The Roman snail (Gastropoda: Helicidae) is not a generalist herbivore, but shows food preferences for Urtica dioica and plant litter

Abstract

ABSTRACT The food preferences and palatability of different plant species for snail and slug species in arable fields has been a major area of research in the past. The assumed diet of Helix pomatia (Linnaeus, 1758), however, provides an example of the limited knowledge of snail diets in nonagricultural habitats. This species has been described as a generalist herbivore, although it showed preferences for individual plant species in another study. Helix pomatia is considered a pest species, while also being listed as endangered in several Red Lists. In this study, the feeding activity of eight subpopulations of H. pomatia were recorded in a nature reserve in Cottbus, Germany, from April to October 2021 to understand food preferences and feeding behaviour. Along with the plant species on which feeding was observed, the height of feeding in the vegetation, shell width and height, number of whorls, and exposure to direct sunlight at observation sites were recorded. Results indicate that H. pomatia prefers Urtica dioica, and plant litter, which accounted for 35% and 44% of all observed feeding interactions respectively, as food resources, while generally only feeding on 27 of 143 available plant species. The importance of U. dioica as a food resource for 19 other terrestrial snail species is confirmed by 18 previous studies. In H. pomatia, analysis of the width and height of shells indicated that smaller, juvenile snails consumed plant material significantly higher up in vegetation as compared to adult snails, which fed closer to the ground. Awareness of the preference in H. pomatia for U. dioica as a food resource may be beneficial for land managers regarding the impact of this snail as an agriculture pest to crops. Urtica dioica is a very important food plant for terrestrial snails, and could play an important role in future species conservation strategies.