INDIANAPOLIS (AP) — The Indiana bat, a state and federally endangered species, spends the winter hibernating in caves. But, over time, one of its favorite springtime hangouts has increasingly become well, less bat friendly.
That home? The area around the Indianapolis International Airport.
As Indianapolis and its surrounding area grew, forested lands near the airport have yielded to pavement and runways. But in the crevices and peeling bark of the trees that made up these forests, large colonies of the 13 species of bats known in Indiana — including the state and federally endangered Indiana bat — made their summer homes.
One particular population of the Indiana bat around the airport was displaced.
Over the years, the Indianapolis Airport Authority has worked with local conservation groups and the U.S. Department of Fish and Wildlife to protect the bats. And while they have been successful in stabilizing the population, they could use some help.
A thriving bat habitat depends on healthy and abundant trees. Researchers from Purdue and Indiana State University have found that planting and protecting native trees from invasive plants, such as honeysuckle, might be the best hope for the future of the bats.
The researchers note that in areas such as around the airport, it is crucial to create more roosting habitat, which involves planting and making sure trees grow large enough so that bats can live in them. That’s why it is do important to keep invasive plants away, especially bush honeysuckle.
“In Central Indiana, we have a huge problem with bush honeysuckle invading our forests,” said Joy O’Keefe, director for the Indiana State University Center for Bat Research, Outreach, and Conservation.
She has been working with the Center for Earth and Environmental Science at Indiana University-Purdue University Indianapolis coordinating students to help in the removal of invasive species through their service-learning program during spring and fall.
“The negative impacts of the honeysuckle will just mean it’s going to take that much longer before a hickory would get to be of sufficient size that would really be an adequate roost (for the bats),” said Victoria Schmalhofer, assistant director of CEES, who works out the logistics with students.
And even when people are not directly involved with bats, there are simple ways to help them spend their summers in safe places.
“The first thing I always encourage people to do,” O’Keefe said, “is to try to provide healthy forests and clean water for bats.”
Creating more roosting habitat, or summer housing for bats, is not only beneficial for the bat named after the state — other species reap the benefits as well. The tricolor bat and the little brown bat populations have declined 90%, said Brad Westrich, an Indiana Department of Natural Resources mammalogist.
The most recent Purdue and Indiana State study also confirmed the need to work on one of the recommendations in the 2002 Habitat Conservation Plan, crafted by a task force composed of six state and local agencies. That recommendation: increasing tree diversity.
“DNR should start really focusing on forest heterogeneity, that’s mixing up the structure and composition, so that they can provide both the solar exposed roosts and the shaded roosts, so that the bats have this this plethora of availability and choice,” said Scott Bergeson, an assistant professor at Purdue University Fort Wayne, and lead author of the publication.
This might seem like an awful lot of work just to keep bats around, but O’Keefe said keeping bats in the forests also keeps them away from people’s houses — which puts both bats and humans at risk.
The wing-fingered creatures also do a great service for communities: They pollinate crops, eat bugs that might otherwise devour food staples, and feast on mosquitoes.
Brianne Walters, assistant director at the bat research and conservation center, said Indiana bats can eat the equivalent of their weight in insects in a single night.
To put that into perspective, if bats were lost in North America, the economic impact to the agricultural industry could exceed $3.7 billion per year.
Bats are an ally for agriculture.
“They save a lot of money and they also save the need to have to apply pesticides. For an ag state it’s really easy to make a case for bats just based on their insect control alone,” said Emily Wood, executive director of the Indiana Wildlife Federation.
To fully understand the current plight of the Indiana bat — caused by myriad factors beyond development around the airport — you need to go back to the beginning.
The Wyandotte Caves in southern Indiana where the Indiana bats were first found in 1908, started gaining notoriety among hikers. When the Indiana Department of Natural Resources purchased the Wyandotte Caves in 1966, people could explore the caves for eight months out of the year. But this created a problem — they kept waking the bats up.
Bats come out of their slumber occasionally to find water or to look for cozier spots in the cave, but human voices, lights, or even slight changes in temperature and humidity caused by large groups of people can wake them up.
“They’ll wake up more frequently than they need to and so they’ll burn through those fat reserves that they have stored up too quickly, which can cause them to starve to death,” said Westrich, the DNR mammalogist.
The Indiana bat was first included in the Endangered Species Preservation Act of 1966, when biologists noticed winter populations were declining. They suspected it might be because of people waking them up while hibernating and a reduction in forest covering where they spend their summers.
“Indiana was about 75% forests. (That) went down to about 7% forests in the early 1900s, and now is more around 20% forests,” said O’Keefe, the director for ISU’s center for bat research. The bats were again included in the current Endangered Species Act of 1973, but populations started increasing in the mid-1980s when the DNR set up gates to close the caves, giving bats the chance to sleep through the winter.
Then came the fungus that causes white nose syndrome, a disease that creeps into bats’ noses and wings while they hibernate in caves.
Since first detecting white-nose syndrome in the state in 2011, the Indiana bat population has declined between 15 to 20% said Westrich.
O’Keefe, who has been studying white-nosed syndrome in bat populations in the Midwest, says the decline might be closer to 30%.
Indiana bats leave their caves after the winter and search for summer housing. The problem around Indianapolis was the growing airport.
The U.S. Fish and Wildlife Service requires those planning to build in natural landscapes to survey for the presence of the Indiana bat. More than 20 years ago, one of these surveys in the airport area showed a maternity colony of Indiana bats would have to give birth and feed their pups in alternative locations.
The bats, however, were not left to fend for themselves. The Indiana Airport Authority and the fish and wildlife service worked together to help the bats relocate.
As the airport continued to expand and the Ronald Reagan Parkway was developed, that’s when the task force was created that produced the Habitat Conservation Plan in 2002, said Georgia Parham, from the External Affairs Office at the Fish and Wildlife Service.
In an email, Parham explained that “the goal of the (Habitat Conservation Plan) was to provide for adequate habitat for this Indiana bat colony to be sustained over the long term in this rapidly developing area.” The plan set guidelines for seasonal tree cuttings, habitat protection, hardwood planting, and monitoring and researching the Indiana bat.
Researchers at Indiana State University have been studying bats near the airport since 1994, playing an important role to meet one of the conservation plan’s objectives. The legacy population of Indiana bats discovered nearly 20 years ago has been monitored longer than any other colony, Parham said. The fact that it has remained in the area despite the airport’s expansion shows the effectiveness of the mitigation efforts, O’Keefe said.
That said, it’s still a challenge. Indiana bats have a single pup every year so it takes a long time for populations to increase.
“Surviving and being viable are two different things,” said Susan Loeb, a research ecologist at the Southern Research Station of the Forest Service.
She says research done by the group at Purdue and Indiana State University helps us understand “how we can possibly manage urban forests to increase (bat) populations.”
The fragmented forest where the researchers studied the Indiana bat population is part of the nearly 2,000 acres of conservation land sold by the Indianapolis Airport Authority in 2018 to the Town of Plainfield for $1.6 million.
Of this area, 1,724 acres are reserved for conservation purposes, 210 acres make up the Sodalis Nature Park, and the remaining 142 are non-restricted land.
These lands provide roosting habitat for bats and give scientists the opportunity to study them in their spring and summer homes. Their findings are particularly important because, as Loeb mentioned, previously much of the work was done in caves and little was known of what bats do during the summer.
The fragmented forest is covered by meadow foxtail, white and red clover, and crown vetch — vestiges of an agricultural past. Oaks, hickories, and eastern cottonwoods hide the bat boxes where the flying mammals sleep during the day and then fly out of as the sun sets.
But bat boxes should just be “a temporary tool,” said Bergeson, with Purdue University Fort Wayne. Simply put, the bat boxes don’t always make good bat Airbnbs. They can also be ecological traps.
High temperature and parasite infestation in the bat boxes can be deadly. Avoiding boxes is one of the recommendations resulting from a study Bergeson and his colleagues conducted.
And it also reinforces what the Purdue and Indiana State study suggests: That the best hope for a thriving Indiana bat population — especially around the airport — is to plant and protect native trees.
Lorena Villanueva-Almanza is the 2020 AAAS Mass Media Fellow at the Indianapolis Star. She earned her PhD from the University of California Riverside in 2019 where she studied the taxonomy and ecology of Washingtonia, a group of palms found in southern California and Baja California, Mexico. She’s on Twitter as @lorevial.