Beginning in September 2024, I began collaborating with John Paul White, a mammal ecologist, at the Wisconsin Department of Natural Resources (WDNR) as a volunteer collecting survey data on silver haired bats migrating through Milwaukee, Wisconsin. Silver haired bats begin their southward migration in the autumn to milder climates for hibernation. While it is known that silver haired bats prefer old growth forests or caves, in Milwaukee they can be spotted roosting on the surfaces of buildings or other structures during their migratory journey. An increase in the quantity of silver haired bats was noticed in the Milwaukee area last year, in 2023, during their autumn migration. Therefore, this is a developing study, kicked off in the autumn of 2024 (this year), on the migratory pathway and populations of silver haired bats in the Milwaukee area.

These bats are a species of special concern in the state of Wisconsin meaning that they are known or expected to be rare. For species with this designation, it is important to have quality population data to understand population shifts over time.

Thus far, my observations include that the bats prefer to roost on surfaces which retain heat such as the red brick buildings of Milwaukee or even concrete structures such as light posts or statues. I have also observed the bats roosting in locations which protect themselves from Milwaukee’s windy autumn days. The bats have thus far all been roosting in solitary states meaning that I have not found bats roosting in close proximity to one another. Some of the observed bats have roosted in the same location for several weeks at a time.

I am curious to see how long the bats will continue to be found in Milwaukee and excited to see what conclusions can be drawn from our developing dataset.