Marsh periwinkles live inside of shells that they make.This marsh periwinkle snail has crawled out of the salt marsh and onto a boardwalk or wooden deck. By Graham D. Schuster
Marsh Periwinkle snails live in coastal salt marshes along the east coast of North America. They live as far north as New York, as far south as Florida, and as far west along the Gulf Coast of the United States as Texas.
Coastal salt marshes are special land habitats along the edge of the ocean that are affected by ocean tides. When the tide is high, the marsh is flooded with salt water. When the tide is low, the water retreats to the ocean and the land is revealed. The retreating water often leaves behind mud and food that periwinkle snails like to eat.
Marsh Periwinkle snails adjust their lives to the patterns of the tide. Marsh periwinkles crawl across the mud of the salt marsh and look for food when the water is low and the land is exposed. When the water is high, marsh periwinkles crawl up the stems of grasses that grow in the salt marsh. On the grasses, the marsh periwinkles are safe from the water where they could drown. They are also safe from crabs and conch snails that eat the marsh periwinkle snails.
The tide is low, the water has retreated, and sand and mud are exposed in this salt marsh. Marsh periwinkles look for food on the ground during this time. By Greg Thompson, courtesy of the US Fish and Wildlife Service
The tide is high, the water has covered the land, and marsh periwinkle snails have crawled up the stems of grasses that grow in the marsh. By Mary Hollinger, NESDIS/NODC biologist, NOAA
For references, please see the links listed above and the book listed below.
Kaplan, Eugene H. A Field Guide to Southeastern and Caribbean Seashores. Houghton Mifflin Company: Boston, 1988. P. 235.