Conservation, research encouraged during Bat Week
By Audrey Posten | Times-Register
Oct. 24-31 is International Bat Week, a global celebration of bats and their ecological importance. One area organization marking the occasion is Effigy Mounds National Monument, which has been tracking bat populations in the park through habitat surveys, mist netting, radio telemetry and acoustic monitoring since 2014.
Jeanette Muller, a long-time seasonal bio tech, spoke about the efforts—and the benefits of bats—during a presentation earlier this month.
There are over 1,400 species of bats worldwide, making up one-fourth of the earth’s mammals.
“Everything from the giant flying foxes in the tropics and Australia to our tiny little bats here that might weigh like half an ounce or less. Imagine five or six paper clips,” Muller said. “They’re super diverse. They live everywhere but in super high elevation and Antarctica. The colder you get, the fewer bat species. Ours have to hibernate during cold weather or migrate.”
Seven bat species have been documented at Effigy Mounds: big brown bat, little brown bat, Northern long-eared bat, tri-colored or Eastern pipistrelle bat, Eastern red bat, hoary bat and silver-haired bat.
Bats have numerous benefits, most notably pest control.
“Our smallest bats eat a huge amount of mosquitoes. Some bats can eat half their body weight in a night. Some, even more,” Muller shared.
The U.S. alone, she noted, saves trillions of dollars in crop losses and pesticides thanks to bats. And a number of foods are pollinated by bats, or the animals help spread seeds.
Muller set up a table showcasing some of the foods that benefit from bats and listed others. This includes rice, chocolate, macadamia nuts, bananas, peaches, cloves, agave, dates, figs, coffee, cashews and more.
“Bat pollination can help over 500 species of plants. That’s pretty good,” Muller said.
Additionally, bat guano is a good fertilizer, enriching soil with minerals and providing drainage and texture. It can provide a natural fungicide in the soil and its microbes are reported to help clean up toxic soils.
Bats can serve as sources of tourism in some areas, and they’ve aided medical research and engineering.
Unfortunately, said Muller, bats are under threat due to habit loss where they roost and hunt, as well as overuse of pesticides and even overharvesting for meat. They’re also hindered by a poor public image.
“A lot of people are scared of them,” Muller said. “But less than half a percent of bats get rabies. Generally, they aren’t going to bite you unless you’re handling them or messing with them.”
Perhaps the most dangerous threat, though, is white-nose syndrome, a disease that has killed an estimated 6.7 million bats in North America since 2006, according to the Center for Biological Diversity. White-nose was first seen in New York state in 2006, and quickly spread across the continent. The fungus originally came from Eurasia and can be transmitted by bats as well as humans traveling back and forth.
“It affects more than just their noses, but that’s one of the places you see it,” said Muller, “and it doesn’t mind the cold, which is really bad for our bats hibernating in caves. It will break them down. It gets on their wings, into their skin.”
The disease can dehydrate bats and sap their energy, often waking them during hibernation. Many starve in caves, or brave the elements in search of insects.
“But there isn’t anything,” Muller said.
It was during white-nose’s progression across North America that Effigy Mounds pushed for the first detailed survey of bats in the park.
“If we have threatened or endangered species, we have to consider them in any tasks or projects. If we get a baseline study, we can see what changes are occurring in these species,” Muller explained. “We were starting it with the idea of seeing if the Indiana bat, which was listed at the time, was here.”
Starting in 2014-2015, in cooperation with a University of Dubuque professor and some of his students, intensive mist netting began.
Mist nets are nets attached to two tall poles, which catch bats as they fly at night. Because of the park’s terrain, nets were set up in avenues between groups of trees that might be natural flyways.
Once caught, bats must be treated delicately.
“You have to work carefully to untangle them. We’re wearing leather gloves with exam gloves over the top that we’re changing every time you handle a different bat,” Muller shared.
Staff and students would take measurements of different parts of the bat—body and wing length, weight.
“Weight is important because, when we were doing radio tracking of female northern long eared bats, they had to weigh at least eight grams for you to stick the radio transmitter on them,” Muller said.
Around the same time, acoustic monitoring was happening throughout Effigy Mounds. According to Muller, the 2,500-acre park was divided into roughly 60 squares. Researchers would select a random location and stick a monitor on a tree. The monitor would remain three days and the information downloaded before it was moved to a new spot.
“Part of the reason you’re doing it is you’re not having to handle bats and there are species that are very hard to catch in mist nets. You’re able to detect some bats that mist nets aren’t likely to get,” Muller said. “You’re also looking at patterns—nights and seasonal, like what months are you hearing the bats. Bats have different ranges with their acoustics. Pretty much everything the bats are doing is above human hearing, so the microphone is picking that up and then it’s getting washed through a computer program.”
In 2016, radio telemetry was being used to track bats captured at night to their day roosts. Bats at Effigy Mounds, said Muller, were often roosting in trees, around buildings or in crevices of rocks.
“A lot of our bats preferred dead trees. They’ll use hollows from woodpeckers and sometimes they’ll hang out under the bark,” she detailed.
The first two years, “we caught a little bit of everything,” said Muller. There were 92 total in 2015, though no Indiana or evening bats, despite them being geographically close.
By 2016 and 2017, several years of white-nose had caused populations to fall drastically.
“We saw that with our capture rate. Our smaller bats were taking it very badly. They just weren’t there anymore,” Muller said.
By 2019, the bats had crashed so much that staff were no longer mist netting. They did, however, set up acoustic monitors at several select sites on park cliffs, to see if bats were hanging out on cliffsides.
“In the last few years,” said Muller, “we haven’t been able to do any data crunching, but we still have five ‘permanent’ sites and several cliff sites. We’re still looking at questions. Can our feisty friends recover? We’re not sure.”
How can people help? She urges others to promote bat research and conservation. Bat Conservation International offers resources and information about Bat Week on its website, batcon.org.
Muller said Effigy Mounds will continue to raise awareness and study area populations.
“We want to do some continued study and look at our acoustics because the ecological impact of losing bats is pretty major,” she stated.