Water vole (Arvicola amphibius) ecology was studied at the National Wetland Centre Wales (NWCW), a National Key Site for water voles, consisting of a diversity of interconnected habitats, including ponds, ditches and reed-beds. A novel method of mapping the vegetation of the wetland landscape was devised, using patches of vegetation classified according to the dominant vegetation type (DVT). The richness and abundance of DVT patches was used as an index of diversity at the habitat level. This provided a basis for describing the matrix habitat, which underpins the study of water vole ecology at the patch-landscape scale. The practical application of the DVT mapping approach allows the stages of wetland succession to be monitored, identifies areas of high biodiversity and provides a baseline on which to monitor the distribution and movements of animal species. Implementation of this method reduces time and the need for specialist field surveyors, thereby facilitating efficient management practices if applied at a national level. An intensive four year study of a metapopulation of water voles on eight adjacent ponds in the NWCW wetland reserve revealed an important insight into the dynamics of wild populations in complex, non-linear habitats. Multi-annual fluctuations in population densities were observed, characterised by a peak density phase and a low density phase. Density dependent juvenile dispersal was characteristic of the water vole population. Female water voles in diverse pond habitats maintained intra-sexually overlapping home ranges, uncharacteristic of this species. During the breeding season, water voles selected the ponds with the highest habitat diversity (assemblage of DVTs) but were typically associated with the least diverse DVT patches within the vegetation mosaic. Temporal plasticity in niche partitioning was observed both between genders and between individual female water voles at NWCW. During the winter. Bramble (Rubus fruticosus) was the most important dominant vegetation type, providing a source of cover and protection from predation. Water voles selected 23 plant species (and 3 non-plant species) as food. Soft Rush (Juncus effusus) a species with high nitrogen and calorific content was favoured particularly. The physical effects of water vole grazing and burrowing, combined with the large amounts of nitrogen- containing faeces deposited in latrines and underground burrows, has implications for wetland nutrient cycles. The effects of large scale vegetation clearance are described and holistic management recommendations are presented.