How do different animals capture and eat bivalve mollusks?

Various animals have evolved specialized behaviors and physical adaptations to capture and consume bivalve mollusks, which are often protected by their hard, two-valved shells.12

Predatory Techniques

Different species employ distinct strategies to overcome the defensive shells of bivalves:

• Mechanical Force: Some predators use brute force to open shells. Starfish use the relentless pull of their sucker-tipped tube feet to pry valves apart before everting their stomachs to digest the soft tissues inside. Sea otters float on their backs and use rocks as tools, pounding the mollusk against a stone held on their chest to crack the shell. Similarly, the snail Fulgur uses its columellar muscle to crack a clam shell against its own, while herring gulls drop shells onto rocks to break them.34
• Stealth and Drilling: Certain gastropods use more subtle methods. The snail Sycotypus waits for an oyster to open its valves, then quickly inserts its shell to prevent closure and extends its proboscis to feed. The snail Natica uses a filelike radula supported by the secretion of sulfuric acid to drill a hole through the clam's shell.3
• Specialized Anatomy: The oystercatcher uses its chisel-shaped bill to cut the closing muscles of a cockle. Walruses forage on the ocean floor, using their sensitive whiskers to identify clams and mussels in the sediment before consuming them.35

These diverse feeding strategies highlight the evolutionary interplay between the defensive adaptations of bivalves—such as burrowing, thick shells, and chemical secretions—and the specialized procurement methods of their predators.132