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?