A Comparison of Native and Non-Native Snails and Slugs Across Countries in the Metro-Atlanta Region

Terrestrial gastropods are essential contributors to ecosystems, and in urban settings, non-native species can be particularly disruptive. While land snail and slug distribution is understudied, an improved understanding of diversity can be achieved through the use of citizen-science apps such as iNaturalist. This project details the keen observations and data collected on land snails and slugs within the 11 counties surrounding the city of Atlanta. The work is based on the iNaturalist project SLIME (Snails and Slugs Living in Metropolitan Environments) out of the Natural History Museum of Los Angeles. Here, we similarly use iNaturalist to study and record observations on land snails and slugs in the Atlanta SLIME project. Our goal is to better document the distribution of native and non-native terrestrial gastropod species in metro-Atlanta.

Our preliminary data are based on >1000 observations in iNaturalist from the 11 counties in metro-Atlanta (Cherokee, Clayton, Cobb, DeKalb, Douglas, Fayette, Forsyth, Fulton, Gwinnett, Henry, Rockdale). Common native species include members of the genera Deroceras, Discus, Megapallifera, Pallifera, Philomycus, Ventridens, and Zonitoides. The most abundant observations are of mantle slugs; however, it is unclear if that is due to observer bias, in that they may be more likely to be recorded by iNaturalist users compared to other taxa that are less visually appealing. Interestingly, reports of the carnivorous snail Euglandina, while native to the southeastern U.S., are new to the region, and could have implications for local populations in and around Atlanta.

Non-native species in iNaturalist include members of Ambigolimax, Arion, Bradybaena, and Oxychilus. Several non-native taxa have been confirmed by field collection, and some are more commonly found in DeKalb or Fulton. It is not yet known if that is due to greater human impacts, sampling bias with efforts focused nearer to campus, and/or if their presence is more widely distributed. There are also additional reports of other non-native species that have yet to be fully confirmed due to uncertain identifications and/or limited observations. Further research is needed to examine variation across counties, and in particular uncovering non-native species that may pose an immediate and long-term risk to local ecosystems.