Conserving an Ozark Cave

Tumbling Creek Cave in Taney County is a gorgeous cave with a gurgling stream. It also has the highest recorded biodiversity of any cave west of the Mississippi River. The cave has been featured in a National Geographic special and in other TV programs, as well as in scientific articles.

The cave harbors three endangered species: gray bats, Indiana bats and Tumbling Creek cavesnails; the last is nearly extinct. Among the 115 different species found in the cave are 12 species of troglobites (cave creatures with reduced or absent eyes and pigment). Two of these troglobite species are found only in this cave.

In addition to its biological wonders, 2-mile-long Tumbling Creek Cave is an important educational and research cave. Since 1969, more than 25,000 people have taken guided tours of the cave. Each college or professional group gets an introduction to karst (areas with caves, springs, sinkholes and losing streams), views sinkholes, then enters the artificial shaft entrance, which has two airlock doors to keep the cave from drying out. The visitors bring their own lights and follow a rudimentary trail with low environmental impact.

Tom and Cathy Aley have led most of the tours. The Aleys established and operate the Ozark Underground Laboratory, which is based on a 2,550-acre tract in southern Missouri. The nonprofit Tumbling Creek Cave Foundation owns 383 acres in the cave’s recharge area and around the natural entrance, ensuring protection of the cave into the future.

The Ozark Underground Laboratory has sponsored many studies of the cave. These studies include dye tracing to map the cave’s 9 square miles of recharge area that collects water to the cave, determining water infiltration rates into the cave and collecting water quality data from the cave stream.

Other research conducted at Tumbling Creek Cave includes studies of cavesnails and stream fauna and bat censuses, as well as studies of bat guano, stalactite drippage and land-use effects on the cave.

Even though Tumbling Creek Cave has been well-protected for more than 40 years, something unexpected happened. Muck visibly built up in the cave stream, which is normally floored with cobbles. Some areas became so mucky that one could not pull up rocks that had been loose.

In addition, the Tumbling Creek cavesnail (Antrobia culveri) nearly went extinct. In 1972, a researcher had estimated that 15,000 cavesnails lived under the stream rocks. Fewer cavesnails were noticed by 1991. By 2001 only a few cavesnails could be found.

The Tumbling Creek Cavesnail Working Group brought together landowners and scientists to determine what had happened. We concluded that sediment from surface erosion was the most likely factor affecting the cavesnail population.

Twenty to 30 years ago, many forested areas in Missouri were cleared to create permanent pasture. This increased soil erosion, especially on steeper slopes in the first year after clearing or following droughts. Although the cave has no upstream entrance, the sediments worked down through sinkholes and losing streams into the cave.

A Working Group

Our group has worked on many fronts to restore or protect the cave’s unique habitat and inhabitants. In 2005, scientists placed terra cotta tiles in a cavesnail refuge area. Cavesnails were recently found on those tiles, creating hope that they may use them for feeding on microbes and laying eggs. Tumbling Creek cavesnails may rescue themselves this way.

In 2006, we built a small cavesnail laboratory in the cave, where we have done preliminary tests. If necessary, cavesnails might be propagated in the lab and then stocked in Tumbling Creek.

We sampled the water with highly sensitive equipment that detects parts per quadrillion, but found only tiny amounts of a few chemicals that were of no concern. Working with the Missouri Department of Transportation to monitor a resurfacing project on Highway 160 in the recharge area, we determined that their “chip and seal” method using an asphalt-water emulsion did not introduce any detectable petroleum products into the road ditches or the groundwater.

We also got help from the Conservation Department, which worked with the Ozark Underground Laboratory and the local community to help a school replace a sewage lagoon that was leaking most of its contents into the groundwater system feeding Tumbling Creek Cave (See The School and the Cavesnail; September 2006). A modern peat-filtration system was installed with the help of grants and substantial local contributions.

Because surface and subsurface are connected, caves cannot be protected without protecting the land that contributes water to them.

The Aleys bought nearby properties to help protect the cave and its critters. They used cost-share funds from the Conservation Department and the U.S. Fish & Wildlife Service to plant 70,000 trees to help restore the land.

Although some Ozark Underground Laboratory lands are used for raising cattle or growing hay, the overall goal is to create a landscape dominated by native species, including black oak, northern red oak, white oak, black gum, black walnut, green ash, dogwood, redbud, sycamore and short-leaf pines. Sassafras, hickories and persimmons should reestablish naturally from the surrounding areas.

Thanks to a cost-share project with the National Park Service and Fish and Wildlife Service, 20 farm dumps in sinkholes and in gullies that directly feed losing streams in the recharge area have been cleaned. Many of those dumps contained household chemicals, petroleum products, partially full paint cans, empty pesticide and oil containers with residues, used medical supplies and an unbelievable number of disposable diapers. Cavers from several Missouri groups helped with these cleanups.

Bat Protection

Bats are extremely important to this and many other cave ecosystems. Most of the energy input to a cave might be from gray bat guano.

Eight species of bats have used Tumbling Creek Cave. The endangered Indiana bat (Myotis sodalis) sometimes hibernates in the chilly entrance passage. The endangered gray bat (Myotis grisescens) has had a large maternity colony here in the spring and summer.

To protect the bats and, ultimately, the entire cave community, a team of 18 conservationists, helped by a grant from the Conservation Department, built the world’s largest chute gate on the cave’s natural entrance. A chute gate keeps trespassers out of a cave but allows bats to fly in and out. The gate was completed in 2004.

Tumbling Creek Cave’s gray bats were studied extensively because of their large numbers and the importance of the nutrient input provided by their guano. The earliest known population estimate in the cave peaked at 150,000 bats in 1969. In 1976 there were 36,000. Over the next 20 years the population generally remained below 15,000. The last outflight count before the completion of the new gate was 12,400 in 1998.

We’re not sure what caused the decline in the number of gray bats in the cave. There was a general decline in the species. An internal cave gate might have somehow hindered the bats. Trespassers might have unduly disturbed hibernation sites in the region.

What we do know from internal visual surveys, guano checks and near-infrared video counts of outflights is that the number of gray bats at Tumbling Creek Cave has increased to about 35,000 since the chute gate was installed.

The Conservation Department has increased its efforts to help Missouri cave owners and to teach people about caves and karst.

It is disturbing that the most protected private cave in the Ozarks—in a rural area with little industry or row crops—still developed ecological problems. However, the methods we developed in dealing with those problems will be useful to others.

Through studies, short courses, TV shows and (we hope) articles like this one, the lessons learned at Tumbling Creek Cave have helped many people to better manage caves and groundwater.

Cave Gating and Education

Cave gates protect caves and wildlife from human intruders, but harm can come from improper designs. Designs have changed over the years, and now we know what works and what does not. To learn more, click on the "Biospeleology" link listed below and then click on “Cave Gates We Have Known.”

The Conservation Department’s cave biologist can lend a technical hand and advice to landowners. The Department also provides educational resources on caves and karst. These include publications, guidance documents, teachers’ cave trunks, groundwater models and training workshops. For more information, contact Bill Elliott at (573) 522-4115 ext. 3194, or e-mail him at Bill.Elliott@mdc.mo.gov.

Troglobites

Twelve of Tumbling Creek Cave’s 115 species are cave-adapted troglobites. Species in bold are found only in this cave.