APSU students continue important bat research at Dunbar Cave
CLARKSVILLE, Tenn. 鈥 On a muggy evening in late June, several Austin Peay State University graduate and undergraduate students hiked up to the mouth of Dunbar Cave in the hopes of finding a few bats.
The group brought with them a large Harp trap, consisting of a metal frame inset with rows of thin fishing line, and three high-frequency microphones and computerized recording units. After setting up their equipment, they sat in the cool dark of the cave opening and waited.
CLARKSVILLE, Tenn. 鈥 On a muggy evening in late June, several Austin Peay State University graduate and undergraduate students hiked up to the mouth of Dunbar Cave in the hopes of finding a few bats.
The group brought with them a large Harp trap, consisting of a metal frame inset with rows of thin fishing line, and three high-frequency microphones and computerized recording units. After setting up their equipment, they sat in the cool dark of the cave opening and waited.
鈥淪ometimes bats fly over nets, so what we鈥檝e done is set up three separate ultra sound recorders around the entrance of the cave,鈥 then-graduate student Josh Schulte said. 鈥淭he high frequency acoustic monitoring is much more likely to record any bats in the area.鈥
Several decades ago, the students probably wouldn鈥檛 have needed the traps or the high-tech microphones. Thousands of bats once roosted inside the cave and could easily be seen fluttering out over the adjacent Swan Lake. That, unfortunately, is no longer the case.
鈥淲hen we began our work here, there were very few bats, simply a single bat or two,鈥 Dr. Andrew Barrass, principal investigator for the 鈥淏at Project鈥 with the APSU Center of Excellence in Field Biology, said. 鈥淲e have been working since 2005 to try and restore bat populations in the cave. In June 2006, the Dunbar Cave State Natural Area built a new 鈥榖at friendly鈥 cave entrance gate, and they were interested in us tracking the progression of bats slowly coming back into the cave.鈥
The good news is that since the 鈥淏at Project鈥 began, the students鈥 data shows a steady increase in a few bat populations. The bad news is that the population of one particular species, known as the Little Brown bat, has declined in recent years. Its disappearance is likely the result of a major ecological disaster afflicting bat populations nationwide known as White Nose Syndrome (WNS). The fungal disease has led to the death of about five to seven million bats in North America in only the last four years.
In 2010, then-APSU graduate student Seth McCormick discovered a Little Brown bat with the WNS fungus while conducting field research in Dunbar Cave. The site was quickly closed off to the public, but state officials such as the Tennessee Wildlife Resources Agency, recognizing the important work APSU students were doing, have allowed them rare access to the cave in order to continue their research.
鈥淚 got a nice email the other day from the state鈥檚 Natural Areas program,鈥 Barrass said. 鈥淚t said they鈥檇 like for us to expand our work. Not reduce our work, but expand our work. We鈥檙e one of the few universities researching bats within a cave.鈥
The spread of WNS has closed many caves nationwide and limited important research on bat behavior.
The APSU students are now involved in research with possible major ramifications. That鈥檚 because little is known about White Nose Syndrome, but its effect on agriculture and the economy could be devastating. Bats eat tons of insects each year, providing a major benefit to the agricultural economy. A recent article in the journal 鈥淪cience,鈥 co-authored by University of Tennessee professor Gary F. McCracken, suggests that the 鈥渓oss of bats in North America could lead to agricultural losses estimated at more than $3.7 billion/year.鈥
The APSU students are working closely with McCracken and his graduate students to test bats more often for the WNS fungus during cave surveys. Dunbar Cave, however, has proven to be a bit of an anomaly. Unlike most bat roosting sites infected with WNS 鈥 where bat populations rapidly collapse with a near 100 percent mortality rate 鈥 Dunbar Cave鈥檚 population, aside from the Little Brown bat, is increasing. The cave鈥檚 Tricolor bat, or Eastern pipistrelle, has continued to increase since the APSU 鈥淏at Project鈥 began. State officials have tasked APSU students to see if that trend is continuing.
鈥淲e haven鈥檛 had the mortality that most other sites have,鈥 graduate student Veronica Mullen said. 鈥淲e鈥檝e also seen an increase in females. Their presence is more reproductively significant.鈥
The hope is with increasing numbers of females being trapped, that will mean the populations are accepting the cave and populations will grow. More females suggests more opportunities for mating, which in turn mean more bats.
鈥淭hey (state officials) are also hoping we find evidence of Gray bats using specific cave chambers,鈥 Mullen said. 鈥淭hey鈥檙e federally endangered bats. They historically used Dunbar Cave, but due to the fire and human disturbance, we haven鈥檛 seen signs of them in many years.鈥
In the 1970s, vandals set fire to Civil Defense boxes stored inside the cave. When the flames were finally put out, investigators found thousands of tiny bat skeletons littering the cave floor.
鈥淲e hope with the recent cave closure and with less human disturbances, there will come an influx of more species,鈥 she said.
During cave surveys early this year the students identified several Long Eared bats using a cave chamber. It was the first time this species had been identified in the cave.
Their 鈥淏at Project鈥 research and success has led to a growing interest in the field among a new generation of APSU students. Alisha Andrews, a junior biology major, recently joined Mullen on some night excursions to Dunbar Cave.
鈥淏eing an undergraduate, that night was really awesome that I could come out to the cave and work with graduate students,鈥 she said. 鈥淚鈥檓 told that not a whole lot of people are studying this right now, so it鈥檚 good to be a part of something that can make such a big impact.鈥
Another senior biology major, Alyssa Moe, assisted with banding captured bats.
鈥淢ost people simply don鈥檛 understand how complex bat behavior really is,鈥 she said. 鈥淭hey communicate to each other in milliseconds.鈥
In the years since McCormick discovered the bat infected with WNS, a few new cases have been detected inside Dunbar Cave. And even when bats miraculously survive, the results of WNS aren鈥檛 pleasant.
鈥淢any of the bats we capture are generally healthy and have beautiful golden brown fur coats,鈥 Barrass said. 鈥淵et, some of these recent captures show the signs of skin necrosis and infection caused by WNS fungus. Often the fungus will invade the bat鈥檚 skin cells and kill chunks of tissue, leaving holes in the bat鈥檚 wings.鈥
For now, Barrass and his students continue their research, hoping that the fungus doesn鈥檛 destroy the bats and all their years of hard work.
鈥淚t鈥檚 kind of sad,鈥 Schulte said. 鈥淲ith White Nose Syndrome killing so many bats and seeing what the bats are going through, what if this is the one of the last opportunities we have to study these highly intelligent creatures?鈥
For more information on the bat research taking place at Dunbar Cave, contact the APSU Center of Excellence for Field Biology at 221-7019 or the Bat Project website at www.apsu.edu/bat.
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Photo cutline: APSU graduate student Veronica Mullen and former APSU graduate student Josh Schulte prepare for a night of monitoring bats at Dunbar Cave.