A survey has been carried out on the status of bats in Britain. Of the 14 species, the status of two, the greater horseshoe and mouse-eared bats, is precarious. The survival of these and other cavernicolous species depends on the availability of underground roosts, many of which are being destroyed, or rendered uninhabitable by extensive disturbance during hibernation. Where such disturbance is prevented by a grille at the cave entrance, the number of bats using the roost increases. There is a trade in cave-dwelling bats for museums, schools and research. Large numbers of pipistrelles and other species are killed each year in buildings. In many cases, the slaughter is fruitless because the roost is subsequently reoccupied. Ignorance and fear of bats is widespread among members of the public. With the decrease in deciduous trees, fewer roosts are available for tree-dwelling species.