Habitat Associations, Habitat Selection and Long-Term Monitoring of Land Snails: Quantifying Measurements to Better Detect Trends

Land snails have the highest recorded extinction rate, and these small animals are often overlooked, leading to data gaps. Past data for land snails is often lacking, making the analysis of trends difficult. Here, we compared past presence surveys to new quantitative estimates to infer changes over time. We surveyed 55 sites for land snails and habitat characteristics in 2024 using visual encounter surveys for medium to large snails and litter samples to assess the density of small to medium snails. We assessed habitat on two scales to assess associations and selection. We identified 27 land snail species, including a non-native species (Oxychilus cellarius). Sites with higher snail density and a richer assemblage generally had deeper litter, higher canopy cover and taller understory vegetation. Rare land snails were detected at most sites where they had previously been found, and we detected several species at new sites where they had not previously been documented, due to litter sampling. Vertigo arthuri (V. paradoxa) selected sites with a higher canopy cover. The abundance and density of land snails will enable better estimates of long-term trends and help assess how they respond to management actions. Resolving the taxonomy of Oreohelix and Succineidae is critical for direct management of these species.