Conservation biologists require information on the distribution, ecology, behaviour and genetic diversity of endangered species in order to identify threatened populations, determine which mechanisms are driving populations closer to extinction, and design appropriate mitigating solutions. The hazel dormouse, Muscardinus avellanarius, is declining across much of its northern range. Dormice are detrimentally affected by habitat degradation, loss and fragmentation. Despite extensive studies and conservation work on hazel dormice, there remain many gaps in our understanding. This thesis aims to fill some of those gaps. Hazel dormice are elusive, and therefore difficult to monitor in the wild. I demonstrate the utility of novel monitoring techniques for the rapid determination of dormouse presence, and provide algorithms for the objective verification of species identity from small mammal footprints. I design and utilise genetic microsatellite markers to investigate molecular ecology in this species. In one of the first studies of hazel dormouse population genetics, I describe high levels of population differentiation and genetic isolation across the southwest UK range. I find a powerful signal of reduction in genetic diversity, and an increase in differentiation between core and peripheral populations. I consider rival hypotheses for the mechanisms driving this population genetic pattern, and place the results in the context of conservation strategies for UK dormice. Further, I use molecular data to investigate the prevalence of multiple paternity in wild dormouse populations. Results contradict a recent estimate of very high rates of polyandry, but remain high at 50%. I investigate the effect of food availability on the hibernation behaviour of dormice. My findings, which demonstrate dormice are variable and flexible in their response to winter diet, increases our understanding of the trade-offs dormice must make in order to survive winter periods. I hope that the research undertaken for this thesis will add to the understanding and conservation of an iconic British mammal, ultimately contributing to the persistence of this species.

Tyrimo metu buvo analizuoti didžiųjų miegapelių (Glis glis L.) poreikiai buveinėms, nustatytos joms potencialiai tinkamos gyventi vietos devynių radimviečių miško masyvuose Lietuvoje, įvertinta radimviečių būklė. Rezultatai parodė, jog didžiosioms miegapelėms Lietuvoje svarbios dviejų tipų buveinės: Šc, Šd augavietėse augantys įvairiarūšiai lapuočių medynai su liepomis, klevais, guobomis, pavieniais ąžuolais, ir gausiu įvairių rūšių traku bei Nc, Nd augavietėse augantys brandūs pušų-ąžuolų-eglių medynai su liepomis, beržais ir lazdynų traku. Visuose radimviečių miško masyvuose kartu sudėjus nustatyta 2790,5 ha didžiųjų miegapelių potencialių gyvenamųjų vietų, kai žinomų radimviečių plotas – 179,5 ha. Daugumos radimviečių būklė vidutinė, dviejose – Punios šile ir Strošiūnų miške – gera, bloga būklė nenustatyta nei vienoje. / In this study habitat requirements of fat dormouse (Glis glis L.) were analyzed, in wood plots of the current 9 fat dormouse localities potential living places were identified and state of localities was assessed. Results showed, that most important areas for fat dormouse were in two wood stands: miscellaneous deciduous woods with lime, maple, elm, single oak, abundant and species-rich understorey, growing on skews in normal humidity, fertile and very fertile soils, and other one – high pine-oak-spruce woods with lime, birch and hazel understorey, growing in normal humidity, fertile and very fertile soils. In all localities 2790.5 ha of potential living places were determined, while the area of current known localities is only 179.5 ha. Most of the known localities are in a average state, while only 2 localities in Punia and Strosiunai are in good state.

The extent and quality of forested habitats have changed across Europe and as a result many forest species have suffered declines and range contractions. European legislation has been introduced to conserve those species that have been negatively impacted by widespread land-use changes. In order to assess the needs of declining species and the efficacy of these protective measures, the effects of habitat type, configuration and management on individuals and populations needs to be understood. In this thesis, I have investigated patterns and drivers of variation in the status of populations of hazel dormouse Muscardinus avellanarius in the United Kingdom. I have assessed the effects of variation in habitat on hazel dormice at multiple spatial scales, and related this to woodland management.