Shelta Cave

SHELTA CAVE

All photos by CDaniels unless noted otherwise

Shelta Cave is located directly underneath the National Speleological Society's national headquarters on Cave Avenue in Huntsville. It is approximately 2500 feet long, with a huge 7-acre underground lake and two sink hole entrances. It is the only known habitat of the cave crayfish, Orconectes sheltae. It was purchased by NSS in 1967. According to Bill Torode, curator and librarian for the Huntsville Grotto, the local NSS chapter, the cave was named after the daughter of Major Henry M. Fuller who owned the farm in the late 1800's. Fuller bought the farm and tried to develop the cave into a commercial enterprise. It was opened for walking tours, boat rides and dancing. Floorboards were built over the limestone cave floor for the dance hall.

With permission from the NSS librarian Bill Torode, this photo shows the entrance to the cave in 1889.

Short trail to the cave entrance from the Speleological Society headquarters in 2003.

TEACHER ACTIVITIES

Teachers will have a tour of the cave, guided by Bill Torode, to observe the general geology, dissolutional sculpturing, cave sedimentation, and mineral deposits and speleothems of Shelta.
Its cave ecosystem will be discussed, including its basic biospeleology.
Bill Torode will describe how he had mapped the cave with the assistance of several NSS members in 1973.
Teachers will be measuring the dimensions of just one small section of the cave to experience what it takes to map a cave.
Teachers will test some water samples for temperature, pH, dissolved oxygen, and salinity.
Teachers will be discussing the possible explanations for the following phenomena:

            There were bats in the cave before it was gated. Why did they all disappear?
            Why is it that several cave animals historically living in Shelta Cave are no longer there?
            What is radon and how much is in the cave?
            Why are all the invertebrates in the cave declining?

The last activity will be a short visit to the National Speleological Society's headquarters where teachers may browse through the societies extensive library on caves and spelunking. Many of the books are available for purchase.

Bill Torode, NSS librarian

Shelta cave has one of the most outstanding underground ecosystems in the United States. It is a habitat for several species of cave life, most of which are endangered and protected. There are known to be at least three beetle, two crayfish, a shrimp, and three other arthropod species inhabiting Shelta Cave. There are other species found in the cave such as isopods, amphipods, crickets, spiders, worms, millipedes, and centipedes.

Courtesy of the Texas Memorial Museum, The University of Texas at Austin
and the Missouri Department of Conservation.
@Chip Clark After years of study by a biologist named John Cooper, Orconectes sheltae was described. Found only in Shelta Cave, this crayfish species was found to have a long life span with extremely slow growth and reproductive rates. The males mature after the age of 40 years. Individuals may live to 100 years. Generally, crayfish is an opportunistic omnivore, feeding on whatever organic matter washes into the cave system. It feeds on organic
detritus, aquatic insects, and small crustaceans such as isopods, copepods, and amphipods that are brought in by the streams that feed the cave.

However, Shelta Cave has shown a decline in its biodiversity in the past thirty years. It has been cited as a case study for effects of nutrient loss in a cave ecosystem. Land development and vandalism impacted the cave in the 1960s. At the time, cave harbored a large colony of the endangered gray bat, Myotis grisescens. The NSS purchased the cave in 1967 to save it even moving their headquarters to a building above the cave. They gated Shelta Cave in 1968 using a strong, cross-barred gate taken from an old jail. Little did they know that the gate was not conducive for bats. By 1970, the bats have abandoned the cave. It was also hypothesized that the increased urbanization of the area might have also caused the colony's disappearance from Shelta Cave.

In 1981 a modern, horizontal-bar door replaced the old gate but no bats returned to the cave. This species usually shy away from any type of structure on cave entrances. In 2002, a new fence surrounding the two entrances to the cave was built by members of the Huntsville Grotto. It is at least 20 feet from the entrances. NSS hopes that the more accessible entrances to the cave will encourage bats to return but be discouraging enough for any youths who might vandalize the cave.

Studies by Cooper in 1969 and 1975 showed the rich biodiversity in Shelta Cave, with three species of extremely long-lived crayfish with low reproductive rates, a shrimp, cavefish, and numerous other troglobites. These organisms dependent on food from bat guano. When the bats disappeared, their population declined. Two other biologists, Hobbs and Bagley, did a census study of the cave from1985 to 1989. They confirmed the disappearance of the bats and the accompanying decline of crayfish and cavefish. The decrease in the crayfish was from the range of about 100 individuals to 0-10. For the cavefish they only counted up to 3-15. By 1996, Hobs recorded that the Alabama cave shrimp dropped from 1-25 to none. Upon analysis of the water in the cave, Hobbs and Bagley found small amounts of the insecticide heptachlor epoxide in 1989. It was probably leaching into the groundwater from houses nearby. Whether the bat disappearance along with its guano or the pesticide caused the cave community to decline, no one can be sure.

Another recent finding regarding Shelta Cave may be a factor. One of the geological circumstances of a karst environment is the presence of radon gas. The cracks and fissures in the limestone, shale and other porous rock allow for underground gasses to work their way to the surface. Uranium present in minute amounts in the bedrock decays emitting radon gas. It can accumulate in the cave, permeate the ground, then seep out into the air. Radon is a carcinogen, damages DNA, and is a contributary factor of lung cancer.

Madison County ranks among the highest at risk for radon contamination. In Madison, there is karst beneath Hazel Green, Meridianville and Monte Sano. Some houses in Monte Sano have tested 300 pCi/L! The EPA recommends anything over 4 picocuries of radon per liter of air of radon be mitigated. In Shelta Cave, the tests have shown 400 to 500pCi/L of radon. The NSS office had a radon reading of 83 pCi/L, more than 20 times the acceptable level. NSS and the Alabama Cooperative Extension System agreed to use the headquarters building as a demonstration site for radon mitigation.

photo by Gary Wyman, Courtesy of NSS

In 1973 Bill Torode and several NSS Huntsville Grotto members mapped Shelta Cave. The fruits of their labor is shown below. Bill will present and demonstrate some of the methodology of cave mapping. He will also show some of the more intriguing features of the cave. According to Bill, fossils of very large brachiopods of Mississippian age were in the cave. He also mentioned that the level of the water in the cave varies tremendously depending upon the amount of rain and streamflow of the subterrenean sources of the cave.

Courtesy of NSS, photo by Ed Nicholas

Courtesy of Bill Torode and NSS

Special thanks to the helpful staff of the National Speleological Society, Bill Torode and Stephanie Fearles.

References:

Elliott, W.R. 2000. "Conservation of the North American Cave and Karst Biota." Chap. 34, pp. 665-689 in Wilkens, H., D.C. Culver, and W.F. Humphreys (eds.), Subterranean Ecosystems. Ecosystems of the World, 30. Elsevier, Amsterdam. xiv + 791 pp., http://www.utexas.edu/depts/tnhc/.www/biospeleology/namcons.htm

Stephens, Challen, "Classroom at your feet". Huntsville Times, March 5, 1998 p.A1, A6.

Torode, Bill. "Shelta Cave." NSS News No. 3, March 1973

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