Collaborative program monitors bats at Effigy Mounds

By Audrey Posten, North Iowa Times

A four-year monitoring effort between Effigy Mounds National Monument and the University of Dubuque has helped Effigy Mounds learn more about the park’s bats, some of which are being decimated by the spread of white-nose syndrome. 

When the collaborative program began in 2014, Effigy Mounds had never extensively studied the kinds of bat species in the park, said Tyler Self, an Effigy Mounds bio tech who spoke at a recent public event on bat monitoring. 

“We wanted to have a good understanding of what species we have here. If we happen to have any endangered or threatened species, we need to be able to consider that in any management decisions the park makes,” he said. “And if we continue to study species we have in the park, it’ll allow us to know when there are changes to those populations.” 

In 2014, a disease called white-nose syndrome, which was first detected in New York in 2006, was also rapidly making its way through bat colonies in the eastern U.S., leaving massive die-offs in its wake. 

“Some of those colonies don’t exist anymore. A half a million bats, simply gone,” stated Gerald Zuercher, professor of vertebrate ecology at the University of Dubuque, who, with his students, has helped with the monitoring project. 

“When we were thinking about doing this project,” said Self, “it was apparent white-nose syndrome was spreading westward. We knew it would be important to get data on bats now, before they’re affected. And now that they are being affected, we can monitor that.” 

Caused by a fungus that originated in Eurasia, white-nose syndrome causes dehydration and emaciation in small hibernating bats. 

“Bats are trying to decrease their metabolism in the winter so they can save energy and sleep. What this is doing is forcing them to burn a lot of energy,” Zuercher explained. “When a bat burns too much energy in the winter, it has to start looking for food. If you’re a bat that eats insects, and it’s January, you’re out of luck.” 

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Bats are one of the most diverse groups of mammals, with roughly 1,200 species worldwide. Through the monitoring efforts, Self said seven species have been identified at Effigy Mounds. Three of those—the eastern red bat, hoary bat and silver-haired bat—merely migrate through in the spring and summer. They haven’t been affected by white-nose syndrome, but Zuercher said they can carry the fungus that causes it. 

The other four Effigy Mounds species—the big brown bat, little brown bat, northern long-eared bat and tricolored bat—live in the area year-round, roosting in trees, rock crevices and human-made structures during the summer, then hibernating during the winter months. The northern long-eared bat has been a federally-threatened species since 2015. 

“This is probably the species we’re most interested in when we’re studying bats at Effigy Mounds, because they’re threatened,” Self said. 

Unfortunately, said Zuercher, the little brown, tricolored and northern long-eared bats have been among the species most susceptible to white-nose. Because they’re smaller bats, he said they likely don’t have the fat reserves to sustain them through the winter. 

Self said this is troubling because bats are a significant part of the local ecosystem. They eat not only mosquitoes, but agricultural pests like the corn ear worm moth and tent caterpillar moth. 

“Particularly in the upper Midwest, the costs in agriculture that are saved because of what bats are doing are in the tens of millions per year, per county,” Zuercher added. “Think about that over an entire state. We’re now talking hundreds of millions of dollars that farmers aren’t having to spend on chemicals.” 

“That’s why white-nose is such a concern for us,” he said, “because a lot of those bats that are doing that job and saving all that money are disappearing rapidly.” 

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Monitoring bats is no easy task. They’re active at night, when most people are inactive. During the day, they roost in places that are difficult to find. Bats are also small and fly between trees. They use echolocation for navigation and communication, but the sounds are largely inaudible to humans. 

“It’s pretty hard to just watch bats’ behavior and learn a whole lot about them,” Self said. “And we don’t have all that many tools to pick from to study bats.” 

Although Effigy Mounds staff and their University of Dubuque partners have used radio telemetry, genetic analysis and habitat analysis to learn more about the park’s bats, mist netting and acoustic monitoring are their biggest tools. 

Field work began with mist netting in 2014. 

“Mist netting is the tool you need to use if you want to get a bat in your hand and say, ‘We definitely have this bat in the park,’” Self noted. 

To utilize this method, fine mesh netting is strung from two tall poles. Researchers hope bats won’t notice the net while they’re flying, instead crashing into it and entangling themselves. Once a bat is caught, staff immediately extract it. They then examine the bat, determining species, gender and age. The bat’s weight, body length, forearm length and ears are also measured. 

“We’ll look at their wings, to see if they have any scars from damage on their wings, because that’s actually a primary symptom of white-nose syndrome,” Self stated. 

Once a bat is caught, the researchers can also choose to put a small radio transmitter on it, for tracking purposes. The transmitter, which is glued to the bat’s back, is so light it doesn’t harm the bat or affect its behavior. It falls off after several weeks. 

“For northern long-eared bats, we wanted to learn where the females go during the day,” Self said. “That’s going to be the maternity colony and, for us, the most important habitat to protect in the park.” 

Each transmitter emits pulses every few seconds. With the help of a receiver, researchers can pick up that signal. They can usually find a tree the bat is roosting in, said Self, but finding the actual bat is rare. 

“If we follow a bat all the way to a roost and find what we think is a good roost, that allows us to do some habitat surveys of those sites and figure out what’s different about this spot, why the bat is choosing this spot,” Self explained. 

Since 2015, the team has also used acoustic monitoring to study bats. The devices, which are placed throughout the park, pick up bat sounds. 

“Even though these devices are recording sounds, they’re not sounds we can hear,” Self noted, “so we have to run them through special software to help us understand what species was making the call.” 

He said the frequency level, as well as the shape of the call, helps them determine which bat species it is. 

Mist netting and acoustic recording have their limitations. According to Self, neither technique can give a full picture of the Effigy Mounds bat community—the number of bats or the species composition. They can, however, help those involved in the program compare activity and data over periods of time. 

In the past few years, the program has collected hundreds of thousands of bat call recordings. 

Hundreds of bats have been caught, including nearly 100 in 2015 and roughly 200 in 2016. At that time, Zuercher said 38 percent of the community was comprised of little brown bats. Northern long-eared bats made up 22 percent. But last year, everything changed. 

“We’ve documented a massive decline in the amount of small hibernating bat activity in the last two years,” Self said. 

Capture rates have declined from over 4.5 bats per net each night in 2016 to a little over 1.4 in 2017. 2018’s figures will be similar. 

“In 2017,” said Zuercher, “no more long-eared bats. We haven’t caught them since.” 

He and his students haven’t caught them at other netting sites either. Out of tens of thousands of calls, northern long-eared bats have accounted for less than 100. 

“They’re gone,” Zuercher stated, “and everyone in the bat community has basically said they’re going to go extinct, at least in this area.”

Little brown bats have been nearly as scarce. 

“There are colony collapses anywhere from 95 to 99 percent, in some cases 100 percent,” Zuercher said. 

This program, said Self, came just in the nick of time. 

“We have one year’s worth of data about what bats were active like before white-nose syndrome came,” he shared. 

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Moving forward, Self said Effigy Mounds will continue monitoring its bat population, especially through acoustic monitoring. Zuercher said there’s always hope the bats who make it through will be able to continue the species. 

“We’ve seen bats that obviously had been exposed to the fungus; they had wing lesions, some of them looked really terrible, but they were still flying and breeding,” Zuercher noted. “That’s going to be the key for these bats. Some individuals are going to have to make it through this infection, otherwise they’re all going to go away.” 

He said the bat community is now worried about the spread of white-nose to the western U.S., where there are considerably more species and more bats living in even larger colonies. Because bats are difficult to study, little is known about these bats. 

“A lot of work is being done to see if we can prevent it from coming in and decimating populations before scientists learn more about them,” he said. 

In the meantime, Zuercher encourages people to support bat conservation and research. 

“This is a big issue,” he said. “Things that we don’t think about are ecologically, and many cases economically, important. They need support, they need champions.”