Eating Habits of Moon Snails

Moon snails are known for having bodies that extend far beyond the size of their shells. They are predators that have been devastating clamming communities by nearly depleting the clam population. The only known predators of moon snails are humans and sunflower stars. Moon snails can be found on sandy beaches and there are several different varieties. Understanding their eating habits can make it easier to figure out how to control the moon snail population.

  1. Prey

    • Moon snails eat bivalves, or animals with two hinged shells, such as clams, scallops, oysters and mussels. They also eat limpets and cockles, which are smaller snails. These snails will also eat dead fish. On rare occasions, moon snails will even drill into other moon snails for food.

    Process

    • A moon snail digs for prey in the sand with its large foot. Moon snails first attempt to kill their prey with suffocation. They wrap their large foot around the prey, making it impossible for the prey to breathe. Moon snails can also drill holes in prey. They soften the shells of clams by secreting acid, and then they drill a hole through the clam using a mouth part called a radula. Once the hole is drilled, they scrape out and eat the clam meat, leaving the rest of the shell intact.

    Drilling Habits

    • Moon snails are very consistent when it comes to drilling holes in their prey. Nearly all clam shells are drilled in the umbo region of the shell, which is the bump at the anterior part of a clam shell. Moon snails may place the hole here because it is directly over where most of the meat of the clam lies. This also may be the location where the moon snail can get the best grip on the clam to begin drilling.

    Impact

    • The moon snail is causing great difficulty for clam diggers, especially those in Northern Maine. Moon snails are drilling into and eating an alarming number of clams. According to the Maine Department of Marine Resources, the clam harvest fell by 85 percent from 2006 to 2009, from 800,000 pounds to 100,000 pounds. The population of moon snails is difficult to control because their egg cases can hold more than 1 million eggs. The clam diggers have been trying to remove moon snail egg cases to prevent new moon snails from hatching.