No description available.

Oystercatchers Haematopus ostralegus and cockles Cerastoderma edule were studied with the aim of understanding the behaviour of predators and the consequences which this behaviour has on the cockle population. At Traeth Melynog, Anglesey, the cockle density declined down the shore and those at the bottom were larger, older and heavier than those at the top. This pattern was caused by the spat settling at the top of the shore combined with downshore movement of some cockles. As a consequence, both flesh content and size were correlated with prey density. The profitability (flesh eaten per minute handling time) of cockles increased with their size. According to optimal foraging theory, these larger ones should therefore have been preferred, and this proved to be so. The rate at which oystercatchers ate cockles followed a type II functional response. The plateau was not caused solely by handling time, nor were satiation or interference important. Analysis of the functional responses of other birds feeding on one prey species showed that in each case the behaviour also conformed with a type II distribution yet neither handling time nor satiation appeared responsible. To account for this, a theoretical model was developed which generates type II functional responses from optimal foraging theory. Another model was developed which predicts the aggregative numerical response for a given level of interference. Because of correlations between density, size and flesh content within the cockle population at I Traeth Melynog, this model could not be directly applied to the data. But the basic assumption of the model - that oystercatchers obeyed the ideal free distribution - could be tested. It gave a poor fit to the data. There was little measurable interference between oystercatchers feeding on cockles. The number of oystercatchers on the Ribble fluctuated in parallel with the cockle population. Much of this change appeared to be due to an influx of young birds. This suggests that young birds seek a suitable estuary whilst adults tend to return to the one found whilst young. Thus the change in oystercatcher numbers was an aggregative numerical response rather than a population numerical response. Due to correlations within the cockle population at Traeth Melynog, profitability reached a maximum value at 25-100 cockles per m2. Therefore the oystercatchers concentrated their feeding at these relatively low cockle densities. As a result, cockle mortality due to predation by oystercatchers was inversely density dependent over most of the range of densities. However, since cockle movement took place, this pattern of mortality could not be detected in the cockle population.

No description available.

Using spawn collected from the north Merseyside sand dune system, the effects of temperature on growth, development, metabolism and metamorphosis in B. bufo and B. calamita tadpoles were investigated, together with a limited study on the effects of L-thyroxine. The effects of density on growth, developteI1t and metamorphosis were examined. Physiological and behavioural effects of B. bufo tadpoles on B. calamita tadpoles were also studied. B. calamita spawn and tadpoles survive at higher temperatures than B. bufo. Below20°CB. bufo spawn, and below 15°Ctheir t.adpcl.es, develop at a greater rate than B. calamita. B. calamita spawn and tadpoles' growth and development is faster at higher temperatures. B. calamita tadpoles have higher metabolic rates than B. bufo across the temperature range 15-30°C. Faster rates of metabolism and development in B. calamita result in smaller tadpoles and toadlets than B. bufo. B. calamita may compensate for this with increased metamorphic efficiency in terms of energy. It is speculated that differences in tadpole thyroid physiology could account for observed differences. metamorphic efficiency was greatest, and rates of development and growth maximised/at the tadpoles' preferred body temperature. Increased density reduced growth-and developteI1t of tadpoles, but influenced different stages in the two species. metamorphosis in all B. bufo tadpoles was delayed, whereas in B. calamita a proportion of the population metamorphosed apparently unaffected by increased density. The responses of tadpoles to temperature and density were related to the species' preferred spawning environments. In the presence of B. bufo tadpoles, B. calamita growth, development and metabolism was suppressed. The pattern of development and timing of metamorphosis in B. calamita became similar to that of B. bufo. Inhibition was not relieved by L-thyroxine, and did not effect tadpole behaviour. Mass specific food consumption was increased. It is speculated that the inhibitor is a parasite or a substance which affects assimilation.

Although the value of primary forests for biodiversity conservation is well known, the potential biodiversity and conservation value of regenerating forests remains controversial. Many factors likely contribute to this, including: 1. the variable ages of regenerating forests being studied (often dominated by relatively young regenerating forests); 2. the potential for confounding on-going human disturbance (such as logging and hunting); 3. the relatively low number of multi-taxa studies; 4. the lack of studies that directly compare different historic disturbances within the same location; 5. contrasting patterns from different survey methodologies and the paucity of knowledge on the impacts across different vertical levels of rainforest biodiversity (often due to a lack of suitable methodologies available to assess them). We also know relatively little as to how biodiversity is affected by major current impacts, such as unmarked rainforest roads, which contribute to this degradation of habitat and fragmentation. This thesis explores the potential biodiversity value of regenerating rainforests under the best of scenarios and seeks to understand more about the impact of current human disturbance to biodiversity; data comes from case studies from the Manu and Sumaco Biosphere Reserves in the Western Amazon. Specifically, I compare overall biodiversity and conservation value of a best case regenerating rainforest site with a selection of well-studied primary forest sites and with predicted species lists for the region; including a focus on species of key conservation concern. I then investigate the biodiversity of the same study site in reference to different types of historic anthropogenic disturbance. Following this I investigate the impacts to biodiversity from an unmarked rainforest road. In order to understand more about the differential effects of habitat disturbance on arboreal diversity I directly assess how patterns of butterfly biodiversity vary between three vertical strata. Although assessments within the canopy have been made for birds, invertebrates and bats, very few studies have successfully targeted arboreal mammals. I therefore investigate the potential of camera traps for inventorying arboreal mammal species in comparison with traditional methodologies. Finally, in order to investigate the possibility that different survey methodologies might identify different biodiversity patterns in habitat disturbance assessments, I investigate whether two different but commonly used survey methodologies used to assess amphibians, indicate the same or different responses of amphibian biodiversity to historic habitat change by people. The regenerating rainforest study site contained high levels of species richness; both in terms of alpha diversity found in nearby primary forest areas (87% ±3.5) and in terms of predicted primary forest diversity from the region (83% ±6.7). This included 89% (39 out of 44) of the species of high conservation concern predicted for the Manu region. Faunal species richness in once completely cleared regenerating forest was on average 13% (±9.8) lower than historically selectively logged forest. The presence of the small unmarked road significantly altered levels of faunal biodiversity for three taxa, up to and potentially beyond 350m into the forest interior. Most notably, the impact on biodiversity extended to at least 32% of the whole reserve area. The assessment of butterflies across strata showed that different vertical zones within the same rainforest responded differently in areas with different historic human disturbance. A comparison between forest regenerating after selective logging and forest regenerating after complete clearance, showed that there was a 17% greater reduction in canopy species richness in the historically cleared forest compared with the terrestrial community. Comparing arboreal camera traps with traditional ground-based techniques suggests that camera traps are an effective tool for inventorying secretive arboreal rainforest mammal communities and detect a higher number of cryptic species. Finally, the two survey methodologies used to assess amphibian communities identified contrasting biodiversity patterns in a human modified rainforest; one indicated biodiversity differences between forests with different human disturbance histories, whereas the other suggested no differences between forest disturbance types. Overall, in this thesis I find that the conservation and biodiversity value of regenerating and human disturbed tropical forest can potentially contribute to rainforest biodiversity conservation, particularly in the best of circumstances. I also highlight the importance of utilising appropriate study methodologies that to investigate these three-dimensional habitats, and contribute to the development of methodologies to do so. However, care should be taken when using different survey methodologies, which can provide contrasting biodiversity patterns in response to human disturbance.

Heart rate (f\(_H\)) and rate of oxygen ( V\(_{O2}\) consumption were recorded from adult macaroni penguins while exercising on a treadmill. No differences were found in the relationship between f\(_H\) and V\(_{O2}\) in breeding and moulting female penguins, but a significant difference was found between male and female penguins. These relationships were used to estimate field metabolic rate (FMR) for free-ranging female penguins, which were implanted with heart rate and temperature data loggers. While foraging to provision their chick, FMR was 8.92 ± 0.44 W kg\(^{-1}\) and 9.07 ± 0.42 W kg\(^{-1}\) respectively while at-sea during the brood and crèche phases of the breeding season. While on-shore, the FMR was 6.08 ± 0.43 W kg\(^{-1}\) and 5.64 ± 0.40 W kg\(^{-1}\) respectively for the brood and crèche phases. During their moult fast, male and female penguins showed a pattern of increasing and then decreasing FMR and females had a mean FMR of 5.25 ± 0.88 W kg\(^{-1}\). The peak of energy expenditure was associated with maximum feather loss, probably due to increased costs of thermoregulation. During natural diving, penguins showed complex fluctuations in heart rate. Abdominal temperature fell during dive bouts with the magnitude of this decline increasing with bout length. Put together, these adjustments in heart rate and circulation may be enough to enable all natural dives to be aerobic in nature.

Studying different types of dental pathology, wear, and developmental defects can allow inferences into diet and behaviour in a variety of ways. In this project data on these different variables were collected for South African hominins and compared with extant primates. The species studied include Paranthropus robustus, Australopithecus africanus, A. sediba, early Homo, Homo naledi, baboons, chimpanzees and gorillas. Macroscopic examination of each specimen was performed, with a 10X hand lens used to verify certain pathologies. Variables recorded include antemortem chipping, enamel hypoplasia, caries, occlusal wear, tertiary dentine, abscesses, and periodontal disease. Clear differences in frequencies were found in the different South African hominin species. Homo naledi displays high rates of chipping, especially small fractures above molar wear facets, likely reflecting a diet containing high levels of contaminants. Other noteworthy results include the high levels of pitting enamel hypoplasia in P. robustus molars compared to other species, likely due to a species-specific enamel formation property or developmental disturbance. The low rates of chipping in P. robustus does not fit with this species being a hard food specialist. Instead, the wear best supports a diet of low-quality tough vegetation. Australopithecus africanus likely had a broad diet, with angled molar wear, lack of caries, and high chipping frequencies supporting this conclusion. Seven new carious lesions are described, two from H. naledi and five P. robustus. Other, rarer, pathologies are also highlighted, including abscesses in an early Homo individual, root grooves caused by erosive wear in A. africanus and a case of amelogenesis imperfecta in a female chimpanzee. The main conclusion from this thesis as a whole is the substantial difference in frequencies of the different variables among hominin species, supporting the proposition that their diets differed substantially.

In this thesis are described the populations of waders (Aves: Charadrii) occurring on the Ribble Estuary, Lancashire, special reference being made to the eleven species comprising the bulk of the shore wader population. The daily routine of these birds is described including the time spent in feeding. The feeding areas are described together with the foods taken from gut and pellet analysis and direct observation. The distributions of invertebrates, and especially those of major importance as wader food, are described as well as the factors affecting these distributions. Variations in density of prey in relation to O. D., general geography of the estuary, and time of year are included. Depth distribution and variations in prey size are outlined for the main species. Food intake was studied in the eight main waders. Daily intake through the year is described. in relation to energy requirements. Variations of feeding rates with several factors are included. All data are combined to enable calculation of the total biomasses of the main prey taken by waders in the course of a year. These are compared with total minimum annual production of the prey. Future work, including a computer study based on these and extra data, is outlined.

Leishmania parasites are digenetic protozoans which infect human hosts and are causative agents of a series of diseases known under the name of leishmaniasis. Macrophages represent the main host. Hence the interaction between Leishmania and macrophages is a fundamental step in the development of the disease. Many studies have been undertaken to understand early stages of the parasite interaction with macrophages; however, few have investigated the later stages of infection. This study was undertaken to develop an experimental model to examine the fate of the parasites when they leave the safe environment represented by their host macrophage. Primarily, the study investigated how Leishmania spread to neighbouring cells without being recognized and killed by the immune system defences. Three Old World species of Leishmania parasites: L. aethiopica, L. major and L. tropica, all responsible for the cutaneous form of the disease, were used. A model of infection was described using two cell lines well known for supporting infection: THP-1 and U937. Axenic amastogotes for L. aethiopica parasites were obtained and used to identify drugs active against the infection. On the basis of the information available in the literature, a model was suggested involving interaction of intracellular parasites with the host cells’ apoptotic machinery. Specifically it was suggested that Leishmania parasites were able to induce incomplete activation of apoptosis in the host cells. This hypothesis was confirmed by the findings that during infection an increased number of host cells showed two features associated with early apoptosis but not the one associated with the later stage. Results were validated in peripheral blood derived human macrophages. The information obtained from comparative proteomics analysis of the infection confirmed that Leishmania regulates apoptotic processes. On the basis of the results obtained a model was presented to explain how induction of apoptosis allows intracellular amastigotes to spread unrecognised to uninfected macrophages without inducing an inflammatory response or losing the host cell’s protection.

Farmland birds in Europe have declined as agriculture has intensified, with granivorous specialists disproportionately affected. Despite grassland based farming being widespread, farmland bird research to date has focussed on mixed and arable farms. Yellowhammers are a red-listed species in the UK. This study investigated year round habitat requirements, diet, and movements of yellowhammers at four grassland dominated farms in Ayrshire, Scotland. Data were obtained via field surveys and trials, radio-tracking and faecal analysis. Fine scale breeding season foraging habitat requirements were studied by comparing invertebrate and vegetation communities at foraging sites with paired controls across all four farms. A small scale winter supplementary feeding trial was conducted on one farm. Breeding yellowhammers were distributed throughout the study sites; average density was low at 0.11 pairs per hectare (range 0.06 to 0.15), half the densities reported in arable and mixed regions. Yellowhammers preferentially foraged within 10m of field margins. Grassland summer foraging sites contained significantly higher invertebrate diversity and more large invertebrates than control sites. Faecal analysis revealed that adults ate significantly more cereal than nestlings, with both including more invertebrate material than observed in previous studies. Diptera, Coleoptera and Araneae were key orders, with Lepidoptera larvae additionally important for nestlings. A low proportion of cereal was found in nestling diet, suggesting that the invertebrate dominated diet provided was of high quality. In contrast to summer diet, and despite grassland being the dominant habitat, cereal dominated winter diet; grass seeds and invertebrates accounted for <1% of diet in winter. Winter yellowhammer density at each farm was positively correlated with stubble availability. Radio-tracking found yellowhammers significantly selected stubble in early winter and game managed habitat in late winter. Supplementary feeding attracted an estimated 247 to 267 yellowhammers at a site where the previous year’s winter surveys recorded only 5 birds despite holding a good breeding population. Survival rates of 1st years at the supplementary fed site appeared higher than elsewhere in the landscape, and a small increase in breeding density was observed post feeding. As winter progressed, the use of the grain provided increased, suggesting that the late winter period was the most crucial time for the birds regarding food supply. Providing supplementary food represents a cheap and easy solution that could be utilised by agri-environment schemes to tackle late winter farmland bird food shortages. Alternatively, increasing winter stubble in grassland dominated regions should provide additional biodiversity benefits associated with increased landscape heterogeneity as well as increased winter food availability. This study highlights differences in breeding density, habitat selection, movements and diet of yellowhammers on grassland farms compared to arable and mixed farm populations. Restricted winter stubble habitat limits winter food availability, and hence the likely overall size of the population able to subsist in this habitat.