What happens to intertidal snails during the winter?

When I’m asked to explain what I do,* my standard 10-second response goes something like this:

“I’m a PhD student at Northeastern University’s Marine Science Center in Nahant, MA. I study marine ecology.  My research focuses on one type of snail, the dogwhelk, which lives on rocky shores along the coast of Massachusetts and Maine. I study how factors like temperature can affect how much the snails eat and grow at different locations in the northern and southern Gulf of Maine, which involves doing a lot of fieldwork.”

Nucella on hand
Dogwhelks (Nucella lapillus)

After I finish that brief explanation, one of the most common follow-up questions I get is: “Where do the snails go in the winter?” I’m not really sure why that one question is so overwhelmingly popular, but in honor of the impending wintry weather, here is the answer:

Dogwhelks (Nucella lapillus) don’t really go anywhere in the winter. They don’t migrate. They don’t die. They basically just stay on the rocks and hunker down for the winter.

Which is actually pretty amazing – New England rocky shores are an extremely challenging habitat, and winter is no exception. Water temperature usually stays around 40° F but the air temperature during low tide can get much, much lower. And dogwhelks are ectothermic (“cold-blooded”), so their body temperature is the same as their environment! Winter storms are also common, which can generate massive waves. Dogwhelks aggregate in protected areas of the rock, such as crevices and overhangs, to avoid being dislodged (Feare 1971, Crothers 1985).

Waves in Nahant during a storm last winter — now imagine you are a 1 inch snail hanging onto a rock. (video by Missirius)

Even though the snails are still around during the winter, I only do experiments with them in the summer. Because it’s so cold in the winter, the snails don’t move around very much, or eat, or grow. Non-moving, non-eating, non-growing snails aren’t very interesting to study, so I squeeze all my experiments in when it’s warm. New England may technically have four seasons, but my year only has two: field season (May-Oct) and desk season (Nov-April).

*This typically happens in one of two situations: at parties where polite conversation is expected and at field sites when I’m schlepping around power tools and other gear.


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