The declines of the brown hare (Lepus europaeus), a priority species for conservation in the UK, may have been caused by changes in agricultural management. This study aims to identify hare distribution, density, habitat selection and demography in grass lands in order to benefit their future conservation. In addition, this study aims to investigate the impact of current agricultural management on the populations of the European wild rabbit (Oryctolagus cuniculus), a major agricultural pest and potential competitor for hares. Hare and rabbit populations were surveyed in several large, pasture-dominated, sites in north -east England between 2007 and 2009. Estimated density of brown hares in the studied region was far higher than the published national average density for this species in pastures but with very large variation between superficially similar sites. We explored a new method to survey hares using night-time line transect distance sampling and compared this method with day time surveys. Night-time distance sampling produced improved precision estimates of hares with considerably less survey effort by maximising detectability during surveys. Hares and rabbits had different habitat requirements in grassland areas and areas dominated by intensive sheep grazing produced the lowest hare densities and in most cases were associated with high rabbit densities. Field size was an important determinant of the distribution of both hares and rabbits but with contrasting effects for the two species. Predator control appeared more important in increasing rabbit numbers than hares in the studied region. Our results indicate that recent changes in pasture management in the UK might favour high rabbit densities with potentially significant economic impacts for the agricultural sector. Hare productivity was high but female fertility and survival, in particular juvenile survival, were relatively low. Hares in the studied region were generally in good condition and reached sizes comparable with hares from arable areas. Population modelling suggested the hare population in the area was slowly increasing but was susceptible to decline even at relatively moderate levels of hunting. Radio-tracking indicated that habitat heterogeneity was important for hares at both between and within field levels. Hares preferentially used field margins during both active and inactive periods and selected woodland edges and unimproved grassland during diurnal periods, suggesting that they might benefit from measures designed to increase heterogeneity and re-establishment of non-farmed habitat features, particularly field margins. Equally, hares avoided sheep grazed fields with short swards for both foraging and resting indicating that reducing grazing intensity in pastural areas would also be beneficial for hare conservation. We suggest that grassland management could be adapted in order to minimize damage by high numbers of rabbits and increase the presence and abundance of the brown hare, a species of conservation concern in Europe and the UK.