Periwinkles (Littorina spp.)

Description: Periwinkles are the group of smaller snails commonly found at Haystack Rock. They are a dark blue to black and very small, about half the size of a pinky nail. They are often found near collections of dogwinkles and acorn barnacles. Baby hermit crabs some times live in periwinkle shells when they are too small to use other snail shells.

Habitat: Different species of periwinkle can be found across the West Coast in intertidal zones. At Haystack Rock, periwinkles can be seen across tidal zones, but there are large concentrations in the upper tidal zone on algae covered rocks in the marine garden. 

Diet: These small snails scrape tiny pieces of algae off of rocks using their “radula” a ribbon like structure that is lined with teeth. They may also eat tiny zooplankton or larva if given the opportunity.

Tide Pool Tidbits:

• Shore birds, sea stars, crabs, and larger snails are known predators of periwinkles.

• Periwinkles typically do not more that 3 feet per month.

• Like many species of snail, periwinkles have a door or “operculum” that can close their shell completely for protection and to retain moisture.

References: Biodiversity of the Central Coast