How to: Collect Moon Snails

The moon snails are living, feeding, and breeding like crazy here on the coast of Maine. I just was out doing some beach collecting today when I found this fist-sized snail half buried in a sandy stretch of clam flats. Moon snails are molluscs that are predatory as opposed to being filter feeders, grazers, or scavengers. Their scientific name is Lunatia heros. At this time of year, you will find the snails and not too far away in the mud will often lie their large 'sand-collar' egg cases. Just this one beach today had in my estimation at least 3 of these egg cases per square meter of the exposed beach! One day we decided to see how many sand collars we could find and very easily filled two 5 gallon pails of them in an hour.

It is easy to see what all these moon snails are feeding on. A quick look at the storm cast shells at the high tide mark will show that moon snails will eat any kind of shellfish that is available. Soft shell clams may be the one species that humans hate to see eaten by moon snails, but indeed there are other favored species as well. Other bivalves that get eaten are Blue Mussels

diet

Periwinkle snails, dog whelks, and even other moon snails. They are CANNIBALS - which means they eat each other too. Here are some snails I found eating other moon snails.

Apparently, they follow each other down into the sandy mud and then sometimes cannot control themselves. The poor prey snail is left with the signature of the moon snail feast - a single circular hole in its shell. The shell hole varies in size depending on the size of the moon snail that feasted there. Here are some moon snail feeding holes in blue mussels and periwinkles:

Moon snail feeding holes in mussel and periwinkle shells.

Where to find them

To find moon snails at low tide you have to look for their 'push ups' - a small mound or burrow type mark in the beach sand or clam flat mud. Years ago I always thought that this was the sign of a raccoon feeding on the clam flats. One day I decided to take a dig down into one of these and low and behold - there was the slimy, juicy foot of a very large moon snail. Once disturbed they quickly retract into their shells and pull their operculum shut behind them. What happens on the flats is that as the tide recedes, the moon snails eventually become stranded by the ebbing water. Once exposed, they could be preyed upon by seagulls or perhaps get too hot in the sun or dry out. At this point, they use their muscular foot to dig into the sand. This leaves behind a lump in the sand or a bump in the mud. Follow the bumps or lumps and you will find moon snails - it is that easy.

Moon snails make good aquarium specimens. They do feed on an occasional mollusc, but they are also very beautiful to watch as they glide along on their exposed mantle and foot. We keep many moon snails in our tanks for just this purpose.

Tidepool Tim