Sociality represents one of the major evolutionary transitions in life: a transition from individuality to societies as complex as our own. Animals exhibit a wide variety of societies, from temporary aggregations, such as schools of fish, to complex organizations where individuals maintain stable relationships, such as cooperative groups in birds, mammals, and eusocial ants. However, the diversity of social systems and the mechanisms driving the formation of complex societies remain unclear. In this dissertation, I aim to understand a less known complex social system, a colonial cooperatively breeding bird on the African savannah, grey-capped social weavers (Pseudonigrita arnaudi). I monitored daytime and nighttime relationships among more than 600 birds in over 100 colonies across three subpopulations for five breeding seasons using an auto-tracking system. In Chapter 1, I examine the social organization of this species and test the role of kinship in the organization of the society. In Chapter 2, I focus on the inter-annual variation in the fission-fusion process of colonies and test how social factors (i.e., group membership and colony membership) and ecological conditions (i.e., rainfall) may underlie individual and group decisions about settlement of colonies. In Chapter 3, I investigate the conflict in the form of infanticide behavior (i.e., egg tossing) in this social system and test nest predation as an alternative hypothesis against a presumed hypothesis that group conflict is the cause of the tossing behavior. In sum, my dissertation provides the first detailed study of a colonial and cooperatively breeding bird with high resolution of movement at the individual level. Understanding a new social system will not only expand our knowledge of the variety of animal societies, but will also give insight into how social complexity has evolved, including our own.

The African Elephant is a key component of the savanna ecosystem. They contribute to the generation of habitat for smaller vertebrates, as well as invertebrates, by the breaking of branches or uprooting of trees. Elephants also play a role in seed dispersal, germination and sapling recruitment. All these functions are advantageous to the ecosystem if the elephant population size is acceptable for the size of the reserve and the amount of available forage. The Tembe Elephant Park covers an area of 30 013 ha and is situated in northern KwaZulu Natal. This reserve has a diversity of vegetation types and is part of the Maputaland Centre of Plant Endemism and the Maputaland-Pondoland-Albany Hotspot of Biodiversity. Elephant numbers in the park are currently high and the elephant population is still increasing. This is threatening, especially to the endemic Sand Forest communities within the park. The extent of elephant impact in Tembe Elephant Park, South Africa, was investigated and compared to data collected six years prior to the current study. Elephant impact was determined in 44 transects within nine communities across the park. Percentage canopy removal was calculated for the woody individuals found in sites and with this data the targeted size classes and species could be identified. The preferences of elephants for specific woody species were determined by three electivity indices. Elephant utilisation in Tembe Elephant Park, as reflected by percentage canopy removal, increased since 2004 as the elephant population increased. Communities that experienced high values in 2010 of elephant utilisation were the Closed Woodland 1, Mature Sand Forest, Open Woodland 1 and the Closed Woodland 3. Not only did the actual canopy volume removed by elephant increase with approximately 57%, but the total canopy volume available for browsing decreased extensively since 2004. The size classes targeted by the elephants remained approximately the same from 2004 to 2010 although the 2010 results showed that elephant canopy removal percentage increased in the large size classes. This was expected as elephants target individuals with large stem diameters. A change in the selection for woody species by elephants was clear, but the change in species preference made future projections of canopy removal problematic. Elephants seem to utilise a species at extreme levels until the species is almost extirpated, then they move onto the next target species. This routine is evident in the results as highly preferred species in 2004, with high canopy volumes available and removed, had low canopy availability and electivity ratios in 2010, consequently the elephants moved on from these species as individuals became scarce. It was clear that the structure of individuals, populations and communities were being altered, selected species were facing extirpation and composition of communities was changed through the browsing manners of elephants. Management actions should be implemented to prevent irreversible damage to the vegetation and to conserve the woody species currently under threat. / Dissertation (MSc)--University of Pretoria, 2012. / Plant Science / MSc / Unrestricted

Savanna systems are complex and dynamic in space and time. Climate, fire, herbivory and nutrients have been identified as structuring agents of savanna form and function, but their interactions and feedbacks with one another and vegetation are poorly resolved. Increasing the spatial and temporal scope of studies will help to improve this situation, as demonstrated in recent studies in the spatial dimension in particular. This study aims to investigate vegetation and Nitrogen cycling changes over time in a diverse patch mosaic landscape in Hluhluwe-iMfolozi Park to identify drivers of vegetation structure and their dynamism over time. Sediment from a 150cm core (taken using a Russian corer) was analyzed for stable ¹³C and ¹⁵N isotope abundances, and C:N ratio of soil organic matter. The base of the core was dated at 2380±40cal.Yr.BP. δ¹³C, δ¹⁵N and C:N of soil organic matter was found to be variable over time. δ¹³C followed a pattern of stable periods of distinct abundance separated by abrupt changes; δ¹⁵N and C:N underwent changes over the same periods as δ¹³C. Vegetation follows a pattern of phase and transition as predicted by resilience theory. An aquatic vegetation phase persists around 2000cal.Yr.BP to about 500cal.Yr.BP, coinciding with a warm, wet period (including the Medieval Warm Period) with an open Nitrogen cycle. A C₄ grassland phase follows alter a transition to cool, dry conditions coinciding with the Little Ice Age, and decreasing openness of the N cycle. Recent increasing C₃ vegetation and N-openness were attributed to atmospheric CO₂ increase and Nitrogen deposition respectively. Climate is concluded to be the major driver of vegetation at this site, and a combination of climate and vegetation are responsible for changes in Nitrogen availability. Findings are discussed in relation to landscape management. Multi-proxy evidence in future studies would be useful in validating the findings of this study.

Orientador: Alessandra Tomaselli Fidelis / Resumo: Sistemas savânicos são compostos por espécies herbáceas, principalmente gramíneas C4, as quais se expandiram há milhões de anos atrás, alterando a ocorrência de fogo nas regiões sub e tropicas do globo terrestre. Assim sendo, em sistemas como o Cerrado, onde o fogo está presente há pelo menos 4 milhões de anos, as espécies selecionadas por este fator possuem atributos inflamáveis que contribuem para a propagação das chamas. A essa capacidade que diversas espécies possuem de entrarem em combustão e serem consumidas, chamamos de inflamabilidade, sendo um componente essencial dos sistemas inflamáveis, contribuindo para o regime de fogo do ambiente, a partir de fatores ambientais, como a sazonalidade, e composição de espécies. Sendo assim, este trabalho teve como objetivo compreender a inflamabilidade das espécies herbáceas de ambientes savânicos do Cerrado, bem como entender quais são os grupos e os atributos vegetais que mais influenciam a inflamabilidade do sistema de acordo com a sazonalidade do ambiente. Diferentes espécies de herbáceas, arbustos e gramíneas foram coletadas em áreas de campo sujo do Cerrado durante a estação chuvosa e ao longo da estação seca (começo, meio e fim). Medições dos atributos de inflamabilidade (temperatura máxima, taxa de queima e biomassa consumida) e morfofisiológicos (biomassa morta, teor de umidade e área específica foliar) dessas espécies foram realizadas durante tais épocas, afim de compreender se existia variações na inflamabilidade. Além ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Savanna ecosystems are essentially covered by herbaceous species, mostly C4 grasses, which have a huge expansion million years ago, altering the fire occurrence in the sub and tropical regions of the world. Therefore, fire-prone ecosystems as the Cerrado, have fire present about 4 million years ago, which selected species with flammable traits enhancing the flames propagation. That capacity that several species possess to be consumed and spread the fire is called flammability, which is an essential component of flammable systems, contributing to fire regime, together with environmental factors, as seasonality and species composition. Thus, this study had the main aim understand the flammability of herbaceous species of the Cerrado open savannas physiognomies, besides understand which are the species groups and traits that most influence the system flammability, according to seasonality. Different species of forbs, shrubs and graminoids were collected in areas of Cerrado campo-sujo during the wet season and over the dry season (early, mid and late-dry). Flammability (maximum temperatures, burning rate and burnt biomass) and morphophysiological traits (dead biomass, moisture content and specific leaf area) measurements were taken across seasons, to understand the flammability changes. Moreover, 21 grass species were also collected in the middle of the dry season in two different regions of Cerrado campo-sujo, where the same traits were measured, to evaluate the variability of f... (Complete abstract click electronic access below) / Mestre

No description available.

The Ethiopian Wildlife Conservation Organization has little information on the lll extent and ecological determinants of plant species composition and distribution in Omo National Park. Elsewhere, the determinants of African savanna vegetation dynamics have been the focus of numerous investigations, yet our understanding of the hierarchical nature and relative importance of any relationships remains very general. As well, our ability to derive predictions about vegetation responses is limited to extreme generalizations. African savanna landscape ecotones have received even less attention than most landscapes. In this dissertation, I test hypotheses about plant species distribution-determinant relationships in Omo National Park, a park that occurs in a landscape ecotone. Determinants investigated include rainfall and topographic-related gradients in soil moisture and edaphic conditions, and availability of soil constituents. Rainfall pattern was determined from meteorological data and multiple linear regression. Topographic attributes were measured in the field. Availability of soil constituents was determined by evaluating and using spatial interpolation models using limited soils data, and construction of surface soil maps. Hypotheses were tested using the simple and partial Mantel tests of matrix association. Results demonstrate that predictions using spatial interpolation models based on limited, coarse-scale soils data are accurate and reliable when compared with more data-intensive investigations. Results using spatial statistics indicate that the nature of the spatial pattern of perennial species associations is a monotonic spatial trend. The distribution of perennial species associations is influenced both directly or indirectly by rainfall. An indirect rainfall relationship occurs when there is variability in topography. The means of influence by the topographic-related attributes is unclear despite significant Mantel results. In the topographically invariant portion of the study area, however, exchangeable sodium and magnesium concentrations appear to indirectly influence the distribution of perennial species associations. Strength and ordering of the vegetation-determinant relationships varied depending on the type of perennial species association type being investigated. Differences in species range of tolerance and rate of change in species association, depending on association type, landforrn, and parent material differences, account for the nature of the vegetation-determinant relationships, the ordering of the determinants, and variability in responses.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21164号 / 農博第2290号 / 新制||農||1060(附属図書館) / 学位論文||H30||N5138(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 舟川 晋也, 教授 縄田 栄治, 教授 北山 兼弘 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science. Johannesburg 1990. / No abstract provided.

The Yellow Rail (Coturnicops noveboracensis) is a migratory nongame bird of high conservation priority throughout its entire range. The objectives of this study were: (1) assess Yellow Rail occupancy in the context of prescribed fire regime in pine savanna habitats of Mississippi and Alabama and (2) assess Yellow Rail habitat use in pine savanna habitats of coastal Mississippi. Yellow Rail occupancy decreased significantly with time since fire and increased with grassland patch size. Throughout the study area Yellow Rail maintained small (mean = 3.37 ha) home ranges aggregated within study areas, indicating suitable habitat may be limited. Yellow Rail used areas dominated by Aristida stricta and Carex spp. They used locations with lower woody percent cover, greater herbaceous height structure and lower frequency of trees than locations outside their home range. This research highlights the continued need to prioritize conservation and management of open grasslands and pine savanna habitats.

Declining bat populations necessitates a need to understand how different land management techniques influence bat activity. This study assessed the influences of different coastal upland habitat management techniques, such as mulching, prescribed fire, and select cut, on forest bat activity within the Grand Bay National Wildlife Refuge and National Estuarine Research Reserve. Acoustic recorders were used to monitor bat activity and insect and vegetation surveys were used to assess influences on bat activity across different land management techniques. Results demonstrate that overall bat activity was similar across different land management techniques, however larger species adapted for open-space flying were shown to be less active within dense forest such as the select cut technique areas. Findings from this study suggest that various land management techniques can influence bat activity differently.