ASSESSING SNAIL DIET TO INVESTIGATE NICHE PARTITIONING AMONG TERRESTRIAL SNAILS IN WOODLANDS FROM OHIO

Terrestrial gastropods are an integral part of their ecosystems because of their role in organic matter decomposition and the soil calcium cycle, primarily enacted through their dietary habits. The vast majority of extant snail species are short-lived (lifespan of 1-2 years) and considered herbivorous. In the past, snail foraging ecology has remained difficult to study in situ since their nocturnal activity and small body size make direct field observation difficult. However, recent geochemical analyses of some woodland snail species have documented more complex diet patterns than anticipated, suggesting that some species assimilate substantial amounts of “brown foods” (i.e. fungus, soil, lichen, wood, scat), in addition to fresh plant matter. These studies, although limited in scope, signal the need for additional research about snail dietary habits, which, in turn, will aid in the investigation of other aspects of snail ecology, such as niche partitioning and interspecific competition. This research investigates, for the first time, the diets of six common snail species native to Western Ohio woodlands (Mesodon thyroides, Anguispira alternata, Ventridens ligera, Ventridens demissus, Euchemotrema fraternum, and Polygyrida demotata) and all potential food resources using stable isotope ecology. We test the hypotheses that (1) selected snail species would incorporate notable amounts of “brown foods” in their diet, and (2) different sympatric (coexisting) species would significantly differ in their diets to minimize interspecific competition. The preliminary d¹³C and d¹⁵N results obtained support distinct dietary patterns for each species, revealing generalists and specialists, both with complex diets including a significant proportion of “brown foods” for most species. Within the generalist species, the data suggest individual dietary preferences leading to distinctive d¹³C and d¹⁵N values. This investigation suggests that coexisting woodland land snail species follow complex diets including variable proportions of “green” and “brown foods”, possibly to minimize interspecific competition.