Land snails benefit from human alterations in rural landscapes and habitats

Abstract

AbstractMetapopulation functioning in the context of landscape and habitat structure is generally well understood. However, in human‐transformed landscapes, human disturbance may affect not only a species of interest but also biotic interactions in which that species is engaged, which has been rarely studied at multiple spatial scales. We tested (1) the associations between local (habitat and micro‐habitat) and landscape factors and the occurrence and abundance of the land snail Cepaea nemoralis and two of its predators (thrushes and mice); and (2) the hypothesis that human disturbances modify associations between C. nemoralis and its predators. We surveyed snail colonies in rural landscapes of Poland. Generalized linear mixed models were used to test the stated hypotheses. At the landscape scale, the occurrence of C. nemoralis colonies was positively related to the cover of suitable habitats, fallow/waste land, and road length in the surrounding landscape. Bird predator abundance was positively correlated with the occurrence of snail colonies, mostly at sites with a high human impact, and was negatively correlated with snail abundance at sites with low human disturbance. Snail occurrence and abundance at the micro‐habitat scale were positively correlated with variables describing the proximity of shelter and humidity. Avian predation pressure was negatively correlated with forest and settlement cover, whereas rodent predation pressure was positively associated with snail abundance and was negatively correlated with bird abundance. Human disturbance at the habitat and landscape scales benefited C. nemoralis through the creation of suitable habitats and scaling down of avian predation pressure. Conditions related to shelter and humidity were linked to the distribution and abundance of snails at the micro‐habitat scale.