Changes have been slow in coming, but today's National Park Service now manages bats and their habitats with increasing recognition of the importance of these resources . . .
Changes have been slow in coming, but today's National Park Service now manages bats and their habitats with increasing recognition of the importance of these resources . . .
BY MARI HOUGHTON AND RONAL C. KERBO
FROM A DISTANCE it looked like a huge column of smoke; for hundreds, perhaps thousands, of years the impressive sight drew humans who wondered what it was. What they found was the entrance to a cave and millions of bats swirling to gain height before dispersing over the surrounding desert. Bats are credited with the discovery of what is undoubtedly one of the world's most spectacular cave systems, and the bat emergence each summer evening still draws people to Carlsbad Caverns National Park in southeastern New Mexico.
At the time of the cave's official discovery, perhaps as early as the late 1800s, President Ulysses S. Grant had already established the nation's first national park, Yellowstone, in 1872. Over 40 other parks and national monuments were added by the time the National Park Service (NPS) was officially created in 1916. Today, America's national park system is one of our richest natural and cultural heritages, encompassing some of this country's most beautiful and diverse lands, from deserts to wetlands, prairies to mountains, forests to seacoasts, to archeological and historical sites.
There are 368 areas in the system, covering more than 80 million acres in every state except Delaware, and including American Samoa, Guam, Puerto Rico, and the U.S. Virgin Islands. The park service exists to conserve these lands and the wildlife that lives there-preserving them for future generations, while providing for the human enjoyment of these special places. The diverse habitats of our parklands abound with wildlife, and significant bat populations are found in many of them making their homes in caves, historic abandoned mines, rock crevices, trees, and even in old park buildings.
Federal guidelines form the basis for management of these natural and historical resources, but each park also creates a plan to address the management of its own unique features and wildlife. Most park visitors view these lands as places where all resources are treasured and protected, but this has, unfortunately, not always been the case especially for bats and their habitats.
The importance of caves to surrounding ecosystems to say nothing of the importance of bats-was little understood by early park naturalists. As a result, some major bat populations have been lost on national parklands. Visitors themselves can share some of the blame. In the past, many park managers perceived caves more as a potential hazard to visitors than as valuable resources. The exception was if a cave had enough striking features to warrant being developed for tourism. When fences around non-commercial caves and mine openings didn't work as a safety measure to keep visitors out, parks often resorted to blocking the entrance by other means-a death sentence for bats.
Even in commercialized caves, concern was for the pleasure and safety of visitors, not for the bats that may have been displaced from a home or for the other biotic cave communities that were disturbed. The number of facilities built directly over the caves at both Carlsbad and Mammoth Cave National Park are further evidence of the initial lack of understanding of fragile cave ecosystems. Fuel storage tanks, gas lines for commercial and residential of its own unique features and wildlife. Most park visitors view these lands as places where all resources are treasured and protected, but this has, unfortunately, not always been the case especially for bats and their habitats.
The importance of caves to surrounding ecosystems to say nothing of the importance of bats was little understood by early park naturalists. As a result, some major bat populations have been lost on national parklands. Visitors themselves can share some of the blame. In the past, many park managers perceived caves more as a potential hazard to visitors than as valuable resources. The exception was if a cave had enough striking features to warrant being developed for tourism. When fences around non-commercial caves and mine openings didn't work as a safety measure to keep visitors out, parks often resorted to blocking the entrance by other means a death sentence for bats.
Even in commercialized caves, concern was for the pleasure and safety of visitors, not for the bats that may have been displaced from a home or for the other biotic cave communities that were disturbed. The number of facilities built directly over the caves at both Carlsbad and Mammoth Cave National Park are further evidence of the initial lack of understanding of fragile cave ecosystems. Fuel storage tanks, gas lines for commercial and residential buildings, along with drainage from sewer lines, remain as potential hazards.
Carlsbad Caverns had a history of commercial use before being designated as a national monument in 1923. Miners removed tons of nitrate-rich bat guano in the early 1900s, shipping it to southern California for the new citrus industry. Blasting two shafts in the ceiling of the main bat roost, they streamlined operations and seriously altered the cave microclimate for the Mexican free-tail bat (Tadarida brasiliensis) nursery colony that originally led to discovery of the cave. Although mining was halted in the main bat cave when Carlsbad was added to the park system, the practice continued in other caves in the park until as recently as 1957.
After Carlsbad became a national monument, tourists continued to walk beneath the bat roost for a few years, but when the park constructed the first tourist trails into the cave in the mid-1920s, they skirted the bat section, leaving it in relative peace. Some 50 years later, however, it was clear that the bat population had declined radically. Concerned, the park service began a study to find out why. No one knows how large the colony was before guano mining began, but a 1936 survey estimated that 8.7 million bats were still present at that time. When the park began its study in 1973, it was a drought year, and less than 200,000 bats were in residence.
The pesticide DDT was eventually implicated, but there were likely other causes as well, prime reasons being development of the cave for tourism and the mining shafts bored into the roof of the main roost. Needing more warmth to raise their pups, bats gradually abandoned their traditional roost sites in the cave. As a result of the study, the park resealed the shafts, restoring the cave's original microclimate. It has been almost 15 years since then; populations at the cave fluctuate from year to year and last September were at about one million, a substantial gain but also illustrative of the slowness of recovery.
Carlsbad can be given much credit for helping to change misperceptions about bats. Over time, the emergence of the bats became part of the total experience of visiting the cave, and rangers began giving talks. Today, park naturalists lecture about the bats in an amphitheater at the cave entrance, just before the evening flight. A popular and integral part of the park's interpretive services, they are attended by as many as a thousand people each summer night.
MAMMOTH CAVE National Park in central Kentucky can't match Carlsbad for its bat emergence, but it is an equally famous cave and the ninth most-visited park in the system. Tourists have been coming for about 150 years, long before it became a national park. Mammoth forms a huge cave system with hundreds of miles of interconnected passageways and numerous openings. There are some 90 known caves within the park, from small to some of the world's largest.
It is the medium-sized caves that federally endangered Indiana bats (Myotis sodalis) seek for their winter roosts. Even with the huge number of caves in this part of central Kentucky, only seven fit the narrow hibernation needs of Indiana bats in the area. Five of these are within the national park. Mammoth itself shows evidence of having had large historic and even prehistoric bat populations, but no one knows just when bats began to leave the cave. Saltpeter mining during the War of 1812 likely contributed, followed by the beginning of tourism not too many years later.
Despite the importance of these caves to bats, Mammoth has long had a poor record of protecting its bats. With the expansion of their resource management staff in recent years, current managers are committed to correcting past abuses, but changes have been slow in coming. Long Cave, one of the five Indiana bat hibernating sites within the park, is a classic example. The cave had been commercialized sometime in the early part of this century, but was closed to tourism probably by the 1930s. While the cave entrance had been restricted in some way ever since, the barriers didn't entirely prevent bats from entering. In 1947, Long Cave still contained more than 50,000 hibernating Indiana bats.
Sometime after that, however, the population plummeted as successive barriers over the entrance became more and more restrictive, culminating in a concrete wall and solid door with only small slots cut into it for bats. The door was added largely to prevent vandalism to the cave, but with airflow severely restricted, temperatures rose.
And because the restriction also forced the bats to land before entering, they were especially vulnerable to waiting predators. Indiana bats are one of America's most endangered bat species. Surveys conducted in 1993 by the U.S. Fish and Wildlife Service Indiana Gray Bat Recovery Team documented that the total Indiana bat population continues to lose ground and may have declined by as much as 41 percent in the last 10 years.
As the bat population continued to fall in Long Cave, biologists and others pleaded to have the openings restored. Many promises were made, but essentially little happened. BCI recently added its official voice to those of new park resource managers, and asked Ron Kerbo, a longtime friend of bats and the cave management specialist for the park service's Southwest Region, to help. These actions, along with the tireless efforts of BCI member Bob Currie, a biologist with the U.S. Fish and Wildlife Service, finally paid off: the park removed the door and erected a bat friendly gate inside the entrance last summer. Designed not to restrict airflow and to allow bats free access, such gates are also constructed to keep people out. This winter, a survey team found 892 bats, a gain of over 100 from the previous official count two years ago, but still far from what the cave historically sheltered.
Long Cave wasn't the only cave in the park where Indiana bats were ousted from their traditional home. The bats of Colossal Cave suffered a similar fate when a solid door blocked the entrance to this cave as well. Although park staff cut several bat-sized holes in the door sometime in the 1960s, it was not enough, and the population fell. The cave received a bat gate about ten years ago, and the colony has been relatively stable since then. Last summer, the park installed an improved bat gate on Colossal, but biologists still observed only 333 bats this winter, a nearly 95 percent decline from the last-known historic population of the early 1950s. Biologists do not know why the population hasn't rebounded.
Dixon Cave may have provided an alternative of last resort for Indiana bats in the park, since other caves in the Mammoth area, both in and out of the park, were unavailable to them for many years.* The bats were never subjected to the stress of commercial park tours, and the cave's entrance was never blocked. Although Dixon's historic populations had always been relatively low (perhaps indicating marginal habitat), it is now one of the nine Priority I hibernation caves for the species. The area around it is fenced off, but because it is near a trail and picnic grounds, the fence has not totally discouraged unauthorized entry. In the last decade, the cave's population has declined about 36 percent.
Dixon is scheduled to receive a bat gate this summer, and with the new gates protecting Long and Colossal Caves, the bats of Mammoth Cave National Park now have a chance to rediscover their historic winter roosts. When the next official surveys are conducted two winters from now, biologists hope to see an increase in bats in these critical caves.
CAVES AREN'T ALL that park managers must consider when protecting bat habitat. Early mineral explorers staked claim to some of this country's most beautiful lands, now within the boundaries of our national parks. A legacy of our pioneer history, many abandoned mines today pollute surface and underground water with heavy metals, sediments, and much more, seriously degrading local ecosystems for both wildlife and people. These historical sites also present another danger to visitors who cannot resist exploring old mine tunnels: each year people are injured or fall to their deaths. For both of these reasons, mines on public lands throughout the country are being reclaimed or their entrances permanently closed.
But while abandoned mines on national parklands can be a scourge and a hazard, yesterday's exploitation has also created some of today's most critical habitat for bats driven from traditional cave roosts through commercialization or other human disturbance. More than half of this country's 43 bat species now roost in old mines, usually because they have few other choices. Not all mines are suitable for bats, but in those surveyed, almost half are used by bats, some by very large colonies. Many more remain to be investigated.
Estimates have been that over 4,000 abandoned mineral sites exist in the park system, ranging from mere scrapes to vast underground workings. Many mines have numerous entrances, forming huge complexes of openings. Some 11,000 underground openings exist on national parklands; California's Death Valley alone accounts for over 4,500 of them, illustrating the magnitude of the problem that the park service has in addressing safety closures and in being sensitive to resident bats. With the recent addition to the park system of new lands under the California Desert Protection Act, these estimates may skyrocket.
The park service reclaims or closes between 10 and 100 mine openings each year. Assessing sites for bats has not always taken place before closure, but this situation has been gradually changing. Today's park service is officially committed to protecting abandoned mines important to bat populations and to outfitting them with appropriate gates. A number of parks have already conducted mine surveys and erected bat-sensitive gates, and others plan to do so.
Over the past three years, Death Valley National Park has worked with BCI member Dr. Patricia Brown to identify Townsend's big-eared bat (Plecotus townsendii) roost sites so they could be protected. The species is highly vulnerable to disturbance and is a candidate for endangered or threatened listing. The Eureka Mine, a hibernation site, was the first to receive a bat gate. The mine had held less than 20 bats, but in the two years after installation of the gate, the colony increased to more than 60. Today it is the largest hibernating population of these bats known in the California desert. Tourists once had access to the historic mine year-round; now the gate is locked in winter when bats are present and open only in the legendary heat of the Death Valley summer. Two other Death Valley mines have also received bat gates, both used by big-eared bats as summer nursery roosts. Future surveys will be directed at identifying and protecting other bat roosts within the park.
Big Bend National Park in the Chihuahuan Desert of southwestern Texas also contains historic mines, which have long posed a hazard to curious visitors. Concerned for visitor safety, the park began in the 1970s to place barriers over most of the openings they could locate. The presence of bats was not considered. A later survey revealed that the barriers had been vandalized anyway, and at least at one barrier had enabled predators to kill bats as they entered. More recently, the park asked experts to survey for bats in the mines and to make recommendations for more secure closure that also would enable bats free access.
Dr. Scott Altenbach, a biologist with the University of New Mexico, found that almost half of 18 mine openings in Big Bend were used by at least three, perhaps four, species. Bat gates were recommended at five of the openings, with others requiring further study. Work is expected to be done early this spring before the bats return for summer. The park service is also working with BCI to develop educational signs to post at the new gates so visitors will have a better appreciation of the bats within and why the gates were installed. The diversity of bats at Big Bend is greater than in any other park, with some 18 species of 11 genera.
Farther to the east, in the Ozark Mountains of north-central Arkansas, the Buffalo National River provides rich habitat for bats. The park is honeycombed with caves, and the area surrounding it contains numerous caves as well, including one of the most important gray bat (M. grisescens) hibernating sites known. This remote cave on U.S. Forest Service land harbors some 15 percent of the entire species population of these endangered bats each winter. The nearby Buffalo River provides critical summer habitat for gray bats, as well as for two other endangered species, Ozark big-eared bats (P. t. ingens) and Indiana bats. Indiana bats use forested riparian habitat in summer, not only for feeding, but also for raising their young.
In addition to its caves, the park contains many abandoned mines. As recently as the late 1950s, mines in the Rush Historic District produced zinc. Today, some 30,000 people visit the area as tourists. Because many mines were within sight of designated trails, the park service began a project 10 years ago to prevent entry into several of the more prominent openings. Despite six-foot-high, chain-link fences and bright yellow "danger" signs, determined visitors continued to enter. The park recently began surveying the mine openings to assess whether bats were present and to determine their future potential as bat habitat. They evaluated some 50 openings, finding bats in 30 of the adits or tunnels.
The park plans to erect bat gates at each of the openings where they discovered bats. The ambitious long-range gating project began two years ago, and matching funds provided by BCI are enabling additional work this summer. The new bat gates will minimize visual intrusion on the historic district, attracting far less attention to the openings. The park also sees the project as an opportunity to expand its interpretive programs for bats. They hope with protection and education that bat populations will increase throughout the entire area, not just within the park.
Many other parks also contain historic mines now used by bats. About seven years ago, in the Great Smoky Mountains National Park in North Carolina, the largest known population of Rafinesque's big-eared bats (P. rafinesquii) was discovered in a series of remote abandoned mines. This species is under consideration for endangered or threatened listing. The park was concerned about protecting them, but most of the openings were impractical to gate. In a cooperative project between the park and the U.S. Fish and Wildlife Service, the entrances received protective fences and one received a gate. Bat numbers are now growing.
At the Chesapeake and Ohio Canal National Historical Park in Maryland, park staff enlisted volunteers last summer to help build bat gates for three historic mines, which had been heavily vandalized. The mines are used in winter by three bat species. Although bat numbers were small, park managers considered the bats important to protect. The park also hopes to conduct bat surveys of their numerous caves.
Nearby, the Delaware Watergap National Recreation Area, along the Pennsylvania-New Jersey border, plans to erect bat gates over the entrances to two old copper mines, which are hibernating sites for four bat species. As has happened elsewhere, bat populations dropped drastically when solid doors with only small holes for bats were placed over the entrances. Rick Dutko, a BCI member and zoologist with the New Jersey Natural Heritage Program, coordinated a field trip to the mines last fall with BCI and representatives from federal and state agencies. Dan Taylor, director of BCI's North American Bats and Mines Project, convinced park staff to remove the doors and erect bat gates instead. The park is committed to correcting the situation and is now in the planning stages.
As many more parks deal with the issue of safety closures of abandoned mines, they too will face the necessity of considering mines as bat habitat. But park personnel will be better equipped today than in the past. BCI's recently published Bats and Mines, a special technical publication on the issue, is already being used by park managers. And with the recent Memorandum of Understanding (MOU) between the National Park Service and BCI, they will have the opportunity to receive training in how to solve the problems that often pit the needs for visitor safety against the needs of bats.
THE CONSERVATION OF BATS on our national parklands has come a long way since the park service was founded. And awareness of the importance of bats, not only to park ecosystems, but also to surrounding areas, is much greater today. Some of the progress can be attributed to behind-the-scenes action taken by BCI, and much of it can also be attributed to dedicated BCI members and other friends of bats. Without their help and persistence, a great deal of this improvement might never have taken place.
But while many parks have in recent years become more sensitive to protecting their bats, funding to erect special bat gates or to conduct surveys can be difficult to find, and bats often remain at the bottom of the priority list. Inaction, though, is costly for bats, especially for declining species like the Indiana bat. While protective gates are a proven help in the recovery of bat populations, the process is very slow. Some bat colonies may be lost before they are protected.
Our national park system is continuing to add new lands with significant bat habitat. Samoa National Park was established in 1988 in American Samoa to protect flying foxes and their unique rain forest habitat. The bats, Samoan flying foxes (Pteropus samoensis), are being evaluated for endangered or threatened listing. The park was created only through several years of intensive work by BCI and its members and colleagues [BATS, Winter 1988].
The California Desert Protection Act, signed by President Clinton last fall, designated some 7.5 million acres in southeastern California as wilderness and created the 1.4-million-acre Mojave National Preserve. Four million new acres are now under the jurisdiction of the NPS. With the addition, the number of abandoned mines on national parklands has also increased greatly from past estimates. Would-be miners once filed many thousands of claims on these lands, and it will take time to assess how many of these actually resulted in a mine or what their potential is as bat habitat.
AS THE BATS RETURN to Carlsbad Caverns in the early morning light, they fold their wings and dive from the sky into the cave at astounding speeds, much as they have been doing for centuries. For the past 45 years, however, once a year late in summer, awed human visitors await their return in a special park tradition: the bat-flight breakfast. After the event, the people feast on a hearty breakfast, while the bats retire for a rest after a hard night's feeding. They will have flown over 80 miles round-trip to nearby agricultural lands where roughly half of their evening meal consisted of crop pests.
Unlike most other park mammals, bats know no boundaries. They may go home in the morning to a particular park, but they can also provide tremendous ecological benefits far beyond park borders. Parks are increasingly living up to their mission of conserving habitat for all their wildlife, including bats. But park visitors too must change their attitudes and learn to respect the homes of these animals. With as much beauty as we have in our national parks, there is still plenty for visitors to explore other than the fragile habitat where bats live.
Mari Houghton is Editor of BATS. Ronal C. Kerbo is the cave management specialist for the park service's Southwest Region. He has been working with caves and bats for over 30 years.
* Nearby Coach Cave, under private ownership, received bat gates in the summer of 1993 with BCI's help [BATS, Fall 1993] and was once home to over 100,000 Indiana bats. The cave was, for the most part, blocked to bats for some 30 years.
The sight of great numbers of bats emerging from the entrance of Carlsbad Cavern in New Mexico is what originally drew people to the site (above). While the interior of Carlsbad makes it one of the world's most beautiful caves, the bats are still a major attraction.
In the park service's early years, caves were considered as hazards rather than as assets unless the cave had enough spectacular features to be developed for tourists (left). Other caves were sealed for visitor safety. The sad outcome was that important bat habitat was lost and bat populations declined precipitously on national parklands.
As many as a thousand people a night await the emergence of Carlsbad's free-tailed bat colony. Park naturalists lecture about the colony and the park's other 14 bat species before the event.
Mammoth Cave National Park in Kentucky contains some 90 known caves, including five critical hibernating sites for endangered Indiana bats. Safety barriers placed over cave entrances were installed to keep tourists out, but they also discouraged the bats. As a result, Indiana bat populations in the park declined severely. The park is now installing bat gates instead.
The bats at Long Cave suffered one of the highest declines in Mammoth Cave National Park. This past summer, at long last, the old barrier was removed and a bat-friendly gate was installed, which allows bats free access but still keeps people out. Official surveys this winter showed an increase of over 100 bats.
California's Death Valley has more mine openings than any other park. When Biologist Patricia Brown (left) discovered big-eared Bats (right) hibernating in the Eureka Mine, the park decided to erect a bat gate to keep people from disturbing the colony. As a result of protection, the colony has grown to become the largest hibernating population of the species known in the California desert.
Left. This barrier over a mine opening in Big Bend National Park, Texas, typifies the kind of restrictions the park service used in the past to keep people out of old mines, but bats suffer severely as a result, and such barriers are easily vandalized. Big Bend is now replacing them with good bat gates.
Right: The Delaware Watergap National Recreational Area plans to remove the solid barrier from this old copper mine where four bat species hibernate. Bats enter through small holes in the door, but their numbers have dropped drastically. The problem for bats is not only in entering, but also that solid barriers alter the cave microclimate. Dan Taylor (left) talks with chief park resource planner Beth Johnson.
Samoa National Park is one of our newest parks and was designated to protect the habitat of Samoan flying foxes. The park was established through the efforts of BCI and friends.