24 July 2009

A massacre in the forest


A couple of weeks ago while exploring the park near my house I found this tree with a deep hole in its trunk. Tree holes are usually good places to search for interesting creatures. Sure enough, there were 3 snail shells inside and just outside this hole. Each had its apex removed.


The largest one, an adult, is a Neohelix albolabris. The others are probably juveniles of the same species or juveniles of Mesodon thyroidus (the 2 species are difficult to distinguish before they mature).

Not too far from the 1st tree, at the base of another tree with a partially rotten trunk on one side, I found 7 more shells with similar breakage patterns. The 2 largest ones are again Neohelix albolabris. I suspect these snails had been preyed on by a rodent, perhaps a chipmunk.


On the same tree, about 1.2 m above these shells was a live juvenile snail temporarily dormant on the trunk. Because I could not identify it for certain, I brought it home.


I noticed earlier this afternoon that it had built its adult lip and it is a Mesodon thyroidus, a species that often climbs trees. That would be an effective way to avoid ground based predators*. On the other hand, I don't remember if I've ever seen Neohelix albolabris on trees. And that may explain why most of the predated shells I found appear to belong to the latter species, although the juveniles require a definite identification.

Potential revision alert (26 july 2009): My identification of the snail from the tree as Mesodon thyroidus may have been premature. Apparently the snail has't completed its growth yet and may in fact be a Neohelix albolabris. I may revise this post in a few days.

*Do chipmunks climb trees?


Kirk said...

Yes chipmunks can climb trees. Deer and white footed mice will also eat pretty much whatever they can get their mitts on, those shells remind me of mice gnawings.

School for Us said...

So, I'm curious as to what eats snails and leaves remains like that?