The sand dollar is a type of small sea urchin that has a surprising number of predators. Most people think of sand dollars as flat, white shell circles found on the beach. In actuality, those are just their skeletons. "Living sand dollars are covered with velvety, purple spines used to grab food particles," according to an article in "The Seattle Times." When threatened, baby sand dollars drifting through the sea clone themselves, seemingly to protect their species.
Sea gulls are one of the most prominent predators of sand dollars. Sea gulls carry the sand dollars in their mouths and dash their bodies on rocks and other sharp objects. Typically, the sea gulls eat the adult sand dollars, but they can also eat the larvae of sand dollars.
Starfish will also eat sand dollars in both adult and larvae forms. Starfish eat the sand dollar by suddenly striking out at the sand dollar and ingesting it with sharp spine-like teeth on the bottom of their bodies. Starfish usually only attack sand dollars smaller than themselves.
Many species of crab eat sand dollars. Crab species such as the sand crab, hermit crab, king crab and stone crab all frequently attack and eat adult sand dollars. The crabs pinch the sand dollars and slowly rip apart their bodies before finally ingesting them.
Otters will also occasionally eat sand dollars. Otters usually do not come into contact with sand dollars because most sand dollars frequent saltwater locations while most otters live in fresh water. However, when a sand dollar washes up on a beach where fresh water meets saltwater, such as at a river mouth, an otter will eat the sand dollar if given the chance.
Several species of fish will also eat sand dollars. Their flexible bodies make excellent meals for larger fish such as the trigger fish, wrass and flounder. Sharks and other larger fish may also eat sand dollars, but usually do not because sand dollars stay close to the sea bed.
Some species of snails will also eat sand dollar larvae. These snails slowly chew on the bodies of baby sand dollars or on dead sand dollars. Usually a snail will not attack a fully grown sand dollar because the sand dollars are larger than most snails.
Octopi also prey on sand dollars. An octopus will grab a sand dollar from the ocean floor and hold it in its tentacles. The octopus will then eat the sand dollar in one large gulp.