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Ungulate browsing as an ecosystem process: browser-plant-soil interactions in a Southern African Savanna
Get PDFThesis (DPhil)--University of Pretoria, 2007.Ungulate browsing and its ecological effects at plant, population, community, and ecosystem levels were addressed in a eutrophic southern African savanna. This was to test predictions of prevailing hypotheses, which are based on research in boreal and temperate forests. Changes in plant morpho-functional traits and population structure of a staple palatable species, Acacia nigrescens Miller were addressed over a two-year survey among vegetation stands with very different histories of attack from herbivores. Moreover browser-induced effects on functional composition of a woody plant community were addressed along a strong browsing gradient. Nutrient cycling was investigated through measurements of leaf litter decomposition rates, as well as soil and leaf chemistry analyses. Finally, a modelling approach was used to make predictions on plant productivity and changes in soil nutrient availability under ungulate browsing according to opposite plant defensive traits (i.e. tolerance vs resistance). I found evidence that long-term selective browsing may negatively affect soil nutrient pool, at least in the vicinity of palatable woody plants. I proposed this might be due to the drastic reduction of leaf-twig litter mass returned to the soil, which likely decreased decomposer activity and negatively affected N mineralization rates. Hence, the processes responsible for a loss of nutrients in the soil were different from those proposed for northern hemisphere scenarios, which were instead due to decreased litter quality. However, I found evidence of high plant resilience in heavily browsed sites where Acacia stands shown (1) higher leaf N during the main growing season, (2) higher N release from leaf litter, (3) high concentrations of nitrate (NO3) and ammonium (NH4), and (4) similar, or even faster, litter decomposition rates than in lightly browsed sites. Firstly, this suggests that tree pruning triggers and maintains a fast nutrient cycling within the plant-browser system. The accelerating effect is supported by high mass compensatory growth abilities from highly palatable, fast-growing Acacia trees that produce highly decomposable litter. Secondly, browsing may have a long-term decelerating effect on N cycling through quantitative changes in litter production rather than through qualitative changes in litter chemistry. Further studies should better address processes related to soil nutrient cycling to confirm such hypothesis. I discuss how the interactive effects of browsing-grazing-soil fertility may influence nutrient cycling trough different ecological processes.Zoology and Entomologyunrestricte
Conserving wild dogs ( Lycaon pictus ) outside state protected areas in South Africa: ecological, sociological and economic determinants of success
Get PDFThesis (DPhil (Zoology))--University of Pretoria, 2006.The restricted geographic range and tenuous conservation status of wild dogs in South Africa were the motivating factors behind this study. Wild dogs have been extirpated from most of their historic range in South Africa, and now occur in three limited distributions: a) one viable population in Kruger National Park; b) a protected meta-population, consisting of 1 packs in six sub-populations (four on state owned reserves – Hluhluwe-Umfolozi Park, Madikwe Game Reserve, Marakele National Park, Pilanesberg National Park, and two on privately owned reserves – Karongwe Game Reserve, and Venetia Limpopo Nature Reserve), and c) ` 76 unprotected individuals in 17 packs and dispersing groups occurring outside protected areas, primarily in the game ranching areas of the extreme north and north east. Prior to the establishment of the proposed transfontier parks, the best prospects for range expansion likely exist on private land. My study investigated some of the ecological, sociological and economic issues associated with wild dog conservation on private land under various scenarios. Over the last few years, the focus of conservation efforts and donor funding expenditure (72.6% of funding) has been the establishment of the meta-population. This been effective – the target size (nine packs) of the meta-population has been exceeded in six years, four years less than the targeted schedule (10 years). From here, there are two ways in which donor funding might be used to achieve further range expansion outside state protected areas, through expansion of the meta-population by reintroducing wild dogs onto private nature reserves, and through the conservation of wild dogs in situ on ranchland. For either strategy, an estimated minimum area of 158.5 km2 is required to support the predation requirements of a pack of 12 wild dogs in northern South Africa, 172.8 km2 in eastern South Africa, and 354.2 km2 in north-eastern South Africa. Private reserve owners may not be willing to accept the costs of predation by wild dogs in the absence of compensation. Compensation for predation (101,762/year) in addition to the high start up costs of wild dog reintroductions (11,000 - 11,942 - 3,572 initially, and then 100,000 cf. 3-19 packs / $100,000). Furthermore, tourism revenue from wild dogs has the potential to offset the costs of their predation on ranchland under most scenarios, and promoting the conservation of wild dogs in situ on ranchland by assisting ranchers in establishing wild dog-ecotourism operations should be the focus of future conservation efforts. A substantial proportion of ranchers (52.3%) are positive towards wild dogs, and private landowners are potentially important facilitators in the conservation of the species in South Africa. The focus on future conservation efforts involving wild dogs in South Africa should be to establish wild dog populations in the proposed Limpopo/Shashi and Lubombo transfrontier conservation areas as soon as they are established, to encourage private reserve owners to reintroduce wild dogs at their own expense ,and to promote the conservation of naturally occurring wild dogs in situ on ranchland, by encouraging and assisting ranchers to establish wild dog-ecotourism programmes.Zoology and Entomologyunrestricte
Cheetah Acinonyx jubatus ecology in the Kruger National Park : a comparison with other studies across the grassland-woodland gradient in African savannas
No full textDissertation (MSc (Zoology))--University of Pretoria, 2006.The objectives of this study were(1) to analyse a data-set on cheetah home range size, habitat utilisation, prey selection and hunting behaviour in the Kruger National Park (KNP), and (2) conduct a comparative study on the above aspects of cheetah ecology across a variety of African savanna ecosystems. Cheetah home range sizes in the KNP for territorial male cheetahs were 173 km2, 438 km2 for a nomadic male cheetah coalition, and 193 km2 and 179 km2 for two female cheetahs. Cheetahs preferred open savanna habitat, although females used areas with thicker bush such as drainage lines) more than males, probably because this is the preferred habitat of their main prey. Analysis showed that while females were closely associated with drainage lines, males were closely associated with roads. A male cheetah coalition preferred scent marking along roads rather than in the bush. Impala occurred most frequently in the cheetahs’ diet, although males took larger prey than females. Cheetahs hunted and killed more frequently in open savanna, even though impala densities were higher in adjacent habitats. Mean chase distance for successful hunts was 18l9 m and unsuccessful hunts was 96 m. Cheetah hunting success was 20.7%, kleptoparasitism was 11.8%, mean kill retention time was 165 min, kill rated averaged 1 kill per 4.61 days, and consumption rate of a three-male cheetah coalition was 1,4 kg meat/cheetah/day. Across African savanna ecosystems, female cheetah home range size was determined by the dispersion patterns and biomass of medium-sized prey. Female home range size was larger in areas with migratory (833 km2) than sedentary prey (105 km2) and increase as prey biomass decreased in areas with sedentary prey only. Conversely, male cheetah territory size was smaller in areas with migratory (37 km2) than sedentary prey (108 km2). Although it was predicted that male cheetah territory size would be determined by female cheetah density, no relationship was found here. Across a range of African savannas, cheetahs showed distinct preferences for open habitats that provided some woody cover. Adults (40%) and juveniles (20%) of medium-sized prey made up the largest proportion in the cheetahs’ diet. There were, however, significant variations in the size and age groups of prey taken by cheetahs in different areas. Areas with the least amount of cover appeared to have the longest mean chase distance, and the greatest percentage hunting success and incidents of kleptoparasitism (%). A population viability analysis, using VORTEX, found that cheetah population viability was greater in a woodland savanna than a grassland savanna, particularly at small population sizes. While the grassland savanna population was most affected by changes in juvenile mortality the woodland savanna population with exceptionally high cub mortality may be a sink for cheetahs while the woodland population with lower cub mortality and predicted high dispersal rates may be a source. Maximum annual litter size and female mortality rates had large impacts on population persistence.Zoology and Entomologyunrestricte
Feeding ecology and social organisation of honey badgers (Mellivora capensis) in the southern Kalahari
Get PDFThesis (DPhil (Zoology))--University of Pretoria, 2001.The lack of fundamental biological information on the honey badger Mellivora capensis and its vulnerable conservation status were the motivating factors behind this study. A study population of 25 individuals (12 females; 12 males) was radio-marked in the Kgalagadi Transfrontier Park (KTP), South Africa. Through a combination of radio telemetry and visual observations (5 244 h) of nine habituated individuals (five females; four males), the feeding ecology, scent marking and social behaviour of the honey badger were investigated. The honey badger is a solitary, generalist carnivore with strong seasonal differences in diet. In support of optimal diet theory, the cold dry season diet is characterized by low species richness, low foraging yield, high dietary diversity and increased foraging time while the reverse is true in the hot wet and hot-dry seasons. The honey badger appears to shift between alternative prey species depending on their availability on a seasonal and daily level. The daily activity patterns of both sexes show a strong seasonal shift from predominantly nocturnal activity in the hot-wet and hot-dry season to more diurnal activity in the cold-dry season and this appears to be primarily affected by temperature. Despite marked sexual size dimorphism (males a third larger than females), no intersexual differences in diet or foraging behaviour were observed, but there were sexual and in males age-related differences in movement patterns, scent marking and social behaviour. The honey badger appears to have a polygynous or promiscuous mating system, but did not fit the general mustelid pattern of intrasexual territoriality. Instead, adult males had extensive overlapping home ranges (548 km2) that encompassed the smaller, regularly spaced home ranges of the females (138 km2) and young males (178 km2). Receptive females are an unpredictable and scare resource in space (large home ranges) and time (no breeding season) with a long time to renewal (inter-birth interval > 1 year). As a result adult males adopt a roaming rather than a staying tactic with competition for access to the mating burrow mediated by a dominance hierarchy loosely based on age, mass and testes size. The hierarchy appears to be maintained through regular aggressive and agonistic interactions and scent marking. Data suggest that latrine scent marking in adult males is related to advertising social status and maintaining the dominance hierarchy though “scent matching”. In females and young males latrine visits are rare, but token urination is common and its association with foraging behaviour suggests that it mediates spatio-temporal separation and/or resource utilization. Interspecific interactions between the honey badger and other mammalian and avian predators were common and included intraguild predation and interspecific feeding associations between the honey badger and seven other species (two mammals; five birds). The most common foraging associations were observed between the honey badger and the pale chanting-goshawk Melierax canorus and black-backed jackal Canis mesomelas. These associations appear to be commensalisms, with associating species benefiting from increased hunting opportunities and intake rate but no significant costs or benefits to the honey badger. Copyright 2001, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Begg, CM 2001, Feeding ecology and social organisation of honey badgers (Mellivora capensis) in the southern Kalahari, DPhil thesis, University of Pretoria, Pretoria, viewed yymmdd Zoology and Entomologyunrestricte
Elephants in the Waterberg : impacts on woody vegetation by breeding groups compared with bachelors
No full textDissertation (MSc (Zoology))--University of Pretoria, 2006.In May 1994 IFAW funded the relocation of 50 elephants from the Kruger National Park to Welgevonden Private Game Reserve in the Northern Province, South Africa. Impact by the elephants on the vegetation of this reserve has since become a concern. The aim of this study was to quantify impact by the elephants on the woody vegetation by investigating vegetation and habitat use by elephant bachelor and breeding groups. This was determined by comparing resource use between sexes within seasons, and within sexes between seasons. Data were collected at two ecological scales: feeding patch scale and habitat scale. Feeding data were collected from 202 food plots, defined from 161 elephant sightings. In the dry season, when resources are often limited, no difference in feeding patch use was found between bachelor groups and breeding groups. This may suggest a lack of inter-sexual competition and could therefore suggest that the elephant population is currently below carrying capacity. Three habitat types are available to the elephants: plateau, hillslope and valley bottom. Both bachelor groups and breeding groups preferred valley bottom in comparison with habitat availability, in both seasons. When sexes were compared within seasons, in the dry season, bachelor groups used valley bottom more and breeding groups used hillslope more.Zoology and Entomologyunrestricte
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Inter-Relationships In The Global Environment
No full textIt is very recently in the history of humanity that we have begun considering environmental issues on a global scale. This is not only because we have recently realized that humanity is making a significant impact on the global environment, but mainly because it has been very difficult to get the complete subject in view. At the scale of the individual person, the global environment is a very large thing that cannot be fully understood from an Earth-bound perspective. This problem is analogous to that of trying to appreciate and understand the artistry of a large oil painting or tapestry, when standing only a few inches away from it. We no longer have this excuse, however, because modern man is now able to step back and see the full picture. In the present stage of the space-age it is possible to view the entire planet Earth in exquisite detail, like a small organism under a microscope
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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