31 May 2009

Cepaea nemoralis in Maryland

Early last week, a reader e-mailed the picture of a snail shell he had found in Maryland and asked for an identification. To my surprise, it turned out to be Cepaea nemoralis, a native of Europe introduced to a few places in the U.S. Subsequently, I got from the reader the GPS coordinates and detailed directions to his collection spot along with the warning that there was a lot of poison ivy in the area.

The location turned out to be only about a half an hour drive from where I live. So this morning I took my son along and went there. The exact spot was surrounded by an impenetrable wall of poison ivy. While I was scouting the area and trying to figure out what to do, my 14-year old son, who has been trained since the age of 4 to spot snail shells, announced his first find. It was indeed an empty Cepaea nemoralis shell from the edge of the busy highway next to us. Empty shells turned out to be quite abundant among the grass along the metal guardrail separating us from the highway. Soon we had close to 40 shells.


Here is our collection spot.


The live snails took longer to find. Eventually, I spotted them on damp soil inside the cavities around the bases of the guardrail posts.


Its brown lip distinguishes Cepaea nemoralis from the similar Cepaea hortensis. The latter, known from some islands off the coast of northeast U.S., may or may not be native to North America.


I have no idea how and when these snails were introduced to this spot. We will probably write a short paper to publish this new record for Maryland. Until then, I will keep the exact location confidential.

Part 2


xoggoth said...

The Banded Snail. Quite common round here (South East England) and one included on our animals identification CD.

According to the CD (my sister is the nature expert, I just do the software) they are rather variable in colour, although they are usually a brighter yellow in our garden than than in your picture.

fred schueler said...

Well you never know where they're going to show up. In Ottawa I'd thought they were confined to a few locations, with dense populations, but when we went up to the daughter's birthday celebration recently, there was a downpour, and a single C. nemoralis crawling across the porch of their apartment building. This complicates the search for the introduced colonies across Ottawa, because it means we've got to search everywhere.

George said...

Why hide the location of this population of a potential pest?


I don't think Cepaea nemoralis is a pest, potential or real. There are known populations of it at several places in the U.S. & I've never heard of any complaints against it.

Anonymous said...

Yes. Not all introduced species become "invasive" or "pest" species.

Susan J. Hewitt

Michael Hölling said...

There's an interesting project here in Europe to learn about evolution during this Darwin year 2009: people are asked to count Cepaea snails to record changes in color morph frequency during the last decades. See at http://www.evolutionmegalab.org/

Greetings from Germany

George said...

According to a snail lab at Michigan State University, C. nemoralis has been reported as a harvest contaminant in vineyards in New York and Ontario, but its status as a pest is open to question, which is why I included "potential" in my question.

A student in this lab recently completed a dissertation on some ecological aspects of this species. He gives a reference that reported the species in 17 states, including Maryland, as of 1964:
Reed, C.F. 1964. Cepaea nemoralis (LINN.) in eastern North America. Sterkiana vol 16, pp 11-18.

He also cites a book on pest slugs and snails in Europe (Godan, 1983) that identifies this species as a significant agricultural and garden pest there.

Also, apparently nobody has looked at ecological impacts of this snail on native snails or other species, despite its wide occurrence.

I'm not saying its definitely a pest, it may well not be one. Whether it might be a pest or not, I'm still wondering why one would hide the location of a population.



(I hope this is not a duplicate post, my first attempt doesn't seem to have worked)


George, thanks for the info. The location of our record will eventually be in the manuscript. In the meantime, I don't see an urgent need to reveal it. Snails like C. nemoralis, despite their conspicuous coloration, are cryptic, at least where we found them, & not very large. These characteristics would make it difficult to eradicate them even if anyone attempted to do so. We don't yet know how widely they are distributed anyway.

Mary said...

This is one of my favorite snails because of the shell variability. They are awesome.

As a person fascinated by snails I am very pleased to see that you are not going to reveal where they are located right off the bat.

I haven't heard of any in Florida, unfornately, I would love to see some in person and take some pictures of them.

Thanks again!

Kevin Bonham said...

I've been involved in a similar case involving an outbreak of an exotic species (see current Cepaea thread) except that that one definitely is a pest.

There are a couple of legitimate reasons for concealing the locality of such infestations:

1. It's always possible someone else might poach your discovery and beat you into print before you publish it; stranger things have happened.

In my case that one doesn't concern me but what does concern me is:

2. It is always possible that if you publish information about the location of a colony of a new pest before it can be eradicated, some nutter might seek to spread the pest species deliberately as a form of eco-vandalism or economic sabotage. Not a very big risk but still one I would rather avoid unless there is a benefit in releasing the information.


Orion Curiel here from Montreal, Quebec, Canada...And you guessed it folks...This same Gastropod is abundant in Montreal in wodde areas next to train tracks. Surely there are many other spots but now at either end of town on 2 different train lines I have found this Grove Snail by the bagfull. I have a lot of pictures similar the the Maryland ones in this article.