Factors affecting the distribution and abundance of Aegopinella and Nesovitrea (Pulmonata: Zonitidae) at Monks Wood National Nature Reserve, Huntingdonshire

The distribution and abundance of three closely related species of zonitid snails in grassland and woodland habitats at Monks Wood are described. Interspecific differences in distribution and abundance can be related to differences in climatic tolerance as shown in laboratory experiments. Evidence is presented which indicates that Aegopinella nitidula predates other snails and that Nesovitrea hammonis is a preferred prey species. It is suggested that the low population densities characteristic of N. hammonis in some areas might result, at least in part, from selective predation by A. nitidula.