The water shrew Neomys fodiens is one of Britain’s least known mammals and its habitat requirements are poorly understood. The purpose of this study was to determine occurrence and associated habitat preferences of water shrews, a species of conservation concern, by comparing populations in central England freshwater habitats. Bait tube surveys were undertaken at 32 freshwater sites to establish water shrew presence, half of which were found to contain water shrews. Habitat surveys were undertaken and, in addition to water shrew presence/absence data, were used to develop habitat suitability index models by means of artificial neural networks. Management intensity (occasional or frequent bankside management) was identified as the most important predictor of water shrew presence and, when combined with dissolved oxygen (0-2.99mg l-1) and water depth (<25cm), created the highest performing model. These models will allow sites to be rapidly assessed for water shrew presence without labour intensive and costly live-trapping techniques. Prey availability was investigated by undertaking invertebrate surveys at four water shrew-positive sites, as well as at an additional four sites with unknown water shrew presence with which to compare. Overall, there was no significant difference between the total numbers of terrestrial and aquatic invertebrates at sites with known/unknown water shrew presence although there were differences in composition of potential prey. POPAN abundance of water shrews was estimated, and its relationship with other small mammal species investigated, using live trapping at the four water shrew positive sites. Negative relationships were found between water shrews and the terrestrial shrew species although these were not significant. Individually identifying captured water shrews using traditional fur-clipping marking methods is difficult. Therefore, buccal swab samples were taken to identify individuals via genetic profiling. Determining numbers of water shrews via genetic profiling was found to be more accurate than through fur-clipping which overestimated populations. Furthermore, buccal swab sampling is a new, minimally invasive method of identifying individuals which can be used to give accurate information about water shrew population densities and dynamics across seasons. This is the first in-depth study of factors affecting the occurrence and habitat selection of water shrews in central England and has made some important contributions to the understanding of habitat analysis and species identification.

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The UK population of hedgehogs (Erinaceus europaeus) has halved in rural areas between 2005 and 2015, and hedgehogs select urban areas over arable land. Explanations for the unsuitability of arable land for hedgehogs include: high predation risk by badgers (Meles meles), low prey densities, cold microclimates and low availability of nest sites. I investigated the reasons for hedgehog avoidance of arable land by measuring hedgehog habitat use, ranging behaviour, daily energy expenditure (DEE) and diet along a gradient of habitats from rural villages to arable farmland, under varying predation threat and temperatures. I also examined which factors affected hedgehog presence and abundance nationally. Hedgehogs preferentially selected urban habitats for both foraging and nesting, including gardens and buildings. A hedgehog's mean distance to buildings over a season was positively correlated with home range size and DEE, conceivably due to higher prey availability in rural villages and the need for increased movement on arable land to achieve sufficient food intake. I found little evidence that the prey taxa hedgehogs consumed changed along the gradient from buildings to arable land, although all hedgehogs consumed pet food, suggesting that supplementary feeding is one reason hedgehogs are attracted to buildings. On sites where badgers were present hedgehogs stayed closer to edge habitats and buildings, had smaller home ranges, spent less time on arable land, and had a lower DEE. Badger presence is one likely cause of hedgehogs' avoidance of arable land and their selection of rural villages, where badgers are found at lower densities. Nationally, badger abundance and fox (Vulpes vulpes) abundance was negatively associated with hedgehog abundance. Landowners on farms under Higher Level Stewardship (HLS) were more likely to report having seen hedgehogs than landowners on farms not under HLS. I conclude that rural villages are a key habitat for sustaining hedgehog numbers in the countryside and the connectivity between these island populations should be enhanced through the implementation of agri-environment schemes. Higher-tier schemes may also increase habitat complexity, which could potentially reduce the predation pressure from badgers, as well as enhancing hedgehogs' invertebrate food supply.

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All five species of British shrews (Sorex araneus, S. minut, Neomys fodiens, Crocidura suaveolens and C. russula were studied with the emphasis being placed on the commoner species. The population dynamics and seasonal fluctuations in numbers of S. araneus and S. ininutus were investigated. A seasonal cycle of captures of S. araneus was demonstrated, with peaks of occurrence in summer, low numbers in winter and a re-emergence of high numbers in spring. Closer study indicated a great mortality of old adults and. juveniles in autumn which commenced before the onset of harsh weather conditions, but overwintering survival of remaining shrews was high. Home ranges and activity of S. araneus appeared to be reduced in winttc. A study of food availability aid diet of S. araneus, S. ininutus and N. fodiens showed major prey items to include adult coleopterans, insect larvae, araneids, isopods and lumbrlcids which occurred In large numbers throughout the year; no decrease in numbers or biomass of prey was found to account for the decrease in body weight of shrews in autumn and winter aid their apparent decline in numbers. Food consumption of shrews ranged from 4 of the body weight daily for C. suaveolens to i6 for S. minutus, but was not directly related to body weight within a species. Conaurnption by S. araneus was reduced at low temperatures. Studies of fat storage by wild. shrews showed no great seasonal differences, although captive shrews ac.cumirulated fat in warm conditions. Studies on the foraging and burrowing behaviour of S. araneu3 showed that they are generally poor burrowers but that they are able to recover insect pupae buried up to 120mm deep in soil. It is sugges ted. that overwintering shrews adopt a more subterranean existence, spending longer periods in the nest to conserve body heat aid less time foraging. Mortality due to increased. predation in autumn, aid reduced activity on the ground surface probably account for low numbers of captures in winter.

Potential alterations of host and parasite ranges are likely with climate change so an understanding of the host traits and ecological factors that can influence host-parasite interactions is vital for the effective protection of ecosystems. Accidental introductions of non-native species can place elevated stress on native ecosystems so that the examination of key species can act as early warning systems. The Eurasian otter, Lutra lutra¸ is a top predator and sentinel species for the health of European freshwater ecosystems and is therefore a suitable model for exploring parasite fauna introductions. In this PhD, the patterns and processes that define macro-parasitic infections were explored using evidence from post-mortems of 587 otters. Specifically, the invasive status of two helminths (Pseudamphistomum truncatum and Metorchis albidus: Trematoda; Opisthorchiidae) was investigated, both species having been identified in the UK otter populations for the first time within the last 10 years. Genetic variation, however, was similar across Europe indicating neither helminth is likely to have been a recent introduction to the UK., The distribution of both helminths as well as the only ectoparasite, Ixodes hexagonus (Arthropoda; Ixodidae), recovered from UK otters, were associated with abiotic factors, particularly temperature. The complexity of the parasite life cycles was investigated; otters act as a definitive host for both helminth species considered in this thesis and early stage intermediate hosts were identified for P. truncatum as the snail Radix balthica and the roach Rutilus rutilus. Metacercariae of M. ablidus were detected on chub (Leuciscus cephalus), rudd (Scardinius erythrophthalmus) and roach. Parasite aggregation and parasite fecundity of the P. truncatum populations were influenced by abiotic factors, region and season, whilst P. truncatum abundance was defined better by the biotic factors host age-class and condition demonstrating how multiple factors combine to produce parasite population dynamics in wild fauna. Ultimately, the data collated throughout this PhD was used to parameterise a susceptible-infected Susceptible-Infected (SI) model describing the host population dynamics of opisthorchiid trematodes. This model is applied to the P. truncatum system to examine which factors might determine the proportion of hosts that become infected.

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