The Ridges Sanctuary

Preservation, Education, and Research

Nature Notes: Wisconsin’s Bats

Posted on Sep 29, 2022 by Jeanne Farrell   No Comments Yet | Posted in Blog · In the News · Nature Notes · Uncategorized

By Anna Foster  

Little brown bats in a bat house. © Heather Kaarakka, Wisconsin DNR.

As a child, I vividly remember spending summer evenings at Welcker’s Point in Peninsula State Park, waiting patiently for the sun to go down. Children would gather about ten feet from the large bat nursery, hung on the side of the old shelter, with parents gathered behind them. As the sun grew closer and closer to the horizon, we would begin to hear the squeaks of bats waking up from their daily slumber. Slowly, then in a rush, they would emerge, darting out faster than anyone could count. Sometimes they were so fast we couldn’t even see them. We would only feel the rush of wind as they flew inches above our heads and into the forest beyond us. Hundreds of bats would emerge in the span of twenty minutes, off to eat the swarms of mosquitoes at campsites throughout the park.  

Now, about 20 years later, most of the bats are gone. Crowds no longer gather at sunset to experience the magic of the bats emerging from their box. Instead, a sign hangs under the bat nursery that educates visitors on White Nose Syndrome, the devastating disease that has killed over 90% of Wisconsin’s bats.  

Bats are one of the most misunderstood yet ecologically beneficial creatures in the world. They help pollinate plants, control insect populations, and are an important indicator species for many ecosystems. Bats are known to eat fruit, pollen, insects, invertebrates, frogs, and in some species, blood. However, bats of Wisconsin primarily eat insects.  

A bat researcher climbs through Horseshoe Bay Cave to monitor the bat population there. Courtesy of Wisconsin DNR.

There are four species of cave bats in Wisconsin, which live in caves and hibernate there throughout the cold winters: the Big brown bat, the Little brown bat, the Northern long-eared bat, and the Eastern pipistrelle. In addition, there are four species of tree bats, which migrate south to warmer weather in the winter: the Silver-haired bat, the Hoary bat, the Eastern red bat, and the Evening bat.  

Bats have very poor eyesight, relying instead on echolocation to navigate. Echolocation describes a process where an animal emits calls at a certain frequency and those calls bounce off of objects around them and back to the animal. Using the echoes of their call, they create a sound map to navigate the world around them and find prey. Bats’ echolocation is incredibly sophisticated and accurate. When echolocating, they can detect an object the size of a single human hair.  

Bats have many natural predators, including owls, snakes, hawks, raccoons, and even cats. However, in recent years, disease has been the primary cause of population decline. White Nose Syndrome (WNS) has caused the decline of cave bats in Door County by over 95%. In Horseshoe Bay cave, just south of Egg Harbor, the bat populations fell from over 1,000 in 2015 to 24 in 2019. WNS is a fungal disease that causes bats to wake up during their hibernation, causing the bat to use up its energy reserves. In some cave sights in North America, it has killed between 90 and 100% of the cave bat populations. 

Although WNS has decimated the cave bat populations in Door County, there is hope. In 2022, the bat population in Horseshoe Bay Cave was up to 44 bats. That’s almost double what it was in previous years. Some populations are showing a stabilization after years of rapid decline caused by the disease. Scientists are also studying vaccines for bats to prevent the spread of WNS. This could take years to fully develop and implement, but there could be a light at the end of the tunnel for Wisconsin bats (pun intended).  

On Friday, October 14th, we are hosting a program called Get to Know Wisconsin’s Bats. Jennifer Redell, Wisconsin Bat Biologist from the Wisconsin DNR, will be joining us to talk about Wisconsin Bats and White Nose Syndrome. After the presentation, there is a Bat House Building Workshop, in which you will be provided with materials for a bat house, instructions on how to put it together, and tips for installation on your property. Be sure to join us for this bat-tastic event! More details below:  

Get to Know Wisconsin’s Bats Presentation 

October 14 @ 2:00 pm – 3:00 pm 

Meets at Cook Fuller Nature Center
$8 Public, $5 Members, Under 12 Free 

PRE REGISTRATION IS REQUIRED | Capacity: 25 participants 

Click here to register! 

Bat House Building Workshop 

October 14 @ 3:00 pm – 4:30 pm 

Meets at Cook Fuller Nature Center 

$30 Public, $25 Member 

PRE REGISTRATION IS REQUIRED | Capacity: 14 bat boxes available (more than one individual can build a box) 

Click here to register! 

 Blog Sources:,of%20objects%20in%20its%20environment. 

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