Recently the customer service staff and I have been receiving a lot of calls about bats and how to exclude them from buildings. Like many folks, I have always thought bats were cool, as long as they stayed out of my living space. Like snakes, though, there are many people who have a complete hatred for bats without a valid reason. I can understand; it seems that bats have long been associated with evil and darkness (take Dracula, for example). However, bats are relatively harmless and can benefit people, consuming large amounts of insects like mosquitoes and moths.

As a biologist, watching bat developments has been fascinating the last couple of years. Because of a disease called White Nose Syndrome that was discovered in 2006, bats have been dying off in large numbers. While the disease has not been documented in Wisconsin to date, it has been documented in neighboring states, most recently northeast Illinois. Like many agencies and groups, the Wisconsin DNR began an intensive effort to survey, document and monitor bat populations since that time. Check out the Wisconsin Bat Monitoring Program website, wiatri.net/inventory/bats/, to learn about opportunities you might have to help with the bat survey effort.

In June 2011, Wisconsin’s cave bats were added to the state list of threatened mammals. This means killing bats is now illegal in most cases. People can still legally remove bats from human living spaces in their homes under certain circumstances. One big source of frustration for homeowners this year is an added measure of protection that makes it illegal to exclude bats from buildings between June 1 and Aug. 15. Bats are mammals and give live birth to young (pups) that need to nurse until they are old enough to begin hunting for food. These pups are left behind in nurseries while adults go out foraging, and if the mothers are excluded, the pups will certainly starve to death in the building. According to Heather Kaarakka, DNR bat roost coordinator, there are a rare few exceptions that may be granted for exclusion during this time, specifically for roosts that are in hospitals, schools, daycare centers and other public buildings in which the bats roosting (and their droppings) may cause health issues.

Once we get past Aug. 15, there are exclusion methods that will let the bats leave the building, but not let them return. These are available on the DNR website (log on to dnr.wi.gov, and search “bat exclusion guide”) or, if you don’t surf the web, stop in at your local DNR Service Center and ask the customer service staff to print you off a copy. I am truly impressed by the bat information available on the DNR website; they have everything from life history information on Wisconsin’s eight bat species to information on how to build a bat house, which gives bats an alternative roost site once legally excluded from your buildings. If you have any questions about bats, I have co-workers like Paul and Heather who are experts; you can email them at dnrbats@wisconsin.gov or call the bat hotline at (608) 266-5216.

Our long, cold, late spring was tough on bats coming out of hibernation. If our current weather trend continues, though, we should see good survival of bats and young. I thought that bats roosting under siding might move out as the weather warms up, but I was wrong. Paul White, an ecological inventory and monitoring conservation biologist with the DNR in Madison, says bats like it hot, over 110 degrees Fahrenheit, to keep their young warm and help them grow quickly. So, if you have multiple bats using your attic, boathouse or siding right now, you likely have a roosting colony of female bats and their young. This means you are performing a vital ecological service, running a bat daycare of sorts, and the lives of little baby animals hang in the balance.

Jeremy Holtz is a wildlife biologist with the Wisconsin DNR and writes a weekly column in the Star Journal. To contact him, call (715) 365-8999.