In this investigation, students measure and describe movements of animals in a natural ecosystem. Students mark stream-dwelling snails with nail polish, then search for these snails 1-7 days later. Distances and directions moved by recaptured snails are recorded. Simple statistical techniques are used to answer specific research questions and identify movement patterns in the snail population. Students also use knowledge of ecological and evolutionary concepts and snail biology obtained from lectures and readings to propose explanations for observed movement patterns.