Size-Specific Emergence of the Marsh Snail, Littorina irrorata: Effect of Predation by Blue Crabs in a Virginia Salt Marsh

Abstract

Marsh periwinkles of 5 to 7 mm in shell height were eaten regularly by blue crabs. Fractures marking unsuccessful crab attacks were present in about 25% of medium-sized (10-16 mm) snails and over 60% of larger snals (over 16 m). Medium-sized snails, subject to predation, leave the water more frequently tan larger snails, but only about a quarter of the snail population leaves the water during high tide. We found no evidence that the snails leave the water because they sense blue crabs in the water.