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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.
1

The relationship between nasal turbinate structure and the ecological attributes of ungulates

Kietzmann, Michelle Ann January 2010 (has links)
The nasal turbinates of ungulates are complex bony scrolls within the nasal cavity. These intricate bony plates, covered by moist epithelium, provide a large surface area that facilitates a countercurrent exchange of both water and heat between turbinal lining and respired air. Given their functional importance, maxilloturbinate size and structural dimensions may vary among species of different body sizes, activity levels and from different habitats, and may also serve as a predictor of the ability of the species to cope with high temperatures or limiting water resources. This is the first study to measure nasal turbinate surface area in ungulates using high-resolution computed tomography (CT) scanning. Heads of eleven South African bovid species and one European bovid species were successfully scanned and surface area measurements made using stereological techniques. These species included Cape grysbok, springbuck, bushbuck, blesbok, impala, mountain reedbuck, fallow deer, kudu, nyala, gemsbok and blue wildebeest; and represent species of different body sizes, from a range of habitats and with different water dependencies and predator avoidance strategies. The total maxilloturbinate surface area increased with body size for all study species. The surface areas of the nasal turbinates varied rostrocaudally, with the highest surface area occurring approximately midway along the length of the maxilloturbinate bones. The Cape grysbok stood out as having a nasal turbinate surface area of 12.77 cm2/kg, which was lower than the observed trend, the reason for this not being clear from these data. Phylogenetic independent analyses showed that log body mass and water dependence had a significant effect on nasal turbinate surface area, with habitat, distributional range and anti-predator behaviour having no effect. Subsequent phylogenetic species comparisons showed that structural variations in nasal turbinate surface area were phylogeny based due to the close genetic relatedness of the study species, and not associated with any environmental factors. The environmentally linked results for water dependency need further investigation in future studies of larger sample sizes and a broader range of species. Changes in climatic conditions may impact on a species‟ activity patterns, with individuals being forced to make behavioural modifications rather than physiological or anatomical adjustments. However, there is no clear evidence to indicate large differences in nasal turbinate surface area in relation to water dependence. This subsequently rules out the use of nasal turbinate surface area as a predictor to which and how ungulate species will respond to increasing global temperatures.
2

The value of using landsat 8 indices to describe large herbivore distribution

Mordecai, Kim Morag 19 September 2016 (has links)
A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg in fulfillment of the requirements for the degree of Masters in Science. / Satellite imagery and remote sensing techniques provide a way to collect data over large temporal and spatial scales, and build indices that gauge ecological variables. These indices can explain the distribution of animals in their environment. In this study I compare the ability of various indices derived from Landsat 8, to reliably predict locations of different large herbivore species across diverse habitats. The study was undertaken in the Kgaswane Mountain Reserve, North West Province, South Africa. Daily locations of two herds of sable antelope (Hippotragus niger) and one herd of eland (Tragelaphus oryx) were used. One sable antelope herd (vlei herd) occupied a grassland plateau with a wetland and the other sable antelope herd (woodland herd), shared the wooded area at the base of the mountains with the eland herd. I described vegetation communities, burnt areas, geology and soil templates at animal locations during foraging bouts in the dry season; coinciding with the times of the Landsat images. The overall aim of this study was to see whether an index or a combination of indices could better describe animal locations than the normally used NDVI. I calculated a number of indices, and compared their predictive ability to define areas used by the study animals. Specifically, I compared the Normalised Difference Vegetation Index (NDVI) to Soil Adjusted Vegetation Index (SAVI), Visible Atmospherically Resistant Index (VARIgreen), Green Atmospherically Resistant Index (GARI), Normalised Difference Water Index (NDWI), a proxy for soil moisture; and mineral composite indices assessing clay minerals, ferrous minerals and iron oxide. I chose these indices as they describe the basic characteristics of an ecologically functioning unit. The locations of one of the sable antelope herds, located in grassland areas underlined by quartzite, were best described by NDVI, SAVI and VARIgreen. The locations of the other sable antelope herd, occurring in an open wooded area with shallow sandy soils on norite and quartzite, were best described by clay minerals and GARI. Eland locations, found in woodland areas characterised by deep norite soils, were best described by a combination of iron oxide, NDVI and SAVI. Therefore, NDVI proved to be an adequate indicator in open grassland areas, where it could be interchanged with SAVI, and improved by VARIgreen. In closed woodlands NDVI, SAVI and NDWI could all be used to describe browser locations. NDVI was not a suitable index when it came to describe locations of a grazer in a woodland/grassland matrix. However, it is important to keep in mind that my results pertain only to one dry season and two herbivore species, and therefore further studies would be needed to be able to generalise the results further. / MT2016
3

Resources overlap and the distribution of grazer assemblages at Telperion and Ezemvelo nature reserves

Deliberato, Henrique Guindalini January 2017 (has links)
A research report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science. Johannesburg, 2017. / The distribution of grazing herbivores is influenced by several factors, including spatial and temporal availability of resources. The Telperion and Ezemvelo Nature Reserves (TENR), located on the border between Gauteng and Mpumalanga Provinces, experienced a declining hartebeest (Alcelaphus buselaphus caama) distribution over the last years. Simultaneously, an increase in the density of plains zebra (Equus quagga) occurred in the reserves. In this study, I investigated the changes in the distribution of four herbivore species, namely red hartebeest, plains zebra, blue wildebeest and black wildebeest in TENR, and the possible influence that biotic and abiotic factors had on the distribution of hartebeest between 2010 and 2016. Data of aerial surveys conducted in the wet season of each year were used to assess the variation in herbivores distribution along the period. Furthermore, the influence of variables known to affect herbivore distribution (e.g. distance to water, slope gradient, spatial distribution of other herbivore species and vegetation greenness) was tested on hartebeest distribution in TENR. The results indicate that blue wildebeest (Connochaetes taurinus) had the highest distribution variation, while plains zebra presented the most spread distribution among the four species, and black wildebeest (Connochaetes gnou) concentrated their distribution almost entirely at the Ezemvelo nature reserve. Hartebeest avoided areas with the highest concentration of plains zebra, but did not show the same avoidance for areas with prevalence of wildebeest species. Further, high quality forage resources influenced the hartebeest distribution in TENR. Thus, competition for forage resources with bulk feeders may have affected the population and distribution of hartebeest between 2010-2016. / LG2018

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