No description available.

No description available.

Four species of sea terns in the genus Sterna were studied primarily to determine how they differed in strategies used to exploit available food, and to identify factors that influenced their success in obtaining it. Where the four species coexisted during the breeding season, interspecific differences were found in feeding dispersion, dive height, immersion time, use of 'contact-dipping' and size of prey taken. These variations should alleviate competition for food, and therefore facilitate coexistence. The food-robbing behaviour exhibited by Roseate Terns on Coquet Island was examined. The intensity and success of attacks were correlated with the density of "host" terns. Fish size affected the likelihood of attack, and of robbing success. Several variables were found to influence rates of fish capture at sea. Feeding rates contained both diurnal and tidal patterns, the latter corresponding with tidal variations in the rate of fish capture in the littoral zone. In Africa, first-winter Sandwich Terns were less successful than older birds at catching fish, suggesting that foraging skill is acquired gradually. An assessment of weather factors influencing fishing success, and growth rates of chicks indicated that windspeed and/or sea surface disturbance increase to levels that optimise fishing ability of inshore-feeding terns, after which their effects become detrimental. The inimical effects of paralytic shellfish poisoning on the breeding success of terns in 1968 are described. Analysis of the composition of tern eggs demonstrated significant differences between the terminal egg and the prior egg(s) of any laying sequence. The adaptedness of terns to a variable food supply is discussed with reference to other predator-prey systems. Hypotheses for the causation and function of deferred maturity in birds and other animals are assessed in relation to the slow acquisition of foraging skills by Sandwich Terns and some other seabirds.

Regional habitat use by a species, dictated by the spatial and temporal availability of resources, influences its distribution patterns and ultimately population genetic structure. Seasonal migrations between geographically separated breeding and feeding areas, as occur in many baleen whales, can complicate these relationships. Here I try to integrate the population structure of minke whales over the whole North Atlantic with regional habitat use and behavioural adaptations to a particular summer feeding ground, the Hebrides off West Scotland. Whereas no genetic differentiation could be found between separate feeding areas as far apart as Canada, the UK and Svalbard, using microsatellites and mtDNA, the presence of two cryptic breeding populations was detected, which form mixed assemblages on feeding grounds across the North Atlantic. This implies fidelity to at least two breeding grounds irrespective of proximity to feeding areas, i.e. extensive seasonal migrations (over half the North Atlantic or more), which may require a re-assessment of current management stocks. These findings were consistent with the mobility and flexibility in habitat use and behaviour observed within the Hebrides. Results from Generalized Additive Models indicated that minke whale distribution was dependent largely on temporally variable parameters (temperature in spring, chlorophyll concentration in autumn), besides depth and, to a lesser extent, topography. However, fine-scale foraging behaviour was dictated primarily by the strength and direction of tidal currents. Distribution patterns according to environmental parameters changed through the season, but were largely consistent between the entire Hebrides (cell resolution of 4min) and a smaller core study area (2min), and over a time period of 15 years. Significantly higher sighting rates in areas of likely sandeel presence in spring, but not during the rest of the season, combined with prey samples from the core study area consisting almost entirely of sprat in August/September, indicate a switch in diet between early and late season and are consistent with the changes in habitat use. Site fidelity within the core study area was high only during periods of high feeding activity, but low at other times and between years, so that individual specializations to fine-scale feeding areas, as observed off Washington State, seem unlikely. Significant interannual changes in minke sighting rates between 2003-07, both within the core study area and over the entire Hebrides, were paralleled by changes in phytoplankton concentration, local sprat landings by the fishing fleet, and seabird breeding success and numbers counted at sea, particularly common guillemots. Auks were also the seabird guild that minke whales were most likely to associate with during foraging, taking advantage of tight bait-balls concentrated by them. The significant relationships with primary productivity make bottom-up control the most likely scenario for dictating concentrations of whale and seabird prey species in West Scotland. The ability to switch between different prey according to their availability through the season, and a distribution influenced by temporally variable parameters (temperature and chlorophyll concentration), combined with adjustments in foraging activity dependent on variable conditions at fine spatial scales (tides), enable minke whales to optimise exploitation of patchy prey concentrations.

Human-wildlife conflict is a major threat to long-term wildlife survival and to subsistence communities’ livelihoods in developing countries, particularly near protected areas. In this thesis, I use an interdisciplinary approach based on a threefold vulnerability framework to examine the specific issue of crop-raiding in Loango National Park, Gabon. First, I investigate the context of conservation at the study site, and how this limits, or intensifies, conflict over wildlife. People in Loango have an understanding of sustainability that shares common ground with modern conservation principles. However, local people resent and resist current conservation practices, which exclude local communities, threaten local environmental entitlement and thus exacerbate institutional vulnerability to crop-raiding. Next, I examine biophysical vulnerability to crop-raiding and find that elephants cause the most crop damage in Loango. Crop-raiding by elephants, when considered at the scale of the study site, follows a seasonal pattern which probably results from elephants’ use of water points. However, field isolation and surrounding forest types render some fields more vulnerable than others. Farmers use diverse deterrent methods to limit raids, but none seem effective. The lack of efficacy of deterrents stems from lack of access to labour, driven by rural exodus, which prevents their successful implementation. State mitigation strategies exist but are inadequate and ineffective. Demographic changes also make farmers increasingly vulnerable to poverty, which ultimately increases social vulnerability to crop-raiding. The consequences of crop-raiding, which span from increased food and economic insecurity to social marginalisation, create a negative spiral of vulnerability to poverty and to crop-raiding. Ultimately, spatial and social isolation are the main factors driving vulnerability to crop-raiding in Loango, and both need to be addressed. Vulnerability proves to be a very appropriate analytical framework for the holistic investigation of crop-raiding, and I recommend its use in future research on human-wildlife conflicts and in conservation.

No description available.

No description available.

This thesis represents a highly novel attempt to combine capture-recapture camera trapping, GPS telemetry and dietary analysis with anthropological techniques such as participant observation and semi-structured interviews in order to investigate leopard population density and dynamics, human-leopard conflict and the potential and effectiveness of trophy hunting as a conservation tool for leopards in the Soutpansberg Mountains, Limpopo Province, South Africa. Results from camera trapping data show that the Soutpansberg is home to a very high density of leopards (20 per 100km2). This is supported by the small home range of an adult female measured during the study (13.9 km2 95% MCP) suggesting the Soutpansberg is a prey rich area with prey densities high enough to allow leopards to live in large numbers and hold small home ranges. The dispersal movements of a collared sub-adult male indicate that the Soutpansberg may be acting as a population source for sinks beneath the mountains. High levels of human-wildlife conflict exist between leopards and landowners and leopards are frequently persecuted for perceived livestock predation although no evidence of livestock was found in leopard scats. Trophy hunting does not currently work as an effective conservation tool for leopards by providing economic incentives for landowners to reduce illegal hunting and tolerate the wider leopard population. Quotas are not based on accurate population figures of leopards from field studies, females are allowed in hunting off-take and only game farmers that own hunting farms apply for trophy hunting permits. Landowners responsible for the majority of leopard mortalities (cattle and community farmers) do not conduct trophy hunting due to their distrust of the complex and bureaucratic application process. The sustainability of trophy hunting must be improved by basing off-take on accurate population numbers, monitoring harvested populations, encouraging a wider uptake of commercial hunting and reducing illegal harvests.

No description available.

Over evolutionary time coral reefs have been exposed to the influence of diverse environmental forces which have determined their structure and function. However, the climate of the earth is changing, affecting many biological systems, including coral reefs. Through this thesis the static and dynamic environment of the Caribbean basin was characterized using remote sensing and in situ data sources. This information was used to understand how present environmental conditions have shaped reef ecosystems and how the changing climate might jeopardize them. Focusing on physical constraints that drive many aspects of coastal ecology, a region-wide categorisation of the Physical Environments of the Caribbean Sea (PECS) was developed. The classification approach is hierarchical; including a first level of 16 physicochemical provinces based on sea surface temperature, turbidity and salinity data; and a second level considering mechanical disturbance from wave exposure and hurricanes. The PECS categorisation will facilitate comparative analyses and inform the stratification of studies across environmental provinces in the region. Montastraea spp. forereef habitats have the highest biodiversity and support the largest number of ecosystem processes and services in the Caribbean. One of the aspects of the physical environment, wave exposure, was used to predict the distribution of these habitats in the Caribbean basin with high accuracy (79%). The distribution of the habitat is constrained in environments of high exposure, a pattern likely to be driven by high rates of chronic sediment scour that constrain recruitment. This approach constitutes a fast and inexpensive alternative to traditional habitat mapping and complements global efforts to map reef extent. Recent changes in temperature have impacted ecosystem function across the globe. However, the nature of the responses has depended upon the rate of change of temperature and the season when the changes occur, which are spatially variable. In the Caribbean Sea, temperature trends are highly variable in space (ranging from -0.20 to 0.54°C decade-1) and most of the warming has been due to increases in summer temperatures. The highly detailed spatial and temporal patterns assessed can be used to elucidate observed ecological responses to climatic change in the region. In the face of increased temperatures it has been suggested that reefs may become increasingly restricted to locations of naturally low thermal stress, such as upwelling areas. However, when analysing the degree to which seasonal upwelling reduces the local thermal stress experienced by corals, it is clear that upwelling areas do not always offer meaningful protection. Hypothesised areas need to be assessed individually in order to evaluate their capacity as a refuge against climate change. In this thesis large progress has been made in assessing the ocean climate of the Caribbean basin by quantifying spatial patterns and their rate of change. Although some insight into the consequences of these seascape patterns to the function and distribution of marine systems has been provided, more can be done to fully exploit the datasets produced.