71 Records out of 22207 Records

'Staying together' : people-wildlife relationships in a pastoral society in transition, Amboseli ecosystem, southern Kenya.

Author: Ferreira de Lima Roque de Pinho, Maria Joana

Awarding University: Colorado State University, USA

Level : PhD

Year: 2009

Holding Libraries: Dissertation Abstracts International ;

Subject Terms: Biological sciences ; Animal behavior ; Pastoralists ; Wildlife ; Amboseli, Kenya ;

Abstract:

This study looks at three dimensions of the relationship between Maasai and wildlife: attitudes towards wildlife; cultural models of human-wildlife relationships; the aesthetic value of wildlife and its relation to support for wildlife conservation. First, I found that attitudes varied with land tenure, formal education, religion and gender. I used a regression analysis to identify predictors of positive attitudes towards wildlife. Being a Christian is the strongest predictor, followed by being male and residing on communal land. Second, I followed a cognitive anthropology approach to analyze how Maasai relate to wildlife. 'Cultural models' are implicit, shared cognitive representation of a conceptual domain that mediate our understanding of the world and are differentially distributed, socially transmitted and correlated with behavior. I investigated content and distribution of Maasai models of their relationship with wildlife. With discourse analysis, I identified two contrasting models of human-wildlife relationships. In the 'traditional' model, wildlife are seen as different from cows in everything but as having the right to be on the land since God meant for humans, cows and wildlife to 'stay together'. In contrast, in the 'modern' model, wild animals are useful and income-generating like cows, but people wish to be separated from them. I used cultural consensus analysis to determine the distribution of agreement with each model. It shows that there is one consensual model that is close to the 'modern' model. This study shows a shift towards models of human-wildlife relationships that are informed by western culture, the market economy and conservation. The consensual model contrasts with the vision that conservationists have for the ecosystem. Investigating stakeholders' cultural models is a step towards addressing such conflicts. Lastly, I examine the role of aesthetic value in human-wildlife relationships. I show that Maasai appreciate visual beauty in wild animals and enjoy the sight of wild animals. Then, I determine that there is an association between how Maasai aesthetically value species, preferences thereof and support for their conservation. The community-based conservation approach emphasizes the economic value of wildlife to local communities. This study suggests that these strategies would benefit from considering non-economic dimensions of human-wildlife relationships

HIV-specific CD8+ T cell phenotype and HIV-1 genetic diversity : understanding the interplay [kenya].

Author: McKinnon, Lyle

Awarding University: University of Manitoba, Canada

Level : PhD

Year: 2009

Holding Libraries: Dissertation Abstracts International ;

Subject Terms: Biological sciences ; HIV infection ; Genetics ;

Abstract:

Historically, vaccination has been the most effective way to limit the spread of infectious diseases, but candidate HIV vaccines have so far been unsuccessful. Major challenges surrounding HIV vaccination are the genetic diversity and evolutionary capabilities of HIV, and an incomplete understanding of which immune responses are capable of providing protection. This thesis examines relationships between these obstacles in Kenyan populations. While CD8+ T cells responses were rarely observed in HIV-resistant subjects, most HIV-infected subjects had detectable responses. There were several instances in which Glade influenced the detection frequency and evolution in HIV-1 infection. We found a high degree of cross-reactivity and shared epitopes between clades, as well as examples of Glade-specific responses. While many previous studies have focused on IFN-? secretion as a immunological readout, we provide evidence that CD8+ T cell cross-reactivity and epitope specificity differ between IFN-? and proliferation, the latter associated with better disease progression outcomes. Finally, we characterized CD8+ T cells specific for variant-bound HLA class I tetramers and found that different populations of cells may recognize different epitope variants, and that a variant associated with proliferation displayed a weaker interaction with HLA and TCR. In several instances, we found that Env-specific IFN-? secretion was associated with worse clinical outcome. These findings offer a better understanding of the bidirectional interaction between HIV genetic diversity and various attributes of CD8+ T cell responses, and highlight the need for a more thorough immunological assessment of HIV vaccine candidates

East African biodiversity and molecular systematics of wood inhabiting ascomycete fungi (Ascomycota) [Kenya].

Author: Mugambi, George K

Awarding University: University of Illinois, Chicago, USA

Level : PhD

Year: 2009

Holding Libraries: Dissertation Abstracts International ;

Subject Terms: Biological sciences ; Molecular biology ; Fungi ;

Abstract:

Ascomycetes are the largest group of the Fungi constituting 40% of all described fungi. Their inconspicuous nature, diversity and complex life cycle pose challenges in the study of the group. The diversity, ecology and systematics of ascomycete fungi are still poorly known. The work presented in this dissertation analyzed the molecular phylogenetics of the Coronophorales, Hysteriales and Pleosporales and explored the relationships of taxa within the orders. The study also assessed the validity of the morphological characters currently used in the classification of the groups. Taxonomic revisions are suggested and many new taxa are added to the groups. Aspects of wood inhabiting ascomycete fungal communities in two tropical forests were also evaluated. Molecular phylogenetic analyses revealed five families in Coronophorales, Bertiaceae, Scortechiniaceae, Chaetosphaerellaceae, Coronophoraceae and paraphyletic Nitschkiaceae. The concept of Bertiaceae was expanded to include Gaillardiella while Scortechiniaceae includes all the quellk?rper bearing species. Coronophoraceae is retained separate from Nitschkiaceae for species of Coronophora . The genus Fracchiaea is polyphyletic, and Spinulosphaeria belong in the Coronophorales but of unknown affinities. Eleven new species are described in the order. Molecular analyses of Hysteriales sensu lato indicated that the hysterothecial type of fruiting body evolved at least three times within the ascolocularous fungi. A new hysterothecial bearing lineage was established within Pleosporales. Phylogenetic analyses indicated that Melanommataceae is polyphyletic as currently circumscribed. Ostropella, Xenolophium and some species of Pseudotrichia belong outside the family. Lophiostomataceae is expanded to include a new genus with morphology previously not associated with family. Trematosphaeria and Astrosphaeriella are polyphyletic as currently circumscribed, and host preference was found to be a poor predictor of relationship in the genera. Assessment of wood inhabiting ascomycete fungi sampled from two forests in Kenya revealed diverse communities comprised of few common and many rare species. Evaluation of community structuring in the study areas revealed narrow communities marked by small geographic ranges, host substrate size, and vegetation type. Since the entire community was not captured due to high diversity in the group, more studies are needed in these regions

Using remote sensing and distribution modeling to determine the habitat selection and distribution of the rare mountain bongo antelope Tragelaphus eurycerus isaaci [Kenya].

Author: Estes, Lyndon Despard

Awarding University: University of Virginia, USA

Level : PhD

Year: 2008

Holding Libraries: Dissertation Abstracts International ;

Subject Terms: Biological sciences ; Habitats ; Antelopes ; Tragelaphus ;

Abstract:

Many species may depend on restorative conservation measures to survive, including the mountain bongo Tragelaphus eurycerus isaaci, an endangered Kenyan antelope that is being restored on the Aberdares Range and Mount Kenya. The success of this international conservation project depends on understanding the bongo's ecological requirements, which is this dissertation's focus. The bongo is difficult to study because it is rare and lives in challenging terrain, necessitating a research strategy that combined field data (42 bongo, 90 non-presence observations collected in the Aberdares), remote sensing, and predictive distribution models to overcome these obstacles. Initial results showed that bongo habitat selection is shaped by micro- (0.04 ha) and patch-scale (20.25 ha) vegetation structural features. To map micro-scale vegetation structure, eight variables were summarized in a structural complexity index (SCI), which was estimated with a multiple regression model incorporating 5 RS variables derived from ASTER data (15-30 m resolution) using spectral mixture (SMA) and texture analysis (TA). This methodology was more accurate and transportable (root mean square error = 15%, R 2 = 0.46), than mapping techniques applied in similar studies. Logistic regression models (31 in total) were based on this SCI map and four other predictors. The models showed good predictive capability (73-89% accuracy). Terrain ruggedness, related to bongo security, is the best predictor, then soil moisture availability (related to browse quality), followed by distance to wildlife authority bases (security), and micro-scale vegetation structure (SCI). Edge density (a patch-scale vegetation measure) is least important. The present day bongo niche is thus found where predation is best avoided and vegetation structure is suitable. Models show that less than ~20% of the study area is suitable 'core' bongo habitat, but can increase to ~30% if security is improved. Bongo restoration should focus on the largest blocks of suitable habitat delineated by a model incorporating all 5 predictors. This dissertation provides the first assessment of bongo spatial ecology, and shows that (1) enhanced remote-sensing techniques improve distribution models, and (2) rare species ecology can be better understood by using multiple data sources to overcome data collection challenges.

Threat-sensitive behavior and its ontogenetic development in top mammalian carnivores [Kenya].

Author: Pangle, Wiline Mallory

Awarding University: Michigan State University, USA

Level : PhD

Year: 2008

Holding Libraries: Dissertation Abstracts International ;

Subject Terms: Biological sciences/Animal behavior/Lions/Wildcats/ ;

Abstract:

Animals have evolved behaviors to both detect and respond to threats in order to maximize survivorship. In my dissertation, I describe four studies that focused on inter- and intra-specific variation in threat-sensitive behaviors, with special attention to vigilance, among East African mammalian carnivores. I first evaluated the functions of vigilance behavior in adult and juvenile spotted hyenas ( Crocuta crocuta ) by observing them in various behavioral contexts and over gradients of risk. The results indicated that the main function of vigilance in hyenas is to detect inter-specific rather than intra-specific threats, as vigilance was lower when hyenas were in large than small groups, and was not affected by social rank. Vigilance was also highly context-specific, with hyenas most vigilant when nursing a young litter, and least vigilant when consuming food of high quality. Adult hyenas exhibited pronounced individual variation in vigilance. Juvenile hyenas were less vigilant than adults in all contexts and showed less consistency in their vigilance behavior. I then further explored the ontogenetic variation in vigilance apparent in the first study. I used playback experiments to evaluate age-related variation in responses by spotted hyenas to roars of their main natural predators, lions ( Panthera leo ). Both juvenile and adult hyenas moved in response to lion roars, but not to control sounds. Juveniles showed a stronger response to lion sounds than did adults. Both juvenile and adult hyenas also had stronger reactions to roars emitted by male than female lions. Thus, juvenile hyenas appear to associate certain signals with dangers, and respond accordingly. However, during ontogeny, young hyenas may need experience with danger to learn the specific environmental circumstances under which they need to be vigilant when no threat is immediately apparent. The third study assessed the lethal and non-lethal effects of anthropogenic activities by comparing vigilance in an undisturbed population of hyenas to that in one experiencing human disturbance. Proportions of deaths of known causes that were attributable to humans increased between 1988 and 2006 in the disturbed population. In addition, hyenas from the disturbed population were more vigilant during rest than hyenas from the undisturbed population, especially on days during which livestock were grazing in their territory. I assessed this livestock effect using playback experiments of cow bells. I found that hyenas from the disturbed population responded more strongly to these bells, but also to control sounds, than did hyenas from the undisturbed populations, indicating a heightened responsiveness to all unnatural sounds. The last study placed the findings from the previous studies in a comparative perspective by examining vigilance by adult members of eight sympatric East African carnivore species. Vigilance varied strongly among the eight species, and this could be attributed to variation in body size, mortality rate and sociality. In addition, each carnivore species spent about the same amount of time vigilant during rest as when feeding, but vigilance strategies differed between these activities in a way that was consistent among species. Animals generally exhibited long, infrequent vigilance bouts during rest, and short, frequent vigilance bouts when feeding

The effects of translocation on the behavior of African elephants (Loxodonta africana) [Kenya].

Author: Pinter-Wollman, Noa Michal

Awarding University: University of California, Davis, USA

Level : PhD

Year: 2008

Holding Libraries: Dissertation Abstracts International ;

Subject Terms: Biological sciences/Elephants/Loxodonta africana/Animal behavior/Ecology/ ;

Abstract:

Animals often encounter novel environments, both naturally and due to human activities. Translocations are conservation actions that introduce animals to new habitats. Animals' behaviors post-release can provide useful tools for assessing translocations' outcomes. In addition, translocations provide extraordinary opportunities for studying basic questions about the animals' behavior in novel settings that are relevant to natural life history stages, such as dispersal. Here I present the outcome of the largest African elephant ( Loxodonta africana ) translocation. In Chapter One I examine the settlement process of the translocated elephants. I show that both males and females left the release site and returned home. In addition, the exploration patterns of the elephants remaining at the release site varied greatly among individuals, and the degree to which individuals explored their new home negatively correlated with their approach distance to a human observer. In Chapter Two I provide details on the translocated elephants' demographics, behavior, and physiology, and compare them to the local resident population. The translocated elephants' behavior and stress hormones converged with those of the local population. However, the translocated elephants' death rates were higher than those of the locals and their body condition was poorer. These two first chapters use behavior to assess the outcomes of the translocation and to provide recommendations for future management actions. In Chapter Three I address basic questions in animal behavior by examining the social response of the translocated elephants to their new home. The translocated elephants preferred interacting with more conspecifics upon arrival to their new home than later, when the habitat became familiar to them, suggesting there are added benefits to sociality when a habitat is unfamiliar. Furthermore, I show that the translocated elephants preferred interacting with familiar conspecifics and not with the local residents. This social segregation dissolved over time, suggesting that elephants are able to integrate into an existing social setting. This study melds applied and basic research in animal behavior. It is the first to report on the outcomes of an elephant translocation that involves both family groups and adult males, and it successfully utilizes management actions to explore animals' behavior

Tree-grass interactions in an East African savanna : the role of wild and domestic herbivores [Kenya].

Author: Riginos, Corinna

Awarding University: University of California, Davis, USA

Level : PhD

Year: 2008

Holding Libraries: Dissertation Abstracts International ;

Subject Terms: Biological sciences/Grasslands/Trees/Herbivores/ ;

Abstract:

Savanna ecosystems--defined by the co-dominance of trees and grasses--cover one fifth of the world's land surface and are both socio-economically and biologically important. Yet, the fundamental question of how trees and grasses coexist to maintain the savanna state remains poorly understood. Furthermore, although many savanna systems are undergoing anthropogenic changes in tree cover, the consequences of these changes are not well known. In this dissertation, I address some of the gaps in our knowledge about the relationships among savanna trees, grasses, and herbivores. I used both experimental and descriptive means to address these questions in an Acacia drepanolobium dominated savanna in central Kenya. In Chapter 1, I made use of a long-term herbivore exclusion experiment to test the effects of grass competition, cattle, and wild herbivores on tree saplings. I found that, although browsing herbivores suppressed tree growth, the suppressive effects of grass competition were far greater. In Chapter 2, I built on these findings by testing the effects of grass competition on trees ranging widely in size and demographic stage. I found that trees doubled their growth when grass competition was removed, regardless of demographic stage. These results collectively overturn the long-held assumption that grass competition is unimportant in limiting tree demography in savanna systems. In Chapter 3, I examined the effects of variation in tree density on wild and domestic herbivore habitat preferences. Results of structural equation modeling suggest that wild herbivores avoid areas with high densities of trees because of poor predator visibility in those areas. In Chapter 4, I examined some of the ways in which trees affect the grass community and how these effects do or do not scale up in a landscape of varying tree densities. Together, these studies provide important new insights into the variety of consequences--mostly negative--of anthropogenic increases in savanna tree cover for both wild and domestic herbivores. From these findings I conclude that, in most cases, management activities should aim to maintain open savannas with few, scattered trees and avoid the heavy cattle grazing that promotes increases in tree cover.

Livestock and wildlife effects on the successional development of a savanna landscape mosaic in East Africa [Kenya].

Author: Veblen, Kari Elizabeth

Awarding University: University of California, Davis, USA

Level : PhD

Year: 2008

Holding Libraries: Dissertation Abstracts International ;

Subject Terms: Biological sciences/Savannas USE Grasslands/Livestock/Wildlife/Grasslands/ ;

Abstract:

In African savannas, large herbivores, along with rainfall and fire, have historically been considered key drivers of ecosystem dynamics. Recently, attention has focused on an additional driver: landscape heterogeneity, ranging in scale from small nutrient patches to large grassland-woodland mosaics. Herbivores respond to this heterogeneity, and feedbacks can help maintain landscape mosaics. I used descriptive and experimental studies to explore the development of a dominant type of anthropogenic landscape heterogeneity in Kenya, East Africa, focusing on the influence of large herbivores. First, I used chronosequence methodology to describe plant community succession associated with development of abandoned cattle corrals into long-term treeless 'glades' in a wooded Acacia drepanolobium savanna. Descriptive data showed that glades were hotspots of increased nutrient levels, improved soil texture, palatable grasses, termite activity, and herbivore use. Herbivore exclusion cages showed that herbivore use reinforced or sped the progression of succession. Second, I used a plant neighbor removal experiment crossed with herbivore exclusion in dry and wet seasons to investigate the interactive effects of herbivory and abiotic stress on plant competition and facilitation in glade plant communities. Facilitation of the early successional species, Cynodon plectostachyus , by the later successional species, Pennisetum stramineum , was highly context dependent, occurring only in the presence of herbivores in the dry season. Pennisetum was competitively dominant during wet times, opposing patterns of dry season facilitation. Thus, the relative strengths of dry and wet season interactions may help determine the overall rate of succession. Third, to test how cattle vs. wildlife affect glade development, I used a large-scale 13-year experiment that excluded different combinations of cattle and wildlife. Long-term vegetation data showed that elephants homogenized the glade landscape mosaic by suppressing growth of large trees that define glade edges. In the herbaceous community, through forage preferences, wildlife suppressed and cattle reinforced succession. Plant neighbor removals indicated that cattle addition intensified facilitation of Cynodon , but dampened facilitation of Pennisetum . Collectively, these studies indicate that large herbivores exert control over the long-term persistence of the glade landscape mosaic through their short-term and long-term effects on herbaceous and woody plant communities.

Movement decision-making in plains zebra (Equus burchelli) [Kenya].

Author: Fischhoff, IIya Reuben

Awarding University: Princeton University, USA

Level : PhD

Year: 2007

Holding Libraries: Dissertation Abstracts International ;

Subject Terms: Biological sciences ; Animal behavior ; Zebra ; Equus quagga ;

Abstract:

ABSTRACT NOT AVAILABLE

Association of interferon regulatory factor-1 polymorphisms with resistance to infection by HIV-1 in Kenyan female sex workers.

Author: Ji, Hezhao

Awarding University: University of Manitoba, Canada

Level : PhD

Year: 2007

Holding Libraries: ;

Subject Terms: Biological sciences/HIV infection/Sexual behavior/Women's studies/Gender/Prostitution/Interferon/Medical immunity/ ;

Abstract:

Resistance to Human Immunodeficiency Virus-1 (HIV-1) infection has been observed in multiple cohort studies including a female sex worker cohort established in Nairobi, Kenya. Both host genetic variations and HIV-1 specific immune responses have been described as important components correlating with resistance to HIV-1. Interferon regulatory factor 1 (IRF-1), a promoter to host immunity and also a transactivator of HIV-1, has a dual role to play in HIV/AIDS. This study reconfirmed our previous finding that 179 allele at microsatellite (MS) region in IRF-1 correlated with HIV-1-resistant phenotype in this cohort. Upon this, by near-complete gene sequencing, we demonstrated that the IRF-1 gene in Kenyan cohort was highly polymorphic. Fifty-three single nucleotide polymorphisms (SNP) (26 newly identified), 2 insertions and 1 deletion mutation were identified. We identified 35 consistent discrepancies between IRF-1 GenBank sequences and our population-based sequencing data, suggesting that the current GenBank reference sequences for IRF-1 is incomplete. The sequence of IRF-1 gene and its upstream promoter region was re-established (GenBank: DQ789232). Statistical analysis revealed that, together with 179 allele at the MS region, SNPs at 619 (A/C) and 6516 (G/T) were also significantly correlated with HIV-1 resistance. Despite their intronic locations, further functional investigations revealed that PBMCs from subjects with protective IRF-1 genotypes/haplotypes showed: (1) significantly depressed IRF-1 protein expression at both a basal expression level and in response to exogenous IFN-? stimulation or infection by an artificially pseudotyped HIV-1 construct; (2) significantly increased chances of skipping exon 2 and 3 which contain the IRF-1 start codon as well as encode the DNA binding domain of IRF-1 protein; (3) significantly decreased frequencies of skipping exon 7 and 8; (4) A clear trend of decreased efficiency of HIV-1 replication early upon infection by HIV-1, suggestive of that these cells are less competent in supporting HIV-1 replication. This study suggests that different IRF-1 genotypes/haplotypes and consequently altered expression and function of IRF-1 likely compose a significant determinant for the heterogeneity of susceptibility to HIV-1 in our Kenyan subject cohort. This study provides insight to natural immunity to HIV-1 infection and suggests that effective anti-HIV-1 strategies should target not only host immunity, but also factors important in the establishment of HIV-1 infection.