04 June 2008

Still red after all these months

During an after lunch walk near the end of last January, I found and marked (with red ink) 8 live, but dormant, adults of a land snail, a Triodopsis species. These snails were at the same spot where I had collected roughly 300 empty shells of them several months earlier.

I returned at the end of February and marked, again with red ink, all the adults (25) I could find. On 17 April, I found 12 of those snails and remarked them with red ink. At the same time, I saw 9 unmarked adults, which I marked with green ink.

Yesterday, I went back. Expectedly, the place had changed quite a bit since April. There were now plants growing everywhere and one of the small boards under which some of the snails were taking refuge had been displaced. Back in April, I noticed that since the end of winter the snails had gotten more mobile and some had left their winter homes. Their increased mobility, of course, makes it more difficult to locate them.

Yesterday, the plant cover also made it difficult to search for snails, but I could still find 10 adults. None was marked green, but one was carrying its red line behind its lip.


Now I know for sure that the adults of this species survive the winter and some live at least until June. One day next week I will go back and carry out a more thorough search. I will also mark all the unmarked snails I can find with a yet different color.


Kathryn said...

fun small project. It always amazes me how little we know about life history of any of these. People always ask me how long Polygyrids live or how often they reproduce. I get tired of saying, we just don't really know for 99% of the species.


Snail said...

Do you know if the green ink was really colourfast? I have a vague memory that green paint (if not ink) was used on Cepaea as a way of investigating exposure to sun. The green faded in light, giving a relative measure.

Of course, I may have made this up, in which case it's a great idea and we should test it.


Kathryn: You are absolutely right. We know very little & in most cases, nothing about the life histories of the majority of the animal species.

Snail: I am using "Staedtler permanent Lumocolor" pens. They are said to be "waterproof on most surfaces" but nothing is mentioned on the package or on the pens about them being fadeproof. I am hoping that since these snails usually come out at nite or on cloudy days, fading from exposure to light may not be an issue. However, even waterproof inks can be scraped off, for example, by the radula of another snail. They can also simply flake off if they are not absorbed into the shell.