Crabs
Larger crabs, such as blue crabs, green crabs and mud crabs, eat clams. Crabs will not eat the shells of clams. To reach the edible clam body inside the shell, crabs crush clams between their claws, which breaks the shell open. Soft-shell clams make up the bulk of the green crab's diet. Hard clams are also a popular food item for crabs, though they are not as commonly consumed as soft-shell clams.
Horseshoe Crabs
Horseshoe crabs also eat clams. They will eat both soft-shell clams and very small hard clams and can burrow into the sand to find their prey. While horseshoe crabs may look similar to the crabs listed above, they are actually two very different animals. Horseshoe crabs are closely related to spiders. The broad, smooth shell of the horseshoe crab makes an excellent place for barnacles and other small sea creatures to live and grow.
Snails
Snails, such as moon snails, whelks and oyster drills, eat clams. To catch the clams, snails dig rapidly into the sand. Snails attack clams in two ways. Whelks force the clam to open while moon snails and oyster drills both drill one hole into the shell of the clam. Once the clam's shell has been breached, snails can reach and consume the body of the clam inside.
Other Predators
In addition to the predators listed above, many other animals eat clams. Starfish pry clams apart with their arms, then insert their stomachs in the shell to dissolve and eat its body. Worms sneak into clams through a gap in the valves, then eat them from the inside out. Skates and rays crush clam shells with their teeth to get at the body, and seagulls are known to drop clams onto rocks to break them open.