11/12/2025
What do Cave Bats do in the Winter months?
Wisconsin is the home to 8 species of bats with the Big Brown Bat being the most common.
Here we have a Big Brown Bat that was discovered on the ground during these past cold days. All he needs is a little warmth and food and he can be on his way back to find his roost.
Let’s learn a little about these amazing little critters.
During winter bats go into a state called torpor. It’s not true hibernation because the warm temperatures can cause them to move around more to find water and readjust themselves, but they can spend weeks or months at a time in an inactive state by slowing down their metabolism to conserve energy. Cave bats roost in large groups in the winter because even though their body temperature drops significantly during torpor, their collective group body heat can help keep them all warm.
Bats look for a roosting place called a hibernaculum. It typically will have a consistent temperature range of between 35- and 40-degrees Fahrenheit. They may roost in caves, hence the name, but these spaces can often be too damp for them. Because buildings often provide consistent temperatures and low humidity, bats may make roosts inside barns, churches, and warehouses. Your home’s living space is probably too warm for bats, but the attic or garage may provide ideal conditions. Big brown bats are more tolerant of cold and dry conditions, so they sometimes don't hibernate until around December and when they do, they're more likely to hibernate in people's homes.
In the past decade, the hundreds of thousands of bats that live in Wisconsin have faced a scary situation: the rise of white-nose syndrome, a fungal disease that has devastating impacts on the bat population globally. Named for the powdery white fungal growth on infected bats' wings and muzzles, it was first found in Wisconsin in 2014 and has had a catastrophic impact on the state's bat population. But the numbers have looked more reassuring in recent years. Bats have been around for more than 50 million years, they’re very adaptable so there is some hope that their ability to adapt will help them with living with white-nose syndrome.
Now you know 😊
