20 April 2009

Clustering of the intertidal snail Batillaria minima

While in Florida 2 weeks ago, I spent quite some time collecting data on the intertidal snail Batillaria minima. In the 2 beaches where I was studying them, the distributions of these snails were often patchy: there would be areas 2-3 meters wide where I would see none of them and then there would be a cluster of 50 or 100 snails.

I kept some snails in captivity for a few days. I noticed that captive snails also had a tendency to aggregate. I carried out some simple, preliminary experiments by piling the snails up in the centers of containers and then monitoring their behavior over time.

Here are the photographic records of one such experiment. Initially, there were 40 snails around the center of a box whose bottom measured approximately 11x12 cm.


7 minutes later:


24 minutes later a large aggregate had formed against the top wall:


56 minutes later, the aggregate along the top wall was still there; in addition, there were 2 smaller clusters (or 1 diffuse cluster) along the left wall:


I think the clusters were fluid in that snails continuously moved in and out of them, but because the individual snails were not marked in these experiments, I don't have data to support that claim. I saved that experiment for a future trip to Florida.


xoggoth said...

Is that a proper specimen tray or a fast food container? They are probably going mmmmm! there's some more chicken korma over here.


Actually it was a mushroom container. But that's a good point. Nevertheless, I did repeat the experiment with a different container.

Megan said...

What tidy documentation of their group movements in that series of photos! Do you think that they're following their fellow snails' mucous trails? Maybe there's some phototropism in there as well (they seem to be moving to the shadow at the top)?

Kirk said...

I came across a time lapse controller for digital cameras, and I thought you might be interested. It's called Pclix. You could really get a good idea on movements with it, and it's not too terribly expensive.

Best regards,

Wanderin' Weeta said...

We were just noticing that same clustering behaviour in Batillaria attramentaria, here in Boundary Bay (BC, Canada).

We haven't seen that before, even though we've been walking on acres of these snails for years. Maybe we just weren't paying attention.

Nomad said...


I thought you might find this:
a. amusing
b. entertaining
c. interesting

Wid Skyline said...

thanks for this information, it helped me a lot for my oceanography biology. :)