A shortage of food for the terrestrial snail Helicella virgata in South Australia.

Two field experiments were conducted to investigate the likelihood of snails experiencing a shortage of food. In the first experiment and in one by a previous worker, various measures of growth, reproduction, activity or survival decreased with increasing density of snails. These results appear inconsistent with the hypothesis of an absolute shortage of completely-accessible food. They could be explained by a modification of that hypothesis or by the hypothesis that snails at high density interfere with each other by means other than competition for food.The results of the second experiment suggest that the food naturally available on the study-area is of poor quality; the snails may experience a relative shortage of food, of the kind where food is abundant but much of it is low in nutrients.