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VOLUME 31, NO. 2 Summer 2013


An Unusual Home for Mother Bats
Remodeling a tourist site for bats, educators and scientists
Steven Thomas

Chapel Garden Galleries opened in 1972 as part of the Wondering Woods tourist attraction alongside Kentucky’s Mammoth Cave National Park. The art gallery included a spacious chapelhall and a sturdy, brick tower 50 feet (15.2 meters) tall. When the attraction closed in 1992, the property was donated to the national park. Most of the buildings were removed, but the chapel and tower were left standing. For years, they were largely ignored, except for occasional vandals – and one of the largest-known maternity colonies of Rafinesque’s big-eared bats.

About 100 females of this rather rare species (Corynorhinus rafinesquii) found refuge in the chapel, especially the tower, each summer as they gave birth and raised their pups in the defunct tourist site.

In 2008, increased concerns about human safety in and around the dilapidated chapel led park management to decide that the buildings needed to be demolished. As a National Park Service ecologist, I asked the park to consider sparing at least the circular tower as a summer home for bat mothers and pups. I also suggested enhancing the tower roost to provide new research and educational opportunities – an idea the park had previously discussed with Bat Conservation International and the Kentucky Department of Fish and Wildlife Resources.

Mammoth Cave management approved the plan and dedicated funds and staff time to ensure the bats kept their home. The result is a state-of-the-art bat house with an array of high-tech research and monitoring tools and the beginning of an innovative web-based citizen-science project.

Rafinesque’s big-eared bats, one of the least-studied American bat species, are thinly scattered across much of the southeastern United States. Researchers affectionately refer to them as “Rafs.” Roughly 1,500 Rafs are known to live within the boundaries of Mammoth Cave National Park. They are agile flyers that feed on moths and other insects.

Rafs hibernate in caves during the winter in this area and mostly roost during the summer months in caves, abandoned buildings and hollow trees. In summer, female Rafs gather in maternity colonies, where each gives birth to a single pup in early June. Mothers mostly nurse their babies during the day, then leave at night to feed. Adult males typically roost by themselves, but occasionally join maternity colonies or “bachelor colonies” made up of other males and females without young.

Remodeling the Chapel Garden Galleries began in January 2010, when the bats were absent and hibernating in area caves. The main building was demolished, leaving only the circular tower and its two entrance structures.

The tower itself required little attention beyond protecting the bats from human disturbance. We installed bat-friendly steel gates at the two entrances, installed a security-alarm system and added a lockable door for official access to the roost. We reinforced and replaced the roof on each of the two short entrance structures and sealed unwanted openings. The grounds were graded and seeded with native grasses and a mix of native wildflowers to promote insects.

The secure maternity roost was ready to go by March 17, 2010, when pregnant female bats began reclaiming their maternity ward.

A small, prefabricated concrete building was added within a few months to serve as a control room for an array of electronic equipment that was added over the next two years for research and education. These included Internet service, wireless monitoring, beam-break bat counting, night-vision web cameras and instruments to remotely monitor temperature and humidity.

These bats play vital roles in ecosystems, yet relatively little is known about their social behaviors. Do certain bats hang out together in maternity roosts? Do mothers help each other care for their young? How much time in the day roost is spent sleeping, grooming or interacting with their pups and with other bats in the colony? Do the babies interact with one another? How? Scientists have few answers to such questions – and they have found that even a single observer sitting quietly in a roost can disturb the bats and affect their behavior.

We installed two night-vision video cameras in the bat house to allow scientists, online observers and people at Mammoth Cave National Park’s Visitor Center to remotely view the bats without disturbing them.

Bats enter and exit the bat house through the two entrances, each guarded by a double set of gates, which allow the bats to move freely in and out, but prevent people from entering. Each inner gate has an infrared double beam-break system, installed by Bat Conservation International, that shoots pairs of infrared beams from an emitter to a detector. When a bat flies through the gate it breaks the beams and is recorded. The system provides not only the number of “beam breaks,” but information on whether the bats were entering or exiting.

These data give scientists important information on the changes and timing of the bats’ activity, but they do not provide an exact count since the same bat may break the beams multiple times in just a few minutes. Researchers are developing a model that should provide a better estimate of the relationship between the number of beam breaks and the number of bats using the bat house.

We also use Passive Integrated Transponders (PIT tags) to identify and count specific bats. These are like the microchips often implanted in pets. In 2011-12, Rafinesque’s big-eared bats were captured using a harp trap as they left the bat house. Each bat’s sex, age and health status were recorded and a PIT tag with a unique number was harmlessly implanted under the skin of its back. This process will be repeated every year in late summer to add pups and any new adults. 

A PIT-tag antenna, which resembles a culvert three feet (about a meter) across and four feet (1.2 meters) long, was installed at each entrance. When a tagged bat flies through, the antenna activates the PIT tag and sends the information to a transceiver, which records every pass. Portable PIT-tag readers have also been used to scan Rafs at other roosting sites, thus allowing scientists to track the movements of individual bats.

Of the 173 bats implanted with PIT tags since April 2011, 158 were recorded at the bat house at least once. That number is probably low because of early equipment problems that have since been resolved.

Meanwhile, the Mammoth Cave International Center for Science and Learning recently received funding from the National Science Foundation to develop a national online citizen-science initiative focused on bat behaviors. When completed, people will be able to log into the project’s website, watch streaming video from inside the bat house and record the behaviors they observe. The resulting data will be freely available to scientists, educators and others.

BCI Education Director James Eggers serves on the advisory team for this ambitious project, which is expected to be completed in early 2015.

The Wondering Woods Bat House at Mammoth Cave National Park is proving to be a success on several levels. A battered and abandoned building has been transformed to protect an important bat colony, while offering a glimpse into the secret life of bats. It is a stimulating collaboration among National Park Service scientists, researchers, educators and citizen scientists.

In the years to come, this Wondering Woods Bat House Project will produce a massive database of behavioral information that should help us answer the many lingering questions about this fascinating bat species.

STEVEN THOMAS is the Monitoring Program Leader of the National Park Service’s Cumberland Piedmont Network, headquartered at Mammoth Cave National Park.

Acknowledgements
Mammoth Cave National Park gratefully acknowledges its partners in this important project: Ball State University, Bat Conservation International, Cumberland Piedmont Network, Indiana State University, Kentucky Department of Fish and Wildlife Resources, University of Kentucky, U.S. Geological Survey and Western Kentucky University.

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All articles in this issue:
We Need Your Help
Protecting Endangered Species
Flying Foxes Rebuild Madagascar’s Tattered Forests
An Unusual Home for Mother Bats
Grassroots Help for Russia’s Forgotten Bats
The Enemy of my Enemy is my Friend
The Memo from our Executive Director

Unless otherwise noted, all images are copyright ©Merlin D. Tuttle and/or ©Bat Conservation International