Phil,
I have several papers that show pictures of shells broken by rodents (rats,
chipmunks). Such animals usually remove a large piece of shell, but do not
leave behind any scraping marks. However, it would probably be difficult to
distinguish between the holes made by different rodents. Furthermore,
rodents may also eat empty shells for calcium. How could one ever
distinguish between post- & premortem breakage?

Snails, on the other hand, create a characteristic abrasion pattern that
eventually (if it goes on for a while) creates a beveled hole with gentle
slopes.

Haplotrema concavum, if it can't reach its prey thru the aperture, almost
always opens up a hole in the body whorl in front of the aperture.
Furthermore, there will be "poke" marks surrounding the hole.

If it looks like a hole began fom inside the shell, then my best guess is
that a smaller snail consumed the shell from inside. I have removed small
live snails from inside of large empty shells on many occasions.

Aydin


On Mon, 23 Sep 2002 23:33:45 -0700, Phil Liff-Grieff
<[log in to unmask]> wrote:

>Dear Conch-L'ers,
>
>Here's a pair of questions for the specialists....
>
>
>I often find dead shells of land snails with clear patterns of breakage
>resulting from predation.  Is there any literature that describes some
>of the differences between breakage caused by rodents, vs. birds vs.
>reptiles (etc.)?  Do different species of rodent exhibit different
>breakage patterns?
>
>Secondly,  I recently collected a nice series of dead shells of a
>California Helminthoglyptid landsnail that showed a pattern of abrasion
>and breakage on the body whorl a small distance back from the outer lip.
>The hole clearly began as abrasion from inside the shell.  Is this
>caused by carniverous snails (there are Haplotremes present at the
>locality)?
>
>Thanks,
>
>Phil Liff-Grieff