Snail Collecting Protocol for the Schoolyard
Below, a snail feeds on the microscopic life living on a fern.
Photo by Charles Wilder. |
- How/what to collect.
- Because we want to limit our impact, it is best not to collect live snails. As we are currently unable to ID them to species, we can get no useful data from a live snail without killing it. Since a snail can pull deeply into its shell, it isn’t always easy to discern live vs. dead. One clue is that live snails often have a shiny film around the lip, and/or a dark mass 1/4 to 1/2 turn up the shell. When in doubt, leave it in the field!
- Container: Any small container that will prevent crushing. Insert paper with pertinent information into the container with
the shell(s). Film canisters work well.
- How to do the Inventory.
- Set up a 10 meter square plot (or appropriate size for your group). Mark the edges of the plot with flagging.
- Break students into groups by collecting technique (i.e. leaf litter sifting, visual search around the base of trees, visual search under logs and leaves, visual search on plants and standing trees).
- Collect in the plot for a set time (i.e.15 minutes).
- Sort the snails collected into groups of like shells. Use the snail characteristics sheet as a guide (i.e. is there a lip, are there teeth, compare the height, overall size & belly button).
- Assign each different species a number (e.g. species 1, species 2, species 3…) by marking on the shell with a permanent marker. Only mark shells that are empty.
- Save one shell of each species to use a reference. Using a small fishing tackle kit is a great way to save and display the shells. Distribute all other shells back in the plot (that calcium is important).
- Next time you are in the field, take the reference key. Use the data sheet to track total numbers of each species you see. You are creating baseline data of what snail species are in your schoolyard.
- Add any new species to the reference key.
Background:
Land snails are one of the exceptionally diverse groups in the Smokies. Researchers have already documented 130 species of snail and slug as living in Great Smoky Mountains National Park. Expectations are there could be almost as many species still unknown from the park, including some species unknown to science. Unlike slugs, a land snail leaves a shell behind when it dies and most species can be identified using the shell alone. Land snails range in size from over 40 mm in diameter to only one millimeter in diameter, therefore it is important to look closely for the tiniest species.
Most snails, unlike slugs, require a source of calcium in their diet in order to build their shells. This is significant in the context of the park for several reasons.
- There are only three areas in the park with significant limestone-based surface geology (Cades Cove, White Oak Sinks, and Finley Cane) and these are the areas with the greatest land snail diversity. These are also the only known locations in the park for some species that can only live on limestone substrates.
- Dogwoods are significant in the forest for bringing calcium to the soils (via their roots and leaves), making the forest floor less acidic and more accessible for calcium-loving species. Dogwoods are declining in the park because of an introduced fungus pathogen called Dogwood Anthracnose. The species that is replacing the dogwood in the forest understory is Eastern Hemlock, which has the reverse effect on the soils.
- Acid deposition in high elevations is leaching calcium out of the soils. There are several dozen species of snail found only in high elevations in the southern Appalachians. The loss of calcium from the mountaintop ecosystem may be having an adverse effect on these species and could possibly lead to their extinction. Additionally, research in Europe has provided convincing evidence that lack of calcium in some environments reduces reproduction in some groups of birds. Dutch researchers associated the bird declines on years of acid precipitation, which appear to have reduced land snail numbers. Snail shells are a prime source of calcium for wild birds that need to boost calcium for egg laying. The Dutch scientists were able to manipulate reproductive success in their study by increasing calcium with supplemental feedings. Dr. Ted Simons’ study in the Smokies will investigate this same issue starting in 2004. The Smokies get some of the highest depositions of sulfate and nitrate in North America.
Because of these significant issues effecting land snails in the park, it is important that we learn as much as possible about the present distribution of snail species in the park so we can recognize when species start to become rare, or rarer than they are now as these issues have been in effect for several decades already. Knowing their present range can also help managers identify populations that may be especially at risk from future acid deposition or loss of dogwoods, allowing protection activities to begin sooner. This project will produce the following three results:
- Locate and identify new park record species of land snails
- Increase our knowledge of the current range of land snail species
- Provide students with both an educational experience and a legitimate sense of contribution to the protection of the park's incredible diversity
