3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Multilevel determinants of fertility behaviour in Eswatini(2018) Chemhaka, Garikayi BernardThe study re-examines the levels, trends and determinants of fertility in Eswatini. The overall objective of the study is to understand fertility behaviour of Swati women. Fertility behaviour is explained by actual (current and lifetime) fertility and proximate determinants of fertility measures. The following variables were considered as regression dependent variables: i) lifetime fertility (children ever born), ii) current use of contraception. The study used data from four population censuses (1976, 1986, 1997 and 2007) and 2007 Eswatini Demographic and Health Survey (DHS). The study employed direct and indirect estimation methods (P/F ratio methods-Brass, Trussell, Arriaga, Feeney; Relational Gompertz model and regression based methods-Rele’s, Palmore’s, Gunasekaran and Palmore methods), to estimate the level and trends of fertility in Eswatini. The impact of the proximate determinants of fertility on the level of fertility was assessed using the Bongaarts model and its modifications. Bivariate and multivariate (or multilevel) Poisson and logistic regressions analyses were used to examine the correlates of fertility and contraceptive use in Eswatini. The study found that between 1966 and 1976, fertility remained constant and thereafter fertility declined from 7.0 in 1976 to 4.6 children per woman in 2007. Contraceptive use among sexually active women is 46.1% of which 1.9% used traditional methods and 44.2% used modern contraceptives. Among the individual-level factors influencing fertility were child mortality, women’s empowerment, ideal number of children, employment, marriage, female education, wealth, age at first sex and age at first birth. At community-level, rural-urban residence played a significant role in shaping fertility in Eswatini. On the one hand, fertility was positively associated with child mortality, women’s empowerment, ideal number of children, employment, marriage and rural residence. On the other hand, fertility was negatively associated with female education, wealth, age at first sex, age at first birth, but not associated with mass media exposure and contraceptive use. The analyses of the proximate determinants of fertility revealed that contraception had the greatest impact on fertility reduction, then postpartum infecundability, sexual activity and induced abortion. In terms of contraceptive use, the study indicated that the following individual-level variables are significantly associated with contraceptive use in Eswatini: occupation, wealth, education, exposure to mass media, women’s empowerment, marital/union status, age, parity and age at first birth. The study recommends, among other things, improving female education, delaying age at first birth and sexual debut, and reducing poverty, child mortality and desired number of children as measures that can be adopted to accelerate fertility decline in the country. In addition, the study recommends more studies on aspects such as women’s empowerment, employment, marriage patterns, and rural-urban divide disadvantages which could provide additional insights into fertility behaviour. Efficient and effective fertility reducing programmes and interventions should be directed towards individual-level differences as well as considering the urban-rural community contexts in Eswatini.Item Longevity, population stage and size structures, morphology and reproduction of four long-lived grassland suffrutices(2012-01-18) Dayaram, AnishaLittle is known about the longevity of grassland suffrutex plants and the relationship between longevity and plant morphological structures and seedling growth strategies. The aim of this study was to determine the longevity of four grassland suffrutex plant species, namely Berkheya insignis, Callilepis laureola, Protea insignis and Tephrosia kraussiana. Seed viability, seedling growth, morphology, habitat and population structure and demography were also assessed and related to plant age. The rhizomes, seeds (if available) and canopies of B. insignis, C. laureola, P. simplex and T. kraussiana were removed from a site near Port Edward in the Pondoland region, KwaZulu-Natal, South Africa in April 2008. Seeds were available for P. simplex and T. kraussiana only. Seed germination and viability were tested in the field and laboratory using germination trials and tetrazolium tests. Greenhouse and field grown seedlings were used to monitor seedling growth and to record seedling morphology. The aerial and rhizome morphologies of adult plants excavated from the field were also recorded. The largest of these rhizomes were aged using radiocarbon dating. Attempts were made to develop morphological surrogates for plant age as no method currently exists. Plant density, demographies, number of inflorescences and various environmental variables of wild populations of B. insignis, C. laureola, P. simplex and T. kraussiana were sampled from the Red Desert Nature Reserve and the Umtamvuna Nature Reserve. Species morphologies varied, however important similarities suggest convergent evolution. These included a single vertical main stem rhizome with multiple side branches, early rhizome development in seedlings, and high root: shoot ratios. Seed viability was high in the laboratory but low seedling emergence was observed in the field. Seedling growth was rapid for T. kraussiana and slow for P. simplex. The population stage structure for all four species comprised primarily adults with few or no juveniles. Wild population plant height and main stem diameter followed normal distributions. Number of stems, basal area, canopy area and the number of floral structures had distributions favouring the smaller size classes. Soil P, N, K and organic carbon were important soil nutrients in a PCA analysis of the habitats of the four species. Radiocarbon dating yielded the following ages: B. insignis: 49-51 years, C. laureola: 49-50 years, P. simplex: 49-51 years and T. kraussiana: 51 years. There was a significant relationship between rhizome mass and canopy area, basal area, height, number of stems and main stem diameter. Since rhizome mass had a positive relationship with age- a relationship between age and aerial structures is likely. Therefore, creating surrogates for age may be possible. Overall, these species have moderate longevity, are poor seed producers with possibly slow population growth and are closely associated with soil nutrients. Therefore, these and other suffrutex species are particularly vulnerable to habitat destruction and climate change. The results of this study indicate that there needs to be a greater focus on below ground growth during ecological assessments in order to better understand the ecology of our diverse grassland biome plants.Item Social behaviour and activity patterns of the African ice rat Otomys sloggetti robertsi(2006-11-16T11:20:20Z) Hinze, AndreaI studied the sociality and activity patterns of free-living ice rats Otomys sloggetti robertsi. The ice rat is a medium-sized, diurnal, herbivorous rodent, endemic to the alpine habitats of the southern Drakensberg and Maluti Mountains in southern Africa. These environments are characterized by sub-zero temperatures in winter and high levels of solar radiation in summer, and snow can be expected at any time of the year. Previous research by other scientists indicated that the physiology of ice rats is more similar to congeners living at lower altitudes, and, instead the taxon has morphological and behavioural adaptations for coping with the temperature extremes in its environment. Predator pressure on ice rats was negligible in my study site, making the ice rat an ideal model for testing how environmental factors influence sociality and activity patterns. Sociality was investigated by using direct observations and through experimental manipulations. Colonies comprised 4-17 individuals with several reproductively active males and females. Colony members had a high degree of home range overlap, whereas interactions between colony members were rare and usually resulted in agonistic behaviour. Ice rats responded aggressively to experimentally-caged colony members positioned in different parts of their own colony and these were treated with the same level of aggression as were strangers. Moreover, colony members competed aggressively for better-quality introduced food, particularly in winter. From direct observations of male-female interactions, it appeared that ice rats mate promiscuously, which is most likely a consequence of the multi-male and multi-female colonies. Females spent long periods of time belowground with unweaned young which emerged aboveground independently at four weeks of age. The first litter born in a season dispersed at sexual maturity (males±14 weeks; females±9 weeks), but, since I did not observe the behaviour of litters born later in the breeding season, I was not able to tell if these dispersed as well. I excavated the burrow systems of ice rats and found an intricate interlinking underground tunnel system with sometimes more than 25 entrance holes and 1-2 nesting chambers, which would provide a thermoneutral refuge for the ice rats at night as well as during adverse weather conditions. Because the ratio of the number of animals in the colony to III the number of nest chambers exceeded one, I predicted that huddling occurs belowground, which was confirmed by video recordings of nest chambers. Diurnal aboveground activity patterns of ice rats were influenced by prevailing environmental conditions, which resulted in synchronous aboveground appearance of members in a colony. The summer activity pattern was bimodal, dominated by foraging and sun basking behaviour aboveground, with animals retreating belowground to escape high temperatures and radiation levels prevalent around midday. Ice rats utilized the warmer temperatures throughout the day in winter for aboveground foraging and basking. Otomys s. robertsi displays a spatial shift in its social system: colony members huddle belowground but display temporal territoriality aboveground. Such a social system is contrary to predictions previously made for this taxon (i.e. they live as family groups). Ice rat relatives living at lower altitudes mainly occur as non-social aggregations and one relative, the vlei rat O. irroratus, also displays temporal territoriality. Although sociality is common in rodents inhabiting temperate environments in the northern hemisphere, these rodents do not show territoriality at other times. I conclude that the social system of ice rats, in the absence of significant predation pressure, is determined by a combination of 1) environmental factors driving communal thermoregulation and 2) phylogenetic constraints imposed by competition for limited food resources.