Endangered gray myotis, along with seven other bat species, had long found refuge each winter in Hubbards Cave in central Tennessee. As many as 250,000 of the beleaguered gray myotis hibernated there in 1970. But the Cumberland Mountains cave, with miles of dramatic passages and chambers, also drew many adventurous cavers who were inadvertently disturbing the hibernating bats.
By the winter of 1984, just 88,000 gray myotis remained in this critical hibernation site. Then a remarkable coalition of partners joined together to build by far the largest bat-friendly gate ever attempted to that time.
BCI and Bob Currie, a tireless bat advocate at the U.S. Fish and Wildlife Service, helped convince The Nature Conservancy's Tennessee Chapter to purchase the cave. TNC, with the support of BCI, Currie and Roy Powers of the American Cave Conservation Association, organized the project. The Richmond Area Speleological Society funded the gate and Mid-State Steel Corporation donated materials. The Tennessee National Guard built a mile-long road to the cave. Volunteers from the National Speleological Society gathered from five states to build the great gate – 35 feet (10.5 meters) tall, 35 feet (10.5 meters) wide and containing 105 tons of steel and concrete.
The gate was completed in 1985, and the impact was astonishing. By 2006, when the gate was replaced with an updated design, biologists counted some 520,300 gray myotis in Hubbards Cave.
Today, more than 90 percent of gray myotis, which range from Missouri to West Virginia and as far south as Alabama, hibernate in just nine caves during the winter. BCI has worked over the decades to identify and protect crucial caves used by the species in winter and summer and to educate landowners, officials and others about the values and conservation needs of gray myotis. By 2005, the gray myotis populations had recovered to the point that the species seemed likely to graduate off the Endangered Species List.
The Indiana myotis (Myotis sodalis), listed as endangered in 1967, presented a different problem. Once among the most abundant mammals in North America, its numbers kept falling, with just 380,000 survivors remaining in 2001 – despite gates and other protection at key caves.
Research led by BCI demonstrated that the Indiana myotis required a very narrow and stable temperature range for its hibernation sites: approximately 37-43 degrees F (3-6 degrees C).
Our study showed that many once-crowded hibernation caves had been modified by mining and/or tourism in ways that altered airflows and changed temperatures enough to make them unsuitable for Indiana myotis. Many bat caves were heavily mined in the 18th and 19th centuries for saltpeter, an essential ingredient of the gunpowder used until the late 1800s. Guano is rich in saltpeter. The miners typically dug new entrances and passageways and blocked existing ones.
Based on these findings, the key to Indiana myotis recovery had to be locating caves that were once packed with the hibernating bats, then identifying historic changes and undoing them to restore conditions required by the species.
In 2005, the Fish and Wildlife Service's Indiana Bat Recovery program made restoration of hibernation caves its top priority.
Saltpetre Cave in Kentucky's Carter Caves State Resort Park is the prime example. Extensive roost stains were discovered on the cave's ceiling in 1998, indicating that bats – apparently hundreds of thousands of them – hibernated there, probably more than a century ago. Only a few dozen Indiana myotis remained.
Winter tours of the cave were halted that year, and the bat population began to rebound. More dramatically, though, BCI Caves Coordinator Jim Kennedy worked with partners and volunteers to begin restoring the historic conditions that had originally attracted so many hibernating bats. By 2007, some 7,000 Indiana myotis were hibernating at Saltpetre Cave each winter, confirming the potential of cave restoration.
BCI launched its Appalachian Saltpeter Caves Project in 2005 to locate and survey caves that were known, by name or local history, as "saltpeter caves." A number of sites were quickly identified as promising prospects for restoration. The Indiana myotis was beginning to recover, albeit slowly.
Then White-nose Syndrome appeared in New York's Howes Cave in February 2006. The alarm was sounded the following year, and this devastating disease has been spreading across eastern North America and beyond ever since. Indiana myotis already is among the six species being hammered by WNS, and gray myotis have been confirmed with the fungus that causes it. BCI and its partners and colleagues are redoubling their efforts to protect the recoveries of both these species in the face of this new threat, even as other once-common species face the real possibility of being listed as endangered.
Entering hibernation caves is generally discouraged now, given the risks of inadvertently spreading the WNS fungus to new sites and of disturbing already infected bats.
BCI continues its varied conservation efforts around North America, but the enormous peril of WNS dominates our work.
Meanwhile, another major threat to bats caught BCI's attention in 2003: bats were being killed in alarming numbers by the spinning blades of turbines at wind-energy facilities.
BCI joined with the U.S. Fish & Wildlife Service, the American Wind Energy Association and the National Renewable Energy Laboratory that year to create the Bats and Wind Energy Cooperative, an alliance of state and federal agencies, private industry and others committed to minimizing those deaths.
BWEC scientists, led by BCI's Ed Arnett, documented wind-energy's frightful toll on bats – now estimated at several hundred thousand per year. In 2010, the researchers demonstrated that "curtailing" wind turbines (essentially shutting them down temporarily) on low-wind nights when bats are migrating can reduce fatalities by up to 93 percent, at a cost of less than 1 percent of annual energy production.
BWEC also reported promising results with acoustic deterrents. The devices, designed by Deaton Engineering, emit high-frequency sounds designed to confuse bats' echolocation to the point that they avoid the area. The task now is to refine both procedures and win industry acceptance for them.
Winning acceptance for new, bat-friendly approaches is always a challenge. BCI's North American Bat House Research Project met such a challenge in dramatic fashion through research and education in the 1990s.
Before the program began in 1993, most bat houses were small, unpainted, mounted in shady locations and had wide roost chambers. By and large, they were not particularly attractive to bats. BCI analyzed success rates for existing bat houses and quickly determined that bats prefer their artificial roosts to be larger, painted, mounted in full sun and to provide ¾-inch (19-millimeter) roosting chambers.
The findings were published that year in the first edition of the still-popular Bat House Builder's Handbook. The Bat House Research Project spent the next 10 years refining bat-house designs and expanding the initial results. Some 7,000 volunteer Research Associates erected bat houses and reported their annual results to BCI for analysis.
Occupancy rates for houses built and installed according to BCI guidelines exceeded 80 percent by the time the project was phased out in 2004. Today, bat houses are found on private and public property around the U.S. and in many other countries. They've won an enthusiastic following among farmers, especially organic growers. BCI also designed and promoted "tower roosts," essentially artificial hollow trees, and oversized community bat houses that can shelter tens of thousands of bats.
During the 1990s, BCI acquired and began its continuing stewardship of Bracken Bat Cave, summer home to the world's largest bat colony. Millions of Mexican free-tailed bats (Tadarida brasiliensis) migrate north from Mexico each spring to give birth and raise their pups in the Central Texas cave on the outskirts of San Antonio. Protecting these bats is a great responsibility.
The cave mouth and five surrounding acres (two hectares) were purchased in 1992, thanks to a grant from the Ewing Halsell Foundation, which also joined with Lennox and Beneficia Foundations to help BCI increase its Bracken holdings in 1997. The final step, which created a buffer zone totaling 697 acres (282 hectares) around the cave, was taken in 2003, with funding from the Kronkosky Charitable Foundation, Brown Foundation and W.E. Robertson Fund.
The evening emergence of millions of bats, spiraling out of the cave in a huge vortex accompanied by the soft sounds of countless flapping wings, is an awesome sight – and an unequaled educational moment. Thousands of BCI members, guests and others have witnessed this awesome spectacle. We are working to improve the educational value of the cave, return the rugged landscape to a more natural state and ensure protection and reliable water for the bats and other wildlife that live there.
Much of BCI's early conservation work in North America focused on Eastern and Midwestern states, where great bat colonies roost or hibernate together. Gating a single major cave or abandoned mine protects tens, even hundreds of thousands of bats.
BCI moved strongly into the American West in 1994, with its new Bats and Mines Project, a joint effort with the U.S. Bureau of Land Management. Western states presented very different problems: thousands of abandoned mines and diggings were scattered around the sprawling, semiarid countryside with vast expanses of public lands and private holdings.
Many of these derelict old mines provide sanctuaries for species such as Townsend's big-eared bat (Corynorhinus townsendii). But most bats form much smaller colonies than their eastern cousins. Townsend's colonies, for instance, rarely exceed 150 animals. With the exception of the Mexican freetails, conserving bats in the West required a new approach.
Old mines are often hazardous to the public, so closing them is frequently a priority for public and private landowners. Just bulldozing the entrance shut can leave trapped bat colonies to die in the dark. The challenge is to discover which mines are used by bats and how best to keep people out while allowing the bats to come and go.
The "landscape-level" strategy that evolved for the region, embodied now in the Western Subterranean Program, approaches bat conservation at a broader geographic scale by identifying and protecting mines and caves that are most critical for maintaining healthy bat populations throughout an entire region.
That, of course, means long hikes across very rugged country and spending a great deal of time dangling from ropes or squeezing through passages in old mines to look for evidence of bats. Then it requires the expertise to determine the best method for closing the hole to ensure both people and bats are protected.
BCI and an impressive array of federal, state, local and private partners have surveyed thousands of old mining features and protected hundreds that are used by bats. Led by Program Coordinator Jason Corbett, that work continues across the West.
So does the effort to ensure another key part of the bat-conservation challenge in the West: ensuring safe and available water for bats in an arid land. Since 2004, BCI's Water for Wildlife Program has used research, education and workshops to help ranchers and land managers improve water supplies, especially those originally built for livestock. By such simple actions as removing obstructions along flight paths and adding escape ramps, countless bats across the West are now enjoying a safe drink of water.
BCI's fundamental goal remains unchanged after three decades: We are still working tirelessly to conserve the world's bats and their habitats. But our strategies and tools have changed dramatically over the years. Even as we make progress against old threats, we find ourselves facing new challenges that demand urgent action.
White-nose Syndrome has refocused bat conservation in the United States and Canada. Climate change promises a host of new perils. And who knows what other threats bats will face in the years ahead? Yet Bat Conservation International, buoyed by dedicated members, partners and friends, will evolve, as it has in the past, to meet the challenges of the future.