Limpets serve an important ecological role in food chains, grazing on algae and marine plants and being an important food source for shore birds, fish, mammals, crabs, sea stars, and so forth. Many limpet shells are often covered in microscopic growths of green marine algae, which can make them even harder to see, as they can closely resemble the rock surface itself. The majority of limpets are commonly found adhering strongly to rocks or other hard substrates.The ability to clamp down seals the shell edge against the rock surface, protecting them from desiccation during low tide, despite their being in full sunlight.