A heavy rainstorm in March caused extensive damage to the $50,000 gate erected at an entrance to Boone Cave to protect two endangered species of bats.
“It was one of those good old heavy Missouri rains,” said Tim James, a Missouri Department of Conservation biologist. “The damage was caused by a combination of the way the water and the debris were coming through the slots in the gate.”
The department bought the cave in 1996 to protect six species of bats, including the gray and the Indiana, which are listed on a national register of endangered species.
This is the second gate at Boone Cave that has been damaged by rain. The first gate was constructed in 1996 at a cost of $80,000 to the Conservation Department. In 2002, the department hired a Virginia expert in cave gates, Roy Powers, to design and construct a second gate. The materials cost $50,000, which was paid with federal funds from the U.S. Army Corps of Engineers.
Conservation officials believe a gate at the cave, which is located along the Katy Trail between Rocheport and Columbia, is the best way to deter people from entering the cave and disturbing the bats. But the cave’s formation has complicated the effort.
The cave has three openings. Two of the openings take water in; one is a sinking creek, or a stream that seems to disappear into the ground. A third opening, where the gate is located, lets water out. Debris, including logs the size of railroad ties, stacks up against the inside of the gate.
“When the debris stacks up, the water weight essentially blows the gate out,” said Jim Loveless, wildlife management biologist with the department. Loveless said that a rain of more than four inches in a 24-hour period caused the damage both times.
“The gates were somewhat similar, but Mr. Power’s gate was much more substantial,” he said. “At the time it was built it was the largest cave gate in the world.”
Loveless said the department anticipates seeing the design for a new gate, by Jim Kaufmann of the Missouri Caves and Karst Conservancy, by the end of the month.
“The primary focus of the state owning that cave is for the protection of the bats,” Loveless said. “A gate has been the only thing we’ve come up with as an effective deterrent.”
Missouri has more than 5,000 known caves, but Boone Cave is one of only four in the state that is used by both the gray and the Indiana bats. Rick Clawson, a bat biologist with the department, said summer is a critical time for gray bats, which use caves to raise their young.
The gray bat will cluster together in groups as large as 170 bats per square foot, raising the cave ceiling temperature to the bat’s body temperature of 100 degrees. This makes the gray bat unique because it doesn’t need to migrate to warmer climates to raise its pups.
The gray bat weighs between one-fourth ounce and one-half ounce, according to information from the U.S. Fish and Wildlife Service Web site.
For now, the department has erected a chain link fence and posted signs warning people that human interaction can harm the bats.
“We know that when the cave was commercialized and people were in there on a regular basis, bats couldn’t live in there or raise their young,” Clawson said. “We have high hopes that the gray bats will re-establish a maternal colony in the cave.”