Going Underground

Cavers look forward to exploring Horseshoe Bay Cave again

Sep. 10, 2013

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Jennifer Redell, cave and mine specialist with the Wisconsin Department of Natural Resources, was studying bats at the cave on Thursday night. Redell said a recent study found that insect-eating bats provide the Wisconsin agricultural industry with $658 million to $1.5 billion in insect-control services each year. / Kate Stein/Door County Advocate
The entrance to Horseshoe Bay Cave, located south of Egg Harbor, just off County G. The cave is gated and closed to the public, but a plan for public access and cave conservation is being developed. / Kate Stein/Door County Advocate

Horseshoe Bay Cave Facts
• Main passage length (known): 2,770 feet
• Combined length of all known passages: 3,103 feet
• Niagara dolomite stone walls
• Year-round average temperature: 46 degrees Fahrenheit
• Year-round average humidity: 90 percent
• Four different species of bats; over 1,000 bats total
• Largest bat hibernaculum (hibernation site) in Wisconsin
• Discovered 1896 (approximately)
• Was open to the public until 1986
Another feature of Horseshoe Bay Cave and caves in general is the phenomenon of “total darkness.” The name is somewhat misleading, though--“total darkness” is only 40 percent darker than the darkest night.
“You’d think that a cave would be absolutely dark,” Zachariasen said. Citing a NASA study that found light even in the depths of the darkest caves in America, he added, “You can’t get complete darkness; it’s just very, very dim.”

Jennifer Redell, left, and Richard Propsom set up a device that will count the number of bats going into and coming out of Horseshoe Bay Cave in Egg Harbor. Redell is a cave and mine specialist with the Wisconsin Department of Natural Resources, and Propsom works in the Door County Soil and Water Department. One purpose of their study of the bat population is to help develop a management plan for the cave. / Kate Stein/Door County Advocate
Photograph of entrance of the Horseshoe Bay Cave between the steel bars of the gate. / Tina M. Gohr/Door County Advocate
Horseshoe Bay Cave entrance on County G, south of Egg Harbor. / Tina M. Gohr/Door County Advocate


The public could be able to explore part of Horseshoe Bay Cave as soon as next summer, if progress on a plan for management of the cave continues as scheduled.

“It’s a wonderful opportunity,” said Gary Soule, current Wisconsin Speleological Society Grotto Historian and board member. He added that if the cave were open to the public, “anyone … could suddenly find themselves in a vaulted chamber, complete with stalactites and stalagmites, everything, that no one’s ever seen before.”

Soule is part of a diverse group that is working to develop a plan for the future of the cave, which is located along County G, just south of the village of Egg Harbor. The group includes two subgroups: stakeholders in the project and scientific advisers. Although all group members have different backgrounds and interests, they share an interest in creating a plan for the cave’s future.

The stakeholders group includes cavers, like Soule, town and county government officials, tourism and economic development officials and representatives from Horseshoe Bay Golf Club, which owns the majority of the cave. Wisconsin Department of Natural Resources representatives, along with geologists, biologists and cave mappers are among the scientists.

Government officials involved in developing the plan include Erik Aleson, Door County Airport and Parks director, and William Schuster, Door County Soil and Water director. The Parks Department will eventually manage the cave.

“What we’re trying to do is come up with a plan that allows access to the cave and (establishes) the process by which people can get access,” Schuster said. He added that since multiple groups would be involved in maintaining the cave when it is open to the public, it’s important all these groups participate in the planning process.

Conservation and public access

Horseshoe Bay Cave, also known Tecumseh Cave, Alpine Cave and the Door County Cave, was open to the public for approximately 90 years. In 1986, the cave was gated to prevent inexperienced cavers from entering and possibly injuring themselves or damaging the interior. The entrance remains gated, and in the past few years, only scientists have been allowed inside.

Researchers from the DNR are among the humans who have most recently entered the cave. This summer, they installed solar-powered sensors to monitor the comings and goings of the cave’s bat population. This DNR study is part of a larger investigation of white nose syndrome, a fungus that has killed entire bat populations in caves throughout the eastern United States. The fungus hasn’t yet been found in Horseshoe Bay Cave or in Wisconsin, but it is spreading to caves in the Midwest.

DNR cave and mine specialist Jennifer Redell said that because the spores that cause white nose syndrome can be spread by humans, procedures to avoid contamination of Horseshoe Bay Cave are important to planning for the cave’s future. But she emphasized that white nose syndrome and bats are only one consideration in the protection and conservation components of the management plan.

“We have an entire ecosystem to consider,” Redell said.

Bats and larger mammals, amphibians, insects, fungi and other microorganisms all coexist in Horseshoe Bay Cave. Redell said human activity would inevitably affect this sensitive ecosystem. For instance, a human with an average body temperature of 96 degrees Fahrenheit can raise the temperature of the cave from its average of 46 degrees and, as a result, impact the micro-organism population. A change in the micro-organism population could affect the population of millipedes and crustaceans that feed on the micro-organisms. A change in that population could impact other populations, such as cave spiders and, of course, bats.

Redell said that to avoid potentially negative ripple effects, members of the public who want to explore the cave will have to follow a decontamination protocol. And to keep cavers from disturbing hibernating bats, the cave will likely be open to the public only from May 1 to Oct. 15.

“You do have a very sensitive system,” Redell said of Horseshoe Bay Cave. “That’s the reason for all the precautions.”

Another consideration in developing the plan is cave ownership. The main passage of the cave extends 2,770 feet into the bluff; currently, the county owns the first 75 feet of the cave and Horseshoe Bay Golf Club owns the rest. A Horseshoe Bay Golf Club representative declined to comment for this article; Schuster described the club as “supportive” of the project and said the club wants to see the management plan completed before finalizing the access agreement. The county acquired its portion of the cave from Horseshoe Bay Golf Club in 2011.

Both Schuster and Soule said that they anticipate the final cave management plan will be completed by the end of 2013 or the start of 2014. Schuster also said the final plan will be “dynamic” to allow for flexibility as more becomes known about the cave. Along these lines, a current proposal for public access is four zones, each requiring a different amount of caving experience to access.

“We have a goal (that) we will be able to allow people to go into the front section of the cave, which is on county property, next summer,” Schuster said.

Inside the cave

Soule and fellow stakeholders group member George Zachariasen are both long-time cavers and former chairmen of the Wisconsin Speleological Society. Both also explored Horseshoe Bay Cave when it was still open to the public.

“The easy way to think about it is like going down an underground river channel,” Soule said. “It’s basically horizontal, although there’s a couple of places where there’s a 10- to 15-foot, or even a 20-foot change in level.”

Soule made a 13-hour trip into the cave in the mid-1980s and says cavers equipped with scuba gear have gone farther back than he did. Even so, he said, he doesn’t think the end of the cave has been reached.

Zachariasen hasn’t been in as far as Soule but said that even if the management plan were to allow unlimited access to the cave, he doesn’t think anyone anytime soon would attempt to “push” the cave and go farther than the area that’s already been explored.

“To get to the very back of the cave is very difficult,” Zachariasen said. “(Cavers are) wet and cold and crawling most of the way.”

Other opportunities for exploration could lie closer to the front of the cave. In total, 3,103 feet of passages have been discovered, and while he acknowledged he’s not a geologist, Zachariasen said he thinks there might be more that could be found if the front portion of the cave were excavated.

Soule agreed.

“It’s a different way to look at nature,” he said. “There are very few areas where no one has literally walked in the history of the world.”

He added, “Caves are truly the last frontier on Earth.”

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