Population Demography of a Land Snail Species of Conservation Concern in the Black Hills

Abstract

Understanding population biology of a species is critical for its successful management. We obtained information on movement, growth, and activity levels from four populations of Cooper' Rocky Mountain snail (Oreohelix cooperi) in the Black Hills, South Dakota, during May through September 2005 from a simple mark-recapture set-up. Grid population density estimates for each of the four sites ranged from 145 to 795 individuals. We observed movements up to 7.2 m. Moisture was more important than temperature in determining the presence of Cooper's Rocky Mountain snails within a site. Growth was not continuous across the season, but concentrated in intervals. Different populations maintained distinct differences in shell size. Although we could not statistically explain diameter differences, we hypothesize that population density, range of moisture conditions experienced, or another habitat characteristic, i.e., litter thickness, may influence overall size of individuals. Our results demonstrated that mark-recapture methods can be used for monitoring populations of western land snails as well as answer important demographic, ecological, and life history questions.