In this post back in August, I explained how I marked the shells of a land snail, a Triodopsis species, by filing small notches into the lips of the shells. The total number of shells I marked and released was 14.
Last week, almost a month later, I went back to the same spot and collected 18 snails, all I could find. 10 of the snails had notches in their lips. Surprisingly, only 4 of the snails had partially repaired the notches; in the rest of the snails, the notches filed into their lips were still, well, notches. Moreover, in those snails that attempted to repair the notches, the notch itself remained but only the inner side—where the snail's body is—was closed. Apparently, the snail can't fill the notch.
Here is a photograph of one "repaired" notch (arrow). The remnants of green paint is from April when I had marked this particular snail and a few others with a green pen (that story is here).
So it looks like filing notches into their lips is a good way to mark these snails. Even if a snail repairs its lip, the mark remains visible and it is easily detected in the field. My next trip to the study site will be in November when the snails will be winding down for the winter.