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The Northwoods River News | Rhinelander, Wisconsin

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July 20, 2019

5/25/2019 7:30:00 AM
Natural Reaction
Listening to the language of bats
Jacob Friede
Of The Lakeland Times

Unlike the slow grandeur of the sunsets they scatter through, bats are a fleeting beauty. They're the first glimpse of night as they dart across the dusk and disappear into nocturnal mystery. Their dazzling flight, quick as the fading light, allows no time for close observation. Bats are a challenging treat to the eye which unfortunately is becoming more and more rare.

Plain and simple, hibernating bats are in trouble. They are dying by the millions and white nose syndrome is the culprit. It is caused by a fungus which grows in the caves where bats hibernate. The fungus, once contacted, irritates the bats to the extent that they wake from hibernation in winter and go out seeking food which is not there, and while doing so they burn all their food storage and drop dead of starvation.

It began on the East Coast 12 years ago and in that time it has spread across the country. That's why it's more important than ever to know where surviving bats are, so they can be monitored and the extent of the damage of white nose syndrome can be better understood.

That's where the Wisconsin Bat Monitoring Project comes in. The project is a network of citizen scientists that survey locations for bat populations all across the state. On Monday night at the North Lakeland Discovery Center, naturalist Licia Johnson taught an acoustic bat monitoring course to introduce new participants to the project.

"This program came about because there was such a need to learn more about the bats in Wisconsin and this really came about when white nose syndrome hit the East Coast in the winter of 2006-2007," Johnson explained. "They lost millions of bats in one year and they hadn't really researched. They didn't know how many bats they had, where the species were distributed around the area at different times of the year, and so we saw that what was happening is they were scrambling because all these bats were just dead. And so we really kicked it up after that, to get people out surveying their lakes, surveying their areas to find out what bats we have, where are they at different times of the season, turning to citizens to help with that information."

In order to help keep an eye, or ear, on Wisconsin's bat population, participants in the course were instructed on how to conduct bat surveys using an extremely sensitive microphone, called a bat detector, that picks up the acoustic frequencies of bats and divides them so they can be heard by humans.

A survey is done by simply holding the bat detector while moving slowly by boat along a shoreline or walking in an open space after dusk. The detector picks up the vocal waves bats send out to echo off insects. An approaching bat gives a "tick-tack" sound that increases with frequency the closer a bat gets. The sound waves are instantly recorded onto a portable data computer connected to the detector. The data computer is also connected to a GPS so the precise location of the bat detection is documented.

DNR scientists who study the collected sound waves can make a determination as to which species of bats were present based on frequency. There are eight different species in Wisconsin.

The GPS allows for a map of the survey route to be developed. Through repeated surveys of a route, populations at different times of the year can be compared, and therefore an increase or decrease in bat numbers can be determined at a specific time and location.

Johnson showed a sample survey map from Wisconsin in 2013 of one lake which was completely marked along the entire shoreline with bat detections. Four years later the map had only two detection marks on the whole lake.

That was just one example, on one lake, of a disturbing trend caused by white nose syndrome.

The threat to bats has serious implications to the ecosystems they inhabit. Johnson explained bats are some of the world's most important pollinators, as well as agents of pest control. She said they save the agricultural industry in Wisconsin $658 million which would otherwise be spent on pesticides.

Bats are also some of the world's most efficient planters, dispersing seeds in their nitrogen rich droppings called guano.

But for all their benefits and beauty, Johnson said the nature of bats remains a mystery, and that can present challenges when trying to understand and help them.

"Basic lack of information on the ecology and the trends is one of the greatest limitations to conserving bats," she said. "They're small, they're dark, they come out at night, they don't make a sound we can hear. You really can't get much information from that."

Thankfully, with the proper technology in hand, bats can now be heard, and at the very least the bats are simply saying that they are there, which is significant because at this point there is no greater find concerning bats than finding one in the first place.

Jacob Friede may be reached at or

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