Chasing Echoes: Are Humans Scaring Bats to Death?

October 31, 2019

On Halloween night, witches and ghouls stalk the streets in search of sweets, dodging the skeletons and vampire bats hanging from the trees.

But while fantasy figures may cause a temporary scare, the ones in real danger are the famous winged creatures of the night. Researchers at Indiana State University believe human encroachment and timber harvests may be scaring bats to death, increasing their stress hormones and making them susceptible to infections such as the deadly White-Nose Syndrome.

“When mammals get stressed, they get a surge of cortisol, which helps prepare for demands the animal may have that take energy, like flying, fighting immune infection and reproduction,” said ISU biology professor Diane Hews. "Our hypothesis is that if the Indiana bat is being adversely impacted by the forest management practices, we will see that bats have higher baseline levels of the stress hormone.”

Hews and Joy O'Keefe, ISU associate professor of biology, are conducting an eight-year project on state-owned lands in Missouri to assess the effects of the timber harvest on federally protected Indiana bats.

Two Indiana State University professors are conducting an eight-year study on the effects of timber harvest on federally protected Indiana bats.

"This project stems from a larger question that many agencies in many states have, which is if we harvest timber, are we negatively impacting these bats that rely on trees in the summer?" O'Keefe said.

While nonmigratory bats spend their winter months in caves, the rest of the year they roam the forests. In the summer, they roost in trees, under bridges, or in dilapidated buildings, where they can give birth and rear their young.

About half of the bat species found in the U.S. are listed as threatened or endangered, including the Indiana bat. White-Nose Syndrome, a highly contagious fungal disease, is a common threat. It was first detected in Indiana in 2011 and has since spread throughout the southern part of the state, leading to a 17 percent decline in various bat species, according to the Indiana Department of Natural Resources.

“We were able to see that White-Nose did have a very negative effect on our bat species,” said Brad Westrich, a bat specialist and Indiana Department of Natural Resources mammologist. “Some species it reduced their population size in Indiana by 90 percent. Others, like the Indiana bat, it did not affect as badly.”

ISU researchers said half of the bat species found in the U.S. are listed as threatened or endangered, including the Indiana bat.

That decline could have a critical impact on the ecosystem. Bats pollinate, disperse seeds and are a natural pesticide, eating millions of insects every year. According to Bat Conservation International, one little brown bat can eat 60 medium-sized moths or over 1,000 mosquito-sized insects in one night.

“If we had lost this very important pollinator, insectivore, frugivore, seed disperser, it would have untold effects on human civilization,” Westrich said.

In their study, O’Keefe and Hews will examine feces and hair of the Indiana bat for indicators of stress levels. The fecal samples provide a recent snapshot of current hormone levels over the last few hours. Hair samples record hormones levels over the time that the fur has been growing.

Since bats grow hair in the womb, the scientists can take samples from newborn bats and use them to compare stress levels from womb to adult.

“There hasn't been a before-after-control experiment like this, so we have measurements before and after, control sites that will never be harvested and then we have these experimental sites that will be harvested,” O’Keefe said.

Although it will take several years to complete the ISU study, O’Keefe said people at home don’t have to launch lengthy research projects to help save the bat population. In fact, she recommends people with trees in their backyard set up bat boxes to encourage roosting.

ISU researchers recommend people with trees in their backyard to set up bat-boxes to encourage roosting.

According to O’Keefe, bat boxes look almost identical to bird boxes, but just a bit roomier. The goal is to make a bat house that mimics the space between bark and a tree trunk.

“As the landscape has changed, we have seen that there are not many good roosts left in the landscape,” O’Keefe said. “We don’t really see the bats using the trees. For now, they are using our bat boxes.”

Westrich also urges more community involvement in bat conservation. He said he hopes people can look past the stereotype and see how essential bats are to the environment.

“Help dispel myths,” he said. “Give bats a fighting chance.”

Chasing Echoes: Are Humans Scaring Bats to Death?