Lockout for bats.
A DIFFICULT PROBLEM needs "fairly drastic action," and Daniel Boone National Forest's John MacGregor is faced with one: Protecting the privacy of resident bats. For two species of these "flying mice," this action preserves more than just beauty sleep: It can mean the difference between life and death.
"The problem here is that we're looking at the extinction of at least one bat species--the Virginia big-ear--within the next 10 or 15 years if something isn't done to save the only two major remaining populations," says MacGregor, endangered-species specialist for the national forest in eastern Kentucky. "Next to go could be the Indiana bat."
The populations are dwindling for several reasons, the main one being "human disturbance" to hibernating and nesting colonies, according to Larry Martoglio, a 26-year Forest Service veteran and wildlife staff officer at Daniel Boone. The bats are also adversely affected by habitat destruction, direct killing, vandalism, and the use of pesticides on their food--insects.
Both the Virginia big-ear bat, a five-inch-long, chocolate-colored creature with mule-like ears, and the flat-faced, three-inch-long Indiana bat are currently listed as federally endangered. One colony of Virginia big-ear bats winters in a cave on private land in West Virginia, the other in Stillhouse Cave on the 670,000-acre Daniel Boone.
The "drastic action" MacGregor refers to is the fairly new practice of "gating" bat caves--closing off entrances to everyone except resident bats. The slatted gates, made of quarter-inch angle iron, allow for normal air flow through the cave and don't change ambient temperatures. A gated cave retains all its normal conditions; the only difference is that vandals can no longer get in to destroy the bats or their habitat. Well-intentioned folks such as spelunkers and biologists can't get close enough to the furry creatures to cause problems either, MacGregor says.
"Even if a bat colony is disturbed unintentionally, the results can still be disastrous," Martoglio says. "When bats are awakened from hibernation, they use up their store of winter fat needed to sustain them until their insect food source is available in the spring." One arousal costs a bat as much energy as it would need for two or three weeks of hibernation. If there are enough arousals, the bat can starve.
Disturbing maternity colonies when newborns are still too young to fly can be equally damaging. When a parent bat is bothered, it can panic and drop or abandon its young, resulting in the little one's death, Martoglio says.
Although a number of bat species are endangered in other parts of the country, gating is not widely practiced outside Kentucky, though it may be eventually. (Throughout the United States only about 70 bat caves have been gated, MacGregor says.) Currently nine Kentucky caves have received 11 gates. Four were placed on bat caves within the Daniel Boone with two more possible in the near future, MacGregor says. The oldest "successful gating" was done only four years ago, but bat censuses already indicate dramatic population gains.
In 1983, the U.S. Fish and Wildlife Service prepared Recovery Plans for Virginia big-ear bats, Indiana bats, and others, and formed a Recovery Team made up of bat experts who recommended gating or fencing important bat caves and placing warning/interpretive signs in others, Martoglio says. The stout angle-iron gates, which cover cave entrances, were designed by Roy Powers of the American Cave Conservation Association and Robert Currie of the U.S. Fish and Wildlife Service. They vary considerably in size, according to the dimensions of the cave opening, and they're assembled at the location from 30-foot lengths of angle iron, each piece weighing about 400 pounds.
The Kentucky National Guard airlifts the pieces of angle iron by helicopter to clearings near the cave openings, which are often remote and inaccessible by truck. The weighty steel must then be carried to the caves by Forest Service personnel and volunteers. They set up cutting torches and welding units and build the gates on-site for a perfect fit, then anchor them in place with poured concrete. The gates, which cost an average of about $12,000, range in height from about seven to 18 feet and in width from 25 to 60 feet. They're fitted with an angle-iron door that's kept locked except to authorized Forest Service personnel who go in to take bat censuses.
Complying with recommended Recovery Plans, the Forest Service gated Daniel Boone's Cave Branch Cave in 1989, Well Cave in 1992, and Stillhouse Cave late last summer. Population increases have been dramatic: The Indiana bat numbers in Cave Branch Cave have grown from 300 to 800 in four years, and in Well Cave from 300 to 600 in one year.
No Virginia big-ear bats winter in either cave, "but about 5,000 Virginia big-ears, or about 40 percent of the species' total population, hibernate in Stillhouse Cave," MacGregor says. "The only other known colony is threatened by a West Virginia quarry where work, if not halted, will eventually break through into the bats' hibernating area--thus Stillhouse is the place where it's most conducive to protecting the bats."
About 1,000 Indiana bats hibernate in Stillhouse. Kentucky has about five percent of the species' total population; 15 percent--about 4,000--hibernate on the Daniel Boone.
Plans are underway to have Daniel Boone's Cave Hollow Cave gated by the end of 1993. At Minton Hollow Cave, where the Indiana bat population has dropped sharply and only about 300 individuals now winter, gating is also desirable. But gating there may be impossible because the cave is such a popular recreation area, MacGregor says. Because the cave is large and the bats hibernate "in an out-of-the-way spot," he believes fencing the area may be sufficient.
Though gating and fencing are offering new hope for endangered bats, the species are threatened by other problems. A three-year study on the bats' range and food habits has recently been completed by Michael Lacke, professor of wildlife at the University of Kentucky. It shows some other measures that must be taken.
Virginia big-ear bats, the study determined, eat only moths, which in turn feed on sourwood or grape; thus a coordinated effort is needed to preserve these plants, MacGregor says. Indiana bats consume a wider variety of insects, which are susceptible to pesticides. The bats range up to six miles in search of food.
To protect foraging areas, the U.S. Forest Service has recently instituted a "cliffline policy," which forbids "interruption," or logging, of the forest canopy within 200 feet below clifflines and 100 feet above them. The Forest Service is building ponds on Daniel Boone--one per 160 acres--to benefit aquatic-insect-eating Indiana bats and other wildlife, Martoglio says.
"More has to be done to protect the bats while they're outside their caves, but we do know that the gating is working," MacGregor adds. "At least we can protect the bats while they're here."
Pamela Selbert covers environmental and resource topics from her home in St. Louis, Missouri.
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|Title Annotation:||Wildlife; cave-gating techniques to preserve endangered bat species|
|Date:||Mar 1, 1994|
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