphic markers in the human genome. The main objective of this study was to assess their usefulness in elucidating the relationships between 17 southern African populations and to assess the feasibility of paternity testing using these hypervariable markers in the local context. / WHSLYP2017

Using the Scanning Electron Microscope (SEM), fruit surface and pericarp anatomy were investigated in the African species of Bolboschoenits (Ascherson) Palla [B. maritimus (L.) Palla; B. glaucus (Lam.) S.G. Smith; B. nobilis (Ridley) Goetghebeur & D.A. Simpson; B. grandispicus (Steud.) K. Lewejohann & W. Lobin] and extended worldwide to cover most known species. There was consideration of type specimens wherever possible. Two main patterns of pericarp construction were revealed, with modifications. Using fruit samples from field populations, a surveillance of embryos was carried out to gain some information on percentages of perfect embryo development and variability in embryo outline (as seen in optical, median sagittal section), within and between selected species. Inflorescence structure within African species was studied and illustrated photographically and diagrammatically. The collective information obtained was directed towards better understanding of species limits within the genus and towards gaining evidence of the significance of natural hybridisation as a cause of morphological variability within some taxa. Formal taxonomy including a key to the identification of the African species is provided. Profuse illustrations of pericarp structure of world species are given, as are colour photographs of the African species, excepting B. grandispicus. A tentative pattern for subgeneric division of Bolboschoenus based primarily on pericarp morphology, is suggested supplemented by a world map illustrating the presently known distribution of the suggested groupings. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 1998.

This study extends an earlier M.Sc. research project on the narrow-leaved species of the genus Asclepias L. (30 species) to cover the entire subtribe Asclepiadinae sensu K. Schum. in southern Africa- (182 species in 23 genera). Two genera (Eustegia R. Br. and Pentarrhinum E. Mey.) are revised and then removed from this tribe. The remaining 177 species and 21 genera form the focus of this thesis, whose principal objectives are to reevaluate the taxonomic and evolutionary significance of various macro, micro and chemical characters and then use them to produce a classification that, more closely, reflects the overall similarity and phylogeny of the taxa involved. Species and genera are recircumscribed based on the wealth of data that has come to light since the subtribe was last revised by N.E. Brown (1907-1908) some 90 years ago. This process was supplemented by extensive field work, observations on pollination and reproductive biology, ecology, biogeography, conservation and ethnobotany. The majority of this thesis consists of a compilation of 17 papers, 12 of these published and most, but not all, of the remainder in preparation for press. Two of these papers form the bulk of the taxonomy. The first deals with what was the genus Asclepias in southern Africa. The genus is now believed to be confined to the Americas. The • Botswana, Lesotho, Namibia, South Africa and Swaziland. southern African species have diverse origins and are partitioned into 7 genera, one of them (Gomphocarpus R. Br.) resurrected, two of them (Aidomene Stopp and Aspidonepsis Nicholas & Goyder) expanded and four of them (Paulforstera, Sigridia, Bruynsia and Pachyacris) described as new. Gomphocarpus is divided into two subgenera and Aidomene into four subgenera. Three new species are also described. The second paper investigates the bulk of most of the remaining genera. Kanahia R. Br., Cordylogyne E. Mey. and Fanninia Harv. remain as is. Xysmalobium R. Br., previously a genus of 19 species in southern Africa, is reduced to three species in two subgenera. Trichocodon is segregated off from Pachycarpus E. Mey. as a new genus. While two species, previously placed in Xysmalobium, are added to Pachycarpus, but placed in the new subgenus Parapodiopsis. Parapodium E. Mey. is reduced from three to two species and Periglossum Decne. is reduced from five to three species, one of them newly described. Woodia Schltr. and Stenostelma Schltr. are both considerably expanded, mainly with species previously housed in Xysmalobium), and the former divided into two subgenera. The third paper briefly looks at the Schizoglossum E. Mey., Miraglossum Kupicha and Aspidoglossum E. Mey. Some changes are suggested but, as further work is needed, none are formalised. As a corollary to the taxonomy, secondary metabolite profiles of 38 species and 17 genera were done using Thin layer Chromatography. The results sometimes confirmed morphological patterns and sometimes were at odds with them. A trend from simple profiles to more complex profiles seems to echo the suspected phylogeny of the genera within this sub tribe. Some species and genera have greater chemical diversity than others and secondary metabolites are shown to vary considerably in different parts of a single plant. As a supplement to the above work or because they are cited elsewhere in the dissertation, published papers dealing with floral structure, the asclepiadaceous work of Rudolf Schlechter, as well as miscellaneous works in the tribe Stapelieae, are also given. / Thesis (Ph.D.)-University of Durban-Westville, 1999.

The majority of the population in South Africa use traditional health care to treat various mental conditions. This thesis has two main objectives; to bring together a comprehensive and detailed record of psychotropic plants used in southern Africa by indigenous peoples for medicinal or cultural purposes. Secondly, this research attempts to investigate the validity and rationale of the use of these plants by screening them in various biological assays for psychotropic activity. Plants were selected, based on their traditional use and availability, and were screened in four assays, which detect biological activity of a useful nature. A number of in vitro enzymatic and neuronal signal transduction assays were employed in this thesis, the inhibition of the serotonin reuptake transporter protein (SERT); inhibition of catabolic enzymes (e.g. acetylcholinesterase, monoamine oxidase); GABAA- benzodiazepine receptor binding. The influence of legislation, past and present, on the state of traditional medicine is highlighted. Aspects of the philosophies and practises of the various practitioners of South African traditional medicine will be discussed. An annotated list compiled from available ethnobotanical literature of plants traditionally used for central nervous system-related purposes is provided. It contains more than 330 species, from 94 families, which are currently used or have been used for cultural, medicinal and recreational purposes related to the central nervous system (CNS). Where available, information pertaining to plant part used, preparation method, dosage, route of administration, known and potentially active constituents are included. Seventy five extracts from 34 indigenous plant species used in South African traditional medicine or taxonomically related to these were investigated for their affinity to the serotonin reuptake transport protein, making use of an in vitro [3H]-citalopram serotonin reuptake transport protein binding assay. Aqueous and 70% ethanolic extracts of various plant parts were screened and 45 extracts derived from 15 plant species showed affinity. The affinity of 12 extracts from four plants was characterized as high (more than 50% inhibition at 5, 1, and 0.5 mg/ml). Plant species with high affinity to the serotonin reuptake transport protein included Agapanthus campanulatus, Boophone disticha, Datura ferox and Xysmalobium undulatum. Agapanthus campanulatus yielded high activity in aqueous extracts from leaves and flowers. B. disticha showed high activity both in aqueous and ethanolic extracts of leaves and bulbs. D. ferox showed high activity in aqueous extracts from the seeds and X. undulatum showed high activity in the ethanolic extract of the whole plant. Two compounds, buphanadrine and buphanamine, were isolated by bioassay-guided fractionation on vacuum-liquid-chromatography (VLC) and preparative thin-layer-chromatography (TLC) from B. disticha. The structures of the compounds were determined by 1H and 13C NMR. Fractions were tested for affinity to the serotonin transporter in a binding assay using [3H]-citalopram as a ligand. The IC50 values of buphanidrine and buphanamine were 274 ìM (Ki = 132 ìM) and 1799 ìM (Ki = 868 ìM), respectively. The two alkaloids were also tested for affinity to the 5HT1A receptor, but only showed slight affinity. Aqueous and ethanol extracts of 43 plants that are traditionally used to treat against epilepsy and convulsions were initially tested in the GABAA-benzodiazepine receptor binding assay, where the binding of 3H-Ro 15-1788 (flumazenil) to the benzodiazepine site is measured. The GABAA-benzodiazepine receptor complex is involved in epilepsy and convulsions. Out of the 118 extracts tested, one aqueous and 18 ethanol extracts showed activity. The most active extracts were the ethanolic leaf extracts of Searsia tridentata, Searsia rehmanniana and Hoslundia opposita and the ethanolic corm extract of Hypoxis colchicifolia, which all showed good dose-dependent activity. A further forty-six ethanol extracts from another 35 species, both indigenous and exotic that are traditionally used predominantly as sedatives or to treat various CNS-related ailments were tested in the GABAA-benzodiazepine receptor-binding assay. Out of the 46 extracts tested, seven showed good activity and 10 showed moderate activity. The most active extracts were the ethanolic leaf extracts of Arctopus echinatus, Artemisa afra, four Helichrysum species and Mentha aquatica which all showed good dose-dependent activity. Two biflavonoids with activity in the 3H-Ro 15-1788 (flumazenil) binding assay were isolated by high pressure liquid chromatography (HPLC) fractionation of the ethanol extract of the leaves from Searsia pyroides. The structures of the two biflavonoids were elucidated by nuclear magnetic resonance spectroscopy (NMR) to be agathisflavone and amentoflavone. Agathisflavone and amentoflavone competitively inhibited the binding of 3H-Ro 15-1788 with a Ki of 28 and 37 nM, respectively. Extracts of Searsia dentata and Searsia pentheri were not as active as the extract from Searsia pyroides; both were found to contain apigenin and agathisflavone. The monomer apigenin, agathisflavone and amentoflavone were fitted into a pharmacophore model for ligands binding to the GABAA receptor benzodiazepine site. This reflected the affinities of the compounds in the [3H]-flumazenil binding assay. Mentha aquatica, a mint that is found in Europe and Africa, is used in Zulu traditional medicine for spiritual purposes. The ethanolic leaf extract showed a strong affinity to the GABA-benzodiazepine receptor. Viridiflorol from the essential oil and (S)-naringenin from an ethanolic extract was isolated by bioassay-guided fractionation using binding to the GABA-benzodiazepine site. Viridiflorol had an IC50 of 0.19 M and (S)-naringenin of 0.0026 M. Twenty plants used in Zulu traditional medicine for several CNS-related ailments were screened for MAO inhibition and specific MAO-B inhibition activity. MAO-B inhibitors are currently employed in the treatment of neurodegenerative related illnesses such as Parkinson's and Alzheimer's diseases. A photometric peroxidase linked assay was used to determine the inhibition of the oxidative deamination of tyramine by MAO isolated from rat liver. Ruta graveolens exhibited the best MAO inhibitory activity (ethyl acetate leaf extract = IC50 5 ± 1 ìg/ml, petroleum ether extract = 3 ± 1 ìg/ml) and specific MAO-B inhibition (ethyl acetate leaf extract = IC50 7 ± 6 ìg/ml petroleum ether extract = 3 ± 1 ìg/ml). Schotia brachypetala, Mentha aquatica and Gasteria croucheri also exhibited good MAO-B inhibition activity. Six extracts of varying polarity of Mentha aquatica were tested in a photometric peroxidase linked MAO bioassay. The 70% ethanol extract had highest inhibitory activity. (S)-Naringenin was isolated from the extract by bioassay guided fractionation on VLC and preparative TLC. The structure of the compound was determined by 1H, 13C and 13C-DEPT NMR and optical rotation. The IC50 values for MAO inhibition by naringenin were 342 ± 33 ìM for the rat liver mitochondrial fraction, 955 ± 129 ìM for MAO-A and 288 ± 18 ìM for MAO-B respectively. South African traditional medicine clearly utilizes many botanical species with CNS-related activity. Only a small number of the more than 330 southern African plant species reported to treat or alter the CNS have been scientifically evaluated. To date very few of the active compounds have been isolated and identified. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

No abstract available. / Thesis(Ph.D.)-University of Durban-Westville, 1996.

The Brown-headed Parrot (Poicephalus cryptoxanthus) is a poorly known species inhabiting open woodland in south-eastern Africa. This study elucidates critical aspects of the species ecology and although each of these categories impinge on one another, it concentrates on two broad biological aspects, diet and breeding biology, and vocalizations. The species has a generalist diet, switching from one suite of food species to another as and when those species become available, with no species critical for its survival. Analysis of dietary items throughout the year and comparison with handling times and availability reveals that at no time is the species under dietary constraint. Evidence from association indices and behavioural observation shows that the popular view that the Brown-headed Parrot forms pairs just before breeding is erroneous. Birds retain pair bonds and the bond is long-term, lasting at least throughout the year. Congregations are therefore of a classical fission/fusion type with the sub-units being the paired males and females. A mathematical model of the growth of captive chicks is presented, as a guideline to alert potential breeders of Brown-headed Parrots of malnutrition or disease. The species is a secondary cavity hole nester and whilst, the breeding biology of the species is summarised, the importance of large and old trees for breeding opportunities of the species is emphasised. This theme is continued by testing various adaptive hatching hypotheses as possible explanations of asynchronous hatching in the species. It is suggested that asynchronous hatching may be an adaptive strategy moderating against the number of suitable nesting cavities. The vocalization repertoire of the Brown-headed Parrot is described and seven separate vocalizations are recognized. None of these are associated with sexual situations, offering further evidence of a long-term pair bond. Evidence is offered that Brown-headed Parrot chicks can recognise their parents from individual vocal signatures supporting previous evidence from a number of species where chicks may mingle with unrelated chicks. Conversely, parents seem to be unable to recognise their chicks in the same way. It is concluded that this inability may be a result of strong one-way selection pressure, where the costs outweigh the benefits for parents with more than one chick or may be related to the experimental design. Individual recognition by voice implies individual voice differences and the adult double chip contact call is analysed using multivariate statistical techniques. The analysis separates individuals on the basis of frequency and temporal patterns and it is concluded that these parameters may allow individual voice differentiation. Finally, high frequency aspects of the double chip contact call are examined. These frequencies lie above the normally accepted upper threshold of avian hearing. From laboratory and field experiments, behavioural evidence is presented suggesting that the Brown-headed Parrot reacts to these frequencies and may use their degradation as a means of ranging distances to conspecifics. / Thesis (Ph.D.)-University of Natal, Pietermaritzburg, 2002.