A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, 2016. / Resource selection by animals is a hierarchical process, reflecting the spatio-temporal heterogeneity in biotic and abiotic environmental conditions and resources. In savannah ecosystems, the availability and nutritional quality of forage resources across the seasonal cycle constitute two of the main drivers of feeding choices, seasonal movements, and, ultimately, population dynamics of large herbivores. As a consequence of the increasing insularisation of protected areas in southern Africa, the understanding of the ecological requirements of confined populations of nomadic ungulates constitutes a crucial issue for their management.
The study aimed at determining the effects of forage quality and availability across the seasonal cycle on the home range occupation and resource selection by eland in an insular-like protected area, the Kgaswane Mountain Reserve (KMR) in South Africa. I focused on three spatio-temporal scales of selection: seasonal home range selection over the available landscape; habitat selection within the seasonal home range; and selection for plant species included in the diet.
The main objectives at the scales of landscape and habitat selection were: 1) to determine the extent and location of the seasonal home ranges utilised by collared adult female eland in the KMR, in order to identify the seasonally favoured resource units within the available landscape; and 2) to determine the influence of environmental drivers, including the seasonal variation in forage quality and abundance, on resource selection by eland at the two different scales. Four adult female eland were fitted with GPS collars, over the course of two years. The extent and location of annual and seasonal home ranges were estimated using a-LoCoH. The influence of environmental factors, including vegetation-type, burnt areas, and NDVI, on landscape- and habitat-scale selection of used locations at peak feeding times over available scattered points was tested using mixed-effects logistic regression models. Despite the small size of the KMR, eland occupied spatially distinct dry and wet season ranges. The dry season ranges were smaller than their wet season counterparts, and During the dry season, seasonal ranges were small, and were located in moderate to very green (as indicated by NDVI values) woodland areas in respect to the available landscape. Eland selected for dry grassland, wet grassland, and open shrubland (associated with low NDVI levels) during the wet season, when they coalesced into a nursery herd and occupied a relatively large home range. The
selective use of burnt areas over the available landscape units was mostly restricted to the wet season, after a green herbaceous flush had been prompted by rainfall events. Within the seasonal home ranges, eland preferentially foraged on burnt woodland and open shrubland, where re-growth of woody plants was also available. The study animals also selected for locations characterized by low vegetation greenness and biomass as a consequence of the concentration of foraging activities in open areas where low-lying browse was accessible.
At the smallest scale considered for this study, the two main objectives were: 1) to determine the changes in the use of vegetation types and burnt areas during foraging activities between two different seasons; 2) to determine forage selection at the plant species scale, as influenced by the phenophase of grasses and browse. In March-April 2015 (wet-early dry transition season) and July-August 2015 (mid-dry season), feeding sites of eland were located through both VHF-tracking and scanning from vantage points. Characteristics of used feeding sites were only descriptively addressed, and included vegetation type, burning, canopy cover, and soil catenal position. The greenness and basal cover of plant species were also recorded. Availability, acceptance, and dietary contribution for each species were calculated for the two seasons, while the influence of phenological traits on plant species selection was investigated through mixed-effects logistic regression models. Woody plants were consumed in larger proportions than grasses and herbaceous forbs during the entire study period. Woody forbs and shrublets such as Lippia javanica and Athrixia elata were particularly favoured. Eland targeted species offering high proportions of green leaves. During the wet-early dry transition, the deciduous Vangueria parvifolia was particularly selected for, while the consumption of evergreen species, including Searsia lancea, increased during the dry season. Most of the observed grazing took place on flushing burns during the wet-early dry transition. The decline in grass consumption was paralleled by a considerably lowered use of the burns and of the dry grassland during the dry season, as also reflected by collars data.
The results indicated that eland in the KMR adjusted their landscape and habitat selection in response to spatio-temporal variations in the availability and quality of food resources. During the wet season, flushing burns provided accessible green forage to nursery herds. Conversely, evergreen woody plants probably represented a crucial resource for eland during the limiting dry season, when herbaceous plants were mostly dormant and foliage on deciduous species
was unavailable. Therefore, environmental heterogeneity at different spatial scales likely constitutes a key factor for the persistence of eland populations in small, fenced reserves. / LG2017
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/21680 |
| Date | January 2016 |
| Creators | D'Ammando, Giacomo |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | Online resource (226 leaves), application/pdf |
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